Exhaust gas purifying catalyst and production method therefor, and exhaust gas purification device using same

Patent metadata

Field	Value
Publication number	US-11179701-B2
Application number	US-201716086869-A
Country	US
Kind code	B2
Filing date	Mar 9, 2017
Priority date	Mar 25, 2016
Publication date	Nov 23, 2021
Grant date	Nov 23, 2021

Abstract

An exhaust gas purifying catalyst having first carrier particles, second carrier particles, and precious metal catalyst particles supported on the first and second carrier particles, wherein: the first carrier particles contain ceria, zirconia, and a rare-earth oxide other than ceria; the second carrier particles contain a rare-earth oxide other than ceria, and may contain ceria and zirconia; the contained proportion of ceria and zirconia in the first carrier particles is higher than the contained proportion of ceria and zirconia in the second carrier particles; the contained proportion of the rare-earth oxide in the second carrier particles is higher than the contained proportion of the rare-earth oxide in the first carrier particles; and the contained proportion of ceria in the first carrier particles is 45 wt % or less, while the precious metal catalyst particles include rhodium particles.

First claim

The invention claimed is:

1. An exhaust gas purifying catalyst having a first carrier particle, a second carrier particle, and a precious metal catalyst particle supported on the first carrier particle and the second carrier particle; wherein,
the first carrier particle contains 3.0% by weight or more of ceria, 50% by weight to 95% by weight of zirconia and 1.0% by weight to less than 20% by weight of a rare earth oxide other than ceria,
the second carrier particle contains 20% by weight to 60% by weight of a rare earth oxide other than ceria and optionally contains 0.0% by weight to 40% by weight of ceria and 0.0% by weight to 40% by weight of zirconia,
the total content of ceria and zirconia of the first carrier particle is higher than the total content of ceria and zirconia of the second carrier particle,
the content of the rare earth oxide other than ceria of the second carrier particle is higher than the content of the rare earth oxide other than ceria of the first carrier particle,
the content of ceria of the first carrier particle is 45% by weight or less, and
the precious metal catalyst particle comprises a rhodium particle.

2. The exhaust gas purifying catalyst according to claim 1 , wherein the content of the rare earth oxide other than ceria of the first carrier particle is less than 20% by weight, and the content of the rare earth oxide other than ceria of the second carrier particle is 20% by weight or more.

3. The exhaust gas purifying catalyst according to claim 2 , wherein, in the case of observing the first carrier particle and the second carrier particle with a scanning transmission electron microscope, the ratio of the projected area of the second carrier particle to the projected area of the first carrier particle (area of second carrier particle/area of first carrier particle) is within the range of 0.050 to 0.100.

4. The exhaust gas purifying catalyst according to claim 1 , wherein the first carrier particle and the second carrier particle are ceria-zirconia solid solutions containing a rare earth oxide other than ceria, and
the rare earth oxide other than ceria of the first carrier particle and the rare earth oxide other than ceria of the second carrier particle are oxides of at least one rare earth element selected from the group consisting of yttrium, lanthanum, praseodymium, neodymium and samarium.

5. The exhaust gas purifying catalyst according to claim 1 , wherein the first carrier particle contains 50% by weight to 75% by weight of zirconia, 20% by weight to 40% by weight of ceria and 1.0% by weight to less than 20% by weight of a rare earth oxide other than ceria, and
the second carrier particle contains 0.0% by weight to 40% by weight of zirconia, 25% by weight to 40% by weight of ceria, and 20% by weight to 60% by weight of a rare earth oxide other than ceria.

6. The exhaust gas purifying catalyst according to claim 1 , wherein the mean particle diameters of the first carrier particle and the second carrier particle as measured with a scanning transmission electron microscope are 0.50 μm to 100 μm and 0.50 μm to 5 μm, respectively.

7. The exhaust gas purifying catalyst according to claim 1 , wherein the precious metal catalyst particle further contains platinum particles and/or palladium particles.

8. The exhaust gas purifying catalyst according to claim 1 , wherein the locations of the rhodium particle and the locations of the second carrier particle coincide at a correlation coefficient of 65.0% or more when element mapping has been carried out by energy dispersive X-ray analysis using a scanning transmission electron microscope, the correlation coefficient being calculated according to the following formula:

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Assignees

• Cataler Corp

Inventors

• Sakurada Yu
• Harada Takahiro
• NAKASHIMA Ryota

Classifications

• B01J2235/15

  X-ray diffraction · CPC title

• B01J2235/30

  Scanning electron microscopy; Transmission electron microscopy · CPC title

• B01J2235/00

  Indexing scheme associated with group B01J35/00, related to the analysis techniques used to determine the catalysts form or properties · CPC title

• B01J35/393

  Metal or metal oxide crystallite size · CPC title

• B01J23/63 Primary

  with rare earths or actinides · CPC title