二氧化铈对贵金属加氢脱硫催化剂的改性作用

采用浸渍法制备了CeO_2改性的Ru/Al_2O_3、Pd/Al_2O_3加氢脱硫催化剂,分别考察了硫化态和还原态贵金属催化剂对噻吩加氢脱硫反应性能的影响,并运用XRD、TPR、TPR-S等手段对催化剂进行表征。结果表明,CeO_2的改性导致还原态Pd/Al_2O_3催化剂初始活性提高了26%,但硫化态Ru/Al_2O_3催化剂活性下降。CeO_2对Pd/Al_2O_3催化剂的改性机理在于Pd与Ce发生了强相互作用,所生成的Ce~(3+)成为了新的不同于B酸的噻吩吸附活化中心。而在Ru/Al_2O_3中,CeO_2增强了Ru-S键,导致活性中心硫空穴的减少。

EFFECT OF CERIA ON NOBLE METAL CATALYSTS FOR HYDRODESULFURIZATION

CeO_2 promoted palladium and ruthenium catalysts supported onγ-Al_2O_3 were prepared by an impregnation method and the activities on thiophene hydrodesulfurization were determined.XRD, TPR,TPR-S were used to characterize the catalysts.The result indicated that CeO-2 had remarkably positive promotion effect on the reduced state of Pd catalysts,with the activity increased by 26%in the thiophene HDS reaction,but decreased the activity of the sulfided Ru catalyst.The function of CeO_2 lies on the interaction between Pd and cerium,with the produced Ce~(3+) being the new adsorptive and active sites of thiophene,different with the BrΦnsted acid.In Ru/Al_2O_3,CeO_2 strengthened Ru—S bond,resulting in the decrease of S vacancies in the active centers.