Membrane technology is a green technology possessing a number of advantages over conventional gas separation technologies i.e. absorption, adsorption and cryogenic process. At present, membranes materials are made from polymeric and inorganic membranes on the basis of materials. The polymeric membranes dominate the market, and they are widely used in natural gas processing, especially for carbon dioxide removal from natural gas. Due to the upper bound trade-off between permeability and selectivity, plasticization, and physical aging problems, the polymeric membranes have reached a saturation level, where no further improvement is observed over the past two decades. Therefore, enhanced polymeric membranes were synthesized by the incorporation of amines and ionic liquids in the membrane matrix to facilitate the removal of carbon dioxide from natural gas. These membranes exhibited an outstanding separation performance; however, the mechanical strength was sacrificed due to softening of the polymer matrix. On the other hand, inorganic membranes demonstrate superior separation properties as compared to the polymeric membranes, but the commercialization and industrial application of inorganic membranes is restricted by the high cost of production, the inadequate technology to develop defect free and continuous membranes, and the handling issues e.g. brittleness. The combination of polymer phase and inorganic phase in a single membrane matrix is known as mixed matrix membrane (MMM), which is an emerging area of research, and provides the superior separation performance of CO₂/CH₄ over the polymeric membranes due to the presence of inorganic fillers, and ease of processing and handling due to the flexibility of polymeric materials. However, interfacial defects in MMMs are the key challenges in the commercialization of MMMs. The upper bound challenge in polymeric membranes, loss of mechanical strength in enhanced polymer membranes, and interfacial defects in MMMs can be addressed by the combination of polymer, filler and additive (ionic liquids or amines) in a single membrane matrix known as enhanced mixed matrix membrane (E3M). Therefore, E3Ms were synthesized by using a variety of fillers such as zeolites, carbon molecular sieves, titanium dioxide, and silica nanoparticles. This concept not only eliminated the interfacial defects of MMMs, but also enhanced the separation performance of CO₂/CH₄ by E3Ms beyond Robeson upper bound trade-off between permeability and selectivity. The issues and challenges in the commercialization of enhanced polymeric and E3Ms were also identified and highlighted.

Keywords:

Methane, Carbon dioxide Separation, Polymer Membrane, Mixed Matrix Membrane, Enhanced Mixed Matrix Membrane