Diesel oxidation catalyst containing manganese

Abstract

The present invention relates to a diesel oxidation catalyst, which comprises a carrier body having a length L extending between a first end face a and a second end face b and a catalytically active material zone A arranged on the carrier body, wherein the material zone A contains palladium and platinum on a manganese-containing carrier oxide, wherein the carrier oxide consists of a carrier oxide component A and a carrier oxide component B and the carrier oxide component B consists of manganese and/or a manganese compound and is present in an amount of 5 to 15 wt. %, calculated as MnO.sub.2 and based on the total weight of the manganese-containing carrier oxide.

Claims

1. A diesel oxidation catalyst, which comprises a carrier body having a length L extending between a first end face a and a second end face b and a catalytically active material zone A arranged on the carrier body, wherein the material zone A contains palladium and platinum supported on a manganese-containing carrier oxide, wherein the manganese-containing carrier oxide includes a carrier oxide component A and a carrier oxide component B and the carrier oxide component B includes a manganese and/or a manganese compound and is present in an amount of 5 to 15 wt. %, calculated as MnO.sub.2 and based on the total weight of the manganese-containing carrier oxide, and wherein material zone A is free of zeolites.

2. Diesel oxidation catalyst according to claim 1, wherein the carrier oxide component A is selected from the series consisting of aluminum oxide, doped aluminum oxide, silicon oxide, titanium dioxide and mixed oxides containing one or more of said oxides.

3. Diesel oxidation catalyst according to claim 1, wherein the carrier oxide component A is doped aluminum oxide.

4. Diesel oxidation catalyst according to claim 1, wherein the carrier oxide component A is a mixed oxide comprising aluminum oxide and silicon oxide or a silicon-oxide-doped aluminum oxide.

5. Diesel oxidation catalyst according to claim 1, wherein the carrier oxide component B is present in an amount of from 8 to 12 wt. %, calculated as MnO.sub.2 and based on the total weight of the manganese-containing carrier oxide.

6. Diesel oxidation catalyst according to claim 1 wherein the ratio of platinum to palladium is Pt:Pd1.

7. Diesel oxidation catalyst according to claim 1, wherein the platinum and palladium in material zone A is supported exclusively on the manganese-containing carrier oxide.

8. Diesel oxidation catalyst according to claim 1, consisting of the carrier body and material zone A.

9. Diesel oxidation catalyst according to claim 1, further comprising material zone B.

10. Diesel oxidation catalyst according to claim 9, wherein material zone B lies directly on the carrier body and material zone A on material zone B.

11. Diesel oxidation catalyst according to claim 9 wherein material zone B comprises noble metal on a carrier oxide selected from the group consisting of aluminum oxide, doped aluminum oxide, silicon oxide, titanium dioxide and mixed oxides containing one or more of said oxides.

12. Diesel oxidation catalyst according to claim 9, wherein material zone B contains zeolite selected from the series consisting of beta zeolite, ZSM-5, zeolite Y or mixtures thereof.

13. Method for treating diesel exhaust gases, wherein the diesel exhaust gas is passed over a diesel oxidation catalyst according to claim 1.

14. A device for purifying exhaust gases from diesel engines, having a diesel oxidation catalyst according to claim 1.

15. An exhaust gas purification system comprising the diesel oxidation catalyst according to claim 1 and one or both of a diesel particulate filter and an SCR.

16. Diesel oxidation catalyst according to claim 1 wherein there is a weight ratio of X:Y:Z with X being aluminum oxide, Y being one of lanthanum oxide and silicon oxide, and Z being a manganese and/or a manganese compound, and wherein X is from 85 to 95 in weight percent; Y is from 0 to 5 in weight percent; and Z is from 5 to 10 in weight percent calculated as MnO.sub.2.

17. Diesel oxidation catalyst according to claim 16 wherein Y is from 3.6 to 5 in weight percent and Z is manganese oxide of 5 to 10 in weight percent calculated as MnO.sub.2.

18. Diesel oxidation catalyst according to claim 1 wherein material zone A is the sole catalytically active material zone on the diesel oxidation catalyst.

19. A diesel oxidation catalyst, which comprises a carrier body having a length L extending between a first end face a and a second end face b and a catalytically active material zone A arranged on the carrier body, wherein the material zone A contains palladium and platinum supported on a manganese-containing carrier oxide, wherein the manganese-containing carrier oxide includes a carrier oxide component A and a carrier oxide component B, and the carrier oxide component B includes a manganese and/or a manganese compound and is present in an amount of 5 to 15 wt. %, calculated as MnO2 and based on the total weight of the manganese-containing carrier oxide, and wherein material zone A extends over a material zone B supported by the carrier body, and the material zone B includes zeolite, and wherein material zone A is free of zeolites.

Description

(1) The invention is explained in the following examples and figures.

(2) FIG. 1a shows the NO.sub.2/NO.sub.x ratio of the C5 catalyst and the CC3 comparison catalyst measured by means of exhaust gas mixture III (10% O.sub.2, 250 ppm CO, 750 ppm NO, 7.5% H.sub.2O, 7% CO.sub.2 and balance N.sub.2) after aging at 650 C. for 16 hours.

(3) FIG. 1b shows the NO.sub.2/NO.sub.x ratio of the C5 catalyst and the CC3 comparison catalyst measured by means of exhaust gas mixture II (6% O.sub.2, 350 ppm CO, 270 ppm NO, 180 ppm C.sub.3H.sub.6, 90 ppm C.sub.3H.sub.8, 116 ppm H.sub.2, 5% H.sub.2O, 10.7% CO.sub.2 and balance N.sub.2) after aging at 650 C. for 16 hours.

(4) FIG. 2a shows the NO.sub.2/NO.sub.x ratio of the C6 and C7 catalysts and the CC4 comparison catalyst measured by means of exhaust gas mixture III (10% O.sub.2, 250 ppm CO, 750 ppm NO, 7.5% H.sub.2O, 7% CO.sub.2 and balance N.sub.2) after aging at 650 C. for 16 hours.

(5) FIG. 2b shows the NO.sub.2/NO.sub.x ratio of the C6 and C7 catalysts and the CC3 comparison catalyst measured by means of exhaust gas mixture II (6% O.sub.2, 350 ppm CO, 270 ppm NO, 180 ppm C.sub.3H.sub.6, 90 ppm C.sub.3H.sub.8, 116 ppm H.sub.2, 5% H.sub.2O, 10.7% CO.sub.2 and balance N.sub.2) after aging at 650 C. for 16 hours.

(6) FIG. 3a shows the NO.sub.2/NO.sub.x ratio of the C8 and C9 catalysts and the CC5 comparison catalyst measured by means of exhaust gas mixture III (10% O.sub.2, 250 ppm CO, 750 ppm NO, 7.5% H.sub.2O, 7% CO.sub.2 and balance N.sub.2) after aging at 650 C. for 16 hours.

(7) FIG. 3b shows the NO.sub.2/NO.sub.x ratio of the C8 and C9 catalysts and the CC5 comparison catalyst measured by means of exhaust gas mixture II (6% O.sub.2, 350 ppm CO, 270 ppm NO, 180 ppm C.sub.3H.sub.6, 90 ppm C.sub.3H.sub.8, 116 ppm H.sub.2, 5% H.sub.2O, 10.7% CO.sub.2 and balance N.sub.2) after aging at 650 C. for 16 hours.

EXAMPLE 1

(8) a) A coating suspension was prepared, which contained 1.36 g/l platinum, 0.91 g/l palladium, 67.8 g/l of a silicon dioxide-doped aluminum oxide and 26.0 g/l beta zeolite, and was coated by means of a conventional method onto a commercially available cordierite flow-through honeycomb body.

(9) b) 35 g/l of an aluminum oxide doped with lanthanum oxide and manganese oxide with a surface area of approx. 160 m.sup.2/g was moistened with an aqueous solution containing 1.9 g/l platinum in the form of tetraammineplatinum acetate and 0.32 g/l palladium in the form of tetraamminepalladium acetate such that the pores of the aluminum oxide were filled but the powder remained free-flowing. The weight ratio of aluminum oxide, lanthanum oxide and manganese oxide in the doped aluminum oxide was 91:4:5. To fix the noble metal, the moist powder was dried at 120 C. for eight hours and calcined at 300 C. for 4 hours. The resulting powder was then suspended in water and ground to a particle size of D.sub.90<20 micrometers.

(10) c) The coating suspension obtained in step b) was coated onto the catalyst obtained in step a) by means of a conventional method.

(11) The catalyst thus obtained is referred to below as C1.

EXAMPLE 2

(12) Example 1 was repeated with the difference that an aluminum oxide doped with lanthanum oxide and manganese oxide and having a surface area of about 150 m.sup.2/g and a weight ratio of aluminum oxide, lanthanum oxide and manganese oxide of 86:4:10 was used.

(13) The catalyst thus obtained is referred to below as C2.

COMPARATIVE EXAMPLE 1

(14) Example 1 was repeated with the difference that an aluminum oxide doped with lanthanum oxide and having a surface area of about 150 m.sup.2/g and a weight ratio of aluminum oxide and lanthanum oxide of 96:4 was used.

(15) The catalyst thus obtained is referred to below as CC1.

EXAMPLE 3

(16) Example 1 was repeated with the difference that an aluminum oxide doped with silicon oxide and manganese oxide and having a surface area of about 180 m.sup.2/g and a weight ratio of aluminum oxide, silicon oxide and manganese oxide of 90:5:5 was used.

(17) The catalyst thus obtained is referred to below as C3.

EXAMPLE 4

(18) Example 1 was repeated with the difference that an aluminum oxide doped with silicon oxide and manganese oxide and having a surface area of about 170 m.sup.2/g and a weight ratio of aluminum oxide, silicon oxide and manganese oxide of 85:5:10 was used.

(19) The catalyst thus obtained is referred to below as C4.

COMPARATIVE EXAMPLE 2

(20) Example 1 was repeated with the difference that an aluminum oxide doped with silicon oxide and having a surface area of about 150 m.sup.2/g and a weight ratio of aluminum oxide and silicon oxide of 95:5 was used.

(21) The catalyst thus obtained is referred to below as CC2.

COMPARATIVE EXPERIMENTS I

(22) a) Cores were taken from the catalysts C1, C2, CC1, C3, C4 and CC2 and hydrothermally aged in an oven at 800 C. for 16 hours (10% H.sub.2O, 10% O.sub.2, balance N.sub.2).

(23) b) The CO T.sub.50 value was determined by means of the extracted and aged cores. In addition, in a laboratory reactor an artificial exhaust gas comprising 6% O.sub.2, 350 ppm CO, 270 ppm NO, 180 ppm C.sub.3H.sub.6, 90 ppm C.sub.3H.sub.8, 10% H.sub.2O, 10% CO.sub.2 and balance N.sub.2 (exhaust gas mixture I) was conducted at 2000 L/h through the cores and the temperature with 15 C./min was increased from 75 C. to 500 C.t. In so doing, the temperature at which 50% of the carbon monoxide is reacted was determined.

(24) The results can be taken from Table 1.

(25) TABLE-US-00001 Proportion by weight of MnO.sub.2 in the carrier oxide CO T.sub.50 [ C.] C1 5 125 C2 10 121 CC1 0 145 C3 5 133 C4 10 135 CC2 0 141

EXAMPLE 5

(26) A coating suspension was prepared, which contained 0.61 g/l platinum, 0.10 g/l palladium, 105.29 g/l of an aluminum oxide doped with silicon dioxide and manganese dioxide, and was coated by means of a conventional method onto a commercially available cordierite flow-through honeycomb body. The weight ratio of aluminum oxide, silicon oxide and manganese oxide in the doped aluminum oxide was 85:5:10.

(27) The catalyst thus obtained is referred to below as C5.

COMPARATIVE EXAMPLE 3

(28) Example 5 was repeated with the difference that an aluminum oxide doped with silicon oxide and having a surface area of about 150 m.sup.2/g and a weight ratio of aluminum oxide and silicon oxide of 95:5 was used.

(29) The catalyst thus obtained is referred to below as CC3.

EXAMPLE 6

(30) Example 5 was repeated with the difference that an aluminum oxide doped with lanthanum oxide and manganese oxide and having a surface area of about 145 m.sup.2/g and a weight ratio of aluminum oxide, lanthanum oxide and manganese oxide of 86:4:10 was used.

(31) The catalyst thus obtained is referred to below as C6.

EXAMPLE 7

(32) 90 g/l of a lanthanum oxide-doped aluminum oxide having a surface area of about 170 m.sup.2/g was moistened with an aqueous solution containing 10 g/l manganese oxide in the form of manganese acetate tetrahydrate in such a way that the pores of the aluminum oxide were filled but the powder remained free-flowing. The weight ratio of aluminum oxide, lanthanum oxide and manganese oxide in the doped alumina was 86.4:3.6:10. To fix the manganese (as manganese oxide), the moist powder was dried at 120 C. for eight hours and calcined at 300 C. for 4 hours. The resulting powder was then suspended in water and ground to a particle size of D90<20 micrometers.

(33) A coating suspension containing 0.61 g/l platinum, 0.10 g/l palladium and 105.29 g/l of the aforementioned powder was prepared from the powder thus obtained and coated onto a commercially available cordierite flow-through honeycomb body by means of a conventional method.

(34) The catalyst thus obtained is referred to below as C7.

COMPARATIVE EXAMPLE 4

(35) Example 5 was repeated with the difference that an aluminum oxide doped with lanthanum oxide and having a surface area of about 190 m.sup.2/g and a weight ratio of aluminum oxide and lanthanum oxide of 96:4 was used.

(36) The catalyst thus obtained is referred to below as CC4.

EXAMPLE 8

(37) 95 g/l of a pure aluminum oxide with a surface area of approx. 140 m.sup.2/g was moistened with an aqueous solution containing 5 g/l manganese oxide in the form of manganese acetate tetrahydrate such that the pores of the aluminum oxide were filled but the powder remained free-flowing. The weight ratio of aluminum oxide and manganese oxide in the doped aluminum oxide was 95:5. To fix the manganese (as manganese oxide), the moist powder was dried at 120 C. for eight hours and calcined at 300 C. for 4 hours. The resulting powder was then suspended in water and ground to a particle size of D90<20 micrometers.

(38) A coating suspension containing 0.61 g/l platinum, 0.10 g/l palladium and 105.29 g/l of the aforementioned powder was prepared from the powder thus obtained and coated onto a commercially available cordierite flow-through honeycomb body by means of a conventional method.

(39) The catalyst thus obtained is referred to below as C8.

EXAMPLE 9

(40) 90 g/l of a pure aluminum oxide with a surface area of approx. 140 m.sup.2/g was moistened with an aqueous solution containing 10 g/l manganese oxide in the form of manganese acetate tetrahydrate such that the pores of the aluminum oxide were filled but the powder remained free-flowing. The weight ratio of aluminum oxide and manganese oxide in the doped aluminum oxide was 90:10. To fix the manganese (as manganese oxide), the moist powder was dried at 120 C. for eight hours and calcined at 300 C. for 4 hours. The resulting powder was then suspended in water and ground to a particle size of D90<20 micrometers.

(41) A coating suspension containing 0.61 g/l platinum, 0.10 g/l palladium and 105.29 g/l of the aforementioned powder was prepared from the powder thus obtained and coated onto a commercially available cordierite flow-through honeycomb body by means of a conventional method.

(42) The catalyst thus obtained is referred to below as C9.

COMPARATIVE EXAMPLE 5

(43) Example 5 was repeated with the difference that a pure aluminum oxide having a surface area of about 140 m.sup.2/g was used.

(44) The catalyst thus obtained is referred to below as CC5.

COMPARATIVE EXPERIMENTS II

(45) a) Two cores were extracted from each of the catalysts C5, CC3, C6, C7, CC4, C8, C9 and CC5 and hydrothermally aged in an oven at 650 C. for 16 hours (10% H.sub.2O, 10% O.sub.2, balance N.sub.2).

(46) b) The CO T.sub.50 value was determined by means of the extracted and aged cores. In addition, in a laboratory reactor an artificial exhaust gas comprising 6% O.sub.2, 350 ppm CO, 270 ppm NO, 180 ppm C.sub.3H.sub.6, 90 ppm C.sub.3H.sub.8, 116 ppm H.sub.2, 5% H.sub.2O, 10.7% CO.sub.2 and balance N.sub.2 (exhaust gas mixture II) was conducted at 1930 L/h through the cores and the temperature with 15 C./min was increased from 75 C. to 500 C. In so doing, the temperature at which 50% of the carbon monoxide is reacted was determined.

(47) c) In a further test the method according to b) was repeated, but with an artificial exhaust gas comprising 10% O.sub.2, 250 ppm CO, 750 ppm NO, 7.5% H.sub.2O, 7% CO.sub.2 and balance N.sub.2 (exhaust gas mixture III).

(48) d) The comparative experiments according to a) and b) were repeated with cores aged for 16 hours at 750 C.

(49) The results are shown in Tables 2 to 5.

(50) TABLE-US-00002 TABLE 2 Aging 16 h 650 C., exhaust gas mixture II Proportion by weight of MnO.sub.2 in the carrier oxide CO T.sub.50 [ C.] C5 10 142 CC3 0 162 C6 10 155 C7 10 145 CC4 0 172 C8 5 154 C9 10 150 CC5 0 180

(51) TABLE-US-00003 TABLE 3 Aging 16 h 750 C., exhaust gas mixture II Proportion by weight of MnO.sub.2 in the carrier oxide CO T.sub.50 [ C.] C5 10 151 CC3 0 168 C6 10 164 C7 10 162 CC4 0 179 C8 5 150 C9 10 155 CC5 0 188

(52) TABLE-US-00004 TABLE 4 Aging 16 h 650 C., exhaust gas mixture III Proportion by weight of MnO.sub.2 in the carrier oxide CO T.sub.50 [ C.] C5 10 119 CC3 0 155 C6 10 132 C7 10 122 CC4 0 153 C8 5 129 C9 10 124 CC5 0 162

(53) TABLE-US-00005 TABLE 5 Aging 16 h 750 C., exhaust gas mixture III Proportion by weight of MnO.sub.2 in the carrier oxide CO T.sub.50 [ C.] C5 10 139 CC3 0 161 C6 10 136 C7 10 142 CC4 0 161 C8 5 132 C9 10 127 CC5 0 165

(54) e) The NO.sub.2/NO.sub.x ratio at the catalyst outlet was also measured with the cores aged for 16 hours at 650 C.

(55) The results are shown in FIGS. 1a and 1b for the catalysts C5 and CC3, FIGS. 2a and 2b for the catalysts C6, C7 and CC4, and FIGS. 3a and 3b for the catalysts C8, C9 and CC5.