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高选择性一步转化纤维素制山梨醇,是实现纤维素制备高附加值化学品的一个重要途径。催化剂的酸水解性能及加氢性能直接影响纤维素一步转化的反应结果。筛选了一系列纳米酸性金属氧化物与Ru/CMK-3组合催化剂,结果表明纳米γ-Al_2O_3-Ru/CMK-3组合催化剂可高选择性催化纤维素转化为山梨醇,在适宜的反应条件下,纤维素转化率为49.8%,山梨醇选择性可高达91.3%。并讨论了各组合催化剂的酸性位、加氢活性位的组合特点及反应产物的分布特征,结果表明催化剂的酸性位和加氢活性位的合理匹配是提高山梨醇选择性的重要因素。当酸性位占主导时,纤维素水解生成的葡萄糖不能快速加氢转化,会降解生成5-羟甲基糠醛等副产物,从而降低山梨醇选择性。
The high selectivity of one-step conversion of cellulose to sorbitol is an important way to achieve cellulose-based high-value-added chemicals. The acid hydrolysis performance and hydrogenation performance of the catalyst directly affect the reaction result of one-step conversion of cellulose. A series of nanosized acidic metal oxides and Ru / CMK-3 composite catalysts were screened. The results show that the nanosized γ-Al_2O_3-Ru / CMK-3 composite catalysts can catalyze the conversion of cellulose to sorbitol under suitable reaction conditions , Cellulose conversion rate of 49.8%, sorbitol selectivity up to 91.3%. The characteristics of the combination of acidic site and hydrogenation site and the distribution of the reaction products were discussed. The results show that the reasonable match between the acidic site and the hydrogenation site of the catalyst is an important factor to improve the selectivity of sorbitol. When the acidic sites dominate, the glucose produced by cellulose hydrolysis can not be rapidly hydroconverted and will degrade by-products such as 5-hydroxymethylfurfural to reduce the sorbitol selectivity.