煤是由有机质和少量矿物质组成的混合岩，其中有机质组成和结构直接影响着煤的高效清洁利用，研究煤的有机组成和结构特征对煤炭高值化利用具有重要意义。为了揭示不同煤阶煤中低分子化合物组成和大分子结构的差异，以长焰煤、1/3焦煤、焦煤、贫瘦煤、贫煤和无烟煤等不同变质程度煤为研究对象，采用四氢呋喃(THF)索氏萃取，借助于气相色谱-质谱(GC/MS)和核磁共振碳谱(13C-NMR)等测试手段，比较了不同变质程度煤中THF可溶有机化合物的差异，探讨了煤化过程中化学组成和结构参数的变化机制，以期为煤组成和结构研究提供参考。结果表明：① 各类煤中的THF可溶低分子化合物均以含氧杂原子化合物为主，其中低、中变质的烟煤中以长链脂肪烃和含羧基的含氧化合物为主，高变质程度煤中以环烃和含醛基的含氧化合物为主。其次为脂肪类化合物，芳烃含量较少，且随着变质程度的加深，可溶组分的化合物类型呈先增多后减少的趋势。② THF萃取作用对芳香碳数影响较小，表现为低分子化合物溶出后计算得到的芳碳率(fa′)与原煤变化趋势相同，均随着煤演化程度增大，表现出先减小后增大的变化趋势。③ 烟煤和无烟煤中可溶低分子化合物组成和大分子结构的变化呈现阶段性：煤化作用第2次跃变期间(0.5%～1.3%,Ro,max)，羧基类低分子化合物逐渐减少甚至消失，芳环结构由1～2环的苯、萘等结构转化为1～3环的苯、萘、蒽等结构，进入第3次跃变(在2.0%Ro,max左右)阶段，芳香缩合反应加剧，芳香基本结构单元增大，出现芘等4环结构的稠环，强烈的热裂解作用使得低分子化合物脱离煤体，可溶组分显著减少。研究认为，不同煤阶煤的THF溶剂萃取率及其组成的变化，是煤化作用过程中生成的可溶低分子化合物含量和种类、赋存方式，及可溶低分子化合物与溶剂、大分子结构间作用力大小的不同的结果。

Coal is a mixture of organic matter and a small amount of minerals, among which the composition and structure of organic matter directly affect the efficient and clean utilization of coal. It is important to study the organic composition and structural characteristics of coal for the high-value utilization of coal. In order to reveal the difference of the composition and macromolecule structure of low molecular compounds in different grade coals, this study takes long flame coal, 1/3 coking coal, coking coal, meager-lean coal, lean coal, and anthracite as the research objects. THF soxhlet extraction is used to test the coal with GC / MS and 13C NMR. The differences of THF soluble organic compounds in coals with different metamorphism degrees were compared, and the mechanism of chemical composition and structural parameters in coal gasification were discussed, so as to provide a reference for the study of coal composition and structure. The results show that ① THF soluble low molecular compounds in all kinds of coal are mainly oxygen-containing heteroatom compounds, in which long-chain aliphatic hydrocarbons and oxygen-containing compounds containing carboxyl group are mainly in low and medium metamorphic bituminous coal, and cyclic hydrocarbons and oxygen-containing compounds containing aldehyde group are mainly in high metamorphic coal. The content of aromatic hydrocarbon is less than that of aliphatic compounds, and the types of soluble compounds increase first and then decrease with the degree of metamorphism. ② THF extraction has little effect on the carbon number of aromatic structure, which shows that the calculated aromatic carbon ratio (fa′) after the dissolution of low molecular weight compounds has the same trend as that of raw coal, and decreases first and then increases with the increase of coal evolution degree. ③ The changes of composition and macromolecular structure of soluble low molecular weight compounds in bituminous coal and anthracite are staged. During the second jump of coalification (0.5%-1.3%，Ro,max), the low molecular weight carboxyl compounds gradually decrease and even disappear, while the structure of aromatic ring is changed from the benzene and naphthalene of 1-2 ring to the benzene, naphthalene and anthracene of 1-3 ring. In the third jump (Ro,max is about 2.0%), the aromatic condensation reaction intensifies, the basic aromatic structure unit increases, and the condensed ring of pyrene and other four ring structure appear. The strong pyrolysis makes the low molecular weight compounds separate from the coal, and the soluble components decrease significantly. It is considered that the variation of THF solvent extraction rate and composition of different grade coals is the result of the different content and type of soluble low molecular compounds generated in the process of coalification, the mode of occurrence, and the force between soluble low molecular compounds and solvent and macromolecular structure.

1 样品及实验方法

   1.1 样品

   1.2 索氏萃取实验

   1.3 核磁共振碳谱测试

   1.4 气相色谱-质谱测试

2 实验结果分析

   2.1 不同变质程度煤的萃取率

   2.2 不同变质程度煤中低分子化合物的差异性分布特征

   2.3 煤大分子结构变化特征

3 讨论

   3.1 低分子化合物溶出对煤大分子结构的影响

   3.2 煤演化过程中化学组成和结构变化

4 结论