Molten-Salt-Mediated Chemical Looping Oxidative Dehydrogenation of Ethane with In-Situ Carbon Capture and Utilization.

Abstract

The molten-salt-mediated oxidative dehydrogenation (MM-ODH) of ethane (C₂H₆) via a chemical looping scheme represents an effective carbon capture and utilization (CCU) method for the valorization of ethane-rich shale gas and concurrent mitigation of carbon dioxide (CO₂) emissions. Here, stepwise experimentation with Li₂CO₃-Na₂CO₃-K₂CO₃ (LNK) ternary salts (i) assessed how each component of the LNK mixture impacted ethane MM-ODH performance and (ii) explored physicochemical and thermodynamic mechanisms behind melt-induced changes to ethylene (C₂H₄) and carbon monoxide (CO) yields. Of fifteen screened LNK compositions, nine exhibited ethylene yields greater than 50 % at 800 °C while maintaining C₂H₄ selectivities of 85 % or higher. LNK salts rich in Li₂CO₃ content yielded more ethylene and CO on average than their counterparts, and net CO₂ capture per cycle reached a maximum of ~75 %. Extended MM-ODH cycling also demonstrated long-term stability of a high-performing LNK medium. Density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations suggested that the molten salt does not directly activate C₂H₆. Meanwhile, an empirical model informed by experimental data and reaction thermodynamics adequately predicted overall MM-ODH performance from LNK composition and provided insights into the system's primary drivers.