Synthesis of micro-mesoporous hierarchical structure of coal-based activated carbon and its effect on methane adsorption

Abstract

This research synthesized a series of porous carbon materials utilizing three different coal-rank samples as raw materials through carbonization and activation processes. The resulting activated carbon has a high specific surface area of up to 2092.83 m2/g, a micro-mesopores volume of 1.08 cm3/g and a hierarchical porous structure, and the surface is enriched with heteroatoms. These properties can be adjusted by adjusting the charging temperature, activation temperature and KOH/Coal mass ratio. Methane adsorption experiments showed that the maximum adsorption capacities of the three activated carbons at 40℃ were 7.97 mmol/g, 9.34 mmol/g, and 11.71 mmol/g (Langmuir parameter a), respectively. It was found that methane adsorption is primarily related to nanopores (0.5 nm −2 nm), with micropores playing a dominant role and mesopores supplying transport channels for gas molecules and contributing to their immobilization on solid surfaces. The results of the dynamic and static adsorption experiments were consistent, demonstrating that better adsorption separations could be attained for samples with stronger molecular affinities. Coal-based activated carbon shows potential as a material for low-concentration methane separation due to its superior affinity for methane molecules, providing theoretical support for the selection of materials for variable pressure adsorption.