Effect of Porosity and Surface Chemistry on CO2 and CH4 Adsorption in S-Doped and S-/O-co-Doped Porous Carbons

Abstract

The aim of this study was to determine the adsorption performance of a petroleum pitch-based activated carbon (PPAC1:3) before and after a post-treatment with H2S. In the first step, a microporous activated carbon (PPAC1:3) with a highly developed porous structure was produced through a chemical activation route with KOH. Afterward, the synthesized activated carbon was thermally treated yielding two different series of functionalized activated carbons: (i) a series of carbons were treated directly with H2S at elevated temperatures (600 °C and 800 °C), and (ii) a series of carbons were generated by combining an oxidation treatment with plasma followed by H2S treatment at elevated temperatures (600 °C and 800 °C). The chemical and structural characteristics of the S-doped and S-/O-co-doped porous carbons were investigated by means of different experimental techniques, such as XRD, RAMAN, FESEM, XPS, TPD, N2, and CO2 adsorption, and finally tested in CO2 and CH4 adsorption at atmospheric and high pressure. The functionalized porous carbons possessed specific surface areas of 2420–2690 m2/g, total pore volume of 1.05–1.18 cm3/g, and sulfur content up to 2.55 atom % (the sulfur content of the original carbon was 0.19%). After a careful analysis of the carbon dioxide and methane uptake at atmospheric (0.1 MPa) and high pressure (4 MPa), adsorption results confirm that the microporous structure is the main structural parameter defining the adsorption performance and, to a lower extent, the surface chemistry. Overall, a significant improvement in the total uptake can be appreciated after the H2S treatment.

Nanoporous carbons for the electrochemical reduction of CO2: Challenges to discriminate the roles of nanopore confinement and functionalization

“…Again, important lessons learned from the field of adsorption should be borne in mind. Micropores (< 2 nm) and narrow micropores (< 0.7 nm) are known to govern the adsorption of CO 2 at atmospheric pressure in nanoporous carbons, whereas wider micropores and small mesopores define the uptake at high pressures [41][42][43][44]. Analogously, high surface areas and micropore volumes seem to favor the electrocatalytic conversion of CO 2 [26,27,29,40], although the dependence with different performance indicators is not clear due to the diversity of compositions (Figures 2C, 2D).…”

New Pillar-MOF with Nitrogen-Donor Sites for CO2 Adsorption

“…An excellent advantage, since CO 2 adsorption is attributed to a well-established pore structure that integrates both narrow and wide micropores. Narrow micropores play a crucial role in adsorption at atmospheric pressure, while wider micropores and small mesopores are essential for adsorption at high pressure …”

“…Narrow micropores play a crucial role in adsorption at atmospheric pressure, while wider micropores and small mesopores are essential for adsorption at high pressure. 9 Furthermore, the adsorption of CO 2 molecules is mostly given onto the porous material by physical interactions; therefore, less energy is required for sorbent regeneration when compared to traditional amine solvents. 1 Activated carbon shows superior CO 2 uptake than zeolites, but the interaction between CO 2 molecules and activated carbon is weak, making this adsorbent sensitive to temperature, leading to a loss in selectivity.…”