Load Au-pd Bimetallic Catalyst Co Oxidation And Thiophene Hydrodesulfurization Performance Study

The research on supported Au-Pd bimetallic catalysts has been highly desirable for its excellent activity and stability. This thesis investigated the catalysis performance of CO oxidation and hydrodesulfurization (HDS) of thiophene over the bimetallic catalysts. The supports were selected between SiO2 and Al2O3. Various techniques such as XRD, TEM, XPS, TPR, H2 or CO TPD, XAFS were employed to characterize the structure of these catalysts. The main results are summarized as follows:The Au-Pd/SiO2,Au-Pd/Al2O3 catalyst was prepared by incipient wetness method. The effects of calcinations temperature of the catalyst on CO oxidation were shown. The results indicate that the Au-Pd/SiO2 catalyst calcined in air at 673K and Au-Pd/Al2O3 catalyst calcined in air at 473K shows high activity for CO oxidation. The synergetic effect of Pd0, PdO and Au0 phases is responded for the activity.HDS of thiophene over Au-Pd/SiO2 catalysts was studied and effect of various calcination temperature,different gold solution pH value and different Palladium precursors on HDS activity is found. The maximum HDS conversion was reached at calcination temperature of 673 K. Lower activity is found in the catalyst calcined at 723 K or 623 K. The calcined catalysts give higher HDS activities than the reduced catalysts. The promotional effect of Au0 phase in PdO phase with small particle size can enhance the thiophene conversion.The effects of Au-Pd/SiO2 catalyst prepared from different gold solution pH value on HDS activity were studied. The results indicated that the catalyst prepared from gold solution with pH value of 7 gave the best HDS activity of thiophene. It is obtain that Au0 phase is made for high activity other than AuxPdy phase. The effects of Au-Pd/SiO2 catalyst prepared from there different Palladium precursors on HDS activity were studied. The thiophene conversion on catalyst prepared from Pd(NO3)2 solution is higher than the catalyst prepared from Pd(NO3)2 solution which is reduced by alcohol. The results indicated that PdO phase is better than Pd0 phase in improving the HDS activity.The catalytic activity of the bimetallic Au-Pd/SiO2 in the HDS of thiophene revealed a strong synergistic effect between gold and palladium compared to the activity of monometallic catalysts. The stronger resistance to sulfur poisoning of Au-Pd bimetal catalysts with respect to pure palladium catalyst is attributed to the formation of AuxPdy alloy, though it is inactive phase.