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 CO 2 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 liquidderived coal pyrolysis, namely phenolic oil, which was used as gel precursor before carbonization and KOH activation. CO 2 capture performances were determined at temperatures 2 between 25 and 120°C, with CO 2 concentrations ranging from 5 to 90 vol. %. The most efficient sample captured 2.86 mmol of CO 2 /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. CO 2 uptake was not affected by desorption temperature after six adsorption-desorption cycles. Based on the results obtained in this work, the role of the textural properties into the CO 2 capture at realistic postcombustion temperatures and partial pressures was elucidated. In particular, we concluded that CO 2 adsorption performance was more related to the volume of the narrowest pores and to the average pore size than to the surface area.

A Step Forward in Understanding the Hydrogen Adsorption and Compression on Activated Carbons

“…Although the kinetic diameters of N 2 and CO 2 are quite similar (3.6 and 3.3 nm, respectively), CO 2 physisorption at 273 K is a much faster process than that of N 2 at 77 K because molecular diffusion is highly temperaturedependent 50,51 . CO 2 adsorption isotherms give a reliable indication of porosity with a diameter of less than 1 nm because CO 2 is adsorbed in pores where N 2 cannot enter, within the set equilibrium times 50,52 .…”

“Green”, innovative, versatile and efficient carbon materials from polyphenolic plant extracts

“…Without treatment, they proved to be extremely hydrophobic materials (water contact angle higher than 157°) and were very efficient for selectively trapping, within a few seconds only, hydrocarbons such as heptane spread at the surface of water [118]. The same feature, associated with a rather high packing density, makes them very interesting for capturing CO2 in real conditions, i.e., from wet and hot (> 75°C) gaseous streams [119]. Activation dramatically increased the surface area and both the connectivity between micropores and mesopores and the oxygen content at the material surface.…”

Activated carbon xerogels derived from phenolic oil: Basic catalysis synthesis and electrochemical performances

“…The pore size distributions (PSDs) of the carbon materials were obtained by applying the Non-Local Density Functional Theory (2D-NLDFT, SAIEUS software) to both the N 2 and the CO 2 isotherms. The surface areas were calculated by applying: (i) the BET equation to the nitrogen isotherms as detailed in [22], leading to A BET (m 2 g -1 ); and (ii) the Non-Local Density Functional Theory (2D-NLDFT-HS), with SAIEUS software, to both N 2 and CO 2 isotherms, leading to S NLDFT (m 2 g -1 ) [23]. The surface areas of the micropores and mesopores, S micro and S meso (m 2 g -1 ), respectively, were calculated from the PSDs [22].…”

“…The surface areas were calculated by applying: (i) the BET equation to the nitrogen isotherms as detailed in [22], leading to A BET (m 2 g -1 ); and (ii) the Non-Local Density Functional Theory (2D-NLDFT-HS), with SAIEUS software, to both N 2 and CO 2 isotherms, leading to S NLDFT (m 2 g -1 ) [23]. The surface areas of the micropores and mesopores, S micro and S meso (m 2 g -1 ), respectively, were calculated from the PSDs [22]. The total pore volumes, V T and V NLDFT (cm 3 g -1 ), were determined from the N 2 isotherms and from the PSDs, respectively [22].…”

“…The surface areas of the micropores and mesopores, S micro and S meso (m 2 g -1 ), respectively, were calculated from the PSDs [22]. The total pore volumes, V T and V NLDFT (cm 3 g -1 ), were determined from the N 2 isotherms and from the PSDs, respectively [22]. The micropore volumes were calculated by applying: (i) the Dubinin-Radushkevich (DR) equation to the N 2 adsorption isotherms, leading to V µ-N2 (cm 3 g -1 ) [24]; (ii) the Dubinin-Radushkevich (DR) equation to the CO 2 isotherms, leading to V µ-CO2 (cm 3 g -1 ) [24]; (iii) the 2D-NLDFT-HS to both the N 2 and CO 2 isotherms, giving rise to V micro (w < 2 nm), V w<0.5 , V 0.5<w<0.7 and V 0.7<w<2 (cm 3 g -1 ) [22].…”