(492b) Synthesis of Hydrothermally Stable Silica-Niobium Oxide Catalysts
A significant challenge encountered with aqueous phase reactions for the production of biorenewable chemicals is the development of hydrothermally stable catalysts that maintain surface area and prevent aggregation of the support. We have synthesized a hydrothermally stable, bifunctional niobia catalyst by incorporation of 5 wt% silica in the niobia framework using a surfactant templating approach. Catalytic performance of the material was studied by impregnating Pd on the niobia-silica support for the aqueous phase transformation of γ-valerolactone (GVL) to pentanoic acid at 573 K and 35 bar. In this reaction, catalyst deactivation was caused by the sintering of Pd particles due to the loss of surface area of the support. A 53% decrease in catalytic activity was observed for Pd supported on commercial niobia, HY-340, whereas the synthesized Pd/niobia-silica catalyst showed higher stability with only a 19% loss of activity for the conversion of GVL to pentanoic acid. N2 physisorption and TEM were used to study the structure of the metal oxide after exposure to reaction conditions. These results have allowed us to develop new strategies for the synthesis of high surface area oxide catalysts that are stable in liquid water at 473 K, leading to a material that shows a surface area of 350 m2/g under these conditions.