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

Abstract

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.