Process of producing a microporous hydrophobic inorganic membrane

Microporous hydrophobic inorganic membrane having an average pore size of less than 2 nm and a hydrophobicity index octane/water of at least 2 can be obtained by a process comprising hydrolyzing a metal alkoxide in the presence of a hydrocarbyl metal alkoxide having at least one non-hydrolyzable group in an organic solvent to produce a metal (hydr)oxide sol, and precipitating metal (hydr)oxide from said sol and drying the precipitate. In this process, at least 50% of the amount of hydrocarbyl metal alkoxide is introduced into the solvent after 20% of the hydrolysis period has lapsed.