Membranes are a promising technology for bulk CO₂ separation from natural gas mixtures due to their numerous advantages. Despite the numerous fundamental studies on creating better quality membrane efficiency, scaling up the research work for field testing requires huge efforts. The challenge is to ensure the stability of the membrane throughout the operation while maintaining its high performance. This review addresses the key challenges in the application of polymeric technology for CO₂ separation, focusing on plasticization and aging. A brief introduction to the properties and limitations of the current commercial polymeric membrane is first deliberated. The effect of each plasticizer component in natural gas towards membrane performance and the relationship between operating conditions and the membrane efficiency are discussed in this review. The recent technological advancements and techniques to overcome the plasticization and aging issues covering polymer modification, high free-volume polymers, polymer blending and facilitated transport membranes (FTMs) have been highlighted. We also give our perspectives on a few main features of research related to polymeric membranes and the way forwards. Upcoming research must emphasize mixed gas with CO₂ including minor condensable contaminants as per real natural gas, to determine the competitive sorption effect on CO₂ permeability and membrane selectivity. The effects of pore blocking, plasticization and aging should be given particular attention to cater for large-scale applications.

Membranes with a stable performance during the natural gas sweetening process application are highly demanded. This subject has been immensely explored due to several challenges faced by conventionally used polymeric membranes, especially the high tendency of plasticization and physical aging. In this study, polysulfone (PSf) hollow-fiber membrane was formulated and tested for its application in natural gas sweetening based on several compositions of CO₂/CH₄ mixed gas. The effects of operating conditions such as pressure, temperature and CO₂ feed composition on separation performance were analyzed. The findings showed that the formulated membrane exhibited decreasing CO₂ permeation trend with the increase in pressure. Conversely, the increase in operating temperature boosted the CO₂ permeation. High productivity can be attained at higher operating temperatures with a reduction in product purity. Interestingly, since PSf has higher plasticization pressure, it was not affected by the change in CO₂ percentage up to 70% CO₂. The experimental study showed that the membrane material formulated in this study can be potentially evaluated at the field stage. Longer testing duration is needed with the real feed gas, appropriate pre-treatment based on the material limitations, and optimum operating conditions at the site to further confirm the membrane’s long-term lifetime, resistance, and stability.

Membrane contactors allow for higher mass transfer per unit volume. Hence, there has been great interest in recent years on its development and applications in separation processes. It offers high interfacial area between liquid and gas phases while preventing direct mixture, and concurrently prevents flooding and foaming, thanks to the independent gas and liquid flow rates. However, wetting of the membrane pores is a serious problem for this technology application, where even partial membrane pores wetting could significantly deteriorate contactor performance. Therefore, it is crucial that the membranes are hydrophobic to maintain membrane nonwetting during operation. Moreover, any membrane surface modification to increase its hydrophobicity must also be highly stable, does not leach out, and can be applied for long-term operation. This chapter looks at the research done on superhydrophobic membranes for gas-liquid membrane contactor application and its recent advances.