Sorbitol Hydrogenolysis over Hybrid Cu/CaO-Al2O3 Catalysts: Tunable Activity and Selectivity with Solid Base Incorporation

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• 作者：Xin Jin ; Jian Shen ; Wenjuan Yan ; Meng Zhao ; Prem S. Thapa ; Bala Subramaniam ; Raghunath V. Chaudhari
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：November 6, 2015
• 年：2015
• 卷：5
• 期：11
• 页码：6545-6558
• 全文大小：843K
• ISSN：2155-5435

文摘

We report for the first time the performance of hybridized Cu/CaO-Al₂O₃ catalysts for aqueous-phase hydrogenolysis of sorbitol to ethylene glycol (EG), 1,2-propanediol (1,2-PDO), and 1,2-butanediol (1,2-BDO) with linear alcohols as coproducts in a base-free liquid phase. These supported Cu catalysts with solid bases as promoters show significant activity for C鈥揅 cleavage and high selectivity (鈭?4%) to glycols and linear alcohols. The effects of Cu loading, catalyst pretreatment conditions, H₂ pressure, and temperature on activity and selectivity of Cu/CaO-Al₂O₃ catalysts were investigated. The strong interaction between Cu and Ca²⁺ cations in the solid support is found to facilitate C鈥揅 and C鈥揙 cleavage of sorbitol, as evidenced from TEM, SEM, and TPR studies of the catalysts. Surface characterization and activity tests further suggest that Ca_xCu_yAl_zO_p (Phase I) promotes dehydrogenation and isomerization reactions, whereas spinal CuAl₂O₄ (Phase II) species facilitates hydrogenation reactions. In addition, the overall activity and selectivity of the Cu catalysts may be easily tuned by the Cu/Ca²⁺ molar ratio and catalyst preparation conditions. Cu/CaO-Al₂O₃ catalysts also give higher overall yields of value-added glycols (63鈥?2%) for facile conversion of various other sugar polyols such as glycerol (C₃), erythritol (C₄), xylitol (C₅), and mannitol (C₆) under similar reaction conditions. A surface reaction mechanism involving the formation of 尾-ketoses on multifunctional Cu鈥揅a²⁺ sites is proposed.