煤液化残渣可溶有机质中杂原子结构片段的赋存特征

Characteristics of heteroatomic structural portions in soluble organics from coal liquefaction residue

  • 摘要: 煤液化残渣(CLR)是一种典型的煤化工固废。但煤液化残渣中的可溶有机质含量高,且富含缩合芳环结构,又可视为一种宝贵的重质炭资源。基于CLR在有机溶剂中的优良溶解性,选择等体积甲醇/甲苯混合溶剂为萃取剂,采用超声-索氏协同萃取法,实现CLR可溶有机质(CLR-SO)的温和提取,并通过逐级钌离子催化氧化,结合气相色谱/质谱联用分析,揭示CLR-SO中的杂原子结构单元特征,为其清洁转化和高值化利用提供支撑。结果表明,在CLR-SO的氧化产物中,含杂原子的酸类化合物中杂原子主要是氧、氮、硫,所构成的官能团有甲氧基、羰基、醚桥键、硝基、氨基、乙腈、吲哚、吩嗪、硫羰基等。此外,还检测到含氮、硫、氟等杂原子的酯类化合物。除了含氧化合物以外,其他杂原子化合物基本从第3级氧化产物中出现。杂原子结构存在于CLR-SO的大分子骨架内部,在氧化过程中,受到周围芳环的电子云保护,优先氧化CLR-SO分子骨架外围的芳环结构。除了酸和酯类化合物,在CLR-SO氧化产物中还检测到其他含杂原子的化合物,主要分布在第3,4级氧化产物中,且在第4级氧化产物中的种类最多。此外还检测到氯、氟等杂原子,以共价键的形式存在于CLR-SO有机质的分子骨架结构中。通过逐级选择性氧化,实现了有机质分子结构的“层层剥离”,获取了更多的结构单元片段,丰富了CLR中的杂原子结构信息。

     

    Abstract: Coal liquefaction residue is a typical solid waste in coal chemical industry. However,the coal liquefaction residue is of high content of soluble organics and rich in condensed aromatic structure,thereby is considered to be the valuable heavy carbon resources. In this study,the isometric methanol/toluene mixed solvent was used to extract soluble organics from coal liquefaction residue by the ultrasonic-Soxhlet synergetic extraction at mild condition,based on the good solubility of coal liquefaction residue in organic solvents. Then the soluble organics was oxidized according to sequential ruthenium ion catalyzed oxidation,combined with gas chromatography/mass spectrometry analysis,the molecular structural characteristics of heteroatomic structure units in soluble organics were revealed,thereby to provide supporting information for its clean conversion and higher valuable utilization. Among the CLR-soluble organics(CLR-SO)from coal liquefaction residue,the heteroatom species in acid compounds containing heteroatom are mainly oxygen,nitrogen and sulfur,and the functional groups are methoxy,carbonyl,ether bridge bond,nitro,amino,acetonitrile,indole,phenazine,thiocarbonyl,etc. In addition,esters containing nitrogen,sulfur,fluorine and other heteroatoms were also detected. In addition to oxygen-containing compounds,other heteroatom compounds appear in the oxidation products 3. Heteroatom structure exists in the macromolecular framework of CLR-SO,which is protected by the electron cloud of the surrounding aromatic rings during the oxidation process,preferentially oxidizes the aromatic ring structure around the molecular framework of CLR-SO. In addition to acids and esters,other compounds containing heteroatoms were also detected in the oxidation products of CLR-SO,which were mainly distributed in the oxidation products 3 and oxidation products 4,and most of them were found in the oxidation products 4. In addition,heteroatoms such as chlorine and fluorine were detected in the molecular framework of CLR-SO in the form of covalent bonds. In summary,in this paper,through step-by-step selective oxidation,the molecular structure of organic matter is stripped layer by layer,more structural unit fragments are obtained,and the heteroatomic structure information in CLR is enriched.

     

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