The application of density functional theory to calculate adsorption properties, reaction pathways, and activation energies for surface chemical reactions is reviewed. Particular emphasis is placed on developing concepts that can be used to understand and predict variations in reactivity from one transition metal to the next or the effects of alloying, surface structure, and adsorbate-adsorbate interactions on the reactivity. Most examples discussed are concerned with the catalytic properties of transition metal surfaces, but it is shown that the calculational approach and the concepts developed to understand trends in reactivity for metals can also be used for sulfide and oxide catalysts.

Theoretical surface science and catalysis—calculations and concepts

ion from a primary OH group of glyc-erol. 223,231 A similar mechanism was proposed manyyears ago for alcohol oxidation on Pt/C, involving asecond step, the transfer of a hydride ion to the Ptsurface (Scheme 11). 8,87,237 We consider it more feasible that the rate-deter-mining step is the cleavage of the C-H bond at theR-carbon atom. A similar mechanism is now generallyaccepted for Au electrodes (Scheme 12). 238 Despite thestructural differences between Au nanoparticles andan extended Au electrode surface, there are alsosimilarities, such as the critical role of aqueousalkaline medium and the absence of deactivation dueto decomposition products (CO and C x H y frag-ments). 239,240 An important question is the nature of active siteson Au nanoparticles. Electrooxidation of ethanol onAu nanoparticles supported on glassy carbon re-quired the partial coverage of Au surface by oxides. 241 Another analogy might be the model proposed for COoxidation. 219,242,243 According to this suggestion, theactive site consists of an ensemble of metallic Auatoms and a cationic Au

Oxidation of Alcohols with Molecular Oxygen on Solid Catalysts

Mechanism and Catalyst Deactivation Lisiane V. Mattos,† Gary Jacobs,‡ Burtron H. Davis,‡ and Fab́io B. Noronha* †Departamento de Engenharia Química e de Petroĺeo, Universidade Federal Fluminense (UFF), Rua Passo da Pat́ria, 156-CEP 24210-240, Niteroí, RJ, Brazil ‡Center for Applied Energy Research, The University of Kentucky, 2540 Research Park Drive, Lexington, Kentucky 40511, United States Instituto Nacional de Tecnologia−INT, Av. Venezuela 82, CEP 20081-312, Rio de Janeiro, Brazil

Production of Hydrogen from Ethanol: Review of Reaction Mechanism and Catalyst Deactivation

The hydrodeoxygenation of furfural has been investigated over three different metal catalysts, Cu, Pd and Ni supported on SiO2, on a continuous-flow reactor under atmospheric pressure of hydrogen in the 210–290 °C temperature range. The distribution of products is a strong function of the metal catalyst used. High selectivity to furfuryl alcohol is obtained over Cu/SiO2, with the formation of only small amounts of 2-methyl furan at the highest reaction temperature studied. In contrast to Cu catalyst, the conversion of furfural over Pd/SiO2 mainly produces furan by decarbonylation. Furan can further react with hydrogen to form tetrahydrofuran (THF). Finally, on Ni/SiO2 catalysts ring opening products (butanal, butanol and butane) can be obtained in significant amounts. The different product distributions are explained in terms of the strength of interaction of the furan ring with the metal surface and the type of surface intermediates that each metal is able to stabilize.

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Hydrodeoxygenation of Furfural Over Supported Metal Catalysts: A Comparative Study of Cu, Pd and Ni

https://www.ou.edu/catalysis/pubs/2011-2.pdf

Kinetics and mechanism of hydrogenation of furfural on Cu/SiO2 catalysts

Aldehydes have been proposed as important intermediates during alcohol synthesis on supported transition metal catalysts. To develop insights into higher oxygenate syntheses, adsorption and reaction of aldehydes on transition metal surfaces and the surface structure dependence of these processes are considered here. In this work, the adsorption and reactions of acetaldehyde and propionaldehyde on Pd(110) surfaces were investigated with temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy techniques. The slate of desorption products observed in TPD experiments following acetaldehyde adsorption on the clean Pd(111) and Pd(110) surfaces was the same:  CO, H2, CH4, and CH3CHO were observed in both cases. Likewise, propionaldehyde decomposition gave rise to CO, H2, C2H4, and C2H6 on both surfaces. However, acetaldehyde isotope-labeling experiments indicated that methyl groups were released following decarbonylation reactions of acetaldehyde on Pd(110), in contrast with ...

Adsorption and Reaction of Aldehydes on Pd Surfaces

A temperature programmed reaction/desorption (TPD) study of decomposition pathways of methanol, ethanol, 1-propanol and 2-propanol was conducted on the clean Pd(110) surface under ultra-high vacuum conditions. No alcohol underwent C-O scission. Alcohols appear to react on this clean surface via the same dehydrogenation and decarbonylation steps observed on the Pd(111) surface. In contrast to previous reports noting substantial differences in methanol chemistry on the Pt(110) and (111) surfaces, the reactions of methanol and ethanol were found to be the same on the Pd(110) and (111) surfaces, giving rise to H2 plus CO from methanol, and H2, CO, and CH4 from ethanol. The C3 alcohols, 1- and 2-propanol, did produce somewhat different products on the Pd(110) and (111) surfaces, but these differences can be accounted for by differences in the chemistry of intermediate reaction products, rather than different reaction pathways of the parent alcohols.

Ratna Shekhar

Papers

Adsorption and Reaction of Aldehydes on Pd Surfaces

Structure sensitivity of alcohol reactions on (110) and (111) palladium surfaces

Decarbonylation and hydrogenation reactions of allyl alcohol and acrolein on Pd(110)

Ring-opening reactions of ethylene oxide on Pd(110) surfaces

HREELS studies of ethylene oxide interaction with Pd(110)