Phase Analysis and Oxygen Storage Capacity of Ceria-Lanthana-Based TWC Promoters Prepared by Sol–Gel Routes
✍ Scribed by Francesca Deganello; Antonino Martorana
- Publisher
- Elsevier Science
- Year
- 2002
- Tongue
- English
- Weight
- 398 KB
- Volume
- 163
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
Ceria+lanthana-based promoters of three-way catalysts are synthesized by two di4erent sol+gel routes, involving nitrate precursors. The oxygen uptake ability of these compounds is measured by O 2 chemisorption. The speci5c surface area is determined by N 2 adsorption (BET). X-ray di4raction data are analyzed by Rietveld re5nement, demonstrating that lanthanum forms solid solution with CeO 2 ; its total amount in ceria depends on the competitive formation of La+Al mixed oxides and on the synthetic method. The O 2 uptake ability is essentially determined by the La content in the ceria+lanthana solid solution, while it is independent on the surface area and on the CeO 2 particle size. The O 2 uptake ability increases with the La:Ce relative amount in the ceria+lanthana solid solution, but decreases beyond a La:Ce molar ratio greater than +0.18. This behavior is ascribed to the stable association of vacancy+vacancy or vacancy+ dopant cation.
2002 Elsevier Science (USA)