Wide temperature range (T=295 K and 770-1305 K) study of the kinetics of the reactions HCO plus NO and HCO+N02using frequency modulation spectroscopyt
Wide temperature range (T=295 K and 770-1305 K) study of the kinetics of the reactions HCO plus NO and HCO+N02using frequency modulation spectroscopyt
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DOI：
10.1039/b704197g
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发表时间：
2007-08-21
影响因子：
3.3
通讯作者：
Friedrichs, G.
中科院分区：
文献类型：
--
作者：
Dammeier, J.;Colberg, M.;Friedrichs, G.
反应 (1) (HCO + NO -> HNO + CO) 和反应 (2) (HCO + NO2 产物) 的速率常数已在反射冲击波后 770 K < T < 1305 K 之间的温度下测量，出于一致性检查的目的，在室温下的慢流反应器中进行了测量。 HCO 自由基是通过 193 nm 准分子激光光解氩气中含有乙二醛、(CHO)(2) 和 NO 或 NO2 的稀释气体混合物产生的，并使用调频 (FM) 吸收光谱进行监测。基于综合反应机理的动力学模拟表明，可以从测量的 HCO 曲线中灵敏地提取标题反应的速率常数。确定的高温速率常数为 k(1)(769-1307 K) = (7.1 +/- 2.7) x 10(12) cm(3) mol(-1) s(-1) 和 k(2)(804-1186 K) = (3.3 +/- 1.8) x 10(13) cm(3) mol(-1) s(-1)。发现室温值与现有文献数据非常一致，并表明这两种反应基本上与温度无关。反应（1）的弱温度依赖性可以通过占主导地位的直接提取途径和复合物形成机制的相互作用来解释。两种途径均产生产物 HNO + CO。与反应 (1) 相比，没有发现证据表明直接高温提取通道对反应 (2) 有显着贡献。在这里，观察到的与温度无关的总速率常数可以通过具有多个产物通道的复合物形成机制来描述。提供了与温度密切相关的通道分支比的详细信息。此外，反应(7)的高温速率常数OH + (CHO)(2)已确定为k(7)，近似于1.1 X 10(13) cm(3) mol(-1) s(-1)。
The rate constants for reaction (1), HCO + NO -> HNO + CO, and reaction (2), HCO + NO2 products, have been measured at temperatures between 770 K < T < 1305 K behind reflected shock waves and, for the purpose of a consistency check, in a slow flow reactor at room temperature. HCO radicals were generated by 193 nm excimer laser photolysis of diluted gas mixtures containing glyoxal, (CHO)(2), and NO or NO2 in argon and were monitored using frequency modulation (FM) absorption spectroscopy. Kinetic simulations based on a comprehensive reaction mechanism showed that the rate constants for the title reactions could be sensitively extracted from the measured HCO profiles. The determined high temperature rate constants are k(1)(769-1307 K) = (7.1 +/- 2.7) x 10(12) cm(3) mol(-1) s(-1) and k(2)(804-1186 K) = (3.3 +/- 1.8) x 10(13) cm(3) mol(-1) s(-1). The room temperature values were found to be in very good agreement with existing literature data and show that both reactions are essentially temperature independent. The weak temperature dependence of reaction (1) can be explained by the interplay of a dominating direct abstraction pathway and a complex-forming mechanism. Both pathways yield the products HNO + CO. In contrast to reaction (1), no evidence for a significant contribution of a direct high temperature abstraction channel was found for reaction (2). Here, the observed temperature independent overall rate constant can be described by a complex-forming mechanism with several product channels. Detailed information on the strongly temperature dependent channel branching ratios is provided. Moreover, the high temperature rate constant of reaction (7), OH + (CHO)(2), has been determined to be k(7)approximate to 1.1 X 10(13) cm(3) mol(-1) s(-1).