Efficacy of modified carbon molecular sieve with iron oxides or choline chloride-based deep eutectic solvent for the separation of CO 2 /CH 4 .

It is necessary to separate CO 2 from biogas to improve its quality for the production of biomethane. Herein, an improvement in the separation of CO 2 /CH 4 via adsorption was achieved by modifying the surface of CMS. The surface modification of CMS was performed by impregnation with metal oxide (Fe 3 O 4 ) 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 CO 2 by CMS-DES-[ChCl:Gly] and CMS-Fe 3 O 4 was comparable; however, their performance for the separation of CO 2 /CH 4 was different. Consequently, CMS-DES-[ChCl:Gly] and CMS-Fe 3 O 4 exhibited ca. 1.6 times enhanced CO 2 uptake capacity and ca. 1.70 times and 1.55 times enhanced CO 2 /CH 4 separation, respectively. Also, both materials exhibited similar repeatability. However, CMS-DES-[ChCl:Gly] was more difficult to regenerate than CMS-Fe 3 O 4 , which is due to the higher adsorption heat value of the former (59.5 kJ).