title: Selective catalytic oxidative-dehydrogenation of carboxylic acids-acrylate and crotonate formation at the Au/TiO2 interface.
abstract: 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═CHCOO) and crotonate (CH3CH═CHCOO) 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 (13)C and (12)C 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-Ti(4+) sites at the nanometer Au particles' 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.
authors.affiliation: Department of Chemistry, University of Virginia , Charlottesville, Virginia 22904, United States.
authors.forename: Monica
authors.initials: M
authors.lastname: McEntee
authors.forename: Wenjie
authors.initials: W
authors.lastname: Tang
authors.forename: Matthew
authors.initials: M
authors.lastname: Neurock
authors.forename: John T
authors.initials: JT
authors.lastname: Yates
mesh_terms: D000179:Acrylates / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D002384:Catalysis; D003437:Crotonates / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D006865:Hydrogenation; D053768:Metal Nanoparticles / Q000737:chemistry*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D000179:Acrylates; D002264:Carboxylic Acids; D003437:Crotonates; C009495:titanium dioxide; D006046:Gold; D014025:Titanium; C036658:acrylic acid