Isobaric (vapor + liquid) equilibria of 1-ethyl-3-methylimidazolium ethylsulfate plus (propionaldehyde or valeraldehyde): Experimental data and prediction

This paper reports the density, refraction index, and (vapor + liquid) equilibria (VLE) for binary systems {aldehyde + 1-ethyl-3-methylimidazolium ethylsulfate ([emim][EtSO4])}: {propionaldehyde + [emim][EtSO4]} and {valeraldehyde + [emim][EtSO4]}. The uncertainties for the temperature, pressure, and compositions measurements for the phase equilibria are ±0.1 K, ±0.01 kPa and ±0.0004, respectively. A qualitative analysis of the variation of the properties with changes in solvent and temperature was performed. The Peng–Robinson equation of state (PR EoS), coupled with the Wong–Sandler mixing rule (WS), is used to describe the experimental data. To calculate activity coefficients we used three different models: NRTL, UNIQUAC, and COSMO-SAC. Since the predictive liquid activity coefficient model COSMO-SAC is used in the Wong–Sandler mixing rule, the resulting thermodynamic model is a completely predictive one. The prediction results for the density and for the (vapor + liquid) equilibria have a deviation lower than 2.3% and 1.6%, respectively. The (vapor + liquid) equilibria predictions show a good description for the propionaldehyde system and only a qualitative description for the valeraldehyde system.

Research highlights
► We report density, refraction index, and VLE for (propionaldehyde or valeraldehyde) + [emim][EtSO4].
► The Peng -Robinson + Wong -Sandler + COSMO-SAC model was used to predict density and VLE.
► The densities were predicted with deviations below than 2.3%.
► The experimental VLE was predicted with deviations below than 1.6%.