Microporous silica and doped silica membrane for alcohol dehydration by pervaporation

The aim of this work is the development of inorganic membranes that will enable broad application of pervaporation/vapour permeation technology in the chemical industry. This can be achieved by improvement of the existing microporous membranes and the development of new types with enhanced thermochemical stability and separation characteristics. The materials in the system, SiO2–Al2O3–TiO2–ZrO2–MgO, were investigated with respect to their chemical stability and pervaporation performance in alcohol dehydration processes. It was found that, depending on the nature and amount of dopant, composite membranes with improved pervaporation characteristics and chemical stability were obtained.

Mesoporous composite titania/(-alumina layers with mean pore diameters of about 2 nm were prepared. As separative microporous top layer, doped silica layers were deposited on the mesoporous composite layers. Doping silica with zirconium or titanium was seen to lead to a moderate improvement of the chemical stability, while cations with a lower valency led to a reduction of the chemical stability of the silica matrix. Similarly, microporous silica doped with small amounts of zirconium showed improved pervaporation performance compared with undoped silica material. The flux was significantly reduced when Al is present, while other systems showed fluxes similar to silica itself. Further investigations are necessary for better understanding of the effect of doping on microstructure and pervaporation performance.