Superior Salting‐Out of MgSO ₄ to Improve the Synthesis of 5‐Hydroxymethylfurfural

Abstract The effect of salts on the 5‐hydroxymethylfurfural (HMF) synthesis over the catalyst of AlCl 3 ‐HCl was investigated. An unprecedented R (distribution coefficient) value of 30.48 was achieved in the H 2 O/THF system when MgSO 4 was used as a salting‐out agent. Results indicated that the excellent salting‐out effect of MgSO 4 on HMF was attributed to the synergistic effect of Mg 2+ and SO 4 2− . MgSO 4 showed more efficiency on the HMF synthesis than other salts in the ChCl‐H 2 O/THF biphasic system. A 78.1% yield of HMF was achieved from glucose under optimal conditions, and higher than 95.0% of the produced HMF was partitioned into the organic phase due to the excellent salting‐out effect of MgSO 4 . During the recyclability of the aqueous phase, a remarkably high yield of HMF (78.0%) and conversion of glucose (93.8%) were achieved even after 10 cycles. The MgSO 4 also showed efficiency to improve the synthesis of HMF from other sugars. Finally, the salting‐out effect of MgSO 4 on sugar dehydration was investigated in other biphasic systems, and the yield of HMF showed an obvious increase compared with the literature reports.