Composites of aluminum oxide and cerium/zirconium mixed oxides

Abstract

The subject matter of the invention is a method for producing composites comprising aluminum oxide and cerium/zirconium mixed oxides, hereinafter referred to briefly as Al/Ce/Zr oxide composite(s) using boehmite and soluble cerium/zirconium salts. Al/Ce/Zr oxide composites produced in this way have an increased thermal stability.

Claims

1. An Al/Ce/Zr oxide composite comprising aluminum oxide and cerium/zirconium mixed oxides in the form of a solid solution, wherein Al.sub.2O.sub.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.sub.2O.sub.3; 5% to 80% by weight zirconium, calculated as ZrO.sub.2; 5% to 80% by weight cerium, calculated as CeO.sub.2; and 0% to 12% by weight, rare earth metal(s) (RE) calculated as RE.sub.2O.sub.3.

2. The oxide composite according to claim 1 comprising 0.1% to 9% by weight, rare earth metal(s) (RE), calculated as RE.sub.2O.sub.3.

3. The oxide composite according to claim 1 comprising 40% to 70% by weight, aluminum, calculated as Al.sub.2O.sub.3; 5% to 40% by weight, zirconium, calculated as ZrO.sub.2; 5% to 40% by weight, cerium, calculated as CeO.sub.2; and 0 to 12% by weight, rare earth metal(s) (RE), calculated as RE.sub.2O.sub.3.

4. The oxide composite according to claim 1 having after 4 h at 1200 C. a surface area of at least 20 m.sup.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.sup.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.sub.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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be explained in greater detail based on the illustrations, in which

(2) FIG. 1 shows the particle size distributions of Examples A1 and A2 in aqueous suspensions;

(3) FIG. 2 shows x-ray powder diffractograms of the material from Example 2 after calcination.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(4) The following experimental examples show that

(5) a) higher residual surface areas are obtained in comparison with the synthesis procedures in EP 1172139 B1 and WO 2012/067654 A1,

(6) b) high residual surface areas are obtained even after calcination under especially sharp conditions (1150 C./36 h, 1200 C./4 h),

(7) c) in Comparative Example 3, surface areas which are also very high and are within the range of the inventive composites produced by the process described here (Comparative Example 3 and Example 6) are obtained, however, the process described here does not require the use of sodium, which is a significant advantage in the process technology because sodium leads to poisoning of noble metal catalysts

(8) d) in Comparative Example 5 high residual surface areas were also obtained which are also within the range of the composites produced by means of the process described here (Comparative Example 5, Examples 7 and 8).

(9) However, in one embodiment, the process described here proposes the use of modified boehmite, which facilitates dispersibility in an alkaline medium. Thus there is no agglomeration or sedimentation of the boehmite, but instead there is an especially homogeneous precipitation and distribution of the CeO.sub.2/ZrO.sub.2/(optional rare earth oxide) components at an elevated pH in the presence of finally dispersed boehmite, which is apparent on the basis of the particle sizes in the aqueous suspension at a high pH. This is demonstrated in Examples A1 and A2.

(10) The measurements of the surface areas (BET) were performed using a Micromeritics TriStar 3000 according to DIN ISO 9277. The x-ray diffractograms were measured using a Panalytical XPert Pro MDB diffractometer. The percentage amounts are percent by weight, unless otherwise indicated. The particle distributions were determined using a Malvern Mastersizer 2000 with the Hydro-S dispersion unit in water. The measurement was performed according to ISO 13320:2009 using the Fraunhofer method for the analysis.

Comparative Example 1

Synthesis According to Example 27 of EP 1172139 B1

(11) Composition: 61.5% Al.sub.2O.sub.3, 21% CeO.sub.2, 15% ZrO.sub.2, 2.5% Y.sub.2O.sub.3

(12) A mixture consisting of 96.43 g of an aqueous solution of zirconyl nitrate (ZrO.sub.2 content=7%), 52.5 g of an aqueous solution of cerium(III) nitrate (CeO.sub.2 content=18%), 6.32 g of an aqueous solution of yttrium nitrate (Y.sub.2O.sub.3 content=17.80%) and 205.61 g aluminum nitrate nonahydrate in crystalline form was mixed with 600 mL water and stirred until obtaining a clear solution.

(13) This solution was mixed with 7.47 g of a 35% H.sub.2O.sub.2 solution (corresponding to 1.2 times the molar quantity of cerium) and this mixture was stirred for approx. 25 minutes. The resulting solution was then brought to a pH of 7 by adding a 24% ammonia solution and stirred for 15 minutes. The resulting mixture was filtered and the filter residue was washed with deionized water at 60 C. This filter cake was then dried at 120 C. for sixteen hours. Following that, the dry filter cake was calcined first at 300 C. for five hours and then at 700 C. for five hours.

(14) The measured surface area is shown in Table 1.

(15) BET after 300 C./5 hours+700 C./five hours (starting material): 168 m.sup.2/g

(16) BET after 950 C./5 hours: 109 m.sup.2/g

(17) BET after 1000 C./4 hours: 84 m.sup.2/g

(18) BET after 1100 C./2 hours: 32 m.sup.2/g

Comparative Example 2

Synthesis According to Example 1 of EP 1172139 B1

Composition: 41% Al.SUB.2.O.SUB.3., 30% CeO.SUB.2., 23% ZrO.SUB.2., 2.5% Y.SUB.2.O.SUB.3., 3.5% La.SUB.2.O.SUB.3

(19) A mixture consisting 145.93 g of an aqueous solution of zirconyl nitrate (ZrO.sub.2 content=7%), 72.25 g of an aqueous solution of cerium(III) nitrate (CeO.sub.2 content=18%), 6.07 g of an aqueous solution of yttrium nitrate (Y.sub.2O.sub.3 content=17.80%), 10.81 g of an aqueous solution of lanthanum nitrate (La.sub.2O.sub.3 content=14.57%) and 138.08 g aluminum nitrate nonahydrate in crystalline form was mixed with 600 mL water and stirred until a clear solution was obtained.

(20) This solution was mixed with 10.71 g of a 35% H.sub.2O.sub.2 solution (corresponding to 1.2 times the molar quantity of cerium) and this mixture was stirred for approx. 25 minutes. The resulting solution was then brought to a pH of 7 by adding a 24% ammonia solution and stirred for 15 minutes. The resulting mixture was filtered and the filter residue was washed with deionized water at 60 C.

(21) This filter cake was then dried at 120 C. for sixteen hours. Following that, the dry filter cake was calcined first at 300 C. for five hours and then at 700 C. for five hours.

(22) The measured surface area is shown in Table 2.

Comparative Example 3

Synthesis According to Example 6 of WO 2006/070201 A2

Composition: 51% Al.SUB.2.O.SUB.3., 14.2% CeO.SUB.2., 34.8% ZrO.SUB.2

(23) An aluminum nitrate solution was prepared by stirring 112.5 g aluminum nitrate monohydrate into 1500 mL water. To this solution were added 14.77 g of a cerium(III) nitrate solution (CeO.sub.2 content=28.85%) and 149.16 [g] of a zirconyl nitrate solution (ZrO.sub.2 content=7%). This mixture was then stirred at room temperature for 15 minutes. A pH of 10 was adjusted by adding 25% sodium hydroxide solution and this value was maintained during the precipitation process. Then 5 g of 35% H.sub.2O.sub.2 solution was added and the pH was again adjusted to 10. The resulting suspension was then stirred for 60 minutes. Following that the pH was set at 8 by adding 30% nitric acid and the suspension was again stirred for 30 minutes.

(24) The resulting mixture was filtered and the filter residue was washed with deionized water at 60 C. This filter cake was then suspended in 850 mL deionized water and the pH was adjusted to 10 by adding 25% sodium hydroxide solution. The mixture was then autoclaved for six hours at 120 C. The aged suspension was cooled to room temperature, adjusted to a pH of 8 by adding nitric acid and then stirred for 30 minutes.

(25) Following that the suspension was again stirred for one hour at 60 C. and then the liquid was filtered. The resulting filter cake was then washed with deionized water at 60 C. and following that calcined for 4 hour at 850 C. The measured surface area is given in Table 3.

Comparative Example 4

Synthesis According to Example 12 of WO 2012/067654 A1

Composition: 50% Al.SUB.2.O.SUB.3., 30% CeO.SUB.2., 15% ZrO.SUB.2., 3.5% La.SUB.2.O.SUB.3., 1.5% Y.SUB.2.O.SUB.3

(26) Solution A was prepared by adding 6.0 g of a solution of lanthanum nitrate (La.sub.2O.sub.3 content 14.57%) to 53 g of a 24% ammonia solution and 110 g distilled water.

(27) Solution B was prepared by combining 22.19 g zirconyl nitrate (ZrO.sub.2 content=33.80%), 35.89 g cerium(III) nitrate (CeO.sub.2 content=41.80%), 4.21 g of a solution of yttrium nitrate (Y.sub.2O.sub.3 content=4.21%), 100 g distilled water and hydrogen peroxide with a molar ratio of H.sub.2O.sub.2/CeO.sub.2 of 3.

(28) Solution C was prepared by the dissolving 46.3 g sodium aluminate in 200 g distilled water.

(29) Starting with 2 liters of distilled water, it was heated to 65 C. Solution A was added by drops within 25 minutes and the pH was kept at 7.3 at the same time by adding solution C. After adding all of solution A, the remainder of solution C was added completely, thereby adjusting the pH to 9.8. Next the resulting suspension was adjusted to a pH of 4 using dilute nitric acid. Following that solution B was added within 20 minutes. Meanwhile the pH was kept at 4 by adding 10% ammonia solution. After completely adding solution B the pH was raised to 8.2 by adding concentrated ammonia solution. The suspension was filtered and the solids were washed with 2 liters of an aqueous solution of ammonium bicarbonate (120 g/liter H.sub.2O) heated to 60 C. Table 4 lists the resulting surface areas.

Comparative Example 5

Synthesis According to Comparative Example 3 of U.S. Pat. No. 6,831,036 and/or Example 7 of WO 2006/119549 A1

Composition: 50% Al.SUB.2.O.SUB.3., 30% CeO.SUB.2., 15% ZrO.SUB.2., 3.5% La.SUB.2.O.SUB.3., 1.5% Y.SUB.2.O.SUB.3

(30) 15 g CeO.sub.2, 7.5 g ZrO.sub.2, 1.75 g La.sub.2O.sub.3 and 0.75 g and 0.75 g Y.sub.2O.sub.3 in the form of their nitrates were dissolved in water, then 31.53 g DISPERAL HP 14 (boehmite Al.sub.2O.sub.3 content=79.3%) was added to this acidic solution and the resulting suspension was stirred for 30 minutes. Concentrated ammonia solution (300 g) was diluted with 750 mL water and used as the starting material at room temperature. The acidic boehmite/metal nitrate solution was added by drops slowly to the ammonia solution and stirring was continued for 30 minutes after the addition was concluded. The solids were separated by filtration, washed with 1.5 liters water and then dried for sixteen hours at 100 C.

(31) Table 4 shows the resulting surface areas.

Example A1

Preparing an Alkaline Boehmite Suspension by Using a Pure Boehmite

(32) A suspension with an Al.sub.2O.sub.3 content of 5% was prepared by stirring DISPERAL HP 14 (boehmite) into deionized water at pH 7. Next the pH was set at 10 by adding a 24% ammonia solution. The particle sizes in the suspension were determined by laser diffraction (Mastersizer):

(33) D.sub.10=0.96 m; D.sub.50=5.11 m; D.sub.90=28.34 m

(34) The measured particle size distributions are shown in FIG. 1.

Example A2

Preparing an Alkaline Boehmite Suspension by Using a Modified Boehmite

(35) A suspension with an Al.sub.2O.sub.3 content of 5% was prepared by stirring DISPERAL HP 14/7 (boehmite modified with citric acid) into deionized water at pH 7. Next the pH was set at 10 by adding a 24% ammonia solution. The particle sizes in the suspension were determined by laser diffraction (Mastersizer):

(36) D.sub.10=0.09 m; D.sub.50=0.23 m; D.sub.90=0.67 m

(37) The measured particle size distributions are shown in FIG. 1.

Example 1 (According to the Invention)

Composition: 61.5% Al.SUB.2.O.SUB.3., 21% CeO.SUB.2., 15% ZrO.SUB.2., 2.5% Y.SUB.2.O.SUB.3

Corresponds to Comparative Example 1

(38) A metal salt solution consisting of 81.4 g of a solution of ammonium cerium(IV) nitrate (CeO.sub.2 content=12.90%), 103.30 g of a solution of zirconyl nitrate (ZrO.sub.2 content=7.26%) and 7.0 g of a solution of yttrium nitrate (Y.sub.2O.sub.3 content=17.80%) was used as the starting material which was heated to 90 C.

(39) A suspension consisting of 615.0 g DISPERAL HP 14/7 (boehmite modified with citric acid) (Al.sub.2O.sub.3 content=5%) was prepared by stirring the solids into deionized water and then adding 24% ammonia solution up to a pH of 10. The suspension was added by drops slowly to the metal salt solution and after the addition was completed the pH was adjusted to 8.7 by adding 24% ammonia solution. This mixture was then stirred for 30 minutes at 90 C. Following that the mixture was filtered and the filter residue was washed with deionized water at 60 C. The filter cake was resuspended in deionized water while stirring and was then spray dried (inlet temperature=220 C., outlet temperature=110 C.). The dried material was calcined for four hours at 850 C.

Example 2 (According to the Invention)

Composition: 41% Al.SUB.2.O.SUB.3., 30% CeO.SUB.2., 23% ZrO.SUB.2., 2.5% Y.SUB.2.O.SUB.3., 3.5% La.SUB.2.O.SUB.3

Corresponds to Comparative Example 2

(40) A metal salt solution consisting of 96.9 g of a solution of ammonium cerium(IV) nitrate (CeO.sub.2 content=12.90%), 131.96 g of a solution of zirconyl nitrate (ZrO.sub.2 content=7.26%), 10.02 g of a solution of lanthanum nitrate (La.sub.2O.sub.3 content=14.57%) and 5.84 g of a solution of yttrium nitrate (Y.sub.2O.sub.3 content=17.80%) was used as the starting material which was heated to 90 C. A suspension consisting of 341.6 g DISPERAL HP 14/7 (boehmite modified with citric acid) (Al.sub.2O.sub.3 content=5%) was prepared by stirring the solids into deionized water and then adding 24% ammonia solution up to a pH of 10.

(41) TABLE-US-00001 TABLE 1 Measured BET surface areas from Comparative Example 1 and Example 1 after calcining (m.sup.2/g). Comparative Example 1 Example 1 (like EP 1 172 139) (acc. to invention) 5 h/300 C. + 5 h/700 C. 168 126 (starting material) 5 h/950 C. 109 95 4 h/1000 C. 84 89 2 h/1100 C. 32 70

(42) The suspension was added by drops slowly to the metal salt solution and after the addition was completed the pH was adjusted to 8.5 by adding 24% ammonia solution. This mixture was then stirred for 30 minutes at 90 C. Following that the mixture was filtered and the filter residue was washed with deionized water at 60 C. The filter cake was resuspended in deionized water while stirring and was then spray dried (inlet temperature=220 C., outlet temperature=110 C.). The dried material was calcined for four hours at 850 C.

(43) In FIG. 2 the x-ray powder diffractograms of the material from Example 2 after calcining are shown

(44) a) after calcining 4 h at 850 C.

(45) b) after calcining 4 h at 850 C.+4 h at 1100 C.

(46) c) after calcining 4 h at 850 C.+24 h at 1100 C.

(47) d) simulated diffractogram of CeO.sub.2 (cubic)

(48) e) simulated diffractogram of CeO.sub.2 (tetragonal)

Example 3 (According to the Invention)

The Composition Corresponds Exactly to that from Comparative Example 2 41% Al.SUB.2.O.SUB.3., 30% CeO.SUB.2., 23% ZrO.SUB.2., 2.5% Y.SUB.2.O.SUB.3., 3.5% La.SUB.2.O.SUB.3

(49) 220.4 g of a suspension of Pural SB (boehmite, Al.sub.2O.sub.3 content=9.3%) (pH 9.5) was adjusted to a pH of 9.5 with a 24% ammonia solution and used as the starting material. At room temperature, a mixture consisting of 300 g of a solution of cerium acetate (CeO.sub.2 content=5.0%), 50.3 g of a solution of zirconium acetate (ZrO.sub.2 content=22.88%), 24.0 g of a solution of lanthanum acetate (La.sub.2O.sub.3 content=7.3%) and 31.3 g of a solution of yttrium acetate (Y.sub.2O.sub.3 content=4.0%) was added slowly at room temperature. The pH value was kept constant at 9.5 by adding a 24% ammonia solution at the same time. The resulting mixture was then stirred for 45 minutes. Next the suspension was autoclaved for three hours at 140 C. The resulting mixture was filtered and the solids were washed with deionized water at 60 C. This filter cake was dried for sixteen hours in a drying cabinet and then calcined at 850 C.

Example 4 (According to the Invention)

Composition: 41% Al.SUB.2.O.SUB.3., 30% CeO.SUB.2., 23% ZrO.SUB.2., 2.5% Y.SUB.2.O.SUB.3., 3.5% La.SUB.2.O.SUB.3

Corresponds to Comparative Example 2

(50) A boehmite suspension consisting of 492.0 g DISPERAL HP 14/7 (boehmite modified with citric acid) (Al.sub.2O.sub.3 content=5%) was prepared by stirring the solids into deionized water and then adding 24% ammonia solution up to a pH of 10.

(51) At 90 C. a metal salt solution consisting of 139.53 g of a solution of ammonium cerium(IV) nitrate (CeO.sub.2 content=12.90%), 190.1 g of a solution of zirconyl nitrate (ZrO.sub.2 content 7.26%), 14.41 g of a solution of lanthanum nitrate (La.sub.2O.sub.3 content 14.57%) and 5.45 g of a solution of yttrium acetate (Y.sub.2O.sub.3 content 27.54%) was added slowly by drops to this suspension. The pH value was kept constant at 9.0 by adding a 24% ammonia solution at the same time. This mixture was then stirred for 30 minutes at 90 C. Following that the mixture was filtered and the filter residue was washed with deionized water at 60 C. The filter cake was resuspended in deionized water while stirring and then spray dried (inlet temperature=220 C., outlet temperature=110 C.). The dried material was calcined for four hours at 850 C.

Example 5

Composition: 41% Al.SUB.2.O.SUB.3., 30% CeO.SUB.2., 23% ZrO.SUB.2., 2.5% Y.SUB.2.O.SUB.3., 3.5% La.SUB.2.O.SUB.3

Corresponds to Comparative Example 2 but Using by Cerium(III) Nitrate+H.SUB.2.O.SUB.2

(52) A metal salt solution consisting of 58.34 g of a solution of cerium(III) nitrate (CeO.sub.2 content=18.00%), 131.96 g of a solution of zirconyl nitrate (ZrO.sub.2 content=7.26%), 10.02 g of a solution of lanthanum nitrate (La.sub.2O.sub.3 content=14.57%) and 5.84 g of a solution of yttrium acetate (Y.sub.2O.sub.3 content 17.80%) was used as the starting material.

(53) At room temperature 25.74 g of a 30% H.sub.2O.sub.2 solution cooled to 5 C. was added. The resulting suspension was stirred for 10 minutes and then heated to 90 C. A suspension consisting of 341.6 g DISPERAL HP 14/7 (boehmite modified with citric acid) (Al.sub.2O.sub.3 content 5%) was adjusted to a pH of 10 by stirring the solids into deionized water and then adding a 24% ammonia solution.

(54) The suspension was added by drops slowly to the metal salt solution and after the addition was completed the pH was adjusted to 8.3 by adding 24% ammonia solution. This mixture was then stirred for 30 minutes at 90 C. Following that the mixture was filtered and the filter residue was washed with deionized water at 60 C. The filter cake was resuspended in deionized water while stirring and was then spray dried (inlet temperature=220 C., outlet temperature=110 C.). The dried material was calcined for four hours at 850 C.

(55) TABLE-US-00002 TABLE 2 Measured surface areas (BET) from Examples 2-6 and Comparative Example 2 after calcining in m.sup.2/g. Comparative Exam- Exam- Exam- Exam- Example 2, like ple 2 ple 3 ple 4 ple 5 EP 1 172 139 According to the invention 4 h/850 C. 112 98 89 88 85 (starting material) 4 h/1100 C. 18 49 34 46 51 24 h/1100 C. 12 45 34 39 37 36 h/1150 C. 20 25 4 h/1200 C. 16 21

Example 6 (According to the Invention)

Composition: 51% Al.SUB.2.O.SUB.3., 14.2% CeO.SUB.2., 34.8% ZrO.SUB.2

Corresponds to Comparative Example 3

(56) A metal salt solution consisting of 55.0 g of a solution of ammonium cerium(IV) nitrate (CeO.sub.2 content 12.90%) and 239.7 g of a solution of zirconyl nitrate (ZrO.sub.2 content 7.26%) was used as the starting material and heated to 90 C.

(57) A suspension consisting of 510.0 g DISPERAL HP 14/7 (boehmite modified with citric acid) (Al.sub.2O.sub.3 content 5%) was adjusted to a pH of 10 by stirring the solids into deionized water and then adding a 24% ammonia solution.

(58) This suspension was added by drops slowly to the metal salt solution and after the addition was completed the pH was adjusted to 8.7 by adding 24% ammonia solution. This mixture was then stirred for 30 minutes at 90 C. Following that the mixture was filtered and the filter residue was washed with deionized water at 60 C. The filter cake was resuspended in deionized water while stirring and was then spray dried (inlet temperature=220 C., outlet temperature=110 C.). The dried material was calcined for four hours at 850 C.

(59) The values from Comparative Example 3 are given in parentheses.

(60) BET after 850 C./4 hours (starting material): 97 m.sup.2/g (107)

(61) BET after 1100 C./2 hours: 62 m.sup.2/g (47)

(62) BET after 1100 C./24 hours: 36 m.sup.2/g (35)

(63) TABLE-US-00003 TABLE 3 Measured surface areas (BET) from Comparative Example 3 and Example 7 after calcining (m.sup.2/g). Comparative Example 3 Example 6 (like WO 2006/070201) (according to the invention) 850 C./4 hours 107 97 (starting material) 2 h/1100 C. 47 62 24 h/1100 C. 35 36

Example 7 (According to the Invention)

Composition: 50% Al.SUB.2.O.SUB.3., 30% CeO.SUB.2., 15% ZrO.SUB.2., 3.5% La.SUB.2.O.SUB.3., 1.5% Y.SUB.2.O.SUB.3

Corresponds to Comparative Examples 4 and 5

(64) A metal salt solution consisting of 116.3 g of a solution of ammonium cerium(IV) nitrate (CeO.sub.2 content=12.90%), 103.3 g of a solution of zirconyl nitrate (ZrO.sub.2 content=7.26%), 12.1 g of a solution of lanthanum nitrate (La.sub.2O.sub.3 content=14.50%) and 4.2 g of a solution of yttrium acetate (Y.sub.2O.sub.3 content=17.80%) and heated to 90 C.

(65) A suspension consisting of 500 g DISPERAL HP 14/7 (boehmite modified with citric acid) (Al.sub.2O.sub.3 content 5%) was adjusted to a pH of 10 by stirring the solids into deionized water and then adding a 24% ammonia solution.

(66) This suspension was added by drops slowly to the metal salt solution and after the addition was completed the pH was adjusted to 8.3 by adding 24% ammonia solution. This mixture was then stirred for 30 minutes at 90 C. Following that the mixture was filtered and the filter residue was washed with deionized water at 60 C. The filter cake was dried for sixteen hours at 120 C. and then calcined for four hours at 850 C.

Example 8 (According to the Invention)

Composition: 50% Al.SUB.2.O.SUB.3., 30% CeO.SUB.2., 15% ZrO.SUB.2., 3.5% La.SUB.2.O.SUB.3., 1.5% Y.SUB.2.O.SUB.3

Corresponds to Comparative Examples 4 and 5

(67) A metal salt solution consisting of 116.3 g of a solution of ammonium cerium(IV) nitrate (CeO.sub.2 content=12.90%), 103.3 g of a solution of zirconyl nitrate (ZrO.sub.2 content=7.26%), 12.1 g of a solution of lanthanum nitrate (La.sub.2O.sub.3 content=14.50%) and 4.2 g of a solution of yttrium acetate (Y.sub.2O.sub.3 content=17.80%) and heated to 90 C.

(68) A suspension consisting of 500 g DISPERAL HP 14/7 (boehmite modified with citric acid) (Al.sub.2O.sub.3 content=5%) was adjusted to a pH of 10 by stirring the solids into deionized water and then adding a 24% ammonia solution. This suspension was added by drops slowly to the metal salt solution and after the addition was completed the pH was adjusted to 9.0 by adding 24% ammonia solution. This mixture was then stirred for 30 minutes at 90 C. Following that the mixture was filtered and the filter residue was washed with deionized water at 60 C. The filter cake was resuspended in deionized water while stirring and was then spray dried (inlet temperature=220 C., outlet temperature=110 C.). The dried material was calcined for four hours at 850 C.

Example 9 (According to the Invention)

Composition: 70% Al.SUB.2.O.SUB.3., 20% CeO.SUB.2., 7% ZrO.SUB.2., 3.0% La.SUB.2.O.SUB.3

(69) A boehmite suspension consisting of 420.0 g DISPERAL HP 14/7 (boehmite modified with citric acid) (Al.sub.2O.sub.3 content=5%) was adjusted to a pH of 10 by stirring the solids into deionized water and then adding a 24% ammonia solution. At 90 C. a metal salt solution consisting of 46.51 g of a solution of ammonium cerium(IV) nitrate (CeO.sub.2 content=12.9%), 30.0 g of a solution of zirconyl nitrate (ZrO.sub.2 content=7.0%) and 6.18 g of a solution of lanthanum nitrate (La.sub.2O.sub.3 content=14.57%) was added by drops slowly to this suspension. The pH was kept constant at 9.0 by adding a 24% ammonia solution at the same time. This mixture was then stirred for 30 minutes at 90 C. Following that the mixture was filtered and the filter residue was washed with deionized water at 60 C. The filter cake was resuspended in deionized water while stirring and then dried for sixteen hours at 120 C. The dried material was next calcined at 850 C.

(70) TABLE-US-00004 TABLE 4 Measured surface areas (BET) from Comparative Examples 4 and 5 and Examples 8-10 in m.sup.2/g. Comparative Comparative Example 4 Calculated* Example 5 Example 7 Example 8 Example 9 4 h/850 C. 130 96 92 96 101 (starting material) 4 h/1200 C. 17 22 (5 h) 23 23 25 40 *Surface areas calculated on the basis of the formulas given in WO2012/067654 A1