Kinetics and Products of Vinyl + 1,3-Butadiene, a Potential Route to Benzene

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• 作者：Zachary J. Buras ; Enoch E. Dames ; Shamel S. Merchant ; Guozhu Liu ; Rehab M. I. Elsamra ; William H. Green
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：July 16, 2015
• 年：2015
• 卷：119
• 期：28
• 页码：7325-7338
• 全文大小：614K
• ISSN：1520-5215

文摘

The reaction between vinyl radical, C₂H₃, and 1,3-butadiene, 1,3-C₄H₆, has long been recognized as a potential route to benzene, particularly in 1,3-butadiene flames, but the lack of reliable rate coefficients has hindered assessments of its true contribution. Using laser flash photolysis and visible laser absorbance (位 = 423.2 nm), we measured the overall rate coefficient for C₂H₃ + 1,3-C₄H₆, k₁, at 297 K 鈮?T 鈮?494 K and 4 鈮?P 鈮?100 Torr. k₁ was in the high-pressure limit in this range and could be fit by the simple Arrhenius expression k₁ = (1.1 卤 0.2) 脳 10^鈥?2 cm³鈥痬olecule^鈥? s^鈥?鈥痚xp(鈭?.9 卤 0.6 kJ鈥痬ol^鈥?/RT). Using photoionization time-of-flight mass spectrometry, we also investigated the products formed. At T 鈮?494 K and P = 25 Torr, we found only C₆H₉ adduct species, while at 494 K 鈮?T 鈮?700 K and P = 4 Torr, we observed 鈮も埣10% branching to cyclohexadiene in addition to C₆H₉. Quantum chemistry master-equation calculations using the modified strong collision model indicate that n-C₆H₉ is the dominant product at low temperature, consistent with our experimental results, and predict the rate coefficient and branching ratios at higher T where chemically activated channels become important. Predictions of k₁ are in close agreement with our experimental results, allowing us to recommend the following modified Arrhenius expression in the high-pressure limit from 300 to 2000 K: k₁ = 6.5 脳 10^鈥?0 cm³鈥痬olecule^鈥? s^鈥?鈥?i>T^2.40鈥痚xp(鈭?.76 kJ鈥痬ol^鈥?/RT).