Production of 5-hydroxymethylfurfural in a eutectic mixture of citric acid and choline chloride and its extractive recovery

Synthesis of 5-hydroxymethylfurfural (HMF) from d-fructose was analyzed from the kinetic and equilibrium points of view in a eutectic mixture of citric acid and choline chloride (CA/CC) or in [Bmim]Cl to achieve an efficient production of HMF in a biphasic reaction system. The partition coefficient of HMF between an organic solvent and the ionic liquid phases was measured using various organic solvents. Among these solvents, ethyl acetate was found to exhibit the best performance for the extractive recovery of HMF. The stability of HMF was also evaluated in CA/CC at 70–120 °C, and HMF was found to be stable below 80 °C. Kinetic analysis of the formation of HMF was performed under the assumption that fructose was converted into HMF through parallel and consecutive reactions. The kinetically calculated results matched well with the experimental ones. The reaction behaviors were different at low and high (over 20% (kg/kg of IL)) initial fructose concentrations. At high initial fructose concentrations, the equilibrium yield of HMF decreased with increasing initial fructose concentration. The addition of ethyl acetate to the CA/CC phase (biphasic reaction) was effective in improving the HMF yield, especially when the fructose concentration was high