Synergetic effect of carbon nanopore size and surface oxidation on CO2 capture from CO2/CH4 mixtures

• Published in: Journal of colloid and interface science Vol. 397; pp. 144 - 153
• Main Authors: Furmaniak, Sylwester, Kowalczyk, Piotr, Terzyk, Artur P., Gauden, Piotr A., Harris, Peter J.F.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.2013
• Subjects: adsorbents; adsorption; Adsorptive separation; Carbon; Carbon capture and storage; Carbon dioxide; CO2 capture; Coalbed methane recovery; Indexing in process; Mathematical models; methane; Molecular simulations; Monte Carlo method; Nanomaterials; nanopores; Nanostructure; oxidation; Oxidized carbonaceous materials; Separation; Surface chemistry; synergism; thermodynamics; Adsorptive separation; CO2 capture; Coalbed methane recovery; Oxidized carbonaceous materials; Molecular simulations
• ISSN: 0021-9797; 1095-7103; 1095-7103
• DOI: 10.1016/j.jcis.2013.01.044

[Display omitted] ► The influence of porosity and surface chemistry is systematically studied. ► Surface oxidation is a far more important factor than carbon nanoporosity. ► Optimal carbon should consist of narrow carbon pores decorated oxygen functionalities. We have studied the synergetic effect of confinement (carbon nanopore size) and surface chemistry (the number of carbonyl groups) on CO2 capture from its mixtures with CH4 at typical operating conditions for industrial adsorptive separation (298K and compressed CO2CH4 mixtures). Although both confinement and surface oxidation have an impact on the efficiency of CO2/CH4 adsorptive separation at thermodynamics equilibrium, we show that surface functionalization is the most important factor in designing an efficient adsorbent for CO2 capture. Systematic Monte Carlo simulations revealed that adsorption of CH4 either pure or mixed with CO2 on oxidized nanoporous carbons is only slightly increased by the presence of functional groups (surface dipoles). In contrast, adsorption of CO2 is very sensitive to the number of carbonyl groups, which can be examined by a strong electric quadrupolar moment of CO2. Interestingly, the adsorbed amount of CH4 is strongly affected by the presence of the co-adsorbed CO2. In contrast, the CO2 uptake does not depend on the molar ratio of CH4 in the bulk mixture. The optimal carbonaceous porous adsorbent used for CO2 capture near ambient conditions should consist of narrow carbon nanopores with oxidized pore walls. Furthermore, the equilibrium separation factor was the greatest for CO2/CH4 mixtures with a low CO2 concentration. The maximum equilibrium separation factor of CO2 over CH4 of ∼18–20 is theoretically predicted for strongly oxidized nanoporous carbons. Our findings call for a review of the standard uncharged model of carbonaceous materials used for the modeling of the adsorption separation processes of gas mixtures containing CO2 (and other molecules with strong electric quadrupolar moment or dipole moment).