胜利褐煤温和水热解聚物的液-液和微固-液萃取分离与分析

Understanding of lignite structure at the molecular level is a key scientific problem needed to be solved urgently for coal chemistry and coal conversion technology. In this project, hydrothermal depolymerization of lignite subsequent liquid-liquid and micro solid-liquid extraction is proposed to overcome the disadvantages of traditional solid-liquid extraction. lignite will be fractionally extracted with various common-used organic solvents at room temperature to obtain the extracts and extraction residues (ERs). The ERs will be hydrothermally depolymerized in alkaline water under relatively mild condition (< 240 ℃) to provide hydrothermally soluble factions (HTSFs) and hydrothermally insoluble residues (HTISRs). The HTSFs will be fractionally extracted by liquid-liquid or micro solid-liquid extraction methods at various pH values, and HTISRs will be fractionally extracted with various common-used organic solvents to obtain the extracts. All of the extracts will be finely isolated by column chromatography, recrystallization, distillation, etc. to give eluted fractions or sub-fractions. All of the extracts, eluted fractions and sub-fractions will be analyzed by gas chromatography/triple stage quadrupole mass spectrometry (GC/QqQ-MS), high-performance liquid chromatography/quadrupole time-of-fight mass spectrometry (HPLC/QTOF-MS), infrared spectroscopy and nuclear magnetic resonance to provide valuable information of the extracts and fractions at the molecular level. The results of this research should be the scientific basis for directional conversion and value-added utilization technologies of lignite. Investigation on general fragmentation rules of novel compounds in the mass spectrometer by GC/QqQ-MS and HPLC/QTOF-MS could be provided the theoretical basis for rapid analysis of the composition and structure of organic matter in lignite by mass spectrometry.

从分子水平上认识褐煤的组成结构是煤科学及煤转化技术都亟待解决的关键科学问题。针对传统褐煤固-液萃取存在的问题，本项目提出了基于褐煤水热解聚的液-液和微固-液萃取技术。具体是采用常温分级萃取技术将褐煤分离成各级萃取物和萃余煤。在相对温和（<240 ℃）的碱性条件下，将萃余煤水热解聚为水热解聚物和水解残煤。在不同pH值下，对水热解聚物进行逐级液-液或微固-液萃取，并对水解残煤进行分级萃取获得各级萃取物。利用柱层析、重结晶和蒸馏等技术对各级萃取物进行精细分离。用气相色谱/三重四级杆联用、高效液相色谱/四级杆-飞行时间质谱联用、红外光谱和核磁共振等手段分析各级萃取物和柱层析馏分，从分子水平上了解各级萃取物及馏分的组成信息。为开发褐煤的定向转化与高附加值利用技术提供科学依据。用串联质谱法研究分离获得的新化合物的质谱裂解规律，为质谱法快速分析褐煤有机质的组成结构奠定理论基础。

低阶煤的组成结构极其复杂，可溶化是从分子水平揭示其结构的重要前提。本项目采用石油醚、二硫化碳、二氯甲烷、丙酮、甲醇及混合溶剂对四种胜利褐煤进行分级萃取，丙酮和甲醇的萃取率较大，累积萃取率在0.82-2.13%之间。优化的水碱解聚温度、解聚时间、煤水比、碱用量为220 ℃，45 min，1 g/150 mL，0.1 g NaOH/g煤，胜利褐煤的水碱解聚率在15-35%之间。利用石油醚、苯和乙酸乙酯对胜利褐煤水碱解聚物进行了液-液和微固-液萃取，乙酸乙酯的萃取率最大，累积萃取率在2.93-5.94%之间，经水碱解聚后，褐煤的有机溶剂萃取率得到了明显提高。表明基于水碱解聚的液-液和微固-液萃取是传统固-液萃取的重要补充。气相色谱/质谱联用（GC/MS）结果表明，萃取物中含有烷烃、烯烃、芳烃、酯类化合物、含氮化合物等，还有6种分子量在570-598 u，含有2-4个羰基的大分子脂环酮类化合物，GC/MS无法鉴定的组分较多。利用硅胶柱层析、凝胶柱层析、重结晶等手段对胜利褐煤萃取物进行了精细分离，获得了55种族组分和13种纯度较高的化合物纯品。利用GC/MS，高效液相色谱/四级杆-飞行时间质谱联用（HPLC/Q-TOF-MS）、GC/四极杆-静电轨道阱质谱联用（GC/Q-Orbitrap-MS）、GC/大气压化学电离源/Q-TOF-MS（GC/APCI/Q-TOF-MS）、傅立叶变换红外光谱（FT-IR）和核磁共振（NMR）等手段对各馏分进行了分析，鉴定出了多种未见报道的化合物，对从分子水平了解褐煤的组成结构具有重要意义。利用GC/APCI/Q-TOF-MS和GC/Q-Orbitrap-MS等研究了10余类化合物的质谱碎裂规律，并建立了质谱分析专用谱图库，收录了化合物100余种，弥补了国际通用的NIST库的不足，为质谱法快速分析褐煤有机质的组成结构奠定了理论基础。