Influence of Tectonically\nDeformed Coal-Based Activated\nCarbon and Its Surface Modification on Methane Adsorption

Abstract

A series of coal-based activated carbons (CACs) were\nsynthesized\nfrom mylonitized fat coal, a type of tectonically deformed coal (TDC)\nand symbiotic primary structural coal (PSC), followed by oxidative\nmodification. The pore structure, surface oxygen-containing functional\ngroups, and their influence on methane adsorption by CAC as the simplified\ncoal model were investigated by using low-temperature nitrogen adsorption,\nFourier transform infrared spectroscopy, Boehm titration, and X-ray\nphotoelectron spectroscopy. The results showed that tectonic deformation\nfostered smaller pores, particularly ultramicropores in TDC, dominating\nmethane adsorption. Acid-modified TDC-based activated carbons (ACs)\nshowed higher pore parameters and oxygen-containing functional groups\nthan those of PSC-based ACs. Nitric acid introduced abundant carboxyl\ngroups concurrently increasing the pore volume and specific surface\narea (SSA), while sulfuric acid–ammonium persulfate treatment\nresulted in increased lactone groups and a partial collapse/blockage\nof nanopores. Methane adsorption experiments confirmed the importance\nof micropores and revealed a significant decrease in capacity owing\nto increased oxygen-containing functional groups as the primary role,\nwith pore wall corrosion playing a secondary role. Thus, the study\nhighlights the surface effects of TDC on methane adsorption and the\npotential for producing high-performance methane storage materials\nfrom China’s tectonic coal resources.