SYNTHESIS, CHARACTERIZATION AND GAS PERMEATION STUDIES ON MICROPOROUSSILICA AND ALUMINA-SILICA MEMBRANES FOR SEPARATION OF PROPANE AND PROPYLENE

Microporous silica membranes are known to exhibit molecular sieving ef fects. However, separation of nearly equal sized molecules is difficul t to carry out by size exclusion. Introducing sorption selectivity and keeping the kinetics favourable to facilitate a good contribution of permeation from sorption is a possible solution to enhance selectivity of adsorbing molecules. Results are presented in this paper on the sy nthesis of a microporous silica membrane with commendable permselectiv ity between helium and propylene. Modifications are performed on the m embrane to improve its almost non-selective nature to propylene/propan e mixtures to give practical separation values. Gas separation results on the modified membranes are presented. Surface selectivity on the n ewly added alumina surface layer is identified as the helping mechanis m in realising this separation.