Influence of the Storage Material on the Storage of NO<sub>x</sub>at Low Temperatures

Svedberg, Pernilla; Jobson, Edward; Erkfeldt, Sara U; Andersson, Bengt; Larsson, Mikael; Skoglundh, Magnus

doi:10.1023/b:toca.0000029750.36833.6f

Cited by 31 publications

(15 citation statements)

References 20 publications

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“…Ceria-zirconia materials are usually added in three way catalysis for their oxygen storage capacity, but also they are able to store NOx [1][2][3]. In the present work, we have studied the NOx-trap properties of a CeZr material with or without barium addition.…”

Section: Introductionmentioning

confidence: 97%

NOx storage capacity, SO2 resistance and regeneration of Pt/(Ba)/CeZr model catalysts for NOx-trap system

et al. 2007

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NOx storage capacity, sulphur resistance and regeneration of 1wt%Pt/Ce 0.7 Zr 0.3 O 2 (Pt/CeZr) and 1wt%Pt/10wt%BaO/ Ce 0.7 Zr 0.3 O 2 (Pt/Ba/CeZr) catalysts were studied and compared to a 1wt%Pt/10wt%BaO/Al 2 O 3 (Pt/Ba/Al) model catalyst submitted to the same treatments. Pt/Ba/CeZr presents the best NOx storage capacity at 400°C in accordance with basicity measurements by CO 2 TPD and Pt/CeZr shows the better performance at 200°C mainly due to a low sensitivity to CO 2 at this temperature. For all samples, sulphating induces a detrimental effect on NOx storage capacity but regeneration at 550°C under rich conditions generally leads to the total recovery of catalytic performance. However, the nearly complete sulphur elimination is only observed on Pt/CeZr. Moreover, an oxidizing treatment at 800°C leads to partial sulphates elimination on the Pt/CeZr catalyst whereas a stabilization of sulphates on Ba containing species is observed.

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Section: Introductionmentioning

confidence: 97%

NOx storage capacity, SO2 resistance and regeneration of Pt/(Ba)/CeZr model catalysts for NOx-trap system

et al. 2007

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“…Typically, a NSR catalyst consists of Pt and BaO supported on c-alumina, in which Pt acts as a redox catalyst and BaO as a storage component. BaO was shown to have the best NO x storage capability among the alkaline earth metal oxides tested for NO x storage [3]. Many important fundamental and technological aspects in catalytic deNOx processes, including NSR, were summarized in two recent reviews [4,5].…”

mentioning

confidence: 99%

Effect of γ-Al2O3 substrate on NO2 interaction with supported BaO clusters

Cheng

2007

Surface Science

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“…The low temperature peak could be attributed to the removal of weakly adsorbed N2O4 and NO2 +δ species, whereas the high temperature desorption peak could be associated to the decomposition of nitrate species from alumina sites [24,25]. Mg-Al2O3 samples show a similar TPD-profile with an additional peak located around 380 °C, ascribed to the decomposition of NOx stored on magnesium sites [26]. The TPD spectra of Mg-Ce-Al2O3 samples in contrast show a shoulder around 160 °C and two intense peaks located around 330 and 380 °C, respectively.…”

Section: No 2 -Tpd Experimentsmentioning

confidence: 96%

Sulfur Poisoning Effects on Modern Lean NOx Trap Catalysts Components

2019

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In the present work, a series of different materials was investigated in order to enhance the understanding of the role of modern lean NO x trap (LNT) components on the sulfur poisoning and regeneration characteristics. Nine different types of model catalysts were prepared, which mainly consisted of three compounds: (i) Al 2 O 3 , (ii) Mg/Al 2 O 3 , and (iii) Mg/Ce/Al 2 O 3 mixed with Pt, Pd, and Pt-Pd. A micro flow reactor and a diffuse reflectance infrared Fourier transform spectrometer (DRIFTS) were employed in order to investigate the evolution and stability of the species formed during SO 2 poisoning. The results showed that the addition of palladium and magnesium into the LNT formulation can be beneficial for the catalyst desulfation due mainly to the ability to release the sulfur trapped at relatively low temperatures. This was especially evident for Pd/Mg/Al 2 O 3 model catalyst, which demonstrated an efficient LNT desulfation with low H 2 consumption. In contrast, the addition of ceria was found to increase the formation of bulk sulfate species during SO 2 poisoning, which requires higher temperatures for the sulfur removal. The noble metal nature was also observed to play an important role on the SO x storage and release properties. Monometallic Pd-based catalysts exhibited the formation of surface palladium sulfate species during SO 2 exposure, whereas Pt-Pd bimetallic formulations presented higher stability of the sulfur species formed compared to the corresponding Pt-and Pd-monometallic samples.Catalysts 2019, 9, 492 2 of 18 urea [4]. Nevertheless, the LNT system is highly susceptible to sulfur, and its performance can be severely affected as NO x storage sites are blocked by sulfur [5][6][7]. Sulfates formed on the NO x storage sites have higher thermal stability than nitrates and nitrites and, therefore, their decomposition needs very high temperatures and alternating rich/lean exhaust mixtures [8,9]. This does not only lead to higher fuel consumption due to regular desulfation events, but may also cause structural deactivation of the catalyst, such as sintering of precious metals and the formation of mixed oxides (e.g., BaAl 2 O 4 for the reaction between Al 2 O 3 and BaO at high temperatures), affecting the overall NO x storage and reduction activity of the catalyst [10][11][12].Therefore, the sulfur tolerance of modern LNT catalysts should be improved by replacing the NO x trapping material with a component with lower affinity towards sulfation, and with enhanced desorption of sulfur species during regeneration. Barium is frequently employed as a storage material because of its high thermal stability, however, it is responsible for the major LNT catalyst deterioration due to its high affinity for sulfation [13]. Ji et al. [14] studied the incorporation of ceria to Ba-based LNT catalysts and determined to provide a positive impact on LNT performance in the presence of sulfur. Ceria was found to enhance sulfur tolerance of the LNT catalyst by storing sulfur species, which mitigates the sulfation o...

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Influence of the Storage Material on the Storage of NO_xat Low Temperatures

Cited by 31 publications

References 20 publications

NOx storage capacity, SO2 resistance and regeneration of Pt/(Ba)/CeZr model catalysts for NOx-trap system

NOx storage capacity, SO2 resistance and regeneration of Pt/(Ba)/CeZr model catalysts for NOx-trap system

Effect of γ-Al2O3 substrate on NO2 interaction with supported BaO clusters

Sulfur Poisoning Effects on Modern Lean NOx Trap Catalysts Components

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Influence of the Storage Material on the Storage of NOxat Low Temperatures

Cited by 31 publications

References 20 publications

NOx storage capacity, SO2 resistance and regeneration of Pt/(Ba)/CeZr model catalysts for NOx-trap system

NOx storage capacity, SO2 resistance and regeneration of Pt/(Ba)/CeZr model catalysts for NOx-trap system

Effect of γ-Al2O3 substrate on NO2 interaction with supported BaO clusters

Sulfur Poisoning Effects on Modern Lean NOx Trap Catalysts Components

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Influence of the Storage Material on the Storage of NO_xat Low Temperatures