Synthesis and surface characteristics of silica- and alumina-carbon composite xerogels

Silica- and alumina-carbon composite xerogels were obtained by the sol-gel method and carbonization of the product obtained at 773 and 1173 K in inert atmosphere. Samples so obtained were characterized by CO2 adsorption at 27 3 K and by mercury porosimetry, X-ray diffraction and scanning electron mic roscopy. With these techniques the surface area and porosity of the samples were determined, as well as the nature of the inorganic component of the c omposite and the morphology of the surface. The acid-base surface character istics of the samples were studied by the decomposition reaction of isoprop anol. The Al2O3-containing samples had more developed meso- and macroporosi ty than the SiO2-containing ones. The surface areas obtained for the carbon ized derivatives varied between 300 and 400 g(-1). Alumina-carbon composite xerogels were much more acidic than the silica-carbon composite xerogels. Due to this difference, the electronic interaction between the carbonaceous component, with basic character, and the alumina in the composite xerogels caused a decrease in the total surface acidity of the composite. This elec tronic interaction increased with the treatment temperature.