Chemical modification of carbon powders with aminophenyl and aryl-aliphatic amine groups by reduction of in situ generated diazonium cations: Applicability of the grafted powder towards CO2 capture

Aminophenyl, p-aminobenzyl and p-aminoethylphenyl groups were grafted at the surface of carbon Vulcan XC72R by spontaneous reduction of the in situ generated diazonium cations from the corresponding amine. X-ray photoelectron spectroscopy and elemental analysis confirmed an amine loading of about 1 mmol/g. The grafting of amine functionalities leads to a decrease of specific surface area from 223 to about 110 m2/g with a drastic loss of microporosity. Acid–base properties of the surface are also affected by the modification. Aminophenyl grafted groups make the surface more acidic while aryl-aliphatic amines groups tends to render it more basic. The grafted layer shows in each case a good thermal stability up to 250 °C. The affinity of the modified powder towards CO2 and N2 has been evaluated by thermal swing adsorption. The maximum adsorption capacity of CO2 of modified carbons is lower than the unmodified carbon but the presence of the amine functionalities involves a better selectivity of the material towards CO2 adsorption in comparison of N2 adsorption.