溶剂极性控制下的煤抽余物吸附甲烷能力研究

基于原煤和有机溶剂抽余物的等温吸附实验结果,对比分析溶剂极性与其煤抽余物吸附甲烷能力变化关系,探讨抽提溶剂极性差异对煤抽余物吸附甲烷能力控制的地球化学机理。结果表明,煤溶剂抽余物等温吸附甲烷曲线都遵循Langmuir方程,且二硫化碳(CS₂)和苯(C₆H₆)溶剂抽提作用增大了煤吸附甲烷量,四氢呋喃(THF)和丙酮溶剂抽提作用减小了煤吸附甲烷量。实验发现,煤抽余物吸附甲烷能力变化与抽提溶剂极性成负相关关系,该现象可用相似相容原理解释:CS₂和C₆H₆溶剂极性较弱,抽提出较多具有非极性结构(-CH₃和-CH₂-)的烷烃和芳烃,为甲烷在煤表面吸附增多了吸附位而增强了抽余物吸附甲烷能力,THF和丙酮溶剂极性较强,抽提出较多具有极性结构(-CHO、-OH、和-COOH)的非烃和沥青质,减少了吸附位而降低煤抽余物的甲烷吸附能力。

Methane adsorption capacity of extracted coals under control of solvent polarity

Based upon isothermal methane adsorption on raw and solvent extracted coals, relationship between solvent polarity and methane adsorption capacity change of the coal was analyzed, and the possible geochemical mechanism was discussed from polarity of the solvents. The results show that methane isothermal adsorption curves on the extracted coals follow the Langmuir equation. Extraction with CS₂ and C₆H₆ enhances methane adsorption capacities on extracted coals, and that with tetrahydrofuran (THF) and acetone is opposite. There is a negative correlation between methane adsorption capacity change of the coal and the solvent polarity, which can be explained by similarity-intermiscibility theory. The polarities of CS₂ and C₆H₆ are weaker, which can extract more alkane and aromatic hydrocarbons with nonpolar molecule structure (-CH₃ and -CH₂-) to increase the adsorbed space of coal surface for methane adsorption. The polarities of THF and acetone are stronger, which can extract more non-hydrocarbon and asphaltene with polar molecule structure (-CHO, -OH and -COOH) to reduce the adsorbed space of coal surface for methane adsorption.