Improved thermal stability of mesoporous molecular sieves by vapor infiltration treatment

A mesoporous silica has been prepared by base-catalyzed hydrolysis and polymerization of silicate ions followed by a vapor infiltration (VI) treatment using tetraethoxysilane (TEOS). X-ray diffraction analyses suggested that the VI-treated mesostructured silica did not contract during calcination, showing high structural stability. Fourier-transform infrared spectroscopy studies confirmed that a high density of surfactant molecules remained inside the pores during the VI treatment. The pore wall density increased after the VI treatment. The change in weight of mesostructured silica under VI treatment, and nitrogen adsorption/desorption studies, demonstrated that TEOS molecules penetrated into originally deposited silicate but did not deposit on the outer surface of particles and inside the pores. The denser pore wall of the VI-treated mesostructured silica has a high structural stability and hardly contracts under calcination. This post-synthesis method provides good support for the preparation of mesoporous silica with high structural stability and can also be applied to film preparation. (C) 2003 Elsevier Inc. All rights reserved.