Noble metal-free catalyst compositions

Abstract

A composition of formula
Ce.sub.1-a-b-cN.sub.aM.sub.bD.sub.cO.sub.xI
wherein M stands for one or more elements from the group of alkaline metals, except sodium, N is Bi and/or Sb, D is present, or is not present, and if present is selected from one or more of Mg, Ca, Sr, Ba; Y, La, Pr, Nd, Sm, Gd, Er; Fe, Zr, Nb, Al; a is a number within the range of 0<a0.9, b is a number within the range of 0<b0.3, c is a number within the range of 0<c0.2, a plus b plus c is <1, and x is a number within the range of 1.2x2, and its use for exhaust gas aftertreatment systems of Diesel engines, gasoline combustion engines, lean burn engines and power plants.

Claims

1. A composition of formula I:
Ce.sub.1-a-b-cN.sub.aM.sub.bD.sub.cO.sub.xI wherein M stands for one or more elements from the group of alkaline metals, except sodium, N is Bi and/or Sb, D is present, or is not present, and if present is selected from one or more of Mg, Ca, Sr, Ba; Y, La, Pr, Nd, Sm, Gd, Er; Fe, Zr, Nb, Al; a is a number within the range of 0<a0.9, b is a number within the range of 0<b0.3, c is a number within the range of 0<c0.2; a plus b plus c is <1, and x is a number within the range of 1.2x2.

2. A composition of claim 1 wherein D is present.

3. A composition of claim 1, wherein D is Ca, Sr, or Ba.

4. A composition of claim 3, wherein D is Sr.

5. A composition of claim 1, wherein D is Y, Pr, La, or Nd.

6. A composition of claim 5, wherein D is Pr.

7. A composition of claim 1, wherein D is Fe, Zr, Nb, or Al.

8. A composition of claim 7, wherein D is Fe.

9. A composition of claim 7, wherein D is Al.

10. A composition of claim 1, wherein c is a number within the range of 0c0.1.

11. A composition of claim 1 which is of formula II
Ce.sub.1-a-bN.sub.aM.sub.bO.sub.xII wherein M stands for one or more elements from the group of alkaline metals, except sodium N is Bi and/or Sb, a is a number within the range of 0<a0.9, b is a number within the range of 0<b0.3, a plus b is <1, and x is a number within the range of 1.2x2.

12. A composition of claim 11, wherein N is Bi.

13. A composition of claim 1, wherein M is potassium.

14. A composition of claim 11, wherein a is a number within the range of 0.01a0.9.

15. A composition of claim 11, wherein b is a number within the range of 0.01b0.3.

16. A composition of claim 15, wherein b is a number within the range of 0.1b0.2.

17. An exhaust gas after treatment system of a diesel engine, gasoline combustion engine, lean burn engine, or power plant comprising a catalyst that includes the composition of claim 11.

18. A composition of claim 11, wherein M is potassium.

19. A composition of claim 1, which is selected from the group consisting of Bi.sub.0.45Ce.sub.0.45K.sub.0.10O.sub.1.65-1.4, Bi.sub.0.40Ce.sub.0.40K.sub.0.20O.sub.1.4-1.2, Bi.sub.0.30Ce.sub.0.60K.sub.0.10O.sub.1.7-1.4, Bi.sub.0.80Ce.sub.0.10K.sub.0.10O.sub.1.5-1.4, Bi.sub.0.10Ce.sub.0.80K.sub.0.10O.sub.1.8-1.4, Bi.sub.0.4Ce.sub.0.4K.sub.0.1Sr.sub.0.1O.sub.1.55-1.35, Bi.sub.0.4Ce.sub.0.4K.sub.0.1Pr.sub.0.1O.sub.1.6-1.4, and Bi.sub.0.4Ce.sub.0.4K.sub.0.1Fe.sub.0.1O.sub.1.6-1.4.

20. An exhaust gas after treatment system of a diesel engine, gasoline combustion engine, lean burn engine, or power plant comprising a catalyst that includes the composition of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS (FIGS. 1 to 2)

(1) FIG. 1 shows powder x-ray diffraction patter of comparative example 4, reflexs refer to CeO.sub.2 and KNO.sub.3.

(2) FIG. 2 shows powder x-ray diffraction patter of example 1, reflexs refer to Ce.sub.1-xBi.sub.xO.sub.2-x/2, -Bi.sub.2O.sub.3 and Bi.sub.2(CO.sub.3)O.sub.2, no crystalline potassium species is detected

MORE DETAILED DESCRIPTION OF THE INVENTION

(3) The present invention will now be explained in more detail with reference to examples and comparative examples without being limited to these. Temperatures indicated are in degree Celsius ( C.).

(4) Synthesis

EXAMPLE 1

(5) Bi.sub.0.45Ce.sub.0.45K.sub.0.10O.sub.1.65-1.4

(6) Was synthesized via a polymer complex sol-gel method.

(7) A mixture of 50 deionized water, 33.46 ml of ethylene glycol (EG) and 47.285 g citric acid monohydrate (CA) was used as solvent.

(8) The stoichiometric amount of bismuth-(III)-oxide (0.1048 g of Bi.sub.2O.sub.3) was dissolved in 0.1477 ml concentrated nitric acid (69%) and 0.704 ml of the H.sub.2O/EG/CA mixture were added (after the dissolution of Bi.sub.2O.sub.3 a white precipitate may form, which dissolves after adding the H.sub.2O/EG/CA mixture). Cerium-(III)-nitrate hexahydrate (0.1954 g Ce(NO.sub.3).sub.3*6H.sub.2O) was dissolved in 0.842 ml of the H.sub.2O/EG/CA mixture and 9 l concentrated nitric acid (69%) were added. Potassium nitrate (0.0101 g KNO.sub.3) was dissolved in 0.187 ml of the H.sub.2O/EG/CA mixture and 2 l of concentrated nitric acid (69%) were added. The three solutions obtained were mixed and vortexed for 60 minutes via an orbital shaker.

(9) Subsequently solvent of the solutions was evaporated and the evaporation residue obtained was calcined in air. To evaporate the solvent the solutions were heated from room temperature up to 90 C. with a heating rate of 10 C./hour. After a dwell time of 5 hours at 90 C. the mixture was heated up to 200 C. with a heating rate of 5 C./hours. After holding this temperature for 5 hours the sample was heated up to 400 C. with a heating rate of 10 C./hour. The samples were calcined at 400 C. for 5 hours. The calcined oxide powders were cooled to room temperature with a rate of 20 C./hour (fresh samples).

EXAMPLE 2 to 5

(10) The compositions referred to examples 2 to 5 are as disclosed in Tables 1A and 1B below and were prepared analogously to the procedure as disclosed in example 1 but using appropriate starting material and amounts. The quantities of the starting materials used for the preparation according to Examples 2 to 5 are listed in Tables 1A and 1B. A mixture of 50 ml deionized water, 33.46 ml ethylene glycol (EG) and 47.285 g citric acid monohydrate (CA) was used as a solvent

(11) TABLE-US-00001 TABLE 1A H.sub.2O/ Bi.sub.2O.sub.3 HNO.sub.3* EG/CA Ce(NO.sub.3).sub.3*6 Ex. Composition [g] [ml] [ml]* H.sub.2O [g] 2 Bi.sub.0.40Ce.sub.0.40K.sub.0.20O.sub.1.4-1.2 0.0923 0.1313 0.625 0.1737 3 Bi.sub.0.30Ce.sub.0.60K.sub.0.10O.sub.1.7-1.4 0.0699 0.0985 0.469 0.2605 4 Bi.sub.0.80Ce.sub.0.10K.sub.0.10O.sub.1.5-1.4 0.1864 0.2626 1.251 0.0434 5 Bi.sub.0.10Ce.sub.0.80K.sub.0.10O.sub.1.8-1.4 0.0233 0.0328 0.156 0.3474

(12) TABLE-US-00002 TABLE 1B KNO.sub.3 HNO.sub.3** H.sub.2O/EG/CA** Ex. Composition [mg] [l] [ml] 2 Bi.sub.0.40Ce.sub.0.40K.sub.0.20O.sub.1.4-1.2 20.2 12 1.123 3 Bi.sub.0.30Ce.sub.0.60K.sub.0.10O.sub.1.7-1.4 10.1 14 1.310 4 Bi.sub.0.80Ce.sub.0.10K.sub.0.10O.sub.1.5-1.4 10.1 4 0.374 5 Bi.sub.0.10Ce.sub.0.80K.sub.0.10O.sub.1.8-1.4 10.1 18 1.684 *for dissolving Bi.sub.2O.sub.3 **for dissolving other metal salts

EXAMPLE 6

(13) Bi.sub.0.4Ce.sub.0.4K.sub.0.1Sr.sub.0.1O.sub.1.55-1.35

(14) Was synthesized via a polymer complex sol-gel method.

(15) A mixture of 200 ml deionized water, 133.84 ml of ethylene glycol (EG) and 189.14 g citric acid monohydrate (CA) was used as solvent.

(16) The stoichiometric amount of bismuth-(III)-oxide (5.26 g of Bi.sub.2O.sub.3) was dissolved in 11.81 g concentrated nitric acid (69%) and 40.77 g of the H.sub.2O/EG/CA mixture were added (after the dissolution of Bi.sub.2O.sub.3 a white precipitate may form, which dissolves after adding the H.sub.2O/EG/CA mixture). Cerium-(III)-nitrate hexahydrate (9.81 g Ce(NO.sub.3).sub.3*6H.sub.2O), potassium nitrate (0.57 g KNO.sub.3) and strontium carbonate (0.83 g SrCO.sub.3) were dissolved in 59.52 g of the H.sub.2O/EG/CA mixture and 0.85 g concentrated nitric acid (69%) were added. The two solutions obtained were mixed for 60 minutes via a magnetic stirrer. Subsequently solvent of the solutions was evaporated and the evaporation residue obtained was calcined in air. To evaporate the solvent the solutions were heated from room temperature up to 70 C. with a heating rate of 7.5 C./hour. After a dwell time of 24 hours at 70 C. the mixture was heated up to 200 C. with a heating rate of 26 C./hours. After holding this temperature for 24 hours the sample was heated up to 400 C. with a heating rate of 200 C./hour. The samples were calcined at 400 C. for 5 hours. The calcined oxide powders were cooled to room temperature with a rate of 20 C./hour (fresh samples).

EXAMPLE 7

(17) Bi.sub.0.4Ce.sub.0.4K.sub.0.1Pr.sub.0.1O.sub.1.6-1.4

(18) Was synthesized via a polymer complex sol-gel method.

(19) A mixture of 200 ml deionized water, 133.84 ml of ethylene glycol (EG) and 189.14 g citric acid monohydrate (CA) was used as solvent.

(20) The stoichiometric amount of bismuth-(III)-oxide (5.09 g of Bi.sub.2O.sub.3) was dissolved in 11.81 g concentrated nitric acid (69%) and 39.12 g of the H.sub.2O/EG/CA mixture were added (after the dissolution of Bi.sub.2O.sub.3 a white precipitate may form, which dissolves after adding the H.sub.2O/EG/CA mixture). Cerium-(III)-nitrate hexahydrate (9.48 g Ce(NO.sub.3).sub.3*6H.sub.2O), potassium nitrate (0.55 g KNO.sub.3) and praseodymium nitrate hexahydrate (2.37 g Pr(NO.sub.3).sub.3*6H.sub.2O) were dissolved in 59.52 g of the H.sub.2O/EG/CA mixture and 0.85 g concentrated nitric acid (69%) were added. The two solutions obtained were mixed for 60 minutes via an magnetic stirrer. Subsequently solvent of the solutions was evaporated and the evaporation residue obtained was calcined in air. To evaporate the solvent the solutions were heated from room temperature up to 70 C. with a heating rate of 7.5 C./hour. After a dwell time of 24 hours at 70 C. the mixture was heated up to 200 C. with a heating rate of 26 C./hours. After holding this temperature for 24 hours the sample was heated up to 400 C. with a heating rate of 200 C./hour. The samples were calcined at 400 C. for 5 hours. The calcined oxide powders were cooled to room temperature with a rate of 20 C./hour (fresh samples).

EXAMPLE 8

(21) Bi.sub.0.4Ce.sub.0.4K.sub.0.1Fe.sub.0.1O.sub.1.6-1.4

(22) Was synthesized via a polymer complex sol-gel method.

(23) A mixture of 200 ml deionized water, 133.84 ml of ethylene glycol (EG) and 189.14 g citric acid monohydrate (CA) was used as solvent.

(24) The stoichiometric amount of bismuth-(III)-oxide (5.33 g of Bi.sub.2O.sub.3) was dissolved in 11.81 g concentrated nitric acid (69%) and 41.03 g of the H.sub.2O/EG/CA mixture were added (after the dissolution of Bi.sub.2O.sub.3 a white precipitate may form, which dissolves after adding the H.sub.2O/EG/CA mixture). Cerium-(III)-nitrate hexahydrate (9.94 g Ce(NO.sub.3).sub.3*6H.sub.2O), potassium nitrate (0.58 g KNO.sub.3) and iron (III) nitrate nonahydrate (2.31 g Fe(NO.sub.3).sub.3*9H.sub.2O) were dissolved in 59.52 g of the H.sub.2O/EG/CA mixture and 0.85 g concentrated nitric acid (69%) were added. The two solutions obtained were mixed for 60 minutes via an magnetic stirrer. Subsequently solvent of the solutions was evaporated and the evaporation residue obtained was calcined in air. To evaporate the solvent the solutions were heated from room temperature up to 70 C. with a heating rate of 7.5 C./hour. After a dwell time of 24 hours at 70 C. the mixture was heated up to 200 C. with a heating rate of 26 C./hours. After holding this temperature for 24 hours the sample was heated up to 400 C. with a heating rate of 200 C./hour. The samples were calcined at 400 C. for 5 hours. The calcined oxide powders were cooled to room temperature with a rate of 20 C./hour (fresh samples).

COMPARATIVE EXAMPLE 1

(25) Bi.sub.0.45Ce.sub.0.45Na.sub.0.10O.sub.1.65-1.4

(26) Was synthesized via a polymer complex sol-gel method.

(27) A mixture of 50 ml deionized water, 33.46 ml of ethylene glycol (EG) and 47.285 g citric acid monohydrate (CA) was used as solvent.

(28) The stoichiometric amount of bismuth-(III)-oxide (0.1048 g of Bi.sub.2O.sub.3) was dissolved in 0.1477 ml concentrated nitric acid (69%) and 0.704 ml of the H.sub.2O/EG/CA mixture were added (after the dissolution of Bi.sub.2O.sub.3 a white precipitate may form, which dissolves after adding the H.sub.2O/EG/CA mixture). Cerium-(III)-nitrate hexahydrate (0.1954 g Ce(NO.sub.3).sub.3*6H.sub.2O) was dissolved in 0.842 ml of the H.sub.2O/EG/CA mixture and 9 l concentrated nitric acid (69%) were added. Sodium nitrate (0.0085 g NaNO.sub.3) was dissolved in 0.187 ml of the H.sub.2O/EG/CA mixture and 2 l of concentrated nitric acid (69%) were added. The three solutions obtained were mixed and vortexed for 60 minutes via an orbital shaker. Subsequently solvent of the solutions was evaporated and the evaporation residue obtained was calcined in air. To evaporate the solvent the solutions were heated from room temperature up to 70 C. with a heating rate of 7.5 C./hour. After a dwell time of 24 hours at 70 C. the mixture was heated up to 200 C. with a heating rate of 26 C./hours. After holding this temperature for 24 hours the sample was heated up to 400 C. with a heating rate of 200 C./hour. The samples were calcined at 400 C. for 5 hours. The calcined oxide powders were cooled to room temperature with a rate of 20 C./hour (fresh samples).

COMPARATIVE EXAMPLE 2

(29) Bi.sub.10Ce.sub.80Sr.sub.10O.sub.x (EP 2 438 984 A1, Example 2)

(30) The metal nitrate salts (0.5988 g of Ce(NO.sub.3).sub.3*6H.sub.2O, 0.0836 g of Bi(NO.sub.3).sub.3*5H.sub.2O and 0.0365 g of Sr(NO.sub.3).sub.2) were mixed resulting in a molar ratio of Ce/Bi/Sr=0.8/0.1/0.1 and 5 ml deionized water were added. After the dissolution of the nitrate salts, a white precipitate had formed and 3 ml of concentrated nitric acid (69%) were added. The mixture obtained was stirred until a clear solution was obtained. To the solution obtained again water was added so that the total volume of the final solution was 50 ml. To the solution obtained 40 ml of the precipitating agent (1 molar ammonium carbonate aqueous solution) were added slowly while stirring. The suspension obtained was further stirred for 30 minutes. A precipitate was obtained, filtered, washed with deionized water and dried at 125 C. for 15 hours in air atmosphere. The dried solid was calcined at 400 C. for 5 hours.

COMPARATIVE EXAMPLE 3

(31) Bi.sub.10Ce.sub.50Pr.sub.40O.sub.x (EP 2 210 861 B1, Example 1)

(32) First, 0.6809 g of praseodymium oxide (Pr.sub.6O.sub.11, 99.9%, ABCR) were dissolved in 4.5 ml concentrated nitric acid (69%). Then, 2.1711 g of cerium nitrate hexahydrate (Ce(NO.sub.3).sub.3*6H.sub.2O, 99.9%, ChemPur) and 0.485 bismuth nitrate pentahydrate (Bi(NO.sub.3).sub.3*5H.sub.2O, 99.99%, Sigma-Aldrich) were added to the nitric acid solution of Pr resulting in a molar ratio of Ce/Bi/Pr=0.5/0.1/0.4. To the solution obtained 45 ml of the precipitating agent (1 molar ammonium carbonate aqueous solution) were added slowly, while stirring for 30 minutes. The precipitate obtained was filtered and washed with deionized water, dried at 125 C. for 15 hours in air. The dried solid obtained was calcined at 400 C. for 5 hours.

COMPARATIVE EXAMPLE 4

(33) Ce.sub.50K.sub.50O.sub.x (WO 2006/04482)

(34) The comparative example 3 was prepared by melting the corresponding nitrate salts. For this comparative example 1.0856 g of Ce(NO.sub.3).sub.3*6H.sub.2O and 0.2528 g of KNO.sub.3 were manually mixed. The mixture obtained was heated from room temperature up to 350 C. with a heating rate of 50 C./hour. The temperature of 350 C. was kept constant for 12 hours and subsequently decreased again to room temperature with a rate of 120 C./hours. The solid obtained was calcined at 400 C. for 5 hours.

COMPARATIVE EXAMPLE 5

(35) Ce.sub.50K.sub.50O.sub.x (WO 2006/044822 A1)

(36) Was synthesized by dissolving 4.3422 g Ce(NO.sub.3).sub.3*6H.sub.2O in 10 ml of deionized water and adding 0.6910 g of K.sub.2CO.sub.3 to the aqueous Ce solution. The solution obtained was reduced in volume by evaporation at 120 C. for 24 hours in air. The dried solid obtained was calcined at 400 C. for 5 hours.

COMPARATIVE EXAMPLE 6

(37) Ce.sub.66.7K.sub.33.3O.sub.x (WO 2006/044822 A1)

(38) Was prepared by melting the corresponding nitrate salts. For this comparative example 1.7369 g of Ce(NO.sub.3).sub.3*6H.sub.2O and 0.2022 g of KNO.sub.3 were manually mixed. The mixture obtained was heated from room temperature up to 350 C. with a heating rate of 50 C./hour. The temperature of 350 C. was kept constant for 12 hours and subsequently decreased again to room temperature with a rate of 120 C./hour. The solid obtained was calcined at 400 C. for 5 hours.

COMPARATIVE EXAMPLE 7

(39) Ce.sub.66.7K.sub.33.3O.sub.x (WO 2006/044822 A1)

(40) Was synthesized by dissolving 4.3422 g of Ce(NO.sub.3).sub.3*6H.sub.2O in 10 ml of deionized water and adding 0.3455 g of K.sub.2CO.sub.3 to the aqueous Ce solution. The solution obtained was reduced in volume by evaporation at 120 C. for 24 hours in air. The dried solid obtained was calcined at 400 C. for 5 hours.

COMPARATIVE EXAMPLE 8

(41) Bi.sub.0.45Ce.sub.0.45Sr.sub.0.1O.sub.x

(42) Was synthesized via a polymer complex sol-gel method.

(43) A mixture of 200 ml deionized water, 133.84 ml of ethylene glycol (EG) and 189.14 g citric acid monohydrate (CA) was used as solvent.

(44) The stoichiometric amount of bismuth-(III)-oxide (5.17 g of Bi.sub.2O.sub.3) was dissolved in 11.81 g concentrated nitric acid (69%) and 39.77 g of the H.sub.2O/EG/CA mixture were added (after the dissolution of Bi.sub.2O.sub.3 a white precipitate may form, which dissolves after adding the H.sub.2O/EG/CA mixture). Cerium-(III)-nitrate hexahydrate (9.64 g Ce(NO.sub.3).sub.3*6H.sub.2O) and strontium carbonate (0.71 g SrCO.sub.3) were dissolved in 59.52 g of the H.sub.2O/EG/CA mixture and 0.85 g concentrated nitric acid (69%) were added. The two solutions obtained were mixed for 60 minutes via an magnetic stirrer. Subsequently solvent of the solutions was evaporated and the evaporation residue obtained was calcined in air. To evaporate the solvent the solutions were heated from room temperature up to 70 C. with a heating rate of 7.5 C./hour. After a dwell time of 24 hours at 70 C. the mixture was heated up to 200 C. with a heating rate of 26 C./hours. After holding this temperature for 24 hours the sample was heated up to 400 C. with a heating rate of 200 C./hour. The samples were calcined at 400 C. for 5 hours. The calcined oxide powders were cooled to room temperature with a rate of 20 C./hour (fresh samples).

COMPARATIVE EXAMPLE 9

(45) Bi.sub.0.45Ce.sub.0.45Pr.sub.0.1O.sub.x

(46) Was synthesized via a polymer complex sol-gel method.

(47) A mixture of 200 ml deionized water, 133.84 ml of ethylene glycol (EG) and 189.14 g citric acid monohydrate (CA) was used as solvent.

(48) The stoichiometric amount of bismuth-(III)-oxide (5.23 g of Bi.sub.2O.sub.3) was dissolved in 11.81 g concentrated nitric acid (69%) and 40.26 g of the H.sub.2O/EG/CA mixture were added (after the dissolution of Bi.sub.2O.sub.3 a white precipitate may form, which dissolves after adding the H.sub.2O/EG/CA mixture). Cerium-(III)-nitrate hexahydrate (9.38 g Ce(NO.sub.3).sub.3*6H.sub.2O) and praseodymium nitrate hexahydrate (2.09 g Pr(NO.sub.3).sub.3*6H.sub.2O) were dissolved in 59.52 g of the H.sub.2O/EG/CA mixture and 0.85 g concentrated nitric acid (69%) were added. The two solutions obtained were mixed for 60 minutes via an magnetic stirrer. Subsequently solvent of the solutions was evaporated and the evaporation residue obtained was calcined in air. To evaporate the solvent the solutions were heated from room temperature up to 70 C. with a heating rate of 7.5 C./hour. After a dwell time of 24 hours at 70 C. the mixture was heated up to 200 C. with a heating rate of 26 C./hours. After holding this temperature for 24 hours the sample was heated up to 400 C. with a heating rate of 200 C./hour. The samples were calcined at 400 C. for 5 hours. The calcined oxide powders were cooled to room temperature with a rate of 20 C./hour (fresh samples).

COMPARATIVE EXAMPLE 10

(49) Bi.sub.0.45Ce.sub.0.45Fe.sub.0.1O.sub.x

(50) Was synthesized via a polymer complex sol-gel method.

(51) A mixture of 200 ml deionized water, 133.84 ml of ethylene glycol (EG) and 189.14 g citric acid monohydrate (CA) was used as solvent.

(52) The stoichiometric amount of bismuth-(III)-oxide (5.03 g of Bi.sub.2O.sub.3) was dissolved in 11.81 g concentrated nitric acid (69%) and 38.7 g of the H.sub.2O/EG/CA mixture were added (after the dissolution of Bi.sub.2O.sub.3 a white precipitate may form, which dissolves after adding the H.sub.2O/EG/CA mixture). Cerium-(III)-nitrate hexahydrate (9.38 g Ce(NO.sub.3).sub.3*6H.sub.2O) and iron (III) nitrate nonahydrate (1.94 g Fe(NO.sub.3).sub.3*9H.sub.2O) were dissolved in 59.52 g of the H.sub.2O/EG/CA mixture and 0.85 g concentrated nitric acid (69%) were added. The two solutions obtained were mixed for 60 minutes via an magnetic stirrer. Subsequently solvent of the solutions was evaporated and the evaporation residue obtained was calcined in air. To evaporate the solvent the solutions were heated from room temperature up to 70 C. with a heating rate of 7.5 C./hour. After a dwell time of 24 hours at 70 C. the mixture was heated up to 200 C. with a heating rate of 26 C./hours. After holding this temperature for 24 hours the sample was heated up to 400 C. with a heating rate of 200 C./hour. The samples were calcined at 400 C. for 5 hours. The calcined oxide powders were cooled to room temperature with a rate of 20 C./hour (fresh samples).

(53) Results of Catalytic Testing

(54) Table 2 shows the PM removal efficiency, measured with method A, of the Cerium-Bismuth-Alkaline compositions of the present invention prepared according to examples 1 to 6, as well as for the comparative examples 1 and 2 in the fresh status (calcined at 400 C./2 hours) and after thermal aging of the powders at 800 C./2 hours.

(55) TABLE-US-00003 TABLE 2 T.sub.50 fresh T.sub.50 aged Sample Composition [ C.] [ C.] Example 1 Bi.sub.0.45Ce.sub.0.45K.sub.0.10O.sub.1.65-1.4 515 535 Example 2 Bi.sub.0.40Ce.sub.0.40K.sub.0.20O.sub.1.4-1.2 510 519 Example 3 Bi.sub.0.30Ce.sub.0.60K.sub.0.10O.sub.1.7-1.4 520 536 Example 4 Bi.sub.0.80Ce.sub.0.10K.sub.0.10O.sub.1.5-1.4 498 563 Example 5 Bi.sub.0.10Ce.sub.0.80K.sub.0.10O.sub.1.8-1.4 535 547 Comparative Bi.sub.0.45Ce.sub.0.45Na.sub.0.10O.sub.1.65-1.4 569 584 Example 1 Comparative Bi.sub.10Ce.sub.80Sr.sub.10O.sub.x 608 627 Example 2 Comparative Bi.sub.10Ce.sub.50Pr.sub.40O.sub.x 606 634 Example 3

(56) The catalytic test results showed that all the materials of the examples 1 to 5 have a lower T.sub.50-value after thermal aging and in the fresh status than the materials of comparative examples 1, 2 and 3.

(57) Results of Catalytic Testing After Hydrothermal Treatment:

(58) Table 3 below shows the PM removal efficiency, measured with method A, of three compositions of the present invention and those of compositions of the comparative examples 3, 4, 5 and 6, both in the fresh status as well as after hydrothermal treatment. The compositions of comparative examples 3 to 6 show an excellent catalytic activity in the fresh status. In contrast to that, however, the compositions of the comparative examples lose their catalytic activity after hydrothermal aging in contrast to the examples of the present invention, which still show catalytic activity.

(59) TABLE-US-00004 TABLE 3 T.sub.50 fresh T.sub.50 hydrothermally Sample Composition [ C.] aged [ C.] Example 1 Bi.sub.0.45Ce.sub.0.45K.sub.0.10O.sub.1.65-1.4 515 582 Example 2 Bi.sub.0.40Ce.sub.0.40K.sub.0.20O.sub.1.4-1.2 510 595 Example 3 Bi.sub.0.30Ce.sub.0.60K.sub.0.10O.sub.1.7-1.4 520 584 Comparative Ce.sub.50K.sub.50O.sub.x 468 655 Example 4 Comparative Ce.sub.50K.sub.50O.sub.x 470 655 Example 5 Comparative Ce.sub.70K.sub.30O.sub.x 464 672 Example 6 Comparative Ce.sub.70K.sub.30O.sub.x 524 678 Example 7
Effect of Potassium Doping of Different CeBi-M-mixed Metal Oxides:

(60) Table 4 below shows the effect of potassium doping of three different Ce-Bi-M-mixed metal oxides for PM removal efficiency, measured with method B. All compositions doped with potassium are more catalytic active for the soot oxidation than the undoped compositions both in the fresh status as well as after thermal treatment.

(61) TABLE-US-00005 TABLE 4 T.sub.50 fresh T.sub.50 aged Sample Composition [ C.] [ C.] Example 1 Bi.sub.0.45Ce.sub.0.45K.sub.0.10O.sub.1.65-1.4 426 479 Example 6 Bi.sub.0.4Ce.sub.0.4K.sub.0.1Sr.sub.0.1O.sub.1.55-1.35 414 490 Example 7 Bi.sub.0.4Ce.sub.0.4K.sub.0.1Pr.sub.0.1O.sub.1.6-1.4 437 498 Example 8 Bi.sub.0.4Ce.sub.0.4K.sub.0.1Fe.sub.0.1O.sub.1.6-1.4 414 507 Comparative Bi.sub.45Ce.sub.45Sr.sub.10O.sub.x 518 525 Example 8 Comparative Bi.sub.45Ce.sub.45Pr.sub.10O.sub.x 458 508 Example 9 Comparative Bi.sub.45Ce.sub.45Fe.sub.10O.sub.x 490 515 Example 10