Catalysts for controlling auto exhaust emissions including hydrocarbon, carbon monoxide, nitrogen oxides and hydrogen sulfide and method of making the catalysts
AssigneeW. R. Grace & Co.-Conn.
InventorsGwan Kim, Michael V. Ernest, Stanislaw Plecha
Life of this patent
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Abstract
A catalyst, which is capable of controlling not only HC, CO and NOx, but also H.sub.2 S emission from the tail pipe of catalytic converter-equipped automobiles, is made of noble metals promoted with ceria-rich rare earth oxides, preferably doubly promoted along with alkali metal oxides, and oxides of nickel and/or iron as an H.sub.2 S gettering ingredient. The oxides of nickel and/or iron are present in an H.sub.2 S gettering effective amount and in an amount up to 10 wt %. The alumina support can have additionally from 0 to 20% SiO.sub.2 present.
Claims34
In a catalyst suitable for use as a catalyst for auto emission control characterized by 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.sub.2 O.sub.3 which is either in the form of lanthana only or in the form of lanthana-rich rare earth oxides where the La.sub.2 O.sub.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, the improvement comprising adding H.sub.2 S gettering capability by having the catalyst further comprise
- (a) an H.sub.2 S gettering metal oxide selected from the group consisting of oxides of Ni, Fe and mixtures thereof in an amount from an H.sub.2 S gettering effective amount up to 10 weight %, provided that when the H.sub.2 S gettering metal oxide is just NiO, the maximum concentration of the NiO in the first 300 micron layer is at least about twice its average concentration throughout the support;
- and
- (b) wherein said alumina support can have additionally from 0 to 20% SiO.sub.2 present.
A method of making a catalyst which is suitable for use for auto emission comprising the steps of
- (a) impregnating an alumina support which has been heated to at least 300.degree. C. with a solution containing a lanthanum salt which is either in the form of lanthanum-rich rare earth salts, which upon calcination gives rare earth oxides where La.sub.2 O.sub.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, an H.sub.2 S gettering metal oxide selected from the group consisting of NiO, Fe.sub.2 O.sub.3 and mixtures thereof, 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, said H.sub.2 S gettering metal oxide, 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 and said H.sub.2 S gettering metal oxide to form a catalyst;
- wherein when said H.sub.2 S gettering metal oxide is applied the application procedure is controlled to provide an amount from an H.sub.2 S gettering effective amount up to 10 weight % and in the event that the H.sub.2 S gettering metal oxide is just NiO, controlling the maximum concentration of the NiO in the first 300 micron layer so that it is at least about twice its average concentration throughout the support;
- (d) air drying the catalyst at ambient temperature for 0-4 hours, and at about 100.degree.-150.degree. 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.degree.-1100.degree. C. in one of the prior steps (b) or (c), at a temperature of about 250.degree.-550.degree. C.
Dependencies are inferred from the claim text.