Experimental and Theoretical Study on the Thermal Decomposition of C3H6 (Propene)
Experimental and Theoretical Study on the Thermal Decomposition of C3H6 (Propene)
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C3H6（丙烯）热分解的实验与理论研究
DOI：
10.1021/jp5102169
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
and Akira Miyoshi
中科院分区：
文献类型：
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作者：
Wei-Chung Hung;Chieh-Ying Tsai;Hiroyuki Matsui;Niann-Shiah Wang;and Akira Miyoshi
从理论和实验两方面研究了丙烯热单分子分解的机理。通过CBS-QB 3水平的量子化学计算，对可能的反应途径进行了势能面分析，并对主要反应途径进行了RRKM/主方程计算.本文用高灵敏度的探测技术（ARAS，探测限为1011 atoms cm ~（-3）），在反射激波（0.5- 1.0ppmC_3H_6稀释在Ar中，1450-1710 K，2.0atm）后，实验上观察到H原子随时间的演化。本研究的目的是通过实验和理论相结合的产率和H原子产生率的研究，检查的主要产品渠道。 目前的量子化学计算确定反应（1a-1d）为产物通道的候选者：C3 H6 → aC 3 H5（烯丙基自由基）+ H（1a），C3 H6 → CH 3 + C2 H3（乙烯基自由基）（1b），C3 H6 → CH 4+：CCH 2（单重态亚乙烯基自由基）（1c）和C3 H6 → C3 H4（丙二烯）+ H2（1d）。RRKM计算显示（1a）、（1b）和（1c）的支化分数分别约为0.8、0.2和0.01。反应（1d）和其他产物通道可以忽略不计（<0.1%），在本实验条件下，支化分数的压力依赖性很小。H原子的实验产率（1.7-2.0）是一致的考虑从C3 H5和C2 H3的快速随后的热分解的H-原子生产的理论分支分数。由氢原子的时间分布曲线，求得C3 H6的总热分解速率为Ln（k1/s-1）=（38.05 ± 1.18）-（48.91 ± 1.85）× 103 K/T，与理论预测值吻合较好.
The mechanism of the thermal unimolecular decomposition of C3H6(propene) is studied both theoretically and experimentally. The potential energy surfaces for possible reaction pathways are investigated by CBS-QB3 level of quantum chemical calculations, and RRKM/master-equation calculation is performed for the main channels. The time evolutions of H atoms are observed experimentally by using a highly sensitive detection technique (ARAS, detection limit ≈ 1011atoms cm–3) behind reflected shock waves (0.5–1.0 ppm C3H6diluted in Ar, 1450–1710 K at 2.0 atm). The objective of this study is to examine the main product channels by combining the experimental and theoretical investigations on the yield and the rates of H atom production. Present quantum chemical calculations identify reactions (1a–1d) as the candidates of product channels: C3H6→ aC3H5(allyl radical) + H (1a), C3H6→ CH3+ C2H3(vinyl radical) (1b), C3H6→ CH4+ :CCH2(singlet vinyldene radical) (1c), and C3H6→ C3H4(allene) + H2(1d). The RRKM calculations reveal the branching fractions for (1a), (1b), and (1c) to be approximately 0.8, 0.2, and 0.01, respectively. Reaction (1d) and other product channels are negligible (< 0.1 %), and the pressure dependence of the branching fraction is small under the present experimental conditions. The experimental yield of H atoms (1.7–2.0) is consistent with the theoretical branching fractions considering the H-atom production from the rapid subsequent thermal decomposition of a C3H5and C2H3. From the observed time profiles of H atoms, the rate of overall thermal decomposition of C3H6can be evaluated as Ln(k1/s–1) = (38.05 ± 1.18) – (48.91 ± 1.85) × 103K/T, which is in excellent agreement with the theoretical prediction.