NO_x storage and reduction over flame-made M/MgAl₂O₄ (M = Pt, Pd, and Rh): A comparative study

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• 作者：Sounak Roy^a ; Niels van Vegten^a ; Nobutaka Maeda^a ; Alfons Baiker^a ; ^b ; ^{baiker@chem.ethz.ch}
• 关键词：NOx storage and reduction ; Platinum ; Palladium ; Rhodium ; MgAl2O4 ; Spinel ; Dynamic cycling behavior ; Time-resolved IR spectroscopy
• 刊名：Applied Catalysis B ; Environmental
• 出版年：2012
• 期刊代码：4_09263373
• 类别：ce
• 出版时间：30 May, 2012
• 卷：119-120
• 期：Complete
• 页码：279-286
• 文件大小：1268 K

摘要

Various NO_x storage-reduction (NSR) catalysts with 1&#xA0;wt%noble metal loading (Pt, Pd, or Rh) dispersed on MgAl₂O₄ have been synthesized by single step flame spray pyrolysis. The as-prepared powders consisting of nonporous nanoparticles were characterized by X-ray diffraction, scanning transmission electron microscopy, nitrogen adsorption-desorption, CO chemisorption and thermogravimetric methods. Different reduction agents were applied in the fuel rich cycles: H₂, CO or C₃H₆. Processes occurring during fuel rich and lean cycles were analyzed in detail by means of time-resolved diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and thermogravimetry combined with mass spectroscopy. With H₂ as reductant, Pt/MgAl₂O₄ showed the best performance at short regeneration time (<50&#xA0;s), followed by Rh/MgAl₂O₄ and Pd/MgAl₂O₄. However, if CO or C₃H₆ were used as reductant, Rh/MgAl₂O₄ outperformed both other catalysts, especially at longer regeneration times (>50&#xA0;s). NO_x storage on these catalysts was mainly restricted to surface species, although bulk nitrate species were identified by DRIFTS as well. The latter were not completely reduced under the experimental conditions used.