ALUMINA-SILICA AEROGEL CATALYSTS PREPARED BY 2 SUPERCRITICAL DRYING METHODS FOR METHANE COMBUSTION

Palladium-supported alumina-silica (10 mol %) aerogels were prepared by two different supercritical drying methods. In one method, an alumina-silica wet gel was dried under supercritical conditions of ethanol in an autoclave at a temperature of 270 degrees C and pressure of 26.5 MPa. In the other, ethanol was supercritically extracted by carbon dioxide in an extractor at 80 degrees C and 15.7 MPa. Their catalytic properties for methane combustion were measured after being fired at 1200 degrees C for 5 h. The palladium-supported alumina-silica aerogels prepared in the autoclave showed higher activity (methane conversion) than the one prepared in the extractor. This was attributed to the autoclave-dried aerogel having a larger pore size and better palladium dispersion.