Catalyst article having high local rhodium concentration
The present invention provides a catalyst article for treating exhaust gas comprising: a substrate comprising an inlet end and an outlet end with an axial length L; a first catalytic region comprising support material particles; at least some of the support material particles are rhodium-supporting support material particles having rhodium supported thereon at a concentration of from 0.001 to 3.5 wt. %, based on the weight of the rhodium-supporting support material particle; and the rhodium is present at a loading of up to 20 g/ft 3 relative to the first catalytic region.
1. A catalyst article for treating exhaust gas comprising:
a substrate comprising an inlet end and an outlet end with an axial length L;
a first catalytic region comprising support material particles;
at least some of the support material particles are rhodium-supporting support material particles having rhodium supported thereon at a concentration of from 0.001 to 3.5 wt. %, based on the weight of the rhodium-supporting support material particle;
the rhodium is present at a loading of up to 20 g/ft 3 relative to the first catalytic region; and
wherein at least some of the support material particles are non-supporting support material particles having essentially no rhodium supported thereon.
2. The catalyst article of claim 1 , wherein at least some of the support material particles are non-supporting support material particles having no rhodium supported thereon.
3. The catalyst article of claim 1 , wherein from 5 to 80% of the support material particles in the first catalyst region are rhodium-supporting support material particles.
4. The catalyst article of claim 1 , wherein the support material particles comprise alumina and/or a ceria-zirconia mixed oxide.
5. The catalyst article of claim 4 , wherein the alumina and/or a ceria-zirconia mixed oxide is doped.
6. The catalyst article of claim 4 , wherein the support material particles comprise a ceria-zirconia mixed oxide; and
wherein when a cross section of the first catalyst region of the catalyst article is subjected to area analysis by FE-EPMA under conditions of pixel (section) size of 0.34 μm×0.34 μm and number of measured pixels (sections) of 256×256, a characteristic X-ray intensity (α: cps) of the zirconium (Zr) and a characteristic X-ray intensity (β: cps) of the rhodium (Rh) are measured for each pixel, and the Pearson correlation coefficient calculated using the resulting α and β in each pixel is designated as R Zr/Rh , then the value of R Zr/Rh is from 0.15 to 0.48.
7. The catalyst article of claim 1 , wherein the rhodium is present at a loading of from 1 to 20 g/ft 3 relative to the first catalytic region.
8. The catalytic article of claim 1 , further comprising a second catalytic region.
9. The catalytic article of claim 8 , wherein the second catalytic region comprises a second PGM component.
10. The catalytic article of claim 9 , wherein the second catalytic region further comprises a second OSC material and/or a second inorganic oxide.
11. The catalytic article of claim 8 , further comprising a third catalytic region.
12. The catalytic article of claim 11 , wherein the third catalytic region comprises a third PGM component.
13. The catalytic article of claim 12 , wherein the third catalytic region further comprises a third OSC material and/or a third inorganic oxide.
14. The catalyst article of any preceding claim , wherein the first catalyst region further comprises platinum and/or palladium.
15. The catalyst article of claim 1 , wherein the substrate comprises a flow-through substrate.
16. An emission treatment system comprising the catalyst article of claim 1 .
17. A method of treating an exhaust gas, the method comprising:
providing the catalyst article of claim 1 ; and
contacting the catalyst article with an exhaust gas.
18. A method of manufacturing a catalyst article, the method comprising:
providing rhodium-supporting support material particles having rhodium supported thereon at a concentration of from 0.001 to 3.5 wt. %, based on the weight of the rhodium-supporting support material particle;
providing non-supporting support material particles having essentially no rhodium supported thereon;
forming a washcoat comprising the rhodium-supporting support material particles and the non-supporting support material particles; and
coating a substrate with the washcoat to provide a catalyst article wherein the rhodium is present at a loading of up to 20 g/ft 3 relative to the substrate.
19. The method of claim 18 , wherein providing rhodium-supporting support material particles comprises supporting rhodium on support material particles using incipient wetness impregnation.
20. The method of claim 19 , wherein providing rhodium-supporting support material particles further comprises drying and calcining the rhodium-supporting support material particles.