Oxygen storage material, process for its preparation and its application in a catalyst
An oxygen storage material comprising cerium oxide and at least one second oxide of a metal M 1 is disclosed as well as a process for manufacturing the material and the use of this material in an exhaust gas cleaning catalyst. In a preferred embodiment the oxygen storage material comprises particles from a Ce/M 1 mixed oxide solid solution coated with an oxide of another metal M 2 . Metal M 1 e.g. can be calcium or zirconium while metal M 2 most preferably is aluminum.
1. An oxygen storage material comprising cerium oxide and at least one second oxide of a metal M 1 selected from the group consisting of alkaline earth metal, rare earth metal, zirconium, zinc, cobalt, copper and manganese wherein the cerium oxide and the second metal oxide form Ce/M 1 mixed oxide particles and wherein an oxide of a metal M 2 selected from the group consisting of aluminum, magnesium, zirconium, silicon, titanium, gallium, indium, lanthanum, and mixtures thereof is deposited onto the surface of the Ce/M 1 mixed oxide particles.
2. The oxygen storage material according to claim 1 , wherein metal M 1 is calcium or zirconium and metal M 2 is aluminum.
3. The oxygen storage material according to claim 2 , wherein the oxide of metal M 2 is admixed with an oxide of a rare earth metal.
4. The oxygen storage material according to claim 3 , wherein the rare earth metal admixed with metal M 2 is lanthanum.
5. The oxygen storage material according to claim 4 , comprising cerium in an amount of more than about 50 and less than about 99 mole-% relative to the composition of the Ce/M 1 mixed oxide particles and wherein the oxide of metal M 2 is present in an amount of about 1 to about 80 mol-% relative to the total composition of the oxygen storage material.
6. The oxygen storage material according to claim 5 , wherein the oxygen storage capacity measured by hydrogen uptake is at least about 0.9 mmol hydrogen per gram.
7. The oxygen storage material according to claim 6 , wherein the oxygen storage material has a temperature window in an H 2 -TPR curve, and the temperature window of the H 2 -TPR curve is wider than 120° C.
8. The oxygen storage material according to claim 1 , wherein the cerium oxide and the oxide of metal M 1 form a single phase mixed oxide solid solution.
9. A catalyst for cleaning the exhaust gas of internal combustion engines comprising an oxygen storage material according to claim 1 .