Titania-doped zirconia as platinum group metal support in catalysts for treatment of combustion engine exhausts streams
Composites of mixed metal oxides for an exhaust gas purifying catalyst comprise the following co-precipitated materials by weight of the composite: zirconia in an amount in the range of 55-99%; titania in an amount in the range of 1-25%; a promoter and/or a stabilizer in an amount in the range of 0-20%. These composites are effective as supports for platinum group metals (PGMs), in particular rhodium.
1. A composite of mixed metal oxides for an exhaust gas purifying catalyst, the composite comprising, by weight of the composite:
zirconia in an amount in the range of 55-99%;
titania in an amount in the range of 1-25%;
a promoter and/or a stabilizer in an amount in the range of 0-20%,
wherein the composite is effective as a support for a platinum group metal (PGM).
2. The composite of claim 1 , wherein the promoter comprises a rare earth metal oxide and is present in an amount in the range of 0.1-20%.
3. The composite of claim 1 , wherein the promoter comprises lanthana, tungsta, ceria, neodymia, gadolinia, yttria, praseodymia, samaria, hafnia, or combinations thereof.
4. The composite of claim 1 , wherein the stabilizer is present in an amount in the range of 0.1-5% and comprises silicon oxide.
5. The composite of claim 1 , wherein the stabilizer is present in an amount in the range of 0.1-10% and comprises an alkaline earth metal oxide.
6. The composite of claim 1 , wherein the composite has a ceria content of 20% or less by weight.
7. The composite of claim 1 , wherein the zirconia, the titania, and the promoter and/or the stabilizer are co-precipitated.
8. The composite of claim 1 , wherein the zirconia and the promoters and/or stabilizers are co-precipitated and the titania is impregnated from a titania precursor.
9. The composite of claim 8 , wherein the titania precursor comprises a titanium salt, a titanium-containing organic complex, a titania sol, or colloidal titania.
10. The composite of claim 1 having a surface area in the range of 10-40 m 2 /g after oven aging for 12 hours at 1000° C.
11. A catalyst composite for treatment of an exhaust stream of a combustion engine, the catalyst composite comprising a catalytic material on a carrier, the catalytic material comprising: a platinum group metal (PGM) supported on the composite of mixed metal oxides of claim 1 .
12. The catalyst composite of claim 11 wherein:
the mixed metal oxide composite comprises zirconia in an amount in the range of 55-90%;
titania in an amount in the range of 5-25%; a promoter comprising lanthanum oxide in an amount in the range of 5-20%; and
the platinum group metal comprises rhodium.
13. The catalyst composite of claim 11 comprising a rhodium in an amount in the range of 0.1 to 5% by weight.
14. The catalyst composite of claim 13 comprising 0.25% by weight rhodium that after aging at 950° C. is effective to provide conversion of 50% or more of carbon monoxide, nitrogen oxides, and hydrogen; and conversion of 10% or more of hydrocarbons at lambdas in the range of 0.98 to 1.02 during a lean-rich lambda sweep test at 300° C.
15. The catalyst composite of claim 11 comprising a titania to rhodium weight ratio in the range of 5 to 250.
16. A system for treatment of an exhaust stream including hydrocarbons, carbon monoxide, and nitrogen oxides of an internal combustion engine, the system comprising:
an exhaust conduit in fluid communication with the internal combustion engine via an exhaust manifold; and
the catalyst composite according to claim 11 .
17. A method for treating exhaust gases comprising contacting a gaseous stream comprising hydrocarbons, carbon monoxide, and nitrogen oxides with the catalyst composite according to claim 11 .
18. The method of claim 17 , wherein:
the mixed metal oxide composite comprises, by weight: zirconia in an amount in the range of 55-90%; titania in an amount in the range of 5-25%; a promoter comprising lanthanum oxide in an amount in the range of 5-20% and the platinum group metal comprises rhodium in an amount ranging from 0.1 to 5% by weight; and
after aging at 950° C., the catalyst composite is effective to provide conversion of 50% or more of carbon monoxide, nitrogen oxides, and hydrogen; and conversion of 10% or more of hydrocarbons at lambdas in the range of 0.98 to 1.02 during a lean-rich lambda sweep test at 300° C.
19. The composite of claim 1 , further comprising a platinum group metal (PGM) supported on the composite of mixed metal oxides.