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  • Industrial Chemistry and Chemical Engineering  (7)
  • Wiley-Blackwell  (7)
  • American Institute of Physics (AIP)
  • De Gruyter
  • Wiley
  • 1990-1994  (7)
  • 1965-1969
  • 1950-1954
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  • Wiley-Blackwell  (7)
  • American Institute of Physics (AIP)
  • De Gruyter
  • Wiley
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Effect of doping with nickel and copper on catalytic behaviour of wide-pore zeolites with different pore structures (1991)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 14 (1991), S. 200-208 
    Details
    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 catalytic properties of wide-pore zeolites, namely Ni- and Cu-doped faujastie H-Y and H-mordenite (H-M) are compared on the example of conversion of n-hexane. After thermal pretreatment of ion-exchanged zeolites, reduction with hydrogen (PH2 ≤ 40 bar) leads to a large number of metallic clusters and crystallites as well as ionic species in the zeolites. Notwithstanding this variety, the different types of catalysts can be divided into three classes: classical bifunctional catalysts (for example NiHM, NiHY) with ion exchange degrees 〉 30%, monofunctional catalysts, such as CuHM and CuHY with high copper contents (ion exchange degree 〉 40%) and metal-doped (Ni and Cu) zeolites which, depending on the conditions of pretreatment, act as bifunctional and/or monofunctional compounds and, therefore, show very unstable reaction behaviour. In addition to the extent of reduction, the cation distribution affects the activity and deactivation behaviour and, to a lesser extent, the product selectivity. The reaction mechanism of bifunctional catalysis is similar to that observed in platinum-doped catalysts, while the mechanism of monofunctional catalysis resembles the process on undoped zeolites.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270140308
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  • 2
    Electronic Resource
    Electronic Resource
    Design Data for Cyclones (1991)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 301-307 
    Details
    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: For many years efforts have been made to describe the complex process of particle separation in cyclones, and a multitude of separation models have been set up. A comparison of such separation models fails because insufficient usable test results are available and systematic and precise investigations are missing.It is important for the design of cyclones to rate their separation properties by means of the fractional collection efficiency. On account of the known measuring problems, the data supply of reliable fractional efficiency curves of cyclones is still too small. Fractional efficiency as a function of the entrance velocity was measured with a high-speed optical measuring technique. Measurements of low dust concentrations are presented. Geometrically similar cyclones of four different sizes were investigated. The fractional efficiency curves are plotted versus dimensionless parameters and the validity of the design criteria gained in this way is shown. The influence of particle shape on the fractional efficiency curves is discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19910080155
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  • 3
    Electronic Resource
    Electronic Resource
    Interaction Between the Motion of particles and their turbulent carrier fluid flow (1992)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 9 (1992), S. 116-124 
    Details
    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: The turbulence occurring in the flow of the carrier fluid exerts a substantial influence on the motion of suspended particles or droplets. This influence is obvious, e.g. if fine particles are dispersed in free flows or deposited on free surfaces, bluff obstacles or channel walls. With application in aerosol science in mind, the interaction between dispersed phase and carrier fluid is described in terms of turbulence intensities, energy spectra, turbulence time scales and eddy diffusivities. Experimental results obtained for different important flow types are reviewed and compared with theoretical predictions. With regard to the latter, the different methods of treating theoretically turbulent two-phase flows of low concentration are discussed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19920090116
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of thermal pretreatment and reduction on acidity and metal state in doped NiH and CuH mordenites (1991)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 14 (1991), S. 428-436 
    Details
    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: Thermal pretreatment such as calcination and steaming as well as the reduction of cations by hydrogen, affect the zeolitic acidity and activity of nickel- and copper-doped mordenites in heterogeneously catalyzed reactions such as the conversion of n-hexane. Data on acidity changes were obtained by IR spectroscopy, and information on ionic and metallic states by temperature-programmed reduction, CO chemisorption and transmission electron microscopy (TEM). The findings were compared with reaction results from conversion of n-hexane. Trimethylamine (TMA) was selected as a standardization molecule for semi-quantitative determination of acidity. Correlation of relative acidity values with experimental results was possible only to a very limited extent. Results of CO chemisorption, TPR and TEM allow conclusions to be drawn on metallic crystallites, Ni+ and Cu+ ions and clusters, which appear to exert a stabilizing influence on zeolitic activity. Nickel crystallites with d 〉 2 nm catalyze both hydrogenation and dehydrogenation of paraffins on the metal in bifunctional catalysis, as was also observed on platinum-doped zeolites.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270140611
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  • 5
    Electronic Resource
    Electronic Resource
    Production of methylamines over ZK-5 zeolite treated with tetramethoxysilaneDedicated to Professor Hans Kroepelin on the Occasion of his 90th Birthday (1992)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 15 (1992), S. 202-212 
    Details
    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 methonol with ammonia over catalysts, used commercially today, to give methylamines, does not occur with the desired dimethylamine selectivity. Both a thermodynamically and kinetically controlled reaction over conventional catalysts permits a maximum dimethylamine selectivity (DMA selectivity) of only about 30 mol-%. In addition to monomethylamine (MMA), a large amount of the undesirable trimethylamine (TMA) is formed. By using zeolites and taking advantage of their shap-selective properties, it is possible to achieve high MMA and DMA selectivities. Shape-selective catalysis can only take place at catalytically active centrs in the inteerior of the por system. The proportion of non-shape-selective catalysis at the active centres on the outer surfaces of zeolites is not negligible. Treatment of ZK-5 zeolite with tetramethoxysilane deactivates the outer surface of the crystallite and increases the shape-selectivity of the ZK-5 zeolite with rgard to the amination reaction. Computer simulation of the zeolite skeleton in conjuction with investigations of the reaction leads to some conclusions with respect to the reaction mechanisms and reaction sites.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270150309
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  • 6
    Electronic Resource
    Electronic Resource
    Inertial impaction of aerosol particles on single and multiple spherical targets (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 88-94 
    Details
    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: Inertial deposition of aerosol droplets (diameter: 1-14 μm) on steel spheres (diameter: 3-9 mm) was investigated. Air velocity was varied between 7 and 28 m/s (corresponding sphere Reynolds numbers: 1400-17000). The impaction on single spheres as well as that on linear arrays of eight spheres was measured. Theoretical results, based on potential flow investigations were verified by single sphere experiments. Of special interest was the range of lower Stokes numbers, where the theoretically predicted limit of deposition cannot be verified. The experiments on sphere arrays were for the first time performed in the low Stokes number range. Deposition on the leading sphere, relative to that on the shielded spheres, exhibits a maximum in the high Stokes number range, but this changes drastically in the low Stokes number range. Here, maximum deposition can be found on the shielded spheres while the leading sphere shows a markedly lower deposition.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170204
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  • 7
    Electronic Resource
    Electronic Resource
    Basic characteristics of spinel type manganese mixed oxide/titanium composite anodes for electroorganic redox catalysisDedicated to Professor Dr. Hartmut Wendt on the occasion of his 60th birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 338-347 
    Details
    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: Manganese mixed oxide composite layers of about 1 μm thickness on titanium sheet as substrate were fabricated by firing of the corresponding nitrates at a typical temperature of 400°C in air. The activity of these anodes was evaluated by cyclic voltammetry (10 mV/s) and the stability was determined by chronopotentiometry (2.5 mA/cm2) in 1M H2SO4. The oxidation of 2-propanol was examined as a simple electroorganic model reaction. The quality of a first category of mixed oxides with general composition MnMe2O4 decresed in the order Me = Co, Ni, Fe. In a second group with the general formula MeMn2O4 a decrease in the order Me = Co, Cu, Fe, Ni, Ti, Zn, Cd, Ca, Mg, (Zn, Ge), Li was observed. The corresponding candidates of the second group were superior to those of the first. The anode service life τ of the optimum spinel anode CoMn2O4/Ti is dependent on the current density, according to jλ τ = const. (λ = 1.7). Thus high current densities are precluded. The mechanism has been discussed in terms of a heterogeneous redox catalysis: surface Mn(VII) states are formed in a slow electrochemical step. In a subsequent fast chemical oxidation of the organic molecule the original reduced state is regenerated. This also explains the comparatively good service life of these anodes.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170508
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