Understanding Syntheses, Structures, and Properties of Heterogeneous Catalysts at a Molecular Level

Brad Chmelka from UCSB

Heterogeneous catalysts exhibit reactivities and/or selectivities that depend strongly on the local compositions and structures near active-site moieties. Such catalytically active species are formed or can be modified during synthesis or subsequent reactor operation. The reactive moieties are generated or influenced by complicated and interrelated physicochemical processes, including precipitation, self-assembly, crystallization, ion-exchange, calcination, reduction, adsorption, and/or surface reactions. These processes and their influences on the resulting catalysts are challenging to elucidate and control, due at least in part to the absence of long-range atomic order and/or complexity of surface interactions. Such processes and features can nevertheless be monitored and understood by combining spectroscopic, scattering, modelling, and macroscopic property analyses to correlate the compositions, structures, and properties of heterogeneous catalysts across multiple length scales. Recent results will be presented on the local compositions, structures, and surface interactions of nano- and mesoporous zeolite catalysts. Our approach takes advantage especially of new methodologies and insights provided by solid-state nuclear magnetic resonance (NMR) spectroscopy. The analyses provide criteria for the rational design and syntheses of heterogeneous catalysts with enhanced transport, adsorption/reaction, or structural properties for diverse engineering applications.