Pd-CeO_2/Al_2O_3结构对其催化加氢脱硫反应性能的影响

Effects of Pd-CeO_2/Al_2O_3 structure on its catalytic performance in hydrodesulfurization

分步浸渍法制备了不同Pd含量的Pd-CeO2/Al2O3催化剂,以噻吩加氢脱硫为探针反应,考察了Pd-CeO2/Al2O3催化剂的加氢脱硫性能,并应用XRD、H2-TPR、NH3-TPD、H2吸附和CO吸附等手段对催化剂结构进行了表征。结果表明,Pd在制备过程中优先沉积在CeO2表面,Pd-Ce结合作用导致了界面效应和新的酸性位产生,Pd-Ce之间的界面效应是Pd-CeO2/Al2O3催化剂加氢脱硫活性提高的原因。2%Pd的Pd-CeO2/Al2O3催化剂拥有最高的单位质量Pd上的界面酸量,改性效果最为明显。Pd颗粒的优势面是Pd(111)面,这导致了强的Pd-Ce结合作用和界面效应,而1%和4%Pd的Pd-CeO2/Al2O3催化剂由于Pd-Ce结合的空间结构使界面效应削弱,活性提高不明显。

Pd-CeO2/Al2O3 catalysts with different Pd contents were prepared by stage-impregnation; their performances in hydrodesulfurization （HDS） of thiophene were investigated. XRD, H2-TPR, NH3-TPD, hydrogen and CO chemisorption were used to characterize the catalyst structure. The results show that Pd precursor is deposited favorably on CeO2 surface; new acid sites are produced due to the interface effect from the Pd-Ce interaction. The highest promoting effect of Pd-Ce interaction is observed on the Pd-CeO2/Al2O3 catalyst with a Pd content of 2%, which exhibits highest interface acidic amounts per unit Pd. Pd （ 111 ） face is the predominant face, which brings on the strong Pd-Ce interaction and interface effect. As to Pd-CeO2/Al2O3 catalysts with 1% and 4% Pd content, the space structure of Pd-Ce interaction inhibited the interface effect; hence the promoting effect was not so distinct.