Promoter doping for tuning the redox behavior of CuCl2/γ-Al2O3-based catalysts in ethylene oxychlorination: Insights from kinetic studies

Abstract

This study investigates the promoter effects of 14 metal chlorides (NaCl, KCl, RbCl, CsCl, MgCl2, CaCl2, SrCl2, CeCl3, PrCl3, NdCl3, ErCl3, FeCl3, YCl3, and SnCl3) on the CuCl2/γ-Al2O3-based catalysts used for ethylene oxychlorination. The study combines transient experiments of the two half-reactions in the redox cycle to understand the effects of different promoters on the reduction and oxidation rates of the catalysts. The results show that promoter doping can tune the redox behavior of the CuCl2/γ-Al2O3-based catalysts, affecting the reduction and oxidation steps, and the rate-determining step (RDS) changed between reduction and oxidation steps through the effects of different promoters. All the promoters have a positive effect on the reaction rate at steady-state, but the impact of promoter identity on steady-state CuCl2 concentration is variable and related to the electronegativity of the promoter metal. This work provides a better understanding of the reaction process and mechanism and highlights the potential of promoter doping for improving the efficiency and stability of CuCl2/γ-Al2O3-based catalysts in ethylene oxychlorination. The approach of both transient and steady-state kinetic modeling and simulation is a reliable and efficient method to study promoter effects on reduction–oxidation reactions.