Catalyst for removing nitrogen oxide and process for producing the catalyst

(42) Date of commencement of the patent: 15. 1. 1996 (45) Date of issue: 26. 8.1996

<td>(30) Priority:</td><td>(73) Patent owner:</td>

<td>4. 7.1986 JP 61-157448. 9.10.1986 JP 61-240894 claimed. 14.11.1986 JP 61-271533 claims.</td><td>BABCOCK-HITACHI KABUSHIKI KAISHA TOKYO (JP).</td>

<td>(56) Documents:</td><td></td>

<td>US 4046888A US 4663300A EP 219854A2 US 4332644A EP 186398A2</td><td></td>

(54) CATALYST (57) It describes a catalyst for the removal of nitrogen oxides, its loss of activity by volatile catalyst poisons, which are contained in exhaust gases, is avoided and having an increased lifetime, and a method for producing the catalyst, wherein the catalyst is titanium dioxide having a surface area of ​​20 m 2 / g or less and a zeolite coated with 0.01 to 20% by weight of copper and having an average pore diameter of 1 nm or less and a molar silica / alumina ratio of 10 or there is more and wherein the method consists of mixing the zeolite powder with the titania or its precursor, followed by molding the mixture into a predetermined shape, followed by annealing the material obtained at 800 ° C or more.

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The invention relates to a catalyst for the removal of nitrogen oxides according to the preamble of claim 1.

The nitrogen oxides contained in the exhaust gases of various incinerators are not only harmful to the human organism as such, but also cause air pollution such as photochemical smog. For removing or denitrating such nitrogen oxides, a catalytic reduction method with ammonia (selective reduction) is widely used. As a catalyst for this, a number of catalysts have been invented, among which practically those of titanium dioxide with an addition of vanadium (V), molybdenum (Mo), tungsten (W) and the like are mainly used. They are described, for example, in Japanese Patent Applications Sho 50-51966 / 1975 and Sho 52-122293 / 1977. These catalysts have advantages because the reduction of activity by sulfur oxides, etc. only small. However, they have a drawback because the resistance to poisoning by volatile catalyst poisons such as As, Se, Te, etc. is so low that results in a significant reduction in activity.

On the other hand, in recent years, coal and crude oil from China have been used, which have a high content of mineral substances and thereby cause a higher proportion of the above-mentioned metals in the exhaust gases. Now, if the above catalysts are used to denitrate such exhaust gases, there is a problem of greatly reducing their activity.

U.S. Patent No. 4,663,300 has disclosed a method of reducing the nitrogen oxide content by catalytic reduction. In this, a catalyst is used which is made of a crystalline aluminosilicate, (2) a substance prepared by exchanging an alkali metal ion in a crystalline aluminosilicate with at least one metal cation and having a nitrogen oxide reducing activity, and (3) a supported catalyst is formed. The latter is made by applying an active metal component having the ability to reduce nitrogen oxides from a carrier prepared by removing an alkali metal ion from a crystalline aluminosilicate by impregnation treatment.

The crystalline aluminosilicates used according to US Pat. No. 4,663,300 are those having a pore diameter in the range of about 0.3 nm to 1.5 nm and have an SiO 2 / AbOa molar ratio of about 2 to 6.

The known catalyst has in its crystalline aluminosilicates an active content of active metal of about 1 to 20% by weight of copper and about 1 to 30% by weight of a refractory substance containing titanium dioxide.

In this known catalyst, however, due to the large surface of the titanium dioxide only insufficient denitration and high abrasion losses of the catalyst.

Furthermore, EP-A2-186 398 and US Pat. No. 4,331,644 disclosed zeolite catalysts which have high SiO 2 / Al 2 O 3 molar ratios and CU cations. However, such catalysts are relatively sensitive to catalyst poisons and have only erring abrasion resistance.

The aim of the invention is to propose a catalyst of the type mentioned, which is largely insensitive to catalyst poisons and which is characterized by a high abrasion resistance.

This is achieved by the characterizing features of claim 1 according to the invention.

The proposed measures result in a catalyst which is characterized by the low surface area of ​​the titanium dioxide by high activity for a long time and a high abrasion resistance, as well as a high degree of insensitivity to catalyst poisons.

Due to the features of claim 2 results in a further increase in the abrasion resistance of the catalyst.

Another object of the invention is to propose a process for the preparation of a catalyst according to the invention, which ensures a high quality of the catalysts.

This is achieved by the features of claim 3.

Due to the features of claims 4 and 5 results in very simple process control.

Due to the features of claim 6 and 7, a reduction in the surface of the titanium dioxide is achieved in a simple manner.

The invention will now be explained in more detail with reference to the drawing. Showing:

FIG. 1 Fig. 12 shows a typical view of the surface of a catalyst obtained by applying to a molded support substance by impregnation of methyl silicate or ethyl silicate obtained by mixing a zeolite having an active component coated thereon with titanium dioxide. FIG. 2 Fig. 10 is a graph indicating the relationship between the abrasion loss with respect to the amount of S1O2 and the percentage of the removed nitrogen oxides in the catalyst of the present invention.

When aluminum sulfate, alkyl silicate, inorganic fibers or the like is contained in the above-mentioned catalyst of the present invention, it is possible to further improve the mechanical properties

AT 401 356 Β to improve. In particular, in the impregnation of the catalyst body with alkyl silicates both the mechanical properties and the activity of the catalyst can be improved.

The copper applied to the zeolite is for the most part contained in the pores (micropores) of the catalyst in which active sites are formed. Since the diameter of the pores is so small that the above-mentioned catalyst poisons can not penetrate, these active sites are not directly poisoned. In addition, when titanium dioxide is mixed with the zeolite, the mechanical strength of the catalyst is improved. However, since the titanium dioxide itself has catalytic activity and new active sites are formed by migration of a portion of the copper from the pores of the zeolite to the titanium dioxide, the deposition of the volatile catalyst poisons on the surface of the catalyst increases, thereby clogging the pores of the zeolite and thus the activity is reduced. However, if according to the invention a titanium dioxide is used which has a smaller surface than the customary titanium dioxide, or if the catalyst is impregnated with alkyl silicates and then annealed, the deposition of catalyst poisons is largely suppressed and the clogging of the pores of the zeolite by the deposition of large quantities of Catalyst poisons on the catalyst prevented.

The denitration catalyst of the present invention is prepared by mixing a specific zeolite onto the copper as the active metal beforehand by any conventional method such as impregnation, Replace, Knead, Etc, was applied, with titanium dioxide in a ratio of preferably 1: 9 to 9: 1, followed by a dry molding process of the mixture, such as compression molding, a roll granulation process, adding water to the mixture followed by kneading the mixture to obtain a pasty material, which is then extruded in the form of a tube or rod, or a process of applying this pasty material to a metal plate, a metal net, a ceramic fabric or the like. The application of the copper to the catalyst according to the above conventional method can also be carried out after the catalyst body is molded. The resulting shaped catalyst is calcined and can then be used as a catalyst in practice. When the above molded catalyst is impregnated in an amount of 1 to 20% by weight with an alkyl silicate such as methyl silicate or ethyl silicate and then annealed, the resulting catalyst has a higher resistance to the volatile catalyst poisons and increased mechanical strength, since the alkyl silicate in The macropores of the catalyst penetrates and the particles are joined together, whereby the surface is reduced.

In the present invention, zeolites having a molar ratio of SiO 2 / Al 2 O 3 of 10 and above, preferably 20 and above, have an average pore diameter of 1 nm and below, preferably 0.8 nm and below. Examples thereof are mordenite, ZSM-5 (trade name of a synthetic zeolite manufactured by Mobile Oil Company Ltd.), ferrierite, etc. When the molar ratio of SiO 2 / Al₂O3 is less than 10, the mechanical strength and abrasion resistance of the obtained catalyst are lower. When the average pore diameter is larger than 1 nm, sufficient resistance to catalyst poisons is not obtained.

For applying copper as the active ingredient, various methods such as replacement, kneading, impregnation, etc. may be used. using various kinds of copper salts such as copper sulfate, copper nitrate, copper acetate, etc. An amount of coated copper of 0.01 to 20% by weight is suitable, and an amount within the cation exchange capacity of the zeolite is preferred. As the active ingredient in addition to copper, at least one of the metals iron (Fe), vanadium (V), molybdenum (Mo) or tungsten (W) may be applied.

The mixing ratio of the zeolite to the titanium dioxide is preferably in the range of 1/9 to 9/1 based on the ratio of zeolite / titanium. If this ratio is too small, the resistance to the catalyst poisons is too low, if it is too large, there is no appreciable improvement in mechanical strength. The ratio zeolite / titanium dioxide is therefore preferably in the range 3/7 to 8/2.

The titanium dioxide used in the invention has a surface of 20 m²/ g or below, preferably 10 m²/ g or below. Such titania can be prepared by oxidation of titanium tetrachloride obtained by a chlorination process such as reaction of an ilmenite or rutile with chlorine and coke or by annealing a precursor of titania such as titanic acid obtained by hydrolysis of titanium salts at a temperature of 800 °. C or above, preferably 900'C or above. Such a titanic acid may also be formed into a catalyst body and annealed thereon. Examples of such titanium salts are titanium tetrachloride, titanium sulfate, ammonium titanate, etc. Even if the surface of titanium dioxide is more than 20 m²/ g, the catalyst according to the invention can be prepared if the catalyst is impregnated after shaping with an alkyl silicate, in particular methysilicate or ethyl silicate, and then annealed thereon.

When the catalyst body mainly composed of the zeolite having an active ingredient thereon and titanium dioxide is impregnated with an alkyl silicate, the alkyl silicate decomposes

AT 401 356 Β

SiO 2, etc., thus improving the strength of the catalyst. At the same time, the hydroxyl group of titanium dioxide (TiO₂) selectively with the alkyl silicate to form a silanol bond and SiO 2 as shown in Figure 1, thus increasing the strength of the catalyst. On the other hand, in the zeolite with the active sites, no SiO₂ etc is formed in such amounts, the higher activity is maintained. In addition, the SiO 2 partially coated on the zeolite has₂ etc., the effect of reducing the pores of the zeolite, whereby volatile catalyst poisons such as arsenic, etc from exhaust gases difficult to penetrate into these pores and destroy the catalyst.

Preferably, inorganic fibers are added to or mixed with the catalyst powder or catalyst paste prior to molding, thereby appreciably increasing the mechanical properties of the resulting molded catalyst product. As inorganic fibers, those having a decomposition temperature of 500 ° C. and above, such as glass wool, kaowool (trade name for alumina / silica ceramics), asbestos, etc. be used. The mixing ratio is preferably in the range of 1 to 30% by weight, preferably 5 to 20% by weight, based on the total weight of the catalyst.

The inner pore surface of the zeolite is much larger than its outer surface. Therefore, zeolite-applied copper is mainly present within the pores where the active sites for denitration are formed. Since the diameter of these pores is so small that the above-mentioned volatile catalyst poisons can not penetrate, they act as a molecular sieve and prevent direct poisoning of active sites by the catalyst poisons. In addition, since the outer surface of the zeolite (excluding the micropores) is small, catalyst poisons are difficult to attach. With the simultaneous presence of titanium dioxide, however, new active sites are formed in addition to the active sites of titanium dioxide itself. As a result, part of the copper, which forms active sites in the pores of the zeolite, migrates to the titanium dioxide. Not only are these active sites poisoned directly by the volatile catalyst poisons, but they also promote the accumulation of catalyst poisons on the catalyst.

By using a titanium dioxide with a surface of 20 m²/ g or below for the catalyst of the invention, it is possible to minimize the amount of copper migrating from the zeolite pores onto the titanium dioxide and the amount of catalyst poisons accumulated on the catalyst, thereby reducing the loss of activity of the catalyst.

Moreover, if the molded, consisting of zeolite and titanium dioxide catalyst body is impregnated with aluminum sulfate or an alkyl silicate, followed by drying and annealing, so the particles in the catalyst are crosslinked and bonded together, whereby the mechanical strength is increased and at the same time the surface is reduced, because macropores on the catalyst are destroyed; the volatile catalyst poisons are therefore harder to hold on the catalyst and thus the loss of activity is more effectively prevented.

The present invention will be further described by way of examples.

The surface area of ​​the catalyst in the examples was measured as follows:

A catalyst (about 0.2 g) adjusted to a particle size of 10 to 20 mesh was placed in a sample cell and freed from air with heating to 160 ° C. After removing the air, the weight of the sample was determined, and the cell was connected to a BET surface measuring apparatus (Autosorb 1, trade name of one of Yuasa Ionics Co., Ltd.). manufactured apparatus). The catalyst sample was then cooled with liquid nitrogen and the amount of nitrogen adsorbed at low pressure on the catalyst was measured several times by a constant pressure method and the surface area (m²/ g) calculated according to the BET adsorption formula.

example 1

An aqueous solution (1.7 L) of copper acetate (Cu (CH 3 COO)₂) (Cu concentration 2.1 g / l) was added to a hydrogen type synthetic mordenite (1.2 kg) having a ratio SiO 2₂/ AI₂O3 of 23 and an average pore diameter of 0.7 nm were added and the mixture was stirred to deposit the copper by substitution on the mordenite, followed by drying of the resulting material at 180 ° C. followed by annealing at 500 ° C. for two hours. To 500 g of powder of this Cu-coated mordenite was added 10 g of methyl cellulose as molding assistant, and 500 g of titanium dioxide prepared by the chlorination method (specific surface area: 20 m²/ g or below). After mixing, further, kaowool (150 g) as an inorganic filler and water were added to the mixture, the mixture was kneaded with a kneader for 2 hours to obtain a paste, the paste was dried at 18 ° C., then calcined at 500 ° C. and calcined annealed annealed material to a powder of 10 to 20 mesh to obtain a catalyst.

AT 401 356 Β

Example 2

The paste obtained in Example 1 was roll-rolled under pressure onto a wire mesh panel made of SUS 304 stainless steel in the form of a metal mesh sprayed with liquid aluminum, and then dried at room temperature for 8 hours, followed by annealing at 500 ° C. for 2 hours to obtain a plate-type catalyst.

Example 3

The catalyst obtained in Example 2 was immersed in an aqueous solution of aluminum sulfate at a concentration of 350 g / l for 15 minutes, and the resulting material was dried at room temperature for 8 hours, followed by annealing at 500 ° C. for 2 hours to obtain a catalyst receive.

Example 4

A catalyst was obtained in the same manner as in Example 3, except that the aqueous solution of aluminum sulfate (concentration 350 g / L) was replaced by ethyl silicate.

Example 5

Example 2 was repeated except that 700 g of powdery Cu-coated mordenite and 300 g of titanium dioxide were mixed to obtain a plate-shaped catalyst.

Examples 6 and 7

The catalyst obtained in Example 5 was impregnated with aluminum sulfate or ethyl silicate as well as Examples 3 and 4 to obtain catalysts.

Example 8

Example 2 was repeated except that a mordenite with a ratio of SiO₂/ AI₂O3 of 32 used to obtain a catalyst.

Example 9

The catalyst obtained in Example 8 was impregnated with aluminum sulfate in the same manner as in Example 3 to obtain a catalyst.

Example 10

Example 2 was repeated except that the mordenite ZSM-5 (trade name of a synthetic zeolite, manufactured by Mobil Oil Company Ltd., SiO 2 / Ai₂O3 ratio = 47) is used to obtain a catalyst.

Example 11

The catalyst obtained in Example 10 was impregnated with ethyl silicate in the same manner as in Example 4 to obtain a catalyst.

Example 12

Example 2 was repeated, except that titanium dioxide was a titanium dioxide prepared by washing a 30% by weight aqueous slurry of metatitanic acid with water, filtering,

Drying at 180 * C for 4 hours, annealing the material obtained at 900'C for 5 hours and

Grinding the annealed material (surface of the titanium dioxide 5.8 m²/ g, average particle size 2.53 μm) to obtain a catalyst.

ΑΤ 401 356 Β

Example 13

Example 12 was repeated, except that the annealing was replaced at 900 ° C. by annealing at 830 ° C. (the resulting titanium dioxide had a surface area of ​​19.6 m²/ g and an average particle size of 1.85 μm) to obtain a catalyst.

Comparative Example 1

Example 1 was repeated except that titania was prepared as the titanium dioxide prepared by neutralizing a 30% by weight aqueous slurry of metatitanic acid with ammonia water, washing the neutralized substance with water, filtering and drying at 180 ° C. for 4 hours, to get a catalyst.

Comparative Example 2

Example 2 was repeated except that a powder prepared by washing a 30 wt.% Aqueous slurry of metatitanic acid with water, filtering the washed material and drying at 180 ° C. for 4 hours to obtain a catalyst was used as the titanium dioxide receive.

Comparative Example 3

The catalyst obtained in Comparative Example 2 was impregnated with aluminum sulfate in the same manner as in Example 3 to obtain a catalyst.

Comparative Example 4

Example 2 was repeated except that the dried powder of the ammonia-treated titanium slurry obtained in Comparative Example 1 was used as the titanium dioxide to obtain a catalyst.

Comparative Example 5

Example 2 was repeated, except that the copper-coated mordenite was used in an amount of 1 kg and no titania was used to obtain a catalyst.

Comparative Example 6

Example 2 was repeated except that the ratio of the copper-coated mordenite / titanium dioxide was 0.5 / 0.95, that is, 50 g of copper-coated mordenite and 950 g of titanium dioxide were used to obtain a catalyst.

Comparative Example 7

Example 12 was repeated except that the annealing at 900 ° C. was replaced by annealing at 600 ° C. (the resulting titanium dioxide had a surface area of ​​54.1 m²/ g, an average particle size of 1.20 μm and a content of sulfate groups of 2.8% by weight) to obtain a catalyst.

Experimental Example 1

With the catalysts set forth in the Examples and Comparative Examples, their denitrification capability was determined before and after the adsorption of AS2O3. The conditions for the adsorption test with AS2O3 and for the measurement of the denitration capability are shown below.

(1) Conditions for adsorption test:

AT 401 356 B

<td>Composition of the gas:</td><td>NO NH₃50₂50₃AS2O3 CO₂H2O O2</td><td>200 ppm 240 ppm 500 ppm 50 ppm 10 ppm 12% 12% 3%</td>

Reaction temperature: 350 ° C

Surface speed: 51 m / h (space velocity in the case of granulated catalysts) Adsorption time: 2 hours for granulated catalysts; 6 hours for plate-shaped catalysts.

(2) Conditions for measurement of adsorption capacity:

<td>Composition of the gas:</td><td>NO NH₃SO2 CO2 H₂O O₂n₂</td><td>200 ppm 240 ppm 500 ppm 12% 12% 3% rest</td>

Reaction temperature: 350 · C Area velocity: 51 m / h

Experimental Example 2

Using the catalysts of Examples 2 to 11 and Comparative Examples 2 to 6, grit (MGH-70, trade name of a product manufactured by Hohwa Kogyo Company) (8 kg) from a height of 50 mm was coated on the respective plate type catalysts 100 x 100 mm and dropped at a 45 ° inclination under constant temperature and humidity conditions to measure the abrasion loss (g).

Table 1 shows the results for initial activity, activity after the AS2O3 adsorption test and the abrasion test of the individual catalysts.

From the results of Table 1 it can be seen that that the catalysts with titanium dioxide prepared by the chlorination method (Examples 1 to 11) and titanium dioxide produced by the high temperature annealing method (Examples 12 and 13) are not very different in their initial characteristics from those with high surface area titania (Comparative Examples 1 to 7); however, the reduction in activity after the AS2O3 adsorption test is much lower for the former than for the latter. It also shows that the lower the surface area of ​​the titanium dioxide, the greater the mentioned effectiveness, but this efficiency is about 50 m²/ g no longer pronounced (Comparative Example 7) and is noticeably above about 20 m²/G. Further, catalysts containing titanium dioxide, which has a lower content of sulfate groups, apparently have a lower reduction of the activity after the AS2O3 adsorption test than those catalysts with a titanium dioxide with a high content of sulfate groups (Comparative Examples 4 and 2). In addition, it has been found that impregnation with aluminum sulfate, etc. can effectively prevent the reduction of the activity of the catalyst.

In terms of mechanical strength, it is further found that the low surface area titania catalysts have sufficient strength, and that their strength is markedly increased when impregnated with aluminum sulfate or the like. Large surface area titanium dioxide catalysts are not initially as robust and the effectiveness of impregnation with aluminum sulfate or the like is low (Comparative Examples 1-4). However, this can be improved by impregnating the shaped catalyst body with alkyl silicates such as methyl silicate or ethyl silicate followed by annealing as shown in Examples 14 to 20 below.

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<td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td></td><td></td><td></td><td>fl</td><td></td><td>fl</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>fl</td><td></td><td></td><td></td><td></td>

<td></td><td></td><td>1</td><td>u</td><td>S</td><td>44</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>c</td><td>4 »</td><td></td><td></td><td></td><td></td>

<td>e</td><td>fl</td><td>"</td><td>1 0</td><td>fl</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>fl</td><td>44 2</td><td>2</td><td>2</td><td>2</td><td>2</td>

<td>u</td><td>V</td><td></td><td>&gt; 44</td><td>u</td><td>fl</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>X</td><td>fl</td><td></td><td></td><td></td><td></td>

<td>O</td><td></td><td>fl</td><td>~ c</td><td>σ</td><td>fR</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>σ</td><td>fR</td><td></td><td></td><td></td><td></td>

<td>cb</td><td></td><td></td><td>CD</td><td></td><td>O.</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>X</td><td></td><td></td><td></td><td></td>

<td colspan="2"></td><td>u fl u fl fR</td><td>s fl X Ü</td><td>1 fl</td><td>u fl a 6</td><td colspan="8">35</td><td>53</td><td>85</td><td>© t *</td><td>20</td><td>76</td><td>c *</td><td>20</td>

<td></td><td></td><td></td><td>fR</td><td>u</td><td>«3</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td></td><td></td><td>44</td><td>• R</td><td>3</td><td>fl '• m-'</td><td>Ο</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>CM</td><td>fR</td><td>©</td><td>CM</td><td>O</td><td>©</td><td>^ 4</td>

<td>G</td><td></td><td>• R</td><td>fl</td><td>Ό</td><td>e</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>fl</td><td>05</td><td>e</td><td>H</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>44</td><td>* 3</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>&lt;M</td><td>• f4</td><td></td><td></td><td></td><td>c</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>3</td><td>X</td><td></td><td></td><td></td><td>fl</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>X</td><td>0</td><td></td><td></td><td>6</td><td>α</td><td>fR</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>eo</td><td>©</td><td>• "T</td><td></td><td></td><td>O"</td><td></td>

<td>AROUND</td><td>• * 4</td><td>fl</td><td></td><td>in the</td><td>ο "****</td><td>Ο</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>O</td><td>©</td><td>CM</td><td>CM</td><td>CM</td><td>CM</td><td>©</td>

<td>K fl</td><td>* 0</td><td>X</td><td>c</td><td>FR</td><td>3 Μ</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>S TS</td><td colspan="2">Ci «1</td><td>fl</td><td>3</td><td>X r</td><td>Ο</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>©</td><td>©</td><td>©</td><td>t</td><td>©</td><td>©</td><td>CM</td>

<td>fl</td><td>fl</td><td>σ</td><td></td><td>CO</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td></td><td>44</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>• M</td><td>• R</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>w</td><td>fr-</td><td>l</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td></td><td></td><td>u</td><td>•</td><td>fco</td><td></td><td>c *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>©</td><td>©</td><td>C *</td><td>CO</td><td>t *</td><td>c *</td><td></td>

<td></td><td></td><td>"</td><td>f4</td><td>\</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td></td><td></td><td></td><td></td><td>dt</td><td></td><td>ο</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>©</td><td>©</td><td>FR</td><td>eo</td><td>fR |</td><td>* ·</td><td></td>

<td></td><td></td><td>©</td><td></td><td>e</td><td></td><td>^ R</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>FR</td><td>©</td><td>CM</td><td>05</td><td>©</td><td>©</td>

<td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>CM</td><td>eo</td><td>CM</td><td>CM</td><td></td>

<td>xa</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>-&gt; α</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>&lt;R Lf</td><td>•</td><td></td><td>Γ5</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>r- X</td><td>X</td><td>OJ</td><td>O</td><td></td><td></td><td>eo s</td><td>2</td><td>2</td><td>s</td><td>2</td><td>s</td><td>CM 2</td><td>e * · s</td><td>eo</td><td>2</td><td>2</td><td>2 2</td><td>2 2</td><td>2</td><td>2</td>

<td>O</td><td>u</td><td>O</td><td>IN</td><td></td><td></td><td>CM</td><td></td><td></td><td></td><td></td><td></td><td>CO</td><td></td><td>CM</td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>fl 0</td><td>fl</td><td>• W</td><td>^ R</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>CM s</td><td>&gt;</td><td>CO</td><td>&lt;</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

CMeO5T © CDt * ©©© '-' CMCO

CM ^ »© © C *

O.

a eo &lt;x te eo

Examples 14 and 15

Mordenite powder (SiO 2 / Al 2 O 3 = 25, average pore diameter 0.7 nm) coated with 3% by weight of Cu and annealed at 500 ° C. for 2 hours was mixed with titanium dioxide powder in a weight ratio of 1: 1. Then, water was added to the mixture to obtain a pasty material, which was then applied to a stainless steel mesh (SUS 304) sprayed with liquid aluminum in an oxidizing atmosphere. The obtained material was annealed at 500 ° C. for 2 hours to obtain a plate-type catalyst. This catalyst was immersed in liquid methyl or ethyl silicate for one minute, then air-dried and calcined at 500 ° C. for 2 hours to obtain a catalyst.

AT 401 356 B

Examples 16 and 17

Example 14 was repeated except that a mixture of ethyl silicate with anhydrous ethanol in a weight ratio of 2/1 or 1/2 was used to obtain a catalyst.

Example 18

The catalyst impregnated with ethyl silicate and dried from Example 15 was again impregnated with ethyl silicate, dried in air and then annealed at 500 * C for 2 hours to obtain a catalyst.

Example 19

The ethyl silicate-impregnated catalyst of Example 15 was allowed to stand at 30 ° C. and a relative humidity of 95%, then dried and calcined at 500 ° C. for 2 hours to obtain a catalyst.

Example 20

A plate-type catalyst annealed at 500 ° C. for 2 hours from Example 14 was subjected to moisture absorption at 30 ° C. and a relative humidity of 95% for 30 minutes, then impregnated with ethyl silicate, dried in air and calcined at 500 ° C. for 2 hours. to get a catalyst.

The catalysts obtained in Examples 14 to 20 were tested in the same manner as those in Experimental Examples 1 and 2. The results are summarized in Table 2. As can be seen from Table 2, the catalysts of the present invention have significantly lower attrition loss as compared to the catalysts of Comparative Examples, but at the same time retain high activity. Thus, it can be seen that the present invention is a superior method of improving the abrasion resistance of a catalyst.

For the catalysts of Examples 14 to 18, the relationship between the SiO applied to the catalyst₂, the attrition loss and the percent removal of nitrogen oxides in Table 2. As can be seen from Table 2, the impregnation is preferably carried out so that the amount of SiO 2 applied to the catalyst₂ 3 to 20 wt .-% is.

Table 2

<td>catalyst</td><td>Impregnating substance</td><td>Impregnated amount% by weight</td><td>Abrasion loss g</td><td>Percentage denitration%</td>

<td>Beisp.14</td><td>methyl silicate</td><td>15.3</td><td>0.18</td><td>70.2</td>

<td>15</td><td>ethyl silicate</td><td>12.2</td><td>0.20</td><td>71.5</td>

<td>16</td><td>n</td><td>8.3</td><td>0.25</td><td>73.4</td>

<td>17</td><td>"</td><td>4.9</td><td>0.36</td><td>74.6</td>

<td>18</td><td>rt</td><td>20.5</td><td>0.14</td><td>65.7</td>

<td>19</td><td>n</td><td>12.4</td><td>0.16</td><td>71.6</td>

<td>20</td><td>"</td><td>7.7</td><td>0.18</td><td>72.7</td>

<td>Comp. Catal.</td><td>-</td><td>-</td><td>3.38</td><td>77.1</td>

According to the present invention, it is possible to obtain a catalyst for denitrating exhaust gases whose loss of activity caused by volatile catalyst poisons in the exhaust gases is very small, which loss would be unavoidable with conventional catalysts, and which also has sufficient mechanical strength and has superior abrasion resistance. It is thus possible to use the catalyst according to the invention in particular for a long time as a catalyst for the removal of nitrogen oxides from exhaust gases of the coal combustion, which contain a high proportion of dust and catalyst poisons.

AT 401 356 Β