Nitrogen oxide sorbent and exhaust gas cleaning catalyst
A nitrogen oxide storage material comprising: Mg 1-y Al 2 O 4-y , wherein y is a number satisfying 0≤y≤0.2, a noble metal, an oxide of a metal other than the noble metal, and a barium compound, the noble metal, the oxide, and the barium compound being loaded on Mg 1-y Al 2 O 4-y . The metal oxide comprises at least one metal oxide selected from zirconium oxide, praseodymium oxide, niobium oxide, and iron oxide.
1. A nitrogen oxide storage material comprising:
Mg 1-y Al 2 O 4-y , wherein y is a number satisfying 0≤y≤0.2,
a noble metal,
a zirconium oxide, and
a barium compound,
the noble metal, the zirconium oxide, and the barium compound being loaded on Mg 1-y Al 2 O 4-y .
2. The nitrogen oxide storage material according to claim 1 , wherein the zirconium oxide is present in an amount of 1 to 50 mass % based on the nitrogen oxide storage material.
3. The nitrogen oxide storage material according to claim 2 , wherein the zirconium oxide is present in an amount of 5 to 20 mass % based on the nitrogen oxide storage material.
4. The nitrogen oxide storage material according to claim 1 , wherein the barium compound is barium carbonate.
5. The nitrogen oxide storage material according to claim 1 , wherein the noble metal is platinum.
6. The nitrogen oxide storage material according to claim 1 , wherein the Mg 1-y Al 2 O 4-y is MgAl 2 O 4 .
7. The nitrogen oxide storage material according to claim 1 , wherein the nitrogen oxide storage material is in a powder form and has a BET specific surface area of 10 to 200 m 2 /g.
8. An exhaust gas purification catalyst comprising the nitrogen storage material according to claim 1 .
9. A method for producing the nitrogen oxide storage material according to claim 1 , the method comprising the following steps (1), (2), and (3) in this order:
(1) mixing a solution containing a soluble salt of zirconium and a Mg 1-y Al 2 O 4-y powder, evaporating the mixture to dryness, and then obtaining a M1/MAO which is a powder of Mg 1-y Al 2 O 4-y on which the zirconium oxide M1 is loaded;
(2) mixing the M1/MAO with a solution containing a soluble barium salt, evaporating the mixture to dryness, and then obtaining a M1/Ba/MAO which is a powder of Mg 1-y Al 2 O 4-y on which the zirconium oxide and a barium compound are loaded; and
(3) mixing the M1/Ba/MAO with a solution containing a soluble salt of the noble metal M2, evaporating the mixture to dryness, and then obtaining a M2/M1/Ba/MAO which is a powder of Mg 1-y Al 2 O 4-y on which the zirconium oxide, the barium compound, and the noble metal M2 are loaded.
10. A method for producing the nitrogen oxide storage material according to claim 1 , the method comprising the following steps (1), (2), and (3) in this order:
(1) mixing an aqueous solution containing a water soluble salt of zirconium and a Mg 1-y Al 2 O 4-y powder, evaporating the mixture to dryness, and firing the resulting mixture to give a M1/MAO which is a powder of Mg 1-y Al 2 O 4-y on which the zirconium oxide M1 is loaded;
(2) mixing the M1/MAO with an aqueous solution containing a water soluble barium salt, evaporating the mixture to dryness, and firing the resulting mixture to give a M1/Ba/MAO which is a powder of Mg 1-y Al 2 O 4-y on which the zirconium oxide and a barium compound are loaded; and
(3) mixing the M1/Ba/MAO with an aqueous solution containing a water soluble salt of the noble metal M2, evaporating the mixture to dryness, and firing the resulting mixture to yield a M2/M1/Ba/MAO which is a powder of Mg 1-y Al 2 O 4-y on which the zirconium oxide, the barium compound, and the noble metal M2 are loaded.