Study of structure-function relationships in platinum-silica catalysts using hydrocarbon hydrogenation as a probe reaction

In the field of heterogeneous catalysis, the relationship between catalyst synthesis and hence structure, and the resulting catalyst activity and selectivity are not well understood. The focus of this work has been to study the structural and catalytic characteristics of eight silica-supported platinum catalysts containing 0.5 wt% platinum. In particular, we wish to identify the specific characteristics of these materials which determine their catalytic behaviour. A further aim is to relate these material properties to the method of catalyst synthesis used. This paper highlights the application of 29Si nuclear magnetic resonance (NMR) and Raman spectroscopies to the characterisation of the hydroxyl and siloxane ring structure environments on the silica surface. We then investigate how these structures are influenced by catalyst synthesis and the role, if any, they play in the activity and selectivity characteristics of the resulting catalysts. Reactor data are reported for ethene and ethyne hydrogenation reactions. The results suggest that while catalytic activity is determined by metal surface area, which is controlled by the method of metal deposition, for both the ethene and ethyne hydrogenations, the selectivity of the ethyne hydrogenation to ethane production appears to correlate with the structure of the silica surface.