PNNL

Abstract

Ordered mesoporous silica, initially developed in 1992, can be synthesized by using a self-assembly approach: surfactant molecules co-assemble with the inorganic materials into sophisticated nanoscale structures through favorable molecular interactions. The resultant nanoscale materials have extremely high surface area (>1000 m²/g), and highly uniform ordered nanoporosity with tightly controlled pore size and shape. These unique characteristics make the self-assembled nanoporous material an attractive candidate for catalytic applications. Previous work at UC-Berkeley (Iglesia and coworkers) and elsewhere demonstrated that WOx exhibits unique chemical properties for acid-catalyzed reactions. Such catalytic properties are strongly affected by domain size, reducibility, and accessibility of the WOx clusters when supported on conventional refractory metal oxide supports. However, a systematic investigation between the structural and functional relationship in this catalytic system has not been conducted, primarily due to the difficulties in material synthesis with atomic level control, advanced characterization to understand detailed physical and chemical properties, and interpretation and suggestion of mechanisms guided by advanced theory. Mesoporous silica, particularly SBA-15 type silica, provides a chemically inert and thermally stable scaffold for designing WOx type model catalysts with controlled cluster size and spatial dispersion.