Structural Characteristics of Coal Vitrinite during Pyrolysis

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• 作者：Wu Li ; Yanming Zhu
• 刊名：Energy & Fuels
• 出版年：2014
• 出版时间：June 19, 2014
• 年：2014
• 卷：28
• 期：6
• 页码：3645-3654
• 全文大小：616K
• 年卷期：v.28,no.6(June 19, 2014)
• ISSN：1520-5029

文摘

Vitrinite samples inserted into a furnace at room temperature and heated at a rate of 10 掳C/h were subjected to X-ray diffraction analysis, Fourier transform infrared spectroscopy (FTIR), and solid-state ¹³C nuclear magnetic resonance spectroscopy (¹³C NMR) to characterize the macromolecular structure of vitrinite of different ranks of coal, which was discussed with respect to changes in its chemical structure. The results demonstrate that the relationship between average reflectance of the vitrinite and temperature is linear. The structural parameters of vitrinite separated from the coking coal sample collected from the Lujiatuo mine (LJTV) (d₀₀₂ = 3.56 脜, L_c = 11.62 脜, L_a = 10.99 脜) were obtained. The FTIR spectra include bands characteristic of aliphatic C鈥揌 stretching, with the ratio of aliphatic oxygen-containing compounds decreasing with increasing rank of the vitrinite samples. The C鈺怬 stretching contribution is lower than the aliphatic C鈥揌 stretching contribution, whereas the aromatic carbon contribution is high in all of the samples. The vitrinite structural parameters, e.g., the A factor, C factor, CH₂/CH₃, A_ar/A_al, Al/OX, Al/C鈺怌, and C鈺怬/C鈺怌, were calculated. The intensity of the aromatic carbon peak is considerably greater than that of the aliphatic carbon peak. The ¹³C NMR spectra reveal that the aliphatic carbon content decreases progressively with increasing thermal maturity for the replacement of aromatic hydrogens by condensation. The CCH₃ groups are removed more slowly than are the C(CH₂)C groups. The coalification progress was divided into two stages based on the CH₂/CH₃ ratio, which first decreases and later increases. As revealed by the structural parameter f_a, the aromaticity of vitrinite increases during pyrolysis.