P
USRE44802EExpiredUtilityPatentIndex 49

Cerium-zirconium composite metal oxide

Assignee: KUNO OJIPriority: Sep 15, 2003Filed: Jun 10, 2010Granted: Mar 11, 2014
Est. expirySep 15, 2023(expired)· nominal 20-yr term from priority
Inventors:KUNO OJI
B01J 35/30B01D 2255/2066B01D 2255/2061B01D 2255/2063C01F 17/235C01P 2004/61C01P 2002/52B01J 37/036B01J 37/088B01D 2255/407B01D 2255/908B01D 2255/1021B01D 2255/1025B01D 2258/014B01D 2255/1023C01G 25/00C01P 2004/84B01J 21/066Y02T10/12B01J 23/10B01J 23/63B01J 37/0236B01D 53/945C01G 25/006C01P 2006/40
49
PatentIndex Score
1
Cited by
33
References
19
Claims

Abstract

A cerium-zirconium composite metal oxide having improved durability at high temperature and a stable oxygen storage capacity is provided. The cerium-zirconium composite metal oxide is characterized in that the total mole number of Ce and Zr is at least 85% based on the total mole number of metal in the composite metal oxide, a molar ratio Ce/Zr is within a range from 1/9 to 9/1, and an isoelectric point of the composite metal oxide is more than 3.5. Preferably, the molar ratio Ce/Zr is within a range from 3/7 to 7/3 and the isoelectric point is within a range from 3.8 to 5.0, and the cerium-zirconium composite metal oxide contains a rare earth metal (excluding Ce) in a concentration of less than 15% by mole based on the total mole number of metal in the composite metal oxide. Also the present invention provides a cerium-zirconium composite metal oxide, characterized in that CeO 2 forms a core surrounded by ZrO 2 .

Claims

exact text as granted — not AI-modified
What is claimed is: 
     
       1. A cerium-zirconium composite metal oxide, wherein a total mole number of Ce and Zr is at least 85% based on the total mole number of metal in the composite metal oxide, wherein a molar ratio Ce/Zr is within a range from 1/9 to 9/1, and wherein an isoelectric point of the composite metal oxide is more than 3.5. 
     
     
       2. The cerium-zirconium composite metal oxide according to  claim 1 , wherein the molar ratio Ce/Zr is within a range from 3/7 to 7/3 and the isoelectric point is within a range from 3.8 to 5.0. 
     
     
       3. The cerium-zirconium composite metal oxide according to  claim 2 , which contains rare earth metal (excluding Ce) in a concentration of less than 15% by mole based on the total mole number of metal in the composite metal oxide. 
     
     
       4. An exhaust gas purifying catalyst comprising the cerium-zirconium composite metal oxide of  claim 2  and a noble metal supported on the cerium-zirconium composite metal oxide. 
     
     
       5. A method for synthesizing the cerium-zirconium composite metal oxide of  claim 2 , which comprises mixing a ceria sol and a zirconium compound solution or a zirconia sol to prepare a suspension, and drying and firing the mixture. 
     
     
       6. The cerium-zirconium composite metal oxide according to  claim 1 , which contains rare earth metal (excluding Ce) in a concentration of less than 15% by mole based on the total mole number of metal in the composite metal oxide. 
     
     
       7. An exhaust gas purifying catalyst comprising the cerium-zirconium composite metal oxide of  claim 6  and a noble metal supported on the cerium-zirconium composite metal oxide. 
     
     
       8. A method for synthesizing the cerium-zirconium composite metal oxide of  claim 6 , which comprises mixing a ceria sol and a zirconium compound solution or a zirconia sol to prepare a suspension, and drying and firing the mixture. 
     
     
       9. An exhaust gas purifying catalyst comprising the cerium-zirconium composite metal oxide of  claim 1  and a noble metal supported on the cerium-zirconium composite metal oxide. 
     
     
       10. A method for synthesizing the cerium-zirconium composite metal oxide of  claim 1 , which comprises mixing a ceria sol and a zirconium compound solution or a zirconia sol to prepare a suspension, and drying and firing the mixture. 
     
     
       11. A cerium-zirconium composite metal oxide, wherein a total mole number of Ce and Zr is at least 85% based on the total mole number of metal in the composite metal oxide and wherein CeO 2  forms a core surrounded by ZrO 2 , and wherein an isoelectric point of the composite metal oxide is more than 3.5. 
     
     
       12. The cerium-zirconium composite metal oxide according to  claim 11 , wherein the CeO 2  core has a diameter within a range from 5 to 20 nm. 
     
     
       13. An exhaust gas purifying catalyst comprising the cerium-zirconium composite metal oxide of  claim 12  and a noble metal supported on the cerium-zirconium composite metal oxide. 
     
     
       14. An exhaust gas purifying catalyst comprising the cerium-zirconium composite metal oxide of  claim 11  and a noble metal supported on the cerium-zirconium composite metal oxide. 
     
     
       15. A method for synthesizing the cerium-zirconium composite metal oxide of  claim 11 , which comprises mixing a ceria sol and a zirconium compound solution or a zirconia sol to prepare a suspension, and drying and firing the mixture. 
     
     
       16. A cerium-zirconium composite metal oxide,
 wherein a total mole number of Ce and Zr is at least 85% based on the total mole number of metal in the cerium-zirconium composite metal oxide, and   wherein an isoelectric point of the cerium-zirconium composite metal oxide is more than 3.5.    
     
     
       17. The cerium-zirconium composite metal oxide according to claim 16, wherein the cerium-zirconium composite metal oxide is comprised mainly of ZrO 2  outside, and mainly of CeO 2  inside.  
     
     
       18. The cerium-zirconium composite metal oxide according to claim 17, wherein the CeO 2  has a spherical shape.  
     
     
       19. The cerium-zirconium composite metal oxide according to claim 17, wherein the cerium-zirconium composite metal oxide has a spherical shape.

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