Simultaneous capture of acid gases from natural gas adopting ionic liquids: Challenges, recent developments, and prospects

The impurities CO2 and H2S in natural gas (NG) are recognized as major contaminants that exacerbate economic, operational, and environmental losses. Generally, these undesirable impurities are removed using well-established amine-based absorption methods. However, typical methods in this category are cost-intensive, primarily due to their high operating and maintenance costs. The ionic liquids (ILs) are emerging as alternative solvents owing to their lower regeneration costs and non-flammable nature. However, ILs could not attain a significant attention from practitioners due to the lack of effective communication between industry and academia. In this context, a comprehensive review and analysis of specific ILs that can simultaneously remove H2S and CO2 is proposed. This article highlights the major challenges and issues associated with various acid gases removal approaches, particularly IL-based absorption techniques. Recent developments toward solving the major issues associated with absorption using ILs are assessed to highlight areas for further improvement. The acid gas solubility data for ILs are analyzed to evaluate the feasibility and associated major constraints for large-scale process designs using commercial process simulators. Furthermore, the fundamentals for the process systems engineering-based investigations using ILs are also highlighted and evaluated. This study concludes that ILs have the potential to completely replace conventional solvents, have synergistic effects in terms of energy savings, and provide feasible solutions to maintenance-related issues.