Highly microporous nitrogen-doped carbons from anthracite for effective CO2 capture and CO2/CH4 separation

Abstract

The goal of this study is to develop a cost-efficient carbon adsorbent for effective CO2 capture and CO2/CH4 separation. Using anthracite as the precursor, highly microporous nitrogen-doped (N-doped) carbons are fabricated through a combination of KOH activation and urea treatment. The as-prepared carbon samples possess developed microporosity and large nitrogen content. The sample synthesized under mild KOH/anthracite ratio (KOH/anthracite = 2), following with urea treatment shows a remarkable CO2 uptake of 4.46 mmol g−1, among the highest achieved for N-doped porous carbons. This high CO2 capture capability should be attributed to the synergistic effect of large amount of narrow micropores (pore with＜1 nm) and nitrogen doping in the carbon adsorbent. Experiment evidence suggests that nitrogen doping contributes much on CO2/CH4 selectivity than that on CO2 capture. According to ideal adsorption solution theory (IAST), assuming different binary mixture proportions of 50/50, 30/70 and 15/85, the sample possessing the largest nitrogen content (6.48 wt %) exhibits CO2/CH4 IAST selectivities of 8.83, 7.02 and 8.09, respectively. Combining excellent CO2 capture capacity and desirable CO2/CH4 separation property, the microporous N-doped carbons prepared in this work appear to be a very promising candidate for greenhouse gas treatment and natural gas upgrading.