Difference in Nanopore Structure Between Bituminous Coal and High-Grade Anthracite Caused by Magmatic Intrusion

The nano-pore distribution and structure characteristics ranging from 1.9 nm to 350 nm and the adsorptive capacity of the bituminous coal and high-grade anthracite caused by magmatic intrusion were studied by the low-temperature nitrogen adsorption test, scanning electron microscope (SEM) and isothermal adsorption experiment. The coal samples were collected from No. 13 coalmine, Pingmei Shenma Group, Henan Province, China. The principle of low-temperature nitrogen adsorption test was summarized in detailed, as well as the calculation process of the specific surface area, pore volume, and their distribution characteristics at different aperture. The results show that: (1) from bituminous to high-grade anthracite, the pore volume increase from 0.0018 cm³/g to 0.1802 cm³/g, the specific surface area increase from 0.663 m²/g to 194.864 m²/g, which means many new pores generated in magmatic thermal metamorphism; (2) the median pore diameter decrease from 101.81 nm to 1.32 nm significantly, which means most of the new pores are micro-mesopores; (3) the pore structure of most pores change from barrel shaped semi-closed pore to slit pore with slab or conical structure; (4) the adsorption capacity (Langmuir volume) remarkably reduce from 26.26 m³/t to 8.37 m³/t.