HONEYCOMB CATALYST FOR REMOVAL OF NITROGEN OXIDES IN FLUE AND EXHAUST GASSES AND METHOD OF PREPARATION THEREOF

Abstract

A vanadium oxide based honeycomb SCR catalyst composed of a plurality of corrugated sheets stacked upon one another to form a plurality of flow through channels, the corrugated sheets are provided with an inert inner core layer and an outermost layer containing a SCR catalyst composition.

Claims

1. A honeycomb SCR catalyst composed of a plurality of corrugated sheets stacked upon one another to form a plurality of flow through channels, each corrugated sheet comprising an inner core layer comprising entangled non-woven fibers coated with a clay material on both sides of each of the corrugated sheets, and an outermost layer supported on both sides of the inner core layer, the outermost layer comprising an SCR catalyst composition, the inner core layer makes up between 50% and 95% of the channel walls thickness.

2. The honeycomb catalyst of claim 1, wherein the non-woven fibers are glass fibers.

3. The honeycomb catalyst of claim 1, wherein the inner core material further comprises diatomaceous earth.

4. The honeycomb catalyst of claim 1, wherein the outermost layers have a layer thickness of between 0.05 mm and 0.6 mm.

5. The honeycomb catalyst of claim 1, wherein the inner core layer has a layer thickness of between 0.6 mm and 1.2 mm.

6. The honeycomb catalyst of claim 1, wherein the SCR catalyst composition comprises titania and an oxide of vanadium.

7. The honeycomb catalyst of claim 6, wherein the oxide of vanadium is vanadium pentoxide in an amount of between 1 and 5% per weight.

8. The honeycomb catalyst of claim 6, further comprising an oxide of tungsten.

9. The honeycomb catalyst of claim 1, further comprising a liner arranged on each of the corrugated sheets.

10. The honeycomb catalyst of claim 2, wherein the inner core layer further comprises diatomaceous earth.

11. Method of preparing a honeycomb SCR catalyst with a plurality of flow through channels comprising the steps of (a) providing sheets of entangled non-woven fibers; (b) corrugating the sheets; (c) stacking the corrugated sheets obtained in step (b) to form a honeycomb structure substrate; (d) coating the corrugated sheets of the honeycomb structured substrate with a clay material to obtain an inner core layer in each of the corrugated sheets and drying and/or calcining the honeycomb structured substrate; (e) coating each side of the inner core layer of each of the corrugated sheets in the honeycomb structured substrate with a catalyst coat layer comprising an SCR catalyst composition or a precursor thereof; and (f) calcining the honeycomb structured substrate of step (e) to obtain the honeycomb SCR catalyst.

12. The method of claim 11, wherein each corrugated sheet obtained in step (b) is lined with a liner prior to stacking.

13. The method of claim 11, wherein the liner is coated with a clay material.

14. The method of claim 11, wherein the non-woven fibers are glass fibers.

15. The method of claim 11, wherein the clay material further comprises diatomaceous earth.

16. The method of claim 11, wherein the catalyst coat layer has a layer thickness of between 0.05 mm and 0.6 mm.

17. The method of claim, wherein the inner core layer has a layer thickness of between 0.6 mm and 1.2 mm.

18. The method of claim 11, wherein the SCR catalyst composition comprises titania and an oxide of vanadium.

19. The method of claim 18, wherein the oxide of vanadium is vanadium pentoxide applied in an amount of between 1 and 5% per weight.

20. The method of claim 18, wherein the SCR catalyst composition further comprises an oxide of tungsten.

Description

[0016] Specific features of the catalyst according to the invention are alone or in combination thereof that

[0017] the non-woven fibers are glass fibers;

[0018] the inner core layer further comprises diatomaceous earth;

[0019] the inner core layers have a layer thickness of between 0.6 mm and 1.2 mm;

[0020] the outermost layers have a layer thickness of between 0.05 mm and 0.6 mm;

[0021] the SCR catalyst composition comprises titania and vanadium pentoxide;

[0022] the SCR catalyst composition comprises titania, vanadium pentoxide and an oxide of tungsten;

[0023] the amount of vanadium pentoxide in the outermost layer is between 1 and 5% per weight;

[0024] the SCR catalyst further comprises a liner arranged on each of the corrugated sheets.

[0025] A further aspect of the present invention is a method of preparing a honeycomb SCR catalyst with a plurality of flow through channels comprising the steps of

(a) providing sheets of entangled non-woven fibers;
(b) corrugating the sheets;
(c) stacking the corrugated sheets obtained in step (b) to form a honeycomb structured substrate;
(d) coating the corrugated sheets of the honeycomb structured substrate with a clay material to obtain an inner core layer in each of the corrugated sheets and drying and/or calcining the honeycomb structured substrate;
(e) coating each side of the inner core layer of each of the corrugated sheets in the honeycomb structured substrate with a catalyst coat layer comprising an SCR catalyst composition or a precursor thereof; and
(f) calcining the coated honeycomb structured substrate of step (e) to obtain the honeycomb SCR catalyst.

[0026] Specific features of the method according to the invention are alone or in combination thereof that

[0027] each corrugated sheet obtained in step (b) is lined with a liner prior to stacking;

[0028] the non-woven fibers are glass fibers;

[0029] the inner core material further comprises diatomaceous earth;

[0030] the catalyst coat layer has a layer thickness of between 0.05 mm and 0.3 mm;

[0031] the inner core layer has a layer thickness of between 0.6 mm and 1.2 mm;

[0032] the SCR catalyst composition comprises titania and an oxide of vanadium;

[0033] the oxide of vanadium is vanadium pentoxide applied in an amount of between 1 and 5% per weight in the outermost layer; and

[0034] the SCR catalyst composition further comprises an oxide of tungsten;

[0035] In all features and aspects the clay material can be selected from the kaolin group, hydrous alumina silicates, the chlorite group, the pyrophillite group, bentonite or mixtures thereof.

EXAMPLES

[0036] FIG. 1 shows the ratio of the DeNOx activity to the activity for SO.sub.2 oxidation of a honeycomb SCR catalyst according to the invention with an inner core layer thickness of 0.7 mm and a catalyst outer layer thickness of 0.15 mm on each side of the core layer compared to the known honeycomb SCR catalyst with a full catalyst layer supported on corrugated glassfiber paper. Both ratios have been normalized to the value of the full catalyst layer. The ideal is to have as high a ratio of DeNOx activity to SO.sub.2 oxidation activity.

[0037] As apparent from FIG. 1, the inert inner core catalyst according to the invention is about 58% higher/better in terms of DeNOx: SO.sub.2 oxidation activity, compared to the full catalyst layer.