A COMPOSITION FOR SCR CATALYSTS

Abstract

The present invention relates to a composition comprising a non-zeolitic oxidic material comprising alumina; an 8-membered ring pore zeolitic material comprising one or more of copper and iron, wherein the framework structure of the zeolitic material comprises a tetravalent element Y, a trivalent element X and oxygen, wherein the molar ratio of Y:X, calculated as YO.sub.2X.sub.2O.sub.3, is in the range of from 2: 1 to 40: 1; wherein at least part of the outer surface of the zeolitic material is covered by a layer comprising the non-zeolitic oxidic material; wherein Y comprises one or more of Si, Sn, Ti, Zr and Ge and X comprises one or more of Al, B, In and Ga.

Claims

1-17. (canceled)

18. A composition comprising: (i) a non-zeolitic oxidic material comprising alumina; and (ii) an 8-membered ring pore zeolitic material comprising one or more of copper and iron, wherein a framework structure of the zeolitic material comprises a tetravalent element Y, a trivalent element X and oxygen, wherein the molar ratio of Y:X, calculated as YO.sub.2:X.sub.2O.sub.3, ranges from 2:1 to 40:1; wherein at least part of the outer surface of the zeolitic material according to (ii) is covered by a layer comprising the non-zeolitic oxidic material according to (i); and wherein Y comprises one or more of Si, Sn, Ti, Zr and Ge and X comprises one or more of Al, B, In and Ga.

19. The composition of claim 18, wherein from 98 weight-%to 100 weightof the non-zeolitic oxidic material according to (i) consist of alumina.

20. The composition of claim 18, wherein the layer comprising the non-zeolitic oxidic material according to (i) has an average thickness ranging from 2 nm to 100 nm.

21. The composition of claim 18, wherein from 99 weight-%to 100 weight-%, of the layer consist of the non-zeolitic oxidic material according to (i).

22. The composition of claim 18, wherein the 8-membered ring pore zeolitic material according to (ii) has a framework type selected from the group consisting of CHA, AEI, RTH, LEV, DDR, KFI, ERI, AFX, LTA, a mixture of two or more thereof and a mixed type of two or more thereof, preferably selected from the group consisting of CHA, AEI, RTH, a mixture of two or more thereof and a mixed type of two or more thereof, more preferably selected from the group consisting of CHA and AEI.

23. The composition of claim 18, wherein from 20 %to 100 %, of the outer surface of the zeolitic material according to (ii) are covered by the layer comprising the non-zeolitic oxidic material according to (i).

24. A slurry comprising a composition according to claim 18 and a dispersion agent, wherein the dispersion agent is one or more of water, ethanol, acetic acid, nitric acid, lactic acid, and a mixture of two or more thereof.

25. A process for preparing a composition, the process comprising: (a) providing an 8-membered ring pore zeolitic material, comprising one or more of copper and iron, wherein a framework structure of the zeolitic material comprises a tetravalent element Y, a trivalent element X and oxygen, wherein the molar ratio of Y:X, calculated as YO.sub.2:X.sub.2O.sub.3, ranges from 2:1 to 40:1, wherein the zeolitic material comprises crystals having an average crystal size in the range of from 0.05 micrometers to 5 micrometers; (b) providing a source of a non-zeolitic oxidic material comprising alumina, wherein the source of the non-zeolitic oxidic material is a colloid dispersion comprising particles of the non-zeolitic oxidic material, wherein the particles of the non-zeolitic oxidic material have a Dv50 ranging from 30 nm to 200 nm; (c) admixing the zeolitic material obtained in (a) with the source of the non-zeolitic oxidic material comprising alumina obtained in (b), forming a mixture; and (d) calcining the mixture obtained in (c) in a gas atmosphere having a temperature ranging from 400° C. to 800° C.

26. The process of claim 25, wherein the crystals of the 8-membered ring pore zeolitic material have an average crystal size ranging from 0.06 micrometers to 2 micrometers.

27. The process of claim 25, wherein the 8-membered ring pore zeolitic material comprises particles having a Dv50 ranging from 0.5 micrometers to 4 micrometers.

28. The process of claim 25, wherein the colloid dispersion comprising particles of the non-zeolitic oxidic material provided in (b) is alumina sol.

29. The process of claim 25, wherein the particles of the non-zeolitic oxidic material, the particles of alumina, have a Dv50 ranging from 50 nm to 150 nm.

30. A selective catalytic reduction catalyst for treating an exhaust gas of a combustion engine, the catalyst comprising: (1) 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; (2) a coating disposed on the substrate (i), the coating comprising a composition according to claim 18.

31. The catalyst of claim 30, wherein the coating (2) further comprises an oxidic binder, wherein the oxidic binder comprises one or more of zirconia, alumina, titania, silica, and a mixed oxide comprising two or more of Zr, Al, Ti, and Si.

32. The catalyst of claim 30, wherein the coating (2) comprises the composition in an amount ranging from 80 weight-%to 100 weight-%, based on the weight of the coating (2).

33. The catalyst of claim 30, wherein the substrate is a wall-flow filter substrate, wherein the plurality of passages comprises inlet passages having an open inlet end and a closed outlet end, and outlet passages having a closed inlet end and an open outlet end.

34. A process for preparing the selective catalytic reduction catalyst for treating an exhaust gas of a combustion engine, the process comprising (A) preparing a mixture comprising water and a composition according to claim 18; (B) disposing the mixture obtained according to (A) on a substrate, the 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, obtaining a mixture-treated substrate; (C) calcining the mixture-treated substrate obtained according to (B), obtaining the substrate having a coating disposed thereon.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0237] FIG. 1 TEM micrograph of the Cu-Chabazite + alumina-silica used in Comparative Example 1.

[0238] FIG. 2 2.1: TEM micrograph of the Cu-Chabazite + alumina used in Example 1. 2.2: TEM micrograph of the Cu-Chabazite + alumina in Example 2. The white arrows show the alumina layer on the outer surface of the zeolitic material.

[0239] FIG. 3 shows the NOx conversion measured for the catalysts of Comparative Example 1 and of Examples 1 and 2 at 200° C. (SV: 40 k/h).

[0240] FIG. 4 shows the NOx conversion measured for the catalysts of Comparative Example 1 and of Examples 1 and 2 at 600° C. (SV: 40 and 80 k/h).

[0241] FIG. 5 shows the cold flow backpressure recorded for the catalysts of Comparative Example 1 and of Examples 1 and 2 at a volume flow of 27 m.sup.3/h.

[0242] FIG. 6 shows the NOx conversion measured for the catalysts of Comparative Examples 2 and 3 and of Example 4 at 220° C. at 20 ppm NH.sub.3 and at 660° C. at maximum NH.sub.3 slip.

[0243] FIG. 7 shows the cold flow backpressure recorded for the catalysts of Comparative Examples 2 and 3 and of Example 4 at a volume flow of 65 m.sup.3/h.

[0244] FIG. 8 shows the measurements of the average thickness of a layer comprising a non-zeolitic oxidic material (10 wt.% of alumina based on the weight of the zeolitic material - FIG. 8.1 and 30 wt.% of alumina based on the weight of the zeolitic material - FIG. 8.2).

[0245] Cited literature [0246] US 2013/0101503 A1 [0247] US 2017/7050182 A1 [0248] CN 108993579 A [0249] WO 2019/225909 A