SELECTIVE CATALYTIC REDUCTION CATALYST COMPOSITION

Abstract

A SCR catalyst composition comprises a SCR catalyst; and a binder comprising a porous inorganic material, wherein the porous inorganic material comprises a disordered arrangement of delaminated layers, has a disordered porous structure, and has a multimodal pore size distribution comprising at least a first modal maximum having a macroporous or mesoporous pore size and a second modal maximum having a microporous pore size. The SCR catalyst composition can be manufactured using the method comprising the steps of: (i) providing an inorganic material having a layered structure; (ii) contacting the material with a cationic surfactant to form a swollen material; (iii) agitating the swollen material to form an agitated material; and (iv) calcining the agitated material to recover a delaminated inorganic material, wherein an SCR catalyst is mixed with the inorganic material prior to step (iv).

Claims

1. A selective catalytic reduction (SCR) catalyst composition comprising: a SCR catalyst; and a binder comprising a porous inorganic material, wherein the porous inorganic material comprises a disordered arrangement of delaminated layers, has a disordered porous structure, and has a multimodal pore size distribution comprising at least a first modal maximum having a macroporous or mesoporous pore size and a second modal maximum having a microporous pore size.

2. The SCR catalyst composition of claim 1, wherein the multimodal pore size distribution is bimodal.

3. The SCR catalyst composition of claim 1, wherein a powder X-ray diffraction pattern of the porous inorganic material obtained using Cu K radiation is devoid of peaks at 2 values of 10 or less.

4. The SCR catalyst composition of claim 1, wherein the first modal maximum has a mesoporous and/or macroporous pore size.

5. The SCR catalyst of claim 1, wherein the delaminated layers are delaminated silicate layers.

6. The SCR catalyst composition of claim 1, wherein the porous inorganic material comprises one or more of: a clay mineral, graphite, graphene, a layered silicate, a layered phosphate, a layered zeolite, a layered double hydroxide, hydrotalcite, a layered perovskite, attapulgite, sepiolite and vermiculite.

7. The SCR catalyst composition of claim 6, wherein the porous inorganic material comprises a clay mineral comprising a three-layered (2:1) clay mineral.

8. The SCR catalyst composition of claim 7, wherein the clay mineral comprises bentonite.

9. The SCR catalyst composition of claim 1, wherein the porous inorganic material is substantially non-pillared.

10. The SCR catalyst composition of claim 1, wherein the porous inorganic material is functionalised with one or more of Cu, Fe, Ce, Mn, V, Zn, Mo, Pt, Pd, Rh, Ir and Ni.

11. The SCR catalyst composition of claim 1, wherein the porous inorganic material is functionalised with Cu and/or Fe.

12. The SCR catalyst composition of claim 1, wherein the SCR catalyst comprises a zeolite.

13. The SCR catalyst composition of claim 1, wherein the SCR catalyst comprises a titania and the porous inorganic material is functionalised with V and/or Fe.

14. The SCR catalyst composition of claim 13, wherein the titania comprises W, Si and/or Mo and the porous inorganic material is functionalised with V.

15. The SCR catalyst composition of claim 1, wherein the porous inorganic material comprises from 0.01 to 5 wt. % Fe.

16. The SCR catalyst composition of claim 1, wherein the SCR catalyst composition is extrudable.

17. The SCR catalyst composition of claim 1 in the form of pellets or a sheet or having a honeycomb structure.

18. An emission treatment system for treating a flow of a combustion exhaust gas, the system comprising a source of combustion exhaust gas in fluid communication with the SCR catalyst composition of claim 1, and a source of nitrogenous reductant arranged upstream of said SCR catalyst composition.

Description

[0075] The present disclosure will now be described in relation to the following non-limiting figures, in which:

[0076] FIG. 1 shows a flow chart of a method according to the present invention;

[0077] FIG. 2 shows powder X-ray diffraction patterns of Bentonite-U, Bentonite-S and Bentonite-DEL according to Example 1; and

[0078] FIG. 3 shows a N2 sorption pore size distribution of Bentonite-U and Bentonite-DEL according to Example 1.

[0079] Referring to FIG. 3, there is shown a method for the manufacture of a SCR catalyst composition, the method comprising: (i) providing an inorganic material having a layered structure; (ii) contacting the material with a cationic surfactant to form a swollen material; (iii) agitating the swollen material to form an agitated material; and (iv) calcining the agitated material to recover a delaminated inorganic material,

[0080] The present disclosure will now be described in relation to the following non-limiting examples.

EXAMPLE 1

[0081] A number of binders comprising a porous inorganic material were prepared. The starting material used was Bentonite-B (Witgert), which is composed of:

Si.sub.4O.sub.10(Al.sub.3.84Mg.sub.0.49)(Fe.sub.1.84Ca.sub.0.21)Na.sub.0.03(OH).sub.2.xH.sub.2O.

[0082] Step 1 (steps (i) and (ii) in the claimed method): In the first step, the small cations between the layers of the bentonite were exchanged using hexadecyltrimethylammonium bromide (CTAB). To this end, 30 g of CTAB and 13 g of tetrapropylammonium hydroxide (TPAOH, 40% solution) were dissolved in 116 ml of water under agitation (magnetic stirrer). Then, 5 g of bentonite were gradually admixed. The mixing took 20 minutes. The exchange was then carried out at 40 C. under continuous, gentle stirring for a period of 2 days.

[0083] Step 2 (steps (iii) and (iv) in the claimed method): In the second step, delamination of the layered structure was initiated by ultrasonication at room temperature. The treatment time was two hours. Thereafter, the solid fraction was separated from the dispersion by centrifugation and dried at 75 C. for 12 hours. This drying step was followed by a calcination at 550 C. in air for 5 hours. The heating rate for this was 1 K/min.

[0084] FIG. 2 shows powder X-ray diffraction patterns of the untreated bentonite material (Bentonite-U), the swollen bentonite after step 1 (Bentonite-S) and the delaminated clay after step 2 (Bentonite-DEL). It can be observed that a number of peaks decline in intensity after ultrasonication especially peaks from 2 to 10 2Theta, indicating a disordered arrangement of delaminated layers. A powder X-ray diffraction pattern of the bentonite material after swelling was also measured, from which the change in layer spacing on swelling could be observed.

[0085] FIG. 3 shows pore size distributions obtained from nitrogen sorption measurements for the untreated bentonite (Bentonite-U) and the delaminated bentonite (Bentonite-DEL). Compared to the untreated clay two pronounced maxima, one maximum in the micropore range and one maximum in the mesopore range, have been observed for the delaminated clay. In Table 1 the derived specific surface area and pore volume data are summarized showing an increase in meso- and macropore volume and therefore a significantly higher total pore volume and specific surface area for the delaminated bentonite material.

TABLE-US-00001 TABLE 1 Porosity characteristics by N.sub.2-sorption measurement Total pore Micropore Mesopore Macropore BET volume volume volume volume (m.sup.2/g) (cm.sup.3/g) (cm.sup.3/g) (cm.sup.3/g) (cm.sup.3/g) Bent - 107 0.174 0.041 0.110 0.023 U Bent - 165 0.342 0.025 0.283 0.034 DEL

EXAMPLE 2

[0086] The following SCR catalyst compositions were prepared: [0087] 1. 100 wt. % Cu-CHA zeolite (according to WO 2008/132452; comparative example); [0088] 2. 80 wt. % V-Ti-W/20 wt. % delaminated bentonite (present invention), 80wt. % Cu-CHA+20 wt. % Bentonite-U (comparative example); [0089] 3. 80 wt. % Cu-CHA+20 wt. % Bentonite-DEL; and [0090] 4. 80 wt. % Cu-CHA+20 wt. % Fe-Bentonite-DEL.,

[0091] Composition 4 was prepared by functionalising Bentonite-DEL with 2wt. % Fe (using Fe(NO.sub.3).sub.3 as source of Fe) by wet ion exchange. The Fe-Bentonite-DEL material was then mixed with the Cu-CHA SCR catalyst.

[0092] The NOx conversion activity of powder samples of each of compositions 1-4 were tested in a laboratory synthetic catalytic activity test (SCAT) apparatus using a gas mixture of 500 ppm NO, 550 ppm NH.sub.3, 8% O.sub.2, 10% H.sub.2O, rest N.sub.2 and the results are shown in Table 2. No N.sub.2O was detected. The results indicate higher NOx conversion with delaminated bentonite than non-delaminated bentonite, even higher conversion with the sample containing the Fe-Bentonite-DEL material. Composition 4 has nearly the same activity level as composition 1 (100 wt. % Cu-CHA).

TABLE-US-00002 TABLE 2 NOx conversion for SCR catalyst composition 1-4 (500 ppm NO, 550 ppm NH.sub.3, 8% O.sub.2, 10% H.sub.2O, rest N.sub.2; volume flux = 1000 ml min.sup.1; sample mass = 0.05 g) NOx Conversion (%) 200 C. 300 C. 400 C. 500 C. 1. 100% Cu-CHA 46 100 100 94 2. 80% Cu-CHA + 20% 26 74 91 92 Bentonite-U 3. 80% Cu-CHA + 20% 30 92 98 82 Bentonite-DEL 4. 80% Cu-CHA + 20% 45 100 100 91 Fe-Bentonite-DEL

EXAMPLE 3

[0093] The following four SCR catalyst compositions were prepared: [0094] 5. 100 wt. % V-Ti-W (according to U.S. Pat. No. 4,085,193; comparative example); [0095] 6. 70 wt. % V-Ti-W+30 wt. % Bentonite-U (comparative example); and [0096] 7. 70 wt. % V-Ti-W+30 wt. % Fe-Bentonite-DEL delaminated bentonite* functionalised with Fe

[0097] * As explained in Example 2, composition 3 was prepared by addition of 2wt. % Fe to the delaminated clay prior mixing with V-Ti-W SCR catalyst.

[0098] NOx conversion testing of powder samples of compositions 5-7 was carried out using a SCAT apparatus (Reaction conditions: 500 ppm NO, 550 ppm NH.sub.3, 8% O.sub.2, 10% H.sub.2O, rest N.sub.2) and the results are shown in Table 3. No N.sub.2O was detected. Composition 7 shows higher NOx conversion compared to Composition 6 at high temperatures and nearly the same level of conversion at 500 C. compared to composition 5 (100% V-Ti-W SCR catalyst).

TABLE-US-00003 TABLE 3 NOx conversion for SCR catalyst composition 5-7 (500 ppm NO, 550 ppm NH.sub.3, 8% O.sub.2, 10% H.sub.2O, rest N.sub.2; volume flux = 1000 ml min.sup.1; sample mass = 0.05 g). NOx Conversion [%] 200 C. 300 C. 400 C. 500 C. 5. 100% VTiW 7 49 79 70 6. 70% VTiW + 30% 5 38 53 50 Bentonite-U 7. 70% VTiW + 30% 5 37 60 65 Fe-DEL-Bentonite

[0099] The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art, and remain within the scope of the appended claims and their equivalents.

[0100] For the avoidance of doubt, the entire contents of all documents acknowledged herein are incorporated herein by reference.