Abstract The evolution of active groups at low temperature was examined using Chinese lignite by infrared technology and X-ray photoelectron spectroscopy (XPS). The results showed that the hydroxyl, aliphatic ether, methylene, and methyl groups played important roles in the low-temperature oxidation of lignite below 200 °C. Carbonyl and carboxyl groups were important intermediates. Thus, a multi-step evolution mechanism involving the hydroxyl, aliphatic ether groups, and alkane was reasoned to describe the low-temperature oxidation of lignite. In addition, according to the oxidation kinetics experiment and the evolution laws of the active groups, the ratios of the reaction lines were determined considering the accuracy of thermal effects. The thermal effects and the heat release intensities of each temperature interval were obtained based on the evolution mechanism and the reaction ratios. The shortest spontaneous combustion period of lignite was calculated and compared with the experimental value, which proved that the reasoned evolution mechanism of the active groups and the calculations of the thermal effects were reliable.

中文翻译：

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褐煤低温氧化活性基团演化机制及热效应

摘要 利用红外技术和X射线光电子能谱(XPS)研究了褐煤在低温下活性基团的演化。结果表明，羟基、脂肪醚、亚甲基和甲基在褐煤200℃以下的低温氧化过程中起重要作用。羰基和羧基是重要的中间体。因此，涉及羟基、脂肪族醚基团和烷烃的多步演化机制被推论为描述褐煤的低温氧化。此外，根据氧化动力学实验和活性基团的演化规律，考虑到热效应的准确性，确定了反应线的比例。根据演化机理和反应比，得到各温度区间的热效应和放热强度。计算了褐煤的最短自燃期，并与实验值进行了比较，证明了所推论的活性基团演化机理和热效应计算是可靠的。