University of Surrey

Test tubes in the lab Research in the ATI Dance Research

Adsorption Geometry Determines Catalytic Selectivity in Highly Chemoselective Hydrogenation of Crotonaldehyde on Ag(111)

Brandt, K, Chiu, M, Watson, DJ, Tikhov, M and Lambert, R (2012) Adsorption Geometry Determines Catalytic Selectivity in Highly Chemoselective Hydrogenation of Crotonaldehyde on Ag(111) The Journal of Physical Chemistry Part C: Nanomaterials and Interfaces. ISSN 1932-7447

[img]
Preview
PDF (licence)
SRI_deposit_agreement.pdf

Download (32Kb)
[img]
Preview
PDF
WATSON_Adsorption.pdf

Download (957Kb)
[img]
Preview
PDF
WATSON_Adsorption_Supplementary_Info.pdf

Download (148Kb)

Abstract

The chemoselective hydrogenation of crotonaldehyde to crotyl alcohol was studied by temperature programmed desorption/reaction, high resolution XPS and NEXAFS. The organic molecule adsorbed without decomposition, all three possible hydrogenation products were formed and desorbed, and the clean overall reaction led to no carbon deposition. Selectivities up to 95% were found under TPR conditions. The observed behavior corresponded well with selectivity trends previously reported for Ag/SiO2 catalysts and the present findings permit a rationalization of the catalytic performance in terms of pronounced coverage-dependent changes in adsorption geometries of the reactant and the products. Thus at low coverages the C=O bond in crotonaldehyde lay almost parallel to the metal surface whereas the C=C was appreciably tilted, favoring hydrogenation of the former and disfavoring hydrogenation of the latter. With increasing coverage of reactants, the C=C bond was forced almost parallel to the surface, rendering it vulnerable to hydrogenation, thus markedly decreasing selectivity towards formation of crotyl alcohol. Butanol formation was the result of an overall two-step process: crotonaldehyde → crotyl alcohol → butanol, further hydrogenation of the desired product crotyl alcohol being promoted at high hydrogen coverage due to the C=C bond in the unsaturated alcohol being driven from a tilted to a flat-lying geometry. Finally, an explanation is offered for the strikingly different behavior of Ag(111) and Cu(111) in the chemoselective hydrogenation of crotonaldehyde in terms of the different degrees of charge transfer from metal to C=O π bond, as suggested by C 1s XPS binding energies.

Item Type: Article
Additional Information: Copyright © 2012 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry Part C: Nanomaterials and Interfaces, copyright © American Chemical Society after peer review and technical editing by the publisher.To access the final edited and published work see http://dx.doi.org/10.1021/jp208831h.
Divisions: Faculty of Engineering and Physical Sciences > Chemistry
Depositing User: Symplectic Elements
Date Deposited: 29 Mar 2012 13:36
Last Modified: 23 Sep 2013 19:11
URI: http://epubs.surrey.ac.uk/id/eprint/203290

Actions (login required)

View Item View Item

Downloads

Downloads per month over past year


Information about this web site

© The University of Surrey, Guildford, Surrey, GU2 7XH, United Kingdom.
+44 (0)1483 300800