Preparation of N&O-doping and microporous carbon granules for effective CH4 adsorption and separation from low-concentration coal-bed methane

Abstract

Developing novel granular carbon adsorbents for CH4 adsorption and CH4/N2 separation is always a great challenge in the utilization of low-concentration coal-bed methane (CBM). Herein, the N&O-doping and microporous carbon granules are prepared from corn kernels via a facile and effective method. Noteworthy, neither binding agent nor KOH is used in preparation process. The resulting optimal corn kernels based carbon granules (CKCGs) adsorbent CKCGs-900-1 exhibits a high CH4 adsorption capacity of 1.31 mmol g-1 and IAST selectivity of 17.62 (CH4/N2=10/90 v/v) at 25 °C and 1 bar, which is superior or comparable to most of the reported powdery and shaped adsorbents. Above properties result from the synergistic effect of the microporous structure (micropores concentrated at 0.55 nm), functional groups (C-OH&COOH) and surface species (N-5&N-6). Dynamic breakthrough experiments approve that CH4/N2 mixtures can be well separated at ambient condition. Kinetics study shows that the CH4 adsorption on CKCGs-900-1 conforms to the Bangham model, exhibiting pore diffusion process. This work provides a useful strategy to develop potential materials for recovering CH4 from low concentration CBM.