Yong Liu,Lungang Chen,Tiejun Wang,Ying Xu,Qi Zhang,Longlong Ma,Yuhe Liao,Ning Shi
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.
The selective transformation of cellulose to C6 alditols provides a feasible route towards the sustainable synthesis of chemicals and fuels. Herein, the catalytic performance of amorphous zirconium phosphate (ZPA) combined with 5 wt% Ru/C was evaluated in the direct conversion of cellulose to C6 alditols (sorbitol and mannitol) under hydrothermal conditions. The yield of C6 alditols reached 63.5% and 85.5% with microcrystalline cellulose and ball-milled cellulose as the feedstock, respectively. This hybrid catalyst was developed to convert concentrated cellulose to obtain C6 alditols with a high concentration of 68.8 mg mL−1 in the final products. The high yield of C6 alditols from cellulose was ascribed to the fact that ZPA favoured the adsorption of cellulose and promoted its depolymerization to cellobiose and glucose, which was hydrogenated immediately to C6 alditols over Ru/C. The weak adsorption of C6 alditols over ZPA inhibited the dehydration of C6 alditols to sorbitan. Furthermore, ZPA exhibited excellent hydrothermal stability and could be reused for several runs.
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