Construction Of Structural Model And Liquefaction Performance Of Low-rank Coal

China is a big coal resource country,coal is one of the main energy sources at present.While coal is used on a large scale,it will also cause the unclean use of coal.At this time,coal liquefaction technology was born.Direct coal liquefaction is a clean technology that converts coal into liquid fuel through hydrogenation.At the molecular level,it is of great significance to explore the composition of coal structure and its liquefaction reaction performance for the development of direct coal liquefaction technology,so as to achieve a green and sustainable development mode.The coal sample in this paper is selected from low-rank coal,the characterization of a series of analysis of coal samples,get the required functional information and structure parameters,such as,in turn,construct the macromolecular structure of coal sample model,after the quantum chemical calculation and autoclave liquefaction experiments,reaction temperature and reaction time on the properties of liquefied effect,in the end,The saturated hydrocarbon and aromatic hydrocarbon components in oil were studied.The experimental results are as follows:（1）Elemental analysis shows the content of carbon,hydrogen,oxygen,nitrogen and sulfur in coal samples,among which C and O are the highest,which are 74.25%and 19.37%,respectively.The atomic ratio of H/C is 0.8084.Lithofacies analysis showed that the contents of vitrinite,inertinite and chitin were 87.0%,2.6%and 2.4%,respectively.The reflectance is about 0.48.（2）The peak fitting spectra of ¹³C-CP/MAS NMR showed that there were many aromatic carbon structures in coal samples.In addition,the ratio X_bof bridge carbon to peripheral carbon of aromatic structure was 0.061.The peak fitting of FTIR spectra showed that the structure of coal was mainly aromatic ring macromolecular structure,and mainly consisted of three and four substitutions.The morphology of carbon, nitrogen and oxygen elements was analyzed by peak fitting by X-ray photoelectron spectroscopy.The results showed that aromatic carbon,carbon-oxygen organic functional groups,pyrrole type nitrogen and pyridine type nitrogen were dominant in coal samples.The XRD pattern shows that the aromatic structure unit is composed of7-8 layers of aromatic layer net.The above structural parameters provide the basis for the construction of coal macromolecular structure model.（3）By calculating the ratio X_bof bridge carbon and pericarbon in aromatic structure,the optimal solution is deduced,and the number of pyrene,phenylene,naphthalene,benzene,pyridine and pyrrole in the macromolecular structure of low rank coal is 0,0,4,6,1,1,respectively.Then using ACD/CNMR software,the structure model of the coal sample was constructed.After hundreds of adjustments and proofreading,the molecular formula of the coal sample was C₁₆₇H₁₈₈N₂O₃₃,and the molecular weight was 2751.273.（4）Quantum chemical calculations show that the bond order of the structural model is C=O bond>Bonds in aromatic ring>C-O key>-CH₃keys>The bond in the fat ring and the-CH₂-bond near the C=O bond.C-C key.The analysis of the bond length data shows that the bond length order of the structural model is:C=O bond<C-O keys<The aromatic ring key<The bond of the fat ring.（5）In the experiment of autoclave liquefaction,different reaction temperatures and reaction times showed that the coal conversion rate and oil yield were positively correlated with the temperature and time,and the optimal reaction temperature and time were 455℃and 60min.The aromatic hydrocarbons in liquefied oil are mostly biscyclic aromatic hydrocarbons,and the biscyclic aromatic hydrocarbons are mostly tetrahydronaphthalene and naphthalene and their derivatives.