Synthesis, characterization and acid-catalyzed application of ternary deep eutectic solvent: effect of glycerol addition

A ternary deep eutectic solvent was prepared using choline chloride, citric acid and glycerol. The effect of glycerol addition was investigated by means of freezing point, density, viscosity, conductivity, refractive index and pH measurements. Binary and ternary eutectic solvents showed a good catalytic performance in the esterification of acetic acid. For binary eutectic solvent composed of choline chloride and citric acid, acetic acid conversions of 52.46%, 50.00% and 47.86% were achieved at temperatures of 363, 358 and 353 K, respectively. Under the same conditions, the ternary eutectic solvent provided acetic acid conversions of 49.38%, 44.00% and 38.79%. Addition of glycerol caused a decrease in the freezing point from 303 to 241 K and also significant improvement in the physical properties that are important in catalytic applications.