Macromlecular Structural Model And Thermal Reactivity Study Of Dongqu No.2 Coal

Energy is an important foundation for the survival and sustainable development of human beings in modern society.As the most important mineral chemical fuel in China's industrial system,coal plays an irreplaceable role in production.Coking coal is an important part of the energy system structure in China and the world today.With the improvement of China's gross national product,science and technology,economy and many other aspects,how to make full use of China's abundant coal resources to produce clean industrial Production is a major challenge facing China's energy utilization field today,prompting researchers to deepen their research on the efficient conversion and cleaning of coal.Therefore,it puts forward higher requirements for understanding the thermal reaction mechanism of coal.This paper takes Dongqu No.2 mirror coal as the research object,and uses industrial analysis and elemental analysis,FTIR,XRD,XPS,¹³C-NMR to test the data,and through the data analysis software Origin7.5,ACD/Labs C-NMR,gNMR the construction of the macromolecular structure model of No.2 coal,molecular mechanics,molecular dynamics and quantum chemical simulation of the macromolecular structure model using material analysis software Materials Studio,using the ReaxFF reaction force field based on Monte Carlo simulation to simulate the macromolecular structure model Pyrolysis reactions at mesoscopic scale,as well as related energy changes and the formation properties of pyrolysis products.Finally,the TG/MS results of the samples were compared and analyzed.The system was studied at the simulation level and pyrolysis experiments.The main contents are as follows:1.The reflectivity of the vitrinite of Dongqu No.2 coal is measured,and the ratio of R^o_max is 1.81%.It can be seen that the coal sample is a lean coal with a high degree of metamorphism,and it mainly appears in the form of coal blending in the industry.2.The structure of Dongqu No.2 coal is characterized by FTIR.The ratio of methyl,methylene and methine in the coal structure is about 4:3:2,and the infrared aromatic carbon ratio is 0.65.XRD is used.Characterization,the aromatic layer spacing is 3.55?,the stacking height is 21.32?,and the number of stacked layers is 6.01 layers.The O and N elements are characterized by XPS to obtain inorganic oxygen,adsorbed oxygen and organic oxygen in the sample.The ratio of the form of oxygen species in the form of 1:3:4,the ratio of the content of pyrrole-type nitrogen to the content of pyridine-type nitrogen is 1:1;the nucleocarbon aromatic carbon ratio of the sample obtained by ¹³C-NMR is 0.65,The nuclear magnetic aromatic carbon ratio is consistent with the infrared aromatic carbon ratio.3.Using the structural characterization information of Dongqu No.2 coal,it is known that the ratio of aromatic bridge carbon to pericarbon is 0.35,so three hydrazines or their isomers are added to the macromolecular structure model to be constructed.It is calculated that the N atom in the hetero atom exists in one pyrrole ring and one pyridine ring,and the O atom exists in four phenolic hydroxyl groups,and one carboxyl group.The initial macromolecular structure model of the sample was constructed by ACD/Labs software and the ¹³C-NMR spectrum was simulated.After comparing the simulated spectrum with the experimental spectrum,the model was corrected and the experimental results were in good agreement.The macromolecular chemical structure model,the chemical formula of the structural model is C₁₇₄H₁₄₈O₅N₂.4.Molecular mechanics and molecular dynamics method was used to optimize the structure of a macromolecular structure model in Materials Studio software,and the minimum energy geometry was obtained.The optimization results showed that the aromatic structure showed bending deformation after optimization,and Van der Waals force the bond expansion and contraction energy can be reduced to different extents,and the corresponding bond angle energy,and bond twist energy are increased.The density simulation results obtained by adding boundary conditions show that the density of the macromolecular structure model is1.45 g/cm³ respectively.The VAMP simulation module is used to calculate the bond length,bond level and charge population in the macromolecular chemical structure model as the main structural parameters.By analyzing the parameters,it can be obtained that the C-C bond bond length in the aromatic structure is longer than that of the aliphatic hydrocarbon C-C bond.Short,the bond level is larger,so the chemical stability of the aromatic structure is higher than that of aliphatic hydrocarbons.5.The pyrolysis simulation of the macromolecular structure model under different conditions was carried out in the material chemistry simulation platform ADF software.?1?Pyrolysis simulation under isothermal conditions It can be concluded from the analysis that as the temperature increases,the trend of total molecular number,total energy,potential energy and bond energy in the simulated system gradually increases with time.The rotational energy and the van der Waals energy trend gradually decrease with time;the total number of molecules,total energy,potential energy,bond energy,rotational energy and van der Waals energy in the simulated system at different temperatures Basically consistent.?2?The pyrolysis simulation under different heating rates can be concluded by analysis.As the heating rate increases,the total number of molecules,total energy,potential energy,bond energy,rotational energy and van der Waals energy in the simulated system The degree of change is getting bigger and bigger.6.In the TG/MS pyrolysis experiment,taking the main product of pyrolysis CH₄ as an example,there are mainly three types of reactions in the pyrolysis process of coal to produce CH₄:the shorter fatty chain in coal during pyrolysis breaks,methoxy The methylation of the methyl group,the detachment of the alcohol functional group,and the secondary cracking of the long-chain aliphatic hydrocarbon to form the CH₄;the methyl group attached to the aromatic nucleus and the cycloalkane in the coal causes the methyl group to fall off due to the external high temperature;the aromatic structure in coal produces a alicyclic structure due to polycondensation,and the methyl group is detached by the action of high temperature from the outside to form CH₄.