EXHAUST GAS TREATMENT SYSTEM FOR ULTRA LOW NOX AND COLD START

Abstract

The present invention relates to an exhaust gas treatment system for treating an exhaust gas stream leaving an internal combustion engine, wherein said exhaust gas treatment system comprises (i) a first catalyst comprising a coating and a first substrate, wherein the coating comprises a vanadium oxide supported on a first oxidic support comprising titanium; (ii) a hydrocarbon injector for injecting a fluid comprising hydrocarbons into the exhaust gas stream exiting the outlet end of the first catalyst according to (i); (iii) a second catalyst comprising a coating and a second substrate, wherein the coating comprises palladium on a second oxidic support comprising one or more of zirconium, silicon, aluminum and titanium.

Claims

1-15. (canceled)

16. An exhaust gas treatment system for treating an exhaust gas stream leaving an internal combustion engine, the exhaust gas treatment system having an upstream end for introducing the exhaust gas stream into the exhaust gas treatment system, wherein the exhaust gas treatment system comprises (i) a first catalyst having an inlet end and an outlet end and comprising a coating and a first substrate, wherein the first substrate has an inlet end, an outlet end and a substrate axial length extending from the inlet end to the outlet end of the first substrate and comprises a plurality of passages defined by internal walls, wherein the interface between the passages and the internal walls is defined by the surface of the internal walls, wherein the coating is disposed on the surface of the internal walls of the first substrate and the coating comprises a vanadium oxide supported on a first oxidic support comprising titanium; (ii) a hydrocarbon injector for injecting a fluid comprising hydrocarbons into the exhaust gas stream exiting the outlet end of the first catalyst according to (i); and (iii) a second catalyst having an inlet end and an outlet end and comprising a coating and a second substrate, wherein the second substrate has an inlet end, an outlet end and a substrate axial length extending from the inlet end to the outlet end of the second substrate and comprises a plurality of passages defined by internal walls, wherein the interface between the passages and the internal walls is defined by the surface of the internal walls, wherein the coating is disposed on the surface of the internal walls of the second substrate and the coating comprises palladium on a second oxidic support comprising one or more of zirconium, silicon, aluminum and titanium; wherein the first catalyst according to (i) is the first catalyst of the exhaust gas treatment system downstream of the upstream end of the exhaust gas treatment system and wherein the inlet end of the first catalyst is arranged upstream of the outlet end of the first catalyst; wherein in the exhaust gas treatment system, the second catalyst according to (iii) is located downstream of the first catalyst according to (i) and downstream of the hydrocarbon injector according to (ii) and wherein the inlet end of the second catalyst is arranged upstream of the outlet end of the second catalyst.

17. The system of claim 16, wherein the coating of the first catalyst comprises the vanadium oxide at an amount ranging from 1.0 weight-% to 10 weight-%, based on the weight of the first oxidic support.

18. The system of claim 16, wherein the first oxidic support further comprises one or more of tungsten, silicon, zirconium, and antimony; wherein the first oxidic support has from 80 weight-% to 98 weight-% titania, calculated as WO.sub.3.

19. The system of claim 16 wherein the second oxidic support comprises one or more of zirconium and aluminum; wherein the second oxidic support has a total of from 90 weight-% to 100 weight-%, aluminum, oxygen and optionally zirconium.

20. The system of claim 16, wherein the coating of the second catalyst according to (iii) comprises palladium ranging from 5 g/ft.sup.3 to 90 g/ft.sup.3.

21. The system of claim 20, wherein palladium is the only platinum group metal present in the coating of the second catalyst according to (iii).

22. The system of claim 16, wherein the coating of the second catalyst has from 98 weight-% to 100 weight-% palladium supported on the second oxidic support; wherein the second oxidic support comprises one or more of zirconium, silicon, aluminum, and titanium.

23. The system of claim 16, wherein the coating of the second catalyst according to (iii) further comprises a zeolitic material, the zeolitic material comprising one or more of Cu and Fe.

24. The system of claim 23, wherein the coating of the second catalyst according to (iv) further comprises from 0.5 weight-% to 10 weight-% of an oxidic binder, based on the total weight of the zeolitic material.

25. The system of claim 16, further comprising: (iv) a third catalyst having an inlet end and an outlet end and comprising a coating and a third substrate, wherein the third substrate has an inlet end, an outlet end and a substrate axial length extending from the inlet end to the outlet end of the third substrate and comprises a plurality of passages defined by internal walls, wherein the interface between the passages and the internal walls is defined by the surface of the internal walls, wherein the coating is disposed on the surface of the internal walls of the third substrate and the coating comprises one or more of a vanadium oxide and a zeolitic material comprising one or more of Cu and Fe; wherein in the exhaust gas treatment system, the third catalyst according to (iv) is located downstream of the second catalyst according to (iii) and wherein the inlet end of the third catalyst is arranged upstream of the outlet end of the third catalyst; wherein the outlet end of the second catalyst according to (iii) is in fluid communication with the inlet end of the third catalyst according to (iv) and wherein between the outlet end of the second catalyst according to (iii) and the inlet end of the third catalyst according to (iv), no catalyst for treating the exhaust gas stream exiting the second catalyst is located in the exhaust gas treatment system.

26. The system of claim 25, wherein the coating of the third catalyst according to (iv) comprises a zeolitic material comprising one or more of Cu and Fe; wherein the zeolitic material has a framework type AEI, GME, CHA, MFI, BEA, FAU, MOR or mixtures of two or more thereof.

27. The system of claim 25, wherein the coating of the second catalyst according to (iii) comprises palladium supported on the second oxidic support comprising one or more of zirconium, silicon, aluminum and titanium, and wherein the coating of the third catalyst according to (iv) comprises a zeolitic material comprising one or more of Cu and Fe.

28. The system of claim 25, further comprising a fourth catalyst, wherein the fourth catalyst is one or more of an ammonia oxidation catalyst, a catalyzed soot filter and a selective catalytic reduction catalyst; wherein the fourth catalyst has an inlet end and an outlet end and comprises a coating and a fourth substrate, wherein the fourth substrate has an inlet end, an outlet end and a substrate axial length extending from the inlet end to the outlet end of the fourth substrate and comprises a plurality of passages defined by internal walls, wherein the interface between the passages and the internal walls is defined by the surface of the internal walls, wherein the coating is disposed on the surface of the internal walls of the fourth substrate and the coating comprises an ammonia oxidation component, wherein in the exhaust gas treatment system, the fourth catalyst is located downstream of the third catalyst according to (iv) and wherein the inlet end of the fourth catalyst is arranged upstream of the outlet end of the fourth catalyst; wherein the outlet end of the third catalyst according to (iv) is in fluid communication with the inlet end of the fourth catalyst and wherein between the outlet end of the third catalyst and the inlet end of the fourth catalyst, no catalyst for treating the exhaust gas exiting the third catalyst is located in the exhaust gas treatment system.

29. The system of claim 16, further comprising an injector for injecting a fluid into the exhaust gas stream exiting the internal combustion engine, the injector being located upstream of the first catalyst and downstream of the upstream end of the exhaust gas treatment system; wherein no hydrocarbon injector is located upstream of the first catalyst and downstream of the upstream end of the exhaust gas treatment system.

30. A method for treating an exhaust gas stream leaving an internal combustion engine, the method comprising: (1) providing an exhaust gas stream from an internal combustion engine, wherein the exhaust gas stream comprises one or more of NOx, ammonia, nitrogen monoxide, and a hydrocarbon; (2) passing the exhaust gas stream provided in (1) through the exhaust gas system according to claims 16.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0386] FIG. 1 shows the NOx conversion of the V-SCR catalyst of Reference Example 4 at two different temperatures, namely at 200 and 250° C. The NOx conversion was measured at a space velocity of 50,000/hr, NO 500 ppm an NH.sub.3 500 ppm. It was apparent from this figure that the efficiency of the V-SCR catalyst is increased at higher temperatures, in particular the DeNOx is of about 78% at 200° C. and increased to more than 95% at 250° C.

[0387] FIG. 2 shows the responsiveness of the catalysts of Reference Example 4 (V-SCR catalyst) and of the catalyst of Reference Example 6 (Cu-SCR catalyst). The DeNOx was measured at 210° C. and a space velocity of 50,000/hr.

[0388] FIG. 3 shows a schematic view of an engine followed by an exhaust gas treatment system according to the present invention. In particular, the exhaust gas treatment system comprises a SCR catalyst, namely a V-SCR catalyst, a Pd-DOC which is located downstream of the V-SCR catalyst. Further, a HC injector is placed between the outlet end of the V-SCR catalyst and the inlet end of the Pd-DOC, and a first urea injector is placed upstream of the inlet end of the V-SCR catalyst. Further, the system comprises one of a first ammonia oxidation catalyst, a SCR catalyst and a mixed DOC/SCR, located downstream of the Pd-DOC. The system further comprises a second ammonia oxidation (AMOX) catalyst, and optionally a DOC at its outlet end. The system further comprises a catalyzed soot filter (CSF) downstream of the second AMOX catalyst and upstream of a SCR catalyst. Further a second urea injector is placed between the CSF and the SCR catalyst. Finally, the system further comprises a SCR catalyst or an AMOX catalyst.

[0389] FIG. 4 shows the temperatures at the inlet and outlet ends of the V-SCR catalyst in the system of Comparative Example 1 and the temperature at the outlet end of the Pd-DOC of the system of Comparative Example 1 relative to the time.

[0390] FIG. 5 shows the temperatures at the inlet and outlet ends of the Pd-DOC in the system of Example 1 relative to the time during a hydrocarbon injection event. In addition, the temperature of the upstream V-SCR is shown.

[0391] FIG. 6 shows the NOx conversion was measured at 215° C. under steady state conditions at the outlet of systems 1 and 2.

[0392] FIG. 7 shows the NOx conversion at the outlet end of the different catalysts forming the systems A, B and C at 290° C. (steady state).

[0393] FIG. 8 shows the nitrous oxide formed at the outlet end of the different catalysts forming the systems A, B and C at 290° C. (steady state).

[0394] FIG. 9 shows the NOx conversion at the outlet end of the different catalysts forming the systems A, B and C over a WHTC (transient).

[0395] FIG. 10 shows the nitrous oxide formed at the outlet end of the different catalysts forming the systems A, B and C over a WHTC (transient).

CITED LITERATURE

[0396] US 2017/152780 A

[0397] US 2018/258811 A1

[0398] WO 2018/224651 A2