Combination of a Zeolite-Based SCR Catalyst with a Manganese-Based SCR Catalyst in the Bypass

Abstract

The invention relates to an exhaust-gas aftertreatment system for selective catalytic reduction with a plurality of SCR catalytic converters, which exhaust-gas aftertreatment system is able to reduce NOx in a large temperature range and can store SOx. The invention further relates to a method for treating an exhaust gas flow, in which method the exhaust-gas aftertreatment system according to the invention is used. The system comprises a high-temperature SCR catalyst for temperature ranges between 250 C. and 750 C. and a low-temperature SCR catalyst arranged downstream thereof for temperature ranges between 60 C. and less than 250 C. There is a reductant supply system directly upstream of the high-temperature SCR catalyst. The high-temperature SCR catalyst is designed to reduce NOx in exhaust gas that has a temperature above a temperature threshold value and to store SOx in the temperature range below the threshold value. The low-temperature SCR catalyst reduces NOx in the temperature range below the threshold value. In each case, the exhaust gas flows through the high-temperature SCR catalyst. An exhaust-gas bypass valve or flow control valve is arranged directly upstream of the low-temperature SCR catalyst. If the temperature of the exhaust gas is greater than or equal to the temperature threshold value, the exhaust gas is completely conducted past the low-temperature SCR catalyst. The high-temperature SCR catalyst advantageously contains a molecular sieve as a catalytically active layer, and the catalytically active layer of the low-temperature SCR catalyst is preferably a manganese-containing mixed oxide.

Claims

1. An exhaust gas aftertreatment system coupled to an internal combustion engine in such a way that it receives the exhaust gas flow, comprising a selective catalytic reduction catalyst for medium to high temperature ranges (HT-SCR), wherein the medium temperature range comprises temperatures of 250 C. to less than 450 C. and the high temperature range comprises temperatures of 450 C. to 750 C., which catalyst is designed both to reduce NOx in an exhaust gas having a temperature above a temperature threshold value, and to store the SOx contained in the exhaust gas across the temperature range of the exhaust gas, which is below a temperature threshold value, a reductant supply system arranged directly upstream of the HT-SCR, a low-temperature SCR (TT-SCR) arranged downstream of the HT-SCR, wherein the low temperature range comprises temperatures of 60 C. to less than 250 C., and wherein the TT-SCR is designed to reduce NOx in an exhaust gas having a temperature below a temperature threshold value, a temperature sensor arranged directly downstream of the HT-SCR and measuring the temperature of the exhaust gas flow exiting such HT-SCR, an exhaust gas bypass and/or flow control valve designed to conduct the exhaust gas flow in its entirety past the TT-SCR if such exhaust gas flow has a temperature greater than or equal to a temperature threshold value, wherein the exhaust gas bypass and/or flow control valve is arranged directly upstream of the TT-SCR.

2. The exhaust gas aftertreatment system according to claim 1, wherein the HT-SCR is present in the form of a catalytically active layer on a carrier substrate, wherein the catalytically active layer is a molecular sieve selected from an aluminosilicate having a SAR of 5-50 and a silicon aluminum phosphate (SAPO) having an (Al+P)/Si value of 4-15 is selected, wherein the molecular sieve contains 1-10% by weight of a transition metal selected from Fe, Cu, and mixtures thereof, calculated as Fe.sub.2O.sub.3 and CuO respectively, based on the total weight of the molecular sieve, and wherein the molecular sieve contains alkali metal and alkaline earth metal cations selected from Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, and mixtures thereof in a total amount of 1% by weight, calculated in the form of the pure metals and based on the total weight of the molecular sieve, and wherein the molecular sieve contains the metals Co, Mn, Cr, Zr and Ni in a total amount of 1% by weight, calculated in the form of the pure metals and based on the total weight of the molecular sieve.

3. The exhaust gas aftertreatment system according to claim 2, wherein the molecular sieve is selected from small-pore zeolites having a maximum pore size of eight tetrahedral atoms and beta zeolite.

4. The exhaust gas aftertreatment system according to claim 2, wherein the molecular sieve is an Fe BEA having a SAR of 10 to 35, an alkali metal content of 0 to 0.7% by weight, calculated as pure metals, and an Fe content of 3 to 9% by weight, calculated as Fe.sub.2O.sub.3, wherein the alkali metal and Fe contents are each based on the total weight of the zeolite.

5. The exhaust gas aftertreatment system according to claim 2, wherein the molecular sieve is a Cu CHA having a SAR of 10 to 35, an alkali metal content of 0 to 0.7% by weight, calculated as pure metals, and a Cu content of 1 to 7% by weight, calculated as CuO, wherein the alkali metal and Cu contents are each based on the total weight of the zeolite.

6. The exhaust gas aftertreatment system according to claim 1, wherein the TT-SCR is a monolithic flow-through substrate with a manganese-containing coating as catalytically active layer.

7. The exhaust gas aftertreatment system according to claim 6, wherein the manganese-containing coating is a manganese-containing mixed oxide selected from mixed oxides of the general formula Mn.sub.aMe.sub.1-aO.sub.b, where Me is one or more elements from the group Fe, Co, Ni, Cu, Zr, Nb, Mo, W, Ag, Sn, Ce, Pr, La, Nd, Ti and Y and where a=0.02-0.98 and b=1.0-2.5, mixed oxides of the general formula Mn.sub.wCe.sub.xMe.sub.1-w-xO.sub.y, where Me is one or more elements from the group Fe, Co, Ni, Cu, Zr, Nb, Mo, W, Ag, Sn, Pr, La, Nd, Ti and Y and where w=0.02-0.98, x=0.02-0.98 and y=1.0-2.5, spinels of the general formula MnMe.sub.2O.sub.4 or MeMn.sub.2O.sub.4, where Me is Fe, Al, Cr, Co, Cu or Ti.

8. The exhaust gas aftertreatment system according to claim 1, and further comprising a second reductant supply system arranged directly upstream of the TT-SCR.

9. The exhaust gas aftertreatment system according to claim 1, wherein the reductant supply system contains a) a reductant source, b) a reductant pump, and c) a reductant dispenser or a reductant injector.

10. The exhaust gas aftertreatment system according to claim 1, wherein an oxidation catalyst is located directly upstream of the reductant supply system located directly upstream of the HT-SCR.

11. The exhaust gas aftertreatment system according to claim 9, wherein a second HT-SCR is located between the HT-SCR and the temperature sensor.

12. The exhaust gas aftertreatment system according to claim 9, wherein a catalytically coated diesel particulate filter (CDPF) is located between the oxidation catalyst and the reductant supply system.

13. The exhaust gas aftertreatment system according to claim 9, wherein one or more HT-SCRs are arranged upstream of the oxidation catalyst and the reductant supply system is located directly upstream of the the HT-SCR that is closest to the internal combustion engine.

14. The exhaust gas aftertreatment system according to claim 1, wherein an ammonia slip catalyst is arranged downstream of the TT-SCR.

15. A method for treating an exhaust gas flow, comprising: providing an exhaust gas aftertreatment system comprising an SCR catalyst for medium to high temperatures (HT-SCR), a low-temperature SCR (TT-SCR) arranged downstream of the SCR for medium to high temperatures, a temperature sensor arranged directly downstream of the HT-SCR and an exhaust gas bypass and/or flow control valve arranged directly upstream of the low-temperature SCR, wherein the SCR catalyst for medium to high temperatures, wherein the medium temperature range comprises temperatures of 250 C. to less than 450 C. and the high temperature range comprising temperatures of 450 C. to 750 C., is designed both a) to reduce NOx in an exhaust gas having a temperature above a temperature threshold value, and b) to store the SOx contained in the exhaust gas across the temperature range of the exhaust gas which is below a temperature threshold value, and the low-temperature SCR is designed to reduce NOx in an exhaust gas having a temperature below a temperature threshold value, wherein the low temperature range comprises temperatures of 60 C. to less than 250 C., and wherein the temperature sensor measures the temperature of the exhaust gas flow exiting the HT-SCR, and wherein the exhaust gas bypass and/or flow control valve is designed to conduct the exhaust gas flow in its entirety past the low-temperature SCR, if such exhaust gas flow has a temperature greater than or equal to a temperature threshold value, storing the SOx contained in the exhaust gas in the HT-SCR, reducing NOx in an exhaust gas flow with the low-temperature SCR catalyst, if a temperature of the exhaust gas flow is within a low temperature range; conducting the exhaust gas stream in its entirety past the low-temperature SCR, if such exhaust gas flow has a temperature greater than or equal to a temperature threshold value, and reducing NOx in an exhaust gas flow with the SCR catalyst for normal to high temperatures, if the temperature of the exhaust gas flow is within a normal to high temperature range.

Description

[0125] FIG. 1a shows the core of the present invention. An HT-SCR catalyst 120 for medium to high temperatures is located downstream of the engine 110. A reductant supply system 160 which comprises a reductant source, a reductant pump, and a reductant dispenser or a reductant injector (not shown), is located directly upstream of such SCR catalyst 120. An exhaust gas temperature sensor 140 is located downstream of the SCR 120. An exhaust gas bypass and/or flow control valve 150, which communicates with the SCR 120 in such a way that it receives exhaust gas, is located downstream of the exhaust gas temperature sensor 140. The exhaust gas bypass and/or flow control valve 150 conducts the exhaust gas flow past the low-temperature SCR 130 via the bypass 180, if the exhaust gas flow has a temperature greater than or equal to a temperature threshold value. However, if the temperature of the exhaust gas flow is below such temperature threshold value, the exhaust gas flow is conducted, completely or partially, through the low-temperature SCR 130, see arrow 170.

[0126] In the embodiment according to FIG. 1b, a further reductant supply system 190 is also located between exhaust gas bypass and/or the flow control valve 150 and the low-temperature SCR 130. In the event that the temperature of the exhaust gas flow is below the temperature threshold value, the exhaust gas flow is conducted through the low-temperature SCR and, immediately before this introduction, the low-temperature SCR is supplied with reductant.

[0127] FIG. 2 shows a preferred embodiment of an exhaust gas purification system comprising the combination according to the invention of an SCR for normal to high temperatures and a low-temperature SCR. This system comprises an oxidation catalyst 215. A reductant supply system 260, which is constructed like the corresponding system 160 in FIG. 1a and FIG. 1b and supplies reductant to the SDPF 225 is located directly downstream of such oxidation catalyst 215. An SCR 220 is located directly downstream of the SDPF 225. An exhaust gas temperature sensor 240 is arranged downstream of the SCR 220. An exhaust gas bypass and/or flow control valve 250, which communicates with the SCR 220 in such a way that it receives exhaust gas, is located downstream of exhaust gas temperature sensor 240. The exhaust gas bypass and/or flow control valve 250 conducts the exhaust gas flow past the low-temperature SCR 230 via the bypass 280, if the exhaust gas flow has a temperature greater than or equal to a temperature threshold value. However, if the temperature of the exhaust gas flow is below such temperature threshold value, the exhaust gas flow is conducted, partially or completely, through the low-temperature SCR 230, see arrow 270. Optionally, a further reductant supply system 290 may also be provided between the exhaust the gas bypass and/or the flow control valve 250 and the low-temperature SCR 230 as described in FIG. 1b. In the event that the temperature of the exhaust gas flow is below the temperature threshold value, the exhaust gas flow is conducted through the low-temperature SCR and, immediately before this introduction, the low-temperature SCR is supplied with reductant.

[0128] FIG. 3a shows another advantageous embodiment of an exhaust gas purification system containing the combination according to the invention of an SCR for normal to high temperatures and a low-temperature SCR. This system comprises an oxidation catalyst 315 and a CDPF 316 located directly downstream thereof. A reductant supply system 360, which is constructed like the corresponding system 160 in FIG. 1a and FIG. 1b and supplies reductant to the SCR 225, is located downstream of the CDPF. An exhaust gas temperature sensor 340 is arranged downstream of the SCR 320. An exhaust gas bypass and/or flow control valve 350, which communicates with the SCR 320 in such a way that it receives exhaust gas, is located downstream of the exhaust gas temperature sensor 340. The exhaust gas bypass and/or flow control valve 350 conducts the exhaust gas flow past the low-temperature SCR 330 via the bypass 380, if the exhaust gas flow has a temperature greater than or equal to a temperature threshold value. However, if the temperature of the exhaust gas flow is below such temperature threshold value, the exhaust gas flow is conducted through the low-temperature SCR 330, see arrow 370. Optionally, a further reductant supply system 390 may also be provided between the exhaust gas bypass and/or the flow control valve 350 and the low-temperature SCR 330 as described in FIG. 1b. In the event that the temperature of the exhaust gas flow is below the temperature threshold value, the exhaust gas flow is conducted through the low-temperature SCR and, immediately before this introduction, the low-temperature SCR is supplied with reductant.

[0129] FIG. 3b shows another advantageous embodiment of the present invention. The system comprises an oxidation catalyst 315, followed by a reductant supply system 360, which is constructed like the corresponding system 160 in FIG. 1a and FIG. 1b and supplies reductant to the SDPF 325. An exhaust gas temperature sensor 340 is arranged downstream of the SDPF 325. An exhaust gas bypass and/or flow control valve 350, which communicates with the SDPF 325 in such a way that it receives exhaust gas, is located downstream of the exhaust gas temperature 340. The exhaust gas bypass and/or flow control valve 350 conducts the exhaust gas flow past the low-temperature SCR 330 via the bypass 380, if the exhaust gas flow has a temperature greater than or equal to a temperature threshold value. However, if the temperature of the exhaust gas flow is below such temperature threshold value, the exhaust gas flow is conducted through the low-temperature SCR 330, see arrow 370. Optionally, a further reductant supply system 390 may also be provided between the exhaust gas bypass and/or the flow control valve 350 and the low-temperature SCR 330 as described in FIG. 1b. In the event that the temperature of the exhaust gas flow is below the temperature threshold value, the exhaust gas flow is conducted through the low-temperature SCR and, immediately before this introduction, the low-temperature SCR is supplied with reductant.

[0130] FIG. 4a relates to a further embodiment based on the system described in FIG. 3a. A reductant supply system 465, which is constructed like the corresponding system 160 in FIG. 1a and FIG. 1b and supplies reductant to the SCR 425, is located upstream of the oxidation catalyst 415 and a CDPF 416 located directly downstream thereof. As described in FIG. 3a, a further reductant supply system 460, which is constructed like the corresponding system 160 in FIG. 1a and FIG. 1b and supplies reductant to the SCR 420, is arranged downstream of the oxidation catalyst 415 and the CDPF 416. An exhaust gas temperature sensor 440 is arranged downstream of the SCR 420. An exhaust gas bypass and/or flow control valve 450, which communicates with the SCR 420 in such a way that it receives exhaust gas, is located downstream of the exhaust gas temperature sensor 440. The exhaust gas bypass and/or flow control valve 450 conducts the exhaust gas flow past the low-temperature SCR 430 via the bypass 480, if the exhaust gas flow has a temperature greater than or equal to a temperature threshold value. However, if the temperature of the exhaust gas flow is below such temperature threshold value, the exhaust gas flow is conducted through the low-temperature SCR 430, see arrow 470. Optionally, a further reductant supply system 490 may also be provided between the exhaust gas bypass and/or the flow control valve 450 and the low-temperature SCR 430 as described in FIG. 1b. In the event that the temperature of the exhaust gas flow is below the temperature threshold value, the exhaust gas flow is conducted through the low-temperature SCR and, immediately before this introduction, the low-temperature SCR is supplied with reductant.

[0131] FIG. 4b relates to a further embodiment based on the system described in FIG. 4a. Here as well, as in FIG. 4a, a reductant supply system 465, which is constructed like the corresponding system 160 in FIG. 1a and FIG. 1b and supplies reductant to the two SCR 425 located one after the other, is located upstream of the oxidation catalyst 415. A reductant supply system 465, which is constructed like the corresponding system 160 in FIG. 1a and FIG. 1b and supplies reductant to the SDPF 420, is downstream of the oxidation catalyst 415. An exhaust gas temperature sensor 440 is arranged downstream of the SDPF 420. An exhaust gas bypass and/or flow control valve 450, which communicates with the SDPF 420 in such a way that it receives exhaust gas, is located downstream of the exhaust gas temperature sensor 440. The exhaust gas bypass and/or flow control valve 450 conducts the exhaust gas flow past the low-temperature SCR 430 via the bypass 480. if the exhaust gas flow has a temperature greater than or equal to a temperature threshold value. However, if the temperature of the exhaust gas flow is below such temperature threshold value, the exhaust gas flow is conducted through the low-temperature SCR 430, see arrow 470. Optionally, a further reductant supply system 390 may also be provided between the exhaust gas bypass and/or the flow control valve 450 and the low-temperature SCR 430 as described in FIG. 1b. In the event that the temperature of the exhaust gas flow is below the temperature threshold value, the exhaust gas flow is conducted through the low-temperature SCR and, immediately before this introduction, the low-temperature SCR is supplied with reductant.

[0132] FIG. 5 schematically shows a further advantageous embodiment of the present invention, which is illustrated by way of example as a supplement to FIG. 1a. An SCR catalyst 520 for normal to high temperatures is located downstream of the engine (not shown) in FIG. 5. A reductant supply system 560, which comprises a reductant source, a reductant pump, and reductant dispenser or a reductant injector (not shown), is located directly upstream of such SCR catalyst 520. An exhaust gas temperature sensor 540 is arranged downstream of the SCR 520. An exhaust gas bypass and/or flow control valve 550, which communicates with the SCR 520 in such a way that it receives exhaust gas, is located downstream of the exhaust gas temperature sensor 540. The exhaust gas bypass and/or flow control valve 550 conducts the exhaust gas flow past the low-temperature SCR 530 via the bypass 580, if the exhaust gas flow has a temperature greater than or equal to a temperature threshold value. However, if the temperature of the exhaust gas flow is below this temperature threshold value, the exhaust gas flow is conducted through the low-temperature SCR 530, see arrow 570. An ASC 525 is located downstream of the low-temperature SCR 520.

[0133] FIG. 6a shows an exhaust gas bypass or flow valve, hereinafter referred to as a bypass valve, which is 100% open. In this case, 100% open means that the exhaust gas paths 1 and 2 are connected so that exhaust gas from the HT-SCR flows into the TT-SCR. The arrow 1 shows the gas discharge from the HT-SCR and the entry into the bypass valve. Arrow 2 shows the discharge of the exhaust gas from the bypass valve toward the TT-SCR. Arrow 3 shows the discharge of the exhaust gas from the bypass valve toward the bypass. In FIG. 6a, the outlet 3 is completely closed.

[0134] The valve position according to FIG. 6a corresponds, as explained above, to a 100% open bypass valve. In this case, the following applies:

T.sub.actualT.sub.min<T.sub.Thd

T.sub.actualR.sub.min<T.sub.Thd

[0135] In this case. [0136] T.sub.actual=actual temperature of the HT-SCR [0137] T.sub.min=minimum operating temperature of the HT-SCR [0138] T.sub.Thd=temperature threshold value

[0139] As long as the actual temperature, i.e., the factual temperature of the HT-SCR, is below the temperature threshold value, the exhaust gas is conducted through the TT-SCR after exiting the HT-SCR, regardless of whether or not the minimum operating temperature of the HT-SCR has already been reached.

[0140] FIG. 6b shows a bypass valve, which is 100% closed. 100% closed is equivalent to 0% open. Here, the exhaust gas paths 1 and 3 are connected so that exhaust gas coming from the HT-SCR flows into the bypass and not through the TT-SCR. In this case, the following applies:

T.sub.actual>T.sub.minT.sub.Thd

[0141] As soon as the temperature of the HT-SCR is greater than its minimum operating temperature and is greater than or equal to the temperature threshold value, the bypass valve is closed. After exiting the HT-SCR, the exhaust gas flow is then conducted past the TT-SCR.

[0142] If a flow valve or a combination of exhaust gas bypass and flow valve is exclusively used, conditions between 0% and 100% opening of the flow valve can be described by the condition

T.sub.actual>T.sub.min<T.sub.Thd

[0143] In this condition, the actual temperature of the HT-SCR is greater than its minimum operating temperature but less than the temperature threshold value. In this case, a proportionality factor which indicates the degree of opening of the flow valve can be determined from (T.sub.ThdT.sub.actual). In this case, the following boundary condition applies:

[0144] If

T.sub.actualT.sub.min and T.sub.ThdT.sub.actual0,

the bypass valve is 0% open, which is equivalent to 100% closed.

[0145] FIG. 7 shows the nitrogen oxide conversion values U.sub.Nox [%] of three HT-SCR catalysts in the temperature range between 200 and 550 C. HT-SCR1 is a vanadium-containing SCR, HT-SCR2 is an iron-containing SCR and HT-SCR3 is a copper-containing SCR. The experimental conditions for the measurement of the nitrogen oxide conversion values are given in Exemplary Embodiment 4.

[0146] FIG. 8 shows the SO.sub.2 curve after flowing through the DPF for three stationary sulfurization experiments on an engine test bench for a Cu zeolite HT-SCR. Such sulfurization experiments are described in Exemplary Embodiment 5. In this case, the SCR inlet temperature and space velocity in the SCR were varied for the three experiments.

[0147] FIG. 9 shows the SO.sub.2 curve after flowing through the Cu zeolite HT-SCR for three stationary sulfurization experiments on an engine test bench. Such sulfurization experiments are described in Exemplary Embodiment 5. In this case, the SCR inlet temperature and space velocity in the SCR were varied for the three experiments. Together with FIG. 8. This shows the ability of the Cu zeolite to store SO.sub.x at different temperatures and space velocities.

[0148] At temperatures below the HT-SCR minimum temperature and thus also below the threshold value (EOP_01), no SO.sub.2 breakthrough can be observed for the test duration, which means good protection for the TT-SCR.

[0149] By increasing the temperature and/or the space velocity, the SO.sub.x trap efficiency decreases somewhat. However, since in this case the NO.sub.x conversion can be 100% (see FIGS. 7 and 10), the TT-SCR can already be switched into the bypass in these cases.

[0150] FIG. 10 shows the NO.sub.x conversion of the Cu zeolite for the three sulfurization experiments. As can also be derived from FIG. 7, the HT-SCR shows no full conversion at 190 C. since such temperature is below its minimum temperature. Nevertheless, the conversion of 80% is maintained for a long time despite sulfur exposure. It can also be derived from FIG. 7 that at the beginning of the sulfurization, 100% NO.sub.x conversion arises at EOP_02 and EOP_03.

[0151] FIG. 11 shows the sulfur breakdown curve from dynamic engine test bench experiments for a V HT-SCR and a Cu HT-SCR. The V HT-SCR shows hardly any sulfur storage functionality for the test time. However, the Cu HT-SCR exhibits the property as sulfur trap even under dynamic conditions.

[0152] FIG. 12 shows the NO.sub.x conversion curves from the dynamic engine test bench tests for a V HT-SCR and a Cu HT-SCR. Both systems show that they still retain their HT-SCR function even with sulfur exposure.

EMBODIMENTS

Embodiment 1: HT-SCR1=V SCR

[0153] a) A commercially available titanium dioxide in anatase form doped with 5% by weight silica was dispersed in water, and vanadium dioxide (VO.sub.2) and tungsten trioxide (WO.sub.3) were subsequently added to such an amount that a catalyst of the composition 88.10% by weight TiO.sub.2, 4.60% by weight SiO.sub.2, 3.00% by weight V.sub.2O.sub.5, 4.30% by weight WO.sub.3 results. The mixture was stirred thoroughly and finally milled in a commercially available agitator bead mill. [0154] b) The dispersion obtained according to a) was coated onto a commercially available ceramic flow-through substrate with a volume of 0.5 l and a cell number of 62 cells per square centimeter at a wall thickness of 0.17 mm over its entire length with a washcoat loading of 160 g/l. Subsequently, drying took place at 90 C., and calcination took place at 600 C. for 2 hours. The catalyst obtained in this way is referred to below as HT-SCR1.

Embodiment 2: HT-SCR2=Fe SCR

[0155] a) A commercially available BEA-type zeolite with a SAR of 25 is mixed in water with a quantity of Fe(NO.sub.3).sub.3 corresponding to an iron content of 4.5% by weight (based on the iron-containing zeolite and calculated as Fe.sub.2O.sub.3) and stirred overnight. [0156] b) The dispersion obtained according to a) was coated onto a commercially available ceramic flow-through substrate with a volume of 0.5 l and a cell number of 62 cells per square centimeter at a wall thickness of 0.17 mm over its entire length with a washcoat loading of 220 g/l. The catalyst obtained (hereinafter referred to as HT-SCR2) is dried at 90 C., then calcined step-by-step in air at 350 C. and at 550 C.

Embodiment 3: HT-SCR3=Cu SCR

[0157] a) A commercially available CHA-type zeolite with a SAR of 30 is mixed in water with a quantity of CuSO.sub.4 corresponding to a copper content of 3.7% by weight (based on the copper-containing zeolite and calculated as CuO) and stirred overnight. [0158] b) The dispersion obtained according to a) was coated onto a commercially available ceramic flow-through substrate with a volume of 0.5 l and a cell number of 62 cells per square centimeter at a wall thickness of 0.17 mm over its entire length with a washcoat loading of 220 g/l. The catalyst obtained (hereinafter referred to as HT-SCR3) is dried at 90 C., then calcined step-by-step in air at 350 C. and at 550 C.

Embodiment 4: Determination of DeNOx Activity:

[0159] b) The DeNOx activity of the catalysts HT-SCR1 to HT-SCR3 was tested in a laboratory model gas system under the conditions given in the table below.

TABLE-US-00001 Gas/parameter Concentration/conditions NH.sub.3 1100 ppm NO 1000 ppm H.sub.2O 5% O.sub.2 10% N2 Remainder Temperature Cooling step-by-step 550 to 200 C. Space velocity 60.000 h.sup.1

[0160] During the measurement, the nitrogen oxide concentrations of the model gas were detected after flowing through the HT-SCR catalyst by means of FTIR (Fourier transform infrared spectrometry). The nitrogen oxide conversion, based on the ratio of NH.sub.3 to NO, over the catalyst for each temperature measuring point was calculated as follows from the known metered nitrogen oxide contents, which were verified during conditioning at the beginning of the respective test run with a pre-catalyst exhaust gas analysis, and the measured post-catalyst nitrogen oxide contents.

[00001]$U_{N.Math.O_x}\left[\%\right]=\left(1-\frac{c_{\mathrm{Output}}\left({\mathrm{NO}}_x\right)}{c_{\mathrm{Input}}\left({\mathrm{NO}}_x\right)}\right)1.Math.0.Math.0$

where

[0161] U.sub.NOx nitrogen oxide conversion

[0162] C.sub.Output concentration of the nitrogen oxides after flowing through the HT-SCR catalyst

[0163] C.sub.Input concentration of the nitrogen oxides before flowing through the HT-SCR catalyst

C.sub.Input/Output(NO.sub.x)=C.sub.Input/Output(NO)+C.sub.Input/Output(NO.sub.2)+C.sub.Input/Output(N.sub.2O)

[0164] The nitrogen oxide conversion values U.sub.NOx [%] obtained were applied as a function of the pre-catalyst temperature measured to evaluate the SCR activity of the materials investigated. This is shown in FIG. 7.

TABLE-US-00002 TABLE 1 Nitrogen oxide conversion values of the three HT-SCR catalysts according to Exemplary Embodiments 1 to 3 U.sub.NOx [%] T [ C.] HT-SCR1 HT-SCR2 HT-SCR3 200 26.13 28.36 85.71 250 71.79 62.29 99.41 300 95.17 85.48 100.07 350 98.58 94.55 100.07 400 98.87 97.98 99.76 450 97.76 99.29 96.79 500 92.03 99.44 90.65 550 69.13 96.20 83.03

Embodiment 5: Analysis of Cu SCR: SO.SUB.x .Trap Function and HT-SCR:

[0165] The investigations of the HT-SCR3 with regard to its suitability as SCR catalyst for the medium to high temperature range and at the same time its suitability as SO.sub.x trap in the working range of the TT-SCR were carried out on the engine test bench. The catalyst volume used corresponded to the factor 2.26 of the engine cubic capacity or displacement. Customary analysis was used as analysis. For the NO.sub.x conversion determination, the pre-SCR and post-SCR NO.sub.x concentrations were measured by means of CLDs (chemiluminescence detectors). The conversion was calculated analogously to Example 4.

[00002]$U_{N.Math.O_x}\left[\%\right]=\left(1-\frac{c_{\mathrm{Output}}\left({\mathrm{NO}}_x\right)}{c_{\mathrm{Input}}\left({\mathrm{NO}}_x\right)}\right)1.Math.0.Math.0$

where

[0166] U.sub.NOx nitrogen oxide conversion

[0167] C.sub.Output concentration of the nitrogen oxides after flowing through the HT-SCR catalyst

[0168] C.sub.Input concentration of the nitrogen oxides before flowing through the HT-SCR catalyst

[0169] The SO.sub.x input and output concentrations were measured as SO.sub.2 by a mass spectrometer each at the DPF output and SCR output. The experiments were carried out in stationary operating mode. For this purpose, three different operating points were selected which differ with regard to their SCR inlet temperature and the exhaust gas mass flow or the SCR space velocity (GHSV or SV).

[0170] GHS stands for gas hourly space velocity and SV stands for space velocity.

[0171] Commercially available urea solution was used as reductant. An amount corresponding to an ammonia/NOX ratio of 1.2 was metered.

[0172] Table 2 compiles the points. Here, EOP stands for engine operating point.

TABLE-US-00003 TABLE 2 SCR inlet temperature and SCR space velocity for three EOPs examined T SCR in [ C.] SV [h.sup.1] EOP_01 190 7700 EOP_02 260 23100 EOP_03 260 34000

[0173] EOP_01 represents an operating point at which the exhaust gas temperature is below the threshold value and at the same time below the minimum temperature of the HT-SCR.

[0174] Wth regard to their temperature, EOP_02 and EOP_03 are above the minimum temperature.

[0175] For the sulfurization, B10 diesel fuel was used, which was additionally mixed with sulfur. Fuels of this type are commercially available. For all three operating points, the experiment was carried out until 2 g of sulfur (not SOx but S) per liter of SCR volume was emitted.

[0176] The SO2 curve after passage through the DPF is shown in FIG. 8 and the SO2 curve after passage through the SCR is shown in FIG. 9.

Embodiment 6: NOx Conversion and SO.SUB.2 .Trap Function of Cu HT-SCR and V HT-SCR

[0177] The comparison of a V SCR with a Cu SCR with regard to its suitability as a combined HT-SCR for the medium to high temperature range and as SO.sub.x trap in the working range of the TT-SCR was carried out on the engine test bench. The vanadium-containing V SCR (HT-SCR1) and the copper-containing Cu SCR (HT-SCR3) according to Exemplary Embodiments 1 and 3 were tested. The catalyst volume used corresponded to the factor 1.1 of the engine cubic capacity or displacement. For the NO.sub.x conversion determination, the pre-SCR and post-SCR NO.sub.x concentrations were measured by means of CLDs (chemiluminescence detectors). The conversion was calculated as in Example 5.

[0178] The SO.sub.x input and output concentrations were measured as SO.sub.2 by a mass spectrometer each at the DPF output and SCR output. The experiments were carried out in dynamic operating mode. To this end, a sequence of WHTC cycles (world harmonized transient cycles) was performed. WHTCs are legally predefined test cycles used for testing, qualifying and releasing heavy-duty/payload engines. The performance and design of a WHTC and the implementation of the test procedure are known to the person skilled in the art.

[0179] Commercially available urea solution was used as reductant. An amount corresponding to an ammonia/NO.sub.x ratio of 0.8 was metered. This is substoichiometric and the HT-SCR therefore cannot achieve 100% conversion. The theoretical maximum conversion would accordingly correspond to 80%.

[0180] For the sulfurization, B10 diesel fuel was used, which was additionally mixed with sulfur. Fuels of this type are commercially available. The sulfur emission per WHTC was 1375 mg.

[0181] The NO.sub.x conversion of the Cu HT-SCR is shown in FIG. 10.

[0182] The sulfur breakdown curve from the dynamic engine test bench experiments for a V HT-SCR and the Cu HT-SCR is shown in FIG. 11.

[0183] FIG. 12 shows the NO.sub.x conversion curves from the dynamic engine test bench tests for a V HT-SCR and a Cu HT-SCR. In this case, the cumulative mass of SO.sub.2 per cycle, measured at the output of the SCR, is plotted against the number of sulfation cycles.