The relation between electronic trends and the promoter effect on catalytic activity of hydrodesulfurization catalysts

Abstract

The origin of the promoting effect of certain first-row transition metals on the hydrodesulfurization (HDS) activity of MoS 2 is not well understood. We have carried out a systematic theoretical study of the electronic structure of simple clusters which model these catalyst systems and have used the results of these calculations to establish an electronic basis for the trends in promotion effects observed in the MoS 2 systems. Both Co and Ni, which serve as promoters, have the ability to donate electrons to Mo, while Cu, which serves as a poison, withdraws electrons from Mo. The other first-row transition metals, which have little effect on the HDS activity of MoS 2, do not have the ability to donate to or accept electrons from Mo. Thus promotion is associated with an increase in electron density on Mo while poisoning is associated with a decrease in electron density. These results are consistent with previous results for binary catalysts which related particular electronic factors to the HDS activity of the sulfide.