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.

Automated summary

The oxidation state of Cu species in ethylene oxychlorination is closely related to its catalytic performance. CuCl2 and CuCl are the primary active sites in the reduction and oxidation steps, respectively. The distribution of active sites is determined by the kinetic equilibrium of reduction, oxidation, and hydrochlorination rates. In this study, in situ X-ray absorption spectroscopy (XAS) and operando UV-vis-NIR spectroscopy were used to study the dynamic changes of Cu active sites in La-doped CuCl2/c-Al2O3 catalysts. A higher CuCl2 concentration significantly improves the activity, EDC selectivity, and stability. The presence of La enhances the reducibility of CuCl2 and modifies the catalytic performance rather than directly participating in the redox cycle. This study provides a deeper understanding of the role of active species and promoters in CuCl2/c-Al2O3 catalysts for ethylene oxychlorination.