Macromolecular Structure And Generation Dynamics Of Hydrogen And Methane During Pyrolysis For Tunlan No.8Coal

Coal is one of the fossil fuels that can’t be completely replaced in the futurefor a long time. There is, therefore, the need for sustainable development inChina to control and lighten the harmful effects of coal processing. Efficient andclean utilization is the important way to meet this need. The coal pyrolysisbecomes the hot research hotspot of coal conversion and utilization.The composition and structure is closely related to the pyrolysis of coal,exploring the molecular structure, pyrolysis process, and the generativemechanisms of hydrogen and methane, the molecular structure of coal can becharacterized by physicochemical methods, to provide the theoretical basis forthe coal pyrolysis and gas product generation kinetics. The Tunlan No.8coalfrom Taiyuan Xishan is used as the sample in the study. Through analyzing theFTIR spectra, the paper characterizes the main form of oxygen in ether, phenol,carbonyl, and the aliphatic chain in methylene, methine. By extraction ofHRTEM images of aromatic layer structure, it shows that the aromatic groups inmolecular structure of the coal are less than4*4. The analysis of XPS spectracharacterizes that sulfur mainly forms in alkyl and thiophene, nitrogen in pyrrole and pyridine, and oxygen in C=O and C-O. The analytical13C-NMRspectroscopy reveals that the carbon skeleton of coal molecular structure ismainly composed of aliphatic carbon zone, aromatic carbon and carbonyl region.Based on the above experimental results, the coal sample molecular structuremodel is constructed withACD/ChemSket software.Then the most stable configuration can be achieved through molecularmechanics, molecular dynamics, and minimum energy of the coal structuremodel using Materials Studio software. After that, it analyzes the vibrationfrequency of the structure model by the method of semi empirical algorithms inquantum chemistry calculation, which further verifys that the structure modelconstructed in this paper can represent the real molecular structure of the sample.The quantum mechanical calculation of bond length, bond order and chargedistribution in the structure model is also carried out.Application of thermogravimetry-mass spectrometry (TG-MS) couplingtechnology in10,20,40℃min-1three heating rate on the influence of coalpyrolysis behavior is analyzed. By using distributed activation energy model(DAEM), and analysis of pyrolysis, hydrogen and methane dynamics, pyrolysisreaction process, hydrogen and methane activation energy distribution functionis obtained. The results suggest that the activation energy of the pyrolysisprocess shows the characteristics of the stage concentration distribution, and hasa certain symmetry. According to the relationship between the conversion rate,temperature, and activation energy, and the thermal weight loss, the pyrolysis process is divided into five stages, and the chemical reactions of each stage arediscussed. It also suggests that the overall trend of the activation energy of thepyrolysis hydrogen and methane increases as the conversion rate goes up, andexhibits characteristics of the distribution at a certain stage. According to thekinetic characteristics of hydrogen and methane generation, the formationprocess is divided into five and three stages, which reveals the differentmechanisms of chemical reactions.