Novel porous carbons derived from coal tar rejects: Assessment of the role of pore texture in CO₂ capture under realistic postcombustion operating temperatures

Activated carbons (ACs) are among the most commonly used sorbents for CO₂ capture because of their high surface areas and micropore volumes, which depend on precursor and activation methods. In this study, we evaluated different ACs obtained from a low-value fraction of liquid-derived coal pyrolysis, namely phenolic oil, which was used as gel precursor before carbonization and KOH activation. CO₂ capture performances were determined at temperatures between 25 and 120 °C, with CO₂ concentrations ranging from 5 to 90 vol %. The most efficient sample captured 2.86 mmol of CO₂/g AC at 25 °C and 1 bar, which is a highly competitive capture capacity, comparable to previously reported values for ACs without any modification/functionalization. Finally, their thermal stability and cyclability (i.e., for a minimum of six adsorption-desorption cycles) were evaluated. CO₂ uptake was not affected by desorption temperature after six adsorption-desorption cycles. On the basis of the results obtained in this work, the role of the textural properties into the CO₂ capture at realistic postcombustion temperatures and partial pressures was elucidated. In particular, we concluded that CO₂ adsorption performance was more related to the volume of the narrowest pores and to the average pore size than to the surface area.