A study of polyaniline membranes for gas separations

Membrane based gas separations are proven to be technically attractive because of their simplicity and low energy costs, although they are often limited by insufficient flux, selectivity and stability. During the past thirty years, major developments in this technology have been made by developing high flux asymmetric membranes, and large surface area membrane modules. Today, in the present market, the sales of the membrane gas separation equipments have grown to become a $150 million per year business, and substantial growth in the near future is likely. More than 90% of membrane gas separation business involves the separation of non-condensable gases, i.e. nitrogen from air, carbon dioxide from methane, and hydrogen from nitrogen, argon, or methane. However, a large potential market for membrane gas separation lies in refineries. The separations of hydrogen/hydrocarbon and olefin/paraffin are regarded as import processes (although challenging ones) in the petrochemical industry. The membrane based separation p~ocess to sepfirate olefins from paraffins is likely to be developed to the commercial state in the next few years. Industry's demands for increasing the separation effectiveness and productivity have encouraged conducting research into development of new membrane materials. Polyaniline is regarded as so far the best alternative for gas separations, since the molecular spacing of polymer chains can be controlled by its interesting doping/dedoping chemistry. A novel method to make reproducible defect-free dense self-supported polyaniline films with the thicknesses between 2 and 6 IJm, and polyaniline nanofilm membranes with selective polyaniline layer thicknesses between 300 and 800 nm supported on a porous polyvinylidene fluoride (PVDF) substrate is developed. (Continues...).