Surface-modified spherical activated carbon materials for pre-combustion carbon dioxide capture

Abstract

Surface modification of activated carbon beads via HNO₃ oxidation and subsequent amination at elevated temperatures was investigated as a means to improve their performance for CO₂ capture, and the effects of the resultant changes in porosity and surface chemistry on adsorption characteristics of the samples were studied. Characterisations conducted with elemental analysis, physical adsorption, X-ray photoelectron spectroscopy and scanning electron microscope demonstrate that both the porosity and surface chemistry of the carbon beads were tuned by the modification without any alteration of the integrity of the desirable spherical morphology. Adsorption evaluation with both thermogravimetric analysis and high pressure volumetric analysis under various conditions indicate that one of the modified samples had a high CO₂ adsorption capacity (8.64 mmol g⁻¹ at 20 bar and 30 °C) with fast adsorption/desorption kinetics, superior durability and good selectivity over N₂ and H₂. Both the unique spherical form (diameter = 1.2 ± 0.2 mm) and the superior adsorption performance render the modified carbon beads a promising candidate for CO₂ capture especially in pre-combustion capture using pressure swing adsorption.