JPS6245340A - Catalyst for reducing content of nitrogen oxide in combustion exhaust gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Summary of the Invention 1 A silicate having a three-layer structure (three-layer silicate) containing at least one of the metals Ti, Zr, V, W, Mo, or Ce as one or more of its oxides. ), the catalyst comprises: (a) an acid-activated three-layer silicate in which the three-layer silicate still partially maintains its crystalline layer structure; (b) trilayer silicate or ≧30 mVa I before activation;
/100 (+ cation exchange capacity, (C) The concentration of intermediate layer cations has decreased based on acid activation, and the BET surface area is equal to the BET surface area of the three-layer silicate before activation. (d) acid activity [the atomic ratio between the silicon contained in the biochemical trilayer silicate and the metal contained in the oxide is 0.2] ~5
0. It is preferably 0.4 to 25.

[Industrial Application Field] The present invention relates to a catalyst that reduces the nitrogen oxide content of combustion exhaust gas.

[Prior Art] When combusting chemical compound 5 fuel, nitrogen oxides (NOX) are formed from nitrogen-containing components as well as air nitrogen and reach the atmosphere, causing serious environmental pollution.

Nitrogen oxides can be converted to N2 and H20 by NH3, and this reaction is quite selective over a wide temperature range, i.e. in the presence of a large excess of oxygen, such as is generally present in flue gas. It is known that the process proceeds with almost no loss of ammonia by oxidation and therefore only relatively small amounts of reducing agent are required. In general, various catalysts are already known for NOx reduction using ammonia.

For example, from German Publication No. 2410175@, the stoichiometric ratio of vanadium, molybdenum and/or tungsten V12, -yMOxW, (where X and y are O
This type of catalyst is known, which is made of an oxide where ≦X<8.0<y≦5 and 0.3≦(X+V)<8.

Furthermore, a method for reductive decomposition of nitrogen oxides in exhaust gas is known from German Patent No. 2458 aag@, in which a gas mixture containing nitrogen oxides, molecular oxygen and ammonia is brought into contact with a catalyst composition. , this catalyst composition contains the essential components (A>titanium as oxide in an intimate mixture with (B) iron or vanadium as monide.

These catalysts have the disadvantage that the relatively expensive transition metal compounds they contain as catalytically active components are utilized to only a small extent due to their non-optimal distribution. The active component can also be spread on an inert solid support, which clearly improves its economic efficiency, but the risk arises that the catalytic activity is significantly reduced upon dilution with inert substances. These catalysts convert the SO2 often contained in the flue gas into SO3
They also have the disadvantage that they can oxidize, resulting in, for example, salt deposits in subsequent equipment.

Furthermore, a catalyst is known from DE 34 38 367 which reduces the nitrogen oxide content of the combustion exhaust gas by selective reduction, which catalyst can be obtained in particular by heat treatment of (A) aqueous oxidized compounds of titanium or silicon. and (B) [
0 to 5% by weight of a catalyst oxide containing vanadium monide;
(C) For example, it is composed of 1 to 15% of a catalytic oxide of tungsten.

What is essential for this type of catalyst is that S i 02 and TiO
2 and 4A? A solid acid is formed and the acid i1
It may be modified by treatment with sulfuric acid or ammonium sulfate. This partitioning of fixed acid appears to be crucial in controlling NH3 adsorption onto the catalyst surface and therefore appears to be essential for improving catalyst activity.

In this case, Si02 is used as a silicic acid sol.

As is well known, 3i02 sol gives rise to silicic acid gels, which are characterized by their high BET surface area and at the same time a high degree of porosity, but a low macroporous fraction and, as a result, a low effect on mass transfer, and therefore a low catalytic effect. I am also poor.

Furthermore, a catalyst material is known from DE 27 48 471 for use in the gas phase reduction of nitrogen oxides with ammonia, in particular for reducing the nitrogen oxide content of the flue gas, which catalyst substantially Metallic copper, vanadium, chromium, molybdenum, tungsten, mankan, iron or cerium oxides or sulfates with an average particle size of 0.1 to 100! It is supported on a molded carrier containing titanium oxide and clay minerals. Clay minerals of the type montmorillonite, kaolin, halloysite, pyrophyllite and sericite can be used. In the case of these clay minerals, aluminosilicates with a layered structure are present, and in some cases trilayered silicates are present. Even with the pre-use of up to 15% by weight of these clay minerals,
The strength of the catalyst increases only slightly. Regarding the catalytic effect, these additives in the amounts mentioned play no role. If the amount is larger than that, it may even have a negative effect in this regard, and it may even lead to SOX
Decreases the resistance of the catalyst to the contained exhaust gases.

This time, the use of a three-layered silicate modified in a specified manner will further bring about a synergistic exchange effect with the oxidation catalyst component, improve the activity, and reduce the nitrogen oxide content of the combustion exhaust gas using a particularly expensive oxidation catalyst. It has been found that an economical use of the components and the reducing agent provides a catalyst of the type mentioned which is sufficiently removable. It has also been found that a higher degree of SOX resistance can be obtained.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to
A catalyst capable of reducing the nitrogen oxide content of combustion exhaust gas containing i, Zr, V, WSMo or Ce as one or more oxides thereof in combination with a three-layer silicate (three-layer silicate). It is to provide.

[Means for solving the problem] According to the invention, the catalyst has the following characteristics: (a)
A trilayer silicate is an acid-activated trilayer silicate that still partially maintains its crystalline layered structure; (b) the trilayer silicate is ≧30 mVal before acid activation;
/ioog, (C) the concentration of interlayer cations is reduced based on acid activation, and the BET surface area is at least as large as the BET surface area of the trilayer silicate before acid activation. 15%, preferably at least 50%, and (d) the atomic ratio between the metal contained in the silicon tooxide contained in the 1 mm activation layer silicate is from 0.2 to
50, preferably 0.4-25.

The term "acid activation" of trilayer silicates refers to treatment resulting from the exchange of hydrogen ions for monovalent or divalent cations in the interlayer.

In other words, it was confirmed that if a three-layer silicate that only causes this type of ion exchange is used, a catalyst with sufficiently high activity cannot be obtained. Furthermore, catalysts obtained using natural trilayer silicates of type 1'' do not exhibit sufficiently high activity and are not resistant to SOX. Similarly, natural or alkali-activated trilayer silicates (alkali metals are catalytic poisons for the catalysts in question here), as well as fuller earths and natural acid clays, such as Japanese Niigata clay, are also unsatisfactory.

Acid activation probably erodes the silicate layer from its edges and causes ions to elute from the hemiphase. The remaining S i 04-helical phase leads to a change in the orientation of the layer due to simulative effects and steric hindrance, especially during drying. However, in this case 1. The layered structure of the crystal is not substantially destroyed. An intermediate state is reached between the crystal structure of the three-layer silicate, which exists from the beginning or already exists as type 1, and the sufficiently destroyed crystal grooves of amorphous silicic acid.

Acid activation generally increases the specific surface area measured by the BET method. The high specific surface area obtained is also obtained after intimate mixing of the acid-activated layered silicate with the oxidizing components of the catalyst, even when these components are used in large amounts. On the other hand, as mentioned above, acid activation must not proceed to the extent that only amorphous silicic acid remains. This is because in this case it is clear that there is no longer an exchange effect on the oxidizing components of the catalyst, and a significant decrease in the catalytic activity is observed as the silicic acid content increases.

Yet another important feature of the catalyst according to the invention is the use of a trilayer silicate with a cation exchange capacity of ≧30 mVa I/100 g before acid activation. The reason why especially highly active catalysts are obtained using starting materials of this kind is not yet clear in detail, but it appears to be based on the particularly advantageous crystal structure of the acid-activated trilayer silicates.

Acid-activated trilayer silicates exhibit synergistic exchange behavior with metal silicates. However, to date, no clear explanation of the mechanism for this exchange effect has been provided, but the existence of a silicate layer structure that has been reoriented through acid activation seems to be an essential premise.

Thus, if, for example, a silicic acid gel with an equivalent BET surface area is used instead of the acid-activated trilayer silicate according to the invention for reaction with the oxidized metal component, a clear reduction in the catalytic activity occurs.

The acid-activated trilayer silicate used in the present invention preferably has a specific surface area of about 80 to 400 m2/! ;I range.

In the case of the catalyst according to the invention, the concentration of interlayer cations (in particular Na, MCI and Ca) upon acid activation is as follows:
It is preferably at least 12% lower than the agricultural yield.

During acid activation, cations are first removed from the intermediate layer. Further acid activation also removes cations, especially aluminum and iron, from the lattice sites. This results in a change in the silicate structure.

The silicate layer is attacked by the acid from its edges. This probably leads to a change in the orientation of the trilayer silicate by the imitation of a SiO4-tetrahedron, whereby the oxidation catalyst component can clearly produce an exchange effect on the acid-activated trilayer silicate.

Acid dissolution is generally carried out until the SiO2 content of the acid-activated trilayer silicate is increased by at least 5%, preferably at least 10%, over the starting material. Depending on the starting materials, the S i 02 content is between 50 and 90% by weight, preferably between 65 and 80% by weight. In this case, acid dissolution is not performed until only S i 02 of the X-ray amorphous remains. until a predetermined crystallinity of the acid-activated trilayer silicate exists.
That is, acid dissolution is interrupted when a proportion of extractable silicates of less than 45% is present. The proportion of extractable silicates is determined by treating the washed and dried filter cake obtained after carrying out the dissolution with a soda solution [Y
, Otsuho, Journal of the Chemical Society of Japan, Vol. 72 (1951), p. 573.1 Preferably, the proportion of pore volume corresponding to macropores with a diameter of >8011 m is preferably at least 25%. In this case, the pore volume is determined by mercury pomametry.

The acid activation of the starting material containing the trilayer silicate can be carried out in a manner known per se, preferably using an aqueous inorganic acid such as, for example, hydrochloric acid or sulfuric acid. However, organic acids such as formic acid and acetic acid can also be used.

The acid concentration ranges from 1 to 60% by weight, preferably from 10 to 40% by weight, based on the dry matter content. Preliminary wet sorting of the raw materials has also proven advantageous. The acid-treated material is washed and filtered with acidified water if necessary.

The catalyst according to the invention is furthermore characterized by a high degree of resistance to sulfur oxides or sulfuric acid. This is three-layer silica 1
This is due to acid activation. Catalysts made with untreated ion-exchanged or alkali-activated trilayer silicates are subject to severe attack by sulfur oxides or sulfuric acid, resulting in mechanical failure and premature catalyst deterioration. This is probably due to the presence of a relatively large amount of alkali, which acts as a catalyst poison.

On the other hand, catalysts prepared using amorphous silicic acid are resistant to sulfur oxides and sulfuric acid, or their NOx activity is clearly poor.

Preferably acid-activated trilayer silicates of the smectite type, especially of the montmorillonite type, are used.

The most important montmorillonite-containing natural mineral is bentonite, which can exist as calcium or sodium bentonite. Other minerals of the smectite type are hectorite and nontronite.

Starting compounds for the metal oxide component of the catalyst according to the invention include, on the one hand, the corresponding metal oxides and, on the other hand, substances convertible into metal oxides, such as metals, hydroxides and in particular salts, complex compounds and/or hydroxides. Acids or salts derived from these acids are used. these are,
If necessary, it can be used together with reducing agent J3 and/or additive 1) which acts as a complex forming agent.

For example, Ce203, CeO2, Ce
It is possible to use starting from (SO4)2 and Ce2 (C204)3. Suitable starting materials for zircon oxide are, in addition to oxide hydrates, eg zircon salts, zirconyl salts, eg Zr (SO4)2.7 rG4.7 r 0
Ci2 and Zr (C204)2.

Examples of starting materials for the tungsten component include tungsten oxide (for example, WO3, W+o○29, W4011
, WO2), mono- and poly-tungstic acids, heteropolyacids, tungstates, tungsten halides and tungsten oxyhalides. Corresponding molybdenum compounds can also be used in place of these tungsten compounds. For vanadium, especially 205,02, V203 cl, -J: and VO are iM
Starting compounds include ortho- and poly-vanadate or vanadate salts, vanadium halides and vanadium oxyhalides (e.g. VOQ!3).
), 'Kum salt or vanadyl salt of various types are also suitable.

Suitable titanium compounds are, in addition to oxides and oxide hydrates, titanium or titanyl salts, especially halides and l salts. Preferably, chikunyl sulfate is used.

Metal-organic compounds can also be used, such as esters of titanic acid, such as isopropyl titanate.

Metal oxides individually in the following concentration ranges: T i 02 = 10-80 wt% WO3 and/or MoO2 = 1-25 wt% V2
It has been found that particularly advantageous results are obtained if the acid-activated trilayer silicate accounts for the remainder of the active ingredient.

In the case of suitable catalysts, the metal oxides are present as ternary or ternary combinations.

In a preferred ternary combination, the metal oxides are in the following proportions: (a) (TiO2+\/205) = 1 o-go wt% (b) (T i02 + WO3 and /' or Mo53) = 10-80 wt% % (C) (T i 02 +CeO2> =10-8
0 wt% (d) (WO3 and/or Mo03 +V
205 ) = 2-25% by weight (e) (CeO2 + V2O5) = 1-25% by weight
(f) (Zro2+V205) = 1-25
% by weight, with the acid-activated trilayer silicate accounting for the remainder of the active ingredient.

The weight ratios between the metal oxides in the binary combination preferably each include the following ranges: (a) V205 /T i02 = 0.001-
0.2(b) WO3 and/or MOO3/T i
02= 0.1-0.25 (c) CeO2/T i 02 = 0.1-0.3
(d) V205 /W○3 and/or MoQ3=
0.1- 2.5 (e) V205 /CeO2= 0.1- 1.0(
f) V205 / Zr02 = 0.1-1.0° In the case of a ternary combination, the metal oxide is in the following preferred amount ratio: (a) (TiO2+ ~ VO3 and/or MOOa + V205) = 10-80i amount % (b) (T i 02 + CeO2 + V205 )
=10-a.

Weight% (c) (T i 02 + ZrO2 + V205 )
=10-80% (d) (WO3 and/or MOO3+CeO2+V
205) Catfish 10-25% by weight (e) (WO3 and/or MOO3+ZrO2+V
205 > = 10-25% by weight, with the acid-activated trilayer silicate accounting for the remainder of the active ingredient, respectively.

The weight ratios between the metal oxides in the ternary combination preferably each include the following ranges: (a) WO3a and/or MOO3/T i 02=
0.01 - 0.25 V205 /T i 02' = 0.01 - 0.1
1(b) CeO2/T i 02 = 0.05-
0.23V205 /T i○2 = 0.01-
0.11(C)ZrO2/TiO2=0.01
- 0.24V205 /T i○2 = 0.01
- 0.11 (+J) CeO2/WO3 and/or MOO3 = 0.1- 5.0 V2O3/WO3 and/or MOO3 = 0.1
- 2.5 (e) V205 /WO3 and/or MOO3=
0.1- 2゜5 Zro2/WO3 and/or MOO3= 0.1
-100 The catalyst according to the invention is obtained, for example, by impregnating an acid-activated three-layer silicate with a solution containing one or more of the above-mentioned metals as salts and/or complex compounds, followed by calcination.

According to another variant, the catalyst is prepared by mechanically mixing the acid-activated trilayer silite with one or more oxides or salts of the metals mentioned above (e.g. by milling in a ball mill) and then using this mixture as required. It is obtained by impregnating with a solution containing one or more of the above-mentioned metals as salts and/or complex compounds, and then firing.

In general, the catalyst according to the invention comprises precipitating or reprecipitating at least one compound containing one or more of the metals mentioned above in the presence of an acid-activated trilayer silicate;
It can also be obtained by washing away foreign ions and then firing.

Precipitation or reprecipitation of compounds containing one or more of the metals mentioned above is carried out in the presence of a mixed suspension of acid-activated trilayer silicates and oxides or salts of one or more of the metals mentioned above. You can also do that. After washing and removing foreign ions, it is fired again.

In this way, nearly optimal intimate mixing of the oxidized metal component and the acid-activated trilayer silicate is achieved.

When the oxidized metal component is made of a metal oxide with a W number,
Each starting compound can be precipitated together or sequentially in several steps; the order of the precipitation steps generally influences the catalyst activity and must be optimized in each individual case.

Of course, it is also reasonable to impregnate the trilayer silicate with a solution of the corresponding transition metal compound, if necessary after one or more precipitation steps. In this case, the impregnation may be carried out either before or after the shaping d5 and calcination of the catalyst.

The catalyst according to the invention can also contain inert support substances. Generally, the catalyst is present as a shaped body;
In particular, spheres, tablets, extrudates, elongated or squamous honeycombs (also called "channel lattices"), rods,
Exists as a tube, ring, wheel or saddle.

These molded bodies can be obtained, for example, by tabletting or extrusion pressing the catalyst material, and additives for improving moldability can be mixed therein as required. Additives of this type are, for example, graphite or aluminum stearate.

Furthermore, additives that improve the surface structure can also be mixed. In this case, examples include materials that burn while leaving a pore structure during subsequent firing.

The use of additives to improve moldability is not absolutely necessary. This is because the trilayer silicate used as starting material has plastic formability even if it is present during intimate mixing with the metal component. However, it is also possible to add neutral bentonite or other binders, such as kaolin or cement. Shaping is generally carried out with the addition of water or organic solvents, such as -hydric or polyhydric alcohols.

The catalyst according to the invention is generally dried after shaping and is preferably dried from about 200 to γOO°C, preferably from 300 to 55°C.
It is fired at a temperature of 0°C. Additionally, inorganic fiber materials can be added before molding to increase strength. Calcination activates the catalyst and achieves its favorable properties, especially when obtained in the specified temperature ranges mentioned above.

Typical operating procedures for preparing catalysts according to the invention are described in the Examples below.

The present invention provides, in general, a catalyst according to the invention using NH3 as a reducing agent in order to reduce and avoid reducing the nitrogen oxide content of the flue gas, which besides common exhaust gas components also contains sulfur oxides (SOX). It also relates to use.

In the case of reduction with NH3, the nitrogen oxide content of the flue gas is reduced by forming N2 and N20.

Nitrogen oxides (NOx) include various oxygen compounds of nitrogen, such as No, N203, NO2, N2
05, but mainly NO and NO2, especially No, are important.

The NOX concentration of the exhaust gas to be purified can vary over a wide range and generally ranges from 100 ppm by volume to 5% by volume. The molar ratio of NH3:NOx is generally 0.3 to 3,
It is preferably between 0.6 and 1.5 and can be set by means of control technology in such a way that maximum NOx conversion is obtained with the lowest possible N1-13 consumption. NH3 can be administered either in gaseous form or as an aqueous solution.

The catalyst according to the invention is characterized by a highly selective conversion of ammonia, which makes it suitable for use in the reduction of nitrogen oxides compared to known catalysts. In the known process, particularly at high operating temperatures, a significant portion of the ammonia is not consumed for the desired NOx removal, but is oxidized by the oxygen present in the exhaust gas. This results in additional nitrogen formation or lowers the NOx conversion observed between the reactor inlet and outlet, as well as unnecessary NH3 consumption.

For denitrification reactions, reactors used for heterogeneously catalyzed gas phase reactions are generally suitable in principle, as long as the structural characteristics of the reactor as a whole are suitable for throughputs corresponding to high flue gas volumes. There is. The allowable space-time velocity (RG) is the catalyst 112
gas at 500 to 20,000 per hour, preferably 10
00 to 15000j of gas, the space-time velocity is calculated for gas at O'C and 1 bar. below,
Space-time velocity is shown with a dimension of 11-1 for simplicity.

Suitable reaction temperatures are about 200-600°C, preferably 250-600°C. ! It is in the range of 30°C. At significantly higher temperatures, oxidation of ammonia by the oxygen present in the exhaust gas occurs, whereby the ammonia undergoes a reaction with nitrogen oxides, resulting in a lower degree of denitrification.

However, this undesirable effect is not as great with the catalysts of the invention as with the known catalysts.

[Examples] Typical examples for the production and use of catalysts according to the present invention will now be described.

In particular, the effectiveness of a catalyst with respect to the removal of nitrogen oxides from a mixture (a gas which also contains oxygen and sulfur oxides) is determined by contacting the catalyst with a gas stream, in which the gas stream contains the catalyst in bulk. The tube was passed through an external electrically heated tube. The gas mixture used has the following composition: 02 3% by volume H2O 10% by volume NO 750 volume Room NO250 volume i ppm N1-t3 800 volume ippm SO2 950 volume ffil)l) m SO350 @ amount ppm N2 balance to 100% by volume.

The concentrations of components No and NO2 in the gas mixture were measured continuously by a certified analyzer before and after passing through the catalyst bulk layer (chemiluminescence method). As a measure of the effectiveness of the catalyst with respect to the reduction of nitrogen oxides, the conversion of the components No and NO2 after reaching the resting state is used and is defined by the following formula: No conversion (UNo) E xloo (%) CN .

NO2 conversion rate (U) NO2 = xloo (%) NO2 where the symbols CNO and CNO2 indicate the concentration of No and N02, and the superscripts E and A indicate the state of the gas mixture before and after passing through the catalyst.

Example 1 <a) Average particle size of 50 particles obtained by water beneficiation in raw suspension and cation exchange capacity of 79 mVal/Ilg and BET surface area of 69 Trt/(] 2 kg of crude bentonite fraction with the chemical composition shown was mixed with 8 f! of 1-(C1 aqueous solution).
The mixture was stirred for 6 hours. The HO content was approximately 21% by weight on dry ring material. It was filtered with suction and the filter cake was thoroughly washed with acidified water (pH adjusted to 5 with HG). The resulting acid-activated bentonite (hereinafter referred to as
SAB) is dried at 200 °C and then heated to 21 °C.
It had a BET surface area of 0 TrL/g. Its chemical composition is also shown in the table. From this, the reduction in the concentration of interlayer cations was calculated to be 75%.

(b) A suspension of S A B 320 (+) obtained in step (a) in water 5e with a T i 030 of 160 ()
4 was immersed while stirring, and neutralized by adding 1/2 concentrated ammonia. The solids were filtered aspirated, washed free of salt and extruded as extrudates with a diameter of 3+nm after addition of 1(7) glycerol. These were heated at 450°C.
The molding, drying and calcination were carried out in the same manner as for the catalyst material according to the following example.

The composition of the catalyst, the reaction temperature and the No- or NO2 conversion rate at a space-time velocity of 5000 h-1 are shown in Table 2. The above gas mixture was used to carry out the reaction, and the No- and NO2- conversions were calculated according to the above formulas.

Examples 2 and 3 A similar procedure was followed as in Example 1, except that 640C1 (Example 2) or isoog Ti08O
4 (Example 3) was used.

Example 4 400 g of SAB (step a of Example 1) and 350 m of water
Ammonium tungstate 106 in 1! The mixture with ;1 solution was thoroughly kneaded.

Example 5 32 g of N to a solution of oxalic acid dihydrate 52 () in 3507 water
Add 32 g of 84V○3 little by little and mix thoroughly with 475 g of SAB (Step a of Example 1).

Example 6 SAB in water 512 (Step a of Example 1) 400
180 g of Ti0sOa was immersed in the c+(7) suspension with stirring and neutralized with 1/2 concentrated ammonia.

This was suction filtered, washed until sulfuric acid was removed, and 1/
2a condensed ammonia 3 (tengestic acid in m 10.
Mix intimately with the solution of ag.

Example 7 The procedure was as in Example 6, except that the starting materials were: 250 g of SAB and 450 g of T i 03O4 and 27
．． 0g tungstic acid.

Example 8 Catalysts were prepared according to the working procedure of Example 6 from: SAB of 100 () and Ti of 7209 0304 and 4
3.2 CI tungstic acid.

Example 9 196g of Ti0sO4 in 5 parts of water! SA340 inside
It was immersed in 0 g of suspension with stirring. This was neutralized with ammonia, washed until sulfuric acid disappeared, and 4.2g
of oxalic acid dihydrate, 2.6 g of N84V○3 and 50 ml of water were mixed thoroughly.

Example 10 The procedure of Example 9 was repeated with the following changes.
i.e. 250g SAB and 490g TiO304
and 10.2i) of oxalic acid dihydrate and 6.40 of NH4VO3
and was used.

Example 11 SAB of i oog and 784 instead of the amount of substance in Example 9
g of Ti0s04 and 18.3 g of oxalic acid dihydrate and 10.2
g of NHaVO3 was used.

Example 12 46 g of oxalic acid dihydrate were dissolved in 350 d of water, to which 25.6 l of NH4VO3 were added in portions.

After addition of 84.6 g of ammonium tungstate, 100 g of SAB was soaked and the resulting material was kneaded.

Example 13 450g of SAB was mixed with 25.6g of oxalic acid dihydrate and 16(
l of NH4VO3 and water from 200 (d) of the solution obtained in 86.6 () of basic ceritum nitrate to water 170
Used with the solution obtained in m1 and mixed intimately.

Example 14 Oxalic acid dihydrate 25.6 (J and NH
4VO216g (D solution, 130.5g (DZr
(NO3)4 450g SA after addition of 5H20
Mixed with B.

Examples 15-23 Catalysts according to Examples 15-23 were prepared in a similar manner,
The amounts used in each case are shown in the table below.

A suspension of SAB (step a of Example 1) in 5 liters of water was
The i08O4 was soaked in with stirring, neutralized with ammonia and filtered with suction. The solid was washed until free of sulfuric acid, dried at 120°C for 15 hours, and obtained by reaction with 8 liquids of ammonia-alkaline tungstic acid, ammonium metavanadate, and 1.6-fold excess of oxalic acid dihydrate. The solution was then kneaded. The amount of solvent was chosen to give a paste material that could be easily kneaded.

Real SAB Titani Tanges Metavanazine
Example of ammonia acid (g
) (g) (g) Mu (9) 15 400 180 9.7
1,316 400 160 19.4
2.817 400? 80 5.4
6.418 250 450 24.
3 3.219 250 400 48
．． 6 B, 420 250 450
13.5 16.021 100 720
38.9 5.122 100 640
77.8 10.223 100 7
20 21.6 25.6> The proportion having a pore volume measured by HCI pomametry corresponding to a macropore with a diameter of 801 m was 67.6% for the catalyst according to Example 18. Similar values were obtained for other catalysts.

Example 24 400q of SAB was added to 75.6 (7 parts of tungstic acid, 3 parts of tungstic acid)
The resulting material was dried at 120°C for 15 hours and calcined at 500°C for 3 hours. Next, add 1 part of this to water.
Ce(○H)(NO3)3 ・3H204 in 75m1
A solution of 6, 2 () and 20.5 g of oxalic acid dihydrate and 12
．． Equal volumes of solutions obtained from 8 (J) and N84VO3 were added sequentially.

Example 25 A catalyst was prepared in the same manner as in Example 24, but zirconium nitrate pentahydrate of 69.6 (] was used instead of basic cerium nitrate.

Examples 26-28 Catalysts of Examples 26-28 were made as follows: 5
T i 0304 to AB-Suspension (Step a of Example 1)
was added with constant stirring and neutralized with ammonia. The solid, which has been suction filtered and washed until free of sulfuric acid, is
The mixture was thoroughly mixed with 400 d of a solution prepared by adding basic cerium nitrate to a solution obtained from NH4VO3 and oxalic acid dihydrate (1:1.6>).

The amounts of starting components used are shown in the table below.

Actual SAB Titanium Basic Nitric Acid NH4-Meta
sulfuric acid cerium water vanadate, e.g. (c
+) (g) Japanese product (CI> (ni 1) 26
'400 184 13.9 2.62
7 250 460 34.7 6.42
8 100 736 55,,! ) 1
0.2 Catalyst materials according to Examples 29-31 to Examples 26-31
It was prepared in the same manner as shown in 28. However, instead of basic cerium nitrate, zirconium nitrate hydrate (Example 29
Example 30: 52.2 g; Example 31: 83.5 g) and the other ingredients in the amounts indicated, in this case Examples 26 and 29, Example 27
and 30 and Examples 28 and 31 correspond, respectively.

Table ■ Example Composition (%) 1 T
iO2 (20), SAB (80)2 TiO2
(50>, SAB (50)3 TiO2 (80)
, SAB (20>4 WO3(20>, SAB (
80)5 V205 (5), SAB (95
)6 WO3(2>, TiO2(18), 5AB(
80)7 WO3(5), TiO2(45), SA
B (50)8 WO3 (8), TiO2 (72)
, SAB (20) No. ■ Table 9 V2O5 (0,4), Ti02 (19,6), 5A
B (8010V205 (1), 'T-i02 (49)
, 5AB(50)11 V2O5(1,6), Ti02
(78,'4), 5AB(2012V2O5(4), W
O3 (16), 5AB (80) 13 V2O5 (2,5
>, CeO2(7,5), 5AB(90)14 V2O
5(2,5>, Zr02(7,5), 5AB(90)1
5 V2O5(0,2>, WO3(1,8>, Ti02
(18) (Continued) 〉 Table ■Example Composition
(%)16 V2O5(0,4>, WO3(3,6
), TiO2(16)17 V2O5(1), WO3
(1), TiO2 (18), 5AB18 V2O5 (0
,5> , WO3(4,5> , TiO2(45)19
V2O5 (1), WO3 (9), TiO2 (40)
, 5AB20 V2O5(2,5), WO3(2,
5), TiO2(45)21 V2O5(0,8>,
WO3(7,2), TiO2(72)22 V2O5
(1,6>, WO3('14.4>, TiO2(64(
Continued) T (°C) UNo (%) UNo2 (%) No.
Table Example Composition
(%) 30 V2O5 (1), ZrO2 (3), T
iO2 (46), 5AB (31V205 (1,6>
, ZrO2 (4,8>, TiO2 (73,6SAB = acid activated bentonite (continued) V7 Amorphous silicic acid 50
0.54.545 94 95
92V8
80 0.2 The catalyst according to Example 18 was further compared with known catalysts for NO reduction with respect to the use of the reducing agent ammonia.

The known catalyst contained only oxidation catalyst components without acid-reacted bentonite in the following composition: V2O5 1.0% typesetting WO39.0% Shigesato TiO290.0% by weight.

This catalyst was used together with the inventive catalyst according to Example 18 for 5000 h in each case using a gas mixture corresponding to the above composition.
The test was conducted at a space-time velocity of -1. The percentage of ammonia added to the reactor that was actually consumed for NOx reduction was determined from the converted reactant balance. This rate is shown in FIG. 2 as a function of reaction temperature.

In the case of the comparative catalyst, a significant portion of the ammonia was oxidized by the oxygen present in the exhaust gas and could therefore no longer be used for the desired No removal.

In contrast, the catalyst according to the invention exhibited much less undesired oxidation of ammonia by oxygen.

1.818 26 43 47[
Effects of the Invention] According to the present invention, the acid-activated three-layer silicate has sufficiently high activity, and the nitrogen oxide content in the combustion exhaust gas can be more effectively reduced without loss of ammonia used as a reducing agent. A catalyst is obtained that reduces the

[Brief explanation of the drawing]

Figure 1 is a characteristic curve diagram showing the relationship between silicate content and No conversion rate in various catalysts, and Figure 2 is a characteristic curve diagram showing the relationship between the proportion of ammonia consumed in NOx reduction and reaction temperature. be. Patent Applicant Jute-Hiemi Akchengesellschaft Silicate [Contains 1 angular amount (''/,) → NH3-Best J!L Fig, 2

Claims (16)

[Claims] (1) Combustion exhaust gas containing at least one metal Ti, Zr, V, W, Mo or Ce as one or more of its oxides in combination with a silicate having a three-layer structure (three-layer silicate). In a catalyst for reducing nitrogen oxide content, (a) the trilayer silicate is an acid-activated trilayer silicate that still partially maintains its crystalline layer structure, and (b) the trilayer silicate is an acid-activated trilayer silicate. Before ≧30mVal/
(c) the concentration of interlayer cations is reduced due to acid activation, and the BET surface area is at least 15% relative to the BET surface area of the trilayer silicate before acid activation. %, preferably at least 50%; (d) the atomic ratio between the silicon contained in the acid-activated trilayer silicate and the metal contained in the oxide is between 0.2 and 50;
, preferably from 0.4 to 25. A catalyst for reducing the nitrogen oxide content of combustion exhaust gas. (2) The concentration of interlayer cations is reduced by at least 12% by acid activation relative to the concentration of interlayer cations in the three-layer silicate before acid activation. Catalyst according to item 1. (3) The SiO_2 content of the acid-activated trilayer silicate is increased by at least 5%, preferably by at least 10%, relative to the starting material. catalyst. (4) Catalyst according to any one of claims 1 to 3, characterized in that the proportion of the pore volume corresponding to macropores with a diameter of >80 nm is at least 25%. (5) The metal oxides individually have the following concentration ranges: TiO_2 = 10-80 wt% WO_3 and/or MoO_3 = 1-25 wt% V
_2O_5 = 0.1-25% by weight CeO_2 = 1-25% by weight, and the acid-activated three-layer silicate accounts for the remainder of the active ingredient. The catalyst described in Crab. (6) The following binary combinations of metal oxides: (a) (TiO_2 + V_2O_5) = 10-80% by weight (b) (TiO_2 + WO_3 and/or MoO
_3) 10-80% by weight (c) (TiO_2+CeO_2) = 10-80% by weight
(d) (WO_3 and/or MoO_3+V_2O
_5) = 2-25 weight% (e) (CeO_2+V_2O_5) = 1-25 weight%
(f) (ZrO_2+V_2O_5)=1-25% by weight
7. The catalyst according to claim 1, wherein the acid-activated three-layer silicate accounts for the remainder of the active ingredients. (7) The weight ratio between the metal oxides of the binary combination is within the following range: (a) V_2O_5/TiO_2=0.001-0.2
(b) WO_3 and/or MoO_3/TiO_2
=0.1-0.25 (c) CeO_2/TiO_2=0.1-0.3(d)
V_2O_5/WO_3 and/or MoO_3=0
．． 1-2.50 (e) V_2O_5/CeO_2=0.1-1.0(f
) V_2O_5/ZrO_2=0.1-1.0. (8) The following ternary combinations of metal oxides: (a) (TiO_2+WO_3 and/or MoO_
3+V_2O_5)=10-80% by weight (b) (TiO
_2+CeO_2+V_2O_5)=10-80% by weight (c)(TiO_2+ZrO_2+V_2O_5)=1
0-80% by weight (d) (WO_3 and/or MoO_3+CeO_
2+V_2O_5)=10-25% by weight (e)(WO_
3 and/or MoO_3+ZrO_2+V_2O_
5) = 10-25% by weight, and the acid-activated three-layer structure each accounts for the remainder of the active ingredient. catalyst. (9) The weight ratio between the metal oxides of the ternary combination is in the following ranges, respectively: (a) WO_3 and/or MoO_3/TiO_2
=0.01-0.25 V_2O_5/TiO_2=0.01-0.11(b)
CeO_2/TiO_2=0.05-0.23V_2O
_5/TiO_2=0.01-0.11(c) ZrO_
2/TiO_2=0.01-0.24V_2O_5/T
iO_2=0.01-0.11(d)CeO_2/WO
_3 and/or MoO_3=0.1-5.0 V_2O_5/WO_3 and/or MoO_3=0
．． 1-2.5 (e) V_2O_5/WO_3 and/or MoO_
3=0.1-2.5 ZrO_2/WO_3 and/or MoO_3=0.
1-10. The catalyst according to claim 9, characterized in that the catalyst comprises: 1-10. (10) Molded objects, especially spheres, tablets, extrudates,
11. Catalyst according to any one of claims 1 to 10, characterized in that it is present in the form of an elongated or flat honeycomb, a rod, a tube, a ring, a wheel or a saddle. (11) A patent claim characterized in that it is obtained by impregnating an acid-activated three-layer silicate with a solution containing one or more of the metals as salts and/or complex compounds, and then calcining the acid-activated three-layer silicate. Catalyst according to any one of the ranges 1 to 11. (12) mechanically mixing the acid-activated trilayer silicate with oxides or salts of one or more of said metals and then impregnating with a solution containing one or more of said metals as salts and/or complex compounds; 12. The catalyst according to any one of claims 1 to 11, which is obtained by subjecting the catalyst to oxidation and then calcination. (13) at least one compound containing one or more of the metals is precipitated or reprecipitated in the presence of a suspension of acid-activated trilayer silicate, foreign ions are washed away, and then The catalyst according to any one of claims 1 to 11, which is obtained by calcination. (14) At least one compound containing one or more of the metals is added in the presence of a mixed suspension of an acid-activated trilayer silicate and one or more oxides or salts of the metals. Claims 1 to 11 are obtained by precipitating or reprecipitating, washing and removing foreign ions, and then calcining.
Catalyst according to any of paragraphs. (15) Claim 1, characterized in that NH_3 is used as a reducing agent in order to reduce the nitrogen oxide content of combustion exhaust gas that also contains sulfur oxides in addition to general exhaust gas components. 16. The catalyst according to any one of items 15 to 15. (16) 200-600°C, preferably 250-430°C
Temperature range of °C and 500-2000 m/hr per liter of catalyst
17. The catalyst according to claim 16, which is used at a space-time velocity in the range of 0l combustion exhaust gas.