Effect of WOx on Bifunctional Pd鈥揥Ox/Al2O3 Catalysts for the Selective Hydrogenolysis of Glucose to 1,2-Propanediol

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• 作者：Chengwei Liu ; Chenghua Zhang ; Sikai Sun ; Kangkai Liu ; Shunli Hao ; Jian Xu ; Yulei Zhu ; Yongwang Li
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：August 7, 2015
• 年：2015
• 卷：5
• 期：8
• 页码：4612-4623
• 全文大小：683K
• ISSN：2155-5435

文摘

A series of Pd鈥揥O_x/Al₂O₃ catalysts with different contents of WO_x were prepared by stepwise incipient wetness impregnations. The influence of WO_x on the physicochemical properties of Pd鈥揥O_x/Al₂O₃ catalysts, as well as their catalytic performance for the hydrogenolysis of glucose to 1,2-propanediol (1,2-PDO), was investigated. At low surface W density (0.3鈥?.1 W nm^鈥?), distorted isolated WO_x and oligomeric WO_x are present on the Pd鈥揥O_x/Al₂O₃ catalysts. Furthermore, isolated WO₄ are the dominating species on the Pd鈥揥O_x(5%)/Al₂O₃ catalyst. When the W density increased to 3.1 W nm^鈥?, polymeric WO_x species are dominant on the Pd鈥揥O_x(30%)/Al₂O₃ catalyst. The Pd surface area decreased while the acid amount increased with increasing W density. Furthermore, increased Lewis acid sites are provided by isolated WO₄ and oligomeric WO_x species whereas increased Br酶nsted acid sites exist on polymeric WO_x species. Lewis acid sites promote glucose isomerization to fructose, which is an intermediate in glucose hydrogenolysis to 1,2-PDO. Metal sites catalyze C鈺怬 hydrogenation and C鈥揅 hydrogenolysis, which avoid the coke formation on catalysts. 1,2-PDO selectivity is dependent on the synergy of Lewis acid and metal sites; however, Br酶nsted acid sites have no contribution to the 1,2-PDO production. Typically, the Pd鈥揥O_x(5%)/Al₂O₃ catalyst possessing the optimal balance of Lewis acid and the metal site shows a 1,2-PDO selectivity of 60.8% at a glucose conversion of 92.2% and has a lifetime of over 200 h.