EXAFS Studies of Supported Bimetallic Cluster Catalysts

Bimetallic cluster catalysts represent an important class of materials in the field of catalysis from both a fundamental and technological point of view. Significant interest in these systems resulted from the demonstration that various combinations of metals, even pairs which were not miscible in the bulk, produced substantial alterations in the selectivity of competing chemical reactions. Thus, one of us (JHS) [1] showed that the addition of copper to ruthenium and osmium resulted in an increase in the cyclohexane dehydrogenation to benzene relative to hydrogenolysis to methane. This observation stimulated considerable activity in the field since it offered the hope that catalytic structures could be fabricated that produced selective reaction path-ways for complex systems. Technological implementations of bimetallic catalysts have occurred in the petroleum industry in at least two instances, both related to the reforming of hydrocarbons for motor fuel. Thus, supported catalysts based on Re-Pt [2] and Ir-Pt [3,4] are in commercial use in petroleum refineries in place of supported Pt catalysts because of improvements in activity, yield, product distribution, and catalyst activity maintenance.