UNIFAC parametrization for solid-liquid equilibrium of systems containing choline chloride

Choline chloride has been extensively used in literature for the formulation of eutectic solvents for the extraction of biocompounds from different raw materials. The formulation of eutectic solvents should be performed through the evaluation of the Solid-Liquid Equilibrium (SLE) of the mixture and identification of its eutectic point. In this case, the eutectic point calculation through thermodynamic modeling could improve the design of solvents for extraction processes. The UNIFAC model is a group-contribution based model that could be used in this case. In this context, this study was aimed at the adjustment of new original UNIFAC interaction parameters pairs (a_mnand a_nm) for choline chloride [Ch]Cl (treated in this work as a pseudo-group) and CH₃ (CH, CH₂ and CH₃ subgroups), OH and COOH groups. A databank composed of experimental SLE data from different works in literature were built. The dataset included complete SLE data of 23 mixtures of [Ch]Cl with polyols, polycarboxylic acids, long-chain carboxylic acids (fatty acids) and long chain alcohols (fatty alcohols). Parameters adjusted showed a significant accuracy in describing the SLE profile of the mixtures, especially in the [Ch]Cl rich region, with mean relative deviation varying from 1.32 to 10.79 %. The new UNIFAC enthalpic parameters were also able to predict eutectic temperatures and eutectic compositions of [Ch]Cl mixtures with reasonable accuracy, which is quite interesting considering the design of new eutectic solvents. This study collaborates with the green chemistry literature taking into account the faster screening of new DES and ES composed of choline chloride.