Kinetics of the OH + C2H2 reaction in the presence of O2
Kinetics of the OH + C2H2 reaction in the presence of O2
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O2 存在下 OH C2H2 反应的动力学
DOI：
10.1039/ft9969201459
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Cornelius Zetzschn
中科院分区：
文献类型：
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作者：
B. Bohn;M. Siese;Cornelius Zetzschn
用脉冲H_2O_2光解产生OH，然后用连续紫外激光长光程吸收检测法测定了乙炔气相反应中OH自由基的去除速率常数。在1.5~100 kPa的压降范围内，研究了以N_2、O_2和合成空气为缓冲气体时，反应速率常数随压力的变化关系。在N2中，压力依赖性可以通过加德纳的经验表达式：k ={（k ∞）a+（k0 [M]）a} 1/a来描述，其中使用参数a =-pseudo。在给定的压力范围内，反应速率常数k ∞ =（1.07 ± 0.07）× 10 - 12cm~3s~（-1），k0 =（3.9 ± 1.6）× 10 - 29cm~6s~（-1）。较小的有效速率常数，在O2的存在下，由于OH的快速再生通道。根据上述表达式，得到了以O2和合成空气为缓冲气体时的速率常数k ∞分别为（4.6 ± 0.2）和（3.1 ± 0.1）× 10 - 13 cm~3 s~（-1），k_0分别为（1.8 ± 0.2）和（1.9 ± 0.5）× 10 - 29 cm~6 s~（-1）。与N2相比，在O2和合成空气中的脱落行为几乎没有差异，表明OH再生产率与压力无关。另一方面，发现该产率随着O2混合比而降低。提出了一个动力学模型，定性地解释了这种效果与不同的化学性质的非热化OH-乙炔加合物关于O2。该模型证实了测量显示出一个显着更强的依赖性的再生产率上的O2-He混合物中的O2混合比。
Room-temperature rate constants for the removal of OH radicals in the gas-phase reaction with acetylene have been determined using pulsed H2O2 photolysis production of OH followed by cw UV-laser long-path absorption detection. The pressure dependences of the rate constants in N2, O2 and synthetic air as buffer gases have been investigated in the fall-off range between 1.5 and 100 k Pa. In N2 the pressure dependence can be described by the empirical expression of Gardiner: k={(k∞)a+(k0[M])a}1/a, using the parameter a=–⅓. This results in the rate constants k∞=(1.07 ± 0.07)× 10–12 cm3 s–1, and k0=(3.9 ± 1.6)× 10–29 cm6 s–1 for the given pressure range. Smaller effective rate constants were obtained in the presence of O2, owing to a fast regeneration channel for OH. In terms of the above expression the rate constants k∞=(4.6 ± 0.2) and (3.1 ± 0.1)× 10–13 cm3 s–1 and k0=(1.8 ± 0.2) and (1.9 ± 0.5)× 10–29 cm6 s–1 were obtained for O2 and synthetic air as buffer gases, respectively. Compared with N2 there is virtually no difference in the fall-off behaviour in O2 and synthetic air, indicating that the OH regeneration yield is independent of pressure. On the other hand, this yield was found to decrease with the O2 mixing ratio. A kinetic model is proposed that qualitatively explains this effect with different chemical properties of non-thermalized OH–acetylene adducts with regard to O2. This model is confirmed by measurements showing a significantly stronger dependence of the regeneration yield on the O2 mixing ratio in O2–He mixtures.