均相条件下NO与CO、NCO的反应机理研究

基于量子化学密度泛函理论研究了NO与CO、NCO在均相条件下的反应机理并进行了动力学和平衡常数的分析. CO与NO的均相反应存在两条反应路径：两者首先反应形成中间体CNO₂,CNO₂不易稳定存在，其继续与CO、NO反应分别生成NCO、N₂O. NCO的生成速率大于N₂O,但两条反应路径的反应速率常数都很小.与已发现的反应路径相比，反应中间体CNO₂可以降低均相条件下CO与NO的反应能垒，分析发现CNO₂中的N原子是易发生反应的活性位点. NCO与NO的反应同样存在两条路径，优势反应路径随温度升高而改变，但非优势路径对反应的贡献不能忽略，分析平衡常数可知N₂的存在对反应影响可以忽略，因此燃烧环境中NCO与NO的反应既生成N₂O和CO,也生成N₂和CO₂.

Homogeneous Reaction Mechanism of NO Reduction With CO and NCO

Based on the density functional theory of quantum chemistry, the homogeneous reaction mechanism of NO with CO and NCO were studied, respectively. Kinetic analysis and calculation of equilibrium constants were carried out for the above reactions. There are two reaction paths for the homogeneous reaction of CO and NO: one CO and one NO first react to form the intermediate CNO2, which is not easy to exist stably, CNO2 reacts with CO and NO to generate NCO and N2O, respectively. The formation rate of NCO is higher than N2O, but the reaction rate constants of both reaction pathways are small. Compared with the available reaction path in the literatures, the presence of intermediate substance CNO2 in the new reaction path could significantly reduce the energy barrier for CO and NO reaction under homogeneous conditions. N atom in CNO2 was determined to be the active site. The dominant reaction path of NCO and NO reactions changes with increasing temperature, but the contribution of the non-dominant path to the reaction cannot be ignored. Analysis of the chemical equilibrium constant shows that the presence of N2 has a negligible effect on the reactions of NCO and NO. The reaction of NCO and NO in the combustion environment generates N2O and CO, as well as N2 and CO2.