Kinetic Study of the OH plus Glyoxal Reaction: Experimental Evidence and Quantification of Direct OH Recycling
Kinetic Study of the OH plus Glyoxal Reaction: Experimental Evidence and Quantification of Direct OH Recycling
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DOI：
10.1021/jp4076806
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发表时间：
2013-10-31
影响因子：
2.9
通讯作者：
Shannon, Robin
中科院分区：
文献类型：
--
作者：
Lockhart, James;Blitz, Mark;Shannon, Robin
在总压为5-80 Torr、温度为212-295 K的N2和N2/O2浴气中，通过激光诱导荧光（LIF）监测过量（HCO）（2）中OH的衰减，研究了OH +乙二醛（HCO）（2）反应的动力学。以下速率系数，k（OH+（HCO）2）=（9.7 +/- 1.2），（12.2 +/- 1.6），以及（15.4 +/- 2.0）x 10（-12）cm（3）分子（-1）s（-1）（其中误差表示2 σ水平的统计误差和系统误差估计的组合）在氮气中在295 ℃下测量，250和212 K。速率系数的测量被观察到是独立的总压力，但减少以下添加的O-2的反应单元，直接OH回收相一致。OH产率，Phi（OH），为这个反应进行了量化实验，第一次作为总压力，温度和O-2浓度的函数。实验结果已被参数化使用的化学方案，其中一小部分的HC（O）CO人口迅速解离为HCO + CO，剩余的HC（O）CO热解离或与O-2反应，得到CO2，CO2和再生OH。在212 K下观察到最大Phi（OH）为（0.38 +/- 0.02），与总压力无关，表明HC（O）CO群体的60%在形成时迅速解离。在250 K下观察到类似的定性行为，最大Phi（OH）为（0.31 +/- 0.03）;在295 K下，最大Phi（OH）进一步降低至（0.29 +/- 0.03）。根据参数化，计算出295 K和1 atm空气下的OH产率Phi（OH）= 0.19。结果表明，所提出的机制是一致的，与以前的腔室研究。虽然拟合是稳健的，但实验证据表明，该系统受化学活化的影响，不能完全用热速率系数来描述。简要讨论了测量的大气影响。
The kinetics of the OH + glyoxal, (HCO)(2), reaction have been studied in N-2 and N-2/O-2 bath gas from 5-80 Torr total pressure and 212-295 K, by monitoring the OH decay via laser induced fluorescence (LIF) in excess (HCO)(2). The following rate coefficients, k(OH+(HCO)2) = (9.7 +/- 1.2), (12.2 +/- 1.6), and (15.4 +/- 2.0) x 10(-12) cm(3) molecule(-1) s(-1) (where errors represent a combination of statistical errors at the 2 sigma level and estimates of systematic errors) were measured in nitrogen at temperatures of 295, 250, and 212 K, respectively. Rate coefficient measurements were observed to be independent of total pressure but decreased following the addition of O-2 to the reaction cell, consistent with direct OH recycling. OH yields, Phi(OH), for this reaction were quantified experimentally for the first time as a function of total pressure, temperature, and O-2 concentration. The experimental results have been parametrized using a chemical scheme where a fraction of the HC(O)CO population promptly dissociates to HCO + CO, the remaining HC(O)CO either dissociates thermally or reacts with O-2 to give CO2, CO2 and regenerate OH. A maximum Phi(OH) of (0.38 +/- 0.02) was observed at 212 K, independent of total pressure, suggesting that similar to 60% of the HC(O)CO population promptly dissociates upon formation. Qualitatively similar behavior is observed at 250 K, with a maximum Phi(OH) of (0.31 +/- 0.03); at 295 K, the maximum Phi(OH) decreased further to (0.29 +/- 0.03). From the parametrization, an OH yield of Phi(OH) = 0.19 is calculated for 295 K and 1 atm of air. It is shown that the proposed mechanism is consistent with previous chamber studies. While the fits are robust, experimental evidence suggests that the system is influenced by chemical activation and cannot be fully described by thermal rate coefficients. The atmospheric implications of the measurements are briefly discussed.