Exploiting Activated Carbon Felt as a Selective Adsorbent for Removal of CO ₂ from Methane in a Pressurized Fixed-Bed Column

This work investigates commercial activated carbon felt (ACF) as a selective adsorbent for CO2 separation from methane in pressurized fixed-bed columns, for potential use in off-shore natural gas purification. Pristine ACF was chemically modified, aiming to improve its adsorption capacity, followed by comprehensive characterization using TGA, XRD, FT-IR, N2 physisorption, SEM, and XPS to evaluate the textural properties and surface chemistry of the material. Breakthrough curves for CO2 uptake were obtained at 35 °C, up to 10 bar, for both the individual gases and binary CO2 and CH4 mixtures. The pristine ACF presented a high specific surface area (1946 m2 g–1), a microporous structure, and limited surface oxygen groups, resulting in an exceptional experimental CO2 adsorption capacity of 12.2 mmol g–1 at 10 bar and a CO2/CH4 selectivity ratio of 6.7, comparable to that of commercial zeolite 13X. Surface oxidation with nitric acid increased the quantity of oxygen groups, but severely degraded the textural properties, reducing adsorption performance. The results showed that the adsorption on ACF was primarily governed by the textural properties, with the pristine ACF outperforming several benchmark materials, including amino-MOFs and functionalized carbons. The findings highlighted commercial ACF as a promising low-cost and scalable adsorbent for natural gas decarbonization in pressure swing adsorption (PSA) systems.