Novel Porous Carbons Derived from Coal Tar Rejects: Assessment of the Role of Pore Texture in CO2 Capture under Realistic Postcombustion Operating Temperatures.

Abstract

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.