Stabilized and doubly promoted platinum group metal catalysts for emission control and method of making same

Claim 1

A catalyst suitable for use as a catalyst for auto emission control comprising an alumina support with components deposited thereon consisting essentially of lanthana as a stabilizer in an amount of about 1 to 10% by weight expressed as La 2 O 3 which is either in the form of lanthana only or in the form of lanthana-rich rare earth oxides where the La 2 O 3 is at least 50% by weight of the total rare earth oxides, 1-20% by weight of ceria as a promoter, at least 0.5 to about 5% by weight of an alkali metal oxide as a promoter, and a catalytically-effective amount of one or more platinum group metals.

Claim 10

A method of making a catalyst which is suitable for use as a three-way catalyst for auto emission comprising the steps of (a) impregnating an alumina support which has been heated to at least 300° C. with a solution containing a lanthanum salt which is either in the form of lanthanum salt only or in the form of lanthanum-rich rare earth salts, which upon calcination gives rare earth oxides where La 2 O 3 is at least 50% by weight of the total rare earth oxides; (b) heating the impregnated support to at least decompose the lanthanum salt to obtain a lanthana impregnated support; (c) applying promoters and one or more platinum group metals by either A. (1) impregnating the lanthana-impregnated alumina support from step (b) with a soluble cerium salt solution; (2) heating the impregnated support to at least decompose the cerium salt to obtain a lanthana-ceria impregnated support; and (3) impregnating the lanthana-ceria impregnated support with solutions bearing one or more platinum group metals and at least one alkali metal; or B. (1) impregnating the lanthana impregnated support from step (b) with a solution containing a soluble cerium salt and a lithium salt; (2) heating the impregnated support to at least decompose the cerium and lithium salts to obtain a lanthana-ceria-lithia impregnated support; and (3) impregnating the lanthana-ceria-lithia impregnated support with solutions bearing one or more platinum group metals to form a catalyst; (d) air drying the catalyst at ambient temperature for 0-4 hours, and at about 100°-150° C. to dry the catalyst after each impregnation with solutions bearing catalytic metals; and (e) activating the catalyst, which has previously been heated to a temperature of at least 800°-1100° C. in one of the prior steps (b) or (c), at a temperature of about 250°-550° C.

Claim 11

A method of making a catalyst which is suitable for use as a three-way catalyst for auto emission comprising the steps of (a) impregnating an alumina support which has been heated to at least 300° C. with a solution containing a lanthanum salt which is either in the form of lanthanum salt only or in the form of lanthanum-rich rare earth salts, which upon calcination gives rare earth oxides where La 2 O 3 is at least 50% by weight of the total rare earth oxides; (b) heating the impregnated support to at least decompose the lanthanum salt to obtain a lanthana impregnated support; (c) applying promoters and one or more platinum group metals by either A. (1) impregnating the lanthana-impregnated alumina support from step (b) with a soluble cerium salt solution; (2) heating the impregnated support to at least decompose the cerium salt to obtain a lanthana-ceria impregnated support; and (3) impregnating the lanthana-ceria impregnated support with solutions bearing one or more platinum group metals and at least one alkali metal; or B. (1) impregnating the lanthana impregnated support from step (b) with a solution containing a soluble cerium salt and a lithium salt; (2) heating the impregnated support to at least decompose the cerium and lithium salts to obtain a lanthana-ceria-lithia impregnated support; and (3) impregnating the lanthana-ceria-lithia impregnated support with solutions bearing one or more platinum group metals to form a catalyst; (d) air drying the catalyst at ambient temperature for 0-4 hours, and at about 100°-150° C. to dry the catalyst after each impregnation with solutions bearing catalytic metals; and (e) activating the catalyst, which has previously been heated to a temperature of at least 800°-1100° C. in one of the prior steps (b) or (c), at a temperature of about 250°-550° C.