Novel Porous Carbon Adsorbents for CO2 Capture from Flue Gas and Natural Gas Upgrade

A few N-functionalized porous carbon adsorbents were synthesized and characterized for capturing carbon dioxide from flue gas and separating carbon dioxide from natural gas. The hydroquinone and quinone functional groups were grafted into a hierarchical porous carbon framework via Friedel-Crafts reaction for selective capture and removal of carbon dioxide from flue gases and natural gas. Adsorption isotherms of CO₂, CH₄, and N₂ were measured at 1 atm and three different temperatures, and used for predicting the carbon adsorbents’ separation capability by using the Ideal Adsorbed Solution Theory (IAST).  At 298 K and 1 atm, the highest CO₂/N₂ selectivity value of 26.5 is obtained on the hydroquinone-grafted carbon (OAC-1), which is significant improvement (158.7%) of the pristine porous carbon (OAC-0), and the highest CO₂/CH₄ selectivity value of 4.6 is obtained on the quinone-grafted carbon (OAC-2), 28.4% better than the pristine porous carbon. The CO₂ adsorption capacity on the modified activated carbon was increased from 3.02 mmol g^-1 to 3.46 mmol g^-1 at 298 K and 1 atm, although the specific surface area was reduced after modification. In addition, transient breakthrough simulations for CO₂/CH₄/N₂ binary mixtures were conducted to demonstrate the good separation performance in a fixed bed adsorber.  The heats of adsorption of carbon adsorbents are lower than other adsorbents, suggesting a low regeneration energy requirement. Overall the new porous carbon adsorbents developed in this work look very promising for flue gas treatment and natural gas upgrading.