While phosphonium-based ionic liquids are good solvents for gases, they have high viscosities. Addition of a diluent like dodecane significantly lowers the viscosities of the ionic liquids. In the range 20–90 ℃, viscosities and densities were measured for binary mixtures of dodecane with one of five phosphonium-based ionic liquids: Tributylmethylphosphonium bis(2,4,4-trimethylpentyl)phosphinate [TMPP-PA], Tributyltetradecylphosphonium dodecylbenyzenesulfonate [TTDP-DB], Trimethyloctylphosphonium bis(2,4,4-trimethylpentyl)phosphinate [TMPP-TP], Trihexyltetradecylphosphonium dicyanamide [TTDP-DC], and Trihexyltetradecylphophonium bis(2,4,4-trimethylpentyl)phosphoniate [TTDP-PA]. For every one of these ionic liquids, addition of 10 wt. % dodecane very much reduces the viscosity but slightly reduces the density.
- tetraalkylphosphonium-based ionic liquids