Synthesis and characterization of new silica membranes using template–sol–gel technology

The sol–gel polymerization process and template technology were used to prepare silica–alumina asymmetric membrane. The FTIR and 29Si-NMR results showed that the silica polymers were formed and the degree of branching depended on the aging time of polymeric sols. Silica membranes were characterized using DTA, TGA, SEM and EDX techniques. Nitrogen physisorption tests revealed that the surface area of the membrane increases significantly around 10-folds when template is used. The average pore size of the silica membrane increases by a factor of 1.5–3 when a template is added. Changing the type and concentration of template, as well as molar ratio of the precursors alter the final characteristics of the membrane. The permeation data on alumina support showed that the gas permeation through the support was controlled by viscous flow model. The H2H2 permeance of free surfactant template membrane (2.09×10-6mol/m2sPa) was increased approximately 2 times for new templated membrane (4.2×10-6mol/m2sPa) at 400∘C. Permselectivities of H2/CH4H2/CH4 (149) and H2/CO2H2/CO2 (15.5) were obtained for free template membrane and 135 and 35, respectively, for templated membrane at 400∘C.