Microwave-Derived Hierarchic Liquefaction of Pentose and Intensified Separation of Furfural

A microwave-coupled biphasic solvent system was developed for steerable liquefaction of pentoses and hierarchic separation of furfural by leveraging the dielectric properties of γ-valerolactone (GVL)/NaCl aqueous solution under microwave irradiation, during which more than 85.38 mol% of furfural yield was obtained from xylan at 140 °C for 20 min, compared to that of 78.1 mol% at 150 °C for 120 min under conventional heating conditions. Strikingly, the separation efficiency was improved under microwave conditions with the partition coefficients (R) of furfural ranging from 31.1 to 35.68, compared with 22.71 to 29.33 under conventional heating conditions. Moreover, the coupled effect on the substrate from the microwave was also explored. Notably, high heating power during the initial hydrolysis phase enhances the depolymerization of xylan glycosidic bonds, resulting in the rapid release of 87.89 mol% xylose from xylan. Meanwhile, the application of low heating power during the dehydration process effectively facilitates the production of furfural, which is promptly extracted into the organic phase, thereby minimizing product loss. Besides, the feasibility of the process was assessed using real biomass as the substrate, demonstrating low energy consumption attributed to the efficient microwave absorption by GVL and the NaCl aqueous solution. This approach offers a viable strategy for the efficient and scalable production of furfural.