DD296854A5 - CATALYST FOR THE SELECTIVE REDUCTION OF NITROGEN OXIDES WITH AMMONIA - Google Patents

Abstract

The invention relates to a catalyst for the selective reduction of nitrogen oxides with ammonia in exhaust gases from boiler furnaces, the components A) titanium oxide, B1) at least one oxide of tungsten, silicon, boron, aluminum, phosphorus, zirconium, barium, yttrium, lanthanum, cerium and B2) at least one oxide of vanadium, niobium, molybdenum, iron, copper, wherein the atomic ratio between the components A) and B) is 1: 0.001 to 1. The catalyst according to the invention is obtainable by kneading reactive titanium oxide of high specific surface predominantly anatase with the substances of component B) or their precursors with the addition of processing agents to a homogeneous kneading material, extruding this, drying the extrudate and calcining in air at 300-800C. {Catalyst; selective reduction; nitrogen oxides; Ammonia; exhaust gases; Boiler combustion plants; titanium oxide; Oxides of W, Si, B, Al, P, Zo, Ba, Y, La, Ce, V, Nb, Mo, Fe, Cu}

Description

For this 3 pages drawings

Field of application of the invention

The invention relates to a catalyst for the selective reduction of nitrogen oxides with ammonia in exhaust gases from boiler combustion systems, internal combustion engines u.a.

Characteristic of the known state of the art

Nitrogen oxides, which are produced during combustion processes, are among the main causes of acid rain or photo smog and the associated environmental damage. In particular, the nitrogen oxides are suspected in addition to the chlorofluorocarbons to be responsible for the observed decrease in the ozone layer over the polar regions.

Sources of nitrogen oxide emissions include motor vehicle traffic, stationary internal combustion engines, power plants, cogeneration plants, industrial steam generators and industrial production plants.

In power plants with boiler firing can be achieved by using very pure fuels or by optimizing the Combustion systems (primary measures) are achieved a reduction of the nitrogen oxide concentration in the exhaust gas, but this

Firing measures are set both technical and economic limits. Secondary measures must therefore be taken to comply with the legally prescribed emission limit values. Such

Secondary measures for nitrogen oxide reduction are usually catalytic reduction process, with mostly ammonia

is used as a selective reducing agent.

A large number of catalysts for reductive catalytic nitrogen oxide reduction are already known. So be in the DE-AS 1259298, 1253685 and 1115230 oxide catalysts without precious metal and in DE-OS 2214604 oxidic,

noble metal-containing catalysts described.

In DE-PS 2458888 another catalyst is described which consists of an "intimate mixture" of the following Components consists of: A) Titanium in the form of oxides B) at least one metal from the group: B-1 iron and vanadium in the form of oxides

and / or the group

B-2 Molybdenum, tungsten, nickel, cobalt, copper, chromium and uranium in the form of oxides C) tin in the form of oxides

D) metals from the group beryllium, magnesium, zinc, boron, aluminum, yttrium, rare earth elements, silicon, niobium, antimony, bismuth and manganese in the form of oxides.

The components are in the atomic ratios A to B to C to D = 1 to 0.01 to 10 to 0 to 0.2 to 0 to 0.15 A catalyst of this composition is for the reduction of oxygen and ammonia-containing gas mixtures in Temperature range of 150 to 550 "C and at space velocities of 300-10000Oh ' ¹ used. The preparation of these catalysts can be done by measures known per se; but they always have to

ensure that the components A) and B) and optionally C) can be obtained as an intimate mixture in the form of their oxides. As typical examples of such production methods are mentioned:

1 a: Homogeneous solution method

1 b: Coprecipitation method

2: Simultaneous application of solution and precipitation method

3: precipitate mixing method.

As precursors of components A), B) and C) are solutions and / or precipitates such. As hydroxides or hydrous Gels used, which are mixed to an intimate mixture and then subjected to a calcination. It will be

the precursors are pyrolyzed to give the desired intimate mixture of the oxides of the catalysis critical components.

The calcination temperature should be between 300 and 800 ⁰ C. Below 300 ⁰ C, an intimate mixture of oxides and thus a

active catalyst can not be obtained; Above 800 ⁰ C sintering takes place, resulting in the loss of the effective

Catalyst surface leads. As starting material for titanium as component A), for example, various titanic acids, titanium hydroxide and

various titanium salts such as halides, titanium sulfate, titanyl sulfate and the like are used. Also, organic compounds of titanium, for example, titanium alkoxides, may serve as a starting material for the titanium. Titanium oxide is not usable in the calcined rutile and anatase form.

A further development of this catalyst preparation process described in DE-AS 2458888 is the in the DE-PS 3531809 described catalyst. As starting material for the preparation of this catalyst composition

Titanium dioxide is used and this together with vanadium oxide and one or more oxides of the elements tungsten,

Molybdenum, phosphorus, chromium, copper, iron, uranium and then at least one thermal treatment

subjected. Tungsten and molybdenum are wholly or partially substituted by phosphorus in the form of its oxides or phosphates. As mills, eccentric disk mills and annular chamber mills are preferred. Calcination takes place in

Temperature range from 200 to 900 ° C. It is essential in all previously known catalysts of this type that the components A) and B) (eg A = Ti, B = W, Mo, etc.)

be present as an intimate mixture in the form of their oxides. This is then subjected to a shaping process, from which the

Catalysts are obtained by compression or extrusion in the form of bulk or monoliths in honeycomb form

can.

This means that the catalyst forming, such as extrusion molding, must be preceded by a process involving the Formation of the intimate mixture as a starting material has the goal. This usual procedure has the following

Disadvantage:

- There are technically complex, multi-stage, energy-intensive process steps necessary;

- The production of the intimate mixture according to DE-AS 2458888 is polluting, there are exhaust air and wastewater problems;

- The operation of grinders for Mahlaktivierung is energy-intensive and requires complex noise protection and dust control devices;

- The upstream process steps to form the intimate mixture are a serious cost factor in catalyst production.

The object of the invention is to provide an improved process for the preparation of a catalyst for the selective reduction of nitrogen oxides containing titanium oxide and at least one oxide of tungsten, silicon, boron, aluminum, phosphorus, zirconium, barium, yttrium, Lautahn, cerium, vanadium, niobium, Molybdenum, iron, copper.

Explanation of the essence of the invention The invention is therefore based on the object, by saving process steps in the production of so-called. Unsupported catalysts (which consist entirely of catalytically active material) for the selective reduction of nitrogen oxides in

oxygen-containing exhaust gases in the presence of ammonia, a great simplification and thus to achieve a significant reduction in the cost of catalyst production. In addition to a direct and finely graduated control of

Catalyst properties are made possible by the process control. This object is essentially achieved by selecting certain titanium oxide materials and processing them in one Kneading process solved; It is possible to dispense with the already known measures for obtaining an intimate oxide mixture

become.

A catalyst for the selective reduction of nitrogen oxides with ammonia containing the components A) titanium oxide Bi) at least one oxide of tungsten, silicon, boron, aluminum, phosphorus, zirconium, barium, yttrium, lanthanum, cerium and B ₂ ) at least one oxide of vanadium, niobium, molybdenum, iron, copper

with an atomic ratio between the elements of components A) and B) of 1: 0.001 to 1 is obtainable according to the invention by reacting components A) in the form of a reactive high surface area titanium oxide having a BET surface area of 40-500, preferably 50-300, in particular 75-150 m ² / g, which is completely or predominantly in the anatase modification, together with the components B ₁ ) and B ₂ ), preferably their precursors, with the addition of the for pressing or

Extrusion of ceramic materials customary additives, humectants, proppants, binders, forming aids and

if necessary pore-forming agent, intensively kneaded into a homogeneous kneading mass, the kneaded mass extruded into shaped bodies, the

Molded body with slow increase in temperature up to 60 ⁰ C dries and then with gradual increase in Temperature in ambient air calcined in the range of 300-800 ⁰ C lying end temperatures. According to the invention as starting material for the components Bi) and B ₂ ) hydroxides, oxides, salts or Heteropolyacids or their salts, preferably ammonium salts used. Preferably, component A) and component B ₁ ) are mixed in the kneader and at pH 7-11, preferably 8-10 to a Residual moisture of 3-12, preferably 5-10Gew .-% dry kneaded before component B ₂ ) is added. Preferably, the dry pre-kneaded mixture of components A) and B ₁ ) at temperatures of 400-700 ° C.

precalcined before component B ₂ ) is added.

According to the invention from the components A), B ₁ ) and B ₂ ) existing mass at 300-800, preferably 400-700 ⁰ C.

precalcined before it is kneaded to a homogeneous clay.

The components B ₁ ) and B ₂ ) are in the form of a heteropolyacid or one of its salts, preferably the ammonium salts

used, wherein the present in the heteropolyacid metals from groups B ₁ ) and B ₂ ) in the atomic ratio of 12: 1 to 1: 12 are present.

Preferably, the starting material for component B ₂ ) is removed from the kneading process and is in the form of a salt

or a heteropolyacid or one of its salts, preferably the ammonium salts, in aqueous solution by impregnation on the consisting of the components A) and B ₁ ), preferably calcined catalyst precursor.

Suitable titanium oxides are reactive high surface area titanium oxides having a BET specific surface area of 40-500 m ² / g.

which are completely or predominantly anataseous. These materials can be by precipitation or by

Flame hydrolysis produced commercial products. The usually highly disperse products in addition to the

large specific surface area, a very narrow grain area with a mean order of magnitude of 30 nm.

The individual elements of group B) can be used, for example, in the form of the following starting compounds: Tungsten oxide, ammonium paratungstate or metatungstate, silica, silicotungstic acid, silicic acid, boric oxide, Boric acid, alumina, phosphorus oxide, ammonium phosphate, phosphotungstic acid, phosphomolybdic acid, Zirconium dioxide, zirconium phosphate, barium oxide, yttrium oxide, lanthanum oxide, cerium acetate, cerium nitrate, cerium oxide, borotungstic acid, Vanadium oxide, vanadyl oxalate, ammonium metavanadate, vanadotol-framic acids, vanadomlobanedioic acids, Vanadophosphormolybdic acids, phosphovanadic acid, niobium oxide hydrate, niobium oxalate, niobium vanadic acids, Ammonium molybdate, molybdenum oxide, iron oxide, iron phosphate, iron hydroxide, organic iron salts, such as iron oxalate, Copper acetate, copper dioxide, Cu, Ce, La containing heteropolyacids and the like. The substances mentioned can be used in the form of solutions or else as solid substances. In the production of the solid catalysts according to the invention, in addition to the actual catalyst mass, there are still a number

per se conventional additives needed.

As wetting agents can desalted water, aqueous ammonia solution, monoethanolamine and alcohols used

become.

As support materials z. B. glass fibers of different sizes use. As a binder, which of the paste to be produced after deformation in the state of the so-called. Green body sufficient stability

lend are cellulose derivatives, such as. As carboxymethylcellulose or unsubstituted celluloses suitable.

In addition, polyethylene, polypropylene, polyvinyl alcohol, polyethylene oxide, polyacrylamide or polystyrene come as Binders used.

To facilitate compression or to improve the extrusion ability, are deformation and / or sliding aids, such. As bentonites, clays, organic acids, paraffin, waxes, silicone oils added.

Finally, the porosity (pore volume, pore distribution) of the unsupported catalysts can also be adjusted in a targeted manner by adding suitable pore formers. Such substances are for. As finely divided coals or groundwood, which burn out at the calcination temperatures to be used.

For intensive kneading of the starting materials to a homogeneous plasticine kneading units are used. Kneaders with sigma or masticator blades are preferred. The inventive use of a specific titanium oxide in conjunction with an intensive kneading process for the preparation of the catalyst mass, bring significant advantages over the previously customary production process. This saves technically complex, environmentally damaging and therefore also expensive process steps. Co-precipitation milling operations for the preparation of an intimate oxide mixture omitted. This leads to a significant reduction in production and at the same time eliminates the dependence on elaborately prepared starting materials.

In addition, a targeted adjustment of the shrinkage, a crucial parameter for the cracking tendency and the breaking strength of solid catalysts, by the use of suitable starting materials and by adjusting the kneading process in terms of intensity, temperature and time including intermediate Temperschritte is possible (see ).

Furthermore, the new catalyst preparation process ensures a more direct and at the same time more flexible control of the catalyst properties by saving several process steps. Thus, the choice of a suitable stabilizer component from the series B ₁ ) improves the sintering resistance of the catalysts. This can be seen from the fact that the high BET surface area of the finished catalyst remains virtually constant in practical operation and that the temperature-induced phase transition of titanium dioxide from anatase to rutile modification is suppressed. These properties immediately result in significantly longer service lives of the catalysts obtainable according to the claims.

Figure 1 (for Example 13) illustrates the reduction of the activity declined during long-term use in flue gases from coal-dry-bottom with operating temperatures above 300 ⁰ C, if used in the catalyst as a stabilizer SiOj.

About the physico-chemical properties of the starting materials (TiO ₂ anatase, stabilizers from the series B ₁ ), activators from the series B ₂ ) as well as the choice of other additives and the inventive processing in the kneader, can be in a given plasticine by controlling empirical variation in the moisture content thereof during the kneading process, pore volume and pore radius distribution. The pore radius distribution can be varied within wide limits within the meso and macroporous range, wherein mono-, bi- and trimodal pore radius distributions as well as transitional forms between them are selectively adjustable. The right choice of these parameters leads to a significant increase in the catalytic! Activity. However, the pore distribution and the pore volume also have a decisive influence on the poisoning resistance and thus directly on the catalyst life.

In this context, the pK value of the solid surface is also given special weight. The pK value can be greatly changed in the catalyst according to the invention by selecting the stabilizers or activators. In particular, the use of heteropolyacids as activators and / or stabilizers should be mentioned here. Interestingly, it has been found that especially catalysts which are manufactured from these materials, when used in the problematic flue gases of hard coal Schmelzkammerfeuerungen z. B. compared to catalysts according to DE-PS 2458888 have a significantly lower tendency to accumulate arsenic and other impurities (catalyst poisons). This is due to the increased poisoning resistance due to reduced heavy metal adsorption on the catalyst surface. This makes it possible to use catalysts in the "high-dust operation" of hard coal-fired furnace furnaces with technically meaningful service lifes.The known comparative catalysts, on the other hand, are subject to rapid deactivation, which is primarily caused by heavy metals present in the flue gas.

Figure 2 and Figure 3 show the surprisingly large increase in activity of catalysts according to the invention in comparison to a catalyst conventionally prepared according to Comparative Example 1.

embodiment The invention will be explained in more detail with reference to embodiments. Catalyst testing has been reported in both dust-free model exhausts in a laboratory test facility and in exhaust gas

©! In addition, long-term tests were carried out in the flue gas of a hard coal-fired furnace.

The catalyst tests were carried out in the temperature range of 200-500 ⁰ C. The space velocities amounted thereby

between 10000 and 40000h ' ¹ . In each case it was found to be favorable molar ratio between the reducing agent

Ammonia and the nitric oxide of 0.6-1.6, preferably 0.8-1.2 applied. Comparative example

35kg of a prepared according to DE-PS 2458888 intimate mixture of oxides TiO ₂ and WO ₃ in a weight ratio of 9: 1 with 20 liters of deionized water, 6kg 15 wt.% Aqueous NH _r solution, 1.8 kg monoethanolamine and with a solution of ammonium metavanadate corresponding to 350g V ₂ Os. The mixture is kneaded intensively at varying moisture content and temperatures between 70 and 90 ⁰ C. Subsequently, 620 g of SiO ₂ , 1.4 kg of alkali-free clay and 3.5 kg of glass fibers (length 1-8 mm) are successively added. The mixture is kneaded for 6-8 hours to a homogeneous kneading material, wherein additionally 410g polyethylene oxide, 410g carboxymethylcellulose, 230g lactic acid and 11.5 kg of demineralized water are added to adjust the plasticity necessary for subsequent deformation.

With the aid of an extruder, the catalyst mass is then extruded into monolithic honeycomb bodies with channels of square cross section (cell division: 3.4 mm or 7.4 mm).

The moldings are dried in a climatic drying chamber with increasing temperature in the range of 20-60 ⁰ C and finally calcined after stepwise raising the temperature for 24 hours at 620 ° C.

Examples 1-9

The composition of the catalyst is shown in Table 1. Basically, the catalysts were prepared as follows:

35 kg of the mentioned in claim 1 TiO ₂ anatase with a BET surface area of 98 m ² / g are mixed with 4.4 kg of ammonium paratungstate (APW), 22 liters of deionized water, 7.5 kg 15Gew.% Aqueous NH ₃ - Solution, 1.8 kg monoethanolamine and with a solution of ammonium metavanadate corresponding to 390g V ₂ Os added. With intensive kneading in the temperature range of 60-90 ⁰ C further successively 670g SiO ₂ .2.5kg glass fibers (1-8mm length) and 1.5 kg alkali-free clay added. The mixture is kneaded for 5-7 hours to a homogeneous kneading (Werner & Pfleiderer kneader LUK 2.5), in addition to the adjustment of plasticity 450g polyethylene oxide, 450g carboxymethylcellulose, 250g lactic acid and 12.3 liters of deionized water are added. To fine tune the moisture content and the plasticity of the plasticine, it was necessary to add more ammonia water before the end of the kneading. With an extruder, the catalyst mass is then pressed into monolithic honeycomb bodies with channels of square cross section (cell division: 3.4 mm). After drying at an increasing temperature of 20-60 ° C in a climatic drying chamber, the moldings are calcined after stepwise raising the temperature for 24 hours at 620 ⁰ C.

In Examples 6-9 instead of TiO ₂ -Anatas or ammonium paratungstate (APW) or ammonium metavanadate (AMV) flame-hydrolytically produced TiO ₂ -P-25 (Degussa) or tungsten oxide, boron oxide or Nb ₂ O ₅ , the latter were used used as niobium oxalate dissolved in water.

Table 1

example Komp.A Comp. B ₁ A weight. Comp. B ₂ Proportion of B ₂ oxide in A oxide / B, oxide g / 100g AB ₁ - mixed oxide 1 anatase APW 9: 1 AMV 1.0 2 anatase APW 9.5: 0.5 AMV 1.0 3 anatase APW 9.9: 0.1 AMV 1.0 4 anatase APW 9: 1 AMV 0.5 5 anatase APW 9: 1 AMV 3.0 6 anatase WO ₃ 9: 1 AMV 1.0 7 P-25 WO ₃ 9: 1 AMV 1.0 8th anatase B ₂ O ₃ 9.7: 0.3 AMV 1.0 9 anatase APW 9: 1 Nb ₂ (C ₂ O ₄ I ₅ 2.5

Examples 10-13

35 kg of the mentioned in claim 1 TiO ₂ -Anatas with a BET surface area of 75m ² / g are added in the current kneader with 4.4 kg of ammonium paratungstate (APW) and 10kg 15Gew.% Aqueous NH ₃ solution. The suspension thus obtained is kneaded at 80 ⁰ C for 3 hours to dryness (residual moisture 5-10Gew .-%). Subsequently, the mixture thus obtained with 22 liters of deionized water, 75kg 15Gew.% Aqueous NH ₃ solution, 1.8 kg monoethanolamine and with a solution of ammonium metavanadate (AMV) corresponding to 390g V ₂ Os. This mass is further processed as described in Examples 1-9 and extruded into the same honeycomb bodies. The drying and calcination of the monoliths also takes place analogously to the method described in Examples 1-9.

In Example 11 according to Table 2, the ammonium metavanadate was replaced by ammonium molybdate (AM), in Examples 12 and 13 the ammonium paratungstate was replaced by BaO or SiO ₂ .

Table 2 Example Comp.A Comp. B ₁ Weight ratio. Comp. B ₂ fraction B ₂ oxide in A-oxide / B ₂ -oxide g / 100g AB ₁ -

mixed oxide

10 anatase APW 9: 1 AMV 1.0 11 anatase APW 9: 1 AT THE 3.0 12 anatase BaO 9.5: 0.5 AMV 1.0 13 anatase SiO ₂ 9: 1 AMV 1.0

Examples 14-17

35kg of the mentioned in claim 1 ТЮг-Anatas with a BET surface area of 40m ² / g are mixed with 4.0 kg of alumina and 12 kg of 15 wt .-% aqueous NH ₃ solution. The paste is dried to a residual moisture of between 5-10Gew .-% kneaded at ⁰ 80 C for 2-3 hours. Then the powder is pre-calcined at 400 C for 2 hours ^0th

The precalcined oxide mixture is mixed in a kneader with 22 liters of deionized water, 75 kg 15 wt .-% aqueous NH ₃ solution, 2.0 kg monoethanolamine, 210g pulp (coarse-fiber cellulose) and then only with a solution of ammonium metavanadate corresponding to 390g V ₂ O ₅ , Under intensive kneading at 60-90 ⁰ C 2.3kg alkali-free clay, 2.2 kg of glass fibers (length 1-8 mm), 200 g polyethylene oxide, 200g of carboxymethylcellulose and 250g of lactic acid are added in addition. The mixture is kneaded for 5-7 hours to a homogeneous kneading, wherein for adjusting the plasticity more ammonia water is added. With an extruder, the catalyst mass is finally pressed into honeycomb bodies with square-shaped channels (cell division: 7.4 mm). After drying with increasing temperatures (20-60 ⁰ C) in a climatic dry chamber, the moldings are calcined after stepwise increase in temperature for 24 hours at 700 ⁰ C. In Examples 15-17, instead of alumina according to Table 3, ammonium paratungstate or lanthanum oxide and, in Example 16, copper (II) acetate dissolved in water instead of ammonium metavanadate were added

Table 3

example Grain p. A KOmP-B ₁ A weight. Comp. B ₂ Proportion of B ₂ oxide in A oxide / BrOxid g / 100gA-B _r mixed oxide 14 anatase Al ₂ O ₃ 9: 1 AMV 1.0 15 anatase APW 9: 1 AMV 1.0 16 anatase APW 9.5: 0.5 Cu (CH ₃ COO) ₂ 1.5 17 anatase La ₂ O ₃ 9.5: 0.5 AMV 1.0

Examples 18-21

35 kg of the mentioned in claim 1 TiO ₂ -Anatas with a BET surface area of 28OmVg are mixed with 4.0 kg of zirconium oxide, 390 g of V ₂ O ₅ and 15kg 15Gew .-% aqueous NH ₃ solution. The low-viscosity paste is kneaded at 80 ° C for 2-4 hours to a residual moisture content of 5-10 wt .-%. The dry powder is then pre-calcined at 700 ⁰ C for 2 hours.

The precalcined mixture is mixed with 25 kg of demineralized water, 75 kg of 15 wt .-% NH ₃ solution and 2.0 kg of monoethanolamine and further processed analogously to Examples 1-9. The finished catalyst mass is extruded as in Examples 14-17 to form honeycomb bodies.

In Examples 19-21, according to Table 4, zirconia was replaced by ammonium paratungstate or phosphorus pentoxide, and in Example 20, V ₂ O ₅ by iron (III) oxide.

Table 4

example Komp.A Comp. B ₁ A weight. Comp. B ₂ Proportion B ₂ -OxJd in A oxide / BrOxid g / 100g AB ₁ - mixed oxide 18 anatase ZrO ₂ 9: 1 V ₂ O ₅ 1.0 19 anatase APW 9: 1 V ₂ O ₅ 1.0 20 anatase APW 9: 1 Fe ₂ O ₃ 1.0 21 anatase P ₂ O ₆ 9.5: 0.5 V ₂ O ₅ 1.0

Examples 22-26

35kg of the stated in claim 1 TiO ₂ -Anatas with a BET surface area of 98m ² / g are mixed with 422g ammonium 2-hydrogen-12-vanadophosphate and with 28 liters of deionized water.

The mass is kneaded intensively at a temperature of 40-70 ⁰ C, with the addition of 670 g SiO _2, 2.5 kg of glass fibers (length 1-8 mm) and 6.0 kg of alkali-free tone are added. To adjust the plasticity also 450g polyethylene oxide, 900g carboxymethylcellulose, 250g lactic acid and 15 liters of deionized water are added.

The mixture is kneaded for 5-7 hours to a homogeneous clay and processed into honeycomb bodies according to Examples 1-9.

According to Table 5, in Examples 23-26, the ammonium 2-hydrogen-12-vanadophosphate was replaced by the following heteropolyacids:

Table 5

example Comp. A KOiTIp-B ₁ + B ₂ A weight. A oxide / Bi oxide 22 anatase (NH ₄ J ₆ H ₂ [P (V ₁₂ O ₃₈ ) J 9.99: 0.01 23 anatase (NH ₄ J ₈ IV ₆ WeO ₃₇ ] 9.9: 0.1 24 anatase H ₄ [P (Mo ₁₁ VO ₄₀ )] 9.99: 0.01 25 anatase H ₆ [P (Mo ₉ V ₃ O ₄₀ )] 9.99: 0.01 26 anatase (NH ₄ JeH [P (Mo ₁₁ CuO ₄₀ )] 9.99: 0.01

Examples 27-31

35 kg of the mentioned in claim 1 TiO ₂ -Anatas with a BET surface area of 98m ² / g with 4.3 kg of ammonium paratungstate, 22 liters of deionized water, 7.5 kg of 15 wt .-% aqueous NH ₃ solution and 1 , 8 kg monoethanolamine added. The mass is provided according to Examples 1-9 with additives (plasticizer, support materials, etc.), intensively kneaded (2-7 hours at 60-90 ⁰ C) and extruded into honeycomb bodies, which are considered here as a catalyst precursor. The latter are dried and calcined analogously to Examples 1-9 and after cooling (according to Claim 7) with 1.0 g of vanadium pentoxide per 100 g of titanium dioxide / tungsten oxide mixture by impregnation with a solution of ammonium ^ -hydrogen-vanadophosphate in one of the water absorption capacity the honeycomb body applied a corresponding amount of water. Drying is carried out under air flow at 150 ⁰ C. The final annealing is carried out for 2 hours at 400 ° C. In Examples 28-31, instead of ammonium paratungstate or ammonium 2-hydrogen-i 2-vanadophosphate, ammonium metatungstate, yttrium oxide, zirconium oxide or silicon dioxide or V ₂ Os (as aqueous solutions of vanadium oxalate), corresponding to the proportions shown in Table 6, were ammonium 6-wolframato-6-vanadate or 11-molybdo-1-vanadophosphoric acid.

Table 6

example Grain p. A Comp. B ₁ A weight. Comp. B ₂ Proportion B ₂ -OxId A oxide / B ^ oxide in g / 100 g AB ₁ - mixed oxide 27 anatase APW 9: 1 (NH ₄ JsH ₂ [P (V ₁₂ O ₃₆ )] 1.0 28 anatase AMW 9: 1 V ₂ (C ₂ O ₄ ) S 1.0 29 anatase Y ₂ O ₃ 9.8: 0.2 V ₂ (C ₂ O ₄ ) _S 1.0 30 anatase ZrO ₂ 9: 1 (NH ₄ J ₈ [V ₆ W ₆ O ₃₇ ] 1.0 31 anatase SiO ₂ 9: 1 H ₄ [P (Mo ₁₁ VO ₄₀ )] 1.0

Testing of the produced catalysts

The catalysts prepared according to Examples 1-31 were tested in the flue gas of an oil furnace, which was adjusted by adding additional pollutant components (NO _x and SO ₂ ) and ammonia required for nitrogen oxide reduction according to the test conditions given below.

test conditions : NO _K 800 ppm exhaust gas composition NH ₃ 800 ppm SO ₂ 500 ppm O ₂ 5,0Vol .-% H ₂ O 11,0Vol .-% CO ₂ 12,0Vol .-% N ₂ rest

The catalyst tests were carried out in the temperature range 250-500 ° C and at a space velocity of 20,000 h '. Selected results of the measurements and long-term tests in coal-fired dry fires under the conditions already mentioned are shown in the graphics FIGS. 1, 2 and 3. The underlying measurements are summarized in Tables 7 and 8.

Table 7 ·

Example 1 6 10 13 14 18 23 27 Comparative

No sample

250 46.0 43.8 39.5 40.5 45.2 44.2 42.5 45.8 34.5

500

* The values given are NO _K conversion rates (η _Ν ο _Μ ) in% relative to the ΝΟ ,, initial concentration. Table 8 *

63.1 60.1 57.5 58.5 62.7 60.5 67.5 62.7 52.0 75.7 72.2 69.4 71.1 73.5 72.5 70.7 74.9 63.9 86.0 84.1 81.3 82.6 84.0 83.0 81.1 85.4 74.7 93.4 90.6 87.0 88.2 91.5 89.9 87.5 92.7 81.8 94.3 92.3 87.8 89.0 92.4 91.1 88.4 94.0 83.1 90.4 86.6 80.8 81.5 87.5 86.6 83.3 88.5 76.0

SK-TF (T = 450 ^° C)

t [h] Examples Comparison sample

1 6

zero measurement 95 92 89 83 500 91.5 86 84.5 75.5 1000 89.5 85 84 73.5 2000 88 85 83.5 73 3000 88 84.5 83.5 72.5 4000 87.5 84.5 83.5 71.5

* The values given are ΝΟ ,, - Revenues (Лмо.і in%, based on the ΝΟ, initial concentration.

Claims (7)

1. Catalyst for the selective reduction of nitrogen oxides with ammonia, containing the components A) titanium oxide B ₁ ) at least one oxide of tungsten, silicon, boron, aluminum, phosphorus, zirconium, barium, yttrium, lanthanum, cerium and B ₂ ) at least one oxide of vanadium, niobium, molybdenum, iron, copper, with an atomic ratio between the elements of components A) and B) of 1: 0.001 to 1, preferably 1: 0.002 to 0.4, characterized in that it is obtainable by reacting component a) in the form of a reactive high-surface area titanium oxide having a BET surface area of 40-500, preferably 50-300, in particular 75-15OmVg, which is completely or predominantly in the anatase modification, together with the Components B ₁ ) and B ₂ ), preferably their precursors, with the addition of the usual for a compression or extrusion of ceramic materials additives wetting agent, propellant, binder, forming aid and optionally pore-forming agent, kneaded intensively to form a homogeneous clay, extruding the clay to form moldings, the moldings with slow increase in temperature until at most 60 ⁰ C dries and then with gradual increase in the temperature in Ambient air calcined at lying in the range of 300-800 ⁰ C end temperatures. 2. Catalyst according to claim 1, characterized in that it is obtainable by using as starting material for the components B ₁ ) and B ₂ ) hydroxides, oxides, salts or heteropolyacids or their salts, preferably ammonium salts. 3. A catalyst according to claim 1 or 2, characterized in that it is obtainable by mixing the component a) and the component B ₁ ) in the kneader and at pH 7-11, preferably 8-10 to a residual moisture content of 3-12, preferably 5-10 wt .-% dry kneaded before component B ₂ ) is added. 4. A catalyst according to claim 3, characterized in that it is obtainable by pre-calcining the dry pre-kneaded mixture of components A) and B ₁ ) at temperatures of 400-700 ⁰ C, before the component B ₂ ) is added. 5. Catalyst according to claims 1 to 3, characterized in that it is obtainable by the from the components A), B ₁ ) and B ₂ ) existing mass at 300-800, preferably 400-700 ⁰ C is precalcined before this is kneaded to a homogeneous plasticine. 6. A catalyst according to claims 1 to 5, characterized in that it is obtainable by the components B ₁ ) and B ₂ ) are used in the form of a heteropolyacid or one of its salts, preferably the ammonium salts, wherein the present in the heteropolyacid Metals from groups B ₁ ) and B ₂ ) in the atomic ratio of 12: 1 to 1:12 are present. 7. A catalyst according to claim 1 or 2, characterized in that it is obtainable by the starting material for the component B ₂ ) deprived of the kneading process and in the form of a salt or a heteropolyacid or one of its salts, preferably the ammonium salts, in aqueous solution is applied by impregnation to the preferably calcined catalyst precursor consisting of components A) and B ₁ ).