Green synthesis of ultramicroporous carbons by in-situ ionic activation of coal-derived humic acids for efficient CH4/N2 separation

Coal-based porous carbon usually has broad pore size distribution, and it remains a major challenge for achieving controllable and optimized pore size distributions in the ultramicroporous (<0.7 nm) range. In this work, coal-derived humic acid-based carbons (HACs) were successfully synthesized by in-situ ionic activation, which consumed much less KOH than the traditional KOH activation method, demonstrating environmentally friendly advantages. The prepared HACs were characterized of the concentrated ultramicroporous pore size distribution. Importantly, ultramicroporous pore size of HACs could be controlled at the sub-angstrom level by slightly adjusting the KOH amount. Dynamic breakthrough experiments and PSA process simulations strongly demonstrated the superior and applicable separation performance of HACs for CH 4 /N 2 mixtures. The investigation extends the application of in-situ ionic activation in coal-based materials and provides a cheap, green, and efficient coal-based adsorbent for low-concentration coalbed methane enrichment.