Deactivation of a single-site gold-on-carbon acetylene hydrochlorination catalyst: an x-ray absorption and inelastic neutron scattering study

Malta, G. et al. (2018) Deactivation of a single-site gold-on-carbon acetylene hydrochlorination catalyst: an x-ray absorption and inelastic neutron scattering study. ACS Catalysis, 8(9), pp. 8493-8505. (doi: 10.1021/acscatal.8b02232)

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Abstract

Single-site Au species supported on carbon have been shown to be the active sites for acetylene hydrochlorination. The evolution of these single-site species has been monitored by Au L3 X-ray absorption spectroscopy (XAS). Alternating between a standard reaction mixture of HCl/C2H2 and the single reactants has provided insights into the reaction mechanism and catalyst deactivation processes. We demonstrate that oxidative addition of HCl across an Au(I) chloride species requires concerted addition with C2H2, in accordance with both the XAS measurements of Au oxidation state and the reaction kinetics being first order with respect to each reactant. Excess C2H2 changes the Au speciation and results in the formation of oligomeric acetylene species which were detected by inelastic neutron scattering. Catalyst deactivation at extended reaction times can be correlated with the formation of metallic Au particles. These Au(0) species generated during the sequential gas experiments, or after prolonged reaction times, results in the analysis of the normalized near-edge white line intensity becoming an unsuitable guide for identifying the active Au species, affecting the strong correlation between normalized white line height and VCM productivity usually observed in the active catalyst. Thus, a combination of scanning transmission electron microscopy and detailed modeling of whole XAS spectrum was required to distinguish active Au(I) and Au(III) species from the spectator Au(0) component.

Item Type:Articles
Additional Information:The UK Catalysis Hub is thanked for resources and support provided through our membership of the UK Catalysis Hub Consortium and funded by the Engineering and Physical Sciences Research Council (EPSRC) (grants EP/K014706/1, EP/K014668/1, EP/ K014854/1EP/K014714/1, and EP/M013219/1).
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Gibson, Dr Emma and Parker, Dr Stewart
Authors: Malta, G., Kondrat, S. A., Freakley, S. J., Davies, C. J., Dawson, S., Liu, X., Lu, L., Dymkowski, K., Fernandez-Alonso, F., Mukhopadhyay, S., Gibson, E. K., Wells, P. P., Parker, S. F., Kiely, C. J., and Hutchings, G. J.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:ACS Catalysis
Publisher:American Chemical Society
ISSN:2155-5435
ISSN (Online):2155-5435
Published Online:27 July 2018
Copyright Holders:Copyright © 2018 American Chemical Society
First Published:First published in ACS Catalysis 8(9): 8493-8505
Publisher Policy:Reproduced in accordance with the publisher copyright policy
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
169321Catalytic HDO : Queen's University of Belfast ref R1188CCESamuel JacksonEngineering and Physical Sciences Research Council (EPSRC)EP/K014706/1Chemistry