Effect of mileage on the deactivation of vehicle-aged three-way catalysts

Granados, M. Lòpez; Larese, C.; Galisteo, F. Cabello; Mariscal, R.; Fierro, J. L. G.; Fernández-Ruiz, Ramón; Sanguino, R.; Luna, Mauricio López

doi:10.1016/j.cattod.2005.07.064

Cited by 44 publications

(27 citation statements)

References 37 publications

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“…Based on XPS results [11], Ce and Zr surface concentrations were found to significantly increase only after oxalic acid washing. These results imply that the latter procedure largely uncovers the TWC washcoat surface through the removal of most of P-containing overlayer which was reported to be constituted of Zn, Ca, Mg, Ce and Al phosphates [4][5][6]9]. [9].…”

Section: Icp-aes Analysesmentioning

confidence: 89%

“…The increase in the number of small pores that become larger due to the applied acid washing could by excluded considering the fact that formation of larger pores would generally lead to lower surface area. The view that the main quantities of contaminants accumulated on the washcoat surface, whereas accumulation inside the pores of washcoat was considerably lower, and, therefore, fouling (closing of pores) was the main deactivation mechanism, is widely accepted [4][5][6][7][8][9]. CePO 4 and AlPO 4 were also reported to be formed around the Ce x Zr 1)x O 2 and c-Al 2 O 3 particles as a crust (washcoat-pores blocking) [5,6].…”

Section: Bet Surface Area and Pore Size Distribution Measurementsmentioning

confidence: 96%

“…The reflections at 20.2 and 22.2 o are assigned to a mixture of MgZn 2 (PO 4 ) 2 (h) and CaZn 2 (PO 4 ) 2 (o) [4]. The broad peak centered at 22.2 o provides also indication for the presence of orthorhombic Zn 2 P 2 O 7 and tridymitetype AlPO 4 [4,5]. Reflections at 25.6, 27.0, 29.8, 31.0 and 34.3 o are due to the presence of CePO 4 (r) [6,9].…”

Section: Icp-aes Analysesmentioning

confidence: 99%

“…The removal of large amounts of P-containing compounds from the aged TWC, known to severely deteriorate the catalytic and oxygen storage and release properties of TWC [5,9], after applying the oxalic acid washing procedure is shown to significantly improve the activity of the aged TWC towards CO and NO conversions. Results on the efficiency of nitrilotriacetic (NTA) and EDTA weak organic acid solutions on the removal of P from the same aged TWC are also presented.…”

Section: Introductionmentioning

confidence: 97%

“…Hydrometallurgical procedures employed for recovering PGM use highly aggressive and corrosive reagents for complete dissolution of TWC which produce large quantities of liquid and solid wastes. Technical challenges encountered in these processes also involve the presence of various contaminants accumulated on the TWC upon usage, such as P, Ca, Zn, Mg, Pb and S, typical oil-and fuel-derived contaminants, and Fe, Cu, Ni and Cr originating from the engine and exhaust system construction materials [2,[4][5][6][7]. Chemical poisoning and high-temperature aging comprise the main causes of TWC deactivation [4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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Efficient In-Situ Regeneration Method of the Catalytic Activity of Aged TWC

Christou

Efstathiou

2007

Top Catal

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The expansion of durability of deactivated ''three-way'' catalysts (TWCs) used in gasoline-driven cars by applying efficient, economically viable and environmentally friendly methods for the in situ regeneration of their performance to acceptable levels was investigated. New experimental results on the use of a weak oxalic acid washing solution as a means of an efficient regeneration method of a severely aged (83,000 km mileage) commercial TWC are presented. Oxalic acid is shown to be the most efficient extracting agent of phosphorus, a severe poison of TWCs, among acetic acid, citric acid, NTA and EDTA investigated. X-ray diffraction studies provided strong evidence that washing of the aged TWC results in the removal of CePO 4 , AlPO 4 and (Mg,Ca,Zn) 3 (PO 4 ) 2 type phosphates leading to a significant increase of BET area and pore volume, as well as of CO and NO conversions (catalytic activity tests). The latter is strongly related with the increase in the number of active catalytic sites, as illustrated by in situ DRIFTS studies, after opening closed pores and uncovering additional catalyst surface.

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Section: Icp-aes Analysesmentioning

confidence: 89%

Section: Bet Surface Area and Pore Size Distribution Measurementsmentioning

confidence: 96%

Section: Icp-aes Analysesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Efficient In-Situ Regeneration Method of the Catalytic Activity of Aged TWC

Christou

Efstathiou

2007

Top Catal

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Catalytic Properties of Nanometric Metal Overlayers with Two‐Dimensional Structures

Yoshida,

Machida

2023

ChemCatChem

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Although most of the currently used solid catalysts possess a three‐dimensional structure of nanoparticles dispersed on a porous support, the nanoparticle structure should not be considered the optimal structure for all catalytic reactions due to some disadvantages such as thermal instability and catalyst poisoning. Herein, we present the unique catalytic performance of a two‐dimensional metal foil‐supported nanometric Rh thin film, referred to as the “Rh overlayer”, for a catalytic CO−NO reaction and a stoichiometric three‐way catalytic reaction under practical conditions. The extremely high turnover frequency for NO reduction using two‐dimensional Rh is a key to understanding this phenomenon, the detailed mechanism of which can be explained by theoretical calculations.

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Rh Nanoparticle Anchoring on Metal Phosphates: Fundamental Aspects and Practical Impacts on Catalysis

Machida

2016

The Chemical Record

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Metal phosphates stabilize Rh nanoparticles on their surface via Rh-O-P bonds, in contrast to the Rh-O-M bonds formed on metal oxides (MO ). The local structure, electronic structure, and redox properties of Rh nanoparticles anchored on metal phosphates, and their practical impacts on catalysis, are reviewed based on recent publications from the author's research group. Because of the covalency of the Rh-O-P bond, Rh oxide is readily reduced to metallic Rh having a higher catalytic activity, whereas Rh oxide on metal oxide supports is more difficult to reduce with an increase of the anchoring strength. Furthermore, Rh metal shows a higher tolerance to reoxidation when supported on metal phosphates because the Rh-O-P bond is preserved under reducing atmospheres. The electron deficiency of Rh metal is another feature that affects its catalytic properties, and the extent of the electron deficiency can be tuned by replacing the metal in the metal phosphate with one of higher basicity. Further impacts on practical performance (thermal stability, poisoning stability, and lean NO purification) in automobile catalyst applications are also described.

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Effect of mileage on the deactivation of vehicle-aged three-way catalysts

Cited by 44 publications

References 37 publications

Efficient In-Situ Regeneration Method of the Catalytic Activity of Aged TWC

Efficient In-Situ Regeneration Method of the Catalytic Activity of Aged TWC

Catalytic Properties of Nanometric Metal Overlayers with Two‐Dimensional Structures

Rh Nanoparticle Anchoring on Metal Phosphates: Fundamental Aspects and Practical Impacts on Catalysis

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