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  • 1
    Electronic Resource
    Electronic Resource
    Radiation-induced paramagnetic defects in heavy metal fluoride glasses
    Amsterdam : Elsevier
    International Journal of Radiation Applications & Instrumentation. Part C, 32 (1988), S. 439-442 
    Details
    ISSN: 1359-0197
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/1359-0197(88)90046-X
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  • 2
    Electronic Resource
    Electronic Resource
    Potential reaction intermediates of NOx reduction with propane over Cu/ZSM-5 (1995)
    Springer
    Catalysis letters 32 (1995), S. 83-92 
    Details
    ISSN: 1572-879X
    Keywords: NOx reduction ; Cu/ZSM-5 catalyst ; adsorbed nitrate, IR spectra of ; adsorbed nitro group, IR spectra of ; adsorbed NOx, reduction to N2 ; adsorbed NOx, H abstraction by ; H abstraction from alkanes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Adsorption complexes that are formed by exposing Cu/ZSM-5 to nitric oxides have been identified by FTIR. Some of them are thermally decomposed below 200°C, but others, though much more stable thermally, are reduced at low temperature by chemical interaction with gaseous propane. The FTIR spectra suggest that the latter complexes are nitro and/or nitrate groups associated with Cu ions. Their formation and reduction when Cu/ZSM-5 is exposed to NO + O2 + C3H8 seems consistent with the assumption that they are intermediates in catalytic NOx reduction. Mass spectrometric analysis of the gases that are released when these complexes react with propane reveals formation of N2, whereas thermal decomposition at higher temperatures only yields NO2, NO, H2O, traces of O2, but no N2. The results suggest that adsorbed NOy, groups (y ⩾ 2) are able to abstract H atoms from hydrocarbon molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806103
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  • 3
    Electronic Resource
    Electronic Resource
    Competitive mechanisms ofn-butane isomerization on sulfated zirconia catalysts (1995)
    Springer
    Catalysis letters 33 (1995), S. 135-143 
    Details
    ISSN: 1572-879X
    Keywords: sulfated zirconia ; butane isomerization ; 13C labelled butane ; intermolecular mechanism of isomerization ; bimolecular mechanism of isomerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Isotopic analysis ofn-butane isomerization over sulfated zirconium oxide, using double13C-labelledn-butane, shows that at low temperature this isomerization is an inter-molecular process. Probably, a C8 surface intermediate is formed which isomerizes and undergoes β-fission; the iso-C4 fragments are desorbed asi-butane. Previously, the same mechanism was indicated for Fe, Mn promoted catalysts. The isomerization rate at 130°C is drastically lowered by gaseous H2, because the concentration of the unsaturated species, required for the formation of the C8 intermediate, is low under such conditions. Whereas13C-scrambledi-butane is a true primary product, isotopic scrambling ofn-butane continues after chemical equilibrium betweenn-butane andi-butane has almost been reached; i.e.13C scrambledn-butane is a secondary product. Intra-molecular rearrangement of carbon atoms inn-butane precedes intermolecular scrambling. The similarity of the isomerization mechanism over unpromoted sulfated zirconia and Fe, Mn promoted sulfated zirconia is paralleled by an equal strength of the acid sites in both catalysts. The shift in the FTIR band of CO adsorbed on the Lewis sites indicates that these sites, presumably surface Zr4+ ions, are weaker acids than A13+ in dehydrated alumina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00817053
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  • 4
    Electronic Resource
    Electronic Resource
    Co-adsorption of nitrogen monoxide and nitrogen dioxide in zeolitic de-NOx catalysts (1994)
    Springer
    Catalysis letters 28 (1994), S. 119-130 
    Details
    ISSN: 1572-879X
    Keywords: adsorption ; TPD ; NO ; NO2 ; Na/Y ; Na/ZSM5 ; Cu/ZSM5 ; SiO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Room temperature adsorption and temperature programmed desorption (TPD) of NO, NO with O2, and NO after NO2 saturation were investigated for Na/Y, Na/ZSM5, Cu/ZSM5 and SiO2 gel. The adsorbates were characterized by TPD, using mass spectrometry to identify the desorbed molecules. In the presence of O2, the adsorption of NO and NO2 is non-additive; co-desorption of nearly equal amounts of NO and NO2 takes place suggesting the formation of a complex with an overall composition N2O3 within the zeolite. Since SiO2 gel does not adsorb NO nor NO2, the adsorption capacity of the zeolites is a function of their specific structure. The oxidation of NO to NO2 is catalyzed by Na/Y and Na/ZSM5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806041
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetics of bulk styrene polymerization catalyzed by symmetrical bifunctional initiators (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 35 (1988), S. 1547-1562 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The kinetics of bulk styrene polymerization catalyzed by symmetrical bifunctional initiators [2,5-dimethyl-2,5-bis(benzoyl peroxy) hexane] is studied. Being characterized by the presence of two peroxide groups of equal thermal stabilities, this bifunctional initiator system shows complex initiation, propagation, and termination reaction pathways. The kinetic model for bulk styrene polymerization with the bifunctional initiator is presented and compared with experimental data. The experimental data indicate that the model is quite satisfactory in describing the polymerization rate and polymer molecular weights for bulk styrene polymerization catalyzed by the symmetrical bifunctional initiator.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1988.070350612
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  • 6
    Electronic Resource
    Electronic Resource
    Melt transesterification of dimethyl terephthalate with ethylene glycol (1989)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1445-1456 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of a semibatch melt transesterification of dimethyl terephthalate (DMT) with ethylene glycol (EG) is studied with zinc acetate as a catalyst. This paper quantifies the effect of various reactor operating conditions on the transesterification rate and the product composition distribution. Our experiments support the assumption that the methylesters in DMT and growing oligomer chains have the same reactivities for transesterification with EG and that the reactivity of hydroxyl groups in pure EG for esterification with DMT is twice that of the hydroxyl group in oligomers. With a molecular species model in which various oligomers are identified by the type of functional end groups, the progress of the transesterification and the oligomer concentration distribution were estimated and the agreement between the model predictions and the experimental data were excellent. It has also been shown that 30 wt. % of oligomers are produced for [EG]/[DMT] molar ratio of three, and up to 70 wt. % oligomers are produced at the [EG]/[DMT] molar ratio of one.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690350905
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  • 7
    Electronic Resource
    Electronic Resource
    Modeling of free-radical polymerization of styrene by bifunctional initiators (1987)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 2067-2076 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A detailed kinetic model for the bulk styrene polymerization initiated by symmetrical diperoxyester bifunctional initiators is presented. When chain termination occurs via a combination termination mechanism, six distinct polymeric species are identified in accordance with the nature of the polymer end units. It is shown that the unequal thermal decomposition characteristics of the peroxides of the bifunctional initiator system lead to the formation of polymers having considerably higher molecular weight than those obtained by the monofunctional intiator systems. It has also been found that high monomer conversion, high molecular weight, and narrow molecular weight distribution can be obtained simultaneously by using the bifunctional initiators at high reaction temperatures. This is due to the reinitiation and propagation of inactive polymers carrying undecomposed peroxides. The molecular-weight-increasing effect of the bifunctional initiator is more pronounced at high reaction temperatures. The new possibilities of increasing the monomer conversion and controlling the polymer molecular weight properties more effectively through the use of bifunctional initiators are discussed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690331217
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  • 8
    Electronic Resource
    Electronic Resource
    A melt prepolymerization of poly(ethylene terephthalate) in semibatch stirred reactors (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 2987-3024 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A semibatch melt prepolymerization of poly(ethylene terephthalate) (PET) is studied. Being characterized by complex reaction pathways leading to various functional end groups and side products, PET prepolymerization process poses a challenging modeling problem. Ten distinct polymeric species have been defined in accordance with the type of functional end groups and the corresponding mass balance and moment equation are developed to estimate the progress of reaction and polymer molecular weight. The effect of various reactor operating conditions on the performance of the polymerization process has been examined through numerical simulation of the molecular species model developed. In particular, the effect of incomplete transesterification of methyl ester groups on the polymer molecular weight has been investigated in detail.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070411135
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