![]() used high-performance liquid chromatography–electrospray ionization time-of-flight mass spectrometry to separate and identify several kinds of organic nitrogen isomers in Dongming lignite, and analyzed their structural information. The solubilization of small molecules in coal by solvent extraction and its effect on pore distribution of low-rank coal were studied. used carbon disulfide and petroleum ether to extract lignite through a Soxhlet extraction (SE) for studying the extracted components of coal. used acetone as a solvent to extract lignite by microwave-assisted heating, and obtained some correlations between extraction yield and power of microwave. In recent years, scientists have made in-depth studies on the solvent extraction yield and extraction efficiency of coal. On the other hand, solvent extraction is an effective approach to study the compositions and structures of coal and to assist coal liquidation and faction. ![]() Such aromatic compounds can be used as raw and starting materials for the synthesis of aromatic polymers and engineering plastics. It has been demonstrated that coal extraction is a good method for achieving the above goals since many aromatic compounds are obtainable from the extraction process. The production of high valued chemicals from coal is a tempting method for coal utilization, which is also a fundamental direction of coal conversion technologies, highly efficient, and of rational utilization. Comprehensive utilization of coal is of critical importance for the development of the economy. Understanding the origin, chemical structure, and carbon skeleton are important for coal exploitation and further utilization. It is a challenging task to characterize the structure of coal due to the complex and heterogeneous nature. This study provides a base for the future choice of the extraction methods in terms of outcomes of the extraction products.Ĭoal is an extremely complex and heterogeneous material. The mechanisms behind these extraction processes are discussed. (3) The three extraction methods gave totally different extraction patterns for the same coal, highlighting that the extraction method can dominate the outcome of the extracted products. Moreover, a few biomarker compounds were also identified including hexaoxane, 2-methylcholest-3-ene, 6,9,12-tripropylheptadecane, and 17α-21β-28,30-bisnorhopane. A small portion of non-alkanes (1.19%) was found, which is in contrast to the other two extraction methods. ![]() (2) MAE extracted 75 organic compounds of which 53 are oxygen-containing substances. GC/MS analysis showed that: (1) The SE method extracted the least number of substances from the coal on the other hand, the extracted compounds are largely chlorinated which can be explained by the free radical mechanism. XRD diagrams showed the peak around θ = 47 was totally disappeared by all the three extractions, indicating that the graphite-like structural substances in the coal were totally destroyed in the extraction processes. The obtained IR spectra indicated that the functional groups were barely changed in strength for the coal before and after extractions concluding that the macromolecular structures of coal were not destroyed in the extraction processes. The extracted components were analyzed by GC-MS while the residues of the coal after extractions were analyzed by FT-IR spectroscopy. ![]() Soxhlet extraction (SE), ultrasonic-assisted extraction (UAE), and microwave-assisted extraction (MAE) were carried out on Daxing coal with carbon tetrachloride. ![]()
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