Influence of oxidation upon the CO2 capture performance of a phenolic-resin-derived carbon

The effect of oxidation upon the CO2 capture performance has been studied taking a phenolic resin carbon as the base material. Oxygen surface groups were introduced through liquid and gas phase oxidation treatments, using ammonium persulfate, nitric acid and air, respectively. The surface chemistry of the final carbon is strongly affected by the type of oxidation treatment: liquid phase oxidation introduces a greater amount of oxygen, mostly as carboxylic groups; these are absent in the gas phase oxidised sample that contains mainly ether and carbonyl functionalities. The porous texture of the samples is also affected by the oxidation treatment: through liquid phase oxidation the pore volume is somewhat reduced, while this is slightly developed by air treatment at 693 K. Despite the reduction in the porous volume and the acidic surface, liquid-phase oxidised samples present greater CO2 adsorption capacity than the starting carbon due to Lewis acid–base interactions with the CO2 molecule. Moreover: oxidised samples are easily regenerated, and observed heats of adsorption are typical from physisorption processes, which will facilitate the adsorbent regeneration in cyclic adsorption processes. Oxidation is therefore proposed as a plausible modification technique for developing easy-to-regenerate carbon adsorbents with enhanced CO2 capture performance.