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  • 1985-1989  (9,268)
  • Chemical Engineering  (3,542)
  • Organic Chemistry  (3,492)
  • Computational Chemistry and Molecular Modeling  (1,638)
  • Life Sciences (general)  (596)
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  • 101
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Benzyl cations, free of counter ions, have been generated from the nuclear decay of tritium atoms contained exclusively in the side-chain of multi-labelled toluene and allowed to react in competition experiments with benzene and toluene. The aromatic substitution was studied in both the gaseous and liquid phase, employing pure aromatics or aromatics dissolved in n-hexane, carbon tetrachloride and nitromethane as the reaction medium. In the gaseous systems, at 20 Torr total pressure, High meta substitution of toluene indicates extensive isomerization of the excited intermediates, while the increase of the kT/kB value in the Presence of NH3 suggests that selective transalkylation competes with proton transfer to ammonia from the benzyl cation adducts with benzene, but not with toluene. High positional and low substrate selectivities were measured in solution, the decrease in kT/kB (from 2·8 to 1·7) in the different solvents being accompanied by an increase in the o/2p ratio. Competition experiments between benzene and methanol indicate that the reaction is not diffusion controlled. The influence of the reaction medium on the substrate selectivity is explained by postulating the formation of a cation-solvent adduct, where the solvent molecule undergoes displacement by the substrate. Positional selectivity would be controlled in a subsequent step.
    Additional Material: 1 Tab.
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  • 102
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The basic hydrolysis of 2,4-dinitrochlorobenzene (DNCB) and 2,4-dinitrofluorobenzene (DNFB) was studied in the presence of β-cyclodextrin (CDOH) and in the presence of hydroxy-functionalized micelles containing either a primary hydroxy group [hexadecyl-2-hydroxyethyldimethylammonium bromide (CHEDAB)] or a secondary hydroxy group [headecyl-2-hydroxypropyldimethylammonium bromide (CHPDAB) and 2-hydroxyhexadecyltrimethylammonium bromide (2-OHCTAB)].In all systems a biphasic reaction was observed. The first phase consisted of a competition between the additive (either micelle or cyclodextrin) and hydroxide ion for the aromatic substrate, and the second phase consisted of the hydrolysis of the trapped aryl micellar or cyclodextryl ether.The percentage of trapping of the aromatic substrate by the cyclodextrin was similar to that found for reactions in the hydroxy-functionalized micelles (CHPDAB and 2-OHCTAB) which contained secondary hydroxy groups. The relative rates of reaction for DNFB and for DNCB, i.e. F/Cl rate ratios, in the presence of CDOH were similar to those obtained in the presence of 2-OHCTAB but less than that obtained in the presence of CHEDAB. These results support the assumption that in CDOH the secondary hydroxy groups of C-2 or C-3 are involved in covalent bond formation with the aromatic substrate rather than the primary hydroxy group of C-6. All the reactions studied proceed much more slowly in the presence of CDOH than in the presence of the hydroxy-functionalized micelles. This may reflect a catalytic effect of the positively charged surface present in the micelles but not in the cyclodextrin.
    Additional Material: 3 Ill.
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  • 103
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Using the solvatochromic indicator method, a scale of solvent hydrogen-bond basicity, β1 (General), has been set up using a series of double regression equations, \documentclass{article}\pagestyle{empty}\begin{document}$$ \nu = \nu _0 + s\pi _1^* + b\beta _1 $$\end{document} for 11 aniline-type indicators. A similar solvent scale, β1 (Special), has been constructed by the homomorphic comparison method using only results by Laurence et al. on the indicators 4-nitroaniline and 4-nitro-N,N-dimethylaniline. Results are available from our previous work on a general solute scale, β2H, and we have also obtained a special solute scale, β2 (pKHB) from available log K values for hydrogen-bond complexation of bases with 4-fluorophenol in CCl4. However, the two solute β2 scales are virtually identical.It is shown that there is a general connection between β1(General) and β2H, with r = 0·9775 and s.d. = 0·05 for 32 compounds, and between β1(Special) and β2H, with r = 0·9776 and s.d. = 0·06 for the same 32 compounds. The latter correlation over 60 compounds yields r = 0·9684 and s.d. = 0·07. However, there are so many compounds in these regressions for which the differences in the solvent and solute β values are larger than the total expected error of 0·07 units that the use of β1 to predict β2 or vice versa is a very hazardous procedure. About 70 new β1 values obtained by the double regression method are also reported.
    Additional Material: 6 Tab.
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  • 104
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 573-579 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The MM2 force field has been extended so that calculations may be carried out on siloxanes. The parameters chosen give a good fit to available experimental data.
    Additional Material: 2 Tab.
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  • 105
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 602-610 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In order to assist in the interpretation of the D5h molecular structure of [45] (1,2,3,4,5)ferrocenophane (1) obtained from x-ray crystallographic analysis, a hypothetical hydrocarbon C30H40 (2) was derived from 1 by removing the iron atom and subjected to geometry optimization by molecular mechanics. A stable D5 conformer was found for 2, which has a g+ g- g+ helical bridge conformation and a ring-ring distance almost identical with that in 1 and ferrocene itself. Optimization of a perhydrogenated hydrocarbon model gave a highly strained C1 structure.
    Additional Material: 2 Ill.
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  • 106
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 623-630 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photolysis of dichlorodiphenylmethane in glassy 2-methyltetrahydrofuran at 77 K results in the formation of diphenylcarbene and the diphenylchloromethyl radical, which were detected by their fluorescence emission and excitation spectra. The relative yields of the carbene and biradical are shown to vary dramatically as a function of photolysis time. The photolability of the diphenylchloromethyl radical is also demonstrated. These results were interpreted in terms of a two-step mechanism, in which the diphenylchloromethyl radical is an intermediate in the formation of diphenylcarbene.
    Additional Material: 2 Ill.
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  • 107
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The formation of a σ-like complex by reaction between 1,3,5-trinitrobenzene and 1,8-diazabicyclo [5.4.0]-undec-7-ene was investigated in toluene at various temperatures. The kinetic data showed autocatalytic behaviour. Inspection of the reaction mixtures at zero reaction time indicated the presence of an equilibrium preceding the attack of the nucleophile, affording a molecular complex (substrate-nucleophile) which is responsible for the observed kinetic features. The present and the previous data led to the conclusion that the catalytic behaviours usually observed in SNAr reactions (in apolar solvents with amines as nucleophiles) are better explained by the presence of substrate-catalyst interactions than by catalysis on departure of the proton and leaving group from the zwitterionic intermediate.
    Additional Material: 3 Tab.
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  • 108
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989) 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 109
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The ups and downs, and reasons therein, of the π-complex theory of the mechanism of the benzidine rearrangements, and the possible role of π-complexes in a newer understanding of the rearrangements, are described.
    Additional Material: 3 Tab.
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  • 110
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 531-539 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Acid-catalysed condensation of resorcinol with aromatic aldehydes results in 2,8,14,20-tetrasubstitued calix[4] areneoctols. Sixteen compounds of this type containing different aromatic substituents were synthesized. The ring closure step, under the conditions of the reaction, is a reversible process. Four configurations are possible for every constitution, viz. cccc, cctt, ccct and ctct, but only cccc and cctt were formed in detectable amounts. In seven cases the thermodynamically more stable cccc isomers (1a-5a, 7a, 8a) and also the kinetically controlled cctt isomers (1b-5b, 7b, 8b) could be isolated. The configurations of the compounds were assigned by temperature-dependent 1H NMR analysis. The conformational motions of the macrocyclic ring permit only the cccc isomers to show coalescence for the signals of the aromatic Hb protons. The coalescence temperature was determined for isomers 1a (ΔG384≠ = 83·5 kJmol-1) and 3a (ΔG369≠ = 83·7 kJ mol-1). For steric reasons the ‘chair-chair’ conformers B and the ‘quasi-boat-chair’ conformers F are favoured. 1H and 13C NMR shifts show that compounds 1a-5a and 1b-5b have a quasi-axial arrangement of the aromatic substituents, whereas 6-9 have a quasi-equatorial arrangement of the substituents.
    Additional Material: 5 Ill.
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  • 111
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: IR spectroscopy is presented as a convenient means to monitor the formation of acyl (and alkyl) cations from corresponding acid chlorides, with Lewis acids at low temperature in the solid state. Phenylacetyl chloride is co-deposited (under vacuum at -173°C with antimony pentafluoride on a KBr window), as in the ‘molecular beam’ method of cation generation. The initial IR spectrum of the deposition shows (in addition to starting materials) that a small amount of phenylacetyl cation (2274 cm-1) has been formed. Warming the solid matrix to -123°C Promotes the smooth conversion of acid chloride to acyl cation. Ultraviolet irradiation (through quartz windows) at -123°C to -73°C facilitates this conversion but does not result in the loss of carbon monoxide from the acyl cation to form benzyl cation. When benzyl chloride is used in place of phenylacetyl chloride, there is no noticeable difference between IR spectra taken before and after warming and/or photolysis of the solid deposition.
    Additional Material: 1 Ill.
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  • 112
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 214-224 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The solvolysis of 21 different 3- or 17-androstanyl tosylates or chlorides with halogen, hydroxy or oxo substituents in 17- or 3-position shows rate constant variations in hexafluoro isopropanol of up to 6·3 with regular differences for epimeric substituents. Similar variations ae seen over a distance of ∼10 Å in 13C-NMR shifts at C-17-ones of androstan-17-ones with varied halogen substituents in C-3, whereas the shielding observed at other distant carbon atoms excludes significant through bond effects. It is shown how, on the basis of suitable Coulomb-type equations and of force field minimized geometries, both the stability variation of carbocationic transition states and the carbonyl group polarization are predictable by linear electric field effects, using the same parametrization.
    Additional Material: 1 Ill.
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  • 113
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 263-270 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Reactivity of dialkyl 2-(dimethylamino)ethyl phosphates, (RO)2P(O)OCH2CH2NMe2 (R = Me, PhCH2) was studied in aqueous solutions. Depending on the initial substrate's concentration, reaction can involve the unimolecular fragmentation to N,N-dimethylaziridinium dialkylphosphate, or the bimolecular isomerization to the zwitterionic derivative. The latter reaction proceeds via two consecutive SN2 steps and involves the formation of two ionic intermediates which were synthesized independently and allowed to react to give the zwitterionic product. Rate constants for the isomerization of the dimethyl ester (R = Me), as well as rate constant for the reaction between the corresponding intermediates have been determined, and the reactivity of the dimethyl ester has been compared with that of the dibenzyl derivative.
    Additional Material: 1 Ill.
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  • 114
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystal and molecular structures of dimesitylketene (1) and bis(3,5-dibromo-2,4,6-trimethylphenyl)ketene (2), the first free ketenes to be studied by X-ray diffraction, have been determined. The molecules of 1 and 2 have crystallographic C1 and C2 symmetry, respectively, and exist in a propeller conformation. Molecular mechanics calculations of 1 and 2 using a modification of Allinger's new allene parameters reproduce satisfactorily the structural parameters of the ketenes. The torsional angles of the aryl rings in 1 and 2 are similar (ca. 50°) and are regarded as ‘intrinsic’ values for a 1,1-dimesitylvinyl propeller. From the similarity in aryl torsional angles in 1 and 2 it is concluded that the buttressing effects in 2 (if any) are not markedly manifested in the structural parameters of 2.
    Additional Material: 2 Ill.
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  • 115
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 323-330 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photoreactions of Cr(CO)5(Im) (Im = 1,3-dimethyl-4-imidazolin-2-ylidene) have been investigated by laser flash and continuous photolysis. Quantum yields for the disappearance of Cr(CO)5(Im) in benzene under Ar or CO were very low, although transients observed by laser flash photolysis reacted rapidly with CO. This suggests that photodissociation of the carbene ligand is very minor. The laser flash photolysis at 337 nm in benzene (B) gave a transient (λmax = 630 nm), which converted to the second transient (λmax = 455 nm) within ∼100 ns. The kinetic studies of these transients revealed that the first one is a ‘free’ coordinatively unsaturated species (Cr(CO)4(Im)) and the second one carries a solvent molecule as a ligand (Cr(CO)4(Im)(B)). From the comparison of Cr(CO)4(Im) and Cr(CO)5, apparently lower reactivity of Cr(CO)5 was found to be due to the strong coordination of a solvent molecule. The Im ligand neutralizes the deficit of electron density on Cr. A simple synthesis of Cr(CO)5(Im) was also described.
    Additional Material: 3 Ill.
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  • 116
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 359-362 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction pathway of urea formation by selenium-catalysed carbonylation of secondary amines with carbon monoxide in the presence of oxygen was studied using piperidine as a secondary amine. It was established that selenium reacts with carbon monoxide and piperidine to give carbamoselenoate as an intermediate, which affords biscarbamoyl diselenide by the oxidation with molecular oxygen. Aminolysis of biscarbamoyl diselenide gives the urea derivative, accompanying the regeneration of selenium catalyst.
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  • 117
    Electronic Resource
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 377-382 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rates of N-methylation of pyridine and its ring-substituted derivatives by trimethyl phosphate were measured in D2O and in CDCl3. Relative rates, together with the solvent activity coefficients of substrates for the transfer form chloroform to water, were used for determining the solvent activity coefficients of the activated complexes for this SN2 reaction. The results indicate early activated complexes for all pyridines, with the most nucleophilic substrate showing the most reactant-like activated complex.
    Additional Material: 2 Tab.
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  • 118
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 389-409 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A gas-phase experimental investigation of the competition between carbon and oxygen alkylation of a series of cyclic and acyclic enolate ions is described. Perfluoropropylene is shown to react in a characteristic way with oxyanions and carbanions to produce distinctive ionic products. The relative yields of these products formed in reactions with ambident enolate ions provides a measure of their intrinsic carbon vs. oxygen regioselectivity. The results for a series of enolates derived from aldehydes, ketones, esters, amides and related compounds show a wide range of reactivity which is a function of the nature of the central substituent. Most aldehyde and ketone enolates react mainly through oxygen, while enolates with σ-acceptor of π-donor type central substituents react mainly thorugh carbon. Ring-size in cyclic ketone enolates also influences C vs. O regioselectivity, i.e. small-ring enolates react mainly through carbon, while larger ring enolates (C7-C9) react preferentially through oxygen. The enolate reactivity patterns can be generally accounted for by the keto-enol energy differences for the parent carbonyl compounds, although some exceptions are evident. The origins of the highly variable, kinetically determined regioselectivities are discussed.
    Additional Material: 5 Tab.
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  • 119
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 417-424 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two organometallic reagents, butyllithium in heptane solution and dibutylmercury in the gas phase, have been studied by means of core electron spectroscopy. The property of particular interest was the charge polarization as reflected by the ESCA shifts. In the butyllithium compound the C1s binding energy is shifted to a lower value by 1·8 eV for C-1 (situated closest to the Li+ ion) relative to the heptane solvent carbon. This is due to the anionic character of the C-1. The interpretation of the experiments was supported by comparing the results with ab initio calculations made on geometry-optimized butyllithium, butyl anion and butane.
    Additional Material: 3 Ill.
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  • 120
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 455-466 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Mixtures of bicyclo[3.2.0]hept-2-ene and bicyclo[2.2.1]hept-2-ene, with one isomer labeled with two deuterium atoms, were isomerized in the gas phase at 276 °C. By following the concentration ratios of d0 and d2 versions of bicyclo[2.2.1]hept-2-ene as functions of time one finds that the partitioning of bicyclo[3.2.0]hept-2-ene between the primary products bicyclo[2.2.1]hept-2-ene and cyclopentadiene plus ethene is 2:1. This and earlier stereochemical results permit the calculation of the partitioning of the [3.2.0] olefin between the orbital symmetry allowed [1,3] carbon shift-with-inversion product and several forbidden or non-concerted reaction channels (approximately 1:1) and the stereochemistry of the ethene d2 formed from exo,exo-[6,7-2H2]bicyclo[3.2.0]hept-2-ene directly (1:1 E: Z).
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  • 121
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    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 875-876 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 122
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 123
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 877-877 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 124
    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
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  • 125
    Electronic Resource
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 877-877 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 126
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 908-922 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Erosion in bubbling fluidized-bed combustors is a serious issue that may affect their reliability and economics. Available evidence suggests that the key to understanding this erosion is detailed knowledge of the coupled and complex phenomena of solids circulation and bubble motion. A thin transparent “two-dimensional” rectangular fluidized bed with an obstacle served as a rough model for a fluidized-bed combustor. This model was studied experimentally and computationally using two hydrodynamic equation sets. The computed hydrodynamic results agree reasonably well with experimental data. Bubble frequencies and sizes compare well with those obtained from analyzing a high-speed motion picture frame-by-frame. Time-averaged porosities computed from both models agree with time-averaged porosity distributions measured with a gamma-ray densitometer. The principal diferences between the data and the computations in this paper are due to asymmetries present in the experiment and to the simplified solids rheology used in the hydrodynamic models.
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  • 127
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 959-966 
    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 approach is developed for applying ideal and real adsorbed solution theory models to the description of multicomponent adsorption equilibria at fixed pressure. This allows ignoring single-component behavior in the Henry's law region, P → O, but introduces new parameters that must be evaluated from binary equilibrium data. Comparisons with various sets of experimental data show that the new approach gives results as good as the classical one, but without requiring knowledge of the single component behavior in the Henry's law region; more over, it removes the sensitivity to the type of model adopted in fitting single-component equilibrium data.
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  • 128
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 988-994 
    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 extent of high temperature (900-1,300°C), short time (〈1 s) SO2 capture was found to be limited by temperature-dependent losses in the porosity of calcium based sorbents. At 970°C these porosity losses were caused by CO2-activated sintering. Sulfation of the sorbents either prevented or reduced the extent of porosity losses. Differences in SO2 capture between hydroxides from different commercial sources, and significantly lower levels of capture by calcium carbonates compared to hydroxides were attributed to differences in particle size and the degree of porosity loss.
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  • 129
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1017-1028 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Systems having transfer functions of the form \documentclass{article}\pagestyle{empty}\begin{document}$$ G_P (s) = \frac{{P_1 (s) - P_2 (s)e^{ - t_d s} }}{{Q(s)}}, $$\end{document} where P1(s), P2(s) and Q(s) are polynomials, are called quasirational distributed systems (QRDS). They are encountered in processes modeled by hyperbolic partial differential equations. QRDS can have an infinity of right half-plane zeros which causes large phase lags and can result in poor performance of the closed-loop system with PID controllers. Theory on the asymptotic location of zeros of quasipolynomials is used to predict the nonminimum phase characteristics of QRDS and formulas are presented for factoring QRDS models into minimum and non-minimum phase elements.A generalized Smith predictor controller design procedure for QRDS, based on this factorization, is derived. It uses pole placement to obtain a controller parameterization that introduces free poles which are selected to satisfy robustness specifications. The use of pole placement allows for the design of robust control systems in a transparent manner. Controller selection is generally better, simpler and more direct with this procedure than searching for optimal PID controller settings.
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    AIChE Journal 35 (1989), S. 1049-1052 
    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.
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  • 131
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    AIChE Journal 35 (1989), S. 1053-1053 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 132
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    AIChE Journal 35 (1989), S. 1097-1106 
    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 sorption of toluene, dilute in CO2, and likewise the distribution coefficient of toluene between silicone rubber and CO2 have been explored from gaseous to supercritical fluid conditions. Sorption and desorption isotherms were determined by frontal analysis using a new inverse supercritical fluid chromatography technique at 35 and 70°C up to 250 bar. Complementary swelling data are presented for pure CO2 in silicone rubber up to 315 bar. A new result is that the sorption of toluene goes through a maximum and is highly adjustable over a continuum in the highly compressible region of carbon dioxide. This behavior is explained physically and predicted quantitatively with the Flory equation and the Peng-Robinson equation of state using only information from binary systems. These results are useful for a wide variety of applications including impregnation of polymers with pharmaceuticals, fragrances and other additives, and polymer purification.
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  • 133
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    AIChE Journal 35 (1989), S. 1137-1147 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Detailed mathematical models, pore or grain based, describing diffusion, reaction, and pore structure evolution in pellets of porous solids are used to simulate, along with a macroscopic reactor design model, the transient phenomena that take place during desulfurization of coal gas in fixed-bed reactors of pellets of metal oxide sorbents. Our computer simulation results show that the form of the pore- or grain-size distribution strongly influences the predictions of the overall reactor design model.
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  • 134
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    AIChE Journal 35 (1989), S. 1186-1194 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Vapors of alkali metal compounds can be removed from coal combustion and gasification flue gases using high-temperature aluminosilicate sorbents. The fundamentals of alkali adsorption on kaolinite, bauxite, and emathlite are compared and analyzed both experimentally and through theoretical modeling. The results show that the process is not a simple physical condensation, but a complex combination of diffusion and reaction. The kinetics of adsorption on these sorbents have similarities: the process is diffusion-influenced, the rate decreases with time, and there is a final saturation limit. There are, however, differences in reaction mechanisms leading to potentially different applications for each sorbent. In adsorbing alkali chloride vapors, kaolinite and emathlite release all the chlorine back to the gas phase while bauxite retains some of the chlorine. Moreover, the products of reaction with emathlite have a melting point significantly lower than those for kaolinite and bauxite. Therefore, emathlite is more suitable for lower-temperature sorption systems downstream of the combustors/gasifiers, while kaolinite and bauxite are suitable as in-situ additives.
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  • 135
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    AIChE Journal 35 (1989), S. 1203-1206 
    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.
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  • 136
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    AIChE Journal 35 (1989), S. 1210-1210 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 137
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    AIChE Journal 35 (1989), S. 1211-1214 
    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.
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  • 138
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    AIChE Journal 35 (1989), S. 1245-1252 
    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 rates of reduction of hematite to magnetite and of magnetite to iron in hydrogen / nitrogen / water vapor atmospheres were each studied with respect to variation in temperature, gas composition, and solid pore structure. It is shown that at temperatures below 350°C, the reactions are under chemical kinetic control, and diffusional limitations are negligible. The activation energies for the reduction of hematite to magnetite and of magnetite to iron were found to be 185 kJ / mol and 76.6 k J / mol, respectively. Both reactions exhibit first-order behavior for hydrogen partial pressures less than 76 kPa. The conversion and rate data for each reaction were interpreted in terms of the random pore model of Bhatia and Perlmutter (1980), which takes into account the detailed pore structure of the starting material as well as the changes that occur as the reaction proceeds. The model predictions of conversion with time agree with the measured data to within 2%, and the rate vs. conversion predictions agree to within 5%.
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  • 139
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    AIChE Journal 35 (1989), S. 1282-1292 
    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 macroscopic model based on the volume-averaged equations of motion is presented for countercurrent gas-liquid flow in a packed bed. The model yields a column-limited flooding point as the loss of existence of uniform states. It correctly predicts the existence of two uniform states below the flooding point. The lower branch corresponds to the trends commonly observed experimentally. It is shown that the upper branch is made unattainable by the gas distributor/support plate at the bottom of the column. The occurrence of premature flooding induced by the support plate is also explained. It is suggested that the occurrence of spontaneous liquid segregation, necessitating frequent liquid redistribution in columns with large dumped packings and porosities, is a consequence of the loss of stability of the uniform state in the lower branch.
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  • 140
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    AIChE Journal 35 (1989), S. 1337-1345 
    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 recent model of partial internal wetting of catalyst particles (Bhatia, 1988) is extended to allow for pore-size distribution, multicomponent diffusion, and nonlinear kinetics for spherical particles exposed to condensible vapor undergoing an exothermic reaction. Profiles of liqid filling of the pores are computed, and the influence on mass transfer and effectiveness factor is determined. Under certain circumstances, the effectiveness factor has a maximum with respect to the mole fraction of condensible component suggesting an optimum vapor-phase composition. As the bulk vapor approaches saturation the effectiveness factor and particle temperature can drop sharply because of precipitious increase in liquid filling. However, a significant fraction of the pore space is still dry in contradiction to prior models assuming complete internal wetting of catalyst particles. The new model is more realistic than earlier attempts and lays the framework for proper representation of the physical phenomena involved.
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  • 141
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    AIChE Journal 35 (1989), S. 1346-1350 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Andritsos and Hanratty (1978b) have shown that the increase in interfacial drag caused by waves in stratified gas-liquid flows is related to the wave steepness. Recent analyses of finite amplitude Kelvin-Helmholtz waves are used to develop a correlation for the ratio of the wave height to wavelength.
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  • 142
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    AIChE Journal 35 (1989), S. 1328-1336 
    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 solid circulation in the annular region of a 0.146 and a 0.292 m ID semicylindrical and cylindrical air spouted beds was investigated for different spouting conditions. Stroboscopic photography, stopwatch and fiber optic methods were used to measure the vertical particle velocities in the annular region. The optical fiber probe enabled the measurement of particle velocities inside the dense annular phase and was validated at the walls. Velocity profiles in half beds were very different from those found in full beds. The work was then limited to full beds. Experimental results show that the solids flow is characterized by a point sink at the nozzle entrance with the solids moving almost in plug flow higher in the bed. There is negligible entrainment of solids along the spout wall and slow, thin wall layers are observed near the walls and spout. The velocity profiles are independent of the total height of the bed. A kinematic model successfully describes the observed velocity field.
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  • 143
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    AIChE Journal 35 (1989), S. 1370-1375 
    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.
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  • 144
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    AIChE Journal 35 (1989), S. 1398-1398 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 145
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    AIChE Journal 35 (1989) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 146
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    AIChE Journal 35 (1989), S. 1437-1444 
    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 of periodic water flow on SO2 oxidation in a trickle bed of activated carbon catalyst was investigated, whereby gaseous reactants were introduced into the trickle-bed reactor continuously, but water was turned on and off. Mean liquid superficial velocities of 0.86 and 1.65 mm/s were used. At the latter, an increase in the oxidation rate of about 30 to 45% was found within a range of cycle periods from 2 to 80 min. A temperature change of up to 7°C was observed in the bed during periodic operation. An explanation of the improved average oxidation rate under periodic operation is developed in terms of the steady-state rates with and without water flow for symmetrical and asymmetrical cycles.
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  • 147
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    AIChE Journal 35 (1989), S. 1509-1520 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Differences in the dispersion and/or catalytic pellet size between laboratory and commercial reactors, operating at the same average residence time, may lead to differences in the yield of a desired product. Bounds are developed for predicting the maximal design uncertainty introduced by these phenomena for a network consisting of an arbitrary number of irreversible first-order reactions. A major advantage of these bounds is that they do not require any knowledge of the rate constants. It is shown that in a packed-bed reactor, the fractional yield loss is smaller than: \documentclass{article}\pagestyle{empty}\begin{document}$$ 0.5{\rm }(m - 1){\rm }\left[{\sigma _\theta ^{\rm 2} + \left({1.2 + \frac{2}{{Bi_m }}} \right)p^2 } \right] $$\end{document} where m - 1 is the number of reaction steps involved in converting a reactant to the desired product, σθ2 is the dimensionless variance of the residence time density function, Bim is the Biot number, p2 = [(Vp/Sx)2(1/Deτ)], and τ is the average residence time.
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  • 148
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    AIChE Journal 35 (1989), S. 1521-1526 
    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 purpose of this study is to observe the dynamic wetting process of a slide coater flow (Ca = 0.16; Re = 14.4; St = 0.0142; ΔeP = 2.5), using a specially-developed Laser-Doppler measuring technique.The measurements, carried out with glycerol solutions, reveal that the observed contact line is apparent and that a thin air film is entrained between the web and the liquid surface. The liquid is accelerated along the lower free surface and attains approximately 50% of the web velocity at the apparent contact line. Downstream from the apparent contact line, the liquid is further accelerated along the air film to the web velocity at the real contact line.The apparent contact angle increases with the capillary number Ca and air entrainment occurs at Ca = 0.25.
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  • 149
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    AIChE Journal 35 (1989), S. 1551-1554 
    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.
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  • 150
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    AIChE Journal 35 (1989), S. 1564-1568 
    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.
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  • 151
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    AIChE Journal 35 (1989), S. 1582-1582 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 152
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    AIChE Journal 35 (1989), S. 1602-1616 
    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 for synthesizing feedforward/state feedback controllers for a broad class of SISO nonlinear systems with measurable disturbances is presented. Depending on the structural characteristics of the system, the control law can be static or dynamic. The closed-loop system is independent of the measurable disturbances and linear with respect to set point changes. The performance of the proposed control scheme is illustrated through an example of composition control in a system of three CSTR's in series.
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  • 153
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    AIChE Journal 35 (1989), S. 1639-1650 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Steel bars in reinforced concrete are protected from corrosion by the high pH environment of the surrounding concrete. This alkaline environment is destroyed by the reaction of atmospheric CO2 with the Ca(OH)2 of the concrete mass. When this process, called carbonation of concrete, reaches the reinforcing bars, corrosion of the latter may commence. In this paper, the physiochemical processes in this phenomenon are presented and modeled mathematically. The mathematical model is fairly complex, but certain simplifying assumptions are possible, which lead to the formation of a “carbonation front” and to a simple analytical expression for the evolution in time of this front, in terms of the composition parameters of cement and concrete and of the environmental conditions. This simple expression is in very good agreement with experimental results obtained in this and in previous studies. The effect of some parameters on the carbonation front propagation is also discussed.
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  • 154
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    AIChE Journal 35 (1989), S. 1667-1677 
    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 study was made of the effect of design and operating parameters on the regeneration of a fixed bed of activated carbon. Two adsorbed species were removed by a hot gas purge, making the study relevant to thermal swing cycles used commercially. The analysis utilized direct experimental results as well as simulated results using a model described earlier by the authors (Huang and Fair, 1988).Regeneration parameters studied were: type of purge gas, purge gas contact time and velocity, regeneration temperature, initial bed loading, and bed pressure. These were related to certain parameters influencing the adsorption step: type of carrier gas, feed concentration, contact time and velocity, pressure, and initial bed temperature. The results are summarized in the form of guidelines for optimal regeneration cycle specification.
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  • 155
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    AIChE Journal 35 (1989), S. 1710-1718 
    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 one-dimensional isothermal transient two-phase flow model of gas and liquid in a low-permeability medium has been developed from the general mass and momentum balances.The characteristic roots of the governing differential equations are real and distinct. Therefore, solution of the flow equations may be attempted by a stable initial-value finite-difference scheme. A numerical solution was obtained using the method of lines.Calculated two-phase flow parameters are consistent with expected flow behavior and reflect the sensitivity of fluid flow to porosity, gas and liquid permeability, and capillary pressure in a tight sands porous medium. Calculated gas flow rates compared well with experimental data obtained at the Institute of Gas Technology (IGT) for low-permeability sandstone.
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  • 156
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    AIChE Journal 35 (1989), S. 1739-1741 
    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.
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    AIChE Journal 35 (1989), S. 1756-1756 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    AIChE Journal 35 (1989), S. 1770-1778 
    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 work has shown that in a standard stirred tank, the three-dimensional velocity field in the discharge flow of the stirrer is characterized by a strong deviation from homogeneous isotropic turbulence. By means of a two-component laser Doppler velocimeter (2D-LDV), the \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {v'_r v'_\theta} $\end{document} Reynolds stresses are measured in a 6.3-dm3 standard tank stirred by a six-flat-blade Rushton turbine. Obviously, these stresses must be known to better understand the turbulent mixing in such a configuration. Moreover, the 2D-LDV appears to be an efficient tool for characterizing, from an energy viewpoint, the type of agitator used and, in principle, is confirmed to be useful to accurately obtain the length scales of turbulence which are fundamental parameters for the study of the micromixing processes.
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    AIChE Journal 35 (1989), S. 1813-1820 
    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 generalized algorithm has been developed for solving simultaneous chemical and phase equilibrium equations of two-phase systems. By rearranging convergence loops of the algorithm of Sanderson and Chien (1973), this new approach shows improved robustness and speed. Solutions to the material balance and chemical equilibrium equations are obtained with an improved Marquardt method (Zhan, 1976). An esterification reaction and dissociation reactions of electrolytes in phase equilibrium are presented as examples.
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  • 160
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    AIChE Journal 35 (1989), S. 1845-1855 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Continuous-phase backmixing coefficients have been determined by continuous tracer injection for pulsed-plate extraction columns of 72-, 152- and 300-mm-diameter. Both single-phase water and two-phase kerosene-water were studied in all three columns, together with four other solvent-water systems in the smallest column; in all cases, water was the continuous phase. Evidence of maldistribution of the phases was obtained in the largest column. The backmixing coefficient was found to increase with column diameter in single-phase operation, but was diameter-independent in the two-phase case. Alternative correlations of the data were based on dimensional analysis and on a physical model, respectively. The influence of different systems was accounted for in the latter in terms of droplet size and terminal velocity, dispersed phase holdup, and density difference. Qualitative color tracer tests on the dispersed phase gave no evidence of backmixing of this phase, although strong forward dispersion was observed in the emulsion regime.
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  • 161
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    AIChE Journal 35 (1989), S. 1883-1893 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Partition coefficients are computed for hard spherical solutes in equilibrium with sponge-type matrices containing randomly-placed spherical cavities or pores using grand canonical Monte Carlo simulation. The random pore model is representative of a variety of disordered porous solids including porous glasses and some polymeric materials. The algorithm used brings additional realism to the problem by rigorously distinguishing between accessible and inaccessible pore space. The simulation results display significant concentration effects which are often observed experimentally and are compared to data obtained by Brannon and Anderson (1982) for the partitioning of bovine serum albumin into controlled-pore glass.
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    AIChE Journal 35 (1989), S. 1899-1902 
    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.
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    AIChE Journal 35 (1989) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 164
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    AIChE Journal 35 (1989), S. 1933-1941 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many industrial proceses require the circulation of particles between reacting fluidized compartments at a stable, but flexible rate, so that the processes can be operated at different solids rates. In order to understand the phenomena involved in the circulation and its control, circulation of sand particles has been studied through a new experimental approach, using an open-loop two compartment circulating system.Experimental results show that the control of the circulation rate depends on three phenomena: the vertical resisting force in the fluidized compartments, the contraction of flow in the communication zone, and the bypass of gas between the compartments. For industrial purposes, the first appears to be predominant in the control of the solids rate. The second ensures neither the strict control of this rate nor the required flexibility. The link between the gas bypass and the circulation phenomena is explained and recommendations for the design and operation of circulating systems are given.
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  • 165
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    AIChE Journal 35 (1989), S. 1975-1979 
    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 model is developed describing consecutive gas-solid reactions occurring in porous media. The model calls for independently measurable parameters and predicts two maxima in the reaction rate at intermediate conversions. The low temperature (350°C) reduction of hematite to iron in a hydrogen-nitrogen atmosphere was used to test the model. The experimental data confirmed the expected rate maxima. The conversion predictions are very close to the data for conversions below 30%, but are systematically somewhat lower than the experimental values for higher levels of conversion. An explanation for the discrepancy is offered in terms of the description of the pore structure.
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  • 166
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    AIChE Journal 35 (1989), S. 2013-2027 
    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 this paper, a simple procedure based on fast and slow reaction asymptotics has been employed to derive first-order closure models for the nonlinear reaction terms in turbulent mass balances from mechanistic models of turbulent mixing and reaction. The coalescence-redispersion (CRD) model, the interaction by exchange with the mean (IEM) model, the three-environment (3E) model, and the four-environment (4E) model have been used to develop closure equations. The closure models have been tested extensively against experimental data for both single and multiple reactions. The closures based on slow asymptotics for the CRD, 3E and 4E models provide very good predictions of all of the experimental data, while other models available either in the literature or derived here are not adequate. The simple new closure equations developed in this paper may be useful in modeling systems involving turbulent mixing and complex chemical reactions.
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  • 167
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    AIChE Journal 35 (1989), S. 2058-2060 
    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.
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  • 168
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    AIChE Journal 35 (1989), S. 1052-1052 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 169
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    AIChE Journal 35 (1989), S. 1535-1542 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many industrially important processes feature both nonlinear system dynamics and a process deadtime. Powerful deadtime compensation methods, such as the Smith predictor structure in state space for linear systems is presented first and then directly extended to nonlinear systems. When combined with input/output linearizing state feedback, this Smith-like predictor makes a nonlinear system with deadtime behave like a linear system with deadtime. The control structure is completed by adding an external linear controller, which provides integral action and compensates for the deadtime in the input/output linear system, and an open-loop state observer. Conditions for robust stability with respect to errors in the deadtime and more general linear unstructured multiplicative uncertainties are given. Computer simulations for an example system demonstrate the high controller performance that can be obtained using the proposed method.
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  • 170
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    AIChE Journal 35 (1989), S. 1543-1546 
    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.
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  • 171
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    AIChE Journal 35 (1989), S. 1376-1379 
    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.
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  • 172
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    AIChE Journal 35 (1989), S. 1617-1624 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ultrapyrolysis or ultrarapid pyrolysis is a hydrocarbon thermal cracking process which offers the promise of greater product selectivity, higher yield and feedstock flexibility. In this paper, ultrapyrolysis of propane in a spouted bed with a draft tube was used as a test system to demonstrate these advantages. Experiments, carried out on a 20-cm-diameter pilot-scale reactor, illustrate the spouted bed to be capable of achieving the extremely high reactant heating rates of up to 105 K/s and the short gas residence times of less than 500 ms necessary for this process. Moreover, reactant conversion and product yields can be enhanced by controlling the operating temperature of the bed. In addition, application of the propane pryolysis reaction scheme of Sundaram and Froment into a recently developed computer model indicates the ability to correctly simulate the spouted bed as an ultrapyrolysis reactor.
    Additional Material: 7 Ill.
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  • 173
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    AIChE Journal 35 (1989), S. 1651-1658 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper focuses on the problem of scale-up of two-phase (e.g., solid-fluid) reactors. It outlines a class of such reactors which, for first-order reactions, scale in the familiar single-phase manner via an analog of the usual residence time distribution formula. The differences lie in the fact that the appropriate tracer experiment entering the formalism for this reactor class refers to a nonadsorbing tracer, and the analog of the plug flow solution is the solution for a fixed bed with fluid-phase plug flow. Surprisingly, unlike single-phase systems, there exist two-phase reactors, outside of the class defined, that do not scale in this manner, even when, say, the true catalyst surface chemistry is purely first-order. The paper discusses a few examples and implications for the design of two-phase reactors, including fluidized beds.
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  • 174
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    AIChE Journal 35 (1989), S. 1685-1691 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Heat transfer coefficients were measured for ciculating beds of sand particles of mean size 222 to 299 μm at temperatures of 340-880° C. Transfer coefficients were obtained for both a 1.22-m-long, 12.7-mm-OD vertical tube and a 1.59-m-long, 148-mm-wide membrane wall near the top of a 152-mm-square by 7.32-m-tall combustion column. For both surfaces and all temperatures, average heat transfer coefficients increased almost linearly with local suspension density which ranged from 0 to 70 kg/m3. Radiation played a significant role, especially at high temperatures and low suspension densities. Heat transfer coefficients also varied significantly with the lateral position of the tube. The vertical length of heat transfer surface is shown to be an important parameter allowing seemingly discrepant published results to be reconciled.
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  • 175
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    AIChE Journal 35 (1989), S. 1719-1727 
    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 approximate equation for the evolution of finite-amplitude, long disturbances to Newtonian liquid films is found to be accurate over a wide range of Reynolds numbers. A long-wave expansion leads to a film profile equation asymptotically correct when wave number and Reynolds number are small. Solutions of the film profile equation are compared to exact and other approximate solutions of the Navier-Stokes system. An alternative form of the film profile equation results in remarkably accurate solutions, when Reynolds numbers are moderate, in the cases of standing or monotonically decaying waves in horizonatal films, rising film flow, final acceleration of a moving film, and film flow emerging from a slot coater.
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  • 176
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    AIChE Journal 35 (1989), S. 1742-1744 
    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.
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  • 177
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    AIChE Journal 35 (1989), S. 1753-1756 
    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.
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  • 178
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    AIChE Journal 35 (1989), S. 1592-1601 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Various strategies for sequencing heterogeneous azeotropic distillations have been explored. The design and optimization of these systems by simulation-based methods is generally acknowledged to be a very difficult problem (Kingsley and Lucia, 1988). In this article, a simple and accurate design and optimization procedure has been developed. The method does not involve any recycle convergence loops and has been applied successfully to several test problems. Unlike the simulation-based methods, our method is robust to changes in the system optimization variables (e.g., reflux ratio in the azeotropic column).In order to demonstrate the method, we present design and optimization results for the dehydration of ethanol using a benzene entrainer. Our optimal designs consume significantly less energy than state-of-the-art designs reported in the literature.
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  • 179
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    AIChE Journal 35 (1989), S. 1625-1630 
    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 final properties and end use of many organic solids often depends on their crystal-size distribution (CSD), e.g., bioavailability for pharmaceutical solids. The objective of this study was to develop an alternate technology for crystallizing and manipulating size distribution of organic solids by crystallization from supercritical fluids. Such a technology might be superior to conventional-size manipulation techniques, such as milling and recrystallization from organic solvents, which might contaminate the products and affect their physical-chemical stability. Supercritical carbon dioxide was used as solvent to dissolve and then crystallize benzoic acid. A batch crystallizer was constructed and operated in the supercritical region. Seeded and unseeded crystallization experiments were performed. Different depressurization vs. time profiles for the supercritical fluid were used to produce crystals of various sizes.
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  • 180
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    AIChE Journal 35 (1989), S. 1962-1974 
    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 computer simulation of turbulent flow in a channel is used to detect flow patterns related to the production of Reynolds stress. It is found that quadrant 2 and quadrant 4 events possess a streaky structure in the viscous wall region and that these events can be best understood by examining the velocity field in the y-z plane. Large turbulence production in the viscous wall region is found to occur in updrafts and downdrafts associated with closed eddies. These eddies, on average, have a spanwise dimension of 50 wall units and a streamwise dimension of 400-450 wall units. They are often seen to originate from small attached eddies at the wall.
    Additional Material: 18 Ill.
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  • 181
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    AIChE Journal 35 (1989), S. 1993-2002 
    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 ability of knowledge-based expert systems to facilitate the automation of difficult problems in process engineering that require symbolic reasoning and an efficient manipulation of diverse knowledge has generated considerable interest recently. Rapid deployment of these systems, however, has been difficult because of the tedious nature of knowledge acquisition, the inability of the system to learn or dynamically improve its performance, and the unpredictability of the system outside its domain of expertise.This paper proposes a neural-network-based methodology for providing a potential solution to the preceding problems in the area of process fault diagnosis. The potential of this approach is demonstrated with the aid of an oil refinery case study of the fluidized catalytic cracking process. The neural-network-based system successfully diagnoses the faults it is trained upon. It is able to generalize its knowledge to successfully diagnose novel fault combinations it is not explicitly trained upon. Furthermore, the network can also handle incomplete and uncertain data. In addition, this approach is compared with the knowledge-based approach.
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  • 182
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    AIChE Journal 35 (1989), S. 2037-2039 
    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.
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  • 183
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    AIChE Journal 35 (1989), S. 1895-1898 
    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.
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  • 184
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    AIChE Journal 35 (1989), S. 2029-2032 
    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.
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  • 185
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    AIChE Journal 35 (1989) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 186
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    AIChE Journal 35 (1989), S. 923-930 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents an efficient method for the design of controllers for integrating and runaway processes. The method is based on model matching in the frequency domain. The presence of open-loop instability as well as pure time delay in the process models make the design task challenging for these classes of processes.The goal is to achieve low-order, easily implementable cascade controllers in a unity-output-feedback configuration. It is shown that the central problem is in the selection of appropriate reference models. Several key constraints are developed which relate a given process model to a class of reference models for achieving total stability. Typical design examples are presented to clearly illustrate the various mathematical techniques.
    Additional Material: 6 Ill.
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  • 187
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    AIChE Journal 35 (1989), S. 951-958 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Models are developed for isothermal desorption in a fixed bed of adsorbent particles. While more general models require numerical solution of the governing equations, two practically important cases have analytical solutions: (1) an equilibrium desorption model where the rate of desorption is controlled by external and intraparticle mass transfer; and (2) a kinetic model where external and intraparticle mass transfer and a first-order irreversible desorption step control the overall process.Recent experimental data (Tan and Liou, 1988) for the desorption of ethyl acetate from activated carbon with supercritical carbon dioxide are found to fit the local-equilibrium model. Data for the effect of temperature on fractions desorbed indicate a reversal of the temperature dependence of the adsorption isotherm as the supercritical pressure is increased. This phenomenon is analogous to the observed cross-over region for the effect of temperature on the solubility of a solid at supercritical conditions.
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  • 188
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    AIChE Journal 35 (1989), S. 995-1002 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental data on silicon nitride film growth have been obtained from a radial-flow, plasma-enhanced chemical vapor deposition reactor. A nonisothermal mathematical model has been developed consisting of Navier-Stokes, energy, and species balance equations taking into account the temperature dependence of physical properties. The model is predictive at various power input levels for film compositions and growth rates.
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  • 189
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    AIChE Journal 35 (1989), S. 1039-1043 
    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.
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  • 190
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    AIChE Journal 35 (1989), S. 1057-1072 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We have developed an analytical solution which describes mineral zonation caused by diffusion in permeable media. For a semiinfinite domain, the species conservation equations transform into ordinary differential equations that yield a closed-form solution. The solution exhibits shock dissolution/precipitation fronts and gradual (nonshock) precipitation fronts. The solution can exhibit regions (gaps) containing no reactive solids which separate moving dissolution and precipitation fronts. The analysis is, in principle, extendable to include intraaqueous reactions, although the mathematics quickly becomes intractable.Numerical simulation exhibits all of the features of the more restricted analytical solution and is in good agreement with the data on hydroxyapatite dissolution taken by Kim and Cussler (1987).
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  • 191
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    AIChE Journal 35 (1989), S. 1107-1114 
    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 extent of diffusion limitations in the catalytic conversion of synthesis gas to hydrocarbons by the Fischer-Tropsch reaction has been established for a number of iron- and cobalt-based catalysts. The studies were performed in a fixed-bed microreactor system at temperatures in the range 473-523 K. Variation of catalyst particle size in the range 0.2-2.6 mm shows that the conversion of synthesis gas decreases considerably when the average particle size is increased. The effects of variation of particle size and pore diameter have been quantified with the Thiele model for diffusion limitations. Evidence has accumulated that the limited mobility of reactant molecules in the liquid-filled pores of Fischer-Tropsch catalysts is the main cause of retardation of the reaction rates. The experimentally determined reaction rates with various catalysts operated under different conditions show an excellent fit with the theoretical model.
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  • 192
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    AIChE Journal 35 (1989), S. 1148-1156 
    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 transient temperature excursions may be caused by a sudden reduction in the feed temperature to a packed-bed reactor operating at an intermediate conversion. When a unique steady state exists for all feed temperatures, the magnitude of the wrong-way behavior predicted by a two-phase model is very close to that predicted by a pseudohomogeneous model if PeH is equal to the dimensionless heat transfer coefficient H. The two-phase model enables a more efficient numerical simulation in such cases. The predictions of these two models may be rather different when steady-state multiplicity exists for some feed temperatures. In such cases, a two-phase model, which accounts for the axial dispersion of heat, should be used to simulate the transient behavior. The wrong-way behavior may lead to an ignition of a low-temperature state or an upstream propagation of a transient temperature wave.
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  • 193
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    AIChE Journal 35 (1989), S. 1195-1198 
    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.
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  • 194
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    AIChE Journal 35 (1989), S. 1219-1223 
    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: 7 Ill.
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  • 195
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    AIChE Journal 35 (1989) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 196
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    AIChE Journal 35 (1989), S. 1263-1270 
    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 the ratio of the drop radius to the distance separating any two drops and the relative importance of gravitational to surface forces are both small, the small amplitude oscillations of a drop of one viscous fluid immersed in another fluid are governed by the nonlinear dispersion relation derived by Miller and Scriven (1968). The dispersion relation has been solved numerically to determine the character of oscillations for arbitrary values of drop size, physical properties of the two fluids, and interfacial tension. The new theoretical results determine the range of validity of the low-viscosity approximation of Miller and Scriven, and are also shown to be essential for proper interpretation of many previously reported experimental results. New experimental measurements of natural frequencies of oscillation of water drops falling in 2-ethyl-1-hexanol, a system having properties characteristic of many others in solvent extraction, agree well with the theoretical predictions when drop radius is smaller than a critical size. The frequencies of oscillations of larger drops are better described by the dispersion relation due to Subramanyam (1969), which accounts for the relative motion of the two phases.
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    AIChE Journal 35 (1989), S. 1304-1314 
    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 laser-Doppler velocimeter (LDV) was used in a cold-flow study of a simulated entrained-flow coal gasifier. The study was designed to provide fundamental information about the flows in such a gasifier and to provide data for the validation of a turbulence submodel used in modeling combustion processes. Measurements in 20 swirling and nonswirling flow cases were made with several levels of replication. This study emphasized the effects of inlet conditions on flow properties within the simulated reactor.Unsteady flow phenomena with time scales on the order of seconds to minutes were sometimes observed. The unsteadiness was apparently associated with relaminarization-type flow transitions.Comparisons were made with model predictions from PCGC-2, a model for combustion processes based on the k,  -  ∊ turbulence model. Several areas of weakness in the model results were observed, but the unusual flow regimes measured in this study may be beyond the abilities of practical computer models.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 198
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1569-1571 
    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
    Library Location Call Number Volume/Issue/Year Availability
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  • 199
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989) 
    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
    Library Location Call Number Volume/Issue/Year Availability
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  • 200
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1391-1394 
    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
    Library Location Call Number Volume/Issue/Year Availability
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