Abstract To improve the understanding of cyclopentadiene-based high-density liquid hydrocarbon fuels combustion chemistry, the pyrolysis experiments of 1,3-cyclopentadiene (c-C5H6), quadricyclane (QC) and ethylnorbornane (EthNB, reported in our recent work: Wang et al.,2020), were performed in a flow reactor at atmospheric and high pressure over 348–1173 K. The mole fraction profiles of products in three fuels pyrolysis were obtained using online GC–MS/FID. Based on theoretical calculations and literature research, a universal kinetic model (397 species and 1522 reactions) of QC and EthNB, incorporating the sub-mechanisms of c-C5H6 and polycyclic aromatics, was constructed in this work. It was validated against the present data and pyrolysis data of c-C5H6 as well as norbornane in literature with reasonable reproducibility. The rate of production analysis shows that the retro-Diels-Alder reaction to c-C5H6 plus C2H2 is always the dominant path to 2,5-norbornadiene (NBD, the only isomer product of QC) consumption at atmospheric and high pressures, whereas the contribution of isomerization to 1,3,5-cycloheptatriene increases with the increasing pressure and is almost equal to that of the former at high pressure and low conversion. The aromatics formation channels in QC pyrolysis are affected by the presence of C2H2 and different from those of c-C5H6 pyrolysis, especially under high pressure. For EthNB decomposition, the open-ring and H-abstraction reactions play a dominant role. The C2-C6 alkene products are formed via the decomposition of ethylnorbornyl radicals and the further reactions of these alkenes are the precursors of aromatics in EthNB pyrolysis. Although QC and EthNB have a similar U-shaped carbon skeleton structure, the difference is that the former has an extra four-membered ring with more strain energy, which leads a lower initial decomposition temperature. Similarly, the extra C C double bonds, in NBD compared to EthNB, result in more c-C5H6 and C2H2 formation and further increase the growing tendency of initial PAH.

中文翻译：

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四环烷和2-乙基降冰片烷从常压到高压热解的实验和建模研究

摘要 为了提高对基于环戊二烯的高密度液态烃燃料燃烧化学的理解，1,3-环戊二烯 (c-C5H6)、四环烷 (QC) 和乙基降冰片烷 (EthNB，在我们最近的工作中报道：Wang et al.,2020)，在常压和高压下超过 348-1173 K 的流动反应器中进行。使用在线 GC-MS/FID 获得三种燃料热解中产物的摩尔分数分布。在理论计算和文献研究的基础上，本文构建了 QC 和 EthNB 的通用动力学模型（397 个物种和 1522 个反应），结合了 c-C5H6 和多环芳烃的子机制。它已根据文献中 c-C5H6 和降冰片烷的现有数据和热解数据进行了验证，具有合理的重现性。产率分析表明，在常压和高压下，逆狄尔斯-阿尔德反应生成 c-C5H6 加 C2H2 始终是 2,5-降冰片二烯（NBD，QC 的唯一异构体产品）消耗的主要途径，而异构化对1,3,5-环庚三烯的贡献随着压力的增加而增加，并且在高压和低转化率下几乎等于前者。QC 热解中芳烃形成通道受 C2H2 存在的影响，与 c-C5H6 热解不同，尤其是在高压下。对于 EthNB 分解，开环和 H-抽象反应起主导作用。C2-C6 烯烃产物是通过乙基降冰片基自由基的分解形成的，这些烯烃的进一步反应是 EthNB 热解中芳烃的前体。虽然QC和EthNB具有相似的U形碳骨架结构，但不同的是前者多了一个四元环，应变能更大，初始分解温度更低。同样，与 EthNB 相比，NBD 中额外的 CC 双键导致更多的 c-C5H6 和 C2H2 形成，并进一步增加初始 PAH 的增长趋势。