Sodium Chloride-Assisted Depolymerization of Xylo-oligomers to Xylose

The depolymerization of hemicellulose is essential in the downstream processing of biomass within a biorefinery, with the search for energy efficient selective pathways for its conversion presenting a significant challenge. Herein, the process of NaCl promoted depolymerization of xylo-oligomers to xylose through use of seawater and NaCl, under microwave hydrolytic conditions, is investigated by systematic kinetic study assisted by deuterated agents. It was found that NaCl shortened the reaction time (10 min in NaCl–H2O vs 60 min in H2O at 180 °C) to obtain the maximum yield of xylose (about 90 wt %) without significant secondary reaction products formed. NaCl was observed to generate acidic products from residual xylose structure, rate limiting the process, but providing acids that simultaneously catalyzed the depolymerization of xylose-oligomers. It was also found that Cl– cleaved the hydrogen bonding in xylo-oligomers, releasing separated xylo-oligomer chains and enhancing the interaction of H+ with xylo-oligomers. The high concentration of Cl– in seawater was observed to significantly enhance the depolymerization process. This abundant solvent is a great prospect for the production of xylose from the depolymerization of hemicellulosic-rich biomass.