Mechanistic insight into selective catalytic combustion of acrylonitrile (C2H3CN): NCO formation and its further transformation towards N2
Mechanistic insight into selective catalytic combustion of acrylonitrile (C2H3CN): NCO formation and its further transformation towards N2
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丙烯腈（C2H3CN）选择性催化燃烧的机理洞察：NCO 的形成及其进一步向 N2 的转化
DOI：
10.1039/c6cp08930e
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发表时间：
2017
影响因子：
3.3
通讯作者：
Yingxia Li
中科院分区：
文献类型：
--
作者：
Ning Liu;Xiaoning Yuan;Runduo Zhang;Rongrong Xu;Yingxia Li
采用浸渍法制备了一系列分子筛催化剂M(Cu，Fe，Co)-ZSM-5，并将其用于丙烯腈(AN-SCC)的选择催化燃烧。进一步选择AN转化活性最高、氮产率最高的Cu-ZSM-5分子筛进行AN-SCC机理研究，采用了实验[原位漫反射红外傅里叶变换光谱]和理论[密度泛函理论]相结合的方法。原位漂移结果表明，在300℃时，AN-SCC通过酰氨基中间体(-CONH2)和NH3的中间体遵循水解机理，而在300℃时，AN-SCC通过NCO中间体遵循氧化机理。DFT模拟结果表明：(I)在O_2气态的解离原子O的辅助下，NCO可以在[Cu]+活性中心上氧化生成NCO；(Ii)NCO的进一步反应可能有三种反应途径，即NCO直接解离、NCO偶联和NO+NCO反应；(Iii)最后一种反应途径(NO+NCO)具有最低的能垒，是最有可能的反应途径，其中NO可以通过NCO的氧化生成。能量计算和微观动力学分析表明，NCO生成步骤是整个催化循环的速率控制步骤，其能量垒为17.0kcal−-1，正向反应速率常数为2.20×10~7 S−-1。
A series of zeolite catalysts, M(Cu, Fe, Co)-ZSM-5, was prepared by an impregnation method and evaluated for the selective catalytic combustion of acrylonitrile (AN-SCC). Cu-ZSM-5, exhibiting the highest AN conversion activity and best N2 yield, was further selected for an AN-SCC mechanism investigation, wherein both experimental [in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS)] and theoretical [density functional theory (DFT)] approaches were employed. The in situ DRIFTS revealed that AN-SCC followed a hydrolysis mechanism at T < 300 °C via intermediates of acylamino species (–CONH2) and NH3, while it followed an oxidation mechanism at T > 300 °C via an intermediate of NCO. The DFT simulations gave much deeper insights suggesting that: (i) the NCO could be generated by oxidation of AN over [Cu]+ active sites, with an assistance of dissociated atomic O from gaseous O2; (ii) three types of reaction routes could be proposed for the further reaction of NCO to produce N2, namely NCO direct dissociation, NCO coupling, and NO + NCO reaction; and (iii) the last route (NO + NCO), possessing the lowest energy barrier, was the most probable reaction pathway, wherein the NO could be produced by oxidation of NCO. The DFT energy calculation results and microkinetic analyses revealed that the NCO generation step, possessing an energy barrier of 17.0 kcal mol−1 and a forward reaction rate constant of 2.20 × 107 s−1, was the rate-determining step of the whole catalytic cycle.