A Shock Tube and Modeling Study about Anisole Pyrolysis Using Time-Resolved CO Absorption Measurements
A Shock Tube and Modeling Study about Anisole Pyrolysis Using Time-Resolved CO Absorption Measurements
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DOI：
10.1002/kin.21105
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发表时间：
2017-09
影响因子：
1.5
通讯作者：
B. Shu;J. Herzler;S. Peukert;M. Fikri;C. Schulz
中科院分区：
文献类型：
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作者：
B. Shu;J. Herzler;S. Peukert;M. Fikri;C. Schulz
利用4.7 μm附近基频振动带的转动跃迁，通过高灵敏度的CO浓度吸收测量，研究了反射激波后苯甲醚（C6 H5 OCH 3）的热解。在1000和1270 K之间，在1.3-1.6 bar的冲击加热的C6 H5 OCH 3/Ar混合物中监测时间分辨的CO摩尔分数。C6 H5 OCH 3的分解完全通过均裂解离进行，反应速率为k1，形成甲基（CH 3）和苯氧基（C6 H5 O）自由基。随后的C6 H5 O的分解通过环重排和键解离产生CO。为了确定避免二次反应的C6 H5 O分解的速率常数k2，烯丙基苯基醚（C6 H5 OC 3 H5）被用作C6 H5 O的替代源。在970和1170 K之间，在1.4 bar下研究了其分解。在G4理论水平上重新计算了C6 H5 O离解的势能面。由单分子速率理论确定的速率常数与实验结果符合得很好。然而，获得的速率k2 = 9.1 × 1013 exp（-220.3 kJ mol-1/RT）s-1显著高于之前报道的速率（比Lin和Lin，J.Phys.Chem.1986，90，425-431; Frank等人，1994; Carstensen and Dean，2012，respectively）。在本工作中，用从C6 H5 OC 3 H5的实验中获得的值代替k2之后，发现测量的CO浓度分布与基于Nowakowska等人的机理的模拟之间具有良好的一致性。在较长的反应时间内，C6 H5 O和CH 3生成甲酚的双分子反应被认为是影响CO浓度的最重要的反应。
The pyrolysis of anisole (C6H5OCH3) was studied behind reflected shock waves via highly sensitive absorption measurements of CO concentration using a rotational transition in the fundamental vibrational band near 4.7 µm. Time-resolved CO mole fractions were monitored in shock-heated C6H5OCH3/Ar mixtures between 1000 and 1270 K at 1.3–1.6 bar. The decomposition of C6H5OCH3 proceeds exclusively via homolytic dissociation, with reaction rate k1, forming methyl (CH3) and phenoxy (C6H5O) radicals. The subsequent decomposition of C6H5O by ring rearrangement and bond dissociation yields CO. To determine the rate constant k2 of C6H5O decomposition avoiding secondary reactions, allyl phenyl ether (C6H5OC3H5) was used as an alternative source for C6H5O. Its decomposition was studied between 970 and 1170 K at ∼1.4 bar. The potential-energy surface of C6H5O dissociation has been reevaluated at the G4 level of theory. Rate constants determined from unimolecular rate theory are in good agreement with the present experiments. However, the obtained rates k2 = 9.1 × 1013 exp(−220.3 kJ mol−1/RT)s−1 are significantly higher than those reported before (factor 6, 2, and 1.5 faster than those data reported by Lin and Lin, J. Phys. Chem. 1986, 90, 425–431; Frank et al., 1994; Carstensen and Dean, 2012, respectively). Good agreement was found between the measured CO concentration profiles and simulations based on the mechanism of Nowakowska et al. after substituting k2 by the value obtained from experiments on C6H5OC3H5 in this work. The bimolecular reaction of C6H5O and CH3 toward cresol was identified as the most important reaction influencing the CO concentration at longer reaction time.