Pore structure, adsorptivity and influencing factors of high-volatile bituminous coal rich in inertinite

•The connectivity of adsorption and seepage pore increased after FCJ.•The adsorption pore heterogeneity of coal increased with Rr and inertinite content.•The VL is controlled by maceral, and Rr, before and after FCJ, respectively.•Bitumen has an important effect on micropores and adsorptivity of bituminous coal. Bituminous coal rich in inertinite is widely distributed throughout the world, but the effect of the first coalification jump (FCJ) on the reservoir properties of high-volatile bituminous coal rich in inertinite, has rarely been studied. Therefore, nine coal samples were collected from the southwestern Ordos Basin and used in a series of experiments designed to study the adsorptivity of high-volatile bituminous coal rich in inertinite and factors affecting adsorptivity before and after FCJ. Such information is helpful for further understanding the evolution of coal physical properties in the key stage of early coalification. The pyrolytic parameters indicate that the FCJ of the coal samples was between 0.60% and 0.65% (Rr). The NMR-T2 spectrum type of the samples was bimodal differentiation before FCJ, and after FCJ, it was a bimodal connection or adsorption single peak. The fractal dimension of adsorption pore increased with increased Rr and inertinite content. The adsorptivity of coal were affected by coalification and macerals. Langmuir pressure was mainly controlled by the maceral composition and exhibited a positive linear relationship with the ratio of vitrinite to inertinite. Langmuir volume was mainly controlled by maceral composition, and coalification, before and after FCJ, respectively. The increase in the adsorption pore volume of high-volatile bituminous coal caused by the increase in inertinite content had little effect on the increase in the adsorption capacity of the coal. In the stage of high-volatile bituminous coal, bitumen is adsorbed by vitrinite, which blocks and fills the pores of vitrinite, thereby reducing the adsorption capacity of coal.