Study On The Macromolecular Structure Of Shengli Lignite By Mild Oxidation And Accelerated Solvent Extraction

Understanding of fundamental aspects of lignite macromolecular structure have strong influences onto their utilization including pyrolysis, gasification, liquefaction and combustion. Shengli lignite was chosen as the study subject, which was treated by hydrogen peroxide and accelerated solvent extraction respectively. The extractions and residual coals were studied by ultimate analysis, FTIR,13 C NMR and TG-GC/MS,and combined with the quantitative calculation simulation, the average molecular structure model of oxidation residual coal, the average molecular structure model of extraction residual coal and the average molecular structure model of oxidation extraction residual coal were established.(1)After dusting lignite treated by hydrogen peroxide, the main content of extraction were aliphatic chain carboxylic acid compounds which dominated by binary carboxylic acid of C2~C5. And the key bridge bonds in macromolecular structure of Shengli lignite were oxygen bridge bonds.The average molecular structure model of oxidation residual coal was established by means of ultimate analysis, FTIR,13 C NMR analysis and quantitative calculation. The molecular formula for the oxidation residual coal model is C96H90NO44. And results of FTIR analysis of the formula based on quantum chemistry prove to be consistent with its chromatogram.(2)Hexane, toluene, tetrahydrofuran, methanol were used successively to extract Shengli lignite, the main content of extraction were the aliphatic hydrocarbons which mainly composed of C10~C24 n-alkanes and the short-chain substituted benzene,and small amount of oxygen containing compounds consisted in the coal’s structure.The average molecular structure model of extraction residual coal was established by means of ultimate analysis, FTIR, TG-GC/MS analysis and quantitative calculation.The molecular formula for the extraction residual coal model is C159H132O52N2S2. And results of FTIR analysis of the formula based on quantum chemistry prove to be consistent with its chromatogram.(3)After extraction residual coals treated by hydrogen peroxide, the main content of extraction were Similar and dominated by binary carboxylic acid of C2~C5. The average molecular structure model of oxidation extraction residual coal was established by means of ultimate analysis, FTIR, 13 C NMR analysis and quantitative calculation.The molecular formula for the oxidation residual coal model is C72H57NO33. And results of FTIR analysis of the formula based on quantum chemistryprove to be consistent with its chromatogram.(4) The oxygenic groups consisted in the average molecular structure model of Shengli lignite were mainly composed by carbonyl, aryl ether, alkyl ether, carboxyl,phenolic hydroxyl and alcoholic hydroxyl with the highest content of aryl ether and least content of alkyl ether. The relative content of oxygenic groups were not changed significantly in the process of extraction. While the phenolic hydroxyl and alcoholic hydroxyl were easy to oxidated, the aryl ether and alkyl ether were fairly stable.(5)Structures of the small molecular compounds of shengli lignite were difficult to be oxidized. The bridge bonds of macromolecular structure between benzene ring and alkane or alcohols, benzene ring and benzene ring were facilitiy to be thermal decomposited and oxidized while the bridge bonds linked with naphthalene and heterocyclic compounds were fairly stable which difficult to be oxidized. In addition,the bridge bonds and branched chains connected with macromolecular structure of Shengli lignite were given priority to the number of carbon atoms with 2 to 5.(6)The interface of lignite with free ash was instability which easy to occur adsorb phenomenon. Re-adsorption water content of oxidation and fractional extraction residual coals were weakened and interface stability were improved. Furthermore,relative to oxidation, the interface stability of coal samples treated byorganicsolvent extraction were higher.