Thesis (M.Eng.)--Chulalongkorn University, 1999

Mixtures of alumina isopropoxide (AIP) and tetraethyl orthosilicate (TEOS) in various organic solvents were set in an autoclave and heated at 300 ํC for 2 h. The methods using in the preparation had three types. At the first preparation, toluene was used as the solvent in the beaker and in the gap between the autoclave wall and the beaker. In the second preparation, 1-butanol was used as the solvent instead of toluene. In the third preparation, toluene was used in the beaker and the water was added in the gap between the autoclave wall and the beaker. The fluid phase was removed at the supercritical temperature. The products were calcined in air to yield silica-modified aluminas. These silica-modified aluminas had high thermal stability and maintained large surface area at high temperature. For example, the product prepared from mixture of AIP and TEOS with Al/Si = 8 in 1-butanol had a surface area of 169 m2/g even after the calcination at 1150 ํC. The surface area and thermal stability of products depended on the reaction mechanism operated in each solvent.