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  • 1995-1999  (1,275)
  • 1985-1989
  • 1997  (1,275)
  • Theoretical, Physical and Computational Chemistry  (699)
  • Chemical Engineering  (418)
  • Genetics  (158)
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Years
  • 1995-1999  (1,275)
  • 1985-1989
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Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Preliminary report on the Mount Sinai Hospital Inflammatory Bowel Disease Genetics Project (1997)
    Springer
    Diseases of the colon & rectum 40 (1997), S. 553-557 
    Details
    ISSN: 1530-0358
    Keywords: Inflammatory bowel disease ; Crohn's disease ; Ulcerative colitis ; Genetics ; Family history
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract BACKGROUND: Although the etiology of inflammatory bowel disease (IBD) is unknown, there is increasing evidence that genetic predisposition plays a major etiologic role. To provide the framework for gene identification using a positional cloning approach, ascertainment of families with multiple affected members and careful documentation of pedigrees are essential. Objective: To report the initial findings of the IBD Genetics Project of the Mount Sinai Hospital IBD Research Unit. METHODS: All records of patients with ulcerative colitis and Crohn's disease followed at the Mount Sinai Hospital IBD Unit were reviewed. A questionnaire was sent to all patients to ascertain those with a family history of IBD. Patients with a presumed family history were contacted by a research assistant, and after confirmation of diagnosis, relevant clinical information, pedigrees, and consent to contact family members were obtained. Blood for DNA and cell line preparation were collected from affected and nonaffected family members. RESULTS: Of 2,504 patients registered in the IBD database, 231 (9.2 percent) were found to have an affected family member: 96 of 964 (10 percent) with Crohn's disease (CD) and 135 of 1,540 (8.8 percent) with ulcerative colitis (UC). A mean of 2.4 family members were affected. In families in which the proband had CD, 82.3 percent had only two affected family members, 78.1 percent had only family members affected with CD, and 82.3 percent had only first-degree family members affected. In families in which the proband had UC, 70.4 percent had only two affected family members, 71.1 percent had only family members affected with UC, and 65.2 percent had only first-degree family members affected. In the 231 families, there were 103 sibling pairs: 46 percent with CD, 28 percent with UC, and 26 percent with CD/UC. CONCLUSION: These data suggest that approximately 10 percent of IBD patients have affected family members, with the rate being similar in UC and CD. Future research is directed to genome scanning and linkage analysis in this cohort of patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02055377
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  • 2
    Electronic Resource
    Electronic Resource
    Genetic control of Interleukin 12 responsiveness: implications for disease pathogenesis (1997)
    Springer
    Journal of molecular medicine 75 (1997), S. 502-511 
    Details
    ISSN: 1432-1440
    Keywords: Key words T helper 1/T helper 2 ; Genetics ; Interleukin 12 ; Allergy ; Autoimmunity ; Leishmania
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We examined the effect of genetic background on Th1/Th2 development. We discuss data demonstrating that genetic background is an important determinant of interleukin-12 (IL-12) responsiveness and the potential implications for disease progression in murine experimental leishmaniasis. Genetic analysis of the differential control of IL-12 responsiveness led to the identification of a controlling locus on the middle portion of murine chromosome 11. This genetic region (or its human counterpart, 5q31) has been associated with increased disease susceptibilities for several atopic, infectious, and autoimmune disorders. We discuss potential roles for genetic control of IL-12 responsiveness in the development of these diseases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001090050135
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  • 3
    Electronic Resource
    Electronic Resource
    Familial Hodgkin's disease: a disease of young adulthood? (1997)
    Springer
    Annals of hematology 74 (1997), S. 131-134 
    Details
    ISSN: 1432-0584
    Keywords: Key words Hodgkin's disease ; Sex ; Age ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Familial Hodgkin's disease (FHD) is estimated to represent approximately 4.5% of all cases of Hodgkin's disease (HD). Shared environmental factors, such as Epstein-Barr virus and other viral agents, and genetic determinants have all been proposed to explain familial aggregation of HD. In order to compare the characteristic features of FHD with those of the much more common sporadic form, we reviewed 28 articles on FHD, published between 1972 and 1995, and analyzed in further detail data from 18 papers, reporting on a total of 328 patients. The male-to-female ratio of the FHD population examined was 1.5, similar to that reported for sporadic HD, and lower than the one suggested for FHD by some authors. On the other hand, a significant difference was found between sporadic and familial HD according to age at diagnosis; that is, only one major peak between 15 and 34 years was present in the group of patients with FHD. Further investigation of FHD in young adulthood may provide insight into the hypothesis of a genetic or infectious etiology of the disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002770050270
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  • 4
    Electronic Resource
    Electronic Resource
    Genetics and cytology of a new genic male-sterile soybean [Glycine max (L.) Merr.] (1997)
    Springer
    Sexual plant reproduction 10 (1997), S. 13-21 
    Details
    ISSN: 1432-2145
    Keywords: Key words Soybean ; Male sterility ; Genetics ; Callase ; Callose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Genetic and cytological studies were conducted with a new male-sterile, female-fertile soybean [Glycine max (L.) Merr.] mutant. This mutant was completely male sterile and was inherited as a single-recessive gene. No differences in female or male gamete transmission of the recessive allele were observed between reciprocal cross-pollinations in the F1 or F2 generations. This mutant was not allelic to any previously identified soybean genic male-sterile mutants: ms1, ms2, ms3, ms4, ms5, or ms6. No linkage was detected between sterility and flower color (W1 locus), or between sterility and pubescence color (T1 locus). Light microscopic and cytological observations of microsporogenesis in fertile and sterile anthers were conducted. The structure of microspore mother cells (MMC) in male-sterile plants was identical to the MMCs in male-fertile plants. Enzyme extraction analyses showed that there was no callase activity in male-sterile anthers, and this suggests that sterility was caused by retention of the callose walls, which normally are degraded around tetrads at the late tetrad stage. The tapetum from male-sterile anthers also showed abnormalities at the tetrad stage and later stages, which were expressed by an unusual formation of vacuoles, and by accumulation of densely staining material. At maturity, anthers from sterile plants were devoid of pollen grains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050062
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of naltrexone on subjective alcohol response in subjects at high and low risk for future alcohol dependence (1997)
    Springer
    Psychopharmacology 129 (1997), S. 15-22 
    Details
    ISSN: 1432-2072
    Keywords: Key words Naltrexone ; Alcohol ; Genetics ; Social drinkers ; Family history of alcoholism ; Biphasic Alcohol Effects Scale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We investigated specific subjective effects of naltrexone pretreatment or placebo during various intervals on the breath alcohol level (BAL) curve in nonalcoholic volunteers. Fifteen high-risk (social drinkers with an alcoholic father) and 14 low-risk (no alcoholic relatives in at least two generations) subjects were tested in a double-blind, placebo-controlled study of the effects of 50 mg oral naltrexone on response to a moderate dose of alcohol. Dependent measures included subjective stimulation and sedation subscales from the Biphasic Alcohol Effects Scale (BAES) and mood subscales from the Profile of Mood States (POMS). At rising BALs, high-risk subjects showed a naltrexone-related attenuation of BAES stimulation. This effect was not evident in low-risk subjects, who directionally showed the opposite effect, although nonsignificant. For both groups, there were no significant naltrexone-related effects for BAES sedation; however, naltrexone did affect several POMS scales on alcohol response, such as decreased vigor, and increased fatigue, tension, and confusion. Confusion was significantly elevated for the high-risk group during rising BALs of the naltrexone session. The results suggest a differential response to naltrexone, based on paternal history of alcoholism and level of stimulation experienced during alcohol drinking.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050156
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  • 6
    Electronic Resource
    Electronic Resource
    Mitochondrial DNA polymorphisms in pathologically proven Parkinson’s disease (1997)
    Springer
    Journal of neurology 244 (1997), S. 262-265 
    Details
    ISSN: 1432-1459
    Keywords: Key words Parkinson’s disease ; Genetics ; Mitochondrial DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To date, five single base pair changes of the mitochondrial DNA have been reported to occur either exclusively or with increased frequency in Caucasian patients with Parkinson’s disease (PD) and it has been postulated that these mutations might be causally related to the observed inhibition of mitochondrial respiratory chain function in PD. To evaluate these findings, we analysed the frequency of all five polymorphisms in 100 cases of pathologically proven cases of PD. We were either unable to detect the previously described polymorphisms in our series or found them to be present with the same frequency among controls. Our data do not support the hypothesis of an involvement of the mitochondrial DNA in the pathogenesis of PD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050082
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  • 7
    Electronic Resource
    Electronic Resource
    Genetics, haloperidol-induced catalepsy and haloperidol-induced changes in acoustic startle and prepulse inhibition (1997)
    Springer
    Psychopharmacology 134 (1997), S. 131-139 
    Details
    ISSN: 1432-2072
    Keywords: Key words Startle ; Prepulse inhibition ; Inbred strains ; Haloperidol ; Catalepsy ; Schizophrenia ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The acoustic startle response (ASR), prepulse inhibition (PPI) of the ASR and the effects of haloperidol on the ASR and PPI were examined in C57BL/6J (B6) and DBA/2 (D2) inbred mouse strains and their F1 and F2 progeny. The startle stimulus was a 60-ms, 110-dB, 10-kHz tone; the prepulse stimuli were 20-ms white noise bursts at 56, 68 and 80 dB against a 50-dB background presented 100-ms before the startle pulse. The B6 strain showed modest PPI (25–40%); in contrast, the D2 strain showed on average no PPI and numerous individuals showed prepulse augmentation (PPA). The F2 progeny showed an intermediate PPI; however, the extreme values ranged from 200% PPA to essentially 100% PPI. Haloperidol in dose-dependent fashion, increased PPI in both the B6 and D2 strains; the threshold dose was in the range of 0.1–0.2 mg/kg. Raclopride (0.3 mg/kg), clozapine (2 mg/kg) and risperidone (0.4 mg/kg) also increased PPI in both strains. The effects of haloperidol (0.4 mg/kg) on PPI in 140 F2 progeny were examined. For all prepulse intensities, there were highly significant (r 〉 0.80) and negative correlations between baseline PPI and the haloperidol-induced change in PPI. Thus, those animals that showed the greatest PPA showed the greatest haloperidol-induced increase in PPI. There was, however, significant variance in the haloperidol response; plots of the regression residuals showed the most and least responsive animals differed by almost 100% in effect on PPI. The F2 progeny were subsequently phenotyped for haloperidol-induced catalepsy. There was no association between the variation in effects on catalepsy and PPI. However, it was observed that those individuals with the poorest baseline PPI were catalepsy non-responsive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050434
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  • 8
    Electronic Resource
    Electronic Resource
    Behavioral phenotypes of inbred mouse strains: implications and recommendations for molecular studies (1997)
    Springer
    Psychopharmacology 132 (1997), S. 107-124 
    Details
    ISSN: 1432-2072
    Keywords: Key words Mouse ; Inbred strains ; Behavior ; Genetics ; Locomotion ; Open field activity ; Learning ; Memory ; Aggression ; Parental behaviors ; Acoustic startle ; Prepulse inhibition ; Alcohol ; Nicotine ; Cocaine ; Opiates ; Haloperidol ; Diazepam ; Breeding ; Embryonic stem cell lines ; Transgenic ; Knockouts ; Null mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Choosing the best genetic strains of mice for developing a new knockout or transgenic mouse requires extensive knowledge of the endogenous traits of inbred strains. Background genes from the parental strains may interact with the mutated gene, in a manner which could severely compromise the interpretation of the mutant phenotype. The present overview summarizes the literature on a wide variety of behavioral traits for the 129, C57BL/6, DBA/2, and many other inbred strains of mice. Strain distributions are described for open field activity, learning and memory tasks, aggression, sexual and parental behaviors, acoustic startle and prepulse inhibition, and the behavioral actions of ethanol, nicotine, cocaine, opiates, antipsychotics, and anxiolytics. Using the referenced information, molecular geneticists can choose optimal parental strains of mice, and perhaps develop new embryonic stem cell progenitors, for new knockouts and transgenics to investigate gene function, and to serve as animal models in the development of novel therapeutics for human genetic diseases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050327
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  • 9
    Electronic Resource
    Electronic Resource
    The effects of cocaine on operant responding for food in several strains of mice (1997)
    Springer
    Psychopharmacology 132 (1997), S. 202-208 
    Details
    ISSN: 1432-2072
    Keywords: Key words Cocaine ; Operant behavior ; Genetics ; Mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The availability of numerous genetically homogenous mouse strains permits the analysis of genetic influences on behavior and also behavioral sensitivity (responsivity) to drugs of abuse. The current study was conducted to characterize discriminated operant responding for food in four inbred strains (Balb/cByJ, DBA/2J, C57BL/6J, SJL/J), an F1 Hybrid (C57BL/6×SJL), and one outbred strain (CD1) of mouse. The effect of cocaine on this operant behavior was also examined. Initially, all animals were trained to nosepoke for food on a continuous reinforcement schedule. The minimum response requirement for reinforcement was increased every 5 days until the animals were responding on an FR-15 schedule of reinforcement. All strains increased operant responding as the schedule of reinforcement was raised. However, significant differences in response rate and discrimination learning were observed among the various strains of mice. Cocaine administration reduced operant responding for food in Balb/cByJ, C57BL/6J, C57BL/6×SJL/J and CD1 mice at a dose of 15.0 mg/kg, whereas higher doses were required in DBA/2J mice (30.0 mg/kg) and SJL/J mice (56.0 mg/kg). These results suggest that operant performance and the effect of cocaine on this behavior is differentially influenced by genetic make-up.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050337
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  • 10
    Electronic Resource
    Electronic Resource
    Homoclinic chaos in a model of natural selection (1997)
    Springer
    Journal of mathematical biology 35 (1997), S. 294-320 
    Details
    ISSN: 1432-1416
    Keywords: Key words: Natural selection ; Homoclinic chaos ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract.  We modify a simple mathematical model for natural selection originally formulated by Robert M. May in 1983 by permitting one homozygote to have a larger selective advantage when rare than the other, and show that the new model exhibits dynamical chaos. We determine an open region of parameter space associated with homoclinic points, and prove that there are infinite sequences of period-doubling bifurcations along selected paths through parameter space. We also discuss the possibility of chaos arising from imbalance in the homozygote fitnesses in more realistic biological situations, beyond the constraints of the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002850050053
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  • 11
    Electronic Resource
    Electronic Resource
    Expression of a unique plastid-localized heat-shock protein is genetically linked to acquired thermotolerance in wheat (1997)
    Springer
    Theoretical and applied genetics 95 (1997), S. 834-841 
    Details
    ISSN: 1432-2242
    Keywords: Key words Stress proteins ; Heat tolerance ; Chloroplast ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We have used a combination of molecular and classical genetic approaches to delineate the relationship between a specific HSP member and cell viability under heat stress. Using recombinant inbred lines (RILs) of wheat, derived from a cross of the thermotolerant cultivar ‘Mustang’ and the thermosusceptible cultivar ‘Sturdy,’ we have identified a unique HSP and a differentially expressed cDNA sequence, both related to the plastid-localized HSP26 gene family, that are closely associated with acquired thermotolerance in wheat. An isoform of HSP26 was synthesized under heat stress in all examined thermotolerant RILs and ‘Mustang’, and was absent in all examined thermosusceptible RILs and ‘Sturdy.’ Using a modified differential-display method, we have also identified a gene-specific cDNA sequence that is similar to other known members of the wheat HSP26 gene family and is selectively expressed in ‘Mustang’ and most of the examined thermotolerant RILs, but not expressed in ‘Sturdy’ and all the thermosusceptible RILs. These results suggest a genetic linkage between the acquired thermotolerance trait and the differential expression of a unique member of the HSP26 gene family.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050633
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  • 12
    Electronic Resource
    Electronic Resource
    Extreme resistance to potato virus V in clones of Solanum tuberosum that are also resistant to potato viruses Y and A: evidence for a locus conferring broad-spectrum potyvirus resistance (1997)
    Springer
    Theoretical and applied genetics 95 (1997), S. 1258-1262 
    Details
    ISSN: 1432-2242
    Keywords: Key words Extreme virus resistance ; Potyviruses ; Genetics ; Genes Rysto and Ra ; Broad-spectrum resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Extreme resistance to the potato V potyvirus (PVV) was found in four potato cultivars that contain Ry genes from Solanum stoloniferum. When plants of these cultivars, were inoculated by grafting in shoot tips from PVV-infected tomato plants, necrotic symptoms developed in some cultivars, although a full hypersensitive reaction was not elicited, while other cultivars were symptomless. PVV replication was not detected in any of the inoculated plants by ELISA, an infectivity assay of leaf extracts by manual inoculation to Nicotiana benthamiana indicator plants, or by ‘return grafting’ of shoot tips taken from newly developed shoots of the potato plants to virus-free indicator plants of tomato. These methods readily detected PVV infection in inoculated plants of cv ‘Flourball’, which does not contain an Ry gene and is susceptible, and in cvs ‘Maris Piper’ and ‘Dr Macintosh’, which contain gene Nv conditioning a hypersensitive reaction to inoculation. One of the Ry-containing cultivars, ‘Barbara’, has been previously shown to contain two genes that control extreme resistance, defined as no viral replication in intact plants, to the potyviruses potato viruses Y and A (PVY and PVA). These genes are: Ry sto , which conditions resistance to PVY and PVA, and gene Ra, which conditions resistance to PVA only. It was found that in genotypes from a progeny of the cross ‘Barbara’ (Ry sto /Ra)בFlourball’ (ry/ra), extreme resistance to PVV segregated with gene Ry sto . It is proposed that either gene Ry sto conditions broad-spectrum extreme resistance to the distinct potyviruses PVY, PVA, and PVV or that Ry sto represents a family of genetically closely linked genes each controlling resistance to a specific virus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050690
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  • 13
    Electronic Resource
    Electronic Resource
    Resistance to Phytophthora fragariae var. fragariae in strawberry: the Rpf2 gene (1997)
    Springer
    Theoretical and applied genetics 94 (1997), S. 1092-1096 
    Details
    ISSN: 1432-2242
    Keywords: Key words Fragaria×ananassa ; Genetics ; Inheritance ; Red core ; Red stele
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract   Phytophthora fragariae var. fragariae is the causal agent of red stele (red core) root rot in strawberry (Fragaria spp.). The inheritance of resistance to one isolate of this fungus was studied in 12 segregating populations of F.×ananassa derived from crosses between four resistant cultivars (‘Climax’, ‘Redgauntlet’, ‘Siletz’, and ‘Sparkle’) and three susceptible cultivars (‘Blakemore’, ‘Glasa’, and ‘Senga’ Sengana’). The analysis clearly supports the hypothesis of a single segregating dominant resistance gene. It is proposed that this gene be designated Rpf2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050520
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  • 14
    Electronic Resource
    Electronic Resource
    Genetic aspects of childhood behavioral disorders (1997)
    Springer
    Child psychiatry & human development 27 (1997), S. 139-150 
    Details
    ISSN: 1573-3327
    Keywords: ADHD ; Tourette Syndrome ; Genetics ; Gene Selection ; Conduct Disorder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The evidence is reviewed to support the concept that many disruptive, childhood and adolescent behavioral disorders including ADHD, Tourette syndrome, learning disabilities, substance abuse, oppositional defiant disorder and conduct disorder, are part of a spectrum of inter-related behaviors that have a strong genetic component, are polygenically inherited, share a number of genes in common that affect dopamine, serotonin and other neurotransmitters, and are transmitted from both parents. Some of the implications of this hypothesis in relation to diagnosis and treatment are reviewed, including the possibility that the genes involved may be increasing in frequency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02353694
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  • 15
    Electronic Resource
    Electronic Resource
    Computerized EEG topography of normal preadolescent twins—Correlating similarity of background activity with genetic relatedness (1997)
    Springer
    Brain topography 9 (1997), S. 303-311 
    Details
    ISSN: 1573-6792
    Keywords: EEG normality ; Brain topography ; Twins ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The influence of genetic relatedness on the similarity degree of topographical EEG parameters was studied in a sample of 26 sets of monozygotic (MZ) and 46 sets of dizygotic (DZ) twins. All 144 subjects were healthy, primary school children, aged 7–15 years, 69 boys and 75 girls. Correlation coefficients were calculated for 50 quantitative EEG parameters of paired values obtained at each of 16 active electrode sites, in four groups of paired tracings: 1. MZ twins, 2. DZ twins, 3. The autocorrelated (A) group formed by correlating the spectral parameters from the same subjects in two different analyzed sequences, 4. The random (R) control group of 1200 unrelated pairs formed from DZ twin pairs. Sets of MZ twins and A group showed the highest degrees of similarity of spectral parameters over all brain areas except for significant differences only for some background features over posterior regions. In contrast, highly significant differences in topographic parameters were evident in comparison of MZ sets with DZ sets, particularly when MZ sets were compared with DZ subsets of opposite sex. Both number and degree of significant differences increased progressively in comparisons with groups 3 vs 2,1 vs 4, and 3 vs 4. The data gave strong evidence for a complex polygenic determination of normal human EEG topography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01464485
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  • 16
    Electronic Resource
    Electronic Resource
    Simulations of a LDPE reactor using computational fluid dynamics (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 104-117 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Computational fluid dynamics methods are used to provide three-dimensional simulations of a low-density polyethylene (LDPE) autoclave reactor under normal operating conditions. For the conditions used, the reactor is not very well mixed; thus, the common model approximation of a perfectly stirred reactor is not warranted. The simulations verify the sensitive nature of the polymerization reactors and indicate a need for optimizing operating parameters.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430113
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  • 17
    Electronic Resource
    Electronic Resource
    Simulation of decoking of thermal cracking coils by steam/air-mixtures (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 118-126 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A rigorous approach was developed for the simulation of the decoking of an industrial cracking furnace. A one-dimensional heterogeneous reactor model, which accounts for the interfacial gradients between the process gas and the coke surface, was used to simulate reactor coils. Both the combustion and steam gasification of the coke layer were taken into account. The reactor model for the decoking was coupled with a detailed firebox simulation model. The initial profile of the coke layer thickness, required for the decoking calculations, was obtained by a run-length simulation. The evolution with time of the temperature distribution inside the cracking coil and in the furnace was generated simultaneously, which made it possible to understand the decoking operation in detail and to predict its duration accurately.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430114
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  • 18
    Electronic Resource
    Electronic Resource
    Dynamics of semibatch polymerization reactors: II. Pilot-plant study (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 157-165 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A semibatch flow scheduling strategy proposed by Teymour and Ray (1989, 1996) is evaluated for a polymerization reaction conducted in a pilot-plant reactor. The reaction used is the free radical terpolymerization of styrene, α-methyl styrene, and acrylic acid monomers initiated by an organic peroxide initiator and carried out in the presence of a reactive glycol ether solvent. This strategy was tested in both single batch and sequential semibatch modes. The process was shown to produce polymer of constant molecular weight properties and composition as inferred from acid number and monomer conversion measurements. This process could be used for obtaining polymer products from a semibatch reactor that are of comparable quality to CSTR products. Results indicate success of this process at meeting this objective; however, practical considerations relating to agitation and temperature control need to be properly addressed to ensure this success.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430118
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  • 19
    Electronic Resource
    Electronic Resource
    Steady-state multiplicity in cocurrently cooled autothermal reactors (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 127-134 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The steady-state simulation of a cocurrently cooled autothermal fixed-bed reactor was carried out using a 2-D heterogeneous mathematical model. The ammonia synthesis was chosen as a case study. Unlike the not-autothermal cocurrent reactor, which is unconditionally stable, the autothermal cocurrent reactor shows multiple steady states within a broad range of operating conditions. This finding, not reported in the literature, is explained through the mass transport from the bottom to the top of the reactor, associated with a feedback of energy. The feedback of heat, which is inherent to autothermal reactors, leads to an ignition-extinction phenomenon similar to that found in the countercurrent configuration. The influence of different parameters on the stability of the autothermal cocurrent reactor was analyzed. The regions where steady-state multiplicity occurs were compared with those presented by the autothermal countercurrent reactor. The influence of an additional heat exchanger on the reactor stability was considered.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430115
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    Analysis of νi/κTx in solvent mixtures at the critical line (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 277-280 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430133
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    Electronic Resource
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    Rheological simulation of in-line bubble interactions (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 265-267 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430130
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  • 22
    Electronic Resource
    Electronic Resource
    Analysis of nucleation and crystal growth data using the interfacial supersaturation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 268-272 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430131
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  • 23
    Electronic Resource
    Electronic Resource
    Boiling heat transfer of Nitrogen in a thermosyphon condenser-reboiler (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 339-344 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental investigation was conducted to determine the boiling heat-transfer characteristics in a thermosyphon condenser-reboiler of air-separation plants. The test section was a plate-fin heat exchanger of practical size of 0.106 m width and 2.56 m length. The testing fluid was nitrogen. Experiments were carried out within a range of pressure from 150 to 300 kPa, submergence from 1.95 to 2.80 m, and heat flux up to 11 kW/m2 under constant wall-temperature condition. The liquid superheat at the onset of boiling was rather significant. The boiling heat-transfer coefficients obtained agreed well with Chen's correlation modified by Colburn's J factor within a mean deviation of 9.3%.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430207
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    Electronic Resource
    Electronic Resource
    Masthead (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997) 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430101
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  • 25
    Electronic Resource
    Electronic Resource
    Efficient sampling technique for optimization under uncertainty (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 440-447 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The concept of robust design involves identification of design settings that make the product performance less sensitive to the effects of seasonal and environmental variations. This concept is discussed in this article in the context of batch distillation column design with feed stock variations, and internal and external uncertainties. Stochastic optimization methods provide a general approach to robust/parameter design as compared to conventional techniques. However, the computational burden of these approaches can be extreme and depends on the sample size used for characterizing the parametric variations and uncertainties. A novel sampling technique is presented that generates and inverts the Hammersley points (an optimal design for placing n points uniformly on a k-dimensional cube) to provide a representative sample for multivariate probability distributions. The example of robust batch-distillation column design illustrates that the new sampling technique offers significant computational savings and better accuracy.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430217
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    Electronic Resource
    Electronic Resource
    Analysis of cake growth in cake filtration: Effect of fine particle retention (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 33-44 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Equations were derived that describe the dynamics of cake growth in cake filtration, and methods for their solutions were developed. In deriving the equations, the moving boundary nature of the cake formation process and the effect of fine particle retention were considered. It was shown that fine particle retention may contribute significantly to the decrease of cake permeability and thus alters the performance of cake filtration even if the amount of fine particles involved is small. Through numerical examples, it was also demonstrated that fine particle retention in filter cakes may cause serious errors in determining the constitutive relationships from filter test data.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430106
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  • 27
    Electronic Resource
    Electronic Resource
    Characteristics of high-pressure liquid-solid fluidization (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 45-57 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fundamental characteristics of liquid-solid fluidization at high pressures (up to 21 MPa) and moderate temperatures (up to 89°C) are investigated. Properties under study include minimum fluidization velocity (umf), bed voidage at minimum fluidization, and bed expansion. Devices for in-situ measurements of physical properties of the liquid in the bed are developed, and measurements are carried out to quantify the pressure and temperature effects on the fluidization behavior. The results indicate that under high pressures and moderate temperatures, liquid-solid fluidization behavior is affected significantly by the variation of liquid density and viscosity with pressure. As the pressure increases, the liquid viscosity and density increase, yielding an increased drag force and buoyancy force on the particles, and hence a decreasing umf and an increasing bed expansion for a given liquid flow rate. An increase in temperature has an opposite effect on the physical properties of the liquid, increasing umf and decreasing the bed expansion for a given liquid flow rate. Various correlations proposed in the literature for umf and bed expansion, including those by Richardson and Zaki (1954) and Chitester et al. (1984), are applicable to high-pressure and high-temperature conditions when proper account is made of the liquid physical properties under bed operating conditions.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430107
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  • 28
    Electronic Resource
    Electronic Resource
    Asymptotic models for H2S absorption into single and blended aqueous amines (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 58-63 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Asymptotic power series solutions for the mass-transfer enhancement factor for absorption of a gas component into a liquid where it undergoes irreversible instantaneous chemical reaction(s) with one and two liquid-phase reactants are developed in this work. The Padé technique is used to extend the region of applicability (accelerate the convergence) of the four-term asymptotic power series solutions. The resulting modified asymptotic expressions for the enhancement factor show excellent accuracy over a wide range and can be used to predict enhancement factors as low as 2 with an error of about 5% compared to the exact numerical solution. Predictions of these new asymptotic solutions are compared with experimental absorption data for H2S absorption into aqueous methyldiethanolamine and H2S absorption into aqueous mixtures of methyldiethanolamine and diethanolamine obtained in a laminar-jet absorber. The absolute mean deviations of the predictions from the experimental absorption data for the single and mixed amine solutions were 4.6% and 2.4%, respectively.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430108
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  • 29
    Electronic Resource
    Electronic Resource
    Analysis of rate enhancement in a periodically operated trickle-bed reactor (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 166-172 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When a trickle-bed reactor (TBR) is operated periodically, the bed is fed with liquid on and off, while the gas phase passes continuously. Rates and conversions could be higher than those corresponding to the steady-state operation. In the “dry cycles” the heat generated by the reaction can drive the vaporization of the liquid phase, and a much more rapid “gas phase” reaction may occur. There is a trade-off between the potential for hot-spot formation and the fact that overall rates are higher during cycling. A qualitative understanding of the phase transition in TBRs is obtained by a simple phenomenological model that takes into account different transport and reaction mechanisms occurring in a catalytic particle under different cycling conditions. A mathematical model is used to predict results.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430119
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    Electronic Resource
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    Recent advances in modeling thermodynamic properties of aqueous strong electrolyte systems (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 180-195 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Theoretical and engineering models for the thermodynamic properties of strong electrolyte solutions have advanced significantly since 1985. This progress is notable in the ability to calculate selected properties of single and mixed strong electrolyte solutions over a wide range of temperatures and compositions, including effects of various nonelectrolytes, solvents and supercritical components. Theoretical studies have begun to consider more realistic fundamental interactions between various components in these systems. There have been several successful conversions of theories based on the mean spherical approximation and perturbation methods into engineering equations, without large numbers of empirical parameters. Other theoretical models seem almost ready for application to real systems. The capability to estimate a wide variety of thermodynamic properties accurately with a consistent set of equations and a small number of adjustable parameters has been achieved by several groups over limited temperature and composition ranges. Much work remains to be done, however, to understand completely the interplay and relative importance of various contributing energy effects.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430121
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  • 31
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    Vapor-liquid equilibria of the ternary mixture CH4 + C2H6 + CO2 from molecular simulation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 212-217 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The NpT + test-particle method for the calculation of vapor-liquid equilibria by molecular simulations is extended to ternary mixtures. It is applied to the system methane + ethane + carbon dioxide, for which all binary molecular interaction models are available from previous work. Methane is described as one-center Lennard-Jones fluid, ethane as two-center Lennard-Jones fluid, and carbon dioxide as two-center Lennard-Jones plus point quadrupole fluid. The unlike interactions are treated in the same way as the binary mixtures, using two parameters for each binary interaction. No ternary parameters are introduced. Vapor-liquid phase equilibria are calculated for the ternary mixture at the following temperature-pressure pairs: 233.15 K - 2 MPa; 250.5 K - 2 MPa; and 250.5 K - 3.04 MPa. Comparison of the simulation data with experimental and equation-of-state results shows excellent agreement. Bubble and dew densities are also reported.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430123
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  • 32
    Electronic Resource
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    Recovery and purification of paclitaxel using low-pressure liquid chromatography (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 232-242 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An efficient and economical low-pressure liquid chromatography process has been developed for paclitaxel recovery and purification directly from plant-tissue culture (PTC) broth. PTC broth is first diluted with ethanol to ensure padlitaxel dissolution and then passed through a column packed with a high-capacity polystyrene divinyl-benzene sorbent. A step increase in ethanol concentration in the mobile phase (ethanol:water) is used to concentrate and compress the taxane bands to as high as 29-fold of influent concentrations (about 1 mg/L). A recycle technique is then used to separate the concentrated paclitaxel band from other taxane bands, achieving 95% purity with more than 90% recovery and 99% purity with more than 80% recovery. In this process, the same low-pressure columns are used to capture, concentrate and purify paclitaxel. Theoretical predictions agree closely with the stepwise elution and recycle chromatography data. After validation, simulations are used to explore various design and operating alternatives. Analysis of the alternatives shows that the process cost can be further reduced by using higher feed concentration, larger loading volume, smaller particle size, and optimal gradient and recycle strategies.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430125
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    Phase equilibria for the mean-force potential of globular protein solutions (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 218-231 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When polymers are added to a solution containing proteins, the protein may deposit as an amorphous precipitate or as crystals. Experimental evidence indicates that from a thermodynamic viewpoint, an amorphous precipitate should be treated as a liquid phase dense in the protein and crystals as true solids. To understand the conditions under which protein precipitation or crystallization may occur, Gibbs-ensemble Monte Carlo simulation and Gibbs-Duhem integration techniques are used to calculate the liquid-liquid and liquid-solid phase boundaries for protein precipitation induced by polymers. In these simulations, the system is modeled using the pseudo-one-component approximation with an appropriate potential of mean force. The critical point for fluid-fluid phase equilibrium disappears as the attractive part of the mean-force potential becomes very short ranged. The accuracy of the second-order Barker and Henderson perturbation theory is examined by comparing the phase diagram predicted using this method with the simulation results. Perturbation theory is able to predict the general trends observed in the simulations but not with quantitative accuracy. Perturbation theory is then used to examine a broader range of conditions for protein deposition.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430124
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    Influence of particle-size distribution on entrainment solid rate in fluidized bed (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 260-262 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430128
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  • 35
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    Simulated moving bed under linear conditions: Experimental vs. calculated results (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 935-945 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simulated moving bed (SMB) was operated for the separation of mixtures of 2-phenyl ethanol and 3-phenyl-1-propanol on columns packed with Zorbax C18 bonded silica, using a 60:40 (v/v) solution of methanol and water as the mobile phase. Series of four or eight columns were used. The experiments were carried out with low concentration mixtures, that is, under linear conditions. Band profiles of both compounds eluted from one of the columns during successive periods after steady state had been reached were recorded, as were the concentration histories at the extract and raffinate ports. These experimental results are compared to those predicted by two models: the linear ideal and the linear equilibrium-dispersive models of chromatography, applied to the SMB separator. These two models give excellent agreement between the experimental profiles and those calculated with the model. As expected, the profiles predicted by the ideal and the equilibrium-dispersive models differ only by the lack of dispersion in the profiles given by the former. The latter model is demonstrated to be a solid, reliable tool for further studies of the SMB design and optimization.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430409
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    Electronic Resource
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    Gas holdup in slurry bubble columns: Effect of column diameter and slurry concentrations (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 311-316 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To study the influence of particle concentration on the hydrodynamics of bubble-column slurry reactors operating in the heterogeneous flow regime, experiments were carried out in 0.10, 0.19, and 0.38-m-dia. columns using paraffinic oil as the liquid phase and slurry concentrations of up to 36 vol. %. To interpret experimental results a generalization of the “two-phase” model for gas-solid fluid beds was used to describe bubble hydrodynamics. The two phase identified are: a dilute phase consisting of fast-rising large bubbles that traverse the column virtually in plug flow and a dense phase that is identified with the liquid phase along with solid particles and entrained small bubbles. The dense phase suffers backmixing considerably. Dynamic gas disengagement was experimented in the heterogeneous flow regime to determine the gas voidage in dilute and dense phases. Experimental data show that increasing the solid concentration decreases the total gas holdup significantly, but the influence on the dilute-phase gas holdup is small. The dense-phase gas voidage significantly decreases gas holdup due to enhanced coalescene of small bubbles resulting from introduction of particles. The dense-phase gas voidage is practically independent of the column diameter. The dilute-phase gas holdup, on the other hand, decreases with increasing column diameter, and this dependence could be described adequately with a slight modification of the correlation of Krishna and Ellenberger developed for gas-liquid systems.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430204
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  • 37
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    Intraparticle diffusion in hydrogenation of 3-hydroxypropanal (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 475-485 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Strong intraparticle diffusion resistance was observed and the apparent effectiveness factors were measured for the hydrogenation of 3-hydroxypropanal (HPA) to 1,3-propanediol (PD) over Ni/SiO2/Al2O3 catalyst pellets at 45 to 80°C and 2.60 to 5.15 MPa in a stirred reactor with a spinning basket. A mathematical model was proposed to describe the intraparticle diffusion and to estimate the effective diffusion coefficients of HPA, PD and hydrogen under reaction conditions by a maximum likelihood function of the apparent effectiveness factors of HPA and PD. The calculated concentration distributions of HPA, PD and hydrogen in catalyst particles reveal an excess of hydrogen at 80°C and higher temperatures, but an excess of HPA at 45°C. It results in a weak dependence of the consumption formation rate of HPA and PD on the partial pressure of hydrogen at high temperature.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430220
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    Perturbation solution to the convection-diffusion equation with moving fronts (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 631-644 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Electrophoresis of a solute through a column in which its transport is governed by the convection - diffusion equation is described. Approximate solutions to the convection - diffusion equation in the limit of small diffusion are developed using perturbation methods. The diffusion coefficient and velocity are assumed to be functions of space and time such that both undergo a sudden change from one constant value to another within a thin transition zone that itself translates with a constant velocity. Two cases are considered: (1) the thickness ∊f of the transition zone is negligible compared to the diffusional length scale, so the zone may be treated as a singular boundary across which the diffusion constant and velocity suffer discontinuous changes; (2) the transition zone is considerably wider than the diffusional length scale, so the diffusion coefficient and velocity, although sharply varying, are smooth functions of position and time. A systematic perturbation expansion of the concentration distribution is presented for case 1 in terms of the small parameter ∊ = 1/Pe. A lowest order approximation is given for case 2. A suitably configured system analyzed here can lead to progressive accumulation, or focusing, of the transported solute. The degree of focusing in case 1 scales with ∊-1, whereas in case 2 it scales with (∊f∊)-1/2, and thus increases much more weakly with increasing Pe. A separation based on this concept requires development of materials and devices that allow dynamic tuning of the mass-transport properties of a medium. This would make it possible to achieve progressive focusing and separation of solutes, such as proteins and DNA fragments, in electrophoretic media with an unprecedented degree of control.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430309
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  • 39
    Electronic Resource
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    Continuous drying of a solid wetted with ternary mixtures (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 681-692 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence on drying selectivity of the continuous-contact mode between a solid wetted with ternary mixtures and a gas stream was theoretically studied. The liquid mixtures, ethanol-isopropanol-water and water-ethanol-acetone, were used. A mathematical model describing a gas-phase-controlled process was developed, and the influence of the process variables was studied by simulations. In addition to the inlet composition of the moisture and temperature of the solid, gas composition has the most important effect on selectivity. Small changes of gas composition, either imposed or spontaneous, may modify completely the process trajectory. The extent of these effects depends on the ratio between the flow rates of inlet gas and liquid contained in the solid. Because of their effects on the evolution of temperature and composition, the operating pressure and energy sources other than convection are also useful in controlling the selectivity. Since all these variables determine the composition of the remaining liquid and thereby product quality, their influence should be predictable. The model may be a valuable tool for exploring the process, provided that drying is gas-phase-controlled.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430314
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  • 40
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    Sherwood number for a swarm of adsorbing spheroidal particles at any peclet number (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 844-846 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430330
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  • 41
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    Finite-element simulation of mixing: 1. Two-dimensional flow in periodic geometry (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 577-587 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Complex mixing flows and mixing parameters are calculated to evaluate mixing quality on the basis of kinematic parameters together with a statistical analysis. The results allow for a comparative evaluation in terms of geometry and flow parameters. The evaluation is limited to two-dimensional flows with moving boundaries in periodic motion such as the flow in the cross section of a twin-cam mixer. The finite-element calculation requires a remeshing procedure for every time step with special techniques to upgrade mixing variables from one time step to the next. The relative mixing quality of single cam and co: or counterrotating cam devices are compared by evaluating segregation scale, length stretch, and efficiency. The numerical results exhibit a good correspondence with their experimental counterpart.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430303
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  • 42
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    Resonant microwave power absorption in slabs and cylinders (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 615-624 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Resonant power absorption is an important phenomenon during microwave heating. The resonances that occur when plane electromagnetic waves are incident on infinitely long cylinders and slabs are investigated as a function of sample dimensions. For cylinders two kinds of incident waves are studied: TMz when the electric field is oriented along the axis of the cylinder and TEz when the magnetic field is oriented along the axis. At a resonant condition the overage power absorbed by the sample is a local maximum. Due to attenuation within the sample the resonances decrease in intensity as the sample size increases. Using the dielectric properties of water, resonances are found to be a function of the ratio of the sample dimension to the wavelength of radiation, λs, in the sample. For slabs of thickness L and integer values of n, resonances occurred at L/λs = 0.5n; for cylinders of diameter D, resonances occurred at D/λs = 0.5n - 0.257. The generality of these relations to predict resonances in other food samples are shown using existing dielectric data. Resonances in cylinders for both polarizations occurred at similar radii. However, the radius at which the first resonance occurred for the TMz case was absent in the TEz case.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430307
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    Transient behavior of pulsed particulate fluidized beds (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 625-630 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient phenomena in solid-liquid fluidized-bed systems are important in designing pulsed, countercurrent (multistage) fluidized-bed contactors of the Cloete-Streat type at high-solids flow rate. Of particular interest are the residence times or corresponding velocities of porosity gradients in the bed and the excess or overshoot height of the bed after refluidization. Theory assuming local equilibrium between holdup and velocity of the phases (local-equilibrium model) for stepwise perturbations in the liquid flow is readily available. It is investigated whether the local-equilibrium theory can be used for more complex perturbations and whether inertia effects, such as are encountered in countercurrent multistage fluidized-bed systems, can be ignored. Therefore, the detailed particle-bed model of Foscolo and Gibilaro, which incorporates inertia effects, was applied to investigate the transient behavior of fluidized-bed systems. Transient fluidization experiments were performed with a broad range of water-fluidized particles in a laboratory-scale multistage fluidized-bed contactor. The operating conditions corresponded to those for countercurrent contact.Numerical simulations with the particle-bed model predict satisfactory experimental results. The “overshoot” heights of the fluidized bed were estimated correctly by the particle-bed model, whereas the local-equilibrium model only provides a conservative estimate. However, the local-equilibrium model allows an analytical solution that is more interesting for design, as it avoids tedious calculations. The residence time of the last perturbation before the fluidized bed relaxes to steady state was estimated with similar accuracy by both models.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430308
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    Steady spontaneous capillary flow in partially coated tubes (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 645-654 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A spontaneous, steady capillary flow is produced for a liquid index in a circular tube that is partially coated with a surface modifier to create a discontinuous wetting condition between upstream and downstream portions of the tube. As a means of demonstrating that the flow configuration may prove useful as a diagnostic tool in studies concerning capillarity and the physics associated with the moving contact line, average steady velocities are predicted and compared against a large experimental data set that includes the effects of tube dimensions and fluid properties. To access a wider range of tube diameters (0.516-9.88 mm), experiments are performed employing “U-tubes” tested in the low-gravity environment of a drop tower, in addition to straight capillary tubes tested horizontally in a laboratory. The sensitivity of the steady capillary flow to surface cleanliness is dramatic.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430310
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    Permeability of filter cakes of palm oil in relation to mechanical expression (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 673-680 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Permeability and compressibility data are required for an adequate process model for compressible-cake filtration and mechanical expression. Experimental and modeling results of the permeability of palm-oil filter cakes (a highly compressible viscoelastic material) are combined with compressibility data, leading to a model for the expression step. Permeability measurements show that permeability depends strongly on the quantity of fine particles in the cake. Removal of fine particles from the slurry before expression significantly increases the solid-phase content during expression due to higher permeability. Modeling results of the expression step show that for palm-oil filter cakes there is a pressure above which the attainable mass fraction of solids becomes independent of pressure. Decrease in specific cake resistance has two effects: a higher mass fraction of solids at the same pressure and a higher pressure at which the mass fraction of solids is not affected further.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430313
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    Modeling and optimization of a semiregenerative catalytic naphtha reformer (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 740-753 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Modeling and optimization of a semiregenerative catalytic naphtha reformer has been carried out considering most of its key constituent units. A detailed kinetic scheme involving 35 pseudocomponents connected by a network of 36 reactions in the C5-C10 range was modeled using Hougen-Watson Langmuir-Hinshelwood-type reaction-rate expressions. Deactivation of the catalyst was modeled by including the corresponding equations for coking kinetics. The overall kinetic model was parameterized by bench-marking against industrial plant data using a feed-characterization procedure developed to infer the composition of the chemical species in the feed and reformate from their measured ASTM distillation data. For the initial optimization studies, a constant reactor inlet temperature configuration that would lead to optimum operation over the entire catalyst life cycle was identified. The analysis was extended to study the time-optimal control profiles of decision variables over the run length. In addition, the constant octane case was also studied. The improvement in the objective function achieved in each case was determined. Finally, the sensitivity of the optimal results to uncertainty in reactor-model parameters was evaluated.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430319
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  • 47
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    Microwave heating of the continuous flow catalytic reactor in a nonuniform electric field (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 754-760 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Temperature profiles in the continuous-flow reactor with a fixed bed placed in a nonuniform microwave field are predicted by considering specific on - off regulation of the microwave power and local distribution of the electric-field intensity. The spatial and temperature dependence of the electric-field intensity affects the heating appreciably, as shown by indirect measurements. Results of numerical calculations agree with experimental data of outlet temperature and explain temperature oscillations in the outlet flow. The model developed allows an accurate description of microwave heating in the continuous-flow reactor associated with specific regulation of microwave power. The hydrolysis of sucrose catalyzed by the strongly acidic cation-exchange resin Amberlite 200C in R-H form was chosen as the reaction system. Calculated conversions of sucrose based on predicted temperature profiles agree with experimental data.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430320
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    Oxidative dehydrogenation of butane using membrane reactors (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 777-784 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxidative dehydrogenation of butane was studied at temperatures between 450 and 550°C using a conventional fixed-bed reactor and inert membrane catalytic reactors with different feed arrangements. When inert membrane reactors were employed, a ceramic membrane was used to distribute oxygen to a fixed bed of V-Mg-O catalyst. The membrane reactor was found to be more efficient than a fixed-bed reactor under most of the conditions investigated. In addition, in the membrane reactor the formation of hot spots decreased considerably, leading to a more stable and safer operation.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430322
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    Reaction rates in fractal vs. uniform catalysts with linear and nonlinear kinetics (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1691-1699 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pore fractal objects are expected to be optimal catalysts, since material is supplied to the narrower pores, which are also shorter through the larger pores where diffusion resistance is smaller. To demonstrate this, diffusion and reaction were simulated on Sierpinski-gasket-type fractal objects and on the corresponding nonfractal uniform-pore structures of the same size, porosity and reactive area. Positive order reactions limited by Knudsen diffusion were shown to exhibit larger rates in fractal than in uniform-pore objects. Fractal catalysts also exhibited a new intermediate domain in which the rate depends only weakly on the kinetics parameters. In nonmonotomic kinetics the branching point (bifurcation point) was extremely sensitive to the pore structure.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430706
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  • 50
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    Electrochemically modulated complexation process for ethylene/ethane separation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1709-1716 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An electrochemically modulated complexation (EMC) process was designed to selectively extract and concentrate ethylene from a feed-phase mixture with ethane. Unlike previous EMC processes, where the separation was based on equilibrium solubility differences, this separation was based on differences in the rate of complexing with copper(I) solution between the two gases. The EMC process employed flowthrough electrolysis cells that electrochemically modulate aqueous-phase copper chlorides between high, copper(I), and low, copper(II), affinity states. The liquid phase in the high affinity form contracts a feed gas phase in a hollow-fiber membrane module for selective extraction and contacts the receiving gas phase in the low affinity form for concentration. Experimental results and modeling of the process are reported.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430708
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    Synthesis of crystallization-distillation hybrid separation processes (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1751-1762 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A systematic method to synthesize crystallization-distillation hybrid separation processes is presented. Two classes of hybrids are identified for binary mixtures. The first bypasses azeotropes and tangent pinches, while the second bypasses eutectics. Guidelines for flow-sheet selection are proposed based on an analysis of simple eutectic, constant relative volatility systems. In addition, the hybrids are compared to both extractive and adductive crystallization in order to determine the conditions under which solvent-based crystallization techniques outperform the proposed hybrid configurations. The method is extended to ternary mixture. The use of stream combination and complex distillation columns is also considered.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430712
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    Dehydrogenation of propane using a packed-bed catalytic membrane reactor (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1819-1827 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In a high-temperature catalytic membrane reactor, a plug-flow reactor is combined with a gas-separative membrane. By selectively removing one of the reaction products, the reaction mixture is prevented from reaching equilibrium, and a higher conversion can be obtained. This concept is only valid for reactions that are limited by the thermodynamic equilibrium, such as the direct dehydrogenation of propane to propene. A tubular H2-selective silica membrane was characterized [αH2/C3H8 = 70-90 at 500°C] and used as the gas-separative membrane. The membrane reactor was filled with a chromia/alumina catalyst. The kinetics of the catalyst was studied. At 500°C the deactivation of the catalyst is slow, and the propene yield is almost constant for at least 10 h of operation. Under well-chosen process conditions, the propene yield is at least twice as high as the value obtained at thermodynamic equilibrium in a conventional reactor.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430717
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    Measurement of ultrasonic forces for particle-liquid separations (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1727-1736 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The magnitude and direction of the ultrasonic radiation forces that act on individual particles in a standing-wave field were determined using a microscope-based imaging system. The forces are calculated from measured particle velocities assuming that the drag force, given by Stokes' law, is exactly counterbalanced by the imposed ultrasonic forces. The axial primary radiation force was found to vary sinusoidally with axial position and to be proportional to the local acoustic energy density, as predicted by theory. The magnitude of the transverse primary force was determined by two independent methods to be about 100-fold weaker than the axial force. Separation concepts exploiting the transverse force for cell retention have been successful despite the great disparity in magnitude between the axial and transvers-force components. This may be explained by the reduced hydrodynamic forces on aggregated particles in transverse flow due to their alignment in the sound field.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430710
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  • 54
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    Surfactant effects on absorption in the presence of induced interfacial turbulence (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1909-1913 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430726
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    Improving clay-based tailings disposal: Case study on coal tailings (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1894-1903 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The role of swelling clays in hindering the compressional dewatering characteristics of coal-mine tailings is examined. The effects of electrolyte concentration and ion exchange in improving the shear and compressional rheology are compared. Suspensions studies include actual mine tailings (thickener feed and thickener underflow) as well as synthetic clay dispersions made from clay collected from the coal seam. It was shown that the most important parameter in controlling the properties of the tailings suspension is “controlled” dispersion in the presence of a Ca2+ electrolyte concentration in excess of that required to (1) prevent initial swelling and (2) provide full cation exchange of the clay. Under these electrolyte conditions, complete delamination of the clay did not occur, and both the dewatering and handling characteristics of the resultant suspensions improved dramatically.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430724
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  • 56
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    Spread and rebound of liquid droplets upon impact on flat surfaces (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2169-2179 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The spread and rebound of droplets upon impact on flat surfaces at room temperature were studied over a wide range of impact velocities (0.5-6 m/s), viscosities (1-100 mPa.s), static contact angles (30-120°), droplet sizes (1.5-3.5 mm), and surface roughnesses using a fast-shutter-speed CCD camera. The maximum spread of a droplet upon impact depended strongly on the liquid viscosity and the impact velocity. The tendency of a droplet to deposit or to rebound is determined primarily by the liquid viscosity and the liquid/substrate static contact angle. A model more broadly applicable than existing models was developed to predict maximum spread as a function of the Reynolds number, the Weber number, and the static contact angle. Based on the conservation of energy, a rebound model is proposed that predicts the tendency to rebound as a function of maximum spread and static contact angle.The maximum-spread model prediction agrees to within 10% with more than 90% of the experimental data from different sources. In the current study, the rebound model successfully predicts the tendency of a droplet to rebound.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430903
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    Mass and thermal transport analysis of oscillating flow with absorbent polymers (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2157-2168 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new concept for removing toxic gases with respirator applications based on inhalation and exhalation through absorbent polymer-lined tubes was studied. The two-way oscillatory flow through the respirator element enables capture and expulsion of toxic vapors, which is not feasible with activated charcoal because of the adverse effect of moist breath on the charcoal efficiency. To study the influence of various material, design and operating parameters on the performance of such a respirator, a numerical model that solves the governing equations of mass and heat transport in an oscillatory flow through an absorbent polymer-lined tube was developed and utilized with experimentally measured property data. Factors investigated include respirator element geometry, polymer and toxic vapor characteristics, and flowthrough speed. Results show a large delay in toxic gas penetration over that obtained by conventional one-way flow, and define the importance of partition coefficient, flow passage size, and length and velocity. Results are compared with data from simulated breathing experiments.
    Additional Material: 20 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430902
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    Analytical description of the Lennard-Jones fluid and its application (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2215-2226 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simplified exponential (SEXP) approximation, combining the exponential approximation and the first-order mean spherical approximation, is proposed to improve the equation of state for the Lennard-Jones (LJ) fluid. The SEXP approximation, which can be implemented in an analytical manner, yields better radial distribution functions of the LJ fluid. Extensive comparisons with two typical perturbation theories show that the SEXP approximation is more appropriate to describe the behaviors of the LJ fluid. The latest 33-parameter modified Benedict-Webb-Rubin equation, also calculated, is inadequate in the region of phase coexistence. The SEXP approximation is applied to the calculation of methane properties with much better results than the Peng-Robinson equation of state for saturated liquid densities and second virial coefficients.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430908
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  • 59
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    Temperature dependence of one-component permeation through a silicalite-1 membrane (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2203-2214 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The one-component steady-state permeation of gases through a silicalite-1 zeolite composite membrane as a function of the temperature is studied from 190 to 680 K for light hydrocarbons, noble gases, and some inorganic gases. In general, with increasing temperature the permeance shows a maximum followed by a minimum. For gases weakly adsorbed the permeance has only a minimum and for gases strongly adsorbed only a maximum is observed in the permeance. The permeance for various gases, for a feed pressure of 101 kPa, span four orders of magnitude. The lowest permeation is for i-butane at 300 K: a permeance of 0.07 × 10-8 mol. m-2.s-1.Pa-1. The highest value is observed for methane: a permeance of 70 × 10-8 mol. m-2.s-1.Pa-1 at about 240 K. A comparison between the isobars and the temperature dependence of the steady-state permeance, both at 101 kPa, shows that at the temperature where the amount adsorbed vanishes the permeance starts to increase. The temperature dependence of the steady-state fluxes through the silicalite-1 membrane can be described only if two diffusion mechanisms are taken into account. For high occupancies the mass transport can be described by equilibrium adsorption followed by surface diffusion and for low occupancies the mass transport can be described by activated gaseous diffusion. With increasing temperature the mass-transport mechanism shifts from the surface diffusion regime to the activated gaseous diffusion regime. With these two diffusivities modeling results agree well with experimental results for the one-component flux through the silicalite-1 zeolite membrane.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430907
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    Masthead (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997) 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431101
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    Gas-filled cavity structures and local void fraction distribution in aerated stirred vessel (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2921-2931 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The local structural function obtained by a microresistivity probe at different hydrodynamic regimes is examined. The structures, such as the vortex-clinging structure, the appearance of one and two large cavities, small 3-3 structure, large 3-3 structure, and ragged cavities were recognized by frequency transformation of the time-domain structural function. An optimized phase discrimination in signal processing was used. The distribution of the local void fraction (α) in a pilot-size stirred tank was experimentally investigated, because almost no such data can be found in the literature. The two-phase mixture was composed of air and water; α was measured at 190 nodes in the vertical half-section plane of the vessel. Relative differences smaller than 9% between integrated values of α and measured gas holdups agreed reasonably well under all conditions.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690431105
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  • 62
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    Constrained MPCI: A weak persistent excitation approach (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2279-2288 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Model-predictive control and identification (MPCI) introduced by Genceli and Nikolaou in 1996 is a novel approach to the identification of processes under constrained model-predictive control. MPCI solves an on-line optimization problem that involves (a) a standard MPC objective; (b) standard MPC constraints; and (c) persistent excitation (PE) constraints. The on-line optimization problem is computationally demanding. To alleviate that problem, we take a frequency-domain approach to formulating the PE constraints. This approach relies on the following fact: a signal is persistently exciting of order n, if its two-sided power spectrum is nonzero at no fewer than n points. Therefore, persistently exciting input signals can be parametrized over a finite horizon as a sum of sinusoid terms with nonzero coefficients. Used in the MPCI framework, the last requirement generates a set of completely decoupled reverse-convex constraints that are combinatorially tractable from a computational point of view. The effectiveness of the proposed MPCI method is demonstrated through simulations. For the SISO systems studied, computation of the global optimum could be handled combinatorially in real-time using PC hardware.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690430913
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    Design and retrofit of sensor networks in process plants (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2300-2306 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel procedure to find cost-optimal sensor networks is proposed. Cost is minimized subject to qualifying constraints that are related to certain requirements of data reconciliation. One basic qualifying constraint is a desired level of precision of reconciled values for a selected set of variables. Since precision requirements lead to multiple solutions, other qualifying constraints are proposed. These constraints are availability, resilience, and error detectability. Definitions for these terms are given and their impact on the results is presented.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430915
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    Pore-structure optimization of calcium carbonate for enhanced sulfation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2323-2335 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A modified CaCO3 sorbent with an open internal pore structure is prepared and its sulfation characteristics are investigated in an entrained flow reactor at high temperatures (900-1,100°C) and short contact times (20-600 ms) using small particle sizes (〈 5 μm). The most distinguishing feature of this modified carbonate (MC) is its 70-75% sulfation conversion within 0.5 s, which is substantially higher than any other sorbents published. The MC is prepared by carbonation-precipitation from a calcium hydroxide suspension by optimizing the operating parameters to generate carbonate particles of the desired pore structural properties. The high initial surface area combined with its open pore structure and pore-size distribution of its calcine contribute to its high reactivity. The calcined MC possesses a significant portion of its pore volume in the 50-200 Å range. This size range represents an optimum pore size for sulfation since it provides a reasonably high surface area and is less susceptible than 〈 50 Å pore sizes, to pore filling, or pore-mouth plugging due to the formation of higher molar volume CaSO4. Investigation with other carbonates reveals that a much higher portion of their calcines' porosity lies in the smaller pores, which leads to premature termination of sulfation. Results show the impact of internal pore structure on initial reactivity and ultimate sorbent conversion.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430917
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    Analysis of bacterial swimming speed approaching a solid-liquid interface (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1341-1347 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Previous experimental studies have found that surface interactions significantly affect the transport of motile bacteria through small tubes, along solid surfaces, and through porous media. However, the role that hydrodynamic forces play in the interactions between solid surfaces and motile bacteria remains unclear. In this study, the swimming speeds of populations of Escherichia coli bacteria were measured near (〈 10 μm) and far (〉10 μm) from a flat glass surface at four ranges of orientations to the surface (0°-45°, 45°-90°, 90°-135°, and 135°-180°). Populations of bacteria close to the surface and moving in the orientation range most perpendicular (0-45°) to the surface experienced the greatest change in the swimming speed when compared to the population in the same orientation range located far from the surface. The decrease in swimming speed experienced by this population was on the same order as that predicted by hydrodynamic models of bacterial swimming near surfaces.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430523
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    Lagrangian simulation of turbulent particle dispersion in electrostatic precipitators (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1403-1413 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Industrial design of electrostatic precipitators is based on the transport theory developed by Deutsch (1922), which assumes that transverse turbulent mixing is effective enough to maintain the concentration profile uniform throughout the cross section (i.e., turbulent diffusivity is assumed infinite). To improve understanding of turbulent particle dispersion under the influence of electrostatic forces, a database on particle trajectories was first generated, based on the flow field from a direct numerical simulation of a plate-plate precipitator (Soldati et al., 1993). The effect of various parameters, such as particle size, charge and particle migration velocity, on dispersion and collection efficiency was investigated. Results show that particle concentration profiles are not uniform due to finite values of “turbulent diffusion” coefficient. The simulations indicate that the early stages of particle collection are controlled by particle migration velocity, while final stages are controlled by turbulence diffusion mechanisms.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430604
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    Gas-holdup measurements in bubble columns using computed tomography (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1414-1425 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A computed tomographic scanner was developed for imaging gas-holdup distributions in two-phase flow systems such as bubble columns and fluidized beds. The scanner has been used to study the effects of various operating parameters (such as column diameter, superficial gas velocity, and distributor type) on the gas holdup and its distribution in an air-water bubble column. The experimental investigation shows that the column dimensions have no significant effect on the void fraction when the column diameter is greater than 0.15 m. Differences in the holdup distribution due to the kind of distributor used are significant only at low gas flow rates. Surface tension of the liquid has a profound influence on the gas holdup and its distribution.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430605
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    Crystallization of nanosized silicon powder prepared by plasma-induced clustering reactions (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2610-2615 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Nanosized silicon powders were prepared by gas-phase cluster agglomeration reactions in a low-pressure silane plasma. The formation and agglomeration of clusters leading to the growth of primary particles of powder were studied by in-situ techniques including mass spectroscopy and laser light-scattering experiments. These powders, generally amorphous and crystallized in a reducing atmosphere, were studied in detail by Raman spectroscopy and high-resolution electron microscopy, which revealed a very rough surface of as-prepared single powder particles with structures of 1 to 2 nm. Upon 1-h annealing at temperatures between 300 and 600°C, circular contrast features, 1.5 to 2.5 nm in size, are observed in the amorphous particles, which show medium-range order. A distinct onset of crystallization is observed at 700°C with structures ranging from very small crystalline ordered regions of 2.5-3.5 nm in size to fast-grown multipletwinned crystallites. The crystallization behavior is influenced by the clusters that form primary particles. Observed sintering behavior cannot be explained by a classical approach; hence, theoretical models need to be adapted to nanosized powders.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431303
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    Carbothermally prepared nanophase SiC/ Si3N4 composite powders and densified parts (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2624-2635 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Nanophase SiC/Si3N4 composite powders were synthesized by the carbothermal nitridation of SiO2. These powders have desirable characteristics of high quality with oxygen contents on the order of 1.5 to 2 wt. %, surface area of ∼ 10 m2/g, submicron α-Si3N4, low metallic impurity levels, and a homogeneous distribution of the nanophase SiC phase. High-resolution TEM analysis has shown that the content and size of the nanophase SiC can be varied from 0.5 to 50 wt. % and 25 to 500 nm, respectively, through proper control of raw materials and reactor conditions. To determine how the nanophase SiC reinforcement affects the mechanical properties of Si3N4, densified components were fabricated using both pressureless and pressure-assisted densification methods. TEM analysis revealed that the nanophase SiC particles are distributed both intergranularly and intragranularly throughout the Si3N4, matrix. By controlling the sintering additive package and the sintering conditions, the ratio of inter- to intragranular SiC can be adjusted. Mechanical property measurements at elevated temperatures showed a dramatic improvement in high-temperature strength and creep resistance over components made with commercially available powders.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431305
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    Generation of unagglomerated, Dense, BaTiO3 particles by flame-spray pyrolysis (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2665-2669 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fine particles of dense, high-purity, crystalline BaTiO3were produced by flame-spray pyrolysis. A 0.5-M (Ba:Ti = 1:1) solution of barium acetate, titanium lactate, and water was aerosolized using an ultrasonic generator, and the droplets were delivered into the core of an annular diffusion flame (H2/air) reactor. For all investigated temperatures [∼1,000-∼2,000°C adiabatic], the generated powders were chemically pure, crystalline (primarily tetragonal phase with hexagonal and cubic polymorphs), and unagglomerated. At a low-flame temperature (∼1,000°C ad.), the particles produced were hollow and irregularly shaped. Particles produced at higher flame temperatures (〉∼1,500°C ad.) were dense and homogeneous. Particles showed a transition from a nonspherical porous morphology to a spherical dense morphology with increasing temperature. By increasing residence time, the temperature at which particles became spherical and dense was reduced. Flame-spray pyrolysis provides a useful method for forming dense particles of high melting point materials by aerosol-phase densification.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431310
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    Perovskite-type oxide membranes for the oxidative coupling of methane (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2731-2740 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A series of ion-conducting perovskites of the form [La1-xAx] [Co0.2Fe0.8] O3-δ (x = 0.4, 0.6 for A = Sr; × = 0.8 for A = Ba) were investigated for their use as a catalytic membrane for the oxidative coupling of methane (OCM). A-site cations consisting of La0.4Sr0.6 and La0.2Ba0.8 produce materials with the highest oxygen fluxes and result in C2+ selectivities of 50% at 1,098 K, which are significantly higher than those achieved with a powdered catalyst in a packed-bed reactor configuration. Selectivities in these materials appear to be limited by high oxygen ion recombination rates that compete for oxygen with the desired coupling reaction(s). The results also indicate that oxygen fluxes are not limited by diffusion, but by surface exchange rates at the oxygen-lean side of the membrane. The study on stability of these materials showed that all three perovskites could be reduced in a pure methane or ethane stream at 1,023 K, but they were totally stable under reaction conditions where oxygen is present.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431319
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    Fabrication of conductometric gas-sensing films by selected area chemical-vapor deposition (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2760-2764 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new selected-area chemical-vapor deposition (CVD) process to fabricate thin sensing films on a micromachined silicon-based, conductometric gas-sensor structure is reported. The CVD method is self-lithographic and does not require the use of masks to define the thin-film region. Since the films are deposited after silicon processing, the selection of film materials is not constrained by their compatibility with the etchants used in silicon micromachining. The presence of conductance electrodes underneath the growing film permits in-situ monitoring of film resistance. The rapid thermal response of the device allows precise termination of film growth once the film resistance has reached a value suitable for gas sensing. The application of this new CVD method is demonstrated for growth of thin platinum films, which are used for sensing of O2 and H2 gases.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431322
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    Thermochemistry of aqueous silicate solution precursors to ceramics (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2773-2784 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A quantitative understanding of the thermochemistry of silicate solution systems is necessary for the design, optimization and control of sol-gel, colloid and zeolite preparations. This review is intended to be a compendium of ready information for the growing number of chemical engineers active in solution-based materials synthesis. Experimental measurements of silica solubility, silicate speciation and silanol deprotonation in aqueous solutions are summarized and critiqued. The thermochemical properties of monomeric and dimeric silicate anions are also assessed. The trends that are then evident are compared with expectations from simplistic gas-phase molecular orbital calculations to illustrate the importance of solvation. Finally, the equilibrium behavior of simple silicate oligomers is rationalized, and the future direction to quantitative modeling of the behavior of more complex oligomers is suggested.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431324
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    Inorganic and organically modified rare-earth-doped silica gels (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2785-2792 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The fluorescence properties of inorganic and organically-modified rare-earth-doped sol-gel silica are presented. Eu3+-doped ormosils were prepared from Si(OCH3)4 and CH3Si(OCH3)3, (CH3)2Si(OCH3)2, (CH3)2Si(OC2H5)2, or (n-C3H7)Si(OCH3)3 in various proportions. Er3+-doped ormosils were prepared using Si(OC2H5)4 and CH3Si(OC2H5)3, (CH3)2Si(OC2H5)2 or C2H5Si(OC2H5)3. Gels derived from Si(OCH3)4 were also doped with the fluorinated Eu3+ precursors Eu(fod)3, (CF3SO3)3Eu, and (CF3CO2)3Eu·3H2O. The effect of metal ion codopants, which are known to inhibit clustering of Eu3+ in sol-gel silica, on Er3+ fluorescence is also considered. Fluorescence line-narrowing studies of Eu3+-doped samples indicated that significant Eu3 clustering occurs in both the ormosils and fluorinated precursor compositions. Lifetime measurements of the Eu3+-and Er3+ -doped ormosils showed longer lifetimes at low heat treatment temperatures relative to purely inorganic sol-gel silica, but no significant difference remained in fully densified samples. The longest lifetimes were observed for samples doped with the fluorinated precursors, indicating that the fluorinated ligands are effective at reducing the water content in densified gels.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431325
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    Nanoparticle synthesis of titanium silicalite for fiber, film, and monolith formation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2802-2808 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Zeolite fiber, film, and monolith were prepared by using nanosize titanium silicalite (TS-1) crystals. Films and fibers of TS-1 zeolite were optically transparent, which might be important for advanced optozeolitic materials. A permeation result of gases on monolith indicates that the gas permeation is governed by the Knudsen mechanism. All types of TS-1 zeolites manufactured in this work are observed to be MFI structure with an orthorhombic symmetry. These results suggest that nanosize zeolites have potential to allow morphological design with applications for advanced functional materials.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431327
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    Covalent grafting of optically active molecules on silica gels (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2820-2826 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Active organic molecules are grafted on the xerogel silica matrix by using functionalized alkoxides f-R′-Si(OEt)3, where f is a chemical function and R′ is an alkyl spacer to limit the degrees of freedom of the molecules. Organic-inorganic hybrid films are prepared in which optically nonlinear DRl chromophores are covalently bound to the silica network. These films exhibit a large and stable second-order nonlinear coefficient from second harmonic generation experiments. Protoporphyrin molecules are attached double covalently to the xerogel matrix via flexible organic spacers. Persistent spectral holes are still burnt with moderate fluency at 120 K.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431329
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    Forsterite powder prepared from water-soluble hybrid precursor (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2832-2836 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Partially polycondensed γ-aminopropylsilanetriol (APSTOL) was used as the silica precursor to prepare magnesium orthosilicate in the form of crystalline forsterite. Aqueous solutions of APSTOL and magnesium acetate were mixed and dried forming a water-soluble product that was converted into forsterite by heating to 1,000°C. The thermal evolution of the system was studied using TGA, FTIR, UV-VIS spectrophotometry, and XRD techniques, especially for the acetate decomposition and transformation of CSiO3-tetrahedra into the orthosilicate anions. The combustion of organics and the crystallization of forsterite proceed at temperatures 350 and 870°C, respectively. At intermediate temperatures, the system contains amorphous silicates with oligomeric and polymeric anions, which gradually depolymerize as temperature increases. The resulting crystalline product contains less impurities (periclase and enstatite) than samples prepared using other wet-chemistry techniques.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431331
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    Thermal decomposition of barium titanate precursor prepared by a wet chemical method (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2837-2843 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: As a part of fundamental study on the kinetics of electroceramics processing by wet chemical methods, barium titanate precursor gel was prepared using barium acetate and titanium tetra-isopropapoxide as starting materials. Experimental results indicated that barium acetate was distributed uniformly in the gel matrix formed by hydrolysis and polymerization of titanium tetra-isopropoxide. In the subsequent calcination of the gel, rapid formation of barium titanate was observed above 823 K, which resulted from the reaction between titania and barium carbonate or barium oxide(s). The dynamics of barium titanate formation under different heat-up programs was successfully simulated based on a proposed reaction model that incorporates a specified reactive portion of barium acetate in the gel matrix.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431332
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    Macroporous ceramics from ceramic-polymer dispersion methods (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2878-2888 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Porous ceramics were fabricated by firing ceramic-polymer composites prepared by casting dispersions containing cellulose acetate, water and colloidal ceramic particles (alumina and silica). Composite microstructures were determined by polymer phase separation. Polymer adsorption on the ceramic particles was necessary for the formation of controlled porosity in the composite and fired ceramic. Cellulose acetate adsorbed on alumina, but not silica particles. The microstructure of alumina-cellulose acetate composites was characterized by unagglomerrated alumina particles in a polymer matrix; relatively large pores (pore diameter ∼ 15 μm) formed when the alumina concentration was low (〈50 vol. % relative to the polymer in the dried composite), and smaller pores (pore diameter ∼2μm) developed at higher alumina contents. By contrast, silica-cellulose acetate composites contained agglomerated silica particles and a large pore structure invariant to silica content. Firing of alumina-cellulose acetate composites with ceramic contents greater than 40 vol. % resulted in crack-free porous ceramics with pore structures comparable to the original composites.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431339
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    Experimental study of the influence of the flow rates in SMB chromatography (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2970-2983 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Sorbex-type SMB separation instrument was operated for the separation of mixtures of 2-phenyl ethanol and 3-phenyl-l-propanol on a series of eight columns packed with Zorbax C18 bonded silica, using a 60:40 (u/v) solution of methanol and water as the mobile phase. The experiments were carried out with low-concentration mixtures under linear conditions. The elution profiles of both compounds between any two successive columns of the set under steady-state conditions were recorded while compositions of the raffinate and extract were measured. The four safety margin factors, βj, were divided into two groups: β1 and β4; β2 and β3 with different influence. Within the framework of the linear, ideal model of chromatography, a range of flow rates enables an SMB to operate successfully by completely separating the feed into its two components. The influence of different flow rates on the performance of the separator was studied by calculations and experiments with excellent agreement between both sets. With a simple optimization strategy, the four flow rates are selected to maximize the production rate or the concentration of extract and raffinate products, or to minimize the desorbent consumption. These optimum conditions are obtained by controlling the locations of concentration profiles inside the SMB. A reliable model for SMB operation allows a rapid and easy selection of the optimum experimental conditions.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431110
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    Multiscale integration hybrid algorithms for homogeneous-heterogeneous reactors (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 3031-3041 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Despite many available models at different reactor length scales, no models exist for designing homogeneous-heterogeneous reactors from first principles by linking molecular with macroscopic scales. Hybrid algorithms, based on a domain decomposition method, are proposed to couple a continuum fluid-phase transport/reaction model with a new efficient, real-time surface Monte Carlo model suitable for stiff problems. These algorithms properly treat surface heterogeneities and morphology and provide the exact boundary condition to the continuum fluid-phase model. In this way, molecular-scale information is integrated into a macroscopic chemical system. The methods are applied at atmospheric pressure to a stagnant boundary layer near a catalytic surface where heterogeneities are caused by adsorbate-adsorbate interactions. Both steady-state and transient simulations are performed. Such numerical methods have the potential for microscopic control of chemical processes through macroscopic control of experimental parameters. Applications to homogeneous-heterogeneous processes such as catalytic reactors, control of morphology of solid materials with atomic resolution, and corrosion processes are also discussed.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/aic.690431115
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    Molecular dynamics study of epitaxial growth and cluster formation on MgO(001) (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2765-2772 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new molecular dynamics (MD) code was developed to simulate the continuous deposition process of various molecules on substrates. In this methodology, various molecules can be deposited over substrate surfaces one by one in regular time intervals with definite velocity. It enables us to simulate homo- and hetero-epitaxial growth process as well as cluster formation process on various substrates. This new MD code has been already applied to study the homoepitaxial growth and Au cluster formation processes on MgO(00l). This article compares such phenomena as growth mode, temperature effect, and influence of surface defects in the homoepitaxial growth and Au cluster formation processes on the MgO(001), based on previous results. The continuous deposition process of MgO molecules was simulated. A 2-D smooth MgO layer without any defects was formed at 1,000 K, which was not realized at 300 K. High temperature is favorable for the complete layer-by-layer homoepitaxial growth. The deposition process of Au atoms on the Mg(001) differed significantly from that of MgO molecules. A 3-D hemispherical Au cluster was constructed on the MgO(001) and low temperature was found to be desired for the fabrication of highly active supported Au catalysts. The origin of the different growth mode and the different temperature effect in the homo-epitaxial growth and Au cluster formation on the MgO(001) was clarified.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431323
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    Intrazeolite nanocomposite catalysts: Co-Mo Sulfides for Hydrodesulfurization (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2809-2819 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It was, for the first time, demonstrated by means of FTIR, EXAFS, XPS, and XRF techniques that thermally stable Co-Mo binary sulfide clusters were synthesized in NaY zeolite cavities using Co and Mo carbonyls as precursors. The hydrodesulfurization (HDS) and hydrogenation activities of the intrazeolite nanocomposite sulfide clusters were examined as a function of composition. It was found that the highest HDS activity was attained at Co/Mo ≃ 1 (2 Mo/super cage or 12 wt. % Mo) and that the Co sites of the clusters were responsible for the reactions. The composition of the catalytically active intrazeolite Co-Mo sulfide clusters was implied to be Co2Mo2S6. The present intrazeolite nanostructure approach strongly suggested that the Co-Mo binary sulfide formation played a prominent role in the catalytic synergy generation. Metal carbonyl techniques were used in the preparation of intrazeolite Fe-Mo binary sulfides.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431328
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  • 84
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    Improved NLO properties through a liquid crystal phase poling (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2827-2831 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cross-linkable organic NLO chromophore called DRS was chemically incorporated into silica matrices using the sol-gel process. A number of electrically poled DRS/silica matrix systems were studied to elucidate the relaxation of the oriented organic chromophore by following the decay of UV absorption as a function of time and temperatures. The value of the second harmonic coefficient d33 was 47 pm/V for the DRS/silica matrix films (0.4 μm thickness). From the dramatic decrease in the UV absorption after poling at 80°C, it is speculated that the DRS may act as a liquid crystalline mesogenic group and is effectively oriented in poling at the phase (nematic) transition temperature (80°C). This argument was substantiated by investigating the phase behavior of DRS itself using both DSC and a polarized optical microscope. The DRS/silica system contained the ideal matrices to retain the oriented chromophore because of optical clarity, thermal stability and effective poling at the nematic liquid crystalline phase.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431330
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  • 85
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    Characterization of sputtered BZT thin films for MCM: Multichip module (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2844-2848 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ba(Zr, Ti)O3 [BZT] thin films were prepared for potential use as a decoupling capacitor for a multichip module (MCM). The crystal structure of BZT thin films on Pt(100)/MgO(100) and MgO(100) deposited from Ba(Zr0.2Ti0.8)O3 powder targets has a perovskite structure and is strongly (100) oriented. The crystal structure of BZT thin films on Pt(111) coated substrates differ from that of Pt(100)/MgO(100) and MgO(100) substrates. The degree of preferred (100) orientation on Pt(111)/SiO2/Si increased with increasing deposition temperature. We obtained a maximum dielectric constant of 150 at 600°C deposition. The loss tangent, leakage current and temperature dependence of capacitance of these BZT thin films were very small.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431333
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  • 86
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    Development of fine-scale piezoelectric composites for transducers (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2849-2856 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Piezoelectric ceramic/polymer composites, also known as piezocomposites, have been developed over the past two decades for electromechanical transducers to be used in both military and civilian applications. Recently, the thrust in these transducers is toward high operating frequencies, requiring fine-scale (〈200-μm ceramic-phase dimension) piezocomposites. Methods for processing these fine-scale piezocomposites are discussed. Current capabilities, as well as strengths and weaknesses of each method, are compared. The fundamentals of medical imaging and the importance of spatial scale in composite performance are reviewed. Several processing methods demonstrated composites with fine-scale ceramic phases (〈50 μm), and others have shown the potential to form composites with a ceramic scale of under 20 μm.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431334
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  • 87
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    La-Ni-oxide films, fibers and powders by La(MOE)3-Ni(acac)2 precursors (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2874-2877 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The preparation of LaNiO3, La4Ni3O10, La3Ni2O7-δ and La2NiO4 via La-methoxy-ethanolato-Ni(acac)2 precursor was investigated. From these precursors films, fibers and powders were prepared and heat treated to form LaNiO3 at temperatures as low as 750°C with a heating time of 4 h. The formation of La4Ni3O10 and La2NiO4 was complete at 1,000°C, for 4 h, while monophasic La3Ni2O7 required heating to 1,150°C, for 1 h. Pathways yielding various phases were also discussed briefly. The techniques used in this study are TGA, mass-spectroscopy, SEM-EDS, TEM-EDS, powder-XRD, and FT-IR spectroscopy.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431338
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  • 88
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    Permeation studies on oriented single-crystal ferrierite membranes (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 83-90 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Large, high-quality, single crystals of pure-silica ferrierite are synthesized, and the structure is described. Selected individual crystals (approximately 600 μm X 500 μm X 20 μm) are mounted in a membrane configuration so that only the 10-membered-ring channels (5.4 Å X 5.4 Å X 4.2 Å) or the 8-membered-ring channels (4.6 Å X 3.7 Å X 3.0 Å) are accessible for gas-molecule permeation. The first examples of transport exclusively through 8- or 10-membered-ring channel systems are reported and obtained through crystal orientation in the membrane. A series. of adsorption experiments are conducted to help select suitable probe molecules and evaluate the role of adsorption in the permeation process for single-crystal membranes. Methane, n-butane, isobutane and nitrogen probe molecules are used to study intracrystalline sorption and transport effects for different crystal orientations, pressures and temperatures. Both pure-gas selectivities and mixed-gas separation factors are reported. A mixed-gas separation factor of n-butane/isobutane = 116 for the 10-membered-ring orientation of the crystal at 383 K and a transmembrane pressure difference of 1.01 X 105 Pa are found using this technique. In addition, molecular sieving is observed for the 8-membered-ring orientation of the crystal since methane, but not butane, transport is observed for this crystal orientation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430111
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  • 89
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    Filter medium clogging during cake filtration (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 273-276 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430132
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  • 90
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    Mechanistic pressure drop model for columns containing structured packings (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 317-327 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mechanistic model was developed to predict pressure drop and flooding in packed columns equipped with corrugated packing of the regular type. It was developed after considerating the interaction of falling liquid film with the gas phase, based on mass-and momentum-conservation equations. Among the most common structured packings, the behavior of the Mellapak and BX types was analyzed. The aim of this work is to demonstrate how mechanistic models, developed for simple geometry, can also be used to compute pressure drops in cases where the geometry is more complex, as with a structured packing. This approach, based on the geometric characteristics of the packing and measurable parameters such as liquid holdup, enables the development of a basic model by limiting the number of adjustable parameters, which are numerous in all the available models. Because of its nature, this model is extremely easy to extend to different types of structured packings.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430205
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  • 91
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    Multimodel approach to mixed-gas adsorption equilibria prediction (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 388-397 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A thermodynamically consistent, multimodel approach for the prediction of mixture adsorption equilibria from pure-component adsorption isotherms is described. The ideal adsorbed solution (IAS) model is employed at low surface coverage, where potential attractive forces tend to govern adsorption behavior. An energetically quasi-homogeneous version of the Langmuir-Freundlich (LF) model is proposed at high coverage, where lateral adsorbate interactions and finite-adsorbent geometric constraints tend to homogenize such attractive forces. The classical LF model is used for intermediate coverage, where both energetic attractive and geometric constraining forces contribute significantly to mixed-gas adsorption behavior. A major benefit of this three-regime modeling method is that physically realistic adsorptive selectivities can be adhered to at both extremes of coverage, a property not generally shared by either the IAS or LF models taken singly. This three-regime approach yields better multicomponent equilibria predictions than IAS-only modeling approaches for many relatively nonideal adsorption systems.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430212
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  • 92
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    High-energy density storage of natural gas in light Hydrocarbon solutions (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1108-1113 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The storage of natural gas in other light hydrocarbons is one procedure for automotive natural gas usage that reduces the requirement of high-pressure or cryogenic storage. Model solutions of methane in n-butane, propane, and a liquefied-bottled-gas mixture were simulated using the Benedict-Webb-Rubin-Starling equation of state to determine the pressures necessary to maintain a liquid phase with perturbations in both temperature (-1°C to 38°C) and mole fraction (50 to 80 mol% methane). Methane storage in these liquid solutions is between 45 and 93% of an equal “tank” volume of compressed natural gas (CNG) at 21 MPa and 15°C. The simulation results indicate that solutions of this type contain 40 to 67% of the energy of gasoline at pressures that range from 60 to 40% that of CNG at 21 MPa and 15°C.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430424
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  • 93
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    Reaction invariance and stability in catalyst particles for production of Methanol (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1082-1090 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Industrial practice requires immediate and adequate responses to simple questions asked. For example, does a catalyst particle show any tendency to thermal oscillations in the form of a limit cycle? The root to such cycles is found in the eigenvalues of the Jacobian matrix to the reaction rate vector, applying the concept of reaction invariance, a direct consequence of Avogadro's stoichiometric principle for homogeneous stirred tank reactors. However, this concept does not generally apply to heterogeneous reactor dynamics, because it is found in the heterogeneous transports of heat, reactants and products. The transport is an irreversible phenomenon that usually contributes to shifting the eigenvalues to the left and hence increases the stability. Still, effects of transport mechanisms, both internally and externally, on the catalyst particle are important to assess in such industrial analyses. A practical industrial reactor for methanol production was the subject for stability studies, which concluded that thermal oscillations are not likely to occur. During this study, a number of interesting details were examined such as rank deficiency of the reaction matrix and root loci for the temperature dependence of the Jacobian matrix eigenvalues. A practical consequence of eventual thermal cycling of the catalyst particles is a long-term degradation of the catalyst efficiency, as seen in the ammonia synthesis.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430421
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  • 94
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    Effect of CO2 concentration on YBa2Cu3O6+x formation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1091-1099 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two reversible reactions are involved in YBa2Cu3O6+x formation: a reaction between BaCO3 and CuO forming BaCuO2 and CO2, and a reaction of BaCuO2 with Y2O3 and CuO forming YBa2Cu3O6 which undergoes phase transformation to YBa2Cu3O6+x upon cooling. In-situ isothermal time resolved HT-XRD of a thin film was used to quantify the effect of CO2 on the kinetics of the first reaction. Increased CO2 partial pressure shifts the reactions to higher temperatures. At high CO2 partial pressure (〉2 vol. %), the rate of the first reaction becomes essentially a step process with a very high activation energy. Noninstantaneous nucleation of the reaction products occurs at low CO2 partial pressure (0.5-1%) and temperatures (700°C). The data fit a 2-D diffusion-controlled mechanism with a zero nucleation rate for BaCO3 decomposition and a second-order nucleation rate for YBa2Cu3O6 formation. A comparison of the kinetics of a thin film (10 mm) as determined by HT-XRD with those of a thick sample (2 mm) determined by TG revealed that the transport of CO2 within the sample pores and to the ambient gas significantly affect the decomposition of BaCO3. For example, the formation of YBa2Cu3O6 in a thick precursor layer occurs in the 840 to 940°C range, exceeding by about 200°C that in which it is formed in thin films.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430422
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    Second-order reaction in a semibatch reactor (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1114-1116 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430425
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  • 96
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    Masthead (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997) 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430501
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  • 97
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    Polymer drag reduction in hydraulic capsule pipeline (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1117-1121 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430426
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  • 98
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    Effect of inlet conditions on scalar statistics in pipe mixing (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1947-1954 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recent experimental validation of theoretical and numerical predictions regarding scalar variance decay in a pipe have revealed that the traditional plug-flow reactor picture of pipe flow omits key physical mechanisms. In particular, the far-field decay exhibits a power law rather than exponential decay. These observations are examined by performing a set of experiments where the manner in which the scalar constituents are introduced into the pipe is varied. Significant differences are noted in the behavior of the variance decay until the very far field is reached, where an invariant power-law form emerges.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430804
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  • 99
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    Explicit algebraic scalar-flux models for turbulent reacting flows (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1935-1946 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Explicit algebraic scalar-flux models that are valid for three-dimensional turbulent flows are derived from a hierarchy of second-order moment closures. The mathematical procedure is based on the Cayley-Hamilton theorem and is an extension of the scheme developed by Taulbee. Several closures for the pressure-scalar gradient correlations are considered and explicit algebraic relations are provided for the velocity-scalar correlations in both nonreacting and reacting flows. In the latter, the role of the Damköhler number is exhibited in isothermal turbulent flows with nonpremixed reactants. The relationship between these closures and traditional models based on the linear gradientdiffusion approximation is theoretically established. The results of model predictions are assessed by comparison with available laboratory data in turbulent jet flows.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430803
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  • 100
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    Drag coefficient and velocity of rise of a single collasping two-phase bubble (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1955-1963 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The velocity of rise and the drag of a single vapor bubble collapsing in another immiscible liquid were measured experimentally. During the process of collapse, the dispersed-phase vapor bubble was transformed to a two-phase bubble with condensate accumulating at the rear of the two-phase bubble and vapor at its top. Such a configuration of a two-phse bubble is commonly known as a drobble. Experimental data for the six pairs of liquids covered a range of drobble (two-phase bubble) Reynolds numbers from 0.003 to 3,000. Two regimes of drobble movement were encountered. In the first regime (Re 〈 100), the drobble maintained its sphericity, and the observed drag was less than the solid-sphere drag predicted by the established solid sphere or Hadamard et al. fluid-sphere drag models. In the second regime, the drobble was deformed and oscillated; the observed drag departed suddenly from predictions of spherical models and increased with increasing Reynolds numbers. The critical Reynolds number covered a range from 100 to 1,000. Empirical models for drobble velocity and drag coefficient are derived.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430805
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