Study On Mechanism Of Microwave-assisted Extraction Of Coal And Analysis Of Its Chemical Component And Structure

The composition,structure and reactivity of coal have been a very important issue in coal science, complete understanding of coal composition and associated force between molecule can be accomplished by experiments of the solvent extracting coal and study on extraction mechanism and extraction kinetics in thesis. The difference in composition and structure between different coals is because of the diverse plants and exterior conditions during forming coals. The thesis takes five coals such as Shenfu coal,Huating coal,Tongchuan coal,Yitai coal and Panzhihua coal with different rank as its research objective and Shenfu coal is the primary objective to reveal the extract component, residual structure using different solvents under microwave-assisted extraction. Extracts and residues are analyzed with GC/MS and elemental analysis,FT-IR analysis, ¹³C-NMR analysis respectively. Relative structure parameters,for example, f_a, f_a^c, f_al are calculated by curve-fitting method.Different extraction methods lead to differ extraction yields and extract components. Comparison of microwave-assisted extraction and Soxhlet extraction,there was a higher extraction yield of microwave-assisted extraction than that of Soxhlet extraction and there were more organic compounds in extracts of microwave-assisted extraction than that of Soxhlet extraction during shorter time. FT-IR and ¹³C-NMR analyses are employed to quantitatively calculate hydroxy functional group and f_al^o, f_al^H of Shenfu coal and its residues. Fick diffusion law using least square method calculates microwave-assisted extraction kinetics equation and the process of microwave-assisted extraction is divided into two stages in which aliphatic and aromatic compounds are dissolved mostly and compounds containing heteroatoms are dissolved mostly respectively.Furthermore,the experimental results reveal that different extraction temperature,extraction time, solvents and minerals in coals affecting extraction yields and extract components. Higher and lower temperature are not in favor of extraction compounds containing heteroatoms;Extraction yields increase when the extraction time is extended,which leads to decrease of aliphatic and aromatic compounds in extract.Results of study on coals with similar rank reveal that extraction yields and extract component contents are different under the same extraction conditions. The percent content of preasphaltene fraction of extracts in higher rank Panzhihua coal is higher than that of in Yitai,Tongchuan,Huating and Shenfu coals under the same conditions.Microwave-assisted extraction of Shenfu coal experimental results show that Shenfu coal is dissolved well by composite sovents and fractionation extraction experiment and extract components are also changed. Experimental research shows that surfactants are benefit to improve the single solvent extraction yields and influence extract components; A few Lewis acid such as Ferric chloride and Zinc chloride are also benefit to largely increase the extraction yields of methanol and alcohol. Although species of alkanes and arenes in extracts of containing additives are less than that of in single solvent, which leads to the relative concentration of extracts.Shenfu coal macromolecular fragment model is assembled using a self-adaptive genetic algorithm by self-build molecular fragement base from the different functional groups and relative structural parameters such as f_a , f_al. A large and complicated coal structural model is constructed. Simulated value of relative parameters are quite close to test value, which supplies worth information on understanding structure, character and conversion from the point of view of molecule structure.