(618h) Scale up Considerations for CO2 Direct Air Capture (DAC) and Catalytic Conversion to Renewable Natural Gas Using a Dual Function Material (DFM) Washcoated Monolith

Catalytically converting captured CO₂ to hydrocarbons is a pathway to defossilize energy feedstocks for mitigating climate change. A promising technology is the dual function material (DFM), which integrates CO₂ capture and conversion to CH₄ (renewable natural gas, RNG) in a single reactor bed. The DFM is composed of an alkaline sorbent (“Na₂O”) and catalyst (Ru) co-dispersed on high surface area 𝛾-Al₂O₃. Previous work demonstrated its capabilities for point source capture and conversion, and recent work showed it can be adapted to direct air capture (DAC) and conversion. Current research examines a DFM washcoated monolith to minimize pressure drop associated with the high throughput of ambient air for DAC.

In the proposed scenario, the DFM selectively adsorbs CO₂ from ambient air. Once saturated, the temperature is increased to ~300°C and renewable H₂ is introduced for catalytic methanation. This method avoids costs of CO₂ compression and transportation for subsequent upgrading or sequestration, and RNG can be injected into the existing pipeline. The process is simulated in the laboratory to evaluate the cyclic performance of a DFM washcoated monolith. Performance metrics include capture and methanation capacities, CO₂ retention during pre-heating, and consistency. The DFM monolith shows good washcoat adhesion and excellent stability over 20+ cycles that simulate humid DAC conditions (Figure 1). Experiments examining the effect of cycling at partial capture capacity show better retention of CO₂ during temperature swing (Figure 2), supporting the belief that stronger sorbent sites are occupied first during adsorption.

Our research highlights the potential of the DFM to advance the shift towards sustainable energy practices. We will discuss experimental work that considers scale up objectives, including: a washcoated monolith for reduced pressure drop; testing in varying simulated DAC climates to scope the operating range; and evaluation of milder catalytic methanation conditions for energy and cost reduction.