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Acetylene hydrochlorination using gold catalysts

Dawson, Simon Rhys 2019. Acetylene hydrochlorination using gold catalysts. PhD Thesis, Cardiff University.
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Abstract

The use of different solvents and modified carbon supports was investigated to determine their effect on the catalytic activity of gold on carbon catalysts for the hydrochlorination of acetylene. By changing the solvent from that of highly oxidising and harmful aqua regia to simple organic solvents such as acetone, the conversion of acetylene was maintained and the initial activation period of the catalyst reduced. This was attributed to the high dispersion of Au(I) species, stabilised on the carbon support. Furthermore, the drying temperature used in the preparation of the catalyst was greatly reduced, from 140 to 45 °C, owing to the high volatility of the solvent. Catalytic activity was correlated with the polarity of the solvent; decreasing the polarity resulted in higher acetylene conversions whilst higher polarities suffered from deactivation due to water present in the solvent and higher drying temperatures. Doping the Au/C catalyst with low concentrations of sulfur increased the conversion of acetylene significantly, simultaneously reducing the induction period. The most effective method for increasing the catalytic activity was found to be pre-washing the carbon in dilute H2SO4, before the addition of gold. By this method, variation of the concentration of H2SO4 had little effect on the catalytic activity, in all cases producing a high initial conversion. Carbons were prepared with a modified Hummers’ oxidation method, resulting in a greater oxygen concentration and greater catalytic activity. The optimum oxygen concentration was found to be 21 %; introduction of ether groups increased acetylene conversion whilst carbonyls were deemed responsible for reduced conversion. Notably, these oxidised carbon catalysts were active at temperatures as low as 130 °C, which would be beneficial for industrial applications. Other oxidation methods resulted in variation in the oxygen concentration, indicating that specific functional groups were responsible for changes in activity, not solely the abundance of oxygen.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Chemistry
Funders: EPSRC
Date of First Compliant Deposit: 17 February 2020
Last Modified: 17 Feb 2020 17:00
URI: http://orca.cf.ac.uk/id/eprint/129737

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