Catalysis by transition metal sulfides: A theoretical and experimental study of the relation between the synergic systems and the binary transition metal sulfides

Abstract

Both a systematic experimental study of the promoting effect of the first row transition metals on the hydrodesulfurization (HDS) activity of MoS 2 and a systematic theoretical study of the electronic structure of simple clusters which model these catalyst systems have been carried out. A comparison of measured trends in activity with calculated trends in electronic structure makes it possible to establish an electronic basis for the 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 which related particular electronic factors to the HDS activity of binary sulfide catalysts.