THE FORMATION OF CHEMICALLY MODIFIED GAMMA-ALUMINA MICROPOROUS MEMBRANES

A technique for the chemical modification of 40-angstrom gamma-alumina membranes with Tridecafluoro-1,1,2,2,-tetrahydroctyl-1-trichlorosilane is presented. The modification is carried out in order to reduce the membrane's pore size so that selective separation of low molecular weight liquid mixtures may be possible. Pure gas permeability measurements with He, H2, Ar, and SF6 are reported for an unmodified and two modified membranes which varied in their reaction times from one day to two weeks. The permeability measurements indicate that the short-term modification produced a membrane that still had an appreciable amount of surface flow, while the membrane modified for two weeks had a hindered surface transport. Also reported are data on the separation of toluene from a high molecular weight (M approximately 660) lube oil. The data indicate an increase in selectivity due to the short-term modification; however, after the two-week modification, the selectivity drops to near unity.