Hydrolysis of Magnesium Methoxide. Effects of Toluene on Gel Structure and Gel Chemistry

Abstract

The hydrolysis of magnesium methoxide in methanol or methanol−toluene solvents with a water-to-methoxide molar ratio of 2 has been studied. The gel obtained from the hydrolysis of magnesium methoxide appears to be polymeric based on the mass fractal dimensions and TEM micrographs. The presence of toluene accelerates the hydrolysis and gelation processes. The fractal dimensions of the wet gels obtained in the absence and in the presence of toluene were 2.22 and 1.80, respectively. Both of these observations indicate that the presence of toluene changes the fractal growth from a reaction-limited to a diffusion-limited growth. In either case, the hydrolysis is only completed partially and produces an intimate gel of MgO−Mg(OH)2−Mg(OH)(OCH3). The N2 BET surface area of the dry gel, obtained with a toluene to methanol volume ratio of 1.60, is 1011 m2/g, which is 1.74 times as large as that of the gel obtained in the absence of toluene.