Effect of Water on the Densities and Viscosities of Some Ionic Liquids Containing a Phosphonium Cation

A small amount of water can significantly decrease the viscosity of an ionic liquid. From 25–80 ºC, densities and viscosities were measured for dilute solutions of water in six ionic liquids: trihexyltetradecylphosphonium bis (2,4,4-trimethylpentyl) phosphinate, trihexyltetradecylphosphonium dicyanamide, tributyltetradecylphosphonium dodecylbenzenesulfonate, 1-ethyl,3-methylimidazolium bis(triflouromethylsulfonyl)imide, methyltrioctylammonium bis(trifluoromethylsulfonyl)imide, and triisobutylmethylphosphonium tosylate. At 25 ºC, when the water content is about 1 wt. %, the viscosity of a phosphonium-based ionic liquid is reduced by nearly one order of magnitude.