Nitrogen-Functionalized Porous Carbons for Enhanced CO2 Capture

Nitrogen-Functionalized Porous Carbons for Enhanced CO<sub>2</Sub> Capture

Peter C. Psarras, Jiajun He, Jennifer Wilcox, Energy Resources Engineering, Stanford University, Stanford, CA

Separations Division

"CO2 Capture by Adsorption II: Adsorbents"

The global consequences of increased anthropogenic carbon dioxide emissions are well documented. To avoid the catastrophic long-term damages associated with climate change, much attention has been devoted to the development of CO₂ emission mitigation strategies. One of the more mature methods involves CO₂ absorption via amine-based solvents; however, this technology is notoriously energy intensive, as amine regeneration requires high regeneration temperatures. Additionally, this process is water-intensive, a factor that is becoming increasingly important in drought-ridden states like California. Solid sorbents represent an alternative method for CO₂ capture, with liquid solvents replaced by (typically) large surface area, carbon-based porous frameworks. These sorbents are generally low-cost, easily fabricated, and are far less energy intensive in terms of regeneration. Further, their design can be customized through the inclusion of surface-functionalized groups. Unfortunately, current sorbents display CO₂ uptakes that are deemed too low to be cost-competitive with traditional solvent-based scrubbing. Nitrogen-functionalization of these porous carbons could result in more efficient CO₂ capture, owing to the same chemistry exploited by basic solvents in capturing acidic CO₂. Similar studies have examined the effects of oxygenated functional groups on CO₂ uptake and selectivity over N₂.

This studt will employ grand canonical monte carlo methods to explore the effect of quaternary, pyridinic, pyrollic, and oxidized-N groups on CO₂ uptake in porous carbon sorbents. Doping amounts will be varied to ascertain the optimum coverage for CO₂ capture. Additionally, gaseous mixtures of CO₂/N₂ and CO₂/N₂/H₂O will be examined to assess CO₂ selectivity. Theoretical performance will be validated through comparison with experimentally obtained CO₂/N₂ isotherms over fabricated hierarchial micro/mesoporous N-doped carbon sorbents. The combination of these methods will help to inform on sorbent design by illustrating which groups are most important for enhanced CO₂ uptake. Design to include more of a particular functional group can be achieved through, for example, a change in carbonization temperature.