(124g) Feasibility Study of Combining Direct Air Capture of CO2 and Methanation with Dual Function Materials (DFM)

A dual function material (DFM) is comprised of an alkaline adsorbent and catalytic metal supported on the same porous carrier. It was originally developed in our group for CO₂ capture from power plant effluents with subsequent catalytic methanation using renewable H₂. Methane is a useful feedstock for fuel and/or chemicals. The DFM allows for the capture and conversion of CO₂ to occur using a single material in a single reactor. This eliminates the need to transport the captured CO₂ for utilization, reducing energy requirements and costs associated with CO₂ compression. In the power plant application, the capture/catalytic conversion operation is carried out isothermally at flue gas temperature (320°C), further reducing energy requirements.

We have demonstrated that the DFM is also able to selectively chemisorb the dilute CO₂ (~400 ppm) from ambient filtered air which can be subsequently catalytically hydrogenated to methane (Figure 1). Because direct air capture (DAC) technologies have free-range of geography, this technology has the added advantage of being aptly placed at emerging power-to-gas facilities or facilities with waste H₂ to eliminate the requirement for transporting H₂. Consequently, DFM relies solely on existing natural gas infrastructure for distribution.

Given the large volumes of ambient air that require processing, the cycle of CO₂ adsorption and methanation must be conducted in a temperature swing operation. We capture CO₂ at ambient temperature (i.e. 25°C) followed by heating to T>200°C in H₂ for methanation. Successful cyclic capture of 400 ppm CO₂/air at 25°C and subsequent methanation has been demonstrated. We also demonstrate that feed flowrates and cycle durations can be tailored to achieve high adsorption kinetics and high capture capacities, allowing for high rates of methane production. Cyclic operation with the DFM is also possible in the presence of humid ambient air, proving that DFM has further potential for DAC application.