Investigations on Pyrolysis of Isooctane at Low and Atmospheric Pressures

The pyrolysis experiments
of isooctane were conducted in a flow
tube at the temperature from 848 to 1123 K at 30 Torr and from 723
to 998 K at 760 Torr. The pyrolysis intermediates and products were
photoionized by synchrotron vacuum ultraviolet and detected by a reflectron
time-of-flight mass spectrometer. A pyrolysis model was developed
to compare the results with the experimental data to improve the combustion
mechanism and to clarify the important pyrolysis pathways of isooctane.
The model includes 321 species and 1569 reactions. It can be revealed
from the rate of production and sensitivity analyses that in the initial
decomposition of isooctane, unimolecular dissociation reactions are
more important than H-abstraction reactions. The reaction pathways
and branching ratios are affected by the change of pressures. The
reaction networks of C5–C2 unsaturated
hydrocarbons are dominated by the production of isobutene and propene
via various reaction channels. Small amounts of benzene and fulvene
are formed from the reactions of smaller radicals and molecules.

异辛烷热解实验于流动管式反应器中开展，实验压强分别为30 Torr与760 Torr，对应温度范围依次为848~1123 K及723~998 K。热解中间体与产物通过同步辐射真空紫外光进行光电离，并由反射式飞行时间质谱仪完成检测。本研究构建了热解模型，将模拟结果与实验数据进行比对，以优化燃烧反应机理并明确异辛烷关键热解路径。该模型涵盖321种组分与1569个基元反应。通过生成速率与敏感性分析可知，在异辛烷初始分解阶段，单分子解离反应相较于氢提取反应占据主导地位。反应路径与分支比随压强变化发生显著改变。C2~C5不饱和烃的反应网络主要通过多条反应通道生成异丁烯与丙烯。少量苯与富烯由小分子自由基及分子间的反应生成。