Effects of calcination temperature on the stability of CePO4 detected in vehicle-aged commercial three-way catalysts

Larese, C.; Galisteo, F. Cabello; Granados, M. Lòpez; Mariscal, R.; Fierro, J.L.G.; Lambrou, P.S.; Efstathiou, Angelos M.

doi:10.1016/j.apcatb.2003.09.020

Cited by 42 publications

(23 citation statements)

References 56 publications

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“…1 show that the samples synthesized have the typical AFI structures with an extremely intense (100) line at about 7.4°and a high crystallinity. No impure crystalline phase was detected, which reveals that Ln may be highly dispersed on the extra framework or Ln atoms partially substitute aluminium atoms in the framework by forming a new Ln-AlPO structure [30]. It was found that all reflections in the XRD patterns of Ln-containing samples shifted to lower positions, as compared to the pure AlPO-5 molecular sieve.…”

Section: Powder X-ray Diffractionmentioning

confidence: 96%

Selective Oxidation of Cyclohexane by Oxygen in a Solvent-Free System over Lanthanide-Containing AlPO-5

Li¹,

Xu²,

Shi³

et al. 2010

Catal Lett

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Ln-containing AlPO-5 (Ln = La, Ce, Sm, Dy, Y, Gd) were synthesized hydrothermally in the presence of HF, and characterized by XRD, UV-vis, SEM, N 2 adsorption/desorption, FT-IR, solid state 27 Al MAS NMR and ICP-AES techniques. The results showed that all the samples had good crystallinity and high specific area. Isomorphous substitution of Ln ions for Al ?3 occurred. The lanthanide ions were incorporated into the frameworks or were highly dispersed on extra frameworks of the samples. The newly synthesized catalysts all were efficient for the oxidation of cyclohexane in a solvent-free system, especially Gd-AlPO-5. Near 13% conversion of cyclohexane were achieved on the catalyst Gd(60)-AlPO-5 with Al/Gd of 60 under the conditions of 0.5 MPa O 2 , 413 K and 4 h reaction. The total selectivity to cyclohexanol and cyclohexanone was up to 92%. In addition, the catalyst Gd(60)-AlPO-5 was recyclable for the titled reaction system.

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Section: Powder X-ray Diffractionmentioning

confidence: 96%

Selective Oxidation of Cyclohexane by Oxygen in a Solvent-Free System over Lanthanide-Containing AlPO-5

Li¹,

Xu²,

Shi³

et al. 2010

Catal Lett

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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: 92%

“…Surface enrichment in ceria has been also observed upon annealing [18].Thus, it is reasonable to state that surface enrichment in Ceand Ba-species would favor their removal through dissolution in the acid solution. In addition, CePO 4 was found to predominate in the form of a crust at the surface/subsurface of CeO 2 and Ce x Zr 1)x O 2 solid crystals [9]. Thus, it could be said that cerium removal would probably correspond to a large extent to that present in CePO 4 (XRD results).…”

Section: Icp-aes Analysesmentioning

confidence: 95%

“…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%

“…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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Regeneration of Aged Commercial Three-Way Catalytic Converters

Christou

Gåsste²,

Karlsson³

et al. 2009

Top Catal

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The present work demonstrates for the first time that rejuvenation of the catalytic activity of full-scale aged commercial three-way catalytic (TWC) converters is feasible after treatment with weak oxalic acid solution (0.1 M). Up to 50% reduction in CO, 75% in NO x and 32% in HC emissions was attained under warm engine driving conditions following regeneration of three aged TWC converters with 42,500, 156,000 and 165,000 km mileage. Efforts to expand the durability of aged commercial TWC converters installed in gasoline-driven cars after applying specific treatments with weak oxalic acid-based solutions appear to be a very promising starting point in recovering to a very large degree their performance.

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Effects of calcination temperature on the stability of CePO4 detected in vehicle-aged commercial three-way catalysts

Cited by 42 publications

References 56 publications

Selective Oxidation of Cyclohexane by Oxygen in a Solvent-Free System over Lanthanide-Containing AlPO-5

Selective Oxidation of Cyclohexane by Oxygen in a Solvent-Free System over Lanthanide-Containing AlPO-5

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

Regeneration of Aged Commercial Three-Way Catalytic Converters

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