Catalyst support materials with oxygen storage capacity (OSC) and method of making thereof
A new type of catalyst support with oxygen storage capacity (OSC) and methods of making the same are disclosed. The composition ratio is x(Ce 1−w Zr w O 2 ):yM:zL:(1−x−y−z)Al 2 O 3 , where Ce 1−w Zr w O 2 is the oxygen storage composition with stabilizer Zr0 2 , molar ratio (w) in the range of 0 to about 0.8, and a weight ratio (x) of about 0.05 to about 0.8; M is an interactive promoter for oxygen storage capacity with a weight ratio (y) of 0 to about 0.10; and L is a stabilizer for the support Al 2 O 3 with weight ratio (z) of from 0 to about 0.10. In some cases, M or L can act as both OSC promoter and thermal stabilizer. The weight percentage range of ceria-zirconia and other metal and rare earth oxides (x+y+z) is from about 5 to about 80% relative to total oxides. Combining platinum group metals (PGM) and adhesive with the catalyst supports, a new wash coat made therefrom is provided that comprises a mixture of catalyst support materials according to the relationship (a)RE-Ce—ZrO 2 +(3)CZMLA+(1−a−β)RE-Al 2 O 3 , where RE-Ce—ZrO 2 is a commercial OSC material of rare earth elements stabilized ceria zirconia having a weight ratio (a) ranging from 0 to about 0.7; CZMLA is the catalyst support material of the present disclosure having a weight ratio (β) ranging from about 0.2 to about 1 such that (α+β)<1; and RE-Al 2 0 3 is rare earth element stabilized alumina having a weight ratio equal to (1−α−β). The new wash coat made therefrom exhibits a lower activation temperature compared with traditional formulation of wash coat by at least 50° C. The new wash coat made therefrom also requires less RE-Ce—ZrO 2 oxide and/or less PGM in the formulation of emission control catalyst for gasoline and diesel engines.
1. A catalyst support material with oxygen storage capacity, the catalyst support material comprising:
ceria-zirconia; the ceria-zirconia having oxygen storage capacity;
an optional interactive promoter (M) for oxygen storage;
an aluminum oxide support; and
an optional stabilizer (L) for the aluminum oxide support;
wherein the catalyst support material (CZMLA) has the formula:
x (Ce 1-w Zr w O 2 ): y M: z L:(1- x - y - z )Al 2 O 3 ;
in which w is a molar ratio between 0 and about 0.8; and x, y, and z are weight ratios based on the total oxides in the CZMLA, such that x is within the range of about 0.05 to about 0.80, while y and z are within the range of 0 to about 0.10 with the remainder (1-x-y-z) being aluminum oxide;
wherein the support material comprises a catalyst support core powder having a formula:
x 1 (Ce 1-w Zr w O 2 ): y 1 M: z L:(1- x - y - z )Al 2 O 3
and a solid solution coated onto the core powder having a formula:
x 2 (Ce 1-w Zr w O 2 ): y 2 M
wherein x 2 =x−x 1 and y 2 =y−y 1 and in which 0.2≦x 1 /x≦0.8 and 0.2≦y 1 /y≦0.8.
2. The catalyst support material of claim 1 , in which the weight percentage range of ceria-zirconia, interactive promoter, and stabilizer (x+y+z) is from about 5 to about 80wt. % relative to the total oxides in the support material.
3. The catalyst support material of claim 1 , wherein M is chosen as one from an alkaline earth oxide, a transition metal oxide, and a rare earth metal oxide.
4. The catalyst support material of claim 1 , wherein L is chosen as one from an alkaline earth oxide, a transition metal oxide, and a rare earth metal oxide.
5. The catalyst support material of claim 1 , wherein M and L are compositionally different from one another.
6. The catalyst support material of claim 1 , wherein M and L are compositionally the same.
7. The catalyst support material of claim 1 , wherein the catalyst support material includes a solid solution (Ce, Zr)O 2 of cubic or tetragonal phase and an alumina of weak gamma phase.
8. catalyst support material of claim 1 , wherein the catalyst support material has a fresh specific surface area (SSA) of greater than 80 m 2 /g.
9. The catalyst support material of claim 1 , wherein the catalyst support material has a hydrothermal aged specific surface area (SSA) of greater than 45 m 2 /g.
10. The catalyst support material of claim 1 , wherein the catalyst support material has a particle size (D50) in the range of 1 to 100 microns.