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Redox reaction process between hydrocarbon and adsorbed NOx over lean NOx trap catalyst
Proceedings of the Combustion Institute ( IF 3.4 ) Pub Date : 2018-06-20 , DOI: 10.1016/j.proci.2018.05.113
Bo Li , Chonglin Song , Gang Lv , Chenyang Fan , Xuyang Zhang , Hong Wen , Jingyao Liu

In this study, we investigated the redox reaction between a hydrocarbon (HC) and adsorbed NOx over CuPtBa/Al2O3 lean NOx trap (LNT) catalyst. Experimental characterizations included temperature-programmed desorption (TPD), temperature-programmed reduction (TPR), in situ diffuse reflectance Fourier transform spectroscopy (in situ DRIFTs) and Raman spectroscopy. Density functional theory (DFT) calculations were also performed. The model C3H6 first adsorbed to the catalyst surface, and the resulting C3H6-adsorbed species reacted with adsorbed NOx species to form various intermediates such as: carboxylates, enolic compounds, carbonato complexes, Pt-carbonyls, acid anhydrides, basic hydroxyls, nitrogen-containing organic species, acyl chlorides, and ammonium salts. These intermediates participated in subsequent reactions and finally produced the effluent gases CO2, N2, NH3, and H2O. The decomposition ability of adsorbed NOx species indicated that the NOx species participated in the C3H6 oxidation in the order: adsorbed N2O4 > monodentate nitrates > free ionic nitrates > bulk free ionic nitrates. Carbonaceous materials were generated during the C3H6 oxidation process and were consumed as intermediates by gaseous NOx released upon decomposition of the adsorbed NOx species. In summary, the redox reaction between C3H6 and adsorbed NOx followed the Langmuir–Hinshelwood mechanism, and three reaction routes were proposed for the redox process over the studied catalyst. The activation energy barriers determined by DFT + U calculations for the three routes indicated that the initial dissociation of NO3 species in R(2) occurred more easily than the oxidation of C3H6 species in R(1), delivering the active oxygen species that participated in R(1) and R(3). As the reactions proceeded, the higher energy barrier for the complete dissociation of NO2* indicated that the temperature determined the further decomposition of adsorbed NOx species, and R(1) and R(3) were constrained owing to the limited surface active oxygen species from R(2).



中文翻译:

烃和吸附NO之间的氧化还原反应过程X超贫NO X捕集催化剂

在这项研究中,我们调查了氧化还原反应(HC)的烃之间和吸附NO X以上的Cu的Pt的Ba / Al的2 ö 3贫NO X收集器(LNT)催化剂。实验表征包括程序升温解吸(TPD),程序升温还原(TPR),原位漫反射傅里叶变换光谱法(原位DRIFT)和拉曼光谱。还执行了密度泛函理论(DFT)计算。首先将模型C 3 H 6吸附到催化剂表面,然后将所得的C 3 H 6吸附物与吸附的NO x反应形成各种中间体的化合物,例如:羧酸盐,烯醇化合物,碳酸盐络合物,Pt-羰基化合物,酸酐,碱性羟基,含氮有机物质,酰氯和铵盐。这些中间体参加随后的反应和最后产生的流出气体CO 2,N 2,NH 3和H 2 O.吸附NO的能力分解X物种表明NO X物种参加在C 3 H ^ 6氧化在顺序:吸附的N 2 O 4 >单齿硝酸盐>游离离子硝酸盐>大量游离离子硝酸盐。过程中与C产生的碳质材料3 ħ 6氧化工艺和被消耗,通过气态NO中间体X时所吸附的NO的分解放出X物种。总之,C之间的氧化还原反应3 ħ 6和NO吸附X符合Langmuir-欣谢尔伍德机构,并提出了用于在所研究的催化剂的氧化还原过程中的三个反应路线。通过DFT + U计算为三条路线确定了激活能障碍表明,NO的初始解离3 -中的R物种(2)比R (1)中的C 3 H 6物种的氧化更容易发生,从而传递参与R (1)和R (3)的活性氧物种。随着反应的进行,NO 2 *完全分解的较高能垒表明温度决定了所吸附的NO x物质的进一步分解,并且由于有限的表面活性氧而限制了R (1)和R (3) R (2)中的物种。

更新日期:2019-01-30
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