JP3474514B2 - Low temperature denitration catalyst and low temperature denitration method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a waste incineration exhaust gas,
In addition, a low-temperature denitration catalyst that reduces and removes nitrogen oxides contained in various exhaust gases at a low temperature around 150 ° C. and suppresses by-products such as N ₂ O in the presence of a reducing agent such as ammonia, and this catalyst The present invention relates to a low temperature denitration method used.

[0002]

2. Description of the Related Art In recent years, environmental pollution has been regarded as a problem worldwide, and various measures for preventing pollution have been proposed, and at the same time, wastewater and exhaust gas emission standards have been reviewed and studied. Nitrogen oxide (NOx), which is a major air pollutant in the combustion exhaust gas
Is included. Various NOx removal technologies have been proposed and put to practical use as measures against NOx. The most widely used denitration system is the selective catalytic reduction system (SCR).
As the catalyst, a titanium oxide carrier carrying vanadium oxide is used, and NOx is reduced by reaction with coexisting ammonia to produce harmless water and nitrogen.

Since this conventional catalyst is active at a high temperature of 200 to 400 ° C., the denitration catalyst device is operated at a temperature exceeding 200 ° C. in order to obtain an appropriate denitration performance. Therefore, as shown in FIG. 2, the exhaust gas coming out of the dust removing equipment 10 such as a bag filter and once cooled to about 150 ° C., at a temperature exceeding 200 ° C. at the inlet of the denitration device 14 in the exhaust gas heater 12, is desirable. Had to be reheated to 210 ° C. or higher and consumed a great deal of heat energy.

Conventionally, a vanadium-based catalyst has been known, but when a denitration apparatus is operated at a temperature of less than 200 ° C. in a system using this vanadium-based catalyst, a large amount of catalyst is required due to its low catalytic activity. In addition, the vanadium-based catalyst itself is expensive.

Japanese Unexamined Patent Publication No. 8-131828 discloses a nitrogen oxide removing catalyst in which titanium dioxide is supported with manganese oxide and cerium oxide. In addition, JP-A-9
Japanese Patent Publication No. 155190 discloses that titanium oxide is used as a carrier,
Manganese is kneaded and / or impregnated and supported with nitrate,
A calcined nitrogen oxide removal catalyst is described.

[0006]

The manganese-based catalysts described in these publications show some high activity at low temperatures around 150 ° C., but have the property of producing N ₂ O, which is a global warming substance, as a by-product. There is a point.

The present invention has been made in view of the above points,
An object of the present invention is to have a higher activity than conventional catalysts at a low temperature of 200 ° C. or lower, preferably 180 ° C. or lower, suppress the by-production of N ₂ O, and reduce the cost. It is to provide a low temperature denitration catalyst and a low temperature denitration method using this catalyst.

[0008]

To achieve the above object, according to the Invention The low-temperature denitration catalyst of the present invention, the titanium oxide carrier, manganese compounds, by supporting at least one of arrangement in motor Ribuden compounds and chromium compounds Is configured to be. In this catalyst, a cerium compound may be further supported. Further, the low temperature denitration catalyst of the present invention,
Titanium oxide carrier, manganese compound and tungsten
Compound, and then a cerium compound.
It is characterized by becoming. Further, there is a case where at least one of a copper compound and a platinum group metal compound is further supported on the support of the cerium compound.
In addition, the low temperature denitration catalyst of the present invention has a titanium oxide support and a matrix.
The gangan compound and the tungsten compound.
And at least one of a copper compound and a platinum group metal compound
It is characterized in that it is carried.

The low temperature denitration catalyst of the present invention is characterized in that a manganese compound and a copper compound are supported on a titanium oxide carrier. In this catalyst,
A cerium compound may be supported. Also, the present invention
The low temperature denitration catalyst of is a manganese compound on a titanium oxide support.
And a platinum group metal compound supported, and further cerium
It is characterized by supporting a compound. The "low temperature" in the present specification is, in a broad sense, 130 to 200 ° C,
In a narrow sense, it means a range of 150 to 180 ° C.

In the low temperature denitration method of the present invention, the exhaust gas at 130 to 200 ° C. containing nitrogen oxides is introduced together with a reducing agent into a catalyst device using any of the above low temperature denitration catalysts, and nitrogen in the exhaust gas is introduced. It is characterized by reducing and removing oxides. Further, the low-temperature denitration method of the present invention introduces an exhaust gas of 150 to 180 ° C. containing nitrogen oxides together with a reducing agent into a catalyst device using any of the above low-temperature denitration catalysts to perform nitrogen oxidation in the exhaust gas. It is characterized by reducing and removing things. Ammonia, urea, etc. are used as the reducing agent. Moreover, the catalyst is filled as a granular body, a honeycomb-shaped body, or the like. When filling the granular material, it is used as a fixed bed or a moving bed.

Titanium oxide as a carrier is produced by a general method such as a sulfuric acid method, a gas phase method, a sol-gel method or the like. Its specific surface area is preferably 10 m ² / g or more.
When the specific surface area of titanium oxide is less than 10 m ² / g, sufficient catalytic activity cannot be obtained. The manganese compound which is the catalytically active component is supported on the titanium oxide by using divalent, trivalent or tetravalent manganese oxide, inorganic hydrochloric acid or organic hydrochloric acid. Generally, manganese nitrate, manganese sulfate or manganese oxalate is used. The supporting is performed by a known method such as a spray method, a dipping impregnation method, a kneading method, a precipitation method, a sputtering method and the like. For example, a manganese compound is dissolved in a soluble solvent such as water, and titanium oxide is immersed in the solution, and then the temperature is adjusted to room temperature to 2
It is dried at 00 ° C. and then calcined in air at 100 to 600 ° C. to obtain manganese-supported titanium oxide.

It is presumed that the manganese compound supported as described above is finally an oxide on the carrier. The supported amount of manganese is 0.1 to 30 wt%, preferably 1 to 20 wt% based on the manganese element. If the supported amount is less than 0.1 wt%, sufficient denitration performance cannot be obtained, and if it exceeds 30 wt%, the specific surface area of the catalyst decreases, which has the opposite effect and sufficient denitration performance cannot be obtained.

The other catalytically active component of the Group 6A element, namely tungsten, molybdenum or / and chromium, is 2
It is supported on the titanium oxide using any one of trivalent, trivalent, tetravalent, pentavalent and hexavalent oxides, inorganic hydrochloric acid and organic hydrochloric acid.
Generally, ammonium paratungstate, ammonium molybdate, and chromium nitrate are used. The supporting is performed by a known method such as a spray method, a dipping impregnation method, a kneading method, a precipitation method, a sputtering method and the like. For example, a tungsten compound is dissolved in a soluble solvent such as water, titanium oxide is immersed in the solution, dried at room temperature to 200 ° C., and then baked in air at 100 to 600 ° C. to carry tungsten oxide on titanium. And

The tungsten compound supported as described above is presumed to be an oxide finally on the carrier. The amount of tungsten supported is 0.1 to 30% by weight, preferably 1 to 20% by weight, based on the elements. If the supported amount is less than 0.1 wt%, sufficient denitration performance and N ₂ O suppressing effect cannot be obtained, and if it exceeds 30 wt%, the specific surface area of the catalyst decreases, which is the opposite effect and sufficient denitration performance is obtained. I can't.

Cerium, which is another catalytically active component, is divalent,
It is supported on the titanium oxide by using any one of trivalent and tetravalent oxides, inorganic hydrochloric acid and organic hydrochloric acid. Cerium nitrate is generally used. Supporting is spray method, immersion impregnation method,
It is carried out by a known method such as a kneading method, a precipitation-precipitation method, or a sputtering method. For example, a cerium compound is dissolved in a soluble solvent such as water, titanium oxide is immersed in the solution, dried at room temperature to 200 ° C., and then baked in air at 100 to 600 ° C. to obtain cerium-supported titanium oxide. To do.

The tungsten compound supported as described above is presumed to be an oxide finally on the carrier. The amount of cerium supported is 0.1 to 30% by weight, preferably 1 to 20% by weight based on the elements. If the supported amount is less than 0.1 wt%, sufficient denitration performance cannot be obtained, and if it exceeds 30 wt%, the specific surface area of the catalyst decreases, which has the opposite effect and sufficient denitration performance cannot be obtained.

In addition to the above catalyst component, a copper compound and / or a platinum group metal compound, that is, a compound of ruthenium, rhodium, palladium, osmium, iridium or platinum can be supported as a catalyst component. The copper compound is supported on the titanium oxide using a monovalent or divalent copper oxide, an inorganic acid or an organic acid. Generally, copper nitrate is used. The supporting is performed by a known method such as a spray method, a dipping impregnation method, a kneading method, a precipitation method, a sputtering method and the like. For example, a copper compound is dissolved in a soluble solvent such as water,
After immersing titanium oxide in the solution, room temperature to 200 ° C
And then baked in air at 100 to 600 ° C. to obtain copper-supported titanium oxide. The copper compound supported as described above is presumed to be an oxide finally on the carrier. The amount of supported copper is 0.0001 to 30% by weight, preferably 0.01 to 20% by weight, based on the element. Carrying amount 0.0001
If it is less than wt%, sufficient denitration performance effect cannot be obtained, and if it exceeds 30 wt%, the specific surface area of the catalyst decreases, which has an adverse effect and sufficient denitration performance cannot be obtained.

The platinum group metal (element) compound is supported on the titanium oxide by using oxides of various valences, inorganic acids and organic acids. Generally, copper nitrate is used. The supporting is performed by a known method such as a spray method, a dipping impregnation method, a kneading method, a precipitation method, a sputtering method and the like. For example, a platinum compound is dissolved in a soluble solvent such as water, titanium oxide is immersed in the solution, dried at room temperature to 200 ° C., and then baked in air at 100 to 600 ° C. to carry platinum-supported titanium oxide. And Platinum loading is 0.0001-30wt% based on element
And preferably 0.01 to 20 wt%. If the supported amount is less than 0.0001 wt%, a sufficient denitration performance effect cannot be obtained, and if it exceeds 30 wt%, the specific surface area of the catalyst decreases, which is an adverse effect and sufficient denitration performance cannot be obtained. The above compounds may be loaded in any order, or may be loaded simultaneously.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments, and can be appropriately modified and implemented. FIG. 1 shows an apparatus for carrying out a low temperature denitration method according to a first embodiment of the present invention. Exhaust gas, for example, exhaust gas from a refuse incineration plant, is cooled by a temperature reducing device (not shown) and introduced into the bag filter 20. In this case, the exhaust gas temperature is set to 20 in order to keep the bag filter service temperature below.
The temperature is 0 ° C or lower, preferably 180 ° C or lower.

Immediately before the bag filter 20, chemicals such as activated carbon and slaked lime (or quick lime) are added to the exhaust gas so that dioxins are activated carbon and HCl is slaked lime (or quick lime).
Acidic components such as SOx are removed. 200 ° C. or less, preferably 180 ° C. or less, which exits the bag filter 20, for example, 1
The exhaust gas at 50 ° C. is introduced into the NOx removal device 22 as it is together with the reducing agent, for example, ammonia, and NO in the exhaust gas is discharged.
x, NH ₃ and O ₂ react to reduce to H ₂ O and N ₂ to render them harmless. Thus, in the present embodiment, as shown in FIG.
Since the exhaust gas heater 12 which has been conventionally required as shown in (3) is no longer required, it is possible to construct a denitration process with less thermal energy.

The denitration device 22 is filled with the low temperature denitration catalyst of the present invention in the form of particles or a honeycomb. In the case of filling the granular material, it may be a fixed bed or a moving bed. Denitration device 22
The lower limit of the temperature of the exhaust gas introduced into the chamber is 130 ° C, preferably 150 ° C, and the upper limit is 200 ° C, preferably 180 ° C. If the exhaust gas temperature is below the lower limit, the activity of the catalyst will be low, while if the exhaust gas temperature exceeds the upper limit, the bag filter 20 will be burnt, which is not preferable. Although the exhaust gas temperature slightly drops in the bag filter 20, the temperature drop is ignored in the description of the present embodiment.

[0022]

EXAMPLES Examples and comparative examples will be shown below to further clarify the features of the present invention. Comparative Example 1 4.6 g (hereinafter, the same supported amount) of ammonium metavanadate (NH ₄ VO ₃ , the same vanadium compound will be used hereinafter) was reduced with oxalic acid to prepare an aqueous vanadium ion solution, and 38 g of titanium oxide (Japan Aerosil Made, product name P
-25, the same titanium oxide will be used hereinafter). Then, after drying the kneaded product in a dryer at 110 ° C. overnight,
It was crushed and sized to a diameter of 2-3 mm. Next, this was baked in an electric furnace at 400 ° C. for 3 hours in air (drying, sizing, baking conditions are the same below).

[0023] Comparative Example 2 Ammonium metavanadate and ammonium tungstate _{5.7g ((NH 4) 10 W} 12 O 41 · 5H 2 O = 3
132.52 (the same tungsten compound is used hereinafter) was reduced with oxalic acid to prepare an aqueous solution of vanadium and tungsten ions, which was kneaded with 34 g of titanium oxide, dried, sized and calcined.

Comparative Example 3 Ammonium metavanadate and 5.7 g of ammonium tungstate were reduced with oxalic acid to prepare vanadium and tungsten ion aqueous solutions. This aqueous solution and 0.2
g colloidal silica (Snowtex 4 manufactured by Nissan Kagaku)
0) was kneaded with 34 g of titanium oxide, dried, sized and calcined.

Comparative Example 4 26.1 g of manganese nitrate hexahydrate (Mn (NO) ₃ .multidot.
6H ₂ O (hereinafter the same manganese compound was used) was dissolved in distilled water, added to 45 g of titanium oxide, kneaded, dried, sized and calcined.

Comparative Example 5 Manganese nitrate hexahydrate and 15.5 g of cerium nitrate 6
The hydrate (Ce (NO ₃ ) .6H ₂ O) was dissolved in distilled water, added to 40 g of titanium oxide, kneaded, dried, sized,
Baked.

Test Example 1 Manganese nitrate hexahydrate was dissolved in distilled water, and ammonium tungstate was dissolved in 7.1 g of distilled water. Then, these were simultaneously added to 40 g of titanium oxide and kneaded. After drying this in a 110 ° C. oven overnight,
It was crushed and sized to a diameter of 2-3 mm. Then, this was fired in an electric furnace at 300 ° C. for 3 hours in air (drying, sizing, firing conditions are the same below).

[0028] Example 1 of manganese nitrate hexahydrate was dissolved in distilled water, and ammonium molybdate _{((NH 4) 6 Mo 7} O 24 · 4H 2 O
= 123.86) was dissolved in 64.4 g of distilled water. Then, these were simultaneously added to 40 g of titanium oxide, kneaded, dried, sized, and fired.

[0029] EXAMPLE 2 manganese nitrate hexahydrate was dissolved in distilled water, and chromium nitrate nonahydrate _{(Cr (NO 3) 3 ·} 9H 2 O = 400.1
5) was dissolved in 38.5 g of distilled water. 40 parts of this aqueous solution
In addition to g of titanium oxide, kneaded, dried, sized, and fired.

Example 3 Manganese nitrate hexahydrate was dissolved in distilled water, and copper nitrate 3 was added.
Hydrate _{(Cu (NO 3) 2 ·} 3H 2 O = 241.60)
Was dissolved in 19 g of distilled water. This aqueous solution was added to 40 g of titanium oxide, kneaded, dried, sized, and fired.

Test Example 2 Manganese nitrate hexahydrate was dissolved in distilled water, and chloroplatinic acid (H ₂ PtCl ₆ .H ₂ O = 517.90) was added to 1.3.
g Dissolved in distilled water. This aqueous solution was added to 44.5 g of titanium oxide, kneaded, dried, sized, and fired.

Test Example 3 Manganese nitrate hexahydrate was dissolved in distilled water, and 1.1 g of palladium nitrate (Pd (NO ₃ ) ₂ = 230.43) was added.
It was dissolved in distilled water. This aqueous solution was added to 44.5 g of titanium oxide, kneaded, dried, sized, and fired.

Test Example 4 Manganese nitrate hexahydrate was dissolved in distilled water, and ruthenium chloride (RuCl ₃ = 207.43) was dissolved in 1 g of distilled water. Add this aqueous solution to 44.5 g of titanium oxide,
The mixture was kneaded, dried, sized, and fired.

Test Example 5 Manganese nitrate hexahydrate was dissolved in distilled water, and rhodium chloride trihydrate (RhCl ₃ .3H ₂ O) was dissolved in 1 g of distilled water. This aqueous solution was added to 44.5 g of titanium oxide, kneaded, dried, sized, and fired.

Test Example 6 Manganese nitrate hexahydrate was dissolved in distilled water, and iridium chloride (IrCl ₃ ) was dissolved in 0.8 g of distilled water. This aqueous solution was added to 44.5 g of titanium oxide, kneaded, dried, sized, and fired.

Examples 4 to 14 Each of manganese, tungsten, molybdenum, chromium, copper, platinum, and cerium was used as a comparative example 5 and a test example.
1, 2, the same compound as in Examples 1 to 3 was used to prepare an aqueous solution, and each element was kneaded with an amount of titanium oxide adjusted to have the same loading ratio as in the above example, followed by drying, sizing, As a result of calcination, a catalyst containing the components shown in Table 1 was obtained. In addition,
The “adjusted amount of titanium oxide” is titanium oxide in the case where the amount of supported elements increases and the amount of titanium oxide is reduced so that the proportion of manganese and the like in the entire catalyst is kept constant. Moreover, Comparative Examples 1-5, Test Examples 1-6, and Example 1-
The catalyst components of 3 are also shown in Table 1.

[0037]

[Table 1]

Example 15 10 ml of the catalysts of Examples 1 to 14, Test Examples 1 to 6 and Comparative Examples 1 to 5 were filled in a reactor, and the NOx concentration detected at the inlet and outlet of the reactor was measured. Measurement conditions are temperature 150
℃, SV6700 (1 / h), gas composition NOx100pp
m 2, ammonia 110 ppm, oxygen 10%, water 15%, and nitrogen balance. The denitration rate was defined as follows. The results are shown in Table 1. Denitration rate (%) = (NOx concentration at inlet (ppm) -NOx at outlet)
Concentration (ppm)) / Inlet NOx concentration (ppm) x 100

From the performance results of various denitration catalysts shown in Table 1, from Test Example 1, Examples 1 and 2 , by adding W, Mo and Cr, N ₂ was maintained while maintaining the activity of the Mn-based catalyst.
It can be seen that the by-product of O can be suppressed. Example 3, test example
From 2 to 6 , it can be seen that the activity of the catalyst added with Cu to Ir is improved. From Examples 4 to 8 , the activity of the catalyst to which Ce was added was improved as compared with Examples 1 to 3 and Test Examples 1 and 2 . According to Examples 9 and 10 , the catalyst to which W is added is suppressed in by-product N ₂ O as compared with Example 3 and Test Example 2 . Examples 11 to 14 have the highest activity and N as a by-product.
_It can be seen that ₂ O is also relatively small.

[0040]

Since the present invention is configured as described above, it has the following effects. (1) The catalyst of the present invention has a temperature of 200 ° C. or lower, preferably 1
At a low temperature of 80 ° C. or less, it is possible to construct a compact catalyst denitration system which has higher activity than conventional catalysts and can reduce heat loss. (2) Byproducts of N ₂ O, which is a global warming substance, can be suppressed. (3) By using manganese as the main active component, it is possible to obtain a catalyst at a lower cost than conventional vanadium-based catalysts.

[Brief description of drawings]

FIG. 1 is a systematic schematic configuration diagram showing an apparatus for carrying out a low-temperature denitration method according to a first embodiment of the present invention.

FIG. 2 is a systematic schematic configuration diagram showing an example of an apparatus for performing a conventional denitration method.

[Explanation of symbols]

10 Dust removal equipment 12 Exhaust gas heater 14, 22 Denitration equipment 20 bug filters

(72) Inventor Seiichi Sugawa 1-1 Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries Ltd. Akashi factory (72) Hironori Ozaki 1-3-3 Higashikawasaki-cho, Chuo-ku, Kobe Kawasaki Heavy Industry Co., Ltd. Kobe Head Office (56) Reference Japanese Patent Laid-Open No. 63-319049 (JP, A) Table 6-509273 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B01J 21/00-38/74 B01D 53 / 86,53 / 94

Claims (10)

(57) [Claims] To 1. A titanium oxide carrier, manganese compound, the low-temperature denitration catalyst, characterized by comprising by supporting at least one of parallel <br/> beauty the motor Ribuden compounds and chromium compounds. 2. A low-temperature denitration catalyst comprising a titanium oxide carrier on which a manganese compound and a copper compound are supported. 3. The low-temperature denitration catalyst according to claim 1, which further carries a cerium compound. 4. The low-temperature denitration catalyst according to claim 2, which further carries a cerium compound. 5. A titanium oxide carrier, a manganese compound and
A tungsten compound is supported on the cerium compound.
A low-temperature denitration catalyst characterized by supporting a substance. 6. A titanium oxide carrier, a manganese compound, and
A tungsten compound is supported, and a copper compound and
Do not support at least one of the platinum group metal compounds.
A low-temperature denitration catalyst characterized by the following. 7. A titanium oxide carrier, a manganese compound and
Platinum group metal compound supported, and further cerium compound
A low-temperature denitration catalyst, characterized in that 8. Further, according to claim 3 or 5 low denitration catalyst according was supported at least one of a copper compound and a platinum group metal compound. 9. The catalytic device using a low temperature denitration catalyst according to any one of claims 1-8, contains nitrogen oxides 13
A low-temperature denitration method comprising introducing exhaust gas at 0 to 200 ° C. together with a reducing agent to reduce and remove nitrogen oxides in the exhaust gas. To the catalytic converter using a low-temperature denitration catalyst according to any one of claims 10] according to claim 1-8, 1 containing nitrogen oxides
A low-temperature denitration method comprising introducing exhaust gas at 50 to 180 ° C. together with a reducing agent to reduce and remove nitrogen oxides in the exhaust gas.