Construction of highly dispersed Au active sites by ice photochemical polishing for efficient acetylene hydrochlorination

Abstract

Considering the economic and environmental advantages of water as a solvent and the drawbacks of Au catalysts prepared in an aqueous solution for acetylene hydrochlorination, such as easy aggregation of active components, insufficient active sites, and serious carbon deposition, supported gold catalysts were prepared by using an ice photochemical method (liquid nitrogen freezing and UV light irradiation). The appropriate ice-photochemical treatment results in ice lattice formation, which inhibits gold nuclei formation during the catalyst preparation and catalytic reaction. In addition, it limits the crystal phase change and aggregation of active species. The freezing and the energy absorbed by the gold component under irradiation at the exact wavelengths may produce a plasma effect on the surface of the Au component and promote the excitation of outer electrons of the Au nucleus to Cl, suppressing the transition of the dispersed atomic active species with a high valence state to the inert Au⁰ clusters. Therefore, the superior activity of the prepared catalysts Au/AC-F₁I₁ is probably caused by the synergistic adsorption and activation of reactants by the highly dispersed AuCl_x-like multi-sites, facilitating the rapid electrophilic addition reaction and impeding the carbon deposition, thus promoting the continuous exposure of active sites. The significantly improved activity and stability, and the environment-friendly preparation strategy provide new inspiration for the design and application of Au-based catalysts for acetylene hydrochlorination.