CO2-mediated oxidative dehydrogenation of ethane over Co/MgAl2O4 catalysts

A series of Co/MgAl 2 O 4 (CM1A2) catalysts with controlled cobalt loadings (0.5–3 wt%) were successfully synthesized using a co-precipitation method and tested for CO 2 -mediated oxidative dehydrogenation of ethane (CO 2 -ODHE) reaction. 1.5CM1A2 catalyst (1.5 wt%) displays the best catalytic performance, superior to other transition metal-based catalysts with ethane conversion, CO 2 conversion and ethylene yield at 700 °C about 42%, 8% and 38%, respectively. The catalysts were systematically characterized by X-ray diffraction (XRD), Raman spectroscopy, Ultraviolet-visible spectrophotometry (UV–vis), X-ray photoelectron spectroscopy (XPS), and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results reveal that the non-reducible MgAl 2 O 4 support possesses remarkable thermal stability and the obtained catalysts exhibit resistance to dry reforming of ethane (DRE) reaction, facilitating prolonged high catalytic activity and selectivity at 650–700 °C. Co 3+ was primarily in Co 3 O 4 , whereas Co 2+ was identified within both Co 3 O 4 and highly stable CoAl 2 O 4 ; however, Co 2+ /Co 3+ decreases continuously along with cobalt loading increase. In addition, CoAl 2 O 4 promotes ethylene formation. In Co 3 O 4 , Co 3+ is more susceptible to reduction to metallic Co 0 under the reaction atmosphere, promoting reverse water-gas shift (RWGS) reaction and finally enhancing oxidative dehydrogenation of ethane. These insights offer a valuable framework for the rational design of efficient and durable catalysts for the CO 2 -ODHE process.