NOx adsorption study over Pt–Ba/alumina catalysts: FT-IR and pulse experiments

Nova, Isabella; Castoldi, L.; Lietti, Luca; Tronconi, Enrico; Forzatti, Pio; Prinetto, F.; Ghiotti, G.

doi:10.1016/j.jcat.2003.11.013

Cited by 265 publications

(82 citation statements)

References 24 publications

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“…As time continued, more gas oxygen could be adsorbed and participate in the oxidation such that nitrites were transformed gradually to nitrates. These processes are in accordance with data observed by the FTIR on Pt/Ba/Al 2 O 3 [12]. It should be stressed that Co plays an outstanding role in the catalysts.…”

Section: Dynamic No X Storage and Reduction Performancessupporting

confidence: 90%

“…This reaction route is widely used to explain the adsorption mechanism on Pt/Ba/Al 2 O 3 . However, Nova et al [12] proposed another mechanism to explain adsorption called the "nitrite route", in which NO can be directly absorbed on the surface by forming nitrites that are subsequently oxidized to nitrates by O 2 . This "nitrites route" may also play a significant role in NO x uptake on both Co and/or Pt containing catalysts, and detailed progress will be discussed later by FTIR experiments.…”

Section: No X Storage Performances At Different Temperaturesmentioning

confidence: 99%

“…Most of previous studies have focused on catalyst compositions and operating conditions that have a great impact on the performance of NO x storage and reduction [7][8][9][10][11][12][13]. For Ba-containing catalysts, noble metal species and their dispersion can lead to different NO oxidation activity during the lean phase [8,14,15] thus directly influencing subsequent adsorption on Ba sites.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Co addition to Pt/Ba/Al2O3 system for NOx storage and reduction

Wang

2010

Applied Catalysis B: Environmental

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a b s t r a c tA comparative study of Pt/Ba/Al 2 O 3 , Co/Ba/Al 2 O 3 , Pt/Co/Al 2 O 3 and Pt/Co/Ba/Al 2 O 3 was performed in regards to their NO x storage capacities and NO oxidation abilities as a function of temperature. The nitrate stability and dynamic behaviors of NO x storage reduction during lean/rich fuel cycles using hydrogen as a reductant were also investigated over these catalysts. It was found that Pt/Co/Ba/Al 2 O 3 possessed the largest NO x storage capacity within the temperature range of 200-350 • C. The existence of Co not only improved the oxidation of NO to NO 2 under lean conditions, but also enhanced the release and reduction of NO x during the rich phase. The Pt and Co co-supported catalysts showed better NO x storage reduction activity and higher N 2 selectivity than Pt supported Ba/Al 2 O 3 catalysts within the tested temperature range. As for Pt/Co/Ba/Al 2 O 3 , high conversion was obtained at either a low reductant concentration with long duration time or a high reductant concentration with short duration time during the rich phase. In situ FTIR studies showed that NO x adsorption over Co-containing catalysts takes "nitrite route" as an important pathway. The intimate contact of Co and Ba/Al could accelerate nitrite/nitrate formation and the synergistic effect of Pt and Co could accelerate NO x reduction.

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Section: Dynamic No X Storage and Reduction Performancessupporting

confidence: 90%

Section: No X Storage Performances At Different Temperaturesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Co addition to Pt/Ba/Al2O3 system for NOx storage and reduction

Wang

2010

Applied Catalysis B: Environmental

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“…Their rate equations suggest that NO adsorbs on both of these sites without the assistance of either a noble metal or gas phase oxygen. Experimental evidence suggests that NO can indeed adsorb on BaO/Al 2 O 3 catalysts but that the rate and level of adsorption are too low in the absence of O 2 or Pt (Elizundia et al, 2007;Nova et al, 2004;Prinetto et al, 2001;Prinetto et al, 2003). Even when pretreatment is carried out in the presence of O 2 , which could lead to formation of surface peroxides (Hess and Lunsford, 2002;Hess and Lunsford, 2003), BaO/Al 2 O 3 formulations adsorb only a negligible amount of NO Prinetto et al, 2003), suggesting that Pt plays a crucial role in NO uptake.…”

Section: Introductionmentioning

confidence: 99%

Simulation of lean NOx trap performance with microkinetic chemistry and without mass transfer.

Larson¹,

Daw

Pihl

et al. 2011

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A microkinetic chemical reaction mechanism capable of describing both the storage and regeneration processes in a fully formulated lean NO x trap (LNT) is presented. The mechanism includes steps occurring on the precious metal, barium oxide (NO x storage), and cerium oxide (oxygen storage) sites of the catalyst. The complete reaction set is used in conjunction with a transient plug flow reactor code to simulate not only conventional storage/regeneration cycles with a CO/H 2 reductant, but also steady flow temperature sweep experiments that were previously analyzed with just a precious metal mechanism and a steady state code. The results show that NO x storage is not negligible during some of the temperature ramps, necessitating a re-evaluation of the precious metal kinetic parameters. The parameters for the entire mechanism are inferred by finding the best overall fit to the complete set of experiments. Rigorous thermodynamic consistency is enforced for parallel reaction pathways and with respect to known data for all of the gas phase species involved. It is found that, with a few minor exceptions, all of the basic experimental observations can be reproduced with these purely kinetic simulations, i.e., without including mass-transfer limitations. In addition to accounting for normal cycling behavior, the final mechanism should provide a starting point for the description of further LNT phenomena such as desulfation and the role of alternative reductants. 4 ACKNOWLEDGMENTSThe authors thank Dr. Andrew E. Lutz, formerly of Sandia, for initial development of the Chemkin-based transient plug flow reactor code (TPLUG). The efforts at Oak Ridge were sponsored by the U.S.

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“…Experimental evidence suggests that NO can indeed adsorb on BaO/Al 2 O 3 catalysts but that the rate and level of adsorption are too low in the absence of O 2 or Pt [21][22][23][24]. Even when pretreatment is carried out in the presence of O 2 , which could lead to formation of surface peroxides [25,26], BaO/Al 2 O 3 formulations adsorb only a negligible amount of NO [22,23], suggesting that Pt plays a crucial role in NO uptake. Among other things, the present model attempts to show how NO can be taken up readily without being adsorbed directly on BaO or BaCO 3 sites.…”

Section: Introductionmentioning

confidence: 99%

Microkinetic Modeling of Lean NO<sub>x</sub> Trap Storage and Regeneration

Larson

Chakravarthy

Pihl

et al. 2011

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A microkinetic chemical reaction mechanism capable of describing both the storage and regeneration processes in a fully formulated lean NO x trap (LNT) is presented. The mechanism includes steps occurring on the precious metal, barium oxide (NO x storage), and cerium oxide (oxygen storage) sites of the catalyst. The complete reaction set is used in conjunction with a transient plug flow reactor code (including boundary layer mass transfer) to simulate not only a set of long storage/regeneration cycles with a CO/H 2 reductant, but also a series of steady flow temperature sweep experiments that were previously analyzed with just a precious metal mechanism and a steady state code neglecting mass transfer. The results show that, while mass transfer effects are generally minor, NO x storage is not negligible during some of the temperature ramps, necessitating a re-evaluation of the precious metal kinetic parameters. The parameters for the entire mechanism are inferred by finding the best overall fit to the complete set of experiments. Rigorous thermodynamic consistency is enforced for parallel reaction pathways and with respect to known data for all of the gas phase species involved. It is found that, with a few minor exceptions, all of the basic experimental observations can be reproduced with the transient simulations. In addition to accounting for normal cycling behavior, the final mechanism should provide a starting point for the description of further LNT phenomena such as desulfation and the role of alternative reductants. 4 ACKNOWLEDGMENTSThe authors thank Dr. Andrew Lutz, formerly of Sandia, for initial development of the Chemkinbased transient plug flow reactor code (TPLUG).

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NOx adsorption study over Pt–Ba/alumina catalysts: FT-IR and pulse experiments

Cited by 265 publications

References 24 publications

Effect of Co addition to Pt/Ba/Al2O3 system for NOx storage and reduction

Effect of Co addition to Pt/Ba/Al2O3 system for NOx storage and reduction

Simulation of lean NOx trap performance with microkinetic chemistry and without mass transfer.

Microkinetic Modeling of Lean NO<sub>x</sub> Trap Storage and Regeneration

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