煤生物气化过程（或称为微生物降解煤生烃过程）研究日益受到国内外学者的广泛关注，前人着眼于煤生物气化效率影响因素、生烃机制及微生物群落结构演化等方面的研究，但对煤物理、化学结构耦合关系研究鲜少。由于低阶煤生物气化效率较高，针对低阶煤生物气化过程中物理和化学结构演化特征和耦合机理这一关键科学问题，本文以黄陇侏罗纪煤田低阶煤为研究对象，挑选代表不同宏观煤岩成分的镜煤、暗煤样品和原煤样品，开展室内微生物降解煤生烃模拟实验，研究生物气化过程中不同降解时间下原煤、镜煤、暗煤的物理和化学结构演化特征及其耦合机理。研究成果对煤层气生物工程的发展有一定的理论指导意义。

查明了煤层原位微生物类型及生烃条件。实验室富集得到的黄陇侏罗纪煤田煤层本源微生物中，细菌优势菌群是拟杆菌门和厚壁菌门，古菌的优势菌群为Methanoculleus（甲烷袋状菌属）和Methanosarcina（甲烷八叠球菌属），细菌包含多种发酵产酸型微生物，古菌能够适应不同的氢分压环境，证明该群落结构具备微生物降解煤生烃的有利条件。

阐释了低阶煤生物气化过程中物理与化学结构的演化特征及规律。对比不同降解时间（第0天、21天、42天和70天）原煤、镜煤、暗煤的物理结构演化特征，发现微生物的降解作用是一个脱碳、脱氢、富氧的过程。在0 ~ 21天碳原子面网间距增加，煤晶核减小，后期稠环芳烃累积，提高了煤晶核的平行定向程度。煤中的羟基氢键、脂肪结构和芳香结构官能团被微生物降解，芳香结构的缩合程度和芳构化作用增加，其中原煤和暗煤在微生物降解的前21天芳香结构的分解最严重，镜煤在21 ~ 42天内芳香结构分解最严重。随着微生物的降解作用，煤的大分子结构模型中活性位点逐渐降低，结构变得更加稳定。微生物对孔隙结构的改造主要包括孔隙扩张、孔隙连通、孔隙增加和孔隙堵塞四种行为，降解后的煤对甲烷的吸附能力减弱，有利于甲烷的解吸运移作用。

探讨了低阶煤中原煤、镜煤、暗煤生烃性能的差异，揭示了微生物降解低阶煤生烃性能的主控因素。镜煤转化甲烷的效率最高，其次是原煤，暗煤最差。不同的官能团的降解程度是制约生烃性能的关键，煤的缩合程度影响煤的水解性能；脂肪结构CH₂/CH₃比率影响微生物对煤基质的降解速率；芳香结构的分解会影响产甲烷作用的启动时间。

探讨了低阶煤生物气化过程中物理与化学结构参数的耦合关系，揭示了低阶煤孔隙结构与有机大分子结构的演化机理。煤的孔隙结构演化主要与芳香层片交联的化学键和小分子芳香结构有关。微生物优先降解芳香层片之间交联的化学键，导致小分子芳烃脱离煤体，造成孔隙堵塞。后期降解小分子芳香结构，残余大分子量的稠环芳烃累积，使残煤结构稳定、致密，孔隙之间的连通性增强。

In recent years, researchers both domestically and internationally have shown increased interest in coal bio-gasification processes, also known as microbial degradation process in coal hydrocarbon generation. While most studies have focused on factors that influence the efficiency of coal bio-gasification, as well as hydrocarbon generation mechanisms and microbial community structure evolution, there remains a gap in our understanding of coupling mechanism coal’s physical-chemical structure that occur during the coal bio-gasification process. On account of the bio-gasification efficiency of low-rank coal is generally higher than that of middle to high-rank coal. Addressing the crucial scientific challenge of exploring the physical and chemical structural evolution characteristics and coupling mechanisms during the bio-gasification process of low-rank coal, the study microbial degradation simulation experiments were conducted as raw coal, vitrain and durain sourced from the Jurassic Huanglong coalfield. This study aims to investigate the scientific issues regarding the physical and chemical structural evolution characteristics and coupling mechanisms involved in the process of bio-gasification of low-rank coal. The results of this study offer valuable theoretical guidance for the advancement of coalbed methane bioengineering.

The types and conditions of situ-microorganisms in coalbed were ascertained. Among the situ-microorganisms of the Huanglong coal mine, the dominant bacterial groups of phyla were Bacteroidetes and Firmicutes, and the dominant archaea groups of genera were Methanoculleus and Methanosarcina. Bacteria consist of multiple types of microorganisms capable of producing acids during fermentation, while archaea are able to thrive in various hydrogen partial pressure environments. The presence of favorable conditions for the biodegradation of hydrocarbons in coal is supported by the characteristics of the microbial community structure.

This study provides insights into the evolution characteristics and rules of physical and chemical structures during the bio-gasification process of low-rank coal. Comparing the physical structure evolution characteristics of raw coal, semi-anthracite, and anthracite at different degradation stages (0 days, 21 days, 42 days, and 70 days). Results showed that microbial degradation is a decarbonization, dehydrogenation, and oxygen enrichment process. Chemical bonds within coal were disrupted, causing the interlayer spacing of carbon atoms to widen during the first 0-21 days, and resulting in a reduction of coal crystal nuclei size. The accumulation of condensed aromatic hydrocarbons in the later stage increases the level of parallel orientation of the coal crystal nuclei. Microbial degradation breaks down the hydroxyl hydrogen bonds, lipid structures, and aromatic structure functional groups in coal, leading to an increased degree of aromatic structure condensation and aromatization. Specifically, the breakdown of aromatic structures was most severe within 21 days for raw coal and durain, whilst for vitrain, it peaked between 21 to 42 days. As microbial degradation progressed, the number of active sites within the macromolecular structure of coal gradually decreased, leading to greater structural stability. The modification of pore structures by microorganisms involves four distinct mechanisms: pore expansion, pore connection, pore increase, and pore blocking. Following bio-degradation, the adsorption capacity of methane on coal is reduced.

The differences in hydrocarbon generation performance among different microscopic components of low-rank coal were compared, revealing the main controlling factors for the hydrocarbon generation property of bio-gasification of low-rank coal. The vitrain had the highest efficiency in converting biomethane, followed by raw coal and durain. The degree of degradation of different functional groups plays a crucial role in determining hydrocarbon production. The level of coal condensation has an impact on its hydrolytic performance, while the CH₂/CH₃ ratio of the lipid structure can influence the rate at which microorganisms degrade coal substrates. Additionally, the breakdown of aromatic structures may also affect the start time of methane production.

This study examines the coupling relationship between physical and chemical structural parameters during the bio-gasification process of low-rank coal, shedding light on the evolution mechanisms of pore structures and organic macromolecular structures. Specifically, the evolution of coal pore structure is primarily dependent on the chemical bonds formed through the cross-linking of aromatic layers and small molecule aromatic structures. Microorganisms break down the chemical bonds between cross-linked aromatic layers, causing small molecule aromatic hydrocarbons to separate from the coal body and potentially leading to pore blockage. Additionally, microbial decomposition of small molecule aromatic structures results in the accumulation of residual high-molecular-weight polycyclic aromatic hydrocarbons, which leads to stable, dense coal structures and enhanced pore connectivity.