(643e) Capture and Conversion of CO2 into Methane Using Catalytic Sorbent of NaNO3/MgO + Ru/Al2O3

A concerted process combining CO₂ capture and utilization can compliment traditional CO₂ capture processes, offering unique advantages, as storage and transportation of CO₂ can be removed, and the produced renewable fuel source can be directly used again in nearby plants. Specifically in case of CO₂ capture & methanation, the energy intensive temperature swing sorption process may also be removed by performing both steps under isothermal conditions. While first generation of catalytic sorbents, such as Ru/CaO/Al₂O₃, has previously been shown to be effective in this task, like all first generation materials, it has some drawbacks, including modest CO₂ sorption and methane production capacities.^[1] In this work, a catalytic sorbent composed of a physical mixture of NaNO₃/MgO and Ru/Al₂O₃, was examined for combined capture & conversion. A material comprised of 17% NaNO₃/MgO was found to be effective at capturing CO₂ under 10% CO₂/15%H₂O/N₂ flows akin to those in flue gas, showing 7.5 mmol CO₂/g sorption capacity. It was also capable of capturing and desorbing CO₂ over 8 cycles at isothermal conditions at 300 °C by switching the feed gas from CO₂ flow to inert flow.^[2]

To evaluate performance of the new catalytic sorbent synthesized, both CO₂ sorption capacity and methane production capacity, equivalent to number of moles of methane produced per mass of catalytic sorbent in one cycle of capture and methanation, were measured. A catalytic sorbent of 2:1 mass ratio of 17%NaNO₃/MgO and 0.5%Ru/Al₂O₃ showed a sorption capacity of 3.5 mmol CO₂/g, and methane production capacity of 1.3 mmol CH₄/g at 300 °C. Both the sorption capacity and methane production capacity are comparable to the highest values reported to date using flue gas relevant CO₂ concentrations (~10% CO₂), making such catalytic sorbents promising materials for further development of combined capture & conversion applications. Ongoing work targets assessment of reaction kinetics and elucidation of reaction pathways using these materials.

Reference:

(1) Duyar, M. S.; Treviño, M. A. A.; Farrauto, R. J. Dual Function Materials for CO₂ Capture and Conversion Using Renewable H₂. Appl. Catal. B Environ. 2015, 168–169, 370–376.

(2) Park, S.J.; Y. Kim.; Jones, C.W. NaNO₃ Promoted Mesoporous MgO for High Capacity CO₂ Capture from Simulated Flue Gas with Isothermal Regeneration. ChemSusChem 2020.