Highly Active ZnO-ZrO2 Aerogels Integrated with H-ZSM-5 for Aromatics Synthesis from Carbon Dioxide

Abstract

Bifunctional catalysis coupling CO 2 to methanol and methanol to hydrocarbons is a promising strategy for the direct hydrogenation of CO 2 into high-value chemicals. However, bifunctional catalysts suffer from low productivity due to the inertness of CO 2 and high activation energy of C–C coupling. Herein, we report a highly active bifunctional catalyst consisting of a ZnO-ZrO 2 aerogel and zeolite H-ZSM-5 for the hydrogenation of CO 2 into aromatics with 76% selectivity at a single-pass CO 2 conversion of 16%. The selectivity of CH 4 is lower than 1% at the same time. The space–time yield of aromatic hydrocarbons is as high as 0.24 g g oxide –1 h –1 under the reaction conditions of 340 °C and 40 bar over ae -ZnO-ZrO 2 /H-ZSM-5 catalyst, which outperforms the previously reported catalysts, including modified Fischer–Tropsch catalysts. We demonstrate that the ZnO-ZrO 2 aerogel catalyst, which is prepared by a combined sol–gel and subsequent supercritical drying method, not only possesses high surface area but also provides large amounts of oxygen vacancies. The formation rate of the methanol intermediate over ZnO-ZrO 2 is dominated by the total amount of oxygen vacancies. Moreover, the stable performance of the bifunctional catalyst under industrially relevant conditions suggests promising prospects for industrial applications.