Improved Efficiency of CO₂ Conversion to Olefins in a Thermal–Microwave Hybrid Heating Reactor

The catalytic hydrogenation of carbon dioxide into ethylene is an innovative approach to carbon mitigation. However, the process suffers from quick deactivation and low selectivity, thus preventing it from industrial adoption. This study developed a single reactor process with two distinct reaction zones: a conventional heating zone for CO2 methanation over the Ru/CeO2 catalyst and a microwave heating zone for methane coupling over the MoOx/CeO2 catalyst. Microwave irradiation selectively heats active sites on the MoOx/CeO2 surface, reducing the required energy for initiating C–H bond activation while suppressing the formation of carbonaceous deposits, thus enhancing both the yield and selectivity of the desired products. The structural characteristics of the catalysts were further examined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and in situ Raman spectroscopy to ascertain changes in the active catalyst phase. The catalyst structure changes were correlated to the activity in CO2 conversion and ethylene selectivity between the two zones. In the conventional heating zone, 70% CO2 conversion and 99.5% selectivity for methane have been obtained. In the microwave heating zone set at 600 °C, the formation of ethylene and acetylene was observed. These results demonstrate that hybrid heating of CO2 conversion to ethylene holds excellent potential for decarbonizing multiple industrial sectors through electrification.