The new concept 3-way catalyst for automotive lean-burn engine: NOx storage and reduction catalyst

Takahashi, Naoki; Shinjoh, Hirofumi; Iijima, T.; Suzuki, Tadashi; Yamazaki, Kiyoshi; Yokota, Kenji; Suzuki, Hiromasa; Miyoshi, Naoto; Matsumoto, Shinichi; Tanizawa, Tsuneyuki; Tanaka, Toshiaki; Tateishi, Syu-shi; Kasahara, Kouichi

doi:10.1016/0920-5861(95)00173-5

Cited by 778 publications

(455 citation statements)

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“…In figure 8 (top) figure 9. As confirmed by the reference spectra of bulk Ba(NO 2 ) 2 and Ba(NO 3 ) 2 , the characteristic band at 1250 cm )1 present in barium nitrite disappears during calcination. This confirms that NO evolution centered at 210°C is related to Ba(NO 2 ) 2 decomposition.…”

Section: Thermal Stability Of No Adsorbed On Different Catalystssupporting

confidence: 52%

“…Commercial c-Al 2 O 3 (BET surface area 210 m 2 /g), SiO 2 (200 m 2 /g) and ZrO 2 (60 m 2 /g) were impregnated with precursor solutions of Pt(NH 3 ) 2 (NO 2 ) 2 and Ba(CH 3 COO) 2 to a final loading of active metals of 1 wt% Pt and 17 wt% Ba. Catalysts were then dried at 80°C for 12 h and finally calcined at 500°C for 5 h.…”

Section: Methodsmentioning

confidence: 99%

“…Sample temperature was controlled with a thermocouple directly in contact with the catalyst powder. Spectra were recorded at a resolution of 4 cm )1 and bulk, KBr diluted, BaCO 3 , Ba(NO 3 ) 2 , Ba(NO 2 ) 2 , Ba(OH) 2 and BaO were also measured and used as reference spectra.…”

Section: Methodsmentioning

confidence: 99%

“…NO x storage catalysts for mixed lean conditions containing Al 2 O 3 -supported noble and alkaline earth metals were patented by Toyota [1] in 1994. In 1996, Takahashi et al [2] proposed a storage mechanism in which NO is oxidized on Pt to NO 2 , then stored as Ba(NO 3 ) 2 and subsequently reduced by HC activated on Pt sites. The primary role of Ba as storage compound was shown in [3][4][5], whereas some debate is still open about the kind and amount of Ba containing species active during NO x storage.…”

Section: Introductionmentioning

confidence: 99%

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Role of Support in Lean DeNO_xCatalysis

Piacentini

Maciejewski

Bürgi

et al. 2004

Topics in Catalysis

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FTIR and pulse thermal analysis were applied to investigate catalysts containing Pt (1 wt%)/Ba (17 wt%) supported on c-Al 2 O 3 , SiO 2 and ZrO 2 . The aim was to learn how the support material affects the thermal stability of barium carbonate and its activity in the reaction to bulk Ba(NO 3 ) 2 . The lower thermal stability of BaCO 3 in alumina supported samples was found to influence the formation of barium nitrate during the NO x storage process. Quantification of Ba(NO 3 ) 2 formed during NO x storage indicated that for alumina supported catalysts only ca. 30% of barium present in the sample is involved in the storage process. The low thermal stability found for alumina supported barium nitrite excludes its role in the formation of barium nitrate during interaction of NO x with the catalyst at 300°C. The studies indicate that c-Al 2 O 3 plays a major role in influencing the thermal stability of BaCO 3 and Ba(NO 3 ) 2 . This finding seems to be relevant for the higher activity of c-Al 2 O 3 -supported catalysts in NO x storage reduction reactions. KEY WORDS:Lean DeNO x ; BaCO 3 ; Ba(NO 3 ) 2 and Ba(NO 2 ) 2 thermal stability; pulse thermal analysis; role of the support in NO x storage.

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Section: Thermal Stability Of No Adsorbed On Different Catalystssupporting

confidence: 52%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Role of Support in Lean DeNO_xCatalysis

Piacentini

Maciejewski

Bürgi

et al. 2004

Topics in Catalysis

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“…For the conventional gasoline engines, three-way catalysts (TWC) can reduce toxic gases effectively under a stoichiometric air to fuel ratio (14.5); however TWC is not effective in NO x after treatment in diesel engines operating under oxygenrich lean conditions (where the air to fuel ratio greater than 14.5). NO x storage reduction (NSR) catalysts were developed as an alternative technology [1][2][3]. Conventional NSR catalysts are composed of three main components, Pt, Al 2 O 3 , and BaO where BaO functions as the NO x storage component.…”

Section: Introductionmentioning

confidence: 99%

Palladium doped perovskite-based NO oxidation catalysts: The role of Pd and B-sites for NOx adsorption behavior via in-situ spectroscopy

Say

Doğaç

Vovk

et al. 2014

Applied Catalysis B: Environmental

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a b s t r a c tPerovskite-based materials (LaMnO 3 , Pd/LaMnO 3 , LaCoO 3 and Pd/LaCoO 3 ) were synthesized, characterized (via BET, XRD, Raman spectroscopy, XPS and TEM) and their NO x (x = 1,2) adsorption characteristics were investigated (via in-situ FTIR and TPD) as a function of the nature of the B-site cation (i.e. Mn vs Co), Pd/PdO incorporation and H 2 -pretreatment. NO x adsorption on of LaMnO 3 was found to be significantly higher than LaCoO 3 , in line with the higher SSA of LaMnO 3 . Incorporation of PdO nanoparticles with an average diameter of ca. 4 nm did not have a significant effect on the amount of NO 2 adsorbed on fresh LaMnO 3 and LaCoO 3 . TPD experiments suggested that saturation of fresh LaMnO 3 , Pd/LaMnO 3 , LaCoO 3 and Pd/LaCoO 3 with NO 2 at 323 K resulted in the desorption of NO 2 , NO, N 2 O and N 2 (without O 2 ) below 700 K, while above 700 K, NO x desorption was predominantly in the form of NO + O 2 . Perovskite materials were found to be capable of activating N-O linkages typically at ca. 550 K (even in the absence of an external reducing agent) forming N 2 and N 2 O as direct NO x decomposition products. H 2 -pretreatment yielded a drastic boost in the NO oxidation and NO x adsorption of all samples, particularly for the Cobased systems. Presence of Pd further boosted the NO x uptake upon H 2 -pretreatment. Increase in the NO x adsorption of H 2 -pretreated LaCoO 3 and Pd/LaCoO 3 surfaces could be associated with the electronic changes (i.e. reduction of B-site cation), structural changes (surface reconstruction and SSA increase), reduction of the precious metal oxide (PdO) into metallic species (Pd), and the generation of oxygen defects on the perovskite. Mn-based systems were more resilient toward B-site reduction. Pd-addition suppressed the B-site reduction and preserved the ABO 3 perovskite structure.

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