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 degrees C. The carbon adsorbent samples were characterized with N-2 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 N-2 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/N-2 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/N-2 (47.3) and CH4/N-2 (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.