The purpose of this work was to prepare coals with various pore structures, and investigate both microporosity development and corresponding methane adsorption capacities. A series of coal samples have been prepared by ultrasonic bath, and characterized by N2 adsorption and scanning electron microscopy (SEM) to obtain the pore structure and surface morphology of the samples. Methane adsorption measurement was conducted in the temperature range 25~55 °C and at pressures of up to 3.5 MPa. The Langmuir equation was applied to fit the experimental data, and the result showed the methane uptake correlated to the micropore volume and surface area, provided by the adsorption of N2 at 77 K. The surface area, pore volume, pore size distribution and surface morphology of the coal have changed significantly when treated for 10 min, resulting in the maximum of methane adsorption capacity. With the time further increasing, the surface area, pore volume and microporosity of the coal samples were reduced, along with the decrease of methane adsorption capacity. It can be concluded that the surface area, pore volume and microporosity had positive correlations with the amount of methane adsorption. The attenuation coefficient of the saturated adsorption amount over the coal samples substantially presented an inverse ‘U-shape’, indicating that the variation of the saturated adsorption amount was mainly controlled by the pore structure. Moreover, the temperature had a certain relationship with the attenuation coefficient of the saturated adsorption amount.
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