Selective Catalytic Oxidative-Dehydrogenation of Carboxylic Acids鈥擜crylate and Crotonate Formation at the Au/TiO2 Interface

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• 作者：Monica McEntee ; Wenjie Tang ; Matthew Neurock ; John T. Yates ; Jr
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：April 2, 2014
• 年：2014
• 卷：136
• 期：13
• 页码：5116-5120
• 全文大小：359K
• 年卷期：v.136,no.13(April 2, 2014)
• ISSN：1520-5126

文摘

The oxidative-dehydrogenation of carboxylic acids to selectively produce unsaturated acids at the second and third carbons regardless of alkyl chain length was found to occur on a Au/TiO₂ catalyst. Using transmission infrared spectroscopy (IR) and density functional theory (DFT), unsaturated acrylate (H₂C鈺怌HCOO) and crotonate (CH₃CH鈺怌HCOO) were observed to form from propionic acid (H₃CCH₂COOH) and butyric acid (H₃CCH₂CH₂COOH), respectively, on a catalyst with 3 nm diameter Au particles on TiO₂ at 400 K. Desorption experiments also show gas phase acrylic acid is produced. Isotopically labeled ¹³C and ¹²C propionic acid experiments along with DFT calculated frequency shifts confirm the formation of acrylate and crotonate. Experiments on pure TiO₂ confirmed that the unsaturated acids were not produced on the TiO₂ support alone, providing evidence that the sites for catalytic activity are at the dual Au鈥揟i⁴⁺ sites at the nanometer Au particles鈥?perimeter. The DFT calculated energy barriers between 0.3 and 0.5 eV for the reaction pathway are consistent with the reaction occurring at 400 K on Au/TiO₂.