On-line pyrolysis-GC-IRMS: isotope fractionation of thermally generated gases from coals
On-line pyrolysis-GC-IRMS: isotope fractionation of thermally generated gases from coals
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DOI：
10.1016/s0016-2361(01)00095-3
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发表时间：
2001-12
期刊：
影响因子：
7.4
通讯作者：
R. Gaschnitz;B. Krooss;P. Gerling;E. Faber;R. Littke
中科院分区：
文献类型：
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作者：
R. Gaschnitz;B. Krooss;P. Gerling;E. Faber;R. Littke
储层气体的同位素组成常用于源岩与天然气的对比。天然气同位素特征的主要控制因素是热成气过程中的动力学同位素分馏。建立了一套新的热解-GC-IRMS在线分析系统，用于研究沉积有机质热成气过程中的同位素动力学分馏。该方法基于100至1100°C温度范围内的开放系统非等温热解，并允许以高采样频率同时监测七种单独热解产物（甲烷、乙烷、乙烯、丙烷、丙烷、一氧化碳和二氧化碳）的同位素组成。由于通过该程序实现的高数据密度，不仅在组成方面而且在同位素特定反应动力学方面对热解曲线进行详细的反应动力学解释是可行的。这种方法和所提供的数据鼓励重新评估现有的概念源岩天然气的相关性，也提供了新的见解控制同位素分馏过程中的热气体生成。目前的结果表明，七个热解产物的同位素组成的高度可变性。虽然富集在the 13 C物种的热解温度增加的一般趋势，观察到的特征逆转这种同位素趋势通常发生甲烷，CO和CO2。这些变化反映了前体结构的同位素组成的差异，这些结构在热解过程中逐渐分解。从这里提出的方法获得的分析数据开辟了开发新的动力学分馏模型的角度，同时考虑到前体结构的同位素变异性和它们的热稳定性。
The isotopic composition of reservoir gases is frequently used for source rock to gas correlations. The prime control on the isotopic signature of gas results from kinetic isotope fractionation during thermal gas generation. A new on-line pyrolysis-GC-IRMS system has been developed as an analytical tool to study the kinetic isotope fractionation during thermal gas generation from sedimentary organic matter. The method is based on open-system non-isothermal pyrolysis in the temperature range from 100 to 1100°C and allows simultaneous monitoring of the isotopic composition of seven individual pyrolysis product (methane, ethane, ethene, propane, propane, carbon monoxide and carbon dioxide) at a high sampling frequency. Due to the high data density achieved by this procedure a detailed reaction kinetic interpretation of the pyrolysis curves in terms not only of compositional but also isotope specific reaction kinetics is feasible. This method and the data presented encourage both the re-evaluation of existing concepts for source-rock to gas correlations and also offer new insights into controls on isotope fractionation during thermal gas generation. Current results indicate a high variability of the isotopic composition of the seven pyrolysis products. Although a general trend of enrichment in the13C species with increasing pyrolysis temperature is observed, characteristic reversals of this isotopic trend are commonly occurring for methane, CO, and CO2. These variations reflect differences in the isotopic composition of the precursor structures, which are progressively decomposed during pyrolysis. The analytical data obtained from the approach presented here open up the perspective of developing new kinetic fractionation models taking into account both the isotopic variability of precursor structures and their thermal stability.