Preparation and characterization of polyimide–silica hybrid membranes on kieselguhr–mullite supports

Two types of supported polyimide–silica hybrid membranes were prepared from polyamic acid (PAA) and different silicon sources by sol–gel technique. Their surface morphologies, surface structures, thermal performances and gas permeabilities were characterized by methods of scanning electron microscopy (SEM), infrared (IR) spectroscopy, thermogravimetric analysis (TGA) and gas permeability measurement. The results showed that the silica particles are finely dispersed in polymers. The phase separation phenomena can be observed and there are bond-linking between minerals and polymer phases. The glass transition temperature (Tg) of hybrid membrane materials increases with the increasing of silica content. With the same silica content, Tg is more greatly affected by T series hybrid membrane materials prepared in acidic condition than that by S series ones prepared in basic environment. Hybrid membranes have excellent gas permeabilities and hydrophilic properties. The separation factors of H2O/N2 and H2O/CH4 are 27.86 and 16.77 for T membrane, 25.85 and 15.57 for S one, which are all higher than that of polyimide membrane.