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31.
Katarzyna Samson Anna Klisiska Irena Gressel Barbara Grzybowska 《Reaction Kinetics and Catalysis Letters》2002,77(2):309-315
VOx/TiO2 and MoOx/TiO2 catalysts with the addition of Re (Re/V or Mo = 0.5) were synthetized and tested in oxidative dehydrogenation of propane and in reduction by propane. XPS measurements showed depletion of the surface in Re. The Re additive does not affect the total conversion of propane, but increases the selectivity to propene. The effect is more pronounced for the MoOx/TiO2 catalyst. The increase in the selectivity to propene is accompanied with the increase in the reducibility of the catalysts. 相似文献
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Wen-Chang Chen Samson A. Jenekhe Jeffrey S. Meth Hermann Vanherzeele 《Journal of Polymer Science.Polymer Physics》1994,32(1):195-200
An investigation of the refractive index and third-order nonlinear optical susceptibility χ(3) of two polypernigraniline derivatives, poly (4,4'-diphenylimine methine) (PDPIM) and poly (4,4'-diphenylimine p-heptyloxybenzylidene) (PDPIHB) reveals effects of molecular structure on the linear optical and nonlinear optical properties of conjugated polymers. The χ(3) (?3ωω,ω,ω) of PDPIM was found to decrease relative to polypernigraniline, reflecting the observed decrease of the oscillator strength of the 2.2 eV absorption band when a methine carbon replaces one of the nitrogen atoms of pernigraniline repeat unti. The alkoxyphenylene side group substitution at the methine carbon in PDPIHB, however, significantly enhances the nonlinear optical response of PDPIHB while reducing the refractive index compared to PDPIM and polypernigraniline. The present results suggest that structural changes in conjugated polymers can be made in such a way as to enhance the nonlinear optical properties while modulating the linear optical properties. © 1994 John Wiley & Sons, Inc. 相似文献
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The stereochemistry of the lithium-liquid ammonia reduction of 2,3-dimethyl-4-hydroxy-2-cyclopentenone is discussed as a function of the acidity of the proton donor. It is shown that the configuration of the resulting 2,3-dimethyl-1,4-dihydroxycyclopentene is determined by competing intra- and intermolecular protonation. 相似文献
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The stereochemical outcome of the lithium-liquid ammonia reduction of 2,3-dialkyl-4-hydroxy-2-cyclopentenones and 2,3-dialkyl-2-cyclopentenones possessing bulky substituents (i-propyl and t-butyl) is investigated, using different proton donors. The relative configuration of both alkyl groups in the reduction products is interpreted on the basis of the geometry of the transition state for protonation of the intermediate enolate anions formed during the reduction 相似文献