Surface Properties of the System SiO2-Al2O3 prepared by the Hydrolysis of Metal Alkoxides

The mixtures of aluminum s-butoxide and silicon ethoxide in different molar ratio were hydrolyzed in aqueous alcohol. The precipitates were dried, and the growth and transformation of the crystals at calcination were estimated by X-ray diffractometry. The surface properties of the oxide powder were studied by means of the heats of immersion and the adsorption of nitrogen, water vapor and ammonia. The samples calcined at 500°C have surface areas 260–600 m2/g. Heats of immersion and surface hydrophilicity with respect to the composition, from pure silica gel to pure alumina, have a fairly good resemblance to each other, but this is not found between the heats of immersion and surface acidity.