Catalysis by Transition Metal Sulfides

Abstract

As supplies of clean petroleum feedstocks dwindle, industry will be called upon to process and upgrade “dirtier” feedstocks. Feedstocks of this type contain large amounts of sulfur and nitrogen which must be removed for utilization and further processing. Catalysts based on transition metal sulfides are currently used for such processes but fall considerably short of requirements for future use. In spite of the importance of these catalysts, little is understood regarding the general fundamental basis for and origin of their catalytic activity. This paper reports some of our recent studies of the fundamental properties of transition metal sulfide catalysts. The primary effect in the hydrodesulfurization (HDS) of dibenzothiophene by transition metal sulfides is “electronic”, i.e. it is related to the position the metal occupies in the periodic table. This effect, which determines the ability of the transition metal sulfides to catalyze the HDS reaction, varies over three orders of magnitude across the periodic table. The first row transition metal sulfides are relatively inactive, but the second and third row transition metals show maximum activity with Ru and Os. A secondary effect in HDS catalysis by transition metal sulfides is “geometric” in origin.