Microwave-assisted extraction (MAE) of a low-rank Naomaohu (NMH) coal was conducted with two solvents, cyclohexanone (CYC) and tetrahydrofuran (THF), to obtain extracts (E_CYC and E_THF) and residues (R_CYC and R_THF). The parent coal, extract, and residue were characterized by ultimate analysis, TG, FTIR, GPC, ¹H NMR, and solid-state ¹³C NMR. The results showed that MAE process is more efficient than Soxhlet extraction. The solvent CYC exhibits a higher total extract yield of 8.3 wt % than THF, being 4.7 wt %, during MAE and more efficiency in extracting organic components of NMH coal, especially condensed arenes and macromolecular compounds. The average molecular weight of E_CYC is higher than that of average aromatic cluster of NMH coal. Online pyrolysis–vacuum ultraviolet photoionization mass spectrometry was taken to determine the initial pyrolysis products of parent coal, R_CYC, and E_CYC. The distribution of initial pyrolysis products suggested that NMH coal and E_CYC possess similar basic arene structures and E_CYC is rich in macromolecular clusters with lots of side chains and bridge bonds. The chemical structure of E_CYC could reflect the macromolecular network structure of NMH coal to some extent. This could be an effective method to understand the organic structure of coal.

中文翻译：

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微波辅助萃取低溶剂煤的溶剂萃取物的结构特征和热解行为

用环己酮（CYC）和四氢呋喃（THF）两种溶剂对低阶Naomaohu（NMH）煤进行微波辅助萃取（MAE），以获得萃取物（E _CYC和E _THF）和残渣（R _CYC和R _THF）。通过最终分析，TG，FTIR，GPC，¹ H NMR和固态¹³ C NMR对母体煤，提取物和残渣进行表征。结果表明，MAE法比索氏提取法更有效。溶剂CYC在MAE期间的总萃取收率比THF高，为4.7 wt％，为THF的4.7 wt％，并且在萃取NMH煤的有机组分（尤其是缩合的芳烃和大分子化合物）方面效率更高。E的平均分子量_CYC高于NMH煤的平均芳烃簇。采用在线热解-真空紫外光电离质谱法确定母体煤，R _CYC和E _CYC的初始热解产物。初始热解产物的分布表明，NMH煤和E _CYC具有相似的基本芳烃结构，E _CYC富含具有大量侧链和桥键的大分子簇。E _CYC的化学结构可以在一定程度上反映NMH煤的大分子网络结构。这可能是了解煤炭有机结构的有效方法。