不同煤级煤的微孔介孔演化特征及其成因

为了探讨煤的微孔介孔演化特征及其成因，在华北二叠纪煤盆地，采取7个不同煤化程度的煤样，分别采用低压CO₂吸附法和液氮吸附法对各煤样的纳米孔隙进行表征；基于密度泛函理论、DA（Dubinin—Astakhov）、DR（Dubinin—Radushkevich）、BET、BJH等方程计算孔隙表面参数；分析煤的微孔（孔径<2 nm）和介孔（孔径2~50 nm）的孔径分布、孔容和比表面积随煤级变化的规律；并探讨微孔形成的主控因素及介孔的形成机制。研究结果表明:微孔孔容和比表面积与煤的镜质体反射率高度正相关，微孔在吸附中占绝对支配性主导地位；微孔孔径分布曲线呈双峰分布，不同煤级煤样的曲线形态相似，极微孔随煤级增加最快；介孔比表面积和孔容随煤级增加逐渐下降，介孔孔径分布呈单峰分布，随着煤级的增加，煤的BET比表面积先减少后增加，呈U形分布；微孔的形成应主要受控于煤的类微晶参数和芳香层片间的堆垛结构，而介孔的形成应主要受控于煤侧链的变化和煤的基本结构单元间隙。 

Evolution characteristics of micropore and mesopore of different rank coal and cause of their formation

In order to investigate the evolution of the structure characteristics of micropore and mesopore of different rank coal and the cause of their formation, 7 different metamorphic coal samples collected from North China Permian coal basin were tested using low-pressure nitrogen and carbon dioxide adsorption techniques respectively. The change rule of pore size distribution(PSD), pore volume(PV)and specific surface area(SSA)of micropores(pore diameter less than 2 nm) and mesopores(pore diameter lies in 2~50 nm) with different metamorphic degrees of coal were analyzed using density function theory(DFT), Dubinin-Astakhov(DA)method, Dubinin-Radushkevich (DR) method, BET and BJH formula. Then the cause of the formation of micropores and mesopores was discussed. The results show that: PV and SSA of micropores are positively correlated with its vitrinite reflectance, the micropore with pore diameter below 2 nm is the dominant factor in coal adsorption; PSD curves of micropores are of bimodal distribution, and different coal samples have similar PSD curves, the ultramicropore has a fastest increasing amount in the micropores; PV and SSA of mesopore decrease with increase of coal rank, and its PSD show unimodal distribution. With the increase of metamorphism, BET and SSA of coal decrease firstly and then increase with “U” pattern; The formation of micropores in coal is mainly controlled by the microcrystalline parameters and the stacking structure of the aromatic layer, while the formation of mesopores is mainly controlled by change of coal side chains and the space of basic structure unite.