不同变质程度煤的碳结构特征及其演化机制

应用X射线衍射(XRD)与核磁共振碳谱测试(13C-NMR)相结合的方法，对5个不同变质程度煤(WMC长焰煤、LL3焦煤、LL4焦煤、CZ无烟煤与SH无烟煤)的碳结构特征及其演化进行了研究。结果表明：(1)变质程度是影响煤中碳结构演化的最重要因素。随着煤变质程度的增加，煤中芳碳率增大，芳香核缩聚程度增加，芳香结构单元排列趋于有序。(2)变质环境对煤的碳结构演化具有重要影响。高温低压环境下，WMC煤中芳香结构单元发生超前演化，形成一系列堆垛高度大延展度小的芳香结构体系；脂肪类物质中，一方面脂肪侧链发生快速热解，形成较多的环甲基，另一方面煤中已有的脂肪环发生热解断裂，形成新的脂肪链，导致支链化程度增加。(3)中等变质程度的LL4与LL3煤中发生了显著的脂环化作用，导致其季碳含量明显增高，支链化程度降低。(4)随着变质程度增加，CZ与SH煤样中，脂肪环发生断裂，形成新的脂肪链致使支链化程度增加，成为高变质程度煤中形成更大芳香体系的前奏。

Carbon structure characteristics and evolution mechanism of different rank coals

Based on the X-ray diffraction (XRD) and 13C nuclear magnetic resonance spectrum (13C-NMR)，the carbon structure characteristics and the evolution mechanism of five different ranks of coals（WMC long flame coal，LL3 coking coal，LL4 coking coal，CZ anthracite and SH anthracite) have been studied.The results indicate that：The coal metamorphic degree is the most important influencing factors for coal structure.With the increase of coal rank，the aliphatic carbon content decreases while the aromatic carbon content increases.Furthermore with the increase of coal rank，the condensation degree of aromatic nuclei increases while the arrangement of aromatic structure units tends to be ordered.The metamorphic environment can bring important influence to the evolution of coal carbon structure.At a high temperature and low pressure con-dition，the aromatic structural units of WMC have evolved in advance，which forms a series of aromatic structural systems with high vertical stacking degree and small horizontal extension degree.For the fatty substances of WMC coal，the aliphatic chains form many ring methyl groups on aromatic rings by the fast pyrolysis while the aliphatic rings break down and form the new fatty chains which leads to the huge branching degree of WMC.In the middle maturate coals there may be the aliphatic cyclization effect which leads to the decrease of the degree of branching and the increase of the content of quaternary carbons.As the increase of coal rank，the aliphatic rings will break down and form the new fatty chains which contributes to the huge degree of branching and might lay the foundation for the formation of bigger aromatic system in high rank coals.