JPS6268541A - Preparation of catalyst for removing nitrogen oxide - Google Patents

Abstract

PURPOSE:To obtain a catalyst having a low SO2 oxidizing rate and a high nitrogen oxide removing rate, by a method wherein Ti-sulfate is neutralized, hydrolyzed and baked to obtain a baked product which is, in turn, mixed with a W-compound and/or a Mo-compound and the resulting mixture is dried and baked. CONSTITUTION:A basic substance is added to Ti-sulfate to neutralize and hydrolyze the same while the obtained ortho Ti-acid precipitate is dried and baked to obtain a baked product being anatase type Ti-oxide. Subsequently, WO3 or a precursor (e.g., ammonium para tungstate) thereof and/or MoO3 or a precursor (e.g., ammonium molybdate) thereof are added to said baked product in an amount of 5-50wt% of Ti-oxide as WO3 and MoO3. Water is added to and kneaded with the resulting mixture while the kneaded mixture is molded into an arbitrary shape and subsequently baked at 800 deg.C or less to obtain a catalyst for removing nitrogen oxide. Further, a catalytically active component for removing nitrogen oxide may be supported by said catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a catalyst for removing nitrogen oxides, and more particularly, to a method for producing the above catalyst in which sulfur dioxide is not oxidized during nitrogen oxide removal.

(Prior art) The use of calcined titanium oxide as a carrier or a catalyst has already begun, but its surface area, crystal shape, mechanical strength, heat resistance, etc. have important effects on the carrier or catalyst function. Various manufacturing methods have been proposed in the past because they differ depending on the manufacturing method and the presence/absence, type, amount, etc. of additives.

It is already known that if titanium is thermally hydrolyzed, it will easily become metatitanic acid, and if it is calcined, it will become anatase-type titanium oxide, which is generally a preferred crystal form as a carrier or catalyst. It is used as a carrier material for removal catalysts.

(Two points to be solved by the invention) The present invention is not satisfied with the performance of anatase-type titanium oxide, which is currently used as a raw material for metatitanic acid, and aims to further improve the performance.

(Ninth Means to Solve All Problems) The inventors of the present invention have conducted intensive studies to achieve all of the above-mentioned performance improvements, and as a result, purified titanium sulfate ('I'10SO4
)t” Neutralized and hydrolyzed with a basic substance such as ammonia,
Orthotitanic acid (Ti(OH)4) obtained by washing with water
By mixing a tungsten compound and/or a molybdenum compound with the calcined product, drying it, and calcining it, a catalyst with a large surface area, excellent strength, and heat resistance can be used to remove the oxidized element, or various catalysts. This invention has led to the proposal of the present invention.

That is, the present invention provides: (1) A nitrogen oxide product characterized in that: (1) a tungsten compound and/or a molybdenum compound is mixed into a fired product obtained by firing after complete neutralization and hydrolysis of titanium sulfate, followed by drying and firing; Method for producing a catalyst for removal, (2) After complete neutralization and hydrolysis of titanium sulfate, a tungsten compound and/or a molybdenum compound is mixed into the fired product obtained by firing, followed by drying and firing. The present invention relates to a method for producing a catalyst for removing nitrogen oxides, which comprises supporting a catalyst component for removing crab oxides.

The basic substance used in the neutralization hydrolysis of titanium sulfate in the present invention may be any basic substance, but aqueous ammonia is preferable because it can be easily washed with water after the reaction. The nine-orthotitanic acid precipitate thus produced is washed with water, filtered, and dried.
Next, it is fired at a temperature of 800°C or lower, preferably 700 to 500°C, and pulverized to obtain a powdered fired product.

In this case, according to the present invention, by using orthotitanic acid produced by neutralizing and hydrolyzing titanium sulfate, sulfate radicals are contained, even in trace amounts, and these sulfate radicals act as carriers and catalysts during firing. This is one of the reasons for producing the preferable anatase type titanium oxide.

The tungsten compound used in the present invention is tungsten oxide or a precursor that forms tungsten oxide by firing, and examples of this precursor include ammonium paratungstate. Similarly to Mayu, the molybdenum compound used in the present invention is molybdenum oxide or a precursor that gives molybdenum oxide by calcination, and the precursor includes, for example, ammonium molybdate, and in any case, it is anatase type. Considering the homogeneous miscibility with titanium oxide, a solution form is preferable.

The addition of the tungsten compound and/or molybdenum compound is 5 to 50 weight percent based on titanium oxide as WO3, MoO3, and when the amount added is less than 5 weight percent, when the orthotitanic acid is fired, The effect of suppressing crystal growth is poor, and even if the amount exceeds 50% by weight, no significant effect is observed, which is not desirable from an economical point of view.

Anatase type titanium oxide and tungsten compounds and/
Or add an appropriate amount of water to a mixture of molybdenum compounds (when using tungsten compounds and molybdenum compounds in solution form, addition of water may not be necessary), knead,
Any conventionally known method, such as extrusion,
It is fired after being molded into an arbitrary shape by a method such as rolling granulation. The firing temperature is 800°C or less, preferably 7 o =
It may be fired at a temperature of 30°C. In this way,
By applying the present invention, fired products of titanium oxide, tungsten oxide and/or molybdenum oxide can be obtained in the form of powder or molded products.

Of course, during molding, conventionally known molding aids, such as methyl cellulose (manufactured by Asahi Kasei (e.g., Avicel)), etc., may of course be used.
In the present invention, the firing atmosphere is not limited in any way; air,
It may be a combustion gas, an inert gas, or the like.

As shown in Figure 1, it is confirmed that the fired product obtained by the present invention contains ungrown anatase, as shown in Figure 1, and its X-ray spectrum shows a low and broad peak. In the case of type titanium oxide, its X-ray spectrum has a high and sharp peak, as shown in Figure 2, because the crystals have grown extremely well.

The fired titanium oxide product according to the present invention can be used as it is as a catalyst for removing nitrogen oxides or as a carrier.

When used as a carrier, the fired titanium oxide product obtained as described above can be supported with an oxide known to have catalytic activity for removing nitrogen oxides. Due to the unexpected synergistic effect with ammonia, it is possible to obtain a catalyst for removing nitrogen oxides with excellent selective catalytic reduction performance of nitrogen oxides using ammonia as a reducing agent.

In the present invention, vanadium, tungsten, molybdenum, copper, iron,
This method supports an oxide of at least 1'm of an element selected from chromium, manganese, and cerium, and the method of supporting the above-mentioned oxide on a fired titanium oxide product has been conventionally used in the preparation of catalysts. can be by any method,
For example, a fired product molded into a predetermined shape may be completely impregnated or coated with a solution or dispersion containing the oxide or its precursor, and then fired at a predetermined temperature if necessary. Of course, the nitrogen oxide removal catalyst of the present invention can also be obtained by kneading the powdered calcined product with the solution or dispersion, molding it into a desired shape, and then calcining it to a predetermined temperature as necessary. .

In order to remove nitrogen oxide gold from a mixed gas containing nitrogen oxides using the catalyst of the present invention, ammonia is added in an amount α5 to 5 times the mole, preferably 1 to 2 times the mole of nitrogen oxides contained in the mixed gas. , this is passed through a reaction bed completely filled with catalyst. Any of a moving bed, a fluidized bed, a fixed bed, etc. can be used as the reaction bed.

The catalyst of the present invention contains at least a tungsten compound and a molybdenum compound selected from the group consisting of a tungsten compound and a molybdenum compound, and has excellent heat resistance. ~500°C. The space velocity of gas is 1,000 to 100,00
0hr-' preferably from 4000 to 3000 hr
-' range.

The catalyst according to the invention can be used to treat any gas containing all nitrogen oxides, but in particular boiler exhaust gas, i.e.
00-1000 ppm of nitrogen oxides, mainly nitrogen monoxide, as well as 200-2000 ppm of sulfur oxides,
Mainly sulfur dioxide, 1 to 10 volumes of oxygen, 5 to 20
It can be suitably used to remove nitrogen oxides from exhaust gas containing 5 to 20 volumes of carbon dioxide gas and 5 to 20 volumes of water vapor.

(Function) As described above, in the method of the present invention, a tungsten compound and/or a molybdenum compound is uniformly dispersed in anatase-type titanium oxide made of orthotitanic acid, and the resulting fired product has improved mechanical strength and heat resistance. has been significantly revised.

Therefore, in the catalyst for removing nitrogen oxides consisting of the fired product itself, or the catalyst for removing nitrogen oxides in which a metal oxide having catalytic activity for removing nitrogen oxides is supported, anatase-type titanium oxide is used. Due to the synergistic effect of tungsten oxide and/or molybdenum oxide, or the synergistic effect of these and the above metal oxides, it not only maintains a high level of snow oxide removal activity for a long period of time even under severe usage conditions, but also removes sulfur dioxide. Since the oxidation force to sulfur trioxide is extremely low, it is an excellent practical and industrial catalyst for removing nitrogen oxides.

(Examples) The present invention will be explained below using Examples, but the present invention is not limited to these Examples in any way.

Example 1 A titanium sulfate solution obtained from the titanium oxide manufacturing process using the sulfuric acid method was neutralized and hydrolyzed with aqueous ammonia to obtain orthotitanic acid, and IK9 was taken out as n'kllllized titanium, washed with water, and then heated at 100°C for 12 hours. After a while, another 50
It was baked at 0°C for 3 hours. All samples of this fired product were pulverized using a sample mill and the particle size was adjusted, then a 10-thimethylamine solution containing 110 f'i of ammonium paratungstate was added, kneaded, and then extruded into a lattice-shaped product using an extruder 7. The product was dried by heating from room temperature to 100°C, and then calcined at 500°C for 3 hours to obtain a calcined product according to the present invention, which is useful as a catalyst for removing nitrogen oxides, as will be described later.

The entire X-ray spectrum of the fired product obtained in this way is
As shown in the figure. Since the peak is low and broad, it is clear that the anatase crystal remains ungrown.

The X-ray spectra were obtained using an X-ray diffraction system (I) manufactured by Rigaku Denki Co., Ltd.
Measurement was performed using RAD-[IA i, and the measurement conditions are as follows.

Quantitation speed 1°/4 min Full scale 1000 cps Time constant 1 sec Chart speed 10/min Target Copper blue voltage 30 KV Lightning current 10 mA Ninth for comparison, the complete X-ray spectrum of the commercially available pigment anatase titanium oxide is shown in Figure 2. Shown below. The measurement conditions are as above.
Same as above except full scale is 4000 cps.

Example 2 To the ffi product of the mixture of titanium oxide and ammonium paratungstate obtained in Example 1, 300 μg of a methylamine solution containing 120 iF of ammonium molybdate (equivalent to Mo0398t) was added, and the following Example 1 was prepared. Firing was performed in exactly the same manner as the second firing to obtain a fired product. This calcined product was determined to be in a powder state, and was further extruded into a bottom shape to obtain a calcined product that can be used as a catalyst for removing nitrogen oxides.

Example 3 A water bath solution containing 102 ammonium metavanadate, 252 oxalic acid, and t was added to the baked product IK9 of the kneaded product of titanium oxide and ammonium paratungstate obtained in Example 1, and after thorough kneading, extrusion was carried out. Comparative Example: A catalyst for removing nitrogen oxides was obtained by extrusion molding into a lattice-shaped bottom shape using a machine, heating from room temperature to 100°C to dry, then baking at 500°C for 5 hours, and further extrusion molding. 1. A titanium sulfate solution obtained from the titanium oxide production process using the sulfuric acid method is completely hydrolyzed to obtain metatitanic acid, which is
1 q of titanium oxide was taken out, 80 tf of barium chloride (dihydrate) was added as a sol-forming agent to form a sol, stirred and mixed thoroughly, and then dried at 100°C for 12 hours.
Furthermore, it is baked at a temperature of 500℃ for 5 hours. This fired product I
After pulverizing with a Kg'i sample mill and fully adjusting the particle size, a 10-thimethylamine solution containing ammonium paratungstate 1102'fc was added, kneaded, and then extruded into a lattice-shaped molded product using an extruder at room temperature. from 100
Dry by heating to ℃ and then baking at 500℃ for 3 hours to obtain a baked product. It can also be used as a catalyst for removing nitrogen oxides.

Comparative Example 2 In Comparative Example 1, 300 t ILti of a methylamine solution containing ammonium molybdate; Lamb 1202 was added to the calcined product of the kneaded product of titanium oxide containing Tokutomo barium and ammonium paratungstate, and the following procedure was carried out in exactly the same manner as in Comparative Example 1. The fired product is completely baked. This calcined product was in powder form and was further extruded to obtain a calcined product that could be used as a catalyst for removing nitrogen oxides.

Comparative Example 5 A fired product of a mixture of titanium oxide containing barium obtained in Comparative Example 1 and ammonium paratungstate was added with 10f of ammonium metavanadate and 25% of oxalic acid. After adding an aqueous solution containing and sufficiently kneading, the mixture was extruded into a lattice-shaped molded product using an extruder, heated from room temperature to 100°C to dry, then baked at 500°C for 3 hours, and further extruded. The entire catalyst for removing nitrogen oxides was obtained.

Example 4 Production process of titanium oxide by sulfuric acid method The obtained titanium sulfate bath solution was neutrally hydrolyzed with aqueous ammonia to obtain orthotitanic acid, IKg of this A't-titanium oxide was taken out, and after washing with water, it was heated at 100°C. Dry for 12 hours, then dry for another 500
Bake at ℃ for 3 hours.

This fired product was pulverized with a sample mill and the particle size was completely adjusted, and then 300w1t'i of a methylamine solution containing 120f' of ammonium molybdate was added, kneaded, and extruded into a lattice-shaped product using an extruder. After that, it was dried by heating from room temperature to 100℃, and then heated to 500℃ for 3
A fired product according to the present invention was obtained by firing for a period of time. The X-ray spectrum of the fired product obtained as in Example C was measured under the same measurement conditions as in Example 1, and the results confirmed that anatase crystals remained ungrown.

Example 5 A titanium sulfate bath solution obtained from the titanium oxide manufacturing process using the sulfuric acid method was neutralized and hydrolyzed with aqueous ammonia to obtain orthotitanic acid, and this titanium oxide was obtained as lK11'.
It was taken out, washed with water, dried at 100°C for 12 hours, and further baked at 500°C for 3 hours. This fired product was crushed by xv in a sample mill, and after adjusting the particle size to km, 110 tons of ammonium paratungstate and 12 tons of ammonium molybdate were crushed.
A 10-thimethylamine bath solution containing Off was added, and then a catalyst was prepared in the same manner as in Example 1 to obtain a calcined product according to the present invention.

The entire X-ray spectrum of this fired product was measured under the same conditions as in Example 1, and it was confirmed that C and t remained at 11, where anatase type crystals had not grown.

Example 6 The fired product lK11' of the mixture of titanium oxide and ammonium molybdate obtained in Example 4 was heated with an aqueous solution containing 109 ammonium metavanadate and 252 oxalic acid, thoroughly kneaded, and then put into an extruder. It is extruded into a lattice-shaped molded product, heated from room temperature to 100°C to dry it, and then
Calcined at 500°C for 3 hours and further extruded to obtain a total catalyst for removing nitrogen oxides, t0.Example 7 A fired product of the mixture of titanium oxide and ammonium molybdate obtained in Example 4, IKl? A 10-thimethylamine bath solution containing paratungsten finished ammonium 110f gold was added to the mixture, and after kneading, it was extruded into a lattice-shaped molded product using an extruder, heated from room temperature to 100°C and dried, and after a long time of 50%
A fired product according to the present invention was obtained by firing at 0° C. for 5 hours.

Example 8 A water bath solution containing 10 tons of ammonium metavanadate and 251 grams of oxalic acid was added to 1 kg of the calcined product of the mixture of titanium oxide and ammonium paratungstate obtained in Example 5. After thoroughly kneading, the mixture was added to an extruder. J, extrusion molded into a di-lattice molded product, heated from room temperature to 100°C to dry, then calcined at 500°C for 3 hours, and further extruded to obtain a nitrogen oxide removal catalyst fc6 Example? After firing, 1 kg of the kneaded product of titanium oxide and ammonium paratungstate obtained in Example 1 was added with a manganese nitrate water bath solution whose concentration was adjusted so that the concentration of manganese oxide was 5 layers. After kneading, the mixture was extruded into a lattice-shaped molded product using an extruder, heated from room temperature to 100°C to dry, then fired at 500°C for 3 hours, and further extruded to form a catalyst for removing nitric oxides. To each of the catalysts for removing nitrogen oxides obtained in the Examples and Comparative Examples where t0 or more was obtained, 1 ooppms of nitrogen oxides, 100 ppm of ammonia, and 1 ounce of water vapor were added.
0%, 12 divalent carbon, 800 ppm sulfur dioxide,
Nitrogen oxides (N
Ox) removal rate and ion dioxide←(802) oxidation rate were all measured. The results are shown in Table 2. In addition, nitrogen oxide removal rate (
H) and sulfur dioxide oxidation rate (φ) are calculated using the following formulas.

Nitrogen oxide removal rate (%); (catalyst layer inlet NOx Itk
- NOx concentration at catalyst layer outlet) / (NOx concentration at catalyst layer inlet)
Catalyst layer outlet So, concentrated It)/ (Catalyst layer inlet < So,
+1301) concentration)×1o.

Table 2 (Effects of the Invention) As is clear from the above results, according to the catalyst of the present invention, the nitrogen oxide removal system is high, but the sulfur dioxide oxidation rate is low, and the nitrogen oxides in the gas mixture are completely removed. Based on the production of sulfur trioxide when

[Brief explanation of drawings]

FIG. 1 shows an X-ray spectrum of a fired titanium oxide product obtained by the method of the present invention, and FIG. 2 shows an X-ray spectrum of a comparative titanium oxide pigment. Sub-Agent 1) Meifu Agent Ryo Hagiwara - Sub-Agent Atsuo Anzai Figure 1 2θ Figure 2 2゜

Claims (2)

[Claims] (1) Production of a catalyst for removing nitrogen oxides, which is characterized in that a tungsten compound and/or a molybdenum compound is mixed with a fired product obtained by neutralizing and hydrolyzing titanium sulfate, followed by drying and firing. Method. (2) After neutralizing and hydrolyzing titanium sulfate, a tungsten compound and/or a molybdenum compound is mixed into the fired product obtained by firing, followed by drying and firing, and a nitrogen oxide removal catalyst is added to the fired product. A method for producing a catalyst for removing nitrogen oxides, which comprises supporting an active ingredient.