Catalyst activity of alumina-galia aerogels for selective reduction of NOx

Alumina gels are known to be good catalysts for the selective reduction of NO, using hydrocarbon under an oxidizing atmosphere. The effects of galia-a ddition on the microstructure and catalytic activity of alumina aerogels we re investigated. Aerogels containing 0-66 wt% Ga2O3 were prepared by hydrol yzing Al(sec-C4H9O)(3) (ASB) in an ethanol solution, adding Ga(NO3)(3) diss olved in H2O, followed by supercritical drying. The catalytic activity of a erogel catalysts containing 38-51 wt% Ga2O3 was higher than pure alumina at low temperatures, 450-550 degreesC, but decreased when the Ga2O3 content w as 66 wt%. The amount of desorbed NH3, which is related to the catalytic ac tivity, increased with increasing Ga2O3 content, but the fraction of mesopo res, 20-30 nm in diameter, decreased when Ga2O3 content > 60 wt%. These res ults show that changes in the gel microstructure caused by Ga2O3 addiction affect the catalytic activity. (C) 2001 Elsevier Science B.V. All rights re served.