12-Tungstophosphoric acid/boric acid as synergetic catalysts for the conversion of glucose into 5-hydroxymethylfurfural in ionic liquid

An efficient process for the conversion of glucose into 5-hydroxymethylfurfural (HMF) with environmentally friendly and cheap catalysts was studied in the ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM]Cl). Among the catalysts employed, the combination of 12-tungstophosphoric acid (12-TPA)/boric acid (B(OH)₃) in the experiments resulted in the highest yield of HMF. The effects of various reaction parameters on HMF yields were also investigated. An HMF yield of 51.9% was achieved at 140 °C for 40 min. In addition, a small amount of water in this reaction system had little effect on the HMF yields. After the extraction of HMF, [BMIM]Cl and 12-TPA/B(OH)₃ could be reused and exhibited stable activities after five successive runs. More interestingly, like [BMIM]Cl, tetraethyl ammonium chloride (TEAC) could be favorable to HMF formation and was also used as an effective solvent for the conversion of glucose into HMF.