Abstract
The formation of highly active and stable acetylene hydrochlorination catalysts is of great industrial importance. The successful replacement of the highly toxic mercuric chloride catalyst with gold has led to a flurry of research in this area. One key aspect, which led to the commercialization of the gold catalyst is the use of thiosulphate as a stabilizing ligand. This study investigates the use of a range of sulfur containing compounds as promoters for production of highly active Au/C catalysts. Promotion is observed across a range of metal sulfates, non-metal sulfates, and sulfuric acid treatments. This observed enhancement can be optimized by careful consideration of either pre- or post-treatments, concentration of dopants used, and modification of washing steps. Pre-treatment of the carbon support with sulfuric acid (0.76 m) resulted in the most active Au/C in this series with an acetylene conversion of ≈70% at 200°C.
Highlights
The addition of a second metal has demonstrated various improvements such as stabilizing Au active species by premercuric chloride catalyst with gold has led to a flurry of research in this area
Powder X-ray diffraction (XRD) exhibited no reflections arising from gold or other metals suggesting no nanoparticles were present in any of the fresh samples, with only two broad reflections for carbon being observed at 24° and 44°/2Θ (Figure S1, Supporting Information)
Bimetallic catalysts prepared with chloroauric acid and metal sulfates were found to be active, eliminating the second metal suggested that sulfur was the crucial species for the activity enhancement
Summary
Three metal sulfates were investigated for their effect as dopants and compared to the standard aqua regia catalyst (Au/C-AR). No reflections at 2.5 and 3.0 Å were detected, suggesting no significant Au nanoparticle formation under reaction conditions which is in agreement with the data obtained from XANES and XRD This analysis demonstrated that the addition of CoSO4 to the carbon support prior to Au deposition, increased the initial acetylene conversion, by oxidizing the Au species present before reaction to Au(III). This increased the rate at which the gold reduced to the active Au(I) species, as observed in the Au/C-AR catalyst. This enhancement is seemingly sensitive to the choice of cation, the extent of doping and the order in which it is applied to the support
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