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

[Display omitted] • In situ X-ray absorption spectroscopy (XAS) and operando UV–vis-NIR measurements. • Monitoring dynamic changing Cu active sites in the transient and steady state. • Correlating the Cu oxidation state with performance under the real reaction conditions. • The influence of La promoter studied by in situ XAS. The oxidation state of Cu species in ethylene oxychlorination is strongly correlated with catalytic performance. CuCl 2 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 CuCl 2 / γ -Al 2 O 3 in transient and steady-state experiments. A higher CuCl 2 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 CuCl 2 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 CuCl 2 / γ -Al 2 O 3 based-catalysts for ethylene oxychlorination was obtained. [ABSTRACT FROM AUTHOR]