Density and viscosity study of pyridinium based ionic liquids as potential absorbents for natural refrigerants: Experimental and modelling

In this work, density and viscosity of two pyridinium based ionic liquids; 1-ethylpyridinium bis(trifluoromethylsulfonyl)imide, [C2py][NTf2], and 1-ethylpyridinium triflate, [C2py][OTf] as well as [C2py][OTf] + H2O mixtures have been studied from experimental and theoretical point of view. Density and viscosity were measured, at several temperatures and atmospheric pressure. A linear equation and Vogel–Fulcher–Tammann equation correlated successfully density and viscosity behaviour. Coefficient of thermal expansion of pure ILs and their mixtures with water together with the excess molar volume and viscosity deviation of mixtures were also calculated. Excess molar volumes and viscosity deviations were described using a Redlich–Kister equation. Regarding to theoretical approach, PC-SAFT was used to model volumetric behaviour whereas Hard Sphere theory was used to study viscosity. The obtained results for pure ILs are satisfactory for both models, but for [C2py][OTf] + H2O mixtures the deviations are higher.