Oxide aerogel catalysts

Abstract

Aerogels and xerogels of TiO 2, V 2O 5, ZrO 2, and Al 2O 3 with and without additives were prepared by hydrolysis of metal alkoxide. The aerogels and the xerogels were obtained by supercritical drying of the wet gels in ethanol and by drying at 90°C for 24 h in air. Catalyst activity of the gels for NO reduction with C 3H 6 were determined at 200–600°C in a fixed bed flow reactor. The highest NO conversion to N 2 was obtained with Al 2O 3 aerogel catalysts, about 80% at 500°C. Al 2O 3–ZrO 2 and ZrO 2 have higher activities at lower temperatures. TiO 2 and V 2O 5 have low activities although they have high oxidation activities. Catalyst activity of aerogels is higher than that of xerogels because of the higher effective diffusivity of reaction gas attributed to the high porosity and larger pore size.