Abstract: In this paper, the key problems of catalyst deactivation caused by the formation of green oil on the surface of acetylene selective hydrogenation Pd⁃Ag catalyst were investigated. XRD and H2⁃TPR were used to characterize the composition and the structure of catalyst. The selective hydrogenation performance of Pd⁃Ag catalyst for acetylene and the formation of green oil precursor C4 olefins during the reaction were investigated by using a 10 ml fixed bed high pressure hydrogenation unit. The results show that there are significant differences in the acetylene hydrogenation activity of Pd⁃Ag/Al2O3 catalysts in several different preparation processes, which mainly depend on the dispersion of Pd on the catalyst surface. The close mixing between the promoter Ag and the active center Pd can enhance the electrons and geometric effect, more Pd⁃Ag alloy phase is generated, which reduces the hydrogenation activity of the catalyst, but increases the stability of the catalyst; while the amount of C4 olefins is positively correlated with the activity of the catalyst. The higher the catalyst activity, the more C4 olefins are generated. The conclusion of this study reveals the deactivation mechanism of Pd⁃Ag catalyst, which has important guiding value for catalyst modification and process condition optimization.

Key words: Pd?Ag/Al2O3 catalyst, Deactivation, Selective hydrogenation of acetylene, C4 olefins

摘要： 针对乙炔选择性加氢Pd⁃Ag催化剂表面绿油生成导致催化剂失活的关键问题，运用XRD和H2⁃TPR表征催化剂的组成及结构性质，运用10 mL固定床高压加氢装置考察了Pd⁃Ag催化剂的乙炔选择性加氢性能及反应过程中绿油前驱体C4烯烃的形成规律。结果表明，不同制备工艺的Pd⁃Ag/Al2O3催化剂乙炔加氢活性存在明显差异，这主要取决于Pd在催化剂表面的分散形式，助剂Ag和活性中心Pd之间紧密的混合可增强电子和几何效应，形成更多的Pd⁃Ag合金相，降低了催化剂的加氢活性，但增加了催化剂的稳定性；而C4烯烃生成量与催化剂活性呈正相关，催化剂活性越高生成的C4烯烃越多，研究结论揭示了Pd⁃Ag催化剂的失活机制，对催化剂的改性和工艺条件优化具有重要的指导价值。

关键词: 　Pd?Ag/Al2O3催化剂, 　失活, 　乙炔选择性加氢, 　C4烯烃