In Situ Direct Sampling Mass Spectrometric Study on Formation of Polycyclic Aromatic Hydrocarbons in Toluene Pyrolysis

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• 作者：Bikau Shukla ; Akio Susa ; Akira Miyoshi ; Mitsuo Koshi
• 刊名：Journal of Physical Chemistry A
• 出版年：2007
• 出版时间：August 30, 2007
• 年：2007
• 卷：111
• 期：34
• 页码：8308 - 8324
• 全文大小：1723K
• 年卷期：v.111,no.34(August 30, 2007)
• ISSN：1520-5215

文摘

The gas-phase reaction products of toluene pyrolysis with and without acetylene addition produced in a flowtube reactor at pressures of 8.15-15.11 Torr and temperatures of 1136-1507 K with constant residence time(0.56 s) have been detected in an in situ direct sampling mass spectrometric study by using a vacuum ultravioletsingle-photon ionization time-of-flight mass spectrometry technique. Those products range from methyl radicalto large polycyclic aromatic hydrocarbons (PAHs) of mass 522 amu (C₄₂H₁₈) including smaller species, radicals,polyynes, and PAHs, together with ethynyl, methyl, and phenyl PAHs. On the basis of observed mass spectra,the chemical kinetic mechanisms of the formation of products are discussed. Especially, acetylene is mixedwith toluene to understand the effect of the hydrogen abstraction and acetylene addition (HACA) mechanismon the formation pathways of products in toluene pyrolysis. The most prominent outputs of this work are thedirect detection of large PAHs and new reaction pathways for the formation of PAHs with the major role ofcyclopenta-fused radicals. The basis of this new reaction route is the appearance of different sequences ofmass spectra that well explain the major role of aromatic radicals mainly cyclopenta fused radicals of PAHsresulting from their corresponding methyl PAHs, with active participation of c-C₅H₅, C₆H₅, C₆H₅CH₂,andC₉H₇ in the formation of large PAHs. The role of the HACA only seemed important for the formation ofstable condensed PAHs from unstable primary PAHs with zigzag structure (having triple fusing sites) in onestep by ring growth with two carbon atoms.