Direct conversion of cellulose into C6 alditols over Ru/C combined with H+-released boron phosphate in an aqueous phase

Abstract

Non-edible cellulose has attracted considerable attention to be converted into valuable platform chemicals. Direct transformation of cellulose to C₆ alditols (mannitol and sorbitol) provides a sustainable route. A productive approach is presented in this work using a Ru/C catalyst combined with H⁺-released boron phosphate in an aqueous phase. A yield of C₆ alditols as high as 74.9% with a 91% conversion of cellulose is achieved. By adding silica–alumina materials, the yield of C₆ alditols can be improved to 93.5% with complete conversion. The acid sites gradually released from boron phosphate under hydrothermal conditions could promote the hydrolysis of cellulose without significant degradation of glucose. Furthermore, the interaction of boric acid with C₆ alditols may form borate–polyol complexes, which can enhance the stability of the C₆ alditols to avoid further hydrogenolysis and dehydration of the C₆ alditols formed. Due to the adsorption ability of the substrate, the addition of silica–alumina materials with a high content of silica leads to improved performance.