Nitrogen-doped porous carbons for highly selective CO2 capture from flue gases and natural gas upgrading

Nitrogen-doped microporous activated carbon adsorbents were synthesized by a self-template method with KOH as the porogen agent at pyrolysis temperatures of 600, 700, and 800 °C. The carbon adsorbent samples were characterized with N2 adsorption at 77 K, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal gravimetric analysis, Raman spectroscopy, Fourier transformed infrared spectroscopy, and energy-dispersive X-ray spectroscopy mapping. Single component gas adsorption equilibrium of CO2, CH4, and N2 on the carbon adsorbents were measured at gas pressures up to 100 kPa and temperatures of 273, 298, and 323 K. Adsorption breakthrough performance of a fixed bed packed with the carbon adsorbents for separation of CO2/CH4/N2 gas mixture was simulated using the adsorption equilibrium data collected in this work. A high CO2 adsorption capacity (6.36 mmol g−1 on N-AC 600 at 100 kPa and 273 K) and large selectivites for the separation of CO2/CH4 (9.2), CO2/N2 (47.3) and CH4/N2 (3.6) mixtures were achieved with the carbon adsorbents due to their N-containing groups, narrow pore size distribution, and large specific surface area. The nitrogen-doped porous carbon adsorbents look very promising for flue gas treatment and natural gas upgrading applications.