In situ monitoring of dynamic behavior of La-doped CuCl2/γ-Al2O3 catalyst in ethylene oxychlorination

Abstract

The oxidation state of Cu species in ethylene oxychlorination is strongly correlated with catalytic performance. CuCl2 and CuCl have been identified as the primary active sites in the reduction and oxidation step, respectively, according to a redox-type mechanism. The distribution of the active sites is governed by the kinetic equilibrium of the reduction, oxidation, and hydrochlorination rates at steady-state. Herein, in situ X-ray absorption spectroscopy (XAS) and operando ultraviolet–visible and near-infrared spectroscopy (UV–vis-NIR) were utilized to quantify the dynamic changes of the Cu active sites over the La-doped CuCl2/γ-Al2O3 in transient and steady-state experiments. A higher CuCl2 concentration plays a key role in dominating the higher activity, EDC selectivity, and stability. The in situ XAS result evidenced La was considered as a structural additive to increase the reducibility of the active CuCl2 and modify the catalytic performance instead of directly involving the reduction-oxidation cycle. A deeper understanding of the complex role of the active species and promoter in the CuCl2/γ-Al2O3 based-catalysts for ethylene oxychlorination was obtained.