Novel Index to Screen and Evaluate Ionic Liquids for CO2/CH4 Separation

Efficient CO2/CH4 separation for biogas upgrading can be achieved by using ionic liquids (ILs) as absorbents. In this study, a novel index named “relative absorption ability” (RAA) was proposed for the first time to facilitate the screening and evaluation of potential absorbents based on their thermodynamic and kinetic properties for CO2/CH4 separation. Subsequently, the properties of 2009 ILs were predicted with the conductor-like screening model, and the top 10 ILs were screened. Finally, the cost of the screened top two ILs for CO2/CH4 separation was further estimated with process simulation. The results further prove the reliability of the new proposed RAA index in screening and evaluating, and the screened promising ILs can reduce the costs of CO2/CH4 separation by 53.9% and 51.9%, respectively, in comparison to the current commercial technology.