Shock wave studies of the pyrolysis of fluorocarbon oxygenates. I. The thermal dissociation of C3F6O and CF3COF.
Shock wave studies of the pyrolysis of fluorocarbon oxygenates. I. The thermal dissociation of C3F6O and CF3COF.
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DOI：
10.1039/c6cp06816b
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发表时间：
2017-01
期刊：
影响因子：
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通讯作者：
C. Cobos;K. Hintzer;L. Sölter;E. Tellbach;A. Thaler;J. Troe
中科院分区：
文献类型：
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作者：
C. Cobos;K. Hintzer;L. Sölter;E. Tellbach;A. Thaler;J. Troe
在 630 至 1000 K 的 Ar 中高度稀释的冲击波中，研究了六氟环氧丙烷 (C3F6O) 热分解为全氟乙酰氟、CF3COF 和 CF2。测得的速率常数 k1 = 1.1 × 1014 exp(-162(±4) kJ mol-1/RT) s-1 与文献数据和建模结果非常吻合。使用该反应作为前体，进一步加热CF3COF和CF2的等摩尔混合物。将实验观察与理论模型（在 CBS-QB3 和 G4MP2 从头开始复合水平上）相结合，CF3COF 显示在两个通道上解离，要么导致 CF2 + COF2 要么导致 CF3 + FCO。通过监测 CF2 信号，确定 1400 至 1900 K 之间的支化比。两个通道的高压速率常数由理论模型获得，如下所示： k5,∞(CF3COF → CF2 + COF2) = 7.1 × 1014 exp(-320 kJ mol-1/RT) s-1 和 k6,∞(CF3COF → CF3 + FCO) = 3.9 × 1015 exp(-355 kJ mol-1/RT) s-1。在[Ar] ≈ 5 × 10-6 mol cm-3 条件下获得的实验结果与模型结果一致，表明反应处于单分子解离的衰减范围内。还分析了 CF3COF 解离后的二次反应机制。
The thermal decomposition of hexafluoropropylene oxide, C3F6O, to perfluoroacetyl fluoride, CF3COF, and CF2 has been studied in shock waves highly diluted in Ar between 630 and 1000 K. The measured rate constant k1 = 1.1 × 1014 exp(-162(±4) kJ mol-1/RT) s-1 agrees well with literature data and modelling results. Using the reaction as a precursor, equimolar mixtures of CF3COF and CF2 were further heated. Combining experimental observations with theoretical modelling (on the CBS-QB3 and G4MP2 ab initio composite levels), CF3COF is shown to dissociate on two channels, either leading to CF2 + COF2 or to CF3 + FCO. By monitoring the CF2 signals, the branching ratio was determined between 1400 and 1900 K. The high pressure rate constants for the two channels were obtained from theoretical modelling as k5,∞(CF3COF → CF2 + COF2) = 7.1 × 1014 exp(-320 kJ mol-1/RT) s-1 and k6,∞(CF3COF → CF3 + FCO) = 3.9 × 1015 exp(-355 kJ mol-1/RT) s-1. The experimental results obtained at [Ar] ≈ 5 × 10-6 mol cm-3 were consistent with modelling results, showing that the reaction is in the falloff range of the unimolecular dissociation. The mechanism of secondary reactions following CF3COF dissociation has been analysed as well.