Assessment of CaO-based sorbent/spinel catalyst composites for the oxidative dehydrogenation of ethane in isothermal integrated CO2 capture and utilization

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In this study, a comparative analysis of the isothermal integrated CO2 capture and utilization (ICCU) performance of MgB2O4 (B = Cr, Ga, Fe, Al)/CaCe15 was conducted. Results show that MgCr2O4/CaCe15 demonstrates exceptional performance, with CO2 uptake capacity, CO2 conversion, ethane conversion, ethylene selectivity, and ethylene yield after multiple cycles measuring at 0.22 g/g, 35.6 %, 19.6 %, 89 %, and 17.4 %, respectively. The dominant mechanism during the CO2 utilization stage was explored, and the coupling mechanism of catalytic dehydrogenation and reverse water–gas shift reaction is dominant. The reaction pathway during CO2 utilization was investigated, and results show that hydrogenation activation (CO2*+H* → HCOO* → CO*+OH*) is the primary pathway for CO2 dissociation, with the oxidative dehydrogenation of ethane mainly attributed to the activation of C–H on distinct C atoms, CH3CH3* → CH3CH2* → CH2CH2*. Meanwhile, the scission of the first C–H bond during CO2 utilization is the rate-determining step. Furthermore, we investigated the influencing factors and discovered that increasing the concentration of ethane and weight hourly space velocity both lead to a decrease in ethylene yield.