Solubilities of Small Hydrocarbons in Tetrabutylphosphonium Bis(2,4,4-trimethylpentyl) Phosphinate and in 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide

Experimental solubilities are reported for methane, ethane, ethylene, and propane in ionic liquid tetrabutylphosphonium bis(2,4,4-trimethylpentyl) phosphinate [P4444][TMPP] from 313 K to 353 K up to 5 MPa. [P4444][TMPP] shows solubilities for methane, ethane, ethylene, and propane that are appreciably larger than those in other typical ionic liquids. However, unlike a hydrocarbon solvent, [P4444][TMPP] is not flammable at ordinary conditions. Unlike other typical ionic liquids, the solubility for ethane is larger than that for ethylene. Because the viscosity of [P4444][TMPP] is high, we consider a low-viscosity diluent. Therefore, experimental solubilities are also reported for the same solutes in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMIM][Tf2N] from 299 K to 354 K up to 4 MPa. Comparison between our results and literature data shows good agreement.