Efficient CO2 catalytic hydrogenation over CuOx–ZnO/silicalite-1 with stable Cu+ species

Abstract

Cu-based/SiO₂ nanocatalysts with Cu⁰ or Cu⁺ species as active sites have been widely investigated for CO₂ hydrogenation. Here, 10CuO/silicalite-1(S-1) and 10CuO–2ZnO/S-1 catalysts were prepared inexpensively via a wet impregnation method. A 7.5% conversion of CO₂ was reached and kept for 100 h over 10CuO–2ZnO/S-1 at 250 °C and 3 MPa. XPS and in situ CO-DRIFT showed that only Cu⁺ species existed on the surfaces of both catalysts due to silanol nests from S-1. Moreover, there was synergism between Cu⁺ species and ZnO on 10CuO–2ZnO/S-1, confirmed by H₂-TPR and in situ H–D exchange DRIFT, in which ZnO was responsible for H₂ dissociation and the Cu⁺ species of ZnO–Cu₂O interface adsorbed CO₂. Subsequently, the adsorbed CO₂ was hydrogenated to CO via the carboxylate pathway by H species generated from ZnO. This study provides new insights into the Cu-based/SiO₂, in which the ZnO–Cu₂O inter face and silanol nests from S-1 play key roles in CO₂ hydrogenation, efficiently and steadily.