Composites of aluminum oxide and cerium/zirconium mixed oxides

1. An Al/Ce/Zr oxide composite comprising aluminum oxide and cerium/zirconium mixed oxides in the form of a “solid solution”, wherein Al 2 O 3 and the Ce/Zr and optionally rare earth (RE) mixed oxides are homogeneously distributed side by side comprising

20% to 80% by weight aluminum, calculated as Al 2 O 3 ;

5% to 80% by weight zirconium, calculated as ZrO 2 ;

5% to 80% by weight cerium, calculated as CeO 2 ; and

0% to 12% by weight, rare earth metal(s) (RE) calculated as RE 2 O 3 .

2. The oxide composite according to claim 1 comprising

0.1% to 9% by weight, rare earth metal(s) (RE), calculated as RE 2 O 3 .

3. The oxide composite according to claim 1 comprising

40% to 70% by weight, aluminum, calculated as Al 2 O 3 ;

5% to 40% by weight, zirconium, calculated as ZrO 2 ;

5% to 40% by weight, cerium, calculated as CeO 2 ; and

0 to 12% by weight, rare earth metal(s) (RE), calculated as RE 2 O 3 .

4. The oxide composite according to claim 1 having after 4 h at 1200° C. a surface area of at least 20 m 2 /g.

5. The oxide composite according to claim 1 having after 4 h at 1200° C. a surface area of at least 40 m 2 /g.

6. The composite according to claim 1 , wherein the oxide composite is an Al/Ce/Zr rare earth oxide composite comprising as rare earth oxides the oxides of neodymium, praseodymium, yttrium and/or lanthanum.

7. The composite according to claim 1 further comprising platinum, rhodium and/or palladium.

8. The composite according to claim 1 , wherein the composite aluminum oxide and cerium/zirconium mixed oxides and optionally rare earth mixed oxides are obtained by a method comprising the following steps:

(a) providing a suspension comprising boehmite as the alumina precursor and adjusting the pH to 6 to 11.5;

(b) providing an aqueous metal salt solution comprising at least metal salts of cerium and of zirconium;

(c) bringing the suspension of (a) in contact with the metal salt solution from (b) at temperatures of 5 to 95° C. or subjecting the slurry so obtained to a temperature of from 5 to 95° C.;

(d) isolating the solids from (c) and

(e) calcining the solids from (d).

9. The composite according to claim 8 , wherein

i) the boehmites are added having at least one carboxyl group (—COO and/or —COOH) and one or more further groups selected from hydroxy (—OH), oxo (—O), carboxy (—COO and/or —COOH) and/or amine (—NH and/or —NH 2 ) groups; or

ii) the suspension of step (c) is hydrothermally aged in an aqueous environment, at a temperature of at least 90° C. and for at least one hour, or

iii) the measures according to i) and ii) both are applied.

10. The composite according to claim 8 , wherein the composite also comprises one or more members of the following group: alkaline earth elements/compounds, rare earth (RE) elements/compounds, zirconium compounds and silicon compounds, which are water soluble and which are added only after step (c) or after step (d).

11. The composite according to claim 8 , wherein the suspension of (c) is hydrothermally aged in an aqueous environment at a temperature of at least 120° C. for at least four hours.

12. The composite according to claim 8 , wherein the water-soluble metal salts are acetates, nitrates and/or chlorides.

13. The composite according to claim 8 , wherein barium salts are optionally added, but no other alkali and/or alkaline earth salts are added.

14. The composite according to claim 8 , wherein the suspension comprising boehmite is adjusted to the pH by a nitrogen base.

15. The composite according to claim 8 , comprising as part of the method a drying step after step (d) and before step (e).

16. The composite according to claim 15 , wherein the composite also comprises one or more members of the following group: alkaline earth elements/compounds, rare earth (RE) elements/compounds, zirconium compounds and silicon compounds, which are water soluble and which are added before the drying step.