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  • 101
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 387-391 
    ISSN: 0268-2605
    Keywords: colloidal manganese ; ESR ; susceptibility ; antiferromagnetism ; superparamagnetism ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reduction of MnBr2·2THF (THF = tetrahydrofuran) using K[BEt3H] yields the organosol [Mn·0.3THF]x. According to the UV/Vis, ESR (electron spin resonance spectroscopy), HRTEM (high-resolution transmission electron microscopy), XPS (X-ray photoelectron spectroscopy) and XAS (X-ray absorption spectroscopy) data, this nanosized metal colloid consists of small THF-stabilized Mn0 particles which show, in susceptibility investigations, a diminished magnetic coupling as deduced from the Weiss temperature, Θ = 96 K. The Neél temperature TN is likewise strongly reduced in comparison with the bulk value (95 K). The THF-stabilized Mn0 particles exhibit superparamagnetism below 20 K, with a partial blocking at 10 K, and to our knowledge represent the first colloid consisting of particles of an elemental antiferromagnetic metal. © 1998 John Wiley & Sons, Ltd.
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  • 102
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 435-438 
    ISSN: 0268-2605
    Keywords: tributyltin ; radiolabelling ; 113Sn ; synthesis ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method of synthesis of tributyl[113Sn]tin,­(n/C4H9)3113Sn(IV), from commercially avail-­able inorganic 113Sn(IV) is presented. Inorganic tin is first extracted in diethyl ether and reacted with C4H9MgCl to produce tetrabutyltin, (C4H9)4113Sn, which is then debutylated with HgCl2. The resulting tributyl[113Sn]tin chloride is isolated from the reaction mixture by successive extractions with hexane and aqueous Na2S2O3. The yield is 40-60% and the product obtained is 〉98% pure. It has the same specific activity as the starting 113Sn(IV), i.e. up to 550 MBq mg-1 Sn, making it suitable for use in environmental fate and toxicology studies at concentrations relevant of those found in the aquatic environment. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
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  • 103
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 439-447 
    ISSN: 0268-2605
    Keywords: high-performance liquid chromatography ; hydride generation ; atomic fluorescence spectrometry ; photo-oxidation ; arsenic speciation ; human urine ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potential of coupling anion-exchange high-performance liquid chromatography, hydride generation and atomic fluorescence spectrometry (HPLC-HG-AFS) for arsenic speciation is considered. The effects of hydrochloric acid and sodium tetrahydroborate concentrations on signal-to-background ratio, as well as argon and hydrogen flow rates, were investigated. Detection limits for arsenite, dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and arsenate were 0.17, 0.45, 0.30 and 0.38 μg l-1, respectively, using a 20-μl loop. Linearity ranges were 0.1-500 ng for As(III) and MMA (as arsenic), and 0.1-800 ng for DMA and As(V) (as arsenic). Arsenobetaine (AsB) was also determined by introducing an on-line photo-oxidation step after the chromatographic separation. In this case the limits of detection and linear ranges for the different species studied were similar to the values obtained previously for As(V). The technique was tested with a human urine reference material and a volunteer's sample. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
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  • 104
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 449-455 
    ISSN: 0268-2605
    Keywords: trimethylantimony ; biomethylation ; anaerobic bacteria ; inorganic antimony ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The volatile antimony compound trimethylantimony (TMA) was detected in headspace gases over anaerobic soil enrichment cultures spiked with potassium antimony tartrate. The presence of TMA was variable (12 positives from 104 cultures) and dependent upon both the inoculum source (environmental sample) and enrichment culture conditions. Positives for TMA formation were obtained with variable frequency for four of the six soils tested and for three types of enrichment culture, designed to encourage growth of nitrate-reducing, methane-producing or fermentative bacteria. The identity of the volatile antimony compound produced in each of the three types of enrichment culture was confirmed by gas chromatography-mass spectrometry and gas chromatography-atomic absorption spectroscopy. There was no evidence of any other volatile antimony compound in the headspace gases. These data suggest that the capability to generate TMA is widely distributed in the terrestrial environment and is attributable to different metabolic types of micro-organisms. © 1998 John Wiley & Sons, Ltd.
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  • 105
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 521-521 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 106
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 879-879 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
    Type of Medium: Electronic Resource
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  • 107
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
    Type of Medium: Electronic Resource
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  • 108
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 880-880 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
    Type of Medium: Electronic Resource
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  • 109
    ISSN: 0268-2605
    Keywords: platinum compound antileukaemic ; cytotoxic ; DNA ; thiosemicarbazone ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: p-Isopropylbenzaldehyde thiosemicarbazone (p-is.TSCN) (1) reacts with [Pt(µ-Cl)(η3-C4H7)]2 to form a dinuclear [Pt(µ-Cl)(p-is.TSCN)]2 complex (2) and a cyclometallated cluster [Pt(p-is.TSCN)]4 (3). Biological testing of these complexes against HL-60 and U-937 human leukemic cells suggest that complexes 2 and 3 may be endowed with important cytotoxic activity properties since they exhibit IC50 values (50% inhibition of cell growth) in the micromolar range, as does the clinically used drug cisplatin (cis-DDP). Analysis of the interaction of compounds 2 and 3 with DNA indicates that the kinetics of DNA platination due to compounds 2 and 3 is faster than that of cisplatin and that after 24 h of incubation most of the platinum centers are bound to DNA. Thus, it is likely that the cytotoxic activity displayed by compounds 2 and 3 may be correlated with their high level of DNA platination. Copyright © 1998 John Wiley & Sons, Ltd.
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  • 110
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 815-818 
    ISSN: 0268-2605
    Keywords: desilylation ; hydroxyquinones t-butyldimethylsilyl ethers ; potassium fluoride ; tetra-n-butylammonium fluoride ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Desilylation of a series of hydrolytically stable hydroxyquinone t-butyldimethylsilyl ethers was achieved in high yields by the use of potassium fluoride in the presence of catalytic amounts of aqueous 48% hydrobromic acid (HBr), or basic aluminium oxide (Al2O3), and tetra-n-butylammonium fluoride (Bu4NF) as cleaving agents. Copyright © 1998 John Wiley & Sons, Ltd.
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  • 111
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 881-882 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
    Type of Medium: Electronic Resource
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  • 112
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 882-883 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
    Type of Medium: Electronic Resource
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  • 113
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 613-620 
    ISSN: 0268-2605
    Keywords: manganese oxides ; montmorillonite ; kaolinite ; mercury(II) ; methylation ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of freshwater sediment components such as kaolinite, montmorillonite and birnessite (δ-MnO2) on the biomethylation of mercury(II) in a synthetic growth medium (M-IIY) were assessed. Additions of kaolinite or montmorillonite to media containing mercuriC nitrate [Hg(NO3)2; 12 μg Hg ml-1] had no significant effect on either bacterial growth or the production of methylmercury (CH3Hg+). However, whereas the addition of birnessite resulted in only a small (ca 4%) increase in bacterial growth, it also produced a significant decrease (ca 50%) in the production of CH3Hg+. Further, it was demonstrated that, with the exception of kaolinite, adsorption of mercury(II) onto the sediment components before they were added to the M-IIY medium decreased its bioavailability, i.e., the amounts of CH3Hg+ produced from the adsorbed mercury(II) were significantly lower than those produced from equivalent concentrations of Hg(NO3)2 in the absence of the mineral colloids. In the case of montmorillonite, CH3Hg+ production was decreased by 21% relative to the control system. Most striking was the case of birnessite, in which no CH3Hg+ was detected after a 25 h incubation period and only very small quantities of CH3Hg+ (3-7 ng l-1) were present in the medium after 336 h. These data demonstrate that mineral colloids common in freshwater sediments significantly influence the extent of biomethylation of mercury(II) adsorbed on their surfaces. Birnessite, in particular, is a very effective inhibitor of the biomethylation of surface-bound mercury(II). Therefore, it may be possible to reduce the severity of mercury pollution in some aquatic environments by adding a reactive manganese oxide, such as birnessite, to the system and thereby to inhibit the transformation (methylation) of inorganic mercury(II) into the much more toxic CH3Hg+ species. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
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  • 114
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 621-634 
    ISSN: 0268-2605
    Keywords: quality ; phenytins ; mussel ; Certified Reference Material ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organotin contamination of the marine environment can be considered one of the main environmental problems in the last 20 years. Starting from the ‘Arcachon case’, monitoring campaigns have been carried out worldwide in order to evaluate the concentration levels of these compounds in the marine environment. In 1987 the EC Standards, Measurements and Testing Programme (formerly BCR) started a ‘tin speciation’ project to assess and improve the quality of measurements in this field and to make available reference materials. Ten years of study within the framework of this project have produced results in the fields of method development and production of reference materials, particularly for butyltins. The quality of the phenyltin analytical results was lower than for butyltins and further efforts are still needed. To overcome this shortfall, the last certification campaign was aimed towards the certification of phenyltins, as well as butyltins, in a candidate mussel certified Reference Material. The results of the homogeneity and stability tests for phenyltins and of the certification campaign are presented here. The preparation of the material and the analytical methods used in the certification campaigns are also described. The certification of phenyltins was hindered by their lack of long-term stability; nevertheless, the exercise provided information about the state-of-the-art of phenyltin measurements in biological samples. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
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  • 115
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 695-705 
    ISSN: 0268-2605
    Keywords: poly(silylenemethylene) ; polycarbo-­silane ; silicon carbide ; precursor ; polysilaethy-­lene ; disilacyclobutane ; pyrolysis ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Work carried in the authors laboratory on Si-CH2-Si bridged polycarbosilanes is reviewed. In pursuit of high-yield polymeric precursors to silicon carbide, convenient synthetic routes to both linear and hyperbranched polycarbosilanes having a ‘[SiH2CH2]n’ compositional formula have been developed. The linear [SiH2CH2]n polymer was prepared by ring-opening polymerization of a substituted disilacyclobutane, and was studied both as an analogue of polyethylene and as a high-yield precursor to SiC. Elaboration of the methods employed to prepare this polymer has yielded a wide range of new poly(silylenemethylene)s (PSMs) of the type [SiRR′CH2]n, where R and R′ can be a wide range of different groups, including a series of symmetrically disubstituted polymers with R = R′ = F, alkyl and alkoxy which form crystalline solid phases and various amorphous, atactic polymers having different R and R′ groups. By using (Si)-Cl replacement reactions analogous to those developed previously for polydichlorophosphazene, as well as hydrosilation reactions similar to those used for [Si(H)(Me)O]n, a series of side-chain polymers having various groups attached to Si through Si-C or Si-O bonded linkages were obtained. Similar polymer modification reactions have recently been developed for the branched oligomer/polymer analogue of these linear polycarbosilanes, leading to hyperbranched species with functional substituents, including a di(ethyleneoxy) methyl ether-terminated derivative which readily dissolves lithium salts. The results of studies of these novel ‘inorganic/organic’ hybrid polycarbosilanes are described and their properties are compared with those of related carbon-backbone and siloxane polymers. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 1 Tab.
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  • 116
    ISSN: 0268-2605
    Keywords: precursor ; ceramic ; thermolysis ; silicon ; carbodi-imide ; boron ; hydroboration ; plastic forming ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis, by two different reaction pathways, of boron-modified polysilylcarbodi-imides of general type {B[C2H4Si(R)NCN]3}n (R =­singly bonded organic ligand) and the plastic-forming and the thermal behavior of these polymers are described. Compounds {B[C2H4Si(R)NCN]3}n [2a, R = H; 2b, R = CH3; 2c, R = (NCN)0.5] can be obtained by treatment of the vinyl-substituted polysilylcarbodi-imides [(H2C=CH)(R)SiNCN]n [1a, R = H; 1b, R = CH3; 1c, R = (NCN)0.5] with borane dimethylsulfide BH3·S(CH3)2. The polysilylcarbodi-imides 1a-1c themselves are accessible via the reaction of vinyl-substituted chlorosilanes (H2C=CH)-­(R)SiCl2 with cyanamide H2N-C≡N in the presence of pyridine or by a non-oxide sol-gel process of vinylated chlorosilanes and bis(trimethylsilyl)carbodi-imide, (H3C)3SiN=C=NSi(CH3)3. In the second method for the synthesis of 2a-2c, hydroboration of vinyl-substituted chlorosilanes (H2C=CH)(R)SiCl2 with borane dimethylsulfide, borane trimethylamide or borane triethylamide to yield the tris[(chlorosilyl)ethyl]boranes B[C2H4Si(R)Cl2]3 (3a, R = H; 3b, R = CH3; 3c, R = Cl) is followed by treatment of the as-obtained compounds with bis(trimethylsilyl)carbodi-imide, which results in the formation of the hydroborated polysilylcarbodi-imides 2a-2c. The thermogravimetric behavior of the polymers 1a-1c and 2a-2c up to 2300°C is reported. It is shown that boron-modified polysilylcarbodi-imides are suitable precursors for the preparation of dense bulk ceramics. Therefore, the preparation of green bodies of the hydroborated polysilylcarbodi-imides 2a-2c by plastic forming (PF) is described. A series of experiments points to the fact that the microstructure of the as-obtained ceramic monoliths obtained by subsequent thermolysis of the plastic-formed green bodies is strongly influenced by the conditions during plastic forming. © 1998 John Wiley & Sons, Ltd.
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  • 117
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 715-723 
    ISSN: 0268-2605
    Keywords: Cubic Silsesquioxanes ; interface ; materials ; hybrids ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cubic silsesquioxanes, [RSiO1.5]x, potentially offer access to organic/inorganic hybrids wherein the exact shape, size and mechanical properties of the inorganic component are perfectly defined. Furthermore, by tailoring the organic functionality bound to silicon, the inorganic/organic interface can also be perfectly defined. Finally, careful selection of the polymerizable groups in the organic moieties can provide good-to-excellent control of the crosslinked density or degree of polymerization of the resulting hybrid materials. Thus, cubic silsesquioxanes may be exceptional model materials for inorganic/organic hybrids. Methods of synthesizing cubes with liquid-crystalline and/or polymerizable organic moieties are described. Some thermal properties are discussed. The catalytic copolymerization of the octavinyldimethylsiloxy-functionalized cube with the octahydridodimethyl-­siloxy-functionalized cube to produce a material with well-defined microporosity and high surface area is described. © 1998 John Wiley & Sons, Ltd.
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  • 118
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 675-680 
    ISSN: 0268-2605
    Keywords: polymer ; nanocomposites ; silicates ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polymer nanocomposites, especially polymer-layered silicate (PLS) nanocomposites, represent a radical alternative to conventionally (macroscopically) filled polymers. Because of their nanometer-size dispersion, the nanocomposites exhibit markedly improved properties when compared with the pure polymers or conventional composites. These include increased modulus and strength, decreased gas permeability, increased solvent and heat resistance and decreased flammability. In addition to their potential applications, PLS nanocomposites are also unique model systems to study the structure and dynamics of polymers in confined environments. Using both delaminated and intercalated hybrids, the statics and dynamics of polymers confined over distances ranging from the radius of gyration of the polymer to the statistical segment length of the chains can be studied. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
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  • 119
    ISSN: 0268-2605
    Keywords: magnetization reversal ; iron oxide particles ; SQUID ; atomic force microscopy ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report first measurements of the magnetization reversal of monodisperse 30 nm and 50 nm ferromagnetic Fe3O4 particles. These particles are produced in a carrier gas as an aerosol by spray pyrolysis. After production and size selection, they are precipitated on a silicon chip with a niobium SQUID (superconducting quantum interference device) incorporated on its surface. By changing a magnetic field in the plane of the SQUID, we can measure the magnetization reversal of the particles by the flux they induce into the SQUID. The angular dependence of this reversal is determined by rotating the magnetic field around the SQUID. Scanning electron microscope (SEM) images have confirmed the particle size and revealed the position of the collected particles. If the particle concentration is too high, we cannot detect changes in the magnetic moment of a single particle, but measure the magnetic properties of the whole assembly. If only a few particles are found on the SQUID loop the angular dependence of the magnetic reversal of a single particle can be measured; this result is compared with a simple model of magnetization reversal. © 1998 John Wiley & Sons, Ltd.
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  • 120
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    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 337-340 
    ISSN: 0268-2605
    Keywords: porous silicon ; luminescence ; light-assisted etching ; atomic force microscopy ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present an investigation into a new technique for producing luminescent porous silicon with controlled lateral microstructure. The process is based on the effect of laser-assisted stain etching of silicon with hydrofluoric acid solution. With the further goal of preparing two-dimensional periodical arrays of luminescent microdots, we studied the accuracy of the technique by etching single submillimetre structures with a low-power laser. The size and exact position of the etched area are controlled by laser focusing and movement, respectively, with submillimetre accuracy. Samples exhibit orange luminescence when illuminated with UV or blue light.We have studied the dependence of the efficiency of the luminescence, the structure and the rate of etching on parameters such as the HF concentration, the intensity and wavelength of illumination and the doping level of the silicon wafer. Optimization of the process parameters, and consistency with assumed mechanisms of luminescence and etching process, are discussed. © 1998 John Wiley & Sons, Ltd.
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  • 121
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 327-335 
    ISSN: 0268-2605
    Keywords: zinc sulphide ; precipitation ; nanocrystallites ; nanopores ; optical transmission spectroscopy ; vibrational spectroscopy ; Raman spectroscopy ; X-ray diffraction ; transmission electron microscopy ; thermogravimetric analysis ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: During the synthesis of ZnS powders by wet chemical precipitation, the formation of nanoporous spheres is observed. The powders have been investigated using thermogravimetric analysis, X-ray diffraction and optical spectroscopies. Nanopore formation can be explained by several stages of growth. The formation of nanoparticles as primary particles is followed by their agglomeration forming secondary particles. These secondary particles are monodispersed spheres with a considerable porosity, because the agglomeration of the nanoparticles is unlikely to be volume-filling. The voids or nanopores formed by this agglomeration process in the secondary particles is estimated to comprise around 35% of the sphere volume. They are mainly filled with water and the residues of the chemical reagents. Water in the pores partially reacts with ZnS and forms hydrated sulphates. The chemical reagents used for the precipitation reactions are also found to be bound to the nanocrystallite's surfaces as ligands in some cases. Depending on the reaction conditions and reagents, the agglomeration of the nanoparticles can also be modified or hindered by the use of complexing agents acting as a sterically stabilizing surface layer on the nanocrystallites. The agglomeration of nanoparticles to larger units being a general phenomenon, this use of complexing agents to control pore formation and agglomerate size should be applicable to other nanocrystalline systems. © 1998 John Wiley & Sons, Ltd.
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  • 122
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 353-360 
    ISSN: 0268-2605
    Keywords: surface chemistry ; sodium nanoclusters ; optical spectroscopy ; plasmon excitation ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of molecular adsorbate layers on surface plasmon excitation in small supported metal particles has been investigated and exploited to study adsorption reactions on their surfaces. For this purpose sodium nanoclusters on quartz and LiF substrates served as model systems. Their optical transmission spectra are dominated by two maxima which are due to the excitation of surface plasmon resonances in the direction of the long and short axes of the oblate particles. By recording the spectra under ultrahigh-vacuum conditions and, subsequently, after exposure to gases such as O2, N2O, CO2, H2 and N2, changes in the optical spectra can be identified if the clusters are covered by as little as half a molecular monolayer. Depending on the adsorbed molecules, different modifications of the maximum position, the width and the amplitude of the surface plasmon resonances are observed. The results of a series of measurements together with calculations using the quasi-static approximation indicate that the variations in the spectra allow one to distinguish between physisorption and chemisorption, i.e. to characterize the strength of the chemical bond. In addition, diffusion of the molecules into the bulk of the particles can be detected. Particularly interesting is the observation that the clusters can experience a change in their shape if gases such as O2 or CO2 react with their surface. © 1998 John Wiley & Sons, Ltd.
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  • 123
    ISSN: 0268-2605
    Keywords: alumina ; nanoporous membranes ; nanocomposites ; templates ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three different examples have shown that nanoporous alumina membranes serve as ideal templates for the formation of nanostructured materials and also as a support of those materials in composites. The unique properties of such membranes (transparency, chemical resistivity, thermal stability, adjustable pore sizes etc.) and the very simple mode of generating these composites are the benefits of using this inorganic template material.
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  • 124
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 303-303 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
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  • 125
    Electronic Resource
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 305-314 
    ISSN: 0268-2605
    Keywords: mesoporous ; oxides ; nanostructures ; luminescence ; zeolites ; guest/host ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ordered porous inorganic compounds can now be synthesized with pore sizes between 0.3 nm and several tens of nanometers. The sharp pore size distribution of such materials and the ordered pore arrangement open possibilities for using them to organize matter on the nanometer scale. This overview highlights different aspects of this topic, using four selected examples: the spatial organization of molecules with high molecular hyperpolarizability to create a frequency-doubling element; the encapsulation of a laser dye which results in a new class of solid-state lasers; the encapsulation of small metal clusters in mesoporous ordered oxides; and the encapsulation of semiconductor clusters in such oxides. © 1998 John Wiley & Sons, Ltd.
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  • 126
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    Applied Organometallic Chemistry 12 (1998), S. 401-408 
    ISSN: 0268-2605
    Keywords: Metallocene ; Ziegler-Natta ; Polypropylene ; α-Olefins ; Catalysis ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of propylene using a mixture of racemic metallocenes and Ziegler-Natta catalysts was investigated. The polypropylene was obtained as a mixture of a fine powder and beads, with the powder being absorbed partially on the beads. The relative amount of the powder can be controlled by the concentration of the metallocene. The compatibility between the components of the mixed catalytic systems and the effect of the components on the rate of polymerization and on the properties of the new polymers were studied. The metallocene system dramatically affects the melt viscosity, isotacticity and molecular weight of the polymers. The two catalytic systems are able to act jointly, producing different polymers, for which separate melting and crystallization temperatures are obtained. © 1998 John Wiley & Sons, Ltd.
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  • 127
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    Applied Organometallic Chemistry 12 (1998), S. 409-417 
    ISSN: 0268-2605
    Keywords: antitumor activity ; cancer cell lines ; dibutyltins ; NCI ; organotins ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper reports the activity of four dibutyltin(IV)-N-arylidene-α-amino acid complexes against the National Cancer Institute (NCI) panel of 60 cell lines. The results indicated that three of the organotin complexes (C17H25NO3Sn, C18H27NO3Sn and C20H31NO3Sn) exhibit their highest cytotoxic effect on the NCI-522 (non-small cell lung cancer) cell line. The fourth complex, C21H27NO3Sn, exhibits its highest cytotoxic activity on the cell line RXF-631L (renal cancer). In general, a low to moderate cellular response was observed for all the organotin complexes, with at least one cell line in each subpanel of cells exhibiting a very low growth inhibition response to all the organotin complexes. The low-responding cell lines included HOP-62 (non-small lung cancer), DLD-1 (colon cancer), SF-539 (CNS cancer), SK-MEL-5 (melanoma), IGROV-1 (ovarian cancer) and RPMI-8226 (leukemia). The results also indicated that the compounds did not exhibit any significant subpanel activity and suggested that the compounds were not active in all the cell lines contained in any subpanel. The low to moderate activity of these compounds across the cell lines was attributed to the presence of nitrogen-bearing ligands which prevented the dissociation of the compound and the subsequent binding to DNA. © 1998 John Wiley & Sons, Ltd.
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  • 128
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    Applied Organometallic Chemistry 12 (1998), S. 427-433 
    ISSN: 0268-2605
    Keywords: laser ; chemical vapour deposition ; thin films ; Si/C/H materials ; divinylsilane ; silicon carbide ; polycarbosilane ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transversely excited atmospheric (TEA) CO2 laser-induced decomposition of divinylsilane in the gas phase yields unsaturated C2-C4 hydrocarbons, benzene and vinylsilane, and it represents a convenient process for chemical vapour deposition of thin solid films composed of silicon carbide and polycarbosilane. © 1998 John Wiley & Sons, Ltd.
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  • 129
    ISSN: 0268-2605
    Keywords: iron ; clusters ; magnetic properties ; laser vaporization ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Clusters of iron produced in a laser vaporization source have been characterized with time-of-flight spectra and deposited on different substrates for production of films of varying thickness. The magnetic properties of these films with thicknesses of 60 and 120 nm were investigated using an alternating gradient magnetometer. The films exhibit mono-domain behavior from a broad size distribution which has been confirmed by transmission electron microscopy. Films were also investigated by Mössbauer spectroscopy, which showed fast relaxation in the particles at room temperature. © 1998 John Wiley & Sons, Ltd.
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  • 130
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    Applied Organometallic Chemistry 12 (1998), S. 485-489 
    ISSN: 0268-2605
    Keywords: polysulfone ; chelate-modified polysulfone ; DSC ; thermal stability ; X-ray ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chloro-terminated polysulfones with various molecular weights were chemically modified with bis(2,4-dihydroxybenzaldehyde)copper(II). The properties of modified polysulfones are compared with the unmodified ones, and an increase in glass transition temperatures, softening points and reduced viscosities of the former materials was observed. In addition, the chelate-modified polymers exhibited excellent thermal stability properties and semicrystalline patterns. Also, they provided transparent and flexible films. © 1998 John Wiley & Sons, Ltd.
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  • 131
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    Applied Organometallic Chemistry 12 (1998), S. 469-474 
    ISSN: 0268-2605
    Keywords: asymmetric catalysis ; diethylzinc ; alkylation ; chiral heterocyclic alcohols ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The asymmetric alkylation with diethylzinc of five heterocyclic aldehydes and benzaldehyde (for comparison) has been studied in the presence of two optically active amino alcohols: (S)-2-amino-1-butanol (AB) and (1S,2R)-N,N-dibutylnorephedrine (DBNE). A number of chiral (hetero)aromatic secondary alcohols were synthesized in high yields (95-98%) with enantioselectivity up to 92% enantiomeric excess (ee) in the presence of DBNE catalyst. Optically active thienyl and 4-pyridyl derivatives were prepared for the first time by catalytic asymmetric alkylation. The influence of the amount of DBNE on the enantioselectivity was investigated. In contrast to benzaldehyde, 2-furan- and 2-thiophene-carbaldehydes, in the case of 3- and 4-pyridinecarbaldehydes the ee values depend directly on the catalyst concentration. © 1998 John Wiley & Sons, Ltd.
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  • 132
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    Applied Organometallic Chemistry 12 (1998), S. 880-881 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
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  • 133
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    Applied Organometallic Chemistry 12 (1998), S. 819-825 
    ISSN: 0268-2605
    Keywords: monobutyltins ; dibutyltins ; tributyltins ; water ; sediment ; Osaka Bay ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The concentration of tributyltin (TBT) in surface water from Osaka Bay ranged from 0.023 to 0.061 µg l-1 in 1989 and from not detected (ND) to 0.059 µg l-1 in 1990 while the proportion of TBT as a percentage of the total butyltins (BTs) was more than 40%. The concentration of TBT was also surveyed in the Port of Osaka and the Yodo River basin. TBT levels were highest in the estuary (the Port of Osaka), followed by sea areas (Osaka Bay) and rivers (Yodo River basin). A fairly high correlation coefficient between TBT concentration and salinity in water from the estuary and the sea areas was observed. This result shows that the TBT in the estuary water is diluted by seawater. Generally, the TBT concentrations in the water columns were distributed uniformly and the composition of the BTs was also constant. TBT was detected in sediment from Osaka Bay in the range from ND to 0.023 mg kg-1 dry weight with a high ratio of monobutyltin (MBT) to the total BTs. TBT in sediment core was also measured; its concentration decreased with core depth. It was estimated from these measurements that the release of TBT into Osaka Bay began in the 1960s. Copyright © 1998 John Wiley & Sons, Ltd.
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  • 134
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    Applied Organometallic Chemistry 12 (1998), S. 881-881 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
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  • 135
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    Applied Organometallic Chemistry 12 (1998), S. 827-842 
    ISSN: 0268-2605
    Keywords: Scopulariopsis brevicaulis ; hydride generation ; antimony ; biomethylation ; biotransformation ; solid-phase extraction ; sudden infant death syndrome (SIDS) ; volatile antimony ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cultures of the fungus Scopulariopsis brevicaulis were grown in antimony-rich media. Although volatile compounds of other elements were readily detected in the culture headspace, volatile antimony compounds were formed irreproducibly and at only ultratrace levels. In order to monitor the media for nonvolatile methylantimony compounds, a method of sample preparation was developed, based on solid-phase extraction. This enabled the separation of large quantities of soluble inorganic antimony species from trace amounts of organoantimony compounds before speciation by HG-GC-AAS. By this methodology methylated antimony compounds were detected at concentrations of 0.8- 7.1 µg Sbl-1 in all media in which S. brevicaulis was grown in the presence of antimony(III) compounds. These methylantimony species were not detected in any of the nonliving or medium-only controls. Methylated compounds were not detected where S. brevicaulis was grown in the presence of antimony(V) compounds. This is the first study to show that antimony(III) compounds are biomethylated by S. brevicaulis under aerobic-only growth conditions. Copyright © 1998 John Wiley & Sons, Ltd.
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  • 136
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    Applied Organometallic Chemistry 12 (1998), S. 855-859 
    ISSN: 0268-2605
    Keywords: butyltin ; phenyltin ; gibberellates ; antitumour ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and characterization of di-n-butyl-, tri-n-butyl- and triphenyltin gibberellates are reported. Their antitumour activities in vitro against a panel of seven human tumour cell lines are given and compared with those of drugs used clinically. Copyright © 1998 John Wiley & Sons, Ltd.
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  • 137
    ISSN: 0268-2605
    Keywords: carbohydrate-modified phenylsiloxane ; surfactants ; wetting behaviour ; superspreading ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dynamic wetting behaviour on a perfluorinated, low-energy solid has been investigated for a carbohydrate-modified phenylsiloxane surfactant. The surfactant concentration, the rate of interface generation and the [solid/liquid interface area] : [liquid/vapour interface area] ratio were varied systematically. Dynamic data for the liquid/vapour (γlv) and solid/liquid (γsl) interfacial tension as well as their Lifshitz-van der Waals and donor-acceptor contributions were determined under strictly controlled conditions. Since γsl reacts sensitively to variations of the surfactant concentration and the rate of interface generation, the covering of the liquid/non-polar solid interface is assumed to be a spreading limiting factor. The corresponding γlv values remain constant and close to those obtained under equilibrium conditions. Copyright © 1998 John Wiley & Sons, Ltd.
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  • 138
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    Applied Organometallic Chemistry 12 (1998), S. 861-871 
    ISSN: 0268-2605
    Keywords: diorganotin ; Pyrimidine ; complex ; Mössbauer ; IR ; NMR ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complexes formed between the diorganotin(IV) moieties, R2Sn(IV), and the ligand 2-mercaptopyrimidine, (H)SPym, were investigated. Complexes R2SnHal(SPym) and R2Sn(SPym)2 [R = Me, iPr, nBu, iBu, tBu, cyclohexyl(Cy), Ph] were synthesized, and characterized by elemental analysis. In the solid state, chelation of SPym through S and N donors was established by IR spectroscopy, and the nature of the environment of tin centers was investigated by 119Sn Mössbauer spectroscopy. From the dynamics of 119Sn nuclei determined by variable-temperature measurements on representative compounds [Me2SnCl(SPym) and Cy2SnBr(SPym)], as well as by point-charge model treatment of nuclear quadrupole splitting parameters, it was inferred that Me2SnCl-­(SPym) may assume a trans-Me2 octahedral coordination geometry around tin in a monodimensional polymer, or a monomeric trigonal-bipyramidal structure (distorted). The latter type of structure was assigned to the other R2SnHal(SPym) species, while R2Sn(SPym)2 complexes assume a trans-octahedral, or skew trapezoidal, tin environment. In CHCl3-CDCl3 solutions, monomeric species occur (according to vapor-pressure osmometry), where 1H and 13C NMR spectroscopic parameters of SPym indicate the persistence of Sn chelation by S and N donor atoms. The Me2SnCl(SPym) species assume trigonal-bipyramidal structures with a chelating SPym ligand, in CDCl3 and C2H5OH solutions, according to the coupling constants 1J(119Sn,13C), as well as IR and 119Sn Mössbauer spectroscopic data. 119Sn NMR parameters fully correspond with data for the homologous complexes with 2-mercaptopyridine. Copyright © 1998 John Wiley & Sons, Ltd.
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  • 139
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    Applied Organometallic Chemistry 12 (1998), S. 541-549 
    ISSN: 0268-2605
    Keywords: organotin speciation ; analytical validation procedure ; organotin sediment extraction ; Grignard derivatization ; organotin extraction stability ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of several extraction variables such as acid concentration and strength (e.g. for HCl and HOAc), the presence of complexing agents (e.g. tropolone, sodium diethyldithiocarbamate) in the extracting mixture, solvent polarity (e.g. hexane, toluene) and sonication time for native butyl- and phenyl-tin compounds from sediment was evaluated. A toluene-HOAc mixture (10:4) yields the highest extraction efficiency for all the analytes and minimizes the degradation of trialkyl- and triaryl-tins during the extraction under sonication. In addition, losses of underivatized monobutyltin and monophenyltin were minimized in several steps of the analytical procedure. The analytical procedure developed was validated against existing CRMs for butyltin determination. © 1998 John Wiley & Sons, Ltd.
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  • 140
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    Applied Organometallic Chemistry 12 (1998), S. 559-563 
    ISSN: 0268-2605
    Keywords: tributyltin ; surface microlayer ; dynamic model ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transport dynamics of tributyltin (TBT) between the surface microlayer and subsurface water were studied in experimental systems which simulated different surface sea states. A dynamic model was derived from a diffusion equation to describe the dynamics of the TBT transport process. With this dynamic model diffusion coefficients were determined, and the effects of surface sea states and temperature on the TBT transport process between the surface microlayer and subsurface water were also studied. Turbulence, breaking waves and elevated temperature can accelerate this transport. © 1998 John Wiley & Sons, Ltd.
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  • 141
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    Applied Organometallic Chemistry 12 (1998), S. 635-641 
    ISSN: 0268-2605
    Keywords: arsenobetaine ; arsenocholine ; non-hygroscopic ; NMR ; FAB MS ; ICP MS ; synthesis ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Multigram quantities of arsenobetaine bromide and arsenocholine iodide were synthesized from trimethylarsine using uncomplicated techniques. Arsenobetaine bromide and arsenocholine iodide are both non-hygroscopic. Arsenocholine iodide is, however, light-sensitive and should be used with actinic glassware. Both compounds were characterized by elemental and spectroscopic techniques and found to be suitable for use as primary analytical standards. © 1998 John Wiley & Sons, Ltd.
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  • 142
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    Chemical Engineering & Technology - CET 20 (1997) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 143
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    Chemical Engineering & Technology - CET 20 (1997), S. 17-22 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mass transfer with chemical reaction by liquid/liquid phase tranfer catalysis (LLPTC) for an isothermal batch reactor was analyzed. The results for the phase transfer catalyzed reaction system can be generally described by a pseudo first-order hypothesis, whereas the reaction system can be controlled by simultaneous mass transfer of the catalysts between two liquid phases and chemical reaction in the organic phase. The mass transfer limitation is mainly from the mass transfer step of QX from the organic phase to the aqueous phase. The concept of catalyst-effectiveness vs. physically meaningful parameters in a liquid/liquid phase transfer catalyzed reaction is introduced. The catalyst effectiveness is increased as the mass transfer factors increase, the ratio of reaction rate coefficients of aqueous forward reaction to organic increases, and the equilibrium constant in the aqueous solution increases.
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  • 144
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    Chemical Engineering & Technology - CET 20 (1997), S. 40-42 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The use of ozone and hydrogen peroxide for the simultaneous oxidation of nitrogen and sulfur oxides was studied in experiments carried out in a stirred cell. It was found that in a gas mixture, containing both nitrogen and sulfur oxides, only the nitrogen oxides are oxidized by ozone. Contrary to earlier results, sulfur dioxide does not disturb the oxidation of nitrogen oxides under dry conditions. The consumption of ozone in the oxidation of nitric oxide was slightly below the stoichiometric level because the ozone was introduced into the reactor in the oxygen flow. When the molar ratio between ozone and nitric oxide was more than 0.4, some of the nitric oxide was oxidized to higher oxides of nitrogen, the final product being a solid mixture of N2O5 and (NO)2S2O7. Some nitrosyl sulfuric acid was formed in the aqueous solution of hydrogen peroxide in addition to sulfuric acid under wet conditions. Some white solid was found on the walls of the reactor. This solid is said it the literature to consist of H2SO4, HNOSO4 and (NO)2S2O7.
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  • 145
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    Chemical Engineering & Technology - CET 20 (1997) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and 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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    Chemical Engineering & Technology - CET 20 (1997), S. 85-89 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A comparative study of reported theoretical and experimental investigations evaluating the numbers and sizes of bubbles emerging from submerged orifices reveals that the lack of consistency can be attributed largely to faulty experimental techniques. Errors are attributed to an inadequate knowledge of the influence of the surface properties of the solid and liquid media on the emission process and to the lack of standardization of the equipment geometries especially regarding the pressure chambers and orifice plates. The analyses provide guidance to designing standardized equipment to produce reproducible bubbles.
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  • 147
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    Chemical Engineering & Technology - CET 20 (1997), S. 429-433 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When in contact with water, organoalkoxysilanes and other alkoxy metal compounds react to organofunctionalized polysiloxanes or heteropolysiloxanes. A new method for the continuous preparation of porous organopolysiloxane spheres was developed. Droplets of the precursor mixture are injected into the vertical reactor column. Movement of the gelating droplets is controlled by flow of the aqueous reaction medium. Advantages are adjustable residence time, minimized coalescence and low reactor height. An example shows typical product characteristics like narrow particle size distribution and macroporosity.
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  • 148
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    Chemical Engineering & Technology - CET 20 (1997), S. 533-537 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Airlift loop reactors are useful in many chemical and biotechnological processes where three phase reaction systems are required. One example is biological waste water treatment. In order to enhance biological reaction rates it is often useful to immobilize the bacteria on carrier particles. Knowledge of solid distribution and local gas holdup in those systems is important for calculation of mass and energy transfer or reaction kinetics. For this reason a method has been developed which enables to measure such local phase holdups. The measuring system consists of a time-domain-reflectometry (TDR)-instrument in combination with a pressure difference meter. The method has successfully been applied to determine local axial gas and solid distribution in internal airlift loop reactors, filled with a three phase system consisting of water, air, and polymer particles.
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  • 149
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    Chemical Engineering & Technology - CET 20 (1997), S. 538-549 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: New data of gas-liquid mass transfer for cocurrent downflow through packed beds of porous and non-porous particles are presented. Mass transfer parameters for air/carbon dioxide/water, air/carbon dioxide/carboxymethylcellulose solution and air/carbon dioxide/sodium hydroxide systems were evaluated by least square fit of the calculated CO2 concentration profiles in gas phase to the experimental values. The volumetric liquid-side mass transfer coefficient increases with the increase of the flow consistency index of the liquid. A comparison of the volumetric liquid-side mass transfer coefficient values evaluated with and without taking into account the axial dispersion shows that the influence of the liquid axial dispersion is significant at low liquid velocity and high CMC concentrations, and the influence of the gas axial dispersion is insignificant.
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  • 150
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    Chemical Engineering & Technology - CET 20 (1997), S. 342-347 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two types of solid adsorbents, activated carbon and zeolite 13X, were used at 80°C to remove sulfur compounds from naphtha solutions. Adsorption isotherms have been determined in a pressure vessel. This investigation indicated that activated carbon is superior to zeolite 13X at such high temperatures. A new formula based on the Langmuir model has been found to fit the experimental data satisfactorily. Comparison of the findings of this study with those of a previous one conducted at ambient temperatures in this department indicates that such treatment generally gives better results at low temperature where almost complete recovery of the sulfur compounds can be performed by using zeolite 13X.
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  • 151
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    Chemical Engineering & Technology - CET 20 (1997) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and 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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    Chemical Engineering & Technology - CET 20 (1997), S. 371-377 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fluctuation solution theory relates thermodynamics partial derivatives to integrals of molecular direct correlation functions from statistical mechanics. This paper describes an application of that theory for correlating and predicting solubilities of light gases in heavy n-paraffins. Two of the solvents are complex waxes. Equations from the theory represent the liquid phase, and additional hypothesis are adopted to build a model for the high pressure vapor-liquid equilibrium. In the correlation mode, the model, based in the fluctuation solution theory, produces a molar fraction of the gas in the liquid phase with an average absolute relative deviation under 3% in a large number of cases. In the prediction mode, when binary parameters are used, errors are on the order of 10%. Overall for n-paraffins solvents, the model presented in this paper shows a good capacity to correlate experimental solubility and an adequate power to extrapolate lower pressure data when a binary parameter value has been chosen.
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  • 153
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The following deliberations are concerned with the application of economy criteria to the optimization of process-engineering plants. We are therefore not concerned here with criteria for investment decisions, i.e., decisions on the implementation orabandonment of an investment project, nor with criteria for the selection of the most profitable investment options from a series of alternatives. Instead, we are interested here in the question of how a plant, while at the planning stage, can best be designed, i.e., the most rational method of selecting process parameters, such as throughputs, pressures, temperatures, concentrations, etc. The problem of plant optimization only occurs, however, when there are design parameters which can be selected at will or can, at least, be varied within certain limits. This is however, virtually always the case. There is then a need for an optimization strategy in the form of an objective function which is either reduced to a minimum, where lowest possible production costs are the target, for instance, or advanced to a maximum, where high profitability is the aim. The inclusion of engineering economy functions, in the form, namely, of the net present value function and the internal rate of return function for definition of such objective functions, provides better defined information on the best possible choice of process parameters than was possible with methods previosly used, such as the annuity method, for instance. One obtains different values for the process parameters to be optimized, depending on the objective functionused, and therefore different investment costs and utility consumptions. These differences are delineated and quantified using a process-engineering example in the course of the following discussion. The example selected is a gas scrubber, the function of which is to remove and recover useful components from a flow of gas. The specific problem examined is one of heat recovery.
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  • 154
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    Chemical Engineering & Technology - CET 20 (1997), S. 90-92 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of sodium lauryl sulphate (anionic) and Triton X-100 (nonionic) on the solid-liquid mass transfer at a gas-sparged fixed bed of copper Raschig rings was studied by measuring the diffusion-controlled dissolution of copper rings in acidified chromate solution. The variables studied were the nitrogen flow rate, the type of surfactant, and the surfactant concentration. It was found that an increase occurs in the solid-liquid mass transfer coefficient with increasing the nitrogen flow rate. Increasing the surfactant concentration was found to decrease the mass transfer coefficient. For a given surfactant concentration, it was found that Triton X-100 reduces the mass transfer coefficient more than sodium lauryl sulphate.
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  • 155
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    Chemical Engineering & Technology - CET 20 (1997), S. 571-575 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For a specific combustion problem involving calculations of several species at equilibrium, it is much simpler to write a special computer program and calculate the concentrations, rather than to use a generalized computer program. To calculate these concentrations, one must solve a set of non-linear algebraic equations. This work describes a procedure in which the Newton-Raphson method and the successive substitution method are combined. It is was found that for these types of problems the value of unknowns and the nature of the equations are such that by adopting the two procedures simultaneously a much faster and reliable convergence is achieved. This study also shows what possible species should be considered for these calculations.
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  • 156
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    Chemical Engineering & Technology - CET 20 (1997) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 157
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    Chemical Engineering & Technology - CET 20 (1997), S. 582-588 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The shape-selective transalkylation of biphenyl with pentamethylbenzene over ultrastable Y-faujasites to produce para-methylated biphenyls was studied in the liquid slurry phase. The reaction was carried out in a discontinuously operated stainless steel autoclave using n-heptane as the solvent with a temperature range of 513 to 533 K and a pressure of 3 MPa. As for the progress of the reaction the presence of strong Brønsted acid sites was essential, an ultrastable faujasite treated with aqueous hydrochloric acid having a high content of those sites was used as the catalyst. Thus, a yield of the target product 4,4′-dimethylbiphenyl of above 11% referring to biphenyl could be achieved. The effect of the operating conditions on the formation of the target product was investigated. The decisive influence was acted out by the molar ratio of biphenyl to alkylating agent, in so far as a surplus of pentamethylbenzene of 7:1 referring to biphenyl enhanced the yield of the target product to 14%. The kinetics of the reaction could be successfully descibed with a lumped reaction scheme, introducing pseudo components, summarizing structural isomers, and pseudo reactions, such as the formation of coke.
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  • 158
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    Chemical Engineering & Technology - CET 20 (1997), S. 624-632 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxidation of sulfide in oxygen-saturated aqueous solutions is accelerated by dissolved or silica-bonded cobalt phthalocyanines. On the basis of thermodynamical considerations it is postulated that the catalyst enhances the formation of disulfide as the initial elementary reaction step. The following reaction steps are largely unaffected by the catalyst, as indicated by a product ratio sulfate/thiosulfate=0.86, comparable to that of the uncatalyzed autoxidation. A Langmuir-Hinshelwood formalism is developed for the catalytic reaction step and is demonstrated to fit best with the kinetics. In addition, from the kinetic data free enthalpies for the adsorption of HS- (i) at the dissolved phthalocyanine (ΔG = -17.6 kJ/mole) and (ii) at the immobilized complex (ΔG = -20.0 kJ/mole) are calculated.
    Additional Material: 8 Ill.
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  • 159
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    Chemical Engineering & Technology - CET 20 (1997), S. 641-645 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An In-HZSM 5 honeycomb catalyst is used for the experimental investigations of the NO reduction with methane. The catalyst is prepared by the ion-exchange method. The influence of temperature and concentration of oxygen and methane is studied. In addition to methane, natural gas is used as reductant for the reduction of nitric oxide. The results are compared with those of other authors who use zeolithe pellets.
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  • 160
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    Particle and Particle Systems Characterization 14 (1997), S. 290-294 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A compact and commercial aerosol generator capable of generating narrowly size-distributed aerosols with high mass concentrations was designed, fabricated and tested. The aerosol generator, consisting of a Delavan simplex nozzle (Model 30610-4), an L-shaped settling chamber and a virtual impactor with a clean air core, was modified and improved from Chein and Lundgren's work [20] to be more compact and readily commercial. The performance of the aerosol generator was evaluated using corn-oil, sodium chloride and uranine solutions. The results indicated that the cornoil droplets produced by the generator had a mass medium aerodynamic diameter (MMAD) of 7.20 ± 0.32 μm with a geometric standard deviation (GSD) of 1.48 ± 0.01 and the aerosol generation rate was 13.8 ± 1.3 mg/min. Solid aerosols generated from NaCl solution were found to have an MMAD in the range 1.39-4.88 μm with a GSD of 1.34-1.47 with the volumetric solution concentration varying from 0.1% to 9%. At the same time, the aerosol generation rate varied from 0.27 ± 0.05 to 15.8 ± 1.8 mg/min. depending on the solution concentration and the particle size produced. In addition, a 0.01% uraniane solution was tested to generate a submicron aerosol with an MMAD of 0.93 μm and a GSD of 1.48.
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  • 161
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    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxidative coupling of methane (OCM) was carried out in a polytropic fixed-bed reactor applying a Zr/La/Sr catalyst developed by the Neste company. Over this catalyst the OCM reaction follows a complex reaction scheme which includes primary parallel reaction steps to CO, CO2 and C2H6 and consecutive reactions of ethane to ethylene or COx. Yield of higher hydrocarbons C2+ obtained with this catalyst strongly depended on reaction conditions, i.e. low partial pressures of methane and oxygen obtained by diluting the feed gas with nitrogen and high reaction temperatures promoted C2+ selectivity and yield. The maximum yield amounted to 21.4% (20 Vol.-% CH4, 9 Vol.-% O2, 71 Vol.-% N2, T = 860°C; XCH4 = 41.8%, SC2+ = 52.5%). This result belongs to the highest yields reported in the open literature.
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  • 162
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    Chemical Engineering & Technology - CET 20 (1997), S. 47-52 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An ultrasonic transmission technique is under development to determine the concentration of solids in a three-phase slurry reactor by measuring the velocity of ultrasound in slurries. Preliminary measurements have been made on slurries consisting of water, glass beads, and air bubbles. The data show that both the sound speed and attenuation are well-defined functions of both the solid and gas concentrations in the slurries. A simple model is proposed to correlate the concentration of solids with the measured ultrasonic signals.
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  • 163
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Chemical engineering is taught at German universities in three different types of curricula: chemical engineering proper, process engineering (“Verfahrenstechnik”), and industrial chemistry (“Technische Chemie”). Independent departments resp. faculties of chemical engineering exist at four universities. At other universities process engineering is offered as a complete curriculum with a smaller amount of chemistry than chemical engineering curricula, mostly by the departments of mechanical engineering. Industrial chemistry is an essential component of chemistry courses at most technical universities and optional subject at several classical universities. The cause of this diversity of approaches to chemical engineering can be traced back to the beginning of the production of high-value organics (dyes, pharmaceuticals) in Germany in the second half of the 19th century.
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  • 164
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    Chemical Engineering & Technology - CET 20 (1997), S. 485-490 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dynamic model of the liquid fluidized bed containing two or more solid particle species of different size and density is presented. The model incorporates the particle mass transport mechanisms of the convection and the dispersion. The movement of the upper interface of the bed subject to a change in the liquid velocity is specified using the mass balance constraint. The particle velocities and dispersion coefficients are evaluated using correlations. The model is capable of describing the bed expansion, concentration profiles of the individual particle species, the bulk density profile, and the occurrence of layer inversion.
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  • 165
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    Chemical Engineering & Technology - CET 20 (1997), S. 495-501 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An algorithm for the computation of design variables in layer crystallisation processes is presented, based on an algebraic solution of the moving boundary equation for heat transfer, as well as on an expression for the concentration profile. The algorithm was applied to the discontinuous crystallisation of a NaCl-H2O solution around the wall of an internally cooled cylindrical tube. Good agreement between simulation results and laboratory experiments was observed. After input of experimentally measurable values of the distribution coefficient, the algorithm enables the prediction of the following process variables along the crystallisation time: layer thickness, temperature, and composition profiles across the layer, as well as the end-values of solid and liquid mass and concentrations. Multistage processes can be studied by the series association of crystallisation cycles, enabling the determination of the optimal number of stages that meets a specific design criterion.
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  • 166
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    Chemical Engineering & Technology - CET 20 (1997), S. 522-532 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The intermixing of fluidizing gas between the compartments of a compartmented circulating gas fluidized bed fitted with a V-valve and riser combination has been experimentally studied. The intermixing of fluidizing gas that flows co-current (cross flow) as well as counter-current (back flow) to the circulating solids has been investigated. At low aerations, gas cross flow increased proportionally with the increase in solid circulation rate. But at high aerations, gas cross flow increased with aeration even when solid circulation decreased. Studies on back flow of gas revealed some interesting observations. At high fluidizing bed height on upstream side back flow of V-valve, gas has been negligible. But at low upstream bed heights and low aeration in V-valve and riser back flow of V-valve, gas has been substantial.
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  • 167
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    Chemical Engineering & Technology - CET 20 (1997), S. 511-521 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When working with disperse solid matter systems, one uses the effect of vibration in numerous processes. Solid matter mixing with vibration has only occurred in very simple units up to now. By means of the 3D-vibrational mixer from the company Kuston, Kleve, the influence of vibration on bulk materials and new mixing techniques are demonstrated. The 3D-vibrational mixer is suitable for liquids and solids, does not require mixing tools that need to be cleaned, and does not carry out rotary motions which would hinder incoming lines. It is used for mixing small amounts, where the mixing tank can be used simultaneously as the transportation container, so that a transfer is unnecessary.With the aid of 4 linear motors, the vibrational amplitudes and the frequencies can be varied within wide boundaries in all three spatial directions. By analyzing the vibrational system by means of Lissajous figures, it can be demonstrated that the optimal mixing effect occurs in the case of small frequency differences between the three axes. For freeflowing bulk materials, the best possible mixing state, the uniform coincidence mixing, is achieved after 2 min.
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  • 168
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    Chemical Engineering & Technology - CET 20 (1997), S. 23-28 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the present study, a mass transfer model for Type-1 facilitated transport in liquid surfactant membrane is developed by taking into consideration a size distribution of emulsion drops, and analytical solution of the model equations has been presented. The model takes into account the continuous phase and outer liquid membrane phase resistances along with diffusion through composite emulsion drop. Effort has been made to highlight the effect of the various system parameters on the extraction rate including computation of reaction front position. The results of this work are found to be in good agreement with the published experimental results on batch extraction of phenol using NaOH as internal reagent. The model would thus provide an insight of the separation mechanism involved in the mass transfer processes in this type of system.
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  • 169
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    Chemical Engineering & Technology - CET 20 (1997), S. 419-423 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: By applying the macroscopic conservation laws to a simplified jet downstream from a sudden enlargement, a new correlation of the two-phase subcritical pressure recovery is obtained. Comparisons with the set of existing data (air-water and steam-water subcritical flows) show that the predictions obtained by means of this formula are more accurate than the ones given by available analytical models. The proposed correlation presents an important improvement of the pressure recovery predictions in the case of small mass velocities. However, it can not be applied in the conditions of quality too close to one.
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  • 170
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    Chemical Engineering & Technology - CET 20 (1997), S. 435-444 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper describes how gain scheduling control is applied to a continuous stirred tank reactor model. The CSTR process, equipped with a cooling system, is modelled. Based on the resulting nonlinear model, a gain scheduling controller is designed. The gain scheduling follows a scheme denoted bias compensation. Compared to earlier reported gain scheduling schemes, the proposed scheme results in a controller that is less complex, which is advantageous in the controller implementation stage. Numerous simulations are performed, using the gain scheduling controller and two choices of control input to the reactor model. The simulation results indicate that a gain scheduling controller performs better than a linear controller. Simulations using different choices of control input to the reactor model indicate that proper process design is crucial for the controlled process performance.
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  • 171
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    Chemical Engineering & Technology - CET 20 (1997), S. 475-477 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple and new model for the prediction of drop velocity as a function of dispersed phase volume fraction has been proposed on the basis of experimental knowledge of onset time of complete separation between two phases as function of the initial hold-up.
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  • 172
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    Chemical Engineering & Technology - CET 20 (1997), S. 478-484 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two important structural factors that affect distillation efficiencies, the outlet weir heigh and the liquid flowpath length, are investigated. Performance and efficiency data of an industrial scale i-butane/n-butane distillation column equipped with two-pass trays are used as a basis for the calculations. A mathematical development for a new method for predicting the numbers of vapor and liquid phase transfer units is given. This method together with some other NTU calculation methods is used to assess the effect of the outlet weir height on efficiencies. The effect of outlet weir height on the Murphree tray efficiencies is investigated using the observed point efficiencies and different point efficiency to the Murphree tray efficiency relation methods. The effect of varying liquid flowpath lengths on efficiencies is studied by calculating the Murphree tray efficiencies for one-pass and two-pass trays. The results obtained using the NTU calculation method presented in this study show that a certain outlet weir height point efficiency reaches its maximum. Most of the other methods give opposite results giving a minimum for point efficiency at a certain outlet weir length. The results also show that the Murphree tray efficiencies for one-pass trays are higher than for two-pass trays. Obviously, this is caused by the longer liquid flowpath length of one-pass trays. The Murphree tray efficiencies are also calculated for an industrial-scale MTBE purification column. The column is equipped with two-pass trays in the stripping section and with one-pass trays in the rectifying section. The Murphree tray efficiencies of one-pass trays are considerably higher than the two-pass tray Murphree tray efficiencies.
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  • 173
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    Chemical Engineering & Technology - CET 20 (1997) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 174
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    Chemical Engineering & Technology - CET 20 (1997), S. 118-130 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dynamic model is developed for a fluid catalytic cracking (FCC) unit to describe the dynamic behavior of both the riser and the regenerator reactors and their interactions. The cracking reactions are simulated by the four-lumped kinetic model [1]. The reactions in the riser occur in a transported bed with the fluid and the solids in ideal plug flow. The two-phase nature of the regenerator-fluidized bed is considered and the kinetic model for the coke combustion on the cracking catalyst [2,3] is incorporated. The proposed model is validated using steady-state plant data from an industrial unit and the results are found to be in good agreement. One of the main advantages of the model is that it does not include any partial differential equations. This facilitates the solution of the equations and makes the model particularly suitable for control studies. Simulation studies are performed to investigate the effect of changing various process variables, such as catalyst circulation rate, gas oil feed rate, and oxygen feed concentration.
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  • 175
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    Chemical Engineering & Technology - CET 20 (1997) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 176
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    Chemical Engineering & Technology - CET 20 (1997), S. 182-191 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The uncatalyzed esterification of acetic acid is described in the literature as a typical example of reactive distillation. Many rigorous models were validated using this esterification as an example. Process proposals for the production of pure ethyl acetate from ethanol and acetic acid have been determined using short-cut methods with the assumption of chemical equilibrium only. In this publication, the limitations of this esterification are clarified, using a rigorous model that was developed. The reasons why reactive distillation appears to be unfavorable for this esterification are explained. It is, however, theoretically possible to obtain ethyl acetate in high purity with different variants of the process. Different process variants are examined in this work. Construction variables that are important for the design of reactive columns, such as the number of reactive separation stages and the holdup in the column, are analyzed. Furthermore, the influence of variables dependent on the component system, such as the phase equilibrium of the reactive system and the reaction kinetics on the conversion in the column, are described. It can be shown that the short-cut methods published so far for reactive distillation, which assume chemical equilibrium, are inadequate.
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  • 177
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    Chemical Engineering & Technology - CET 20 (1997), S. 203-207 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient heat transfer in a mechanically agitated vessel is studied in the case of an anchor and an helical ribbon impeller using Newtonian and shear thinning fluids. Temperature stratification is found more pronounced with the anchor, making this impeller clearly inadequate for heat transfer. The impact of natural convection is evaluated first using the classical Gr/Re2 ratio. It is shown that the use of this criterion in viscous mixing is somewhat misleading. A new Grashof number is then proposed to assess the significance of the viscous and buoyancy effects in non-isothermal, non-Newtonian mixing applications. It is shown that the interpretation of this new number is strongly related to the concept of process viscosity.
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  • 178
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    Chemical Engineering & Technology - CET 20 (1997), S. 240-246 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rate of the homogenous exothermic hydrolysis reaction of acetic anhydride catalyzed by sulfric acid in solvent acetic acid was estimated from nonisothermal experimental batch reactor transient temperature data. Rate equations based on three different reaction mechanisms of hydrolysis published in the literature were fitted to the experimental rate data. The experimental results on runaway and limit cycle behavior obtained with this reaction were explained by using the mechanism-based rate equations for hydrolysis in the reactor dynamic models, and good agreement was obtained between the predicted and the experimental dynamic data.
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  • 179
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    Chemical Engineering & Technology - CET 20 (1997), S. 282-284 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and 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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  • 180
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    Chemical Engineering & Technology - CET 20 (1997), S. 268-276 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: As an alternative to the existing bioheat transfer models a new system of two energy equations is proposed by considering the human body as a deformable porous medium. One equation is developed for the blood and the other for the peripheral skeletal tissue. It includes such significant factors as the vascular geometry and size, the blood flow and direction, thermal diffusion and the local thermal nonequilibrium between the blood and peripheral tissue. Discussion and application of both equations are given.
    Additional Material: 5 Ill.
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  • 181
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    Chemical Engineering & Technology - CET 20 (1997), S. 285-286 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An ortho-experiment design and the analysis method of mathematical statistics are adopted to study the conversion of gypsum and potassium chloride to potassium sulfate in the system of K+, Ca2+, NH4+ ‖ Cl-, SO42- in H2O. Optimal reaction parameters and engineering mean are acquired to attain a conversion yield of potassium chloride of 94.52%.
    Additional Material: 2 Tab.
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  • 182
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    Chemical Engineering & Technology - CET 20 (1997), S. 297-303 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Electrochemical gas absorption or biotechnical purification processes using structured packing as electrode or as biological support, respectively, may operate in bubble columns in presence of suspended solids. In both systems the knowledge of mass transfer rates from the liquid to the packing is important for the design of equipment. In the present investigation, the fluid dynamic behavior of a simple bubble column and a bubble column containing small size particles, both in presence of structured packing, was studied. Furthermore, mass transfer coefficients between the liquid and the structured packing were obtained by the electrochemical method. The influence of physical properties of the liquid phase, gas flow rate, kind and concentration of the suspended particles on both gas holdup and mass transfer was investigated. Correlations of the experimental data of mass transfer using dimensionless groups were derived and compared to previous correlations. Similarity with a heat transfer expression already used in two-phase systems was found.
    Additional Material: 9 Ill.
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  • 183
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    Chemical Engineering & Technology - CET 20 (1997), S. 333-337 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The reaction of anisole hydroxylation with hydrogen peroxide to form methoxyphenols over TS-1 was studied. Four C1-C3 alcohols and the two aprotonic solvents acetone and acetonitrile were used. Product conversion was almost proportional to the titanium content of the catalyst sample. The highest conversion and p-selectivity were observed in ethanol. Some speculations, based on the formation of substrate-solvent or titanium-solvent-oxidant complexes, about the role of the solvent are presented. It was found that in all the solvents studied the p/o ratio increased with time.
    Additional Material: 4 Ill.
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  • 184
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    Chemical Engineering & Technology - CET 20 (1997), S. 445-454 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two different layouts for the liquid-liquid extraction section of an industrial caprolactam process are evaluated. Laboratory mass transfer measurements on streams obtained from an industrial and a demonstration plant with different extraction sections are interpreted by a model describing the effect of surface contaminants on mass transfer coefficients. Indications of the impact of these layouts on the complexity of the extraction section, quality of products and efficiency of the extraction processes are given.
    Additional Material: 14 Ill.
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  • 185
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    Chemical Engineering & Technology - CET 20 (1997), S. 469-474 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bubble columns are commonly used in industry for polluted gas treatment. Based on the same principle, the droplet column which is not widely known in the literature, uses much higher gas velocities, up to 14 m/s. This study concerns the hydrodynamics and mass transfer in this apparatus, in presence or absence of solid particles. Our results have demonstrated the impact of dusts on mass transfer performance giving rise to an increase in the kL aL coefficient with decreasing particle size. However, no influence of dust on the hydrodynamics of the column has been demonstrated within the studied particle size range.A study of liquid holdups obtained by three different methods is also carried out. Our results are comparable, thus validating the methods used.
    Additional Material: 11 Ill.
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  • 186
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    Chemical Engineering & Technology - CET 20 (1997), S. 491-494 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experiments were carried out in a conventional circulating fluidised bed to measure the axial pressure profile and total pressure drop, which covered a wide range of operating conditions. Material belonging to the Geldart A (fine material) as well as the Geldart B (course material) categories have been used in the present work. Slip velocity is determined from the total pressure drop and noticed that the slip velocity is much higher than the free fall velocity of single particle for Geldart A type material, while it is approximately equal to the free fall velocity of single particle for the Geldart B type materials.A model is developed for slip velocity taking into account all the hindrance effects: particle-particle, and particle-wall, and particle agglomeration. Predictions of the present model are validated with the data due to present study and the data reported in the literature.
    Additional Material: 4 Ill.
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  • 187
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    Chemical Engineering & Technology - CET 20 (1997), S. 502-509 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dust explosion hazard exists in plants and facilities wherever combustible dusts are hardled. Minimum explosible concentration of dust clouds is an important factor requiring special attention for hazard evaluation if any technological equipment is to be protected by inertisation. The mathematical models available for prediction of this parameter have been analysed for their application to organic dust clouds. Solution of the most general mode for determination of minimum explosible concentration of dust clouds proposed by Mitsui and Tanaka is presented, together with the comparison with experimental data. It has been found that the model is not successful in predicting the minimum explosible concentration for organic dusts. Recommendations on requirement of development of a new model for prediction of minimum explosible concentration of an organic dust such as polyethylen have been given.
    Additional Material: 6 Ill.
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  • 188
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    Chemical Engineering & Technology - CET 20 (1997), S. 557-563 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Capillary viscometry is used to characterize viscosity, entrance pressure loss and apparent wall slip of paper coating colors at high shear rates. Special emphasis is laid on the dependence of these phenomena on solids content in order to account for changes in the rheology due to the dewatering of the color during the coating process. Coating colors with substantially different runnability have been investigated. Differences in apparent wall slip and high shear viscoelasticity (manifesting itself in extremely high entrance pressure losses) are observed at increased concentration, even if these phenomena do not show up at the initial solids content. Poor runnability is observed when viscosity, entrance pressure loss and wall slip increase strongly with increasing solids content. But all rheological features change simultaneously with the coating color recipe and it is not possible to separate out the contribution of the particular rheological features on the runnability of the coating colors or to correlate the runnability to a single rheological prorameter. Future work will have to focus on a numerical analysis of the blade coating process taking into account all the rheological features described here. First simulations including slip at the color/blade interface indicate that wall slip may cause severe runnability problems, at least when the apparent slip velocity exceeds the web velocity.
    Additional Material: 9 Ill.
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  • 189
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    Chemical Engineering & Technology - CET 20 (1997), S. 581-581 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and 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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  • 190
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    Chemical Engineering & Technology - CET 20 (1997), S. 10-16 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The performance of an upflow packed-bed biofilm reactor has been analyzed under dual substrate limitation conditions. The numerical solution of the proposed equations defining the system has been obtained for a wide range of operating conditions for a case of practical significance involving glucose and oxygen as dual substrates. The results show that the inlet glucose concentration defines the limiting substrate at a position near the inlet of the reactor. For inlet glucose concentrations up to 300 mg/l, glucose acts as the limiting substrate. However, for inlet concentrations of 400 mg/l of glucose or higher, oxygen assumes the role of the limiting substrate at that position. For all other positions in the reactor, glucose acts as the limiting substrate, irrespective of its inlet concentration. Extensive computations were performed in order to define regions where glucose, oxygen or both are limiting. The predicted results have been found to be in agreement with the theoretical criteria, proposed in the literature, of determining the limiting substrate.
    Additional Material: 8 Ill.
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  • 191
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    Chemical Engineering & Technology - CET 20 (1997), S. 36-39 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to reduce the B2O3 content in sintered magnesium oxide as much as possible, in precipitation with 80% of the stoichiometric quantity of dolomite lime, the effect of the pH of the agent used for rinsing the magnesium hydroxide precipitate was examined, as well as the effect of mannitol in sea water before precipitation. Mannitol binds orthoboric acid present in sea water into a weakly dissociated complex acid HB(OC)4. Experiments have shown that the B2O3 content in the sintered magnesium oxide samples is satisfactorily low. The lowest B2O3 content is obtained when mannitol is added; no B2O3 was found in these samples after sintering. Magnesium oxide samples were sintered at 1500°C; duration of isothemal sintering was one hour. Values for density and porosity of individually sintered samples are listed. The ratio CaO/SiO2 indicates that forsterite (Mg2SiO4), monticellite (CaMgSiO4) and mervinite (Ca3MgSi2O8) are formed during sintering of the samples.
    Additional Material: 1 Ill.
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  • 192
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    Chemical Engineering & Technology - CET 20 (1997), S. 53-62 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The minimum ignition temperature of dust clouds is one of the important factors required for the design of preventive measures against dust explosion. The mathematical models available to predict this parameter have been analyzed for thier application to organic dust clouds. A solution of the most general model proposed by Mitsui and Tanaka is presented, together with its comparision with experimental data. It has been found to be quite successful in predicting the minimum ignition temperature for metal dusts but not for organic dusts. Recommendations for the development of a new model to predict the minimum ignition temperature of an organic dust, such as polyethylene, have been given.
    Additional Material: 12 Ill.
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  • 193
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    Chemical Engineering & Technology - CET 20 (1997), S. 76-84 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: During recent years in chemical engineering processes for instance with aerated stirred tanks containing surface-active components foams and their mechanical control have become very important. However, there are still no rules for calculating mechanical foam breakers. As a contribution to foam control the present paper discusses the fundamentals of foam breaking by means of foam densities and gives a physical model for the mechanisms of a mechanical foam breaker when the main breaking effect is based on impact. The mechanisms were proved by measuring pressures in a foam breaker box. Diameters of secondary foam bubbles produced by foam breakers are calculated and discussed. Experimental investigations were made with different surfactants in aqueous solutions. The paper points out their influence on the process of foam breaking.
    Additional Material: 17 Ill.
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  • 194
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    Chemical Engineering & Technology - CET 20 (1997), S. 101-107 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A vapor pressure calculation procedure based on a lattice equation is applied to several compounds. Originally, the method was used to predict low vapor pressures of heavy hydrocarbons. In this work, the method is used at low vapor pressure for nonhydrocarbons, and a modified version is employed at high vapor pressure for n-alkanes. As the procedures require the knowledge of one vapor pressure datum only, they work in a predictive mode. Prediction for hydrocarbons is good and for nonhydrocarbons is poor. Prediction of n-alkanes high vapor pressure is good with an overall average relative absolute deviation under 6 percent.
    Additional Material: 5 Ill.
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  • 195
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    Chemical Engineering & Technology - CET 20 (1997), S. 144-148 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of the liquid phase hydrogenation of 4-tert-butylphenol to form cis- and trans- 4-tert-butylcyclohexanol at 1.0-10.0 MPa and 40°C in isopropanol over a Rh catalyst has been studied. The kinetic behavior of this parallel system is described by a proposed reaction network. Keto-enol tautomeric transformation of adsorbed 4-tert-butyltetrahydrophenol and 4-tert-butylcyclohexanone is thought to be a key step, which governs the stereoselectivity of the overall complex reaction of alkylphenol hydrogenation.
    Additional Material: 4 Ill.
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  • 196
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    Chemical Engineering & Technology - CET 20 (1997), S. 162-170 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The performance of an upflow packed-bed biofilm reactor has been analyzed under multisubstrate limitation by considering simultaneous carbon oxidation and nitrification reactions. The fasting shock load of inlet methanol concentration has a much more pronounced effect on the response of the system compared to that of inlet NH4+ -nitrogen concentration. The exit concentration of NH4+ -nitrogen drops very close to zero, thereby showing essentially complete nitrification during methanol fasting condition. Further, the concentration profiles of oxygen within the biofilm show significant variation during methanol fasting and nonfasting conditions whereas during NH4+ -nitrogen fasting conditions the oxygen concentration profile in the biofilm remains essentially unaffected.
    Additional Material: 6 Ill.
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  • 197
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    Chemical Engineering & Technology - CET 20 (1997), S. 199-202 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An electrochemical technique which involved measuring the limiting current of the cathodic reduction of potassium ferricyanide was used to study the rate of mass transfer inside a cubical cavity machined in the wall of a vertical rectangular duct. Variables studied were side length, physical properties of the solution and flow rate of the solution. The mass transfer coefficient was found to decrease with increasing cavity size; in all cases, the mass transfer coefficient inside the cavity was less than that at the duct wall. Mass transfer data inside the cavity were correlated by the equation Shc = 0.525 (Sc Re de/L)0.33. Comparison of the present results with the results obtained using other cavity geometries shows that cavity geometry plays an important role in determining the rate of mass transfer inside the cavity.
    Additional Material: 6 Ill.
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  • 198
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    Chemical Engineering & Technology - CET 20 (1997), S. 212-219 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Subnetwork Corollary provides some sufficient conditions for which a complex reaction network could be determined to have capacity of admitting multiple positive steady-states, if it contains a subnetwork that also admit multiple positive steady-states. A family of reaction networks, involving catalytic reactions in an isothermal continuous flow stirred tank reactor (CFSTR), is determined to have the capacity to exhibit steady-state multiplicity by implementation of the Deficiency One Algorithm and the Subnetwork Corollary. A set of rate constants and two corresponding positive steady-states are constructed for several cases.
    Additional Material: 6 Ill.
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  • 199
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    Chemical Engineering & Technology - CET 20 (1997), S. 247-258 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: New uses of artificial selective membranes, particularly ion-exchange membranes, improve on traditional methods of treating liquid mixtures before, during or after chemical or biochemical reactions. With the correct choice of ion-exchange membrane in a membrane reactor, reactions can be performed in such a way that the main product is not contaminated by undesired byproducts. Recent examples, mainly in organic chemistry, are given for eight typical ion-exchange membrane reactors: electrodialysis (ED), electrometathesis (EMT), electro-ion substitution (EIS), electro-ion injection-extraction (EIIE), coupled counter-transport (CCT), electro-electrodialysis (EED), electrohydrolysis with bipolar membranes (EHBM), and catalysis with ion-exchange membrane (IEMC).
    Additional Material: 25 Ill.
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  • 200
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    Chemical Engineering & Technology - CET 20 (1997), S. 277-281 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new method for cleaning inner surfaces of pipes was studied both theoretically and experimentally. The method is based on the phenomenon of a sphere rotating in a pipe (levitation), when the translational movement of the sphere is restricted and the sphere is subjected to fluid flow in the pipe. The high rotation velocity causes a vibration process, which may be exploited for cleaning sediments or rust from the inner surfaces of pipes. A simplified theoretical model for the determination of the relationships among the dimensionless parameters governing the rotation phenomenon was developed. The model was validated with experimental data and found to be appropriate for engineering design of the system. Application of the cleaning method was demonstrated by cleaning the sediments and rust off the inner surface of a one-inch nominal diameter pipe.
    Additional Material: 6 Ill.
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