Chevrel Phase HDS Catalysts: Structural and Compositional Relationships to Catalytic Activity

The catalytic activities of “reduced” molybdenum sulfides, known as Chevrel phases, have been evaluated for hydrodesulfurization of thiophene and benzothiophene and hydrogenation of 1-butene. These materials have been found to have hydrodesulfurization activities comparable to or greater than model unpromoted and cobalt-promoted MoS₂ catalysts; in contrast, Chevrel phases exhibit low activities for 1-butene hydrogenation. In this paper, a general discussion of the relationship between the solid state chemistry of Chevrel phases and their catalytic activity is presented. Structural properties appear to be an important factor: large cation Chevrel phases are the most active and stable materials. It is also likely that the most active phases resist surface oxidation which may occur if the ternary metal components undergo surface migration. “Reduced” molybdenum oxidation states are associated with the active sites, in direct analogy with conventional catalysts.