Carbohydrates are the renewable feedstocks to produce 5-hydroxymethylfurfural (HMF) through hexose dehydration. Fructose is widely applied as the raw material in the formation of HMF due to its high rate and selectivity of conversion to HMF. In the HMF production process, the liquid-liquid extraction is essentially used to extract HMF from the reaction medium. The use of an ionic liquid (IL) and a deep eutectic solvent (DES) has been recognized to increase the yield of HMF by suppressing the formation of side products. The aim of this study is to systematically study the effect of fructose on the extraction performance of HMF in the water-1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) or choline chloride urea (ChCl-urea)-sodium chloride (NaCl) solution at 313.15 K and an atmospheric pressure of 0.1 MPa. Methyl isobutyl ketone was used as a selective extraction solvent. The separation factor and the distribution coefficient of HMF were obtained from liquid-liquid equilibrium (LLE) data to interpret the extraction performance. According to the results in this study, fructose had a minimal effect on the extraction performance of HMF. For the LLE system using [EMIM][BF4], the HMF distribution coefficient values showed comparable values to the LLE system without fructose. However, the separation factors decreased by around 1.1 times. Furthermore, fructose decreased the separation factors by around 1.3 times and distribution coefficients of HMF by around 1.1 times for the LLE system using ChCl-urea. A comparison of the IL and DES used indicated that HMF extraction from an aqueous DES (ChCl-urea) demonstrated a better extraction performance with the separation factor, and the HMF distribution coefficient values were 1.4 and 1.2 times higher than those for HMF extraction from an aqueous IL ([EMIM][BF4]), respectively. The experimental LLE data were correlated well using the non-random two-liquid model. The reliability of the experimental LLE data was also satisfactorily ascertained by the Hand and Othmer-Tobias correlations.

Deep eutectic solvent (DES) has demonstrated its ability to improve the yield and selectivity in the 5-hydroxymethylfurfural (HMF) production process. Liquid-liquid extraction is a beneficial process in HMF production to recover HMF from the reaction medium. In the present study, the effect of DES (choline chloride urea) on the liquid-liquid equilibria (LLE) of HMF-water-organic solvent (methyl isobutyl ketone (MIBK) or 2-pentanol) systems in the absence and presence of sodium chloride (NaCl) was investigated at 313.15 K and atmospheric pressure (0.1 MPa). The tie-lines of the multicomponent systems were measured using several analytical methods. According to the experimental results, the extraction performance decreased with an increase in DES concentration. However, the addition of 10 wt % NaCl into the HMF aqueous DES solution can induce stronger liquid-liquid phase splitting, enhancing the separation factors and distribution coefficients of HMF by around 2.7 and 1.6 times, respectively. Additionally, MIBK showed better extraction performance in the presence of DES and NaCl with the separation factors 2.6 times higher than those of 2-pentanol and the HMF distribution coefficients above 1.8. The LLE of the multicomponent systems were correlated well with the nonrandom two-liquid (NRTL) model.

HMF (5-hydroxymethylfurfural) is a well-known promising product from hexose dehydration used for production of biofuels and chemicals. Liquid-liquid extraction is an essential process in HMF production to recover HMF from reaction medium. One of the important parameters needed in the extraction process design is liquid-liquid equilibrium (LLE) data. Organic solvent (methyl isobutyl ketone or 2-pentanol) was applied as extraction solvent to induce phase separation and extract HMF from the aqueous solution in the presence of the ionic liquid [EMIM][BF₄] (1-ethyl-3-methylimidazolium tetrafluoroborate) and NaCl (sodium chloride). The aim of this study is to investigate the effect of [EMIM][BF₄] on the phase equilibria of methyl isobutyl ketone (MIBK) or 2-pentanol, HMF, water systems in the absence and presence of NaCl at 313.15 K and atmospheric pressure (0.1 MPa). The separation factor and the distribution coefficient of HMF were obtained for interpreting liquid-liquid extraction performance. The results indicated that the presence of [EMIM][BF₄] caused negative effect on the LLE of organic solvent-HMF-water systems. The slope of tie-lines became more negative with increasing [EMIM][BF₄] concentration, indicating lower HMF distribution coefficients and separation factors. However, the presence of NaCl in the HMF aqueous ionic liquid solution can enhance both the separation factor and the distribution coefficient making the HMF extraction more favourable with the HMF distribution coefficient values higher than 1 over the whole range of initial HMF concentrations. According to the results in the present study, MIBK was found superior as an extraction solvent for HMF in the presence of [EMIM][BF₄] and NaCl exhibited from the better extraction performance with the separation factors 2.0 times higher than those of 2-pentanol. Furthermore, the NRTL activity coefficient model satisfactorily correlated all the experimental phase equilibrium data provided in this study. The RMSD (root mean square deviations) of the NRTL model were 0.97% and 0.63% for the investigated LLE systems with MIBK and 2-pentanol as solvent in the absence of NaCl, respectively. Whereas, the RMSD of the LLE systems containing NaCl were 0.28% for MIBK-HMF-water-[EMIM][BF₄]-NaCl and 0.90% for 2-pentanol-HMF-water-[EMIM][BF₄]-NaCl.

HMF (5-hydroxymethylfurfural) is one of the bio renewable materials that can be used to produce a wide range of chemical products. In the HMF production process, yield and selectivity may be increased by liquid-liquid extraction of HMF using an organic solvent to prevent its degradation. Phase equilibrium data are required for rational design and optimal separation of HMF from the aqueous solution. In this study, liquid-liquid equilibrium (LLE) data of HMF, water, and methyl isobutyl ketone (MIBK) or 2-pentanol at 313.15 K (40 °C) and atmospheric pressure were measured and correlated using the NRTL and UNIQUAC models. The root mean square deviations (RMSD) of the NRTL and UNIQUAC models were 0.42% and 0.48% for the MIBK-HMF-water and 0.81% and 0.77% for the 2-pentanol-HMF-water system, respectively. The results indicated that higher distribution coefficients are achieved in the 2-pentanol-HMF-water system compared to the MIBK-HMF-water system. On the other hand, the separation ability of MIBK is better than that of 2-pentanol. In liquid-liquid extraction, not only a high distribution coefficient of HMF is important, but also a high separation factor is desirable to reduce the amount of co-extracted water. Therefore, in the present study the distribution coefficient of HMF from MIBK-HMF-water and the separation factor of the 2-pentanol-HMF-water system was improved by introducing a certain amount of salt into the aqueous solution. The salts examined in this study were based on the variety of cation (Na⁺, K⁺) and anion (Cl⁻, SO₄ ²⁻). The NRTL model was applied to correlate the LLE of organic solvent-HMF-water-salt systems, the results of which provided good agreement with the experimental data. The presence of salt can enhance the partitioning of HMF into the organic phase as well as the separation factor up to 2 times indicating the salting-out ability of the studied salts. The order of salting-out strength was NaCl > Na₂SO₄ > KCl > K₂SO₄ in which Cl⁻ and Na⁺ demonstrated stronger salting-out ability than SO₄ ²⁻ and K⁺.