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

The oxidation state of Cu species in ethylene oxychlorination is strongly correlated with catalytic perfor-mance. 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/c-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 evi-denced 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/c-Al2O3 based-catalysts for ethylene oxychlorination was obtained.(c) 2022 Published by Elsevier Inc.