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Heterogeneous gold and vanadium based catalysts for hydrochlorination and oxidation reactions.

Conte, Marco. 2006. Heterogeneous gold and vanadium based catalysts for hydrochlorination and oxidation reactions. PhD Thesis, Cardiff University.

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Abstract

The first examples of gold as the catalyst of choice were the hydrochlorination of acetylene using gold on carbon catalysts and the oxidation of carbon monoxide, both identified around 20 years ago. From that time most research interest has been focused on the use of gold as a catalyst for oxidation reactions, whereas although gold can be an excellent electrophilic agent is some of its oxidation states, few studies are available which display this. Chlorinated organic compounds are widely manufactured in industry for the production of chemicals that can be used as solvents, glues, anaesthetics, and precursor for plastics. However, the usual industrial conditions applied make use of high pressure and temperature. By focusing attention on the production of commodities like vinyl chloride monomer, and chloroethane we have seen that these kinds of products can be obtained under mild conditions when gold is used as a catalyst, and with high selectivity. Moreover, a tuneable effect can be obtained using different supports, or gold oxidation states. Although gold as a catalyst for the hydrochlorination of acetylene is known, no literature is available on the effect of adding another metal, either as a bimetallic or an alloy system, on final activity. For this reason, the effect of adding metals such as Pd, Pt, Ru, Rh, It has been investigated. Gold alone gives the most stable performance. However, when Au/Pd is used an initial promotional effect is observed. Although this effect is not a long term effect, it has been possible to detect an influence of the gold oxidation state and to identify clearly the gold oxidation state responsible for the hydrochlorination of acetylene and the mechanism of catalyst deactivation. Using carbon as a support, only carbon-carbon triple bonds are reacted and ethylene is unreactive. For this reason selectivity to vinyl chloride monomer in excess of 99% is achieved. This particular behaviour has been explained by postulating the formation of a C2H2/AU/HCI complex, and this hypothesis is supported by the use of deuterated reagents and molecular modelling investigations.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
ISBN: 9781303207907
Date of First Compliant Deposit: 30 March 2016
Last Modified: 10 Jan 2018 00:12
URI: http://orca.cardiff.ac.uk/id/eprint/56150

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