Efficacy of modified carbon molecular sieve with iron oxides or choline chloride-based deep eutectic solvent for the separation of CO2/CH4

Abstract

It is necessary to separate CO₂ from biogas to improve its quality for the production of biomethane. Herein, an improvement in the separation of CO₂/CH₄ via adsorption was achieved by modifying the surface of CMS. The surface modification of CMS was performed by impregnation with metal oxide (Fe₃O₄) and N-doping (DES–[ChCl:Gly]). Subsequently, the efficacy of the surface-modified CMS was investigated. This involved CMS modification, material characterization, and performance analysis. The uptake of CO₂ by CMS–DES–[ChCl:Gly] and CMS–Fe₃O₄ was comparable; however, their performance for the separation of CO₂/CH₄ was different. Consequently, CMS–DES–[ChCl:Gly] and CMS–Fe₃O₄ exhibited ca. 1.6 times enhanced CO₂ uptake capacity and ca. 1.70 times and 1.55 times enhanced CO₂/CH₄ separation, respectively. Also, both materials exhibited similar repeatability. However, CMS–DES–[ChCl:Gly] was more difficult to regenerate than CMS–Fe₃O₄, which is due to the higher adsorption heat value of the former (59.5 kJ).