干酪根组成结构及其热解生油特性的红外光谱研究

对五种不同地区油页岩中干酪根进行了固体KBr压片红外吸收光谱分析,并通过曲线分峰拟合建立了干酪根中脂肪烃区域结构参数的定量测定方法。利用TG-FTIR联用分析技术对干酪根在20 ℃/min升温速率下热解挥发分析出组分在线定性分析,得到了脂肪烃结构参数随热裂解过程的反应特性及变化规律。研究表明,油页岩中干酪根由脂肪烃结构、芳香烃结构和含氧等官能团三部分组成。脂肪烃结构相对含量为18.5%~78.2%,并均以含长链亚甲基结构为主。随着演化程度的加深,干酪根中脂肪烃含量逐渐减少,生油能力也不断降低。干酪根热分解主要发生在350~520 ℃,520 ℃后热失重现象趋于平缓,在此温度下各样品残余半焦的质量分数为19.5%~52.2%。在线红外分析结果表明,干酪根热裂解过程中先析出游离水,随后发生解聚和脱水反应,主要的烷基侧链不断脱落、环化及含氧基团逐渐断裂生成各种烷烃类、羧酸类、醇类和醛类等物质,直至形成更加稳定的类石墨态结构。

FT-IR study on composition of oil shale kerogen and its pyrolysis oil generation characteristics

Five oil shale kerogens from different regions were analyzed by KBr-FTIR spectra, and a quantitative determination method of structural parameters of kerogen aliphatic hydrocarbon was established by peak-fitting analysis. Thermogravimetric (TG) and Fourier transform infrared spectroscopy (FT-IR) analysis was used to online analyze devolatilization components of kerogen pyrolyzed at 20 ℃/min. The reactivity characteristic and variation of structural parameters of aliphatic hydrocarbon with pyrolysis time were obtained. The results show that the oil shale kerogen was composed of aliphatic hydrocarbon, aromatic hydrocarbon and oxygen functional groups. The relative content of aliphatic hydrocarbon structure, mainly long chain methylene, reaches 18.5%~78.2%. With increasing degree of kerogen evolution, the content of aliphatic hydrocarbon and capacity of oil generation decrease. The decomposition of kerogen mainly occurs during 350~520 ℃. The thermal weightless is mild when above 520 ℃ at which mass fraction of the residual char is 19.5%~52.2%. FT-IR analysis shows that free water releases out firstly during pyrolysis, subsequently depolymerization and dehydration reactions occur, and in which main side chains of alkane fall off and cyclization and oxygen-containing groups break into various of hydrocarbons, acids, alcohols, aldehydes, etc. until more stable graphite-like structure is formed.