Formation mechanisms of soot from high-molecular-weight polycyclic aromatic hydrocarbons
Formation mechanisms of soot from high-molecular-weight polycyclic aromatic hydrocarbons
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DOI：
10.1016/j.combustflame.2015.03.022
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发表时间：
2015-06
影响因子：
4.4
通讯作者：
K. Ono;Yoshiya Matsukawa;Kazuki Dewa;A. Watanabe;Kaname Takahashi;Y. Saito;Y. Matsushita;H. Aoki;Koki Era;T. Aoki;Togo Yamaguchi
中科院分区：
文献类型：
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作者：
K. Ono;Yoshiya Matsukawa;Kazuki Dewa;A. Watanabe;Kaname Takahashi;Y. Saito;Y. Matsushita;H. Aoki;Koki Era;T. Aoki;Togo Yamaguchi
在1400-1650 K温度范围内，对苯、乙炔、苯与乙炔或2-7环多环芳烃的混合物进行了等温层流热解实验。使用扫描迁移率粒度仪（SMPS）分析了碳烟和新生碳烟的粒度分布（PSD）。使用扫描电子显微镜（SEM）检查具有相同迁移率粒径的颗粒的形态，其中通过差示迁移率分析仪（DMA）辅助的热泳取样对网格进行取样。乙炔在1400 K下热解产生的碳烟与苯和PAH添加剂热解产生的碳烟相比，具有最高的数浓度和对数正态分布。在1500 K时，具有三个或更多个锯齿形位点的环的多环芳烃的热解显著增加了数浓度，尽管添加的碳浓度小于乙炔。此外，二苯并[a，e]芘，它具有三个扶手椅网站，抑制烟灰的形成，这表明海湾网站很容易形成，各向异性的多环芳烃的形成抑制二聚化。通过添加二苯并[a，e]芘形成的烟炱的形态表现出10 nm的初级颗粒直径和类似的初级颗粒，而通过添加具有Z字形位点的PAH形成的烟炱的形态清楚地表明具有20-40 nm的初级颗粒直径的结构。这些观察结果表明，初期烟尘形成的二聚体或小集群的大的多环芳烃通过芳香族分子加成的芳香族基团的机制被称为PAH加成环化（PAH-AC）机制在高温下，而中等大小的多环芳烃开发通过氢提取碳加成（HACA）机制在相对较低的温度下形成集群和初期烟尘。
The feedstocks, including benzene, acetylene, and benzene with acetylene or 2–7 ring PAH, were pyrolyzed in an isothermal laminar flow at 1400–1650 K. The particle size distributions (PSDs) of soot and nascent soot were analyzed using a scanning mobility particle sizer (SMPS). The morphology of particles with the same mobility particle diameter was examined using a scanning electron microscope (SEM), where the grid was sampled via thermophoretic sampling assisted by a differential mobility analyzer (DMA). The soot produced by the pyrolysis of acetylene at 1400 K exhibited the highest number concentration and a log-normal distribution compared with those of the soot produced by the pyrolysis of benzene and the PAH additives. At 1500 K, the pyrolysis of PAHs with three or more rings with zigzag sites significantly increased the number concentration, although the added carbon concentration was smaller than that of acetylene. The addition of dibenzo[a,e]pyrene, which possesses three armchair sites, inhibited soot formation, suggesting that the bay site is easily formed and that the formation of anisotropic PAHs inhibits dimerization. The morphology of the soot formed by the addition of dibenzo[a,e]pyrene exhibited a primary particle diameter of 10 nm and similar primary particles, whereas the morphology of the soot formed by the addition of PAHs with zigzag sites clearly indicated a structure with a primary particle diameter of 20–40 nm. These observations indicate that the incipient soot is formed by the formation of dimers or small clusters of large PAHs via the mechanisms of aromatic molecule addition to aromatic radicals referred to as the PAH–addition cyclization (PAH–AC) mechanism at high temperatures, whereas moderate-sized PAHs developed via the hydrogen-abstraction–carbon-addition (HACA) mechanism form clusters and incipient soot at relatively low temperatures.