CATALYST FOR ENHANCED HIGH TEMPERATURE CONVERSION AND REDUCED N2O MAKE

Abstract

The present invention relates to a catalyst for the treatment of an exhaust gas of a diesel combustion engine, said catalyst particularly comprising a specific substrate and a coating disposed on the surface of the internal walls of said substrate, the coating particularly comprising a specific first non-zeolitic oxidic material, and a specific zeolitic material comprising Fe and Cu, wherein the catalyst exhibits a weight ratio of Fe, calculated as Fe.sub.2O.sub.3, relative to Cu, calculated as CuO, Fe.sub.2O.sub.3:CuO, of less than 0.1:1. Further, the present invention relates to a specific process for preparing said catalyst. Yet further, the present invention relates to a system comprising said catalyst and to a use thereof.

Claims

1. A process for preparing a catalyst for the treatment of an exhaust gas of a diesel engine, comprising (i) preparing an aqueous mixture comprising water, a zeolitic material comprising Fe and having a framework structure type selected from the group consisting of CHA, AEI, RTH, LEV, DDR, KFI, ERI, AFX, a mixture of two or more thereof and a mixed type of two or more thereof, wherein the framework structure of the zeolitic material comprises Si, Al and O, the aqueous mixture further comprising a source of Cu and a first non-zeolitic oxidic material selected from the group consisting of alumina, silica, titania, zirconia, ceria, lanthana, praseodymium oxide, manganese oxide, a mixed oxide comprising one or more of Al, Si, Ti, Zr, La, Mn, Pr, and Ce, and a mixture of two or more thereof, wherein the aqueous mixture exhibits a weight ratio of Fe comprised in the zeolitic material, calculated as Fe.sub.2O.sub.3, relative to Cu comprised in the copper source, calculated as CuO, Fe.sub.2O.sub.3:CuO, of less than 0.1:1; (ii) disposing the aqueous mixture obtained in (i) on the surface of the internal walls of a substrate comprising an inlet end, an outlet end, a substrate axial length extending from the inlet end to the outlet end and a plurality of passages defined by internal walls of the substrate extending therethrough, over at least 55% of the substrate axial length; (iii) subjecting the substrate obtained in (ii) to a heat treatment in a gas atmosphere; obtaining the catalyst.

2. The process of claim 1, wherein in the framework structure of the zeolitic material according to (i), the molar ratio of Si to Al, calculated as molar ratio of SiO.sub.2:Al.sub.2O.sub.3, is in the range of from 1 to 50.

3. The process of claim 1, wherein the aqueous mixture according to (i) comprises the source of copper at an amount, calculated as CuO, in the range of from 0.025 to 7.5 weight-%, based on the sum of the weight of Si, calculated as SiO.sub.2, and the weight of Al, calculated as Al.sub.2O.sub.3, comprised in the framework structure of the zeolitic material comprised in the aqueous mixture according to (i).

4. The process of claim 1, wherein the zeolitic material according to (i) has a CHA framework structure type.

5. The process of claim 1, wherein the source of copper comprises CuO.

6. The process of claim 1, wherein the zeolitic material according to (i) has a CHA framework structure type and wherein the source of copper comprises CuO.

7. A catalyst for the treatment of an exhaust gas of a diesel combustion engine, obtainable or obtained by a process according to claim 1.

8. A catalyst for the treatment of an exhaust gas of a diesel combustion engine, said catalyst comprising (A) a substrate comprising an inlet end, an outlet end, a substrate axial length extending from the inlet end to the outlet end and a plurality of passages defined by internal walls of the substrate extending therethrough; (B) a coating disposed on the surface of the internal walls of the substrate according to (A) over at least 55% of the substrate axial length, the coating comprising a first non-zeolitic oxidic material, Cu, and a zeolitic material comprising Fe and having a framework structure type selected from the group consisting of CHA, AEI, RTH, LEV, DDR, KFI, ERI, AFX, a mixture of two or more thereof and a mixed type of two or more thereof, wherein the framework structure of the zeolitic material comprises Si, Al and O, wherein the first non-zeolitic oxidic material is selected from the group consisting of alumina, silica, titania, zirconia, ceria, lanthana, praseodymium oxide, manganese oxide, a mixed oxide comprising one or more of Al, Si, Ti, Zr, La, Mn, Pr, and Ce, and a mixture of two or more thereof; wherein the coating according to (B) exhibits a weight ratio of Fe, calculated as Fe.sub.2O.sub.3, relative to Cu, calculated as CuO, Fe.sub.2O.sub.3:CuO, of less than 0.1:1.

9. The catalyst of claim 8, wherein the zeolitic material comprised in the coating according to (B) has a CHA framework structure type.

10. The catalyst of claim 8, wherein the zeolitic material comprised in the coating according to (B) exhibits a molar ratio of silicon oxide to aluminum oxide, calculated as SiO.sub.2 to Al.sub.2O.sub.3, SiO.sub.2:Al.sub.2O.sub.3, in the range of from 1 to 50.

11. The catalyst of claim 8, wherein the copper comprised in the coating according to (B) is comprised in one or more of the zeolitic material comprised in the coating according to (B) and the first non-zeolitic oxidic material comprised in the coating according to (B).

12. The catalyst of claim 8, wherein the zeolitic material comprised in the coating according to (B) comprises Fe in an amount, calculated as Fe.sub.2O.sub.3, in the range of from 0.05 to 2 weight-%, based on the sum of the weight of Si, calculated as SiO.sub.2, and the weight of Al, calculated as Al.sub.2O.sub.3, comprised in the framework structure of the zeolitic material comprised in the coating according to (B).

13. The catalyst of claim 8, comprising the first non-zeolitic oxidic material comprised in the coating according to (B) at an amount in the range of from greater than 0 to 20 weight-%, based on the sum of the weight of Si, calculated as SiO.sub.2, and the weight of Al, calculated as Al.sub.2O.sub.3, comprised in the framework structure of the zeolitic material comprised in the coating according to (B).

14. The catalyst of claim 8, wherein the zeolitic material comprised in the coating according to (B) is disposed on the surface of the internal walls of the substrate according to (A) at a loading in the range of from 1.00 to 4.50 g/in.sup.3.

15. The catalyst of claim 8, having a Fe loading, calculated as Fe.sub.2O.sub.3, in the range of from 0.001 to 0.030 g/in.sup.3.

16. The catalyst claim 8, having a Cu loading, calculated as CuO, in the range of from 0.08 to 0.18 g/in.sup.3.

17. The catalyst of claim 8, having a loading of the coating according to (B) in the range of from 1.0 to 5.0 g/in.sup.3.

18. A system for the treatment of an exhaust gas of a diesel combustion engine, the system comprising a diesel oxidation catalyst, a catalyzed soot filter, and a catalyst according to claim 8, wherein in said system, the diesel oxidation catalyst is located upstream of the catalyzed soot filter, and wherein the catalyzed soot filter is located upstream of said catalyst according to claim 8.

19. A method of treating an exhaust gas of a diesel combustion engine, said method comprising bringing said exhaust gas in contact with a catalyst according to claim 8.

20. A method of treating an exhaust gas of a diesel combustion engine, said method comprising passing said exhaust gas through a system according to claim 18.

Description

BRIEF DESCRIPTION OF FIGURES

[0280] FIG. 1: shows the NOx conversion at the maximum NH.sub.3 slip at temperatures of 160 C., 500 C. and 600 C., and the NOx conversion at 10 ppm NH.sub.3 slip at 180 C., for Example 1, Reference Example 3, and Comparative Example 1. The temperature in C. is shown on the abscissa and the NOx conversion in % is shown on the ordinate.

[0281] FIG. 2: shows the high temperature N.sub.2O make (designated as N.sub.2O slip in ppm) at 160 C., 180 C., 500 C. and 600 C. for Example 1, Reference Example 3, and Comparative Example 1.

[0282] FIG. 3: shows the NOx conversion at temperatures of 220 C., 575 C. and 630 C. for Examples 3-7, and Comparative Example 2. The examples are listed on the abscissa and the NOx conversion in % is shown on the ordinate.

[0283] FIG. 4: shows the N.sub.2O emissions at temperatures of 220 C., 575 C. and 630 C. for Examples 3-7, and Comparative Example 2. The examples are listed on the abscissa and the N.sub.2O slip in ppm is shown on the ordinate.

[0284] FIG. 5: shows the N.sub.2O emissions at temperatures of 200 C., 220 C., 580 C. and 630 C. for Examples 9-12, and Comparative Example 2. The examples are listed on the abscissa and the N.sub.2O slip in ppm is shown on the ordinate.

[0285] FIG. 6: shows the NOx conversion at NH.sub.3 slip for Examples 14-15 and Comparative Example 3. The temperature in C. is shown on the abscissa and the NOx conversion in % is shown on the ordinate.

[0286] FIG. 7: shows the NOx conversion and the NH.sub.3 slip for Examples 14-15 and Comparative Example 3. The time in s is shown on the abscissa, the NOx conversion in % and the NH.sub.3 slip in ppm is shown on the ordinate.

[0287] FIG. 8: shows the N.sub.2O slip at maximum NOx conversion for Examples 14-15 and Comparative Example 3. The temperature in C. is shown on the abscissa and the N.sub.2O slip in ppm is shown on the ordinate.

[0288] FIG. 9: shows the procedural details for the temperature ramp test. The time in s is shown on the abscissa, the urea inlet in mg/s, the temperature in C. and the NOx inlet in ppm are shown on the ordinate.

[0289] FIG. 10: shows the NOx conversion for the catalysts of Example 15 and Comparative Example 3. The temperature in C. is shown on the abscissa, the NOx conversion in % is shown on the left ordinate and the NH.sub.3 slip in ppm is shown on the right ordinate.

[0290] FIG. 11: shows the N.sub.2O slip for the catalysts of Example 15 and Comparative Example 3. The temperature in C. is shown on the abscissa and the N.sub.2O slip in ppm is shown on the ordinate.

[0291] FIG. 12: shows the NOx conversion for the catalysts of Example 15, 18 and Comparative Example 3 at a temperature of 210 C. and a normalized stoichiometric ratio (NSR) of NH.sub.3 to NOx of 1.5, at a temperature of 260 C. and a normalized stoichiometric ratio (NSR) of NH.sub.3 to NOx of 1.5, at a temperature of 600 C. and a normalized stoichiometric ratio (NSR) of NH.sub.3 to NOx of 1, and at a temperature of 600 C. and a normalized stoichiometric ratio (NSR) of NH.sub.3 to NOx of 3. The examples are listed on the abscissa, the NOx conversion in % is shown on the ordinate.

[0292] FIG. 13: shows the N.sub.2O slip for the catalysts of Example 15, 18 and Comparative Example 3 at a temperature of 210 C. and a normalized stoichiometric ratio (NSR) of NH.sub.3 to NOx of 1.5, at a temperature of 260 C. and a normalized stoichiometric ratio (NSR) of NH.sub.3 to NOx of 1.5, at a temperature of 600 C. and a normalized stoichiometric ratio (NSR) of NH.sub.3 to NOx of 1, and at a temperature of 600 C. and a normalized stoichiometric ratio (NSR) of NH.sub.3 to NOx of 3. The examples are listed on the abscissa and the N.sub.2O slip in ppm is shown on the ordinate.

CITED LITERATURE

[0293] US 2015/0290632 A1 [0294] CN 104607239 A [0295] WO 2020/063360 A1 [0296] WO 2017/134581 A1