An Experimental Study Of Microwave-assisted Stepped Extraction Of Huating Coal

Coal as an important based source of energy, its reasonable and effective application isparticularly important. Industrial chemicals extracted from coal is one of the effective methodof comprehensive utilization of coal, and new technology which development of coalconverted to chemicals and high performance materials has become an important strategicobjectives coal chemical industry development in our country. But, the efficient utilization ofcoal and the development of clean technologies rely on the studies of coal microscopiccomposition and structure. The solvent extracting coal is one of the important methods ofinvestigating chemical structure of coal.In this paper, Huating coal, microwave assisted extraction by different single solvent andmixed solvent were systematically investigated including extraction time, ratio of solvent tocoal, microwave power and other factors in coal affecting extraction yields. Different methodshave been applied to improve the extraction rate, such as mixed solvents, adding additives insolvent and pretreatment of raw coal. Stepping extraction by methanol, acetone,tetrahydrofuran, benzene, dichloromethane, acetone/carbon disulfide, compared with asingle stage extraction. Extract of coal and residues analyzed with GC/MS, FT IR respectively,suggesting that the structure and composition of the coal.In microwave assisted extraction, the extraction yield is on the increase with time,reached the maximum in20min.The extraction yield is higher when ratio of solvent to coalabout20, and increases with the microwave power increasing, but it increases gradually flattenwhen the microwave power reached500~600W. The compound is detected in extract of singlesolvent is primarily aliphatic hydrocarbons and aromatic compounds. There are a smallamount of the hetero atom containing compounds. The substituted aromatic compounds thatdetected in aromatic hydrocarbons are short chain and long chain substituted aromatics aredifficult to dissolve. Mixed solvent extraction yield improved, the number of compoundsdetected in extract and species are increased. Extraction yield has improved to some extent when adding a small amount of zinc chloride in dichloromethane. The rate of extractionincreased from1.13%to5.19%, and58types of components in the extract, mainly is alkanemore than that no additive.The total stepping extraction rate is as high as42.2%, close to the Huating coal volatilecontent of42.97%. So, this method is a valid method to study composition and structure ofcoal that based on dose no destroying the structure of coal. Compared with the single stageextraction, former three steps extraction yield basically remain unchanged, and then tripleextraction yield increased significantly. This shows that the first three to remove large amountsof alkane, polyhydroxy small molecule, is good for benzene, dichloromethane, CS2/acetonemolecules diffusion into coal, extract better affinity of aromatic molecules with them. Steppingextraction can make the content more dissolved by solvent soluble in coal. and more types ofcompounds detected in the extract, mainly including alkane, aromatics and oxygen compounds,sulfur compounds, etc. The compounds can reflect structure and composition of coal in acertain extent, and to provide information for a better understanding of molecular structure,chemical properties and rational utilization of the Huating coal.