陕北侏罗纪富镜煤和富惰煤分子结构的FTIR，XPS和13C NMR表征

侏罗纪优质煤炭资源为煤制油、制气等清洁高效利用提供了丰富的物质基础，其显微组分以富集惰质组为特征，而镜质组与惰质组大分子结构在很大程度上决定了煤的物理化学性质和工艺性能，进而决定了煤炭资源的综合利用效率及附加值。采集并制备了陕北侏罗纪煤田小保当煤矿和柠条塔煤矿的原煤(XR)、富镜质组煤(XV、NV)和富惰质组煤(XI、NI)样品，利用傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)、固体13C核磁共振谱(13C NMR)等手段，结合煤质分析结果，定量表征了不同显微组分富集物分子结构的差异。研究结果表明：XI和NI煤中芳烃结构芳环取代程度低，主要以3个相邻、4~5个相邻的氢原子形式存在，苯环上氢原子较少被其他官能团取代，同时其结构中芳烃C═C骨架振动明显，脂肪结构中亚甲基伸缩振动强度较低，并且甲基含量略高于富镜煤，C═O基团相对含量略高，表明富惰煤有较多含氧桥键相连的芳香结构，其结构中脂族链、脂环基团脱落、断裂以及芳烃富集，支链相对较少且长度较短，芳碳率、芳香度、芳环缩合程度及成熟度较高。XV和NV煤中表面结构中碳的赋存形态“C—C，C—H”，“C—O”的相对含量高于富惰煤，反映其结构中应含较多的芳环取代的脂肪族侧链，XI和NI煤表面结构中氧的赋存形态以“C—O”为主，“C═O”和“COO—”明显高于富镜煤。XV和XI煤的芳碳率分别为57.91%和66.02%，脂甲基碳分别为10.02%和7.84%，质子化芳碳为非质子化芳碳的两倍，XV煤的羰基和羧基碳相对含量较高，两者桥碳和周碳之比分别为0.25和0.40，芳香核结构平均缩合环数分别为2.68和3.03，平均尺寸分别为0.448和0.676 nm，XI煤结构中芳香核以萘和蒽为主，支链化度L_γ分别为0.22和0.19，表明XV比XI存在较多脂肪侧链、饱和环结构，生烃(油)潜力大。

Molecular Representations of Jurassic-Aged Vitrinite-Rich and Inertinite-Rich Coals in Northern Shannxi Province by FTIR,XPS and 13C NMR

Jurassic high-quality coal resources provide the abundant material basis for clean and efficient coal utilization to oil and gas. Microlithotype composition of Jurassic high-quality coal resources is characterized by enrichment of inertinite. The macromolecular structure of vitrinite and inertinite largely determines coal’s physical and chemical properties and process performance, and then determines comprehensive utilization efficiency and added value of coal resources. Thus, raw coal (XR), vitrinite-rich coal (XV, NV) and inertinite-rich coal (XI, NI) samples were collected and prepared from Xiaobaodang and Ningtiaota coal mining area in the Jurassic coalfield of northern Shaanxi Province. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and solid nuclear magnetic resonance spectroscopy (13C NMR) were used to quantitatively characterize the differences in molecular structures of different maceral enrichments combined with the results of coal quality analysis. The results showed that the aromatic ring substitution degree of aromatic structure in XI and NI coals is low, mainly in the form of three adjacent hydrogen atoms and four to five adjacent hydrogen atoms. Other functional groups less replace hydrogen atoms on benzene ring. At the same time, the vibration of aromaticC═C skeleton in the structure is obvious, and stretching vibration intensity of methylene in aliphatic structure is reduced. Methyl content is slightly higher than that of vitrinite-rich coals, and the relative content of theC═O group is slightly higher, indicating that inertinite-rich coal has more aromatic structures connected by oxygen-containing bridge bonds. Aliphatic chain and aliphatic ring groups fall off, fracture and aromatic enrichment, and branched-chain is relatively small, and the length is short. In addition aromatic carbon rate, aromaticity, aromatic condensation degree and maturity are high. The relative content of “C—C, C—H” and “C—O” in the surface structure of XV and NV coals is higher than that of inertinite-rich coals, which reflects that the structure should contain more aliphatic side chains replaced by aromatic rings. The oxygen species in the surface structure of XI and NI coals are mainly “C—O”, and “C═O” and “COO—” are significantly higher than those of vitrinite-rich coals. The aromatic carbon ratios of XV and XI coals are 57.91 % and 66.02 %, respectively. XV and XI coals’ aliphatic methyl carbon ratios are 10.02 % and 7.84 %, respectively. The protonated aromatic carbon is twice as much as the non-protonated aromatic carbon. The relative content of carbonyl and carboxyl carbon of XV coal is high. The ratios of bridge carbon and per carbon of XV and XI coals are 0.25 and 0.40, respectively. The average number of condensation rings of aromatic nucleus structure is 2.68 and 3.03, and the average sizes are 0.448 nm and 0.676 nm, respectively. The aromatic nucleus in the XI coal structure is mainly naphthalene and anthracene, and the branched-chain degrees are 0.22 and 0.19, respectively. It is indicated that XV has more aliphatic side chains and saturated ring structures than XI coal and has great hydrocarbon generation potential.