Evidence for the Bifunctional Nature of Pt鈥揜e Catalysts for Selective Glycerol Hydrogenolysis

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• 作者：Derek D. Falcone ; John H. Hack ; Alexander Yu. Klyushin ; Axel Knop-Gericke ; Robert Schl枚gl ; Robert J. Davis
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：October 2, 2015
• 年：2015
• 卷：5
• 期：10
• 页码：5679-5695
• 全文大小：633K
• ISSN：2155-5435

文摘

Rhenium substantially promotes the rate of Pt-catalyzed glycerol hydrogenolysis to propanediols and shifts the product selectivity from 1,2-propanediol to a mixture of 1,2 and 1,3-propanediols. This work presents experimental evidence for a tandem dehydration鈥揾ydrogenation mechanism that occurs over a bifunctional Pt鈥揜e catalyst. Infrared spectroscopy of adsorbed pyridine and the rate of aqueous-phase hydrolysis of propyl acetate were used to identify and quantify Br酶nsted acid sites associated with the Re component. Near-ambient-pressure XPS revealed a range of Re oxidation states on the Pt鈥揜e catalysts after reduction in H₂ at 393 and 493 K, which accounts for the presence of Br酶nsted acidity. A mechanism involving acid-catalyzed dehydration followed by Pt-catalyzed hydrogenation was consistent with the negative influence of added base, a primary kinetic isotope effect with deuterated glycerol, an inverse isotope effect with dideuterium gas, and the observed orders of reaction.