Deactivation of a Single-Site Gold-on-Carbon Acetylene Hydrochlorination Catalyst: An X-ray Absorption and Inelastic Neutron Scattering Study

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 L 3 X-ray absorption spectroscopy (XAS). Alternating between a standard reaction mixture of HCl/C 2 H 2 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 C 2 H 2 , in accordance with both the XAS measurements of Au oxidation state and the reaction kinetics being first order with respect to each reactant. Excess C 2 H 2 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 continued...

Carbon with Surface‐Enriched Nitrogen and Sulfur Supported Au Catalysts for Acetylene Hydrochlorination

“…In the fresh Au/AC catalyst, the relative content of Au 3+ and Au 0 were 55 % and 45 %. The Au 0 existed in fresh Au/AC might be originated from the reduction of Au 3+ to Au 0 by the carboxyl functional groups on the carbon surface ,,. Besides, carbon with low reduction potential is also capable of reducing Au 3+ to Au 0 .…”

“…Therefore, nonmercuric catalytic systems are urgently required in consideration of safety and green chemistry. To resolve this problem, a series of metal chlorides catalytic systems employing AuCl 3 , PdCl 2 ,, RuCl 3 and CuCl 2 as catalysts have been investigated by Hutchings et al . and many other research groups for acetylene hydrochlorination.…”

Adsorption Behavior and Electron Structure Engineering of Pd-Based Catalysts for Acetylene Hydrochlorination

“…Poly vinyl chloride (PVC), as the most commonly used thermoplastic, is used in different kinds of fields in modern society [1][2][3]. There are two basic ways in which vinyl chloride monomer (VCM) can be widely produced: the hydrochlorination of acetylene and the oxychlorination of ethylene [2][3][4][5]. For acetylene hydrochlorination, Hg-based catalysts have been used as the main industrial catalysts for the production of VCM.…”

“…For acetylene hydrochlorination, Hg-based catalysts have been used as the main industrial catalysts for the production of VCM. However, mercuric component is volatile under the reaction conditions and thus do harmful to ecological environment and human beings [1][2][3][4][5][6]. Thus, replace of toxic Hg-based catalysts with non-mercury-containing alternatives would be significantly beneficial in this process [6][7][8][9][10][11][12][13][14][15][16][17].…”

An efficient Au catalyst supported on hollow carbon spheres for acetylene hydrochlorination

“…3 Later, Hutchings's group found that single-site cationic Au entities exhibited activity that correlated with the ratio of Au(I)/Au(III) in the catalyst. 4 Although the deactivation of the catalyst might be associated with the formation of metallic Au particles, 5 metallic Au played a role in the catalysis of acetylene hydrochlorination, when the size of Au nanoparticles was controlled to a very small scale. Perez-Ramirez et al found that Au single atoms hosted on N-doped carbon-derived by the controlled pyrolysis of polyaniline exhibited remarkable stability for acetylene hydrochlorination.…”