New perspectives in gas separations (CO2/CH4, H2/CH4) using membranes

The rapid development of membrane processes in recent years is due to the push toward more economically and environmentally efficient separation processes. The use of the membrane for wastewater separation and treatment was the result of advances in membrane materials, membrane structure, and large-scale membrane manufacturing methods. To be useful in separation or purification processes, membranes must have a number of characteristics such as high flow, high selectivity, mechanical stability, resistance to fouling, and low cost. The most commonly used membranes are polymeric and nonporous, the separation being based on a solution diffusion mechanism that involves molecular-scale interactions of the permeating molecule with the membrane polymer. Inorganic membranes (molecular sieve zeolite membranes, carbon membranes, alumina membranes, and silica membranes) have high thermal and chemical stability. In recent years, extensive work has been reported on the synthesis, characterization, and application of inorganic membranes. Despite all the advantages, polymer membranes cannot exceed the polymer upper limit between permeability and selectivity. It is desirable to provide a cost-effective alternative membrane in a position above the compromise curves between permeability and selectivity.