The pore structure is an essential factor that influences the isothermal characteristics of methane adsorption of coal, and the pore structure is altered after methane adsorption. In this study, a high-rank coal sample was investigated via methane adsorption isothermal measurement, and changes in the pore structure were studied using low-pressure N2 adsorption and low-pressure CO2 adsorption before and after the methane adsorption. The excess adsorption capacity exhibits a rapid increase at low pressure, reaching a maximum when the test pressure is approximately 8 MPa. Following that, the excess adsorption capacity of the high-rank coal tends to decrease. After the methane adsorption, the pore volume and specific surface area of the micro-, meso-, and macropores increase as compared to those before the methane adsorption, especially for micropores with apertures greater than 0.8 nm and mesopores with apertures below 10 nm. This is mainly caused by high pressure in the methane adsorption, indicating a pressure effect on the pore structure after the methane adsorption. After the methane adsorption, the ratio of pores with various sizes in the high-rank coal is enhanced, but the connectivity for meso- and macropores presents a slight decrease.

中文翻译：

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高阶煤吸附甲烷等温特性及吸附甲烷前后孔隙结构变化

孔隙结构是影响煤吸附甲烷等温特性的重要因素，吸附甲烷后孔隙结构发生改变。本研究通过甲烷吸附等温测量对高阶煤样品进行了研究，利用低压N2吸附和低压CO2吸附研究了甲烷吸附前后的孔隙结构变化。过量吸附容量在低压下迅速增加，在测试压力约为 8 MPa 时达到最大值。随之，高阶煤的过剩吸附量趋于下降。甲烷吸附后，微孔、中孔和大孔的孔容和比表面积均比吸附前增加，特别适用于孔径大于 0.8 nm 的微孔和孔径小于 10 nm 的中孔。这主要是由于甲烷吸附中的高压引起的，表明甲烷吸附后孔隙结构受到压力影响。甲烷吸附后，高阶煤中各种大小孔隙的比例增加，但中孔和大孔的连通性略有下降。