Analysis Of Easy Separation/Pyrolysis Components In Lignite And Construction Of Lignite Macromolecular Structure Model

Knowing the macromolecular structure of lignite is the basis for understanding the physical and chemical properties of coal.It is of great significance for increase efficiency utilization of lignite pyrolysis,gasification,liquefaction and combustion.Due to the complexity of lignite structure,constructing lignite macromolecular structure model is challenging.The lignite is coated with minerals,small molecular compounds and clusters,which are interwoven with the skeleton structure of insoluble macromolecules by non-covalent bonding forces such as hydrogen bond and van der Waals force to form a complex network-like three-dimensional structure.When the macromolecular framework of lignite is studied by analyzing and characterizing lignite samples,the characterization analysis results will be interfered by the test signals of minerals,small molecular compounds and molecular clusters,which will have a certain impact on the research of lignite macromolecular structure.In order to understand the macromolecular skeleton structure more clearly and accurately,it is necessary to separate minerals,small molecules and clusters from macromolecular structures.In this paper,typical young zhaotong lignite and old shengli lignite are selected as research objects to go into the distribution and kinetics of lignite pyrolysis products,and molecular weight distribution,morphology and structure composition of lignite fractionation extracts.On this basis,the average theoretical structure models of lignite were constructed by quantum chemical theory calculation method.The results show as follows:1.Some of the minerals exist between the aromatic layers of the lignite skeleton structure,which can be removed by acid washing process.A small amount minerals exist in the structure of lignite in the form of metal bridge bond,and some in the form of carboxylate.After acid washing process,the content of carboxyl group increases.Some of them exist in the lignite structure in the form of package,and the original pore structure of lignite is collapsed after removal.2.In the process of pyrolysis,the kinds of small-molecule gases and other volatile components in various samples released are the same.450-500 ^oC is the most concentrated temperature for the release of CH₄?CO?CO₂?C₂H₄?SO₂?NO and other small molecules,and the most important component is CO₂.The initial release temperature of CO₂ is about 200 ^oC,which is mainly from the cleavage of carboxyl group and carbonyl group.The initial release temperature of CO is about 300 ^oC,which is mainly from functional groups such as ketone and aldehyde.The initial release temperature of CH₄ is about 400^oC,which is mainly from aliphatic substance and methoxy.3.The molecular weight of small molecular compounds and organic molecular clusters in ZTL ranges from 300 to 20,000,the molecular weight of organic molecular clusters in SL ranges from 10 to 1,000.The small molecular compounds and organic molecular clusters are encapsulated in the three-dimensional network structure of lignite,and its functional group species are basically consistent with the skeleton structure.4.TG-FTIR-GC-MS was used to study the structural fragments of lignite obtained at different injection temperatures.Through comparative analysis,combining with13C-NMR,it is concluded that the skeleton structure of lignite is mainly composed of two benzene condensation aromatic rings with 3-4 substituents.The skeleton structure of lignite is mainly composed of two condensed aromatic rings of benzene,which substituents number is 3-4.The heteroatoms in lignite are mainly present in the form of pyridine,thiophene,furan,hydrazine and hydrazine.The oxygen-containing functional groups exist mainly in the form of carboxyl group,hydroxyl group,ether and phenolic carbonyl group.5.The pyrolysis reactions of various samples are consistent with the first-order kinetic model.And the activation energy of the pyrolysis reaction is lower,and the pyrolysis reaction is easier to carry out.Compared with SL lignite the pyrolysis reaction of Zhaotong lignite is easier to carry out.The lignite structure is affected by acid washing process,so the activation energy of the corresponding stage is reduced.The activation energy after raffinate is higher than before,and the reaction is more difficult to carry out.6.Based on the carbon skeleton structure obtained by ¹³C-NMR nuclear magnetic resonance,the molecular structure fragments obtained by TG-FTIR-GC-MS and the information obtained by other characterization methods,combined with the calculation of quantum chemical theory,the 3D macromolecular skeleton model of ZTLC,ZTLCR,SLC,SLCR were constructed.The molecular formulas of the model are as follows:C₁₃₁H₁₁₉N₃O₆₄S,C₁₆₅H₁₄₇N₃O₄₁S,C₁₅₉H₁₂₅N₃SO₅₃,C₁₇₅H₁₅₃N₃SO₃₅.The models have low energy,stable structure.They can reflect the structural characteristics of lignite itself.The calculated infrared spectrum of the model agrees well with the characteristic peak of the experimental infrared spectrum.The paper contains 109 images,45 tables,and reference 231.