黔西滇东镜煤CS2抽余物的甲烷吸附特征及地球化学机理

Adsorption characteristics of CS_2-extracted vitrains from western Guizhou and eastern Yunnan and its geochemical mechanism

基于黔西—滇东5套镜煤及其CS2抽余物的等温吸附实验和傅里叶变换红外光谱(FTIR)结果,对比分析了原煤及抽余物的吸附特征和结构官能团特征,探讨了CS2抽提对煤吸附性改造的地球化学机理.结果表明:CS2的抽提作用改变了煤吸附性特征,其改变方向和幅度受煤化作用程度高低控制;抽提作用减小了煤中产烃相关结构官能团和含氧官能团等2类结构官能团含量,其减小幅度同样取决于煤化作用程度高低.发现第2次煤化作用跃变对镜煤抽余物吸附性改变及其结构官能团含量改变起关键作用,镜煤抽余物的吸附性改变和其2类结构官能团含量改变差值之间具有同步响应.认为具有产烃相关结构官能团特征的烷烃及芳烃等非极性分子的溶出增强了煤抽余物吸附性,具有含氧结构官能团特征的非烃和沥青质等极性分子的溶出减弱了煤抽余物的吸附性,煤化作用程度控制下CS2抽提作用对煤中2类结构官能团含量的改变是其吸附性改变的根本原因.

Based on the data of isothermal adsorption and Fourier Transform Infrared Spectroscopy（FTIR）of 5sets of raw and CS2-extracted vitrains from western Guizhou and eastern Yunnan,the characteristics of adsorption and functional groups of raw coal and extracted vitrains were comparatively analyzed.The geochemical mechanism of adsorption was discussed.The results show that CS2 extraction changes the adsorptivity of coals and the change direction and magnitude are controlled by the coalification degree.The extraction reduces contents of hydrocarbon generating and oxygen-containing functional groups in extracted coals,and the reduce magnitude also depends on the coalifcation degree.The second coalification jump playsakey role in the changes of the adsorptivity and the contents of functional groups.There is a synchronous response between the adsorptivity and the D-value of functional group contents of extracted coals.The adsorptivity of extracted coals is enhanced by extracted non-polar molecules like alkanes and aromatics and weakened by extracted polar molecules like nonhydrocarbons and asphaltenes.The CS2 extraction induced variation in contents of the two functional groups is the fundamental reason of the adsorptivity change under the control of coalifcation degree.