小分子有机物对煤吸附瓦斯特性影响机理

Small molecule organics containing many active functional groups are the important part of the coal, which can provide important sites for methane sorption. And the gas can be dissolved in them under high pressure. Small molecule organics have great influence on coal gas adsorption. Small molecule organics in the coal are taken as the research object in this project. Different rank coals were extracted with different solvents by microwave-assisted extraction. Compounds similar to extracts structure containing different functional groups were adopted as the model compounds. The adsorption heat of model compounds for methane was measured in porous media. And then, combining with measurement data of their methane dissolved, methane adsorption and dissolution characteristics of different small molecule organics were analyzed. The methane isotherm adsorption experiments of raw and residual coal were carried out at different temperatures, and their adsorption thermodynamic characteristics were analyzed. The methane adsorption behavior of coal macro-molecular structure that contains different content of small molecule organics with different functional groups was studied by using the molecular dynamics theory. Small molecule organics influencing on methane adsorption capacity and adsorption configurations was analyzed. Finally, the mechanism of small molecule organics influencing on coal gas adsorption characteristics was elaborated on micro level. This study is helpful to improve the coal adsorption gas theory, provides a theoretical basis for realizing simultaneous exploitation of coal and gas and prevention and control of gas disaster.

小分子有机物是煤的重要组成部分，其富含甲基、羰基等活性官能团可为瓦斯提供重要的吸附位，且高压下可溶解一定量的瓦斯，对煤吸附瓦斯产生重要影响。本项目以煤中小分子有机物为研究对象，对不同变质程度煤进行微波辅助萃取，依据萃取物成分检测结果，选取类似萃取物结构含不同官能团的模型化合物，测试多孔环境下含不同官能团的模型化合物的甲烷吸附热，结合其溶解甲烷实测数据，分析不同小分子有机物的甲烷吸附与溶解特性；开展原煤和残煤在不同温度下的甲烷等温吸附实验，并分析其吸附热力学特征，运用分子动力学理论研究含不同量、不同官能团小分子有机物的煤大分子结构的甲烷吸附行为，分析小分子有机物对甲烷吸附量、吸附构型的影响。最终从微观层面阐述小分子有机物对煤吸附瓦斯特性的影响机理。研究成果有助于完善煤吸附瓦斯理论，为实现煤与瓦斯共采及瓦斯灾害防治提供理论基础。

小分子有机物是煤的重要组成部分，其富含甲基、羰基等活性官能团可为瓦斯提供重要的吸附位，且高压下可溶解一定量的瓦斯，势必会对煤吸附瓦斯产生重要影响，但小分子有机物对煤吸附瓦斯特性影响规律及机理缺乏深入研究。本项目立足于煤体本身物质组成，在实测萃取物成分的基础上，理论计算分析了不同小分子有机物对煤吸附甲烷的影响规律，并结合原煤、残煤和含油煤的等温吸附实验数据，分析了原煤和残煤吸附热力学特征，进而揭示了小分子有机物对煤吸附瓦斯的影响机理。通过3年的研究，主要研究成果如下：.1）采用色谱质谱联用仪检测了可溶有机质成分，萃取物以芳香烃为主，主要是含1-2苯环的苯系衍生物和2-3苯环的稠环芳香烃；脂肪烃则主要为正构烷烃，且大多数具有奇碳优势；杂原子化合物主要是含氧原子的衍生物。.2）开展了不同温度下原煤和残煤的甲烷等温吸附实验，理论分析了原煤和残煤的吸附热力学参数变化规律，发现萃取后残煤的初始等量吸附热均低于原煤，煤吸附瓦斯能力降低了；结合含油煤的甲烷等温吸附实验，发现煤吸附甲烷可分为低压阶段主要为符合Langmuir 模型的煤基质表面吸附和高压阶段主要为符合Henry 模型的渗入煤基质的内部(孔隙、内表面)吸附。.3）开展了原煤和残煤的微观孔隙结构测定实验，分析了小分子有机物在煤中赋存形态及其对煤孔隙结构的影响。发现在中低变质程度烟煤中，煤中有机小分子物主要赋存于煤大孔和微孔中，小分子有机物的存在降低了煤中孔隙的连通性；而较高变质程度的烟煤中，小分子有机物主要赋存于微孔和煤的芳香层缺陷中，小分子有机物的存在导致煤中微孔数量减少，降低了煤的吸附能力。.4）构建了含不同量和官能团小分子有机物的煤大分子结构，数值模拟分析了含有不同官能团的小分子有机物对煤吸附甲烷作用机理。发现小分子有机物对甲烷具有较强的吸附能力，同时其在煤中赋存形态影响着煤微小孔发育，因此煤中小分子有机物含量和赋存形态决定了煤的吸附能力。