Insight into 5-hydroxymethylfurfural synthesis and separation from the aqueous solvent with ion exchange resin catalysts, mechanisms, and theoretical calculations

The efficacy of green and economical water-choline chloride (ChCl) co-solvent for the production of 5-hydroxymethylfurfural (HMF) from glucose and fructose, using different ion exchange resins as catalysts, was demonstrated under mild conditions in a water/Methyl isobutyl ketone (MIBK) biphasic system. The maximum HMF yield from fructose reached 96.8%. Bifunctional acidic resin catalysts effectively facilitated glucose conversion, with the recyclable and environmentally friendly Amb-15-Al catalyst achieving a 64.7% HMF yield. The mechanistic study and quantitative computational analysis indicated that glucose conversion was more favorable in water-containing systems than in pure deep eutectic solvents (DES). Furthermore, it also demonstrated the catalytic ability and energy barrier differences of Lewis acidic sites Al, Cr, and Sn ions for glucose isomerization in water-ChCl systems. This study presented a combination of a non-toxic and cost-effective reaction strategy and provided a theoretical calculation and experimental validation of the bio-refinery reaction mechanism.