THERMALLY STABLE NH3-SCR CATALYST COMPOSITIONS

Abstract

A catalyst composition comprising a mixture of (a) a zeolite compound in an amount of from 10% to 60% by weight, wherein the zeolite compound comprises cations selected from Fe.sup.2+, Fe.sup.3+, Cu.sup.+, Cu.sup.2+ or mixtures thereof, and (b) a ceria/zirconia/alumina composite oxide, wherein the alumina content in said composite oxide is in the range of 20 to 80% by weight, in particular of 40 to 60% by weight,
a catalyst comprising such catalyst composition and its use for exhaust gas after-treatment of diesel and lean burn engines.

Claims

1. A catalyst composition comprising a mixture of (a) a zeolite compound in an amount of 10% to 60% by weight, wherein the zeolite compound comprises cations selected from Fe.sup.2+, Fe.sup.3+, Cu.sup.+, Cu.sup.2+ or mixtures thereof, (b) a ceria/zirconia/alumina composite oxide, wherein the alumina content in said composite oxide is in the range of 20 to 80% by weight.

2. A catalyst composition according to claim 1, consisting of (a) and (b).

3. A catalyst composition according to claim 1, wherein the amount of the zeolite compound in said composition is in the range from 25 to 55% by weight.

4. A catalyst composition according to claim 3, wherein the amount of the zeolite compound in said composition is in the range from 30 to 50% by weight.

5. A catalyst composition according to claim 1, wherein the ceria/zirconia/alumina composite oxide is of formula
(Al.sub.2O.sub.3).sub.x(CeO.sub.2).sub.y(ZrO.sub.2).sub.z(M-oxide).sub.a wherein, x denotes a number from 20% to 80% by weight; y denotes a number from 5% to 40% by weight, z denotes a number from 5% to 40% by weight, and a denotes a number from 0% to 15% by weight, with the proviso that x+y+z+a=100% by weight, and M denotes a rare earth metal cation other than a Ce cation, an earth alkali metal cation, or a cation selected from a Mn, Fe, Ti, Sb or Bi cation, or M denotes individual mixtures of such cations.

6. A catalyst composition according to claim 1, wherein the amount of the cations selected from Fe.sup.2+, Fe.sup.3+, Cu.sup.+, Cu.sup.2+ or mixtures thereof in the zeolite is from 0.05-15 weight % of the metal, based on the weight of the zeolite including the cations.

7. A catalyst comprising a substrate coated with a catalyst composition according to claim 1.

8. A catalyst according to claim 7, wherein the substrate is selected from the group consisting of cordierite, mullite, Al-Titanate, and SiC.

9. A method of using a catalyst according to claim 7, comprising contacting and after treating exhaust gas of a diesel or a lean burn engine by the catalyst.

10. The method according to claim 9, wherein after treating exhaust gas comprises Selective Catalytic Reduction (SCR) of NO.sub.x in the exhaust gases.

11. A catalyst composition according to claim 1, wherein the alumina content in said composite oxide is in the range of 40 to 60% by weight.

12. A catalyst composition according to claim 5, wherein M comprises an earth alkali metal cation selected from a Mg, Ca, Sr or Ba cation.

13. A catalyst composition according to claim 6, wherein the amount of the cations selected from Fe.sup.2+, Fe.sup.3+, Cu.sup.+, Cu.sup.2+ or mixtures thereof in the zeolite is from 0.1-10 weight % of the metal, based on the weight of the zeolite including the cations.

14. A catalyst composition according to claim 6, wherein the amount of the cations selected from Fe.sup.2+, Fe.sup.3+, Cu.sup.+, Cu.sup.2+ or mixtures thereof in the zeolite is from 1-6 weight % of the metal, based on the weight of the zeolite including the cations.

15. The method according to claim 9, wherein the exhaust gas is from diesel and lean burn engines of automotives or for non-road applications.

Description

EXAMPLE 1

SCR Catalyst Containing 50 wt % of Composite Oxide Obtained According to A) and 50 wt % of Cu-Zeolite (Type BEA)

[0074] In order to prepare 20 g of SCR catalyst powder, 10 g of freshly prepared ceria/zirconia/alumina composite oxide prepared according to example A) were physically mixed with 10 g of Cu-zeolite ex Clariant (Type BEA; LOI 3.5%; BET 560 m.sup.2/g; d50 as 2.47 μm) in an agate mortar and considered as fresh catalyst powder for measurement of NO.sub.x conversion. 10 g of the SCR catalyst powder thus obtained were aged by calcining at 700° C./10 hours and referred to as aged catalyst. NO.sub.x conversion was also measured after ageing.

EXAMPLE 2

SCR Catalyst Containing 75 wt % of Composite Oxide Obtained According to A) and 25 wt % of Cu-Zeolite (Type BEA)

[0075] In order to prepare 20 g of SCR catalyst powder, 15 g of freshly prepared ceria/zirconia/alumina composite oxide prepared according to example A) were physically mixed with 5 g of Cu-zeolite ex Clariant (Type BEA; LOI 3.5%; BET 560 m.sup.2/g; d50 as 2.47 μm) in an agate mortar and considered as fresh catalyst powder for measurement of NO.sub.x conversion. 10 g of the SCR catalyst powder thus obtained were aged by calcining at 700° C./10 hours and referred to as aged catalyst for measurement of NO.sub.x.

EXAMPLE 3

SCR Catalyst Containing 80 wt % of Composite Oxide Obtained According to A) and 20 wt % of Cu-Zeolite (Type BEA)

[0076] In order to prepare 20 g of SCR catalyst powder, 16 g of freshly prepared ceria/zirconia/alumina composite oxide prepared according to example A) were physically mixed with 4 g of Cu-zeolite ex Clariant (Type BEA; LOI 3.5%; BET 560 m.sup.2/g; d50 as 2.47 μm) in an agate mortar and considered as fresh catalyst powder. 10 g of the SCR catalyst powder obtained were aged by calcining at 700° C./10 hours and referred to as aged catalyst. NO.sub.x conversion was measured in both fresh and aged catalysts.

EXAMPLE 4

SCR Catalyst Containing 85 wt % of Composite Oxide Obtained According to A) and 15 wt % of Cu-Zeolite (Type BEA)

[0077] In order to prepare 20 g of SCR catalyst powder, 17 g of freshly prepared ceria/zirconia/alumina composite oxide as prepared according to example A) were physically mixed with 3 g of Cu-zeolite ex Clariant (Type BEA; LOI 3.5%; BET 560 m.sup.2/g; d50 as 2.47 μm) in an agate mortar and considered as fresh catalyst powder. 10 g of the SCR catalyst powder obtained were aged by calcining at 700° C./10 hours and referred to as aged catalyst. NO.sub.x conversion was measured in both fresh as well as aged catalyst.

EXAMPLE 5

SCR Catalyst Containing 90 wt % of Composite Oxide Obtained According to A) and 10 wt % of Cu-Zeolite (Type BEA)

[0078] In order to prepare 20 g of SCR catalyst powder, 18 g of freshly prepared ceria/zirconia/alumina composite oxide as prepared according to example A) were physically mixed with 2 g of Cu-zeolite ex Clariant (Type BEA; LOI 3.5%; BET 560 m.sup.2/g; d50 as 2.47 μm) in an agate mortar and considered as fresh catalyst powder.

[0079] 10 g of the SCR catalyst powder as obtained were aged by calcining at 700° C./10 hours and referred to as aged catalyst. NO.sub.x conversion was measured in both fresh as well as aged catalyst.

EXAMPLE 6

SCR Catalyst Containing 50 wt % of Composite Oxide Obtained According to B) and 50 wt % of Cu-Zeolite (Type BEA)

[0080] In order to prepare 20 g of SCR catalyst powder, 10 g of freshly prepared ceria/zirconia/alumina composite oxide prepared according to example B) were physically mixed with 10 g of Cu-zeolite ex Clariant (Type BEA; LOI 3.5%; BET 560 m.sup.2/g; d50 as 2.47 μm) in an agate mortar and considered as fresh catalyst powder for measurement of NO.sub.x activity. 10 g of the SCR catalyst powder as obtained were aged by calcining at 700° C./10 hours and referred to as aged catalyst. Aged catalyst was also tested for NO.sub.x conversion activity.

EXAMPLE 7

SCR Catalyst Containing 50 wt % of Composite Oxide Obtained According to C) and 50 wt % of Cu-Zeolite (Type BEA)

[0081] In order to prepare 20 g of SCR catalyst powder, 10 g of freshly prepared ceria/zirconia/alumina composite oxide obtained according to example C) were physically mixed with 10 g of Cu-zeolite ex Clariant (Type BEA; LOI 3.5%; BET 560 m.sup.2/g; d50 as 2.47 μm) in an agate mortar and considered as fresh catalyst powder for measurement of NO.sub.x conversion. 10 g of the SCR catalyst powder obtained were aged by calcining at 700° C./10 hours and referred to as aged catalyst for NO.sub.x conversion measurement.

EXAMPLE 8

SCR Catalyst Containing 50 wt % of Composite Oxide Obtained According to A) and 50 wt % of Fe-Zeolite (Type BEA)

[0082] In order to prepare 20 g of SCR catalyst powder, 10 g of freshly ceria/zirconia/alumina composite oxide prepared according to example A) were physically mixed with 10 g of Fe-zeolite ex Clariant (Type BEA; LOI 7.0%; BET 579 m.sup.2/g; d50 as 5.8 μm) in an agate mortar and considered as fresh catalyst powder. 10 g of the SCR catalyst powder as obtained were aged by calcining at 700° C./10 hours and referred to as aged catalyst. NO.sub.x conversion was measured for both fresh as well as aged catalyst.

EXAMPLE 9

SCR Catalyst Containing 50 wt % of Composite Oxide Obtained According to B) and 50 wt % of Fe-Zeolite (Type MFI)

[0083] In order to prepare 20 g of SCR catalyst powder, 10 g of freshly prepared ceria/zirconia/alumina composite oxide prepared according to example B) were physically mixed with 10 g of Fe-zeolite ex Clariant (Type MFI; LOI 7.5%; BET 373 m.sup.2/g; d50 as 5.8 μm) in an agate mortar and considered as fresh catalyst powder. 10 g of the SCR catalyst powder obtained were aged by calcining at 700° C./10 hours and referred to as aged catalyst. NO.sub.x conversion was measured for both fresh as well as aged catalyst.

EXAMPLE 10

SCR Catalyst Containing 50 wt % of Composite Oxide Prepared According to C) and 50 wt % of Fe-Zeolite (Type MFI)

[0084] In order to prepare 20 g of SCR catalyst powder, 10 g of freshly prepared ceria/zirconia/alumina composite oxide prepared according to example C) were physically mixed with 10 g of Fe-zeolite ex Clariant (Type MFI; LOI 7.5%; BET 373 m.sup.2/g; d50 as 5.8 μm) in an agate mortar and considered as fresh catalyst powder. 10 g of the SCR catalyst powder as obtained were aged by calcining at 700° C./10 hours and referred to as aged catalyst. NO.sub.x conversion was measured for both fresh as well as aged catalyst.

EXAMPLE 11

[0085] SCR Catalyst Containing 50 wt % of Composite Oxide Al.sub.2O.sub.3 (52.9%) ZrO.sub.2 (30.4%) CeO.sub.2 (14.5%) Nd.sub.2O.sub.3 (2.2%)—“Enhanced Material”—and 50 wt % of Cu-Zeolite (Type BEA)
a) Preparation of Ce/Zr/Rare Earth—Hydroxide (Wet Cake) CeO.sub.2(30%) ZrO.sub.2(65%) Nd.sub.2O.sub.3(5%)/Total Oxide

[0086] 1,541 kg of Cerium Nitrate solution (CeO.sub.2 content=29.2%), 4,557 kg of Zirconyl nitrate solution (ZrO.sub.2 content=21.4%) and 0.196 kg of neodymium nitrate as crystals (Nd.sub.2O.sub.3 content=38.3%) are mixed resp. dissolved in 20 kg of deionised water. The mixture was stirred for 10 minutes to get a clear solution. 0.762 kg of H.sub.2O.sub.2 was added to mixed metal nitrate solution and mixture was stirred for 45 minutes. Co-precipitation was done by addition of 18% ammonium hydroxide under vigorous stirring till pH of 8.5 was obtained. The precipitate was stirred for another half an hour and was filtered via a filter press and washed with deionised water.

[0087] ROI (Residue on Ignition at 1000° C./2 hrs)=19.5%

[0088] Yield=approx. 7.69 kg of wet cake corresponding to 1.5 kg of Total Oxide

b) Preparation of Composite Oxide Al.sub.2O.sub.3 (52.9%) ZrO.sub.2 (30.4%) CeO.sub.2 (14.5%) Nd.sub.2O.sub.3 (2.2%)

[0089] 228.4 g of the wet cake (corresponding to 45 g of oxide) prepared under a) was suspended in 670 ml of deionized water and the mixture was stirred using an external stirrer for 15 minutes. The suspension was added to 937.5 g of an aqueous Boehmite Suspension of commercially available Disperal HP14* with an Al.sub.2O.sub.3 content of 4.8 wt. %. The aqueous suspension obtained was stirred vigorously using an external stirrer for 30 minutes, spray dried and calcined at 850° C. for 4 hours (=fresh material). BET was measured of fresh material and material calcined 1100° C./4 hours (aged material).

[0090] BET (fresh material): 102 m.sup.2/g

[0091] BET (after ageing) at 1100° C./4 hours: 47 m.sup.2/g

[0092] *The manufacture of (commercially available) Boehmite Disperal HP14 is disclosed in WO 2013/007809.

c) SCR Catalyst Containing 50 wt % of Composite Oxide Al.sub.2O.sub.3 (52.9%) ZrO.sub.2 (30.4%) CeO.sub.2 (14.5%) Nd.sub.2O.sub.3 (2.2%) and 50 wt % of Cu-Zeolite (Type BEA)

[0093] In order to prepare 20 g of SCR catalyst powder, 10 g of freshly prepared alumina/ceria/zirconia composite oxide prepared according to b) were physically mixed with 10 g of Cu-zeolite ex Clariant (Type BEA; LOI 3.5%; BET 560 m.sup.2/g; d50 as 2.47 μm) in an agate mortar and considered as fresh catalyst powder for measurement of NO.sub.x conversion. 10 g of the SCR catalyst powder thus obtained were aged by calcining at 700° C./10 hours and referred to as aged catalyst. NO.sub.x conversion was also measured after ageing.

COMPARATIVE EXAMPLE 1

NO.SUB.x .Conversion of Ceria/Zirconia/Alumina Composite Oxide

[0094] NO.sub.x conversion was measured using freshly prepared ceria/zirconia/alumina composite oxide as prepared according to example A) (referred to as fresh catalyst).

[0095] The composite oxide was aged at 700° C./10 hours and NO.sub.x conversion was measured again (referred to as aged catalyst).

COMPARATIVE EXAMPLE 2

[0096] NO.sub.x conversion of Cu-zeolite (type BEA; LOI 3.5%; ex Clariant

[0097] In comparative example 2 NO.sub.x conversion was measured using Cu-zeolite (type BEA; LOI 3.5%; ex Clariant) as it is (referred to as fresh catalyst).

[0098] Cu-zeolite was aged at 700° C./10 hours and NO.sub.x conversion was measured again (referred to as aged catalyst).

COMPARATIVE EXAMPLE 3

[0099] SCR catalyst containing 75 wt % of γ-Alumina (PURALOX, SASOL) and 25 wt % of Cu-zeolite (type BEA; LOI 3.5%; ex Clariant).

[0100] 20 g of SCR catalyst powder were prepared by physically mixing 15 g of γ-Alumina (PURALOX, BET 80-160 m.sup.2/g ex SASOL) and 5 g of Cu-zeolite (type BEA; LOI 3.5%; ex Clariant) in an agate mortar considered as fresh catalyst and tested for NO.sub.x conversion activity. 10 g of the SCR catalyst powder obtained were aged at 700° C./10 hours and NO.sub.x conversion was measured again (referred to as aged catalyst).

COMPARATIVE EXAMPLE 4

[0101] SCR Catalyst Containing 75 wt % of [50% Al.sub.2O.sub.3-15% CeO.sub.2-32.5% ZrO.sub.2-2.5% Nd.sub.2O.sub.3-Oxide Mixture [Prepared by Physically Mixing the Individual Oxides] and 25 wt % of Cu-Zeolite (Type BEA; LOI 3.5%; Ex Clariant).
a) Synthesis of the Oxide Mixture [50% Al.sub.2O.sub.3-15% CeO.sub.2-32.5% ZrO.sub.2-2.5% Nd.sub.2O.sub.3]

[0102] All oxides used as a starting material were passed through a 100Ξ sieve before mixing. In order to make 25 g of oxide mixture, 12.5 g Al.sub.2O.sub.3 (99.99%), 3.75 g CeO.sub.2 (99.99%), 8.13 g of ZrO.sub.2 (99.99%) and 0.63 g Nd.sub.2O.sub.3(99.99%) were physically mixed in an agate mortar and then heat treated at 850° C./4 h.

b) SCR catalyst containing 75 wt % of [50% Al.sub.2O.sub.3-15% CeO.sub.2-32.5% ZrO.sub.2-2.5% Nd.sub.2O.sub.3]—Oxide Mixture and 25 wt % of Cu-Zeolite (type BEA; LOI 3.5%; ex Clariant).

[0103] 20 g of SCR catalyst powder were prepared by physically mixing 15 g of oxide mixture [50% Al.sub.2O.sub.3-15% CeO.sub.2-32.5% ZrO.sub.2-2.5% Nd.sub.2O.sub.3—prepared as described under a) and 5 g of Cu-Zeolite (type BEA; LOI 3.5%; ex Clariant) in an agate mortar.

[0104] The SCR catalyst mixture was tested for NO.sub.x conversion activity.

Results of Catalytic Testing of SCR Catalysts Powders:

[0105] Testing was performed according to the parameters as disclosed in Table 1 above.

[0106] In Table 2 below the NO.sub.x conversion in % at temperatures from 200 to 500° C. with a catalyst prepared according to examples 1 to 10 and comparative examples 1 to 3 under fresh and aged conditions is indicated. As a feed gas there was applied practically NO only (feedgas >90% NO).

TABLE-US-00002 TABLE 2 Temp. ° C. 200 230 250 270 300 320 350 380 420 450 480 500 Example 1 50% [50% Al.sub.2O.sub.3 − 15% CeO.sub.2 − 32.5% ZrO.sub.2 − 2.5% Nd.sub.2O.sub.3] + 50% Cu-zeolite Fresh 96 100 100 100 100 100 100 92 88 83 76 73 Aged 91 98 99 99 99 99 99 94 91 88 85 81 Example 2 75% [50% Al.sub.2O.sub.3 − 15% CeO.sub.2 − 32.5% ZrO.sub.2 − 2.5% Nd.sub.2O.sub.3] + 25% Cu-zeolite Fresh 80 95 97 98 99 99 99 94 90 87 82 78 Aged 64 88 92 94 96 99 97 96 93 91 89 86 Example 3 80% [50% Al.sub.2O.sub.3 − 15% CeO.sub.2 − 32.5% ZrO.sub.2 − 2.5% Nd.sub.2O.sub.3] + 20% Cu-zeolite Fresh 73 93 96 97 98 99 92 88 86 81 75 72 Aged 54 76 82 85 88 89 90 90 89 89 87 84 Example 4 85% [50%Al.sub.2O.sub.3 − 15% CeO.sub.2 − 32.5% ZrO.sub.2 − 2.5% Nd.sub.2O.sub.3] + 15% Cu-zeolite Fresh 69 88 92 95 96 97 92 89 85 81 75 71 Aged 46 68 76 80 85 87 90 90 89 88 86 83 Example 5 90% [50% Al.sub.2O.sub.3 − 15% CeO.sub.2 − 32.5% ZrO.sub.2 − 2.5% Nd.sub.2O.sub.3] + 10% Cu-zeolite Fresh 42 71 80 85 89 92 91 88 85 81 75 71 Aged 26 46 55 61 68 73 81 87 88 89 87 85 Example 6 50% [Al.sub.2O.sub.3(50%) − ZrO.sub.2(20%) − CeO.sub.2(20%) − Bi.sub.2O.sub.3(10%)] + 50% Cu-zeolite Fresh 97 100 100 100 100 100 100 93 88 83 77 72 Aged 94 99 100 100 100 100 100 94 90 87 83 80 Example 7 50% [Al.sub.2O.sub.3(30%) − ZrO.sub.2(40%) − CeO.sub.2(30%)] + 50% Cu-zeolite Fresh 90 99 100 100 100 100 100 92 88 84 77 73 Aged 83 97 99 99 99 99 99 96 92 89 85 81 Example 8 50% [50% Al.sub.2O.sub.3 − 15% CeO.sub.2 − 32.5% ZrO.sub.2 − 2.5% Nd.sub.2O.sub.3] + 50% Fe-zeolite (BEA) Fresh 6 25 43 63 87 95 98 97 95 95 95 93 Aged 6 21 35 53 79 88 93 94 95 95 95 93 Example 9 50% [Al.sub.2O.sub.3(50%) − ZrO.sub.2(20%) − CeO.sub.2(20%) − Bi.sub.2O.sub.3(10%)] 50% Fe-zeolite (MFI) Fresh 19 63 85 95 99 99 99 85 85 85 85 85 Aged 34 63 82 93 98 99 98 93 93 93 93 93 Example 10 50% [Al.sub.2O.sub.3(30%) − ZrO.sub.2(40%) − CeO.sub.2(30%)] + 50% Fe-zeolite (MFI) Fresh 16 55 82 96 100 100 100 90 90 90 92 92 Aged 22 53 73 89 98 99 99 93 93 93 93 93 Example 11 50% [Al.sub.2O.sub.3(52.9%) − ZrO.sub.2(30.4%) − CeO.sub.2(14.5%) − Nd.sub.2O.sub.3(2.2%)] + 50% Cu-Zeolite Fresh 97 99 99 99 99 99 99 94 91 87 82 79 Aged 86 95 97 98 98 98 98 98 95 93 91 88 Comp. Ex. 1 100% Composite Oxide (50% Al.sub.2O.sub.3 − 15% CeO.sub.2 − 32.5% ZrO.sub.2 − 2.5% Nd.sub.2O.sub.3) Fresh 0 0 0 2 6 11 20 32 46 52 49 43 Aged 0 0 1 2 7 11 21 32 43 47 44 38 Comp. Ex. 2 100% Cu-zeolite Fresh 94 100 100 100 100 100 100 92 88 83 77 71 Aged 93 99 99 99 99 99 99 95 90 86 81 77 Comp. Ex. 3 75% γ-Al.sub.2O.sub.3 + 25% Cu-zeolite Fresh 74 90 94 95 97 97 93 88 86 83 78 76 Aged 29 47 55 63 74 81 88 90 87 84 77 70 Comp. 75% [50% Al.sub.2O.sub.3 − 15% CeO.sub.2 − 32.5% ZrO.sub.2 − 2.5% Nd.sub.2O.sub.3 out of individual Oxides] + Example 4 25% Cu-Zeolite Fresh 78 92 95 96 98 98 90 89 85 80 75 70