Pd-Cu/γ-Al2O3催化苯乙炔选择性加氢反应

为了提高苯乙炔加氢反应中的苯乙烯选择性, 本文采用“胶体-等体积浸渍”两步法制备了Pd-Cu/γ-Al₂O₃双金属催化剂. 利用高分辨率透射电镜(HRTEM)、X射线光电子能谱(XPS)、CO脉冲化学吸附、N2物理吸附、电感耦合等离子体原子发射光谱(ICP-AES)等技术表征了Pd-Cu/γ-Al₂O₃的结构性质, 考察了Cu/Pd 摩尔比、Pd负载量以及金属引入顺序对Pd-Cu/γ-Al₂O₃催化苯乙炔选择性加氢性能的影响. 结果表明, 与Pd/γ-Al₂O₃单金属催化剂相比, Pd-Cu/γ-Al₂O₃的苯乙烯选择性大幅度提高, 尤其是当Pd负载量为0.3%(w), 且Cu/Pd摩尔比为0.6时, Pd-Cu/γ-Al₂O₃表现出优异的加氢选择性; 在0.1 MPa和40 ℃下, 当苯乙炔转化率为90%时, 双金属催化剂的苯乙烯选择性可达95%; 当转化率达到99%以上时, 苯乙烯选择性仍保持在82%左右. 分析表明, Pd-Cu/γ-Al₂O₃中形成了Pd-Cu合金, 但是两种金属间不存在电子转移, Cu对Pd的几何效应才是导致Pd-Cu/γ-Al₂O₃苯乙烯选择性增加的主要原因.

Selective Hydrogenation of Phenylacetylene over Pd-Cu/γ-Al2O3 Catalysts

A two-step method combining colloid synthesis and incipient wetness impregnation was developed for the preparation of bimetallic Pd-Cu/γ-Al₂O₃ catalysts, with the aim of increasing the selectivity to styrene in the selective hydrogenation of phenylacetylene. The structural properties of the catalysts were characterized using high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), CO-pulse chemisorption, N₂ physisorption, and inductively coupled plasma atomic emission spectrometry (ICPAES). The effects of changing the Cu/Pd molar ratio, the Pd loading, and the order in which the Pd and Cu were introduced into the catalysts on the catalytic activity and selectivity were investigated. The results showed that Pd-Cu/γ-Al₂O₃ exhibited much higher selectivity toward styrene than Pd/γ-Al₂O₃. In particular, Pd-Cu/γ-Al₂O₃ with a Pd loading of 0.3%(w) and a Cu/Pd molar ratio of 0.6 displayed excellent performance at 40℃under 0.1 MPa H₂, with a high selectivity of 95% at a conversion of 90%, and a selectivity of approximately 82%, even at conversions of higher than 99%. The increased selectivity of Pd-Cu/γ- Al₂O₃ was ascribed mainly to the geometrical effects of the Pd-Cu bimetallic alloys, rather than the electronic effects, since no electron transfer occurred between Pd and Cu.