霍林河褐煤热解甲烷生成反应类型及动力学的热重-质谱实验与量子化学计算

应用开放体系的热重-质谱联用技术(TG/MS)对未成熟的霍林河褐煤(镜质组最大反射率ROmax为0.33%)进行了热解模拟, 获得了甲烷的在线析出速率曲线. 曲线拟合结果表明, 甲烷生成速率曲线可以分解为5个峰, 结合化学动力学分析, 发现低温阶段甲烷的峰为吸附甲烷析出峰, 其余四个峰为热解甲烷的生成峰, 代表四类不同的化学反应. 将煤的结构特征及量子化学的理论计算相结合, 认为甲烷的生成包括4类反应, 类型1为与氧等杂原子相连的脂碳断裂; 类型2包含了两种反应, 一种是短链脂肪烃类官能团β位断裂, 另一种是所形成的长链脂肪烃类物质二次裂解; 类型3是与芳核直接相连的甲基热解脱落; 类型4为存在于煤结构中脂肪类物质的芳香化.

Reaction Types and Kinetics of Methane Generation from Huolinhe Lignite Pyrolysis by TG/MS Experiment and Quantum Chemical Calculations

Open system pyrolysis modeling of immature Huolinhe lignite (vitrinite reflectivity, ROmax of 0.33%) was carried out and an on-line curve for the methane generation rate was obtained using a thermogravimetric analyzer coupled to a quadrupole mass spectrometer (TG/MS). Five peaks were suitable for curve fitting. A kinetic analysis of these fitted curves indicated that the lowest temperature peak represented desorption of adsorbed methane in coal and the four other peaks were from pyrolytic methane generation. These results indicated four types of reactions as determined by kinetic analysis combined with the structural characterization of coal by 13C-NMR and quantum chemical calculations. From the order of peak fitting, the first type of reaction involves a cleavage of the aliphatic carbons linked to O atoms; the second includes two reactions, a β-secession of short chain aliphatic functional groups and a secondary cracking of long chain aliphatic hydrocarbons that were formed during the primary pyrolysis of coal; the third is a demethylation of methyl-linked aromatic clusters; and the fourth is an aromatization of aliphatic substances within the coal structure and subsequent condensation.