Basic Research On The Characteristics Of Molecular Compositions And Structures In Organic Matters Of Ningdong Coal And Their Direction Conversion

Ningdong coalfield is an ideal raw material industrial base for Ningxia coal chemical industry for the rich low-rank coal reserves.Comprehending the molecular composition and structural characteristics of Ningdong coal as well as the mechanism of directional transformation is of great significance for realizing the high value-added utilization of Ningdong coal and transforming the advantages of Ningxia coal resources into strong economic advantages.In this paper,the coal samples of Hongliu Mine?HL?,Yangchangwan Mine?YCW?and Meihuajing Mine?MHJ?in Ningdong Coalfield were selected as the research objects.First,petroleum ether,carbon disulfide?CS₂?,methanol,acetone and acetone/CS₂ mixed solvents of equal volume were used to extract three kinds of coal samples separately,and extracts at each stage and residual coal were obtained.Then,cyclohexane,benzene and methanol were selected as the thermal solvents with anthracene as the active hydrogen acceptor,to dissolve and polymerize the extracted coal of three kinds of coal samples respectively,and thermal solutes of all levels and thermal residues were obtained.Finally,magnetic supported solid superbase catalysts were prepared,and the thermal residue was catalyzed by hydrocracking.The extracts,thermosolutes and catalytic cracking products of three coal samples were analyzed by gas chromatography/mass spectrometry?GC/MS?.The experimental results showed that the method of ultrasonic assisted fractional extraction can effectively separate the more easily dissolved organic molecules from Ningdong coal.Extracts by petroleum ether are mainly alkyl-substituted cyclohexane.Extracts by CS₂ are mainly macromolecular aromatic hydrocarbons and aromatic derivatives.Extracts by methanol are mainly normal alkanes and alkyl-substituted benzene.Extracts by acetone are mainly heteroatomic organic compounds with oxygen-containing organic substances.Extracts by acetone/CS₂ after several stages of extraction can detect fewer components,and mainly macromolecules.Methanol has the highest extraction rate for each coal sample,while petroleum ether has the lowest extraction rate for each coal sample,which indicates that the extraction rate is not only related to the coal sample body,but also to the polarity and solubility of solvent.In terms of product composition,there are many kinds of detectable components in the fractional extracts of three kinds of coal samples.Among them,the contents of naphthenes,substituted aromatic hydrocarbons and heteroatomic organic compounds are relatively high.A small number of high value-added products such as squalene,gibberelline and phytane are also detected,which are of great significance for the efficient development and utilization of Ningdong coal.Compared with cyclohexane and benzene,methanol has the best effect on the dissolution of macromolecular organic compounds in coal structure.The content of aromatics is higher and olefins is the lowest in the pyrolysis products at 300?.Most of the aromatics are substituted by methyl,ethyl,isopropyl and long chain alkyl groups.It is presumed that they are mainly free in the macromolecular network structure of coal.A large number of phenolic compounds were also detected,mainly alkyl substituted phenols.Compared with the results of fractional extraction,the content of alkanes in the thermal solution is higher,which indicates that the intermolecular force of alkanes in coal structure is stronger,especially the branched alkanes have strong coiling effect in the complex structure network of coal,and extraction under mild conditions can not dissolve them in large quantities.The prepared magnetic supported fixed super-strong base catalyst has good superparamagnetism,well-distributed mesoporous structure and strong alkaline sites.Compared with stepwise extraction and thermolysis at variable temperature,the yield of solute in the product of catalytic hydrogenation of coal residue is obviously increased,which indicates that solid super alkali can effectively promote the breaking of covalent bonds between organic matter molecules in coal structure.The content of aromatics,phenols and ketones in catalytic cracking products is higher,especially phenolic compounds.It shows that solid super alkali catalyst can promote the fracture of-C-O-bond connecting phenoxy group and macromolecular network skeleton structure in coal structure.