Efficient conversion of chitin to HMF under the co-catalytic system of formic acid and silicotungstic acid

The conversion process of chitin, one of the abundant biomass resources on the earth, not only follows the principles of green chemistry, but also has significant value in industrial applications. However, it is a great challenge to directly convert insoluble and rigid structured chitin to 5-hydroxymethylfurfural (HMF). To address this issue, we developed a green conversion process combining pretreatment and catalytic system. Chitin was first pretreated by hexafluoro isopropanol (HFIP), which somewhat disrupted the hydrogen bonding network within the chitin structure. Subsequently, formic acid (FA) and silicotungstic acid (STA) synergistically catalyzed the conversion to HMF in a biphasic system of 2-methyltetrahydrofuran (2-Me-THF)/H₂O, and high yields (40.2%) HMF was obtained under the optimism conditions. The product distribution was analyzed by HPLC-MS and the co-catalysis of FA with STA was evidenced. A dual-function catalytic system with both Lewis and Brønsted acids was created, the catalytic system that significantly improved the efficiency of complex tandem catalytic reactions with chitin. Based on the experimental results, a possible pathway for chitin conversion was deduced, providing a new catalytic idea for the efficient conversion of chitin to HMF.