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°C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.%A two-step method combining col oid synthesis and incipient wetness impregnation was developed for the preparation of bimetal ic 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 (ICP-AES). 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 excel ent performance at 40 °C 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 bimetal ic al oys, rather than the electronic effects, since no electron transfer occurred between Pd and Cu.
展开▼
