Pd/Al2O3催化过氧化氢异丙苯的液相加氢反应

 分别以K₂[PdCl₄]和K₂[PdCl₄]与草酸的混合液为Pd前驱体，采用浸渍沉淀法制备了Pd/Al₂O₃催化剂。采用等离子体耦合发射原子吸收光谱(ICP-AES)、透射电镜(TEM)、程序升温还原(TPR)等手段对Pd/Al₂O₃催化剂进行了表征。考察了Pd/Al₂O₃催化剂在过氧化氢异丙苯(CHP)固定床加氢反应中的催化活性。结果表明，金属Pd在载体Al₂O₃上呈不均匀分布，并发生团聚，其颗粒直径为5～10nm；催化剂在煅烧及还原过程中，活性金属Pd与载体Al₂O₃发生强烈相互作用，产生了Pd-Al合金。以K₂[PdCl₄]为前驱体制备的Al₂O₃催化剂在过氧化氢异丙苯(CHP)固定床加氢反应中显示了较高的二甲基苄醇(CA)选择性，而且在240 h 连续反应过程中，CHP的转化率始终维持在100%，目标产物CA的平均选择性也达到了97.7%。通过对比反应前后反应体系的组成，探讨了CHP液相催化加氢制备CA的反应途径。

CATALYTIC HYDROGENATION OF CUMENE HYDROPEROXIDE OVER Pd/Al_2O_3CATALYST

Two Pd/Al_2O_3 catalysts were synthesized by using K_2[PdCl_4] and a mixture of K_2[PdCl_4] and oxalic acid as precursors, respectively.The samples were characterized by means of inductively coupled plasma atomic emission spectroscopy (ICP-AES), transmission electron microscopy (TEM) and temperature-programmed reduction (TPR).The catalytic activities of the samples were tested in the transformation of a-cumyl alcohol (CA) from cumene hydroperoxide (CHP) in cumene solution with hydrogen as a reducing agent in a fixed bed reactor.The results showed that the Pd particles loading on the alumina were misdistribution and agglomeration with a mean particle diameter of about 5 - 10 nm, and Pd-Al alloy was formed in the treatments of calcinations and reduction due to the strong interaction between Pd and Al_2O_3.The CHP conversion of 100% and the mean CA selectivity of 97.7% were obtained, respectively, in 240 h CHP hydrogenation over Pd/Al_2O_3 prepared from K_2[PdCl_4].Meanwhile, reaction pathways of catalytic hydrogenation of CHP in cumene solution over Pd/Al_2O_3 were also discussed on the basic of analyzing and comparing the compositions of the system before and after reaction.