Three-way catalyst for lean operating engines

Claim 2

An improved three-way catalyst suitable for simultaneously oxidizing both gaseous hydrocarbons and carbon monoxide while reducing nitrogen oxides said catalyst comprising a washcoat comprising rhodium dispersed on particles of gamma alumina, an amount of a rare earth oxide effective for enhancing oxidation of carbon monoxide and a second platinum group metal selected from the group consisting of platinum, palladium and mixtures thereof, the second platinum group metal being dispersed on particles selected from the group consisting of particles of rare earth oxide, particles of alumina, particles of gamma alumina stabilized with rare earth oxide and mixtures thereof; wherin, the improvement comprises a substantial portion of the rhodium being dispersed on particles which are substantially rare earth oxide free.

Claim 3

The catalyst of claim 1 wherein the rhodium is incorporated therein at a concentration of about 0.1 g/ft 3 to be about 15 g/ft 3 and the second platinum group metal is incorporated therein at a concentration of about 0.5 g/ft 3 to about 150 g/ft 3 based on the total volume of the catalyst.

Claim 4

The catalyst of claim 1, wherein the amount of rare earth oxide is at least about 0.5% of the weight of the particles upon which a platinum group metal is dispersed.

Claim 5

The catalyst of claim 1 wherein the second platinum group metal is dispersed on particles of gamma alumina.

Claim 6

The catalyst of claim 1 wherein the second platinum group metal is dispersed on alumina particles having a rare earth oxide combined therewith.

Claim 7

The catalyst of claim 5 wherein the rare earth metal oxide is combined with the alumina particles at a concentration of about 0.1 to about 25 percent by weight based on the weight of the combined alumina.

Claim 8

The catalyst of claim 6 wherein the rare earth metal oxide is cerium oxide.

Claim 9

The catalyst of claim 1 wherein the second platinum group metal is dispersed on particles of rare earth oxide.

Claim 10

The catalyst of claim 8 wherein the rare earth oxide is cerium oxide.

Claim 11

The catalyst of claim 1 wherein the rhodium is dispersed on alumina particles having an alkaline earth oxide combined therewith.

Claim 12

The catalyst of claim 10 wherein the second platinum group metal is dispersed on alumina particles having rare earth oxide combined therewith.

Claim 13

The catalyst of claim 10 wherein the second platinum group metal is dispersed on alumina particles having cerium oxide combined therewith.

Claim 14

The catalyst of claim 12 wherein the alkaline earth oxide is barium oxide.

Claim 15

The catalyst of claim 10 wherein the alkaline earth oxide is barium oxide.

Claim 16

The catalyst of claim 10 wherein the second platinum group metal is dispersed on alumina particles having an alkaline earth oxide combined therewith.

Claim 17

The catalyst of claim 15 wherein the rare earth oxide comprises at least ten percent bulk ceria by weight of the particles upon which a platinum group metal is dispersed on the alkaline earth oxide is barium oxide.

Claim 18

The catalyst of claim 10 wherein the alkaline earth oxide is combined with alumina at a concentration of about 0.1 to about 3.0 percent by weight of the combined alumina.

Claim 19

The catalyst of claim 1 wherein the rhodium is dispersed on gamma alumina particles having an alkaline earth oxide combined therewith.

Claim 20

The catalyst of claim 18 wherein the alkaline earth oxide is barium oxide.

Claim 21

The catalyst of claim 18 wherein the alkaline earth oxide is combined with the alumina particles at a concentration of about 0.1 to about 3.0 percent by weight based on the combined weight of the alumina and alkaline earth metal oxide.

Claim 22

The catalyst of claim 1, wherein the rare earth oxide and the particles bearing the dispersed rhodium and second platinum group metal are distributed on a monolithic ceramic carrier.

Claim 23

The catalyst of claim 1 wherein there is additionally incorporated in the catalyst a promoter for oxidation and reduction reactions, the promoter being selected from the group consisting of manganese, vanadium, copper, iron, cobalt, chromium, zirconium, nickel and oxides thereof.

Claim 24

The catalyst of claim 22 wherein the promoter is incorporated therein at a concentration of about 0.1 to about 25 percent by weight based on the weight of the particles upon which a platinum group metal is dispersed.

Claim 25

The catalyst of claim 1, wherein the rare earth oxide is present in an amount of at least about 3% by weight of the particles upon which a platinum group metal is dispersed.

Claim 26

The catalyst of claim 1, wherein the rare earth oxide is present in an amount of at least about 5% by weight of the particles upon which a platinum group metal is dispersed.

Claim 27

The catalyst of claim 1, wherein the rare earth oxide is present in an amount of at least about 10% by weight of the particles upon which a platinum group metal is dispersed.

Claim 28

The catalyst of claim 1, wherein the rare earth oxide is present in an amount of at least about 15% by weight of the particles upon which a platinum group metal is dispersed.

Claim 29

A three-way catalyst comprising rhodium, an amount of rare earth oxide effective for enhancing oxidation of carbon monoxide and a second platinum group metal selected from the group consisting of platinum, palladium and mixtures thereof, said catalyst being suitable for simultaneously oxidizing both gaseous hydrocarbons and carbon monoxide, while reducing nitrogen oxides and having been prepared by the method comprising the steps of impregnating substantially rare earth oxide free gamma alumina support particles with a first liquid admixture containing a first platinum group metal compound selected from the group consisting of rhodium compounds, admixtures of rhodium compounds with palladium compounds, and admixtures of rhodium compounds with platinum and palladium compounds; impregnating support particles with another liquid admixture containing a second platinum group metal compound, and said support particles being selected from the group consisting of particles of rare earth oxide, particles of alumina and particles of gamma alumina stabilized with rare earth oxide and mixtures thereof, said second platinum group metal compound being selected from the group consisting of platinum compounds, palladium compounds and admixtures of platinum and palladium compounds, and combining the particles impregnated with said first platinum group metal compound with the particles impregnated with said second platinum group metal compound; drying and calcining.

Claim 30

A three-way catalyst comprising rhodium, an amount of rare earth oxide effective for enhancing oxidation of carbon monoxide and a second platinum group metal selected from the group consisting of platinum, palladium and mixtures thereof, said catalyst being suitable for simultaneously oxidizing both gaseous hydrocarbons and carbon monoxide, while reducing nitrogen oxides and having been prepared by the method comprising the steps of impregnating substantially rare earth oxide free gamma alumina support particles with a first liquid admixture containing a first platinum group metal compound selected from the group consisting of rhodium compounds, admixtures of rhodium compounds with palladium compounds, and admixtures of rhodium compounds with platinum and palladium compounds; impregnating support particles with another liquid admixture containing a second platinum group metal compound, and said support particles being selected from the group consisting of particles of rare earth oxide, particles of alumina and particles of gamma alumina stabilized with rare earth oxide and mixtures thereof, said second platinum group metal compound being selected from the group consisting of platinum compounds, palladium compounds and admixtures of platinum and palladium compounds, and combining the particles impregnated with said first platinum group metal compound with the particles impregnated with said second platinum group metal compound; drying and calcining.

Claim 31

The three-way catalyst of claim 28 wherein said support particles impregnated with said second platinum group metal compound are particles selected from the group consisting of particles of alumina and particles of gamma alumina stabilized with rare earth oxide, wherein the process by which said three-way catalyst is prepared, comprises the further step of combining particles of rare earth oxide with the particles impregnated with said first platinum group metal compound and the particles impregnated with said second group metal compound.

Claim 32

The catalyst of claim 28 wherein the process by which said catalyst is prepared comprises the additional steps of suspending the impregnated alumina particles and the rare earth oxide in a liquid to form a slurry, contacting a monolithic carrier with the slurry, and heating the carrier at a temperature which is sufficiently high to provide on the carrier a composite of the rhodium, second platinum group metal, rare earth oxide and alumina particles.

Claim 33

The catalyst of claim 30 wherein the amount of rhodium impregnated on the alumina particles is from about 0.1 g/ft 3 to about 15 g/ft 3 and the second platinum group metal compound is impregnated on the second alumina particles at a concentration sufficient to provide a platinum group metal concentration of from about 0.5 g/ft 3 to about 150 g/ft 3 based on total volume of the catalyst.

Claim 34

The catalyst of claim 30 wherein the alumina upon which said first platinum group metal compound is impregnated is gamma alumina.

Claim 35

The catalyst of claim 30 wherein the second platinum group metal compound is dispersed on particles of rare earth oxide.

Claim 36

The catalyst of claim 33 wherein said rare earth oxide is cerium oxide.

Claim 37

The catalyst of claim 29 wherein the alumina upon which said second platinum group metal compound is dispersed has an alkaline earth oxide combined therewith.

Claim 38

The catalyst of claim 35 wherein the alkaline earth oxide is barium oxide.

Claim 39

The catalyst of claim 28 wherein the second platinum group metal is impregnated on alumina particles having a rare earth metal oxide combined therewith.

Claim 40

The catalyst of claim 37 wherein the rare earth metal oxide is combined with the alumina particles at a concentration of about 0.1 to about 25 percent by weight based on the weight of the combined alumina.

Claim 41

The catalyst of claim 38 wherein the rare earth metal oxide is cerium oxide.

Claim 42

The catalyst of claim 28 wherein the second platinum group metal compound is impregnated on alumina particles having an alkaline earth oxide combined therewith.

Claim 43

The catalyst of claim 40 wherein the alkaline earth oxide is barium oxide and wherein the rare earth comprises at least about 10% bulk ceria by weight of the particles upon which a platinum group metal is dispersed.

Claim 44

The catalyst of claim 40 wherein the concentration at which said alkaline earth oxide is combined with the alumina particles upon which said second platinum group metal compound is impregnated is from about 0.1 to about 3.0 percent by weight based on the weight of the combined alumina.

Claim 45

The catalyst of claim 42 wherein the rare earth metal is cerium.

Claim 46

The catalyst of claim 29 wherein the rhodium is impregnated on the alumina particles having an alkaline earth oxide combined therewith.

Claim 47

The catalyst of claim 44 wherein the alkaline earth oxide is barium oxide.

Claim 48

The catalyst of claim 44 wherein the akaline earth oxide is combined with the alumina particles at a concentration of about 0.1 to about 3.0 percent by weight based on the combined weight of the alumina particles and alkaline earth metal oxide.

Claim 49

The catalyst of claim 28 wherein there is additionally a promoter for oxidation and reduction reactions, the promoter being selected from the group consisting of manganese, vanadium, copper, iron, cobalt, chromium, zirconium, nickel and oxides thereof is combined with the particles impregnated with said first platinum group metal compound and the particles impregnated with said second platinum group metal compound.

Claim 50

The catalyst of claim 47 wherein the promoter is combined with the particles impregnated with said first platinum group metal compound and the particles impregnated with said second platinum group metal compound at a concentration of about 0.1 to about 25 percent by weight based on the weight of the particles upon which a platinum group metal is dispersed.

Claim 51

The catalyst of claim 28 wherein ceria particles are additionally combined with the particles impregnated with said first platinum group metal compound and the particles impregnated with said second platinum group metal compound.

Claim 52

The catalyst of claim 28, wherein the rare earth oxide is present in an amount of at least about 3% by weight of the particles upon which a platinum group metal is dispersed.

Claim 53

The catalyst of claim 28, wherein the rare earth oxide is present in an amount of at least about 5% by weight of the particles upon which a platinum group metal is dispersed.

Claim 54

The catalyst of claim 28, wherein the rare earth oxide is present in an amount of at least about 10% by weight of the particles upon which a platinum group metal is dispersed.

Claim 55

The catalyst of claim 28, wherein the rare earth oxide is present in an amount of at least about 15% by weight of the particles upon which a platinum group metal is dispersed.