Direct Synthesis of Hexitols from Microcrystalline Cellulose and Birch over Zirconium (IV) Phosphate Supported Nickel Catalysts and the Mechanism Study

Direct and selective conversion of renewable lignocellulose to the platform molecule sorbitol is attractive for valorization of biomass. Herein, a series of phosphate solid acids were prepared and loaded with Ni for cellulose conversion to produce high value-added sorbitol. Zirconium phosphate (ZrP) exhibited the best catalytic activity among the screened catalysts. To explore the structure–function relationship for sorbitol production, systematic characterization studies including XRD, TEM, AAS, HADDF-STEM-EDS, XPS, FT-IR, NH3-TPD, and H2-TPD and comparative experiments were carried out. It was found that the precise regulation of the acid site and the hydrogenation site of the catalyst was crucial to inhibit humin formation and improve the yield of sorbitol. Using Ni/ZrP2 as the catalyst, 60.8% yield of sorbitol was achieved when microcrystalline cellulose (MCC) was used as the substrate. Moreover, 40.2% yield of sorbitol and 67.9% yield of xylitol were obtained directly from birch wood.