构造应力作用下煤结构演化与甲烷富集的分子模拟

The mechanism of methane enrichment and the occurrence of coal under strong tectonic stress is a scientific problem that has plagued the coal geologists and coal mine safety engineers. In the past, the study on the evolution process of coal molecular structure and the molecular mechanism of the interaction between methane and coal are very weak.. Based on the analysis of the geological conditions for the formation of the strong deformed coal, we collect the primary structure coal and the different stages of tectonic coal in the typical area, and find out the difference of the physical properties of the primary structure coal and the different stages of the tectonic coal. The vitrinite and inertinite of coal are obtained by separation and purification of macerals, and their coal microcrystalline structure and coal macromolecular structure parameters are tested by instrumental analysis method. The small molecular substances in coal are determinated by solvent extraction combined with GC-MS and color red combination. The molecular structures of deformed coal and undeformed coal are built and optimized by molecular simulation software and experimental analysis of coal pyrolysis.The evolution of the macromolecular structure and the microscopic mechanism of the coal from the deformed to the different degrees undeformed coal at the atomic and molecular levels by using quantum chemistry software. On this basis, the characteristics of methane molecular aggregates and methane in coal molecular structure preferred adsorption site and binding energy are determinated. The microscopic mechanism of the interaction between methane and coal structure, and the possible phase states of methane in coal structrue are identified at atomic level.. The project will break the molecular mechanism of methane concentration and enrich the theory of coalbed methane geology, which can provide scientific basis for the prevention and control of gas disaster and the exploration and development of coalbed methane resources.

强构造应力作用下煤中甲烷富集机理和赋存状态是一直困扰着煤地质学家和煤矿安全工程师的科学问题。以往对构造应力作用下煤结构演化过程及其与甲烷生成富集及相互作用的分子机理研究较为薄弱。项目在分析强构造变形煤形成地质条件的基础上，采集典型地区的原生结构煤及不同阶段构造煤，分离和纯化煤岩组分，测试煤岩镜质组分的微晶结构、大分子结构参数和小分子物质。结合原生结构煤和构造煤的热裂解实验，采用分子模拟软件构建和优化煤分子的三维空间结构。利用量子化学方法从原子和分子层次上揭示原生结构煤到不同阶段构造煤的分子结构演化历程及其产生甲烷的微观机理，在此基础上，确定甲烷分子聚集体的特征，分析甲烷在煤分子结构中优先吸附点和结合能，查明甲烷与煤分子结构相互作用微观机理及甲烷可能存在的相态。项目研究将破解甲烷富集的分子机理，为高应力和低渗透性煤层气资源勘探与开发及矿井瓦斯灾害防治提供科学依据。

构造应力变形区是煤矿瓦斯突出防治和煤层气开发研究的难点和关键，分子模拟方法是揭示构造应力作用下煤与甲烷相互微观机理的有效手段。项目采集不同的构造煤样，通过元素分析、固体核磁(NMR)和高分辨率透射电子显微镜(HRTEM)等手段确定了煤大分子结构；采用超声微波逐级抽提方法确定了煤中低分子物质，进而运用分子模拟技术构建和优化煤分子的三维空间结构，真实地反映了煤分子结构特征。在此基础上，采用量子化学和分子动力学方法查明煤分子结构演变历程及裂解生成甲烷的过程，揭示构造应力作用下煤结构裂解生成甲烷的分子机理。弱变形作用使煤分子的脂肪结构断裂和脱落；强变形作用可导致煤中芳核数量增加，脂族基团和醚氧键减少，从而生成大量的小分子气体。煤中小分子裂解先发生C-C键断裂，生成苯基和甲基，苯基进而与甲基上的H离子结合，生成苯环和亚甲基。采用巨正则蒙特卡洛（GCMC）分子模拟探索了甲烷在构造煤中的吸附位点及富集机制，发现煤结构的晶胞边缘会优先吸附甲烷分子，随后甲烷分子才慢慢进入结构内部，并且主要吸附在煤大分子的支链附近。甲烷在微孔中的吸附呈微孔填充机制。项目揭示煤结构与甲烷分子及其多聚体相互作用的微观机理，破解了构造应力作用下甲烷富集的分子机理，丰富了煤层气地质理论，为高应力、低渗透性煤层气资源勘探与开发及矿井瓦斯灾害防治提供科学依据。.项目执行期间，发表了高水平学术论文18篇，其中SCI收录12篇，EI收录2篇，ESI高被引论文2篇。项目负责人担任了匹兹堡煤科学国际会议分会主席2次（2019年，2020年）；申请国家发明专利4项，已授权2项；申请实用新型专利3项，已授权2项；获得国家新疆维吾尔自治区科学技术三等奖1项；培养了博士研究生2名，硕士研究生4名；授权发明专利与相关企业合作进行中试放大。