Effects of supercritical CO2 on micropores in bituminous and anthracite coal

•Investigating the effects of scCO2 on micropores in coals of different ranks.•Identifying the effects of scCO2 on chemical structure and organic groups of coals.•The coal rank has a positive influence on the micropore volume. The effects of supercritical CO2 (ScCO2) on coal micropores play a critical role in determining the CO2 capacity of coalbeds. To investigate the effects of ScCO2 on micropores in coals of different ranks under a range of temperature and pressure conditions, CO2 sequestration processes are replicated using a ScCO2 geochemical reactor. Four samples of coal of different ranks are exposed to ScCO2 and water for 240 h at 62.5 °C and 15 MPa, and CO2 adsorption tests, Fourier transform infrared spectroscopy, and X-ray diffraction are performed to determine the volume and pore size distribution of the micropores, the types and contents of the organic groups, and the aromatic crystallite structures of the coal samples before and after the ScCO2-H2O treatment. The influence of the chemical structure and the organic groups of the coal on the coal micropores is then studied. Micropores with widths 0.46 nm in semi-anthracite and