(384c) Stabilization of Porous, High Surface Area, Metastable Oxides at Elevated Temperatures

Metal oxides offer a versatile platform for catalyst design due to their unique surface chemistries, porous nature, and high surface areas. The relatively low surface energies common amongst metal oxides allows them to conform into a diverse range of morphologies with both hierarchical pore size and tunable pore structure. Oxides can be synthesized with tailored pore structures, which span all three porosity regimes (micro, meso, and macropores) through the use of surfactants during soft templating and by hard templating with nano-molds. Unfortunately, the low surface energies which allow such extensive versatility in pore structure also result in increased atomic surface mobility at elevated temperatures; this makes oxides susceptible to sintering, pore collapse, and catalytic deactivation in harsh environments. Thus, it remains imperative to develop methods of oxide stabilization when synthesizing a catalyst for high temperature applications. This work will examine the synergetic stabilization effects that can be achieved by employing surface oxides to stabilize both the surface area and porosity of metastable oxide supports (e.g. zirconia and titania) at high temperatures. Supported oxide systems commonly employed as catalysts and hierarchically porous oxides prepared via a hard templating technique will be examined. HRTEM, XRD, LEIS, and N₂ adsorption are utilized to evaluate the catalytic reconstruction of these systems at elevated temperatures. Both systems presented here are shown to ballast the underlying oxide support while preserving its surface area, porosity, and crystal structure at extreme temperatures. A conceptual framework is provided to explain the preservation of surface area and pore size observed in these systems. This work could lead to the development of more robust, porous, high surface area supported oxide catalysts for use in high temperature applications.