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硅胶负载的钯-金双金属催化剂是乙烯乙酰氧基化制乙烯基乙酸酯(VA)的高选择性催化剂,本文应用平面和负载纳米颗粒模型催化剂体系研究金的助催化作用,应用低能离子散射谱、低能电子衍射、X射线光电子能谱、反射红外吸收光谱及程序升温脱附等技术表征这些模型催化剂.结果表明,金的主要助催化作用是隔离催化剂表面的催化活性钯原子,形成孤立的钯活性中心,从而大大抑制或消除反应物和/或产物在毗邻多原子钯中心上的深度分解,提高VA合成的选择性及活性.同时由于形成了孤立的钯原子活性中心,反应副产物或中间物之一的一氧化碳吸附较弱,避免了催化剂表面的一氧化碳中毒,进而提高催化活性.
The silica-supported palladium-gold bimetallic catalyst is a highly selective catalyst for ethylene acetoxylation of vinyl acetate (VA). In this paper, the catalytic activity of gold is studied by using a planar and supported nanoparticle model catalyst system. The application of low energy ions Scattering spectra, Low-energy electron diffraction, X-ray photoelectron spectroscopy, Reflectance infrared absorption spectroscopy and temperature programmed desorption were used to characterize these model catalysts. The results showed that the main cocatalytic effect of gold was to separate the catalytically active palladium atoms on the surface of the catalyst, Of Pd active centers, thereby greatly inhibiting or eliminating reactants and / or products in the adjacent polyatomic palladium center on the depth of decomposition, improve the synthesis of VA selectivity and activity. At the same time as a result of the formation of an active center of palladium atoms, the reaction by-products Or one of the intermediates has a weak adsorption of carbon monoxide and avoids carbon monoxide poisoning on the surface of the catalyst, thereby increasing the catalytic activity.