Assessment of Cao-Based Sorbent/Spinel Catalyst Composites for the Oxidative Dehydrogenation of Ethane in Isothermal In-Situ Co2 Capture and Utilization

Abstract

In this study, a comparative analysis of the isothermal in-situ 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, with abundant acid and basic sites within MgCr2O4/CaCe15 contributing to its outstanding performance. 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.

Keywords: in-situ CO2 capture and utilization, oxidative dehydrogenation, dual functional materials, CaO-based sorbent, spinel catalysts