Characterization and reactivity of Ce-promoted PtBa lean NOx trap catalysts

Infantes‐Molina, Antonia; Righini, Laura; Castoldi, L.; Loricera, C.V.; Fierro, J.L.G.; Sin, A.; Lietti, Luca

doi:10.1016/j.cattod.2012.07.036

Cited by 25 publications

(17 citation statements)

References 38 publications

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“…The experimental NOx/O2 molar ratios for CZ and Ba6/CZ are collected in Table 3. As can be observed, in the case of CZ, the experimental NOx/O2 molar ratio is 2.8 at low temperature, suggesting a coexistence of mostly nitrites and nitrates on the catalyst surface, in accordance with the literature for ceria-based catalysts at low temperatures [19,54]. On the other hand, at high temperatures, a value near 1.3 is calculated, in line with the presence of nitrates (as verified by in situ DRIFTS experiments, Figure S3 on SI) adsorbed on this catalyst.…”

Section: Thermal Desorption Of Stored No Xsupporting

confidence: 90%

“…On the other hand, at high temperatures, a value near 1.3 is calculated, in line with the presence of nitrates (as verified by in situ DRIFTS experiments, Figure S3 on SI) adsorbed on this catalyst. On the contrary, Ba6/CZ presents values very close to 1.3, from 250 • C, which is theoretically attributed to barium nitrate decomposition [19], if it is assumed that most part of stored NO x species are located on the Ba sites (reactions ( 14)-( 16)). Therefore, it seems reasonable to establish that the NO x species are stored mostly as nitrates in Ba6/CZ.…”

Section: Thermal Desorption Of Stored No Xmentioning

confidence: 97%

“…NO 2 evolution is not detected, but at the highest temperatures (~450 • C, a double concomitant contribution NO/O 2 appears, similar to CZ). Since these peaks are shifted to higher temperatures (compared with those of CZ), this suggests that a lower amount of NO x remains on the catalyst surface at the end of the cycling process, and that these species are more stable [19,34,56]; therefore, higher temperatures are required for these ad-NO x species to suffer complete decomposition.…”

Section: Thermal Desorption Of Stored No Xmentioning

confidence: 99%

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NOx Reduction Pathways during LNT Operation over Ceria Containing Catalysts: Effect of Copper Presence and Barium Content

et al. 2021

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Ceria-based catalysts, with Cu in substitution of noble metals, were studied in a vertical microreactor system under isothermal conditions, where NOx was previously stored, followed by the reduction step conducted under H2. The possible remaining ad-NOx species after the reduction stage, were investigated by Temperature Programmed Desorption in He. In situ DRIFTS was used as a complementary technique for the analysis of the surface species formation/transformation on the catalysts’ surface. Catalysts containing both Ba and Cu were found to be selective in the NOx reduction, producing N2 and minor amounts of NH3 during the reduction step, as well as NO. The different ceria-based formulations (containing copper and/or barium) were prepared and tested at two different temperatures in the NOx reduction (NSR) processes. Their catalytic activities were analyzed in terms of their compositions and have been useful in the elucidation of the possible origin and relevant pathways for NOx reduction product formation, which seems to involve the oxygen vacancies of the ceria-based materials (whose generation seems to be promoted by copper) during the rich step. The scope of this work involves an interdisciplinary study of the impact that catalysts’ formulations (noble metal-free) have on their LNT performance under simulated conditions, thus covering aspects of Materials Science and Chemical Engineering in a highly applied context, related to the development of control strategies for hybrid powertrains and/or the reduction of the impact of cold-start emissions.

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Section: Thermal Desorption Of Stored No Xsupporting

confidence: 90%

Section: Thermal Desorption Of Stored No Xmentioning

confidence: 97%

Section: Thermal Desorption Of Stored No Xmentioning

confidence: 99%

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NOx Reduction Pathways during LNT Operation over Ceria Containing Catalysts: Effect of Copper Presence and Barium Content

et al. 2021

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“…The sample has been characterized by XRD diffraction using a Philips PW 1050/70 diffractometer; peaks related to microcrystalline γ-Al 2 O 3 , orthorhombic and monoclinic BaCO 3 (traces), and small ones possibly related to Pt 0 have been observed. 32 2.2. Apparatus and Procedures.…”

Section: Methodsmentioning

confidence: 99%

n-Heptane As a Reducing Agent in the NO_x Removal over a Pt–Ba/Al₂O₃ NSR Catalyst

et al. 2014

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“…The addition of ceria, which has become a major component in catalyst compositions leads to superior NO x storage efficiencies, especially at temperatures below 300 °C [19,20]. Furthermore, ceria plays a substantial role in the water-gas-shift reaction as it provides hydrogen for the regeneration during rich periods and it has a positive impact on the NO x storage/release chemistry due to its interplay with platinum [21,22,23,24]. The mechanisms of NO x storage on ceria under lean conditions involve the formation of various ad-NO x species, such as linear, bidentate and chelating nitrites and nitrates.…”

Section: Introductionmentioning

confidence: 99%

Improved NOx Storage/Release Properties of Ceria-Based Lean NOx Trap Compositions with MnOx Modification

et al. 2019

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Ceria/spinel-based lean NOx trap compositions with and without barium were modified with MnOx via incipient wetness impregnation. The effect of the MnOx layer on the aged materials (850 °C) as to the NOx storage and release properties was investigated via NOx adsorption (500 ppm NO/5% O2/balance N2) carried out at 300 °C in a dual-bed with a 1% Pt/Al2O3 catalyst placed upstream of the samples to generate sufficient amounts of NO2 required for efficient NOx storage. Subsequent temperature programmed desorption (TPD) experiments were carried out under N2 from 300 °C to 700 °C. The addition of MnOx to the barium free composition led to a slightly reduced NOx storage capacity but all of the ad-NOx species were released from this material at significantly lower temperatures (ΔT ≈ 100 °C). The formation of a MnOx layer between ceria/spinel and barium had a remarkable effect on ageing stability as the formation of BaAl2O4 was suppressed in favour of BaMnO3. The presence of this phase resulted in an increased NOx storage capacity and lower desorption temperatures. Furthermore, NOx adsorption experiments carried out in absence of the Pt-catalyst also revealed an unexpected high NOx storage ability at low NO2/NO ratios, which could make this composition suitable for various lean NOx trap catalysts (LNT) related applications.

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Characterization and reactivity of Ce-promoted PtBa lean NOx trap catalysts

Cited by 25 publications

References 38 publications

NOx Reduction Pathways during LNT Operation over Ceria Containing Catalysts: Effect of Copper Presence and Barium Content

NOx Reduction Pathways during LNT Operation over Ceria Containing Catalysts: Effect of Copper Presence and Barium Content

n-Heptane As a Reducing Agent in the NO_x Removal over a Pt–Ba/Al₂O₃ NSR Catalyst

Improved NOx Storage/Release Properties of Ceria-Based Lean NOx Trap Compositions with MnOx Modification

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Characterization and reactivity of Ce-promoted PtBa lean NOx trap catalysts

Cited by 25 publications

References 38 publications

NOx Reduction Pathways during LNT Operation over Ceria Containing Catalysts: Effect of Copper Presence and Barium Content

NOx Reduction Pathways during LNT Operation over Ceria Containing Catalysts: Effect of Copper Presence and Barium Content

n-Heptane As a Reducing Agent in the NOx Removal over a Pt–Ba/Al2O3 NSR Catalyst

Improved NOx Storage/Release Properties of Ceria-Based Lean NOx Trap Compositions with MnOx Modification

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n-Heptane As a Reducing Agent in the NO_x Removal over a Pt–Ba/Al₂O₃ NSR Catalyst