Catalyst for purifying exhaust gas and method of producing same
First Claim
1. A catalyst for purifying exhaust gas, comprising:
- a monolithic carrier; and
a catalyst component carrying layer formed on a surface of said monolithic carrier, said carrier component carrying layer includinga catalyst component including rhodium, anda catalyst component substrate for carrying the catalyst component, said catalyst component substrate including a composite oxide containing zirconium oxide and at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum, said composite oxide having a composition represented by the following general formula;
space="preserve" listing-type="equation">X.sub.a Zr.sub.b O.sub.cwhere X is at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum; and
a, b, and c, indicate atomic ratios, in which a is within a range of from 0.01 to 0.6 on the basis of b being 1.0 and c is a number which satisfies the valence of elements of the formula Xa Zrb Oc.
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Accused Products
Abstract
A catalyst for purifying exhaust gas from an automotive internal combustion engine. The catalyst comprises a monolithic carrier which is coated with a catalyst component carrying layer which includes rhodium and a zirconium oxide. The zirconium oxide contains at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum. The zirconium oxide in the catalyst component carrying layer has a composition represented by a general formula of X!a Zrb Oc where X is at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum; and a, b and c indicate ratios in number of atoms, in which a is within a range of from 0.01 to 0.6 on the assumption of b being 1.0, and c is a number of oxygen atom which satisfies valence of respective elements.
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Citations
10 Claims
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1. A catalyst for purifying exhaust gas, comprising:
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a monolithic carrier; and a catalyst component carrying layer formed on a surface of said monolithic carrier, said carrier component carrying layer including a catalyst component including rhodium, and a catalyst component substrate for carrying the catalyst component, said catalyst component substrate including a composite oxide containing zirconium oxide and at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum, said composite oxide having a composition represented by the following general formula;
space="preserve" listing-type="equation">X.sub.a Zr.sub.b O.sub.cwhere X is at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum; and
a, b, and c, indicate atomic ratios, in which a is within a range of from 0.01 to 0.6 on the basis of b being 1.0 and c is a number which satisfies the valence of elements of the formula Xa Zrb Oc. - View Dependent Claims (2, 3, 4)
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5. A method of producing a catalyst for purifying exhaust gas, comprising the following steps:
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adding a water soluble salt of zirconium and a water soluble salt of at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum into water to form a liquid containing at least one catalyst component; adding an aqueous solution containing at least one of aqueous ammonia and an ammonium compound to the liquid so as to adjust the pH of the liquid within a range of from 6.0 to 10.0 thereby obtaining precipitate; drying the precipitate; firing the dried precipitate thereby forming a composite oxide containing zirconium oxide and at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum, said composite oxide having a composition represented by the following general formula;
space="preserve" listing-type="equation">X.sub.a Zr.sub.b O.sub.cwhere X is at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum; and
a, b, and c, indicate atomic ratios, in which a is within a range of from 0.01 to 0.6 on the basis of b being 1.0 and c is a number which satisfies the valence of elements of the formula Xa Zrb Oc ;impregnating the composite oxide with rhodium; providing a monolithic carrier; and coating the composite oxide containing rhodium on a surface of the monolithic carrier.
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6. A method of producing a catalyst for purifying exhaust gas, comprising the following steps:
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preparing a suspension liquid containing zirconium oxide; adding a water soluble salt of at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum into water to form a liquid containing at least one catalyst component; gradually dropping the catalyst component containing liquid to the suspension liquid to form a mixed liquid; adjusting the pH of the mixed liquid at a level ranging from 6.0 to 10.0 to form precipitate; and drying the precipitate; firing the dried precipitate thereby forming a composite oxide containing zirconium oxide and at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum, said composite oxide having a composition represented by the following general formula;
space="preserve" listing-type="equation">X.sub.a Zr.sub.b O.sub.cwhere X is at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum; and
a, b, and c, indicate atomic ratios, in which a is within a range of from 0.01 to 0.6 on the basis of b being 1.0 and c is a number which satisfies the valence of elements of the formula Xa Zrb Oc ;impregnating the composite oxide with rhodium; providing a monolithic carrier; and coating the composite oxide containing rhodium on a surface of the monolithic carrier.
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7. A method of producing a composite oxide forming part of a catalyst for purifying exhaust gas, comprising the following steps:
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adding a water soluble salt of zirconium and a water soluble salt of at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum into water to form a liquid containing at least one catalyst component; adding an aqueous solution containing at least one of ammonia and an ammonium compound to the liquid so as to adjust the pH of the liquid within a range of from 6.0 to 10.0 thereby obtaining precipitate; drying the precipitate; and firing the dried precipitate thereby obtaining the composite oxide containing zirconium oxide and at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum, said composite oxide having a composition represented by the following general formula;
space="preserve" listing-type="equation">X.sub.a Zr.sub.b O.sub.cwhere X is at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum; and
a, b, and c, indicate atomic ratios, in which a is within a range of from 0.01 to 0.6 on the basis of b being 1.0 and c is a number which satisfies the valence of elements of the formula Xa Zrb Oc.
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8. A method of producing a composite oxide forming part of a catalyst for purifying exhaust gas, comprising the following steps:
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preparing a suspension liquid containing zirconium oxide; adding a water soluble salt of at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum into water to form a liquid containing at least one catalyst component; gradually dropping the catalyst component containing liquid to the suspension liquid to form a mixed liquid; adjusting the pH of the mixed liquid at a level ranging from 6.0 to 10.0 to form precipitate; drying the precipitate; and firing the dried precipitate thereby obtaining the composite oxide containing zirconium oxide and at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum, said composite oxide having a composition represented by the following general formula;
space="preserve" listing-type="equation">X.sub.a Zr.sub.b O.sub.cwhere X is at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum; and
a, b, and c, indicate atomic ratios, in which a is within a range of from 0.01 to 0.6 on the basis of b being 1.0 and c is a number which satisfies the valence of elements of the formula Xa Zrb Oc.
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9. A catalyst for purifying exhaust gas, comprising:
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a monolithic carrier; and a catalyst component carrying layer formed on a surface of said monolithic carrier, said catalyst carrier component carrying layer including rhodium and a composite oxide, said composite oxide containing zirconium oxide and at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum; said composite oxide being produced by a process including the following steps; adding a water soluble salt of zirconium and a water soluble salt of at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum into water to form a liquid containing at least one catalyst component; adding an aqueous solution containing at least one of ammonia and an ammonium compound to the liquid so as to adjust the pH of the liquid within a range of from 6.0 to 10.0 thereby obtaining precipitate; drying the precipitate; and firing the dried precipitate thereby obtaining the composite oxide containing zirconium oxide and at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum, said composite oxide having a composition represented by the following general formula;
space="preserve" listing-type="equation">X.sub.a Zr.sub.b O.sub.cwhere X is at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum; and
a, b, and c, indicate atomic ratios, in which a is within a range of from 0.01 to 0.6 on the basis of b being 1.0 and c is a number which satisfies the valence of elements of the formula Xa Zrb Oc.
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10. A catalyst for purifying exhaust gas, comprising:
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a monolithic carrier; and a catalyst component carrying layer formed on a surface of said monolithic carrier, said catalyst carrier component carrying layer including rhodium and a composite oxide, said composite oxide containing zirconium oxide and at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum; said composite oxide being produced by a process including the following steps; preparing a suspension liquid containing zirconium oxide; adding a water soluble salt of at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum into water to form a liquid containing at least one catalyst component; gradually dropping the catalyst component containing liquid to the suspension liquid to form a mixed liquid; adjusting the pH of the mixed liquid at a level ranging from 6.0 to 10.0 to form precipitate; drying the precipitate; and firing the dried precipitate thereby obtaining the composite oxide containing zirconium oxide and at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum, said composite oxide having a composition represented by the following general formula;
space="preserve" listing-type="equation">X.sub.a Zr.sub.b O.sub.cwhere X is at least one element selected from the group consisting of magnesium, calcium, strontium, barium, yttrium and lanthanum; and
a, b, and c, indicate atomic ratios, in which a is within a range of from 0.01 to 0.6 on the basis of b being 1.0 and c is a number which satisfies the valence of elements of the formula Xa Zrb Oc.
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Specification