Aqua regia activated Au/C catalysts for the hydrochlorination of acetylene

• Published in: Journal of catalysis 2013-01, Vol.297, p.128-136
• Main Authors: Conte, Marco, Davies, Catherine J., Morgan, David J., Davies, Thomas E., Elias, David J., Carley, Albert F., Johnston, Peter, Hutchings, Graham J.
• Format: Article
• Language: English
• Subjects: acetylene; Acetylene hydrochlorination; Aqua regia; Carbon; Catalysis; catalysts; Chemical reactions; Chemistry; Exact sciences and technology; gases; General and physical chemistry; Gold; Gold alloys; hydrochloric acid; nanogold; Nanoparticles; nitric acid; Oxidation; solvents; temperature; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; vinyl chloride
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2012.10.002

Au/C catalysts prepared using aqua regia as a solvent display superior activity in the hydrochlorination reaction of acetylene to vinyl chloride monomer. A synergistic effect between HCl and HNO3 is observed, which is linked to the nucleation of Au nanoparticles. [Display omitted] ► Impregnated Au/C catalyst with aqua regia as a solvent displayed superior activity in the hydrochlorination reaction of acetylene to vinyl chloride monomer. ► A synergistic effect between HCl and HNO3 is present, driving the Au nanoparticles nucleation process over the carbon support. ► The impregnating acid mixture can affect the carbon support enriching the presence of oxygen functional groups. ► The reaction occurs over Au3+ centres at the Au/C interface. Au/C catalysts are effective materials for the gas phase hydrochlorination of acetylene to vinyl chloride monomer, and to date, the most effective catalyst preparation protocol makes use of impregnation using aqua regia. In the present study, the effect of this solvent is evaluated and discussed in detail by modifying the ratio of HCl and HNO3 and the temperature of the impregnation step. These factors are observed to affect the Au3+/Au0 ratio of the final catalyst, in addition to the modification of the functional groups of the carbon used as support. The results can be rationalised by the oxidation effect of HNO3 on both the gold nanoparticles and the functional groups on the carbon surface, as well as a nucleation effect of HCl towards gold over the carbon support.