Hydrogenation of 1-Butene and 1,3-Butadiene Mixtures over Pd/ZnO Catalysts
Hydrogenation of 1-Butene and 1,3-Butadiene Mixtures over Pd/ZnO Catalysts
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DOI：
10.1006/jcat.1993.1164
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发表时间：
1993-06
影响因子：
7.3
通讯作者：
A. Sárkány;Z. Zsoldos;B. Furlong;J. Hightower;L. Guczi
中科院分区：
文献类型：
--
作者：
A. Sárkány;Z. Zsoldos;B. Furlong;J. Hightower;L. Guczi
制备了几种不同负载量和分散度的ZnO负载钯催化剂，并对其进行了表征、预处理和1-丁烯中少量1，3-丁二烯选择性加氢试验。在高于423 K的温度下的氢处理引起催化活性的显着降低，同时增加丁二烯主要还原为烯烃的选择性。这样的处理还引起ZnO载体的部分还原，这导致形成PdZn金属间相（XRD结果）。XPS测量表明，Pd微晶被“装饰”与减少Zn金属显着降低的Pd吸附位点的可用性，如通过氢和一氧化碳化学吸附测定。交替的氧化和程序升温还原循环可以区分（PdO）S的形成和还原Zn的氧化。即使整体活动后，高温暴露于氢减少，营业额频率为少量的活性位点几乎保持不变。此外，活化能和反应级数没有改变。高温还原也降低了从丁二烯形成的反式/顺式-2-丁烯比：这可能反映了吸附在Zn装饰表面上的1，3-丁二烯的顺式和反式构象之间的缓慢相互转化。这些实验已经确定了载体和预处理条件对此类催化剂性能的一些重要作用。
Several palladium catalysts supported on ZnO with different loadings and dispersions have been prepared, characterized, pretreated, and tested for the selective hydrogenation of small amounts of 1,3-butadiene in 1-butene. Hydrogen treatment at temperatures above 423 K caused a marked decrease in catalytic activity and a simultaneous increase in selectivity for reduction of butadiene primarily to olefins. Such treatment also caused partial reduction of the ZnO support which resulted in the formation of PdZn intermetallic phases (XRD results). XPS measurements suggested that the Pd crystallites were "decorated" with reduced Zn metal which significantly decreased the availability of the Pd adsorption sites, as determined by hydrogen and carbon monoxide chemisorption. Alternate oxidation and temperature-programmed reduction cycles could distinguish between the formation of (PdO)S and oxidation of the reduced Zn. Even though the overall activity was decreased after high-temperature exposure to hydrogen, the turnover frequency for the smaller number of active sites remained virtually unchanged. Moreover, the activation energy and reaction orders were not altered. High-temperature reduction also decreased the trans/cis-2-butene ratio formed from the butadiene: this may reflect slow interconversion between the syn and anti conformation of the 1,3-butadiene adsorbed on the Zn-decorated surface. These experiments have identified some of the important roles of the support and pretreatment conditions on the performance of such catalysts.