ABSTRACT

The mechanism of N₂O homogeneous and heterogeneous reactions with CO were investigated using density functional theory (DFT). The M06-2X method with the 6–311 G(d) basis set were adopted for geometry optimization and energy calculations of each configuration (reactants, intermediates, transition states and products). Thermodynamic and kinetic analyzes were also conducted to study the influence of temperature on the reaction process. Calculation results showed that there are two channels for the homogeneous reaction between N₂O and CO. In addition, the heterogeneous reduction reaction of N₂O and CO has two possible reaction pathways due to the different adsorption configurations of CO on char surface. From thermodynamic analysis, the enthalpy difference (ΔH) and Gibbs free energy difference (ΔG) of the homogeneous and heterogeneous reactions are both negative, which indicates that the reaction of N₂O and CO is an exothermic process and can take place spontaneously. For the both homogeneous and heterogeneous reactions between N₂O and CO, the equilibrium constant of the N₂O and CO reaction is always higher than 10⁵ at 800 ~ 1800 K, suggesting that the reaction can be carried out completely. From the kinetic analysis, activation energy of the heterogeneous reaction (137.26 kJ/mol) is much lower than that of the homogeneous reactions (224.53 kJ/mol and 215.89 kJ/mol), which indicates that the reduction reaction of N₂O with CO is more likely to take place on char surface. The calculation results explain the reaction mechanism of N₂O and CO, which can provide a theoretical foundation for N₂O emission.

摘要

使用密度泛函理论 (DFT) 研究了 N _{2 O 与 CO 的均相和多相反应的机理。}采用具有 6–311 G(d) 基组的 M06-2X 方法进行几何优化和每种配置（反应物、中间体、过渡态和产物）的能量计算。还进行了热力学和动力学分析以研究温度对反应过程的影响。计算结果表明，N ₂ O 和CO 的均相反应有两个通道。此外，由于CO 在炭表面的吸附构型不同，N _{2 O 和CO 的非均相还原反应有两种可能的反应途径。}从热力学分析，焓差（Δ均相和非均相反应的H )和吉布斯自由能差( ΔG )均为负值，说明N ₂ O与CO的反应是放热过程，可以自发进行。_{对于N 2} O和CO的均相和非均相反应，N ₂ O和CO反应的平衡常数在800～1800 K时始终高于10 ⁵，表明反应可以完全进行。从动力学分析可知，非均相反应的活化能（137.26 kJ/mol）远低于均相反应的活化能（224.53 kJ/mol和215.89 kJ/mol），这表明N _{2的还原反应}O 与 CO 更可能发生在炭表面上。计算结果解释了N ₂ O与CO的反应机理，可为N ₂ O排放提供理论依据。