Sorption Studies of Microporous Sol-Gel Modified Ceramic Membranes

Sorption experiments with H-2, CO2, CH4 and iso-C4H10 were performed on microporous SiO2 and SiO2/TiO2 (30 mol% TiO2) non-supported membrane top-layers using volumetric and gravimetric techniques. For silica, the sorption capacity decreases in the order CO2 > iso-C4H10 > CH4 > H2 at temperatures < 373 K. The isosteric heat of adsorption q(st) is 23, 24, 10 and 6 kJ.mol(-1) for respectively CO2, iso-C4H10, CH4 and H-2. The sub-atmospheric adsorption isotherms are of Henry-type for temperatures equal and higher than 348 K for CO2, temperatures higher than 373 K for iso-C4H10, temperatures equal and higher than 194 K for H-2 and for temperatures equal and higher than 273 K for CH4. The sorption capacity for the SiO2/TiO2 sample was only slightly lower than for silica, as may be expected due to the lower porosity.