Auto exhaust catalyst composition having low H.sub.2 S emissions and method of making the catalyst
AssigneeW. R. Grace & Co.-Conn.
InventorMichael V. Ernest
Life of this patent
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Abstract
A catalyst suitable for use as a three-way catalyst having low H.sub.2 S emissions for emission control and with substantially no ceria present is made with a refractory oxide particle or powder support having deposited thereon about 0.5-20% by weight of a non-rate earth oxide stabilizer, 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 preferred refractory oxide is alumina and the non-rare earth oxide stabilizer can be an oxide such as ZrO.sub.2, MgO, CaO, SnO, CaO, Y.sub.2 O.sub.3, TiO.sub.2, ZnO, B.sub.2 O.sub.3, P.sub.2 O.sub.5, SnO.sub.2, Bi.sub.2 O.sub.3, or SiO.sub.2 with the preferred oxide being zirconia.
Claims24
A catalyst suitable for use as a three-way catalyst having low H.sub.2 S emissions for emission control with no substantial amount of ceria or nickel present comprising a formed refractory oxide particle or refractory oxide powder support having a B.E.T. surface area of 50-250 m.sup.2 g and having directly deposited thereon about 0.5-20% by weight of a non-rare earth oxide stabilizer selected from the group consisting of ZrO.sub.2, MgO, CaO, SrO, BaO, Y.sub.2 O.sub.3, ZnO, B.sub.2 O.sub.3, P.sub.2 O.sub.5, SiO.sub.2 and mixtures thereof;
- at least about 0.5 to about 5% by weight of an alkali metal oxide as a promoter;
- and having subsequently deposited thereon a catalytically-effective amount of one or more platinum group metals selected from the group of Pt, Pd, Ir, Rh, or mixtures thereof;
- binary mixtures of Pt-Pd, Pt-Rh, or Pd-Rh;
- and tertiary mixtures of Pt-Pd-Rh.
A method of making a catalyst which is suitable for use as a three-way catalyst with low H.sub.2 S emissions for emission control with no substantial amount of ceria or nickel present comprising the steps of
- (A) impregnating a refractory oxide support with a solution containing either
- (1) a non-rare earth stabilizer salt which will yield oxides selected from the group consisting of ZrO.sub.2, MgO, CaO, SrO, BaO, Y.sub.2 O.sub.3, ZnO, B.sub.2 O.sub.3, P.sub.2 O.sub.5, SiO.sub.2 and mixtures thereof in an amount of 0.5-20% by weight of the refractory oxide support;
- or
- (2) a non-rare earth stabilizer salt which will yield oxides selected from the group consisting of ZrO.sub.2, MgO, CaO, SrO, BaO, Y.sub.2 O.sub.3, ZnO, B.sub.2 O.sub.3, P.sub.2 O.sub.5, SiO.sub.2 and mixtures thereof in an amount of 0.5-20% by weight of the refractory oxide support plus an alkali metal compound;
- (B) optionally drying the impregnated support at a temperature of 100-200.degree. C.;
- (C) heating the impregnated support at 400-1100.degree. C. to at least decompose the non-rare earth stabilizer salt to obtain a non-rare earth oxide stabilized support;
- (D) applying one or more catalytic platinum group metals and optionally at least one alkali metal promoter by either
- (1) impregnating the non-rare earth stabilizer oxide impregnated support from step (C) with solutions bearing one or more platinum group metals and a soluble alkali metal salt solution;
- or
- (2) impregnating the non-rare earth stabilizer oxide impregnated support from step (C) with solutions bearing one or more platinum group metals when the refractory oxide in step (A) was impregnated with an alkali metal compound;
- or
- (3)
- (a) impregnating the non-rare earth stabilizer oxide impregnated support from step (C) with solutions bearing one or more platinum group metals;
- (b) air drying the catalyst at temperature for 0-4 hours, and at about 100-200 .degree.C. to dry the catalyst after the impregnation;
- and
- (c) further impregnating the impregnated support from step (D) (3) (b) with a soluble alkali metal salt solution;
- or
- (4)
- (a) impregnating the non-rare earth stabilizer oxide impregnated support from step (C) with a solution bearing one or more platinum group metals and a soluble alkali metal salt solution;
- (b) air drying the catalyst at ambient temperature for 0-4 hours, and at about 100-200.degree. C. to dry the catalyst after the impregnation with solutions bearing catalytic metals;
- and
- (c) further impregnating the impregnated support from step (D)(4)(b) with a solution of one or more platinum group metals;
- (E) air drying the catalyst at ambient temperature for 0-4 hours, and at about 100-200.degree. C. to dry the catalyst after the impregnation in step (D);
- and
- (F) activating the catalyst containing the platinum group metals in step (D) at a temperature of about 300-650.degree. C.;
- and
- (G) optionally
- (1) further impregnating the activated catalyst from step (F) with a soluble alkali metal salt solution;
- (2) air drying the catalyst at ambient temperature for 0-4 hours, and at about 100-200.degree. C. to dry the catalyst after the impregnation;
- and
- (3) optionally further activating the dried catalyst from step (G)(2) in air at 300-650.degree. C. PG,28
Dependencies are inferred from the claim text.