METHOD FOR PREPARING A CATALYZED FABRIC FILTER

Abstract

Method for preparing a catalytic fabric filter comprising the steps of a) providing a fabric filter substrate, preferably consisting of glass fibers, having a gas inlet surface and a gas outlet surface, the gas inlet surface is coated with a polymeric membrane, preferably consisting of polytetrafluoroethylene; b) providing an aqueous impregnation liquid comprising one or more catalyst metal precursor compounds; c) impregnating the fabric filter substrate with the impregnation liquid; and d) drying and thermally activating the impregnated fabric filter substrate at a temperature below 300 C. to convert the one or more metal compounds of the catalyst precursor to their catalytically active form, wherein the drying of the impregnated fabric filter substrate in step d) is performed from the gas outlet surface.

Claims

1. A method for preparing a catalyzed fabric filter comprising the steps of a) providing a fabric filter substrate having a gas inlet surface and a gas outlet surface, the gas inlet surface is coated with a polymeric membrane; b) providing an aqueous impregnation liquid comprising one or more catalyst metal precursor compounds; c) impregnating the fabric filter substrate with the impregnation liquid; and d) drying and thermally activating the impregnated fabric filter substrate at a temperature below 300 C. to convert the one or more metal compounds of the catalyst precursor to their catalytically active form, wherein the drying of the impregnated fabric filter substrate in step d) is performed solely from the gas outlet surface.

2. The method of claim 1, wherein the thermally activation in step d) is performed from the gas outlet surface.

3. The method of claim 1, wherein the impregnating of the fabric filter substrate is performed from the gas outlet surface.

4. The method of claim 1, wherein the fabric filter substrate is in form of a bag.

5. The method of claim 4, wherein the gas outlet surface of the bag is turned out prior to step c) and/or step d).

6. The method of claim 1, wherein the fabric filter substrate consists of woven or non-woven glass fibers.

7. The method of claim 1, wherein the polymeric membrane consists of polytetrafluoroethylene.

8. The method of claim 1, wherein the one or more catalyst metal precursor compounds comprise ammonium metavanadate, ammonium metatungstate, ammonium heptamolybdate, palladium nitrate, tetraammineplatinum(II) hydrogen carbonate or mixtures thereof.

9. The method of claim 1, wherein the catalytically active form of the one or more catalyst metal precursor compounds comprises one or more of vanadium oxide, tungsten oxide, molybdenum oxide, manganese oxide, copper oxide, iron oxide, and palladium and platinum in the oxidic and/or metallic form.

10. The method of claim 9, wherein the catalytically active form of the one or more catalyst metal precursor compounds consists of vanadium pentoxide and palladium in metallic and/or oxidic form.

11. The method of claim 1, wherein the oxidic metal carrier comprises oxides of titanium, aluminum, cerium, zirconium or mixtures and compounds thereof.

12. The method of claim 11, wherein the oxidic metal carrier consists of nanoparticles of titanium oxide with a particle size of between 10 and 150 nm.

13. The method of claim 1, wherein aqueous impregnation liquid comprises a dispersing agent comprising a primary amine selected from one or more of the group consisting of mono methyl amine, mono ethyl amine, mono propyl amine and mono butyl amine.

14. The method of claim 13, wherein the dispersing agent consists of mono ethyl amine.

15. The method of claim 13, wherein the dispersing agent is added to the aqueous impregnation liquid in an amount resulting in a pH value above 7 of the impregnation liquid.

16. The method of claim 1, wherein the catalyzed fabric substrate comprises from about 5 to about 15% by weight of catalytically active material.

17. The method of claim 1, wherein the one or more catalyst precursor metal compounds are ammonium metavanadate and palladium nitrate.

18. A catalyzed fabric filter substrate prepared by a method according to claim 1.

Description

EXAMPLE 1

[0043] Filter bags were wetted with catalytic liquid, dried from the gas inlet surface and heat treated at >240 C. Thereby, the catalyst was mainly placed on the exterior membrane side. The catalytic liquid was diluted with water in order to vary the amount of catalyst, see Table 1.

TABLE-US-00001 TABLE 1 Permeability Wt % at 200 Pa, Sample Drying Catalyst l/m.sup.2/s Xblank none 0 65.2 A From gas 3.25 22.6 inlet B From gas 4.7 19.1 inlet C From gas 6.8 20.9 inlet D From gas 10.2 20.8 inlet E From gas 13.5 15.3 inlet

EXAMPLE 2

[0044] Filter bags were wetted with catalytic liquid, dried from the gas outlet surface and heat treated at >240 C. Thereby, the catalyst was mainly placed on the interior side and not on the membrane. The catalytic liquid was diluted with water in order to vary the amount of catalyst, see Table 2.

TABLE-US-00002 TABLE 2 Permeability Wt % at 200 Pa, Sample Drying Catalyst l/m.sup.2/s Xblank none 0 65.2 F From gas 6.6 65.7 outlet G From gas 6.6 62.4 outlet H From gas 10.0 58.6 outlet I From gas 10.0 49.1 outlet