Distinct NO2 Effects on Cu-SSZ-13 and Cu-SSZ-39 in the Selective Catalytic Reduction of NOx with NH3,Environmental Science & Technology

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Distinct NO2 Effects on Cu-SSZ-13 and Cu-SSZ-39 in the Selective Catalytic Reduction of NOx with NH3
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2020-11-17 , DOI: 10.1021/acs.est.0c06256
Na Zhu _{1,

2} , Yulong Shan ₃ , Wenpo Shan _{1,

4} , Yu Sun _{2,

3} , Kuo Liu ₃ , Yan Zhang _{1,

4} , Hong He _{1,

2,

3}

Affiliation

Cu-SSZ-13 and Cu-SSZ-39, with similar structures, are both highly active and hydrothermally stable in the selective catalytic reduction of NO_x with NH₃ (NH₃-SCR), attracting great attention for applications on diesel vehicles. In this study, it was interestingly found that NO₂ has distinct effects on the NO_x conversion over Cu-SSZ-13 and Cu-SSZ-39, with an inhibiting effect for Cu-SSZ-13 but a promoting effect for Cu-SSZ-39. The distinct NO₂ effects were found to be associated with the differences in the reactivity of surface NH₄NO₃, a key intermediate for NH₃-SCR, on these two Cu-based small-pore zeolites. Cu-SSZ-13 has excellent standard SCR activity, but the reactivity of surface NH₄NO₃ with NO is relatively low, which would induce the accumulation of NH₄NO₃ on the surface and thus inhibit NO_x conversion. Surface Brønsted acid sites play key roles in the reduction of surface NH₄NO₃ by NO, and Cu-SSZ-39 showed much higher surface acidity than Cu-SSZ-13. Compared with Cu-SSZ-13, the intrinsic standard SCR activity of Cu-SSZ-39 was lower but NH₄NO₃ could be reduced by NO rapidly on Cu-SSZ-39, even faster than the reduction of NO by the adsorbed NH₃ on Cu active sites; thus, NO_x conversion was promoted by NO₂ on Cu-SSZ-39. This work provides an improved understanding of fast SCR on Cu-based small-pore zeolites.

中文翻译：

NH ₃选择性催化还原NO _x对Cu-SSZ-13和Cu-SSZ-39的不同NO ₂影响

的Cu-SSZ-13和Cu-SSZ-39，具有相似的结构，是在所述选择性催化还原的NO既高度活性和水热稳定的_X与NH ₃（NH ₃ -SCR），吸引极大关注用于在柴油车的应用程序。在这项研究中，有趣的是，发现NO ₂对Cu-SSZ-13和Cu-SSZ-39的NO _x转化具有明显的影响，对Cu-SSZ-13具有抑制作用，但对Cu-SSZ具有促进作用。 -39。发现明显的NO ₂效应与表面NH ₄ NO ₃（NH ₃的关键中间体）的反应性差异有关。-SCR，在这两种铜基小孔沸石上。Cu-SSZ-13具有优异的标准SCR活性，但是表面NH ₄ NO ₃与NO的反应性相对较低，这会引起NH ₄ NO ₃在表面上的积累，从而抑制NO _x转化。表面布朗斯台德酸中心在NO还原表面NH ₄ NO _3中起关键作用，Cu-SSZ-39的表面酸度比Cu-SSZ-13高得多。与Cu-SSZ-13相比，Cu-SSZ-39的内在标准SCR活性较低，但是NH ₄ NO ₃可以在Cu-SSZ-39上迅速被NO还原，甚至比被吸附的NH还原NO更快。₃在铜活性部位上；因此，NO ₂在Cu-SSZ-39上促进了NO _x转化。这项工作提供了对基于铜的小孔沸石上快速SCR的更好理解。

更新日期：2020-12-01

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