煤焦边缘模型异相还原NO的Mayer键级变化分析

Variation analysis of Mayer bond order during the heterogeneous reduction reaction between NO and char edge models

为掌握煤焦对NO异相还原反应规律,揭示焦炭氮迁移转化的微观机理,选取armchair型含氮煤焦边缘模型和zigzag型煤焦边缘模型作为研究对象,基于密度泛函理论计算各个键的Mayer键级,研究上述各煤焦边缘模型化合物对NO气体异相吸附、还原和解吸的过程。结果表明:NO气体分子以side-on形式与armchair型含氮煤焦边缘模型发生异相还原反应,N—O键的Mayer键级达到最小值0.984 6,受热时N—O键容易发生断裂,最终释放出N2和CO;两个NO气体分子与zigzag型煤焦边缘模型发生异相还原反应,一个NO分子以side-on形式吸附在煤焦边缘模型表面,进而形成一个五元环中间体,此时O4—N5键级为最小值1.002 5,而另一个NO分子会以O-down的模式吸附在C3键位上,反应最终释放N2;Mayer键级理论可以有效地研究分子水平条件下煤焦边缘模型对NO异相还原反应的机理。

In order to master the rules of heterogeneous reduction between NO and char edge models, and to reveal the microcosmic mechanisms of migration and transformation for char nitrogen, the processes of heterogeneous adsorption, reduction and desorption of NO on the char edge model compounds in armchair and zigzag configurations were re- searched. The algorithm of density functional theory was applied to calculate each bond＇ s Mayer bond order. The re- sults indicate that N2 and CO are released in the process of heterogeneous reduction reaction of NO on the char edge model surface in armchair configuration. The Mayer bond order of N--O is the minimum（0. 984 6） so the bond of N- O is prone to be broken under a certain temperature. N2 is produced in the process of heterogeneous reduction reaction of two NO molecules on the char edge model in zigzag configuration. One NO molecule is adsorbed on the surface of char edge model in zigzag configuration by the side-on form and then an intermediate with five-membered ring is formed. The Mayer bond order of O4--N5 is the minimum （ 1. 002 5 ） at the moment. The other NO molecule is ad- sorbed on the position of C3 by the O-down form. The theory of Mayer bond order can be effectively used to research the heterogeneous reduction reaction mechanisms of NO on the char edge models surface at the molecular level.