(536c) Sintering and Reactivity Studies on Au Catalyst Supported on Aerosol-Derived Spherical Mesoporous Silica Substrates

Spherical mesoporous silica particles prepared by evaporation induced self assembly (EISA) have a unique internal architecture of coiled hexagonally ordered pores, with no obvious termination of the pores on the external surface. The EISA method, when used with aerosols, can produce highly ordered mesostructured silica particles with a total process time of only several seconds or less. The process is a continuous scaleable process that can make particles over a fairly wide size range. Particles produced are generally spherical, and provide for uniform incorporation into every particle of any chemical species that can be dissolved or dispersed into a precursor solution or dispersion. The curved pores of the aerosol silica provide a unique geometry with the Au nanoparticles protected inside thin silica walls. Curved pores were found to be more effective in controlling sintering than the straight pores in MCM-41 type mesoporous materials. The thin silica walls allow the transport of gas phase molecules while retaining the catalyst. The permeability to gases makes these spherical silica particles especially suitable for gas phase catalytic reactions. The incorporating of a monolayer of titanium dioxide (TiO2) on the inner pore structure of the silica particles significantly increased the CO oxidation reactivity and the stability of the Au nanoparticles. The mechanism by which the TiO2 increases the stability of Au nanoparticles will be investigated by measuring the wettability and vapor pressure of gold on SiO2.