Dual Function Materials for Point-Source and Direct Air Capture of CO2 and Combined Conversion to Fuel

Our research group developed dual function materials (DFM), comprised of a solid sorbent and metal catalyst nano-dispersed on the same high surface area carrier for capture and conversion in one reactor and at one temperature (320°C), as an alternative solution to common challenges of carbon capture and utilization technologies (i.e. high energy requirements and transportation needs). The DFM is able to selectively chemisorb CO₂ from an oxygen-containing flue gas and, within the same reactor, convert it to synthetic natural gas (methane) with the addition of renewable or waste H₂. Prior work showed that DFM (tablets of 5% Ru, 6.1% “Na₂O”/γ-Al₂O₃) are stable throughout a minimum of 50 adsorption and methanation cycles (using simulated flue gas conditions: 7.5% CO₂, 15% steam, 4.5% O₂). Our most recent work shows that the DFM also functions in the context of direct air capture (DAC) of CO₂ (Figure 1) at even lower Ru contents.

DFM is able to adsorb the dilute CO₂ (~400 ppm) from ambient filtered air which can be subsequently hydrogenated to methane. Because DAC technologies have free-range of geography, this technology can be aptly placed at emerging power-to-gas facilities to eliminate the requirement of transporting H₂. While an external heat source would be needed to achieve the operating temperature of 320°C in the DAC scenario, the temperature can be supplied by renewable H₂ sources, which would also be present at power-to-gas facilities (i.e. PEM fuel cell). In addition, because the adsorbent saturation time is long for DAC, the kinetics for methanation need not be as rapid as in the point-source case, allowing flexibility to operate the entire system at lower temperatures to minimize energy requirements. Simple desorption of the adsorbed CO₂ is also a viable way to regenerate the DFM, producing a stream of CO₂ for other utilization pathways or storage.