Synthesis of millimeter-sized porous carbon spheres derived from different precursors for CO2 capture

Activated carbon spheres (ACSs) with high surface area and controlled microporous structure were prepared from alkyl phenols and formaldehyde via suspension polymerization and steam activation. The effects of different phenolic resin precursors to ACSs on the textural structure and CO2 adsorption capacity were investigated. The pyrolysis behavior and surface chemistry of the alkyl phenolic resin spheres were characterized by thermal gravimetric, FTIR, XRD and XPS. The texture properties of the obtained ACSs were characterized by N2 adsorption–desorption and scanning electron microscope (SEM). Results showed that the as-prepared ACSs were basically microporous, and exhibited a surface area value as high as 1803.44 m2/g and a total pore volume of 0.96 cm3/g. The maximum CO2 adsorption capacity of the ACSs can reach 4.53 mmol/g and 13.62 mmol/g at 25 °C under 1 bar and 6 bar. The CO2 adsorption capacity had a good linear correlation with the micropore volume at higher pressures. The thermodynamic parameters indicate that physical adsorption mechanisms for CO2 adsorption mainly exist in the ACSs. In addition, the prepared ACSs are easily regenerated and shows a great recycling stability after multiple cycles.