Understanding the production of 5-hydroxymethylfurfural (HMF) from chitosan using solid acids

Herein, we demonstrate that 5-hydroxymethylfurfural (HMF) can be chemically derived from commercial chitosan (CS (com)) using solid acids in a reaction carried out using Nafion (R) 50 resin (NR50) in a co-solvent system of methyl isobutyl ketone (MIBK) and DI water (V/V = 2) at 180 degrees C for 2 h. After reaction, the products can be well resolved by HPLC and GC-FID and identified by GC-MS. HMF yields could reach up to 32.6 +/- 4.2 mol %, which is comparable to HMF yields obtained by using homogeneous organic/inorganic acids. We surmise that interactions between the chitosan chains and the perfluorinated backbone of NR50 could interrupt the hydrogen-bonding network within the chitosan to facilitate hydrolysis and further dehydration. In addition, to understand the interactions between the chitosan monomers/oligomers with the surface of NR50 resin, gel permeation chromatography (GPC) is employed to monitor the evolution of oligomer distribution and HMF production after the reaction. The results suggest that chitosan-derived monomers/oligomers might adsorb on NR50, and D-glucosamine might favorably dehydrated for HMF production once hydrolyzed from chitosan.