焦炭催化CO还原NO的反应机理研究

利用密度泛函理论,研究了焦炭催化作用下CO还原NO的化学反应机理,优化得到了均相反应路径以及在Zigzag和Armchair型焦炭表面上的异相反应路径中所有驻点的几何构型与能量,并对三条反应路径进行了动力学分析。结果表明,均相NO还原反应的活化能为254.06 kJ/mol,而Zigzag型与Armchair型焦炭表面NO异相还原反应的活化能分别为86.94与52.16 kJ/mol,说明焦炭在NO还原反应中能够起到催化作用。在焦炭表面进行的CO还原NO的反应路径经历N_2形成、N_2释放及两步CO_2释放四个阶段,最终生成一个N_2分子与两个CO_2分子。此外,通过对比不同路径下异相反应的能量变化与动力学参数可知,焦炭表面结构对NO还原反应特性存在较大影响;与Zigzag型焦炭表面相比,基于Armchair型焦炭表面的NO还原反应决速步能垒值更低且反应速率更快,表明在Armchair型焦炭表面上的NO还原反应更易进行。

Reaction mechanism of NO reduction with CO catalyzed by char

The mechanism of NO reduction with CO catalyzed by char was studied via density function theory (DFT). The optimized configurations and stationary points of homogeneous and heterogeneous reactions on the char surfaces of Zigzag and Armchair were obtained. Finally, kinetic analysis for both homogeneous and heterogeneous reactions were carried out. The results show that the activation energy of homogeneous NO reduction reaction is 254.06 kJ/mol, while only 86.94 and 52.16 kJ/mol for heterogeneous reaction on Zigzag and Armchair models, respectively. This indicates that char is able to play an activating role in the NO reduction reaction. The NO reduction reaction on the char surface undergoes four stages of N₂ formation, N₂ release, and two stages of CO₂ release, and finally generates one N₂ molecule and two CO₂ molecules. Moreover, the surface structure of char has a great influence on the characteristics of NO reduction reaction. Compared to Zigzag char surface, NO reduction reaction with Armchair-type has a lower energy barriers and higher reaction rate constants. That is, the NO reacts easily with CO on the Armchair surface.