A one-pot microwave-assisted NaCl-H2O/GVL solvent system for cellulose conversion to 5-hydroxymethylfurfural and saccharides with in situ separation of the products

This work addresses a microwave-assisted, NaCl-H2O/gamma-valerolactone (GVL) solvent system for the co-production of 5-hydroxymethylfurfural (HMF) and saccharides from cellulose, examining the effects of the solvent system (H2O/GVL), NaCl concentration and reaction time. Oligosaccharides and glucose were completely recovered in the aqueous phase and their yields varied between 4-67 and 0-16 wt%, respectively, while HMF was largely recovered in the organic phase, in a yield between 0 and 13 wt%. Increasing the proportion of H2O in the system promoted cellulose depolymerisation and increased the production of oligosaccharides and glucose. This latter underwent a further decomposition to yield HMF and carboxylic acids when long times were used. An increase in NaCl not only kinetically promoted cellulose decomposition, but also modified the solubility of cellulose decomposition products in the aqueous phase, thus playing a very important role on the products distribution within both phases. With a solvent system consisting of 67/33 vol% H2O/GVL, with 30 wt% NaCl at 220 degrees C for 18 min, it is possible to selectively convert 76% of the cellulose into a sugar-rich aqueous solution and a rich HMF organic phase. The former was made up of glucose (25%) and oligosaccharides (64%), while the later mainly comprised HMF (75%). This might help the development of new biomass pre-processing technologies, allowing the co-production of precursors for the chemical and biological industries.