Solubilities of Hydrocarbons and Less Soluble Gases in Pure Ionic Liquids: A Mini Review

This paper reviews the solubility of small hydrocarbons, carbon monoxide, as well as other unreactive gases in organic solvents and ionic liquids. Obviously, these nonpolar gases are favorable for ionic liquids with a highly nonpolar field and long aliphatic alkyl chains, such as P6 6 6 14TMPP. Electrostatic interactions between anions and gases make a major contribution to gas dissolution in ionic liquids. Anions with multiple fluorine atoms generally show superior gas solvationthan anions with other functional groups. Weak steric hindrance is also very essential during the design of suitable ionic liquids for the physical absorption of nonpolar gases. Importantly, a statistical analysis of gas-ionic liquid systems shows an inverse temperature dependence of solubility at higher temperature stages, and it is found that gases with lower critical temperatures are more likely to be absorbed during higher temperature stages. Consequently, low temperatures have a positive effect on separating CH4 from CO, Ar, O2, H2, and N2.