Role of Phenyl Radicals in the Growth of Polycyclic Aromatic Hydrocarbons

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• 作者：Bikau Shukla ; Akio Susa ; Akira Miyoshi ; Mitsuo Koshi
• 刊名：Journal of Physical Chemistry A
• 出版年：2008
• 出版时间：March 20, 2008
• 年：2008
• 卷：112
• 期：11
• 页码：2362 - 2369
• 全文大小：300K
• 年卷期：v.112,no.11(March 20, 2008)
• ISSN：1520-5215

文摘

To investigate the role of phenyl radical in the growth of PAHs (polycyclic aromatic hydrocarbons), pyrolysisof toluene with and without benzene has been studied by using a heatable tubular reactor couple with anin-situ sampling vacuum ultraviolet (VUV) single photon ionization (SPI) time-of-flight mass spectrometer(TOFMS) at temperatures 1155-1467 K and a pressure of 10.02 Torr with 0.56 s residence time. Whenbenzene was added, a significant increase of phenyl addition products (biphenyl, terphenyl, and triphenylene)was observed and the mass spectra showed a clear regular sequence with an interval of ~74 mass number,corresponding to the phenyl addition (+C₆H₅) followed by H-elimination (-H) and cyclization (-H₂). Theanalysis showed that the PAC (phenyl addition/cylization) mechanism is efficient for the growth of PAHswithout a triple fusing site, for which the HACA (hydrogen abstraction/C₂H₂ addition) step is inefficient, andproduces PAHs with five-membered rings. The PAC process was also suggested to be efficient in the subsequentgrowth of PAHs with five-membered rings. The role of the PAC mechanism in combustion conditions isdiscussed in relation to the importance of disordered five-membered ring structure in fullerene or soot core.