This award in the Inorganic, Bioinorganic, and Organometallic Program provides continued support for research by Dr. M. David Curtis of the Chemistry Department, University of Michigan, on the reactivity of model complexes for dehydrosulfurization (HDS) catalysts. The specific objectives of the project are to determine (1) how the composition, physical and electronic structure, and redox properties of molybdenum or tungsten sulfide clusters correlate with their reactivity toward organic sulfur compounds; (2) the mechanisms of the desulfurization reactions mediated by the metal cluster complexes; and (3) how the mechanisms of desulfurizations on discrete clusters are related to the mechanisms of desulfurization over the heterogeneous HDS catalysts used in the petroleum industry for fuel upgrading. The experimental approaches to these objectives include the synthesis of new sulfide bimetallic clusters, kinetic and structural studies of their reactions with organic sulfur compounds, electrochemical studies, and comparative studies with actual heterogeneous catalysts. Of particular interest are those HDS reactions catalyzed by molybdenum sulfide catalysts `promoted` with iron, cobalt, or nickel and the role played by the promoter metal in increasing the activity of the catalyst. Hydrodesulfurization (HDS) is a commercial process used to remove sulfur from organic materials and is therefore important in manufacturing and to enhancing air quality in industrial areas. In this project, compounds which are models of the industrial catalyst will be prepared and their reactivity investigated. Knowledge of the mechanistic role of the promoter in desulfurization catalysts can be applied to the design of `second generation` hydrotreating catalysts that possess higher activities and selectivities than those currently in use.
