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. A process for producing an oxygen storage material comprising cerium oxide and at least one second oxide of a metal M 1 , the process comprising the steps of:
a) mixing an aqueous solution of a cerium oxide precursor with an aqueous solution of a precursor of an oxide of a metal M 1 selected from the group consisting of an alkaline earth metal, rare earth metal, zirconium, zinc, cobalt, copper and manganese to form a mixture;
b) adding a first precipitation agent to the mixture, to form an aqueous suspension containing a precipitate, wherein the cerium oxide and the oxide of the metal M 1 form Ce/M 1 mixed oxide solid solution particles, and adding to the suspension: (i) a precursor of an oxide of a metal M 2 and (ii) barium hydroxide as a second precipitation agent to deposit M 2 on Ce/M 1 mixed oxide solid solution particles: and
c) separating the precipitate from the suspension, drying and calcining the precipitate.
2. The process according to claim 1 , wherein ammonium is used as the first precipitation agent.
3. The process as defined according to claim 1 , wherein mixing in step a) is performed in a tubular flow reactor by bubbling gaseous nitrogen into the reactor.
4. The process according to claim 1 , wherein the precursor solutions cerium metal, M 1 and M 2 are mixed by microwave treament.
5. The process according to claim 1 , wherein the precursor solutions containing cerium metal, M 1 and M 2 are mixed by ultrasonic treatment.
6. A process for producing an oxygen storage material comprising cerium oxide and at least one second oxide of a metal M 1, the process comprising the steps of: a) mixing an aqueous solution of a cerium oxide precursor with an aqueous solution of a precursor of an oxide of a metal M selected from the group consisting of an alkaline earth metal, rare earth metal, zirconium, zinc, cobalt, copper and manganese to form a mixture, wherein the mixing is performed in a tubular flow reactor by bubbling gaseous nitrogen into the reactor; b) adding a first precipitation agent to the mixture, to form an aqueous suspension containing a precipitate, wherein the cerium oxide and the oxide of the metal M1 form Ce/M 1 mixed oxide particles; and c) separating the precipitate from the suspension, drying and calcining the precipitate.
7. A process for producing an oxygen storage material comprising cerium oxide and at least one second oxide of a metal M 1, the process comprising the steps of: a) mixing an aqueous solution of a cerium oxide precursor with an aqueous solution of a precursor of an oxide of a metal M 1 selected from the group consisting of an alkaline earth metal, rare earth metal, zirconium, zinc, cobalt, copper and manganese to form a mixture, wherein a precursor of an oxide of another metal M 2 is added to form precursor solutions in the mixture and the mixing is achieved by microwave b) adding a first precipitation agent to the mixture, to form an aqueous suspension containing a precipitate, wherein the cerium oxide and the oxide of the metal M 1 form Ce/M 1 mixed oxide particles; and c) separating the precipitate from the suspension, drying and calcining the precipitate.