The strategies of molecular architecture and modification of polyimide-based membranes for CO₂ removal from natural gas-A review

Efficient separation technologies are required for the removal of carbon dioxide from natural gas streams. Membrane-based natural gas separation has emerged as one of the fastest growing technologies, due to the compactness, higher energy efficiency and economic advantages which can be reaped. However, the inadequacy of the existing polymeric membrane materials hinders the full exploitation of the application opportunities on the industrial scale. The two important identified challenges are: (1) achieving good gas selectivity without sacrificing gas permeability and (2) maintaining the long-term gas separation performance by overcoming the problems of aging and plasticization. In this article, an overview of the natural gas treatment is presented. Following which, the prevalent mechanisms for the transport of the gas molecules through glassy polyimide membranes are briefly discussed. The recent developments in polyimide molecular design and modification for the separation of carbon dioxide from natural gas are examined. In the light of the anticipated marked role of polyimides as eminent materials for natural gas purification, the future research directions to overcome the challenges are proposed.