Key Applications and Potential Limitations of Ionic Liquid Membranes in the Gas Separation Process of CO ₂, CH ₄, N ₂, H ₂ or Mixtures of These Gases from Various Gas Streams

Abstract

Heightened levels of carbon dioxide (CO ₂) and other greenhouse gases (GHGs) have prompted research into techniques for their capture and separation, including membrane separation, chemical looping, and cryogenic distillation. Ionic liquids, due to their negligible vapour pressure, thermal stability, and broad electrochemical stability have expanded their application in gas separations. This work provides an overview of the recent developments and applications of ionic liquid membranes (ILMs) for gas separation by focusing on the separation of carbon dioxide (CO ₂), methane (CH ₄), nitrogen (N ₂), hydrogen (H ₂) _, or mixtures of these gases from various gas streams. The three general types of ILMs, such as supported ionic liquid membranes (SILMs), ionic liquid polymeric membranes (ILPMs), and ionic liquid mixed-matrix membranes (ILMMMs) for the separation of various mixed gas systems, are discussed in detail. Furthermore, issues, challenges, computational studies and future perspectives for ILMs are also considered. The results of the analysis show that SILMs, ILPMs, and the ILMMs are very promising membranes that have great potential in gas separation processes. They offer a wide range of permeabilities and selectivities for CO ₂, CH ₄, N ₂, H ₂ or mixtures of these gases. In addition, a comparison was made based on the selectivity and permeability of SILMs, ILPMs, and ILMMMs for CO ₂/CH ₄ separation based on a Robeson’s upper bound curves.