Kinetic and product yield study of the heterogeneous gas-surface reaction of anthracene and ozone
Kinetic and product yield study of the heterogeneous gas-surface reaction of anthracene and ozone
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DOI：
10.1021/jp056125d
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发表时间：
2006-03-16
影响因子：
2.9
通讯作者：
Abbatt, JPD
中科院分区：
文献类型：
--
作者：
Kwamena, NOA;Earp, ME;Abbatt, JPD
关于多环芳烃（PAHs）与臭氧非均相反应产物的定量资料很少。因此，我们进行了第一次定量研究，调查了蒽和臭氧的非均相气-表面反应的动力学和产物，作为臭氧浓度和相对湿度（RH）的函数。该反应在干燥条件下（RH < 1%）表现出蒽损失的拟一阶动力学，拟一阶速率系数与气相臭氧浓度具有Langmuir-Hinshelwood依赖关系，拟合参数为臭氧吸附平衡常数k -o3 = (2.8 +/- 0.9) × 10(-1) 5cm(3)，最大拟一阶速率系数k(max)(I) = (6.4 +/- 1.8) × 10(-3) s（-1）。当实验在大约50%和60%的相对湿度下进行时，动力学不变。在产物研究中，观察到蒽醌产物产率与臭氧浓度的非线性关系，类似于Langmuir吸附图，并得出以下拟合参数：K-o3 = (3.4 +/- 1.5) x 10-15 cm(3)，最大蒽醌产率ANQ(max) % = 30 +/- 18%。在较高相对湿度条件下进行的实验（类似于50%和60% RH）表明，蒽醌的产率不受气相水存在的影响。值得注意的是，蒽的损失动力学和蒽酮的产率对臭氧分配到表面的程度有相似的依赖性。这可以用一种机制来理解，即蒽损失和蒽醌形成的速率决定步骤都是由表面吸附的臭氧量驱动的。我们的研究结果表明，在与大气相关的臭氧浓度（100 ppb）下，在干燥和高相对湿度条件下，蒽的臭氧分解产生的蒽醌产量将小于1%。
Little quantitative information exists regarding the products of the heterogeneous reaction of polycyclic aromatic hydrocarbons (PAHs) and ozone. We have, therefore, performed the first quantitative study investigating the kinetics and products of the heterogeneous gas-surface reaction of anthracene and ozone as a function of ozone concentration and relative humidity (RH). The reaction exhibited pseudo-first-order kinetics for anthracene loss under dry conditions (RH < 1%) and the pseudo-first-order rate coefficients displayed a Langmuir-Hinshelwood dependence on the gas-phase ozone concentration, which yielded the following fitting parameters: the equilibrium constant for ozone adsorption, K-o3 = (2.8 +/- 0.9) x 10(-1)5 cm(3) and the maximum pseudo-first-order rate coefficient, k(max)(I) = (6.4 +/- 1.8) x 10(-3) s(-1). The kinetics were unchanged when experiments were performed at approximately 50% and 60% RH. In the product study, a nonlinear dependence, similar to a Langmuir adsorption plot, of the anthraquinone product yield as a function of ozone concentration was observed and resulted in the following fitting parameters: K-o3 = (3.4 +/- 1.5) x 10-15 cm(3) and the maximum anthraquinone yield, ANQ(max) % = 30 +/- 18%. Experiments performed under higher relative humidity conditions (similar to 50% and 60% RH) revealed that the anthraquinone yield was unaffected by the presence of gas-phase water. It is noteworthy that both the anthracene loss kinetics and the anthraquitione yields have a similar dependence on the degree of ozone partitioning to the surface. This can be understood in terms of a mechanism whereby the rate-determining steps for anthracene loss and anthraquinone formation are both driven by the amounts of ozone adsorbed on the surface. Our results suggest that at atmospherically relevant ozone concentrations (100 ppb) the anthraquinone yield from the ozonolysis of anthracene under dry and high relative humidity conditions would be less than 1%.