JP2003047845A - Catalyst for treating exhaust gas and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vanadia-based catalyst for treating an exhaust gas at a low cost, with which nitrogen oxides and dioxins can simultaneously be detoxyfied at the temperature of >=100 and <=300 deg.C, preferably of >=150 and <=200 deg.C. SOLUTION: A pentavalent vanadium compound such as V2 O5 or NH4 VO3 is used as a starting material of vanadium, and a solution containing a trivalent vanadium compound is prepared by reducing the valence of vanadium from pentavalent to trivalent using a reducing agent. Further, a vanadia-based active component is highly dispersed on a carrier of titanium dioxide or a titanium oxide-based complex oxide by coprecipitating the above solution together with a solution containing a titanium compound.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an exhaust gas treatment catalyst and exhaust gas treatment for detoxifying halogenated aromatic compounds such as nitrogen oxides (NOx) and dioxins contained in exhaust gas simultaneously or individually. A method and an exhaust gas treatment device.

[0002]

2. Description of the Related Art Nitrogen oxides and halogenated aromatic compounds such as dioxins in exhaust gas from boilers, garbage incinerators, etc. are environmental pollutants. In particular, it is known that dioxins are easily produced in a garbage incinerator or the like, which has become a big social problem in recent years. As a method for detoxifying NOx for environmental purification, for example, a carrier made of titanium oxide (TiO ₂ ) disclosed in Japanese Patent No. 2633316 and 5
Valent vanadium compound vanadium pentoxide (V
There is a catalytic reduction method in which NOx is reduced using ammonia (NH ₃ ) as a reducing agent and a catalyst supporting an active component composed of ₂ O ₅ ) and tungsten trioxide (WO ₃ ). However, in this method, when the exhaust gas temperature becomes lower than about 200 ° C., the denitration rate, that is, the nitrogen oxide treatment performance deteriorates. On the other hand, in order to remove dioxins, it is necessary to treat the exhaust gas at a low temperature of about 200 ° C. or lower at which the vapor pressure becomes low. That is, the treatment of NOx and the treatment of dioxins cannot be performed at the same temperature. Therefore, in this method, for example, a first step of removing dioxins at a low temperature of about 150 ° C, a second step of reheating exhaust gas to 200 ° C, and a third step of treating NOx are sequentially performed. However, the configuration and operation of the device becomes complicated, which is a problem.

Further, in JP-A-2000-210561 and JP-A-2001-038206, trivalent water is produced by a coprecipitation method using vanadium trichloride (VCl ₃ ) which is a trivalent vanadium compound as a raw material. After supporting vanadium oxide on TiO ₂ and heating them in an oxidizing atmosphere to change the valence of vanadium from trivalent to pentavalent, NOx and dioxins are simultaneously decomposed even in a low temperature region around 150 ° C. The catalyst that can be used is provided. However, trivalent VCl ₃ has a high raw material cost, and
Since it is not easy to handle, it is not suitable for mass production.

In another conventional example, conventionally, a catalyst is prepared by an impregnation method using a raw material such as ammonium metavanadate, so that the active component is non-uniformly supported even by heat treatment at high temperature, and a uniform composite oxide is obtained. Therefore, good catalytic activity cannot be obtained.

Here, the nitrogen oxides treated in the present invention usually refer to NO and NO ₂ as well as a mixture thereof, and are also called NOx. However, in addition to these, the NOx often contains unstable nitrogen oxides of various oxidation numbers. Therefore, x
Is not particularly limited, but is usually a value of 1 or more and 2 or less. NOx turns into nitric acid, nitrous acid, etc. in rainwater, and NO is said to be one of the main causative substances of photochemical smog, and is a compound harmful to the human body.

Dioxins are a general term for polyhalogenated dibenzo-p-dioxins (PXDDs) and polyhalogenated dibenzofurans (PXDFs). Of these, particularly dibenzo-p-dioxin tetrachloride (T ₄ CDD) is known to have the strongest toxicity.

[0007]

DISCLOSURE OF THE INVENTION The object of the present invention is 10
0 ° C to 300 ° C, preferably 150 ° C to 200
An object of the present invention is to provide a vanadia-based exhaust gas treatment catalyst that can simultaneously detoxify nitrogen oxides and dioxins at a low temperature of ℃ or lower at low cost.

[0008]

In the present invention, a pentavalent vanadium compound such as V ₂ O ₅ or NH ₄ VO ₃ having a low cost is used as a starting material for vanadium, and a vanadium valence is reduced by using a reducing agent. It is characterized in that the solution is reduced from pentavalent to trivalent, and the vanadia-based active ingredient is highly dispersed on a carrier composed of titanium dioxide or titanium oxide-based composite oxide by a coprecipitation method with a titanium compound solution.

The present inventors have earnestly studied to develop an inexpensive method for producing a catalyst having a high simultaneous decomposition activity of NOx and dioxins even at a low temperature of 150 ° C. or higher and 200 ° C. or lower. As a result, we have found that vanadium pentoxide (V ₂ O ₅ ) or ammonium vanadate (NH ₄ V
O ₃ ) as a starting material, and a solution obtained by reducing the valence of vanadium from pentavalent to trivalent with a reducing agent in a solution of these aqueous solutions or water containing a water-soluble alcohol is used as a raw material of the active ingredient. It has been found that this will solve this problem.

Further, the method of the present invention is characterized in that the catalyst is produced by the coprecipitation method. Therefore, it is possible to highly disperse the active ingredient on the carrier. As a result of high dispersion, 50m ² equivalent to the catalyst produced by the impregnation method
It has been found that a higher catalytic activity can be obtained even with a small specific surface area of about / g. Note that a specific surface area of 100 m ² / g or more is required to obtain a predetermined performance in the conventional technique (Japanese Patent Laid-Open No. 2000-210561).

In the method for producing an exhaust gas treatment catalyst according to the present invention, titanium dioxide or titanium oxide type composite oxide is used as a carrier, and the active component is vanadia type complex oxide, or the active component is vanadium oxide-chromium oxide type complex oxide. In the manufacturing process of the exhaust gas treatment catalyst, which is a vanadium compound, vanadium pentoxide (V ₂ O ₅ ) or ammonium vanadate (NH ₄ V ₄ ) which is a pentavalent vanadium compound is used as a starting material of vanadium.
It is characterized in that the active ingredient is highly dispersed in the carrier by using a solution obtained by reducing the valence of vanadium from pentavalent to trivalent in an aqueous solution using O ₃ ) with a reducing agent.

In the method for producing the exhaust gas treatment catalyst, a dicarboxylic acid or a sulfite can be used as the reducing agent. Examples of the sulfite include ammonium sulfite ((NH ₄ ) ₂ SO ₃ ) or sodium sulfite (Na ₂ S).
O ₃ ) can be used. When oxalic acid is used as the reducing agent in the method for producing an exhaust gas treatment catalyst, the amount thereof is preferably such that the molar ratio of oxalic acid molecules to vanadium pentoxide molecules is 2 or more and 12 or less. When maleic acid is used as the reducing agent in the method for producing an exhaust gas treatment catalyst, the amount thereof is preferably such that the molar ratio of maleic acid molecules to vanadium pentoxide molecules is 5 or more and 13 or less.

The present inventors started conventional VCl ₃ by using an inexpensive pentavalent vanadium compound as a starting material and reducing the pentavalent vanadium compound into a trivalent material as an active ingredient material. Catalyst used as raw material
No. 210561) and a catalyst supporting V ₂ O ₅ and WO ₃ at a lower cost (Japanese Patent No. 263331).
It was clarified that a catalyst having a higher denitration activity can be produced at a lower temperature than that of No. 6).

The exhaust gas treatment catalyst according to the present invention uses, as a carrier, titanium dioxide or a titanium oxide-based composite oxide obtained by adding at least one of silicon oxide and tin oxide to titanium dioxide, and a vanadia-based composite oxide on the surface of the carrier. Or a vanadium oxide-chromium oxide composite oxide is supported as an active component. The amount of silicon oxide and tin oxide added is not particularly limited, but is preferably 20% by weight or less in total. Additions in excess of 20% by weight reduce the excellent carrier effect of titanium dioxide and are undesirable. The effect of the present invention can be exhibited even if the total amount of addition is 0% by weight, that is, the carrier is titanium dioxide alone.

The amount of the active ingredient carried is in the range of 3% by weight to 30% by weight, and the more preferable amount of the active ingredient is in the range of 5% to 15% by weight. If the amount of the active ingredient supported is less than 3% by weight, the denitration performance of the catalyst will be significantly deteriorated. Therefore, the lower limit of the amount of the active ingredient supported is 3% by weight. On the other hand, even if the supported amount of the active ingredient is more than 30% by weight, the denitrification rate can be improved only up to a certain value, and conversely, heat treatment causes grain growth and a decrease in specific surface area. The upper limit of the amount of the supported component is 30% by weight.

Such a catalyst is used in the presence of ammonia.
Ox can be selectively reduced and decomposed, and harmful substances such as dioxins, polychlorinated biphenyls, and chlorophenols in exhaust gas can be decomposed to be harmless.

The active ingredient is vanadium oxide or a vanadia-based complex oxide in which at least one oxide selected from the group of copper and molybdenum is added to vanadium oxide, or the active ingredient is vanadium-chromium oxide-based complex oxide. The relative value of the Cr mole number is 0.2 when the relative value of the total of the Cr mole number and the V mole number in the oxide is 1.
When the content is 0.4 or more and 0.4 or less, the main active ingredient is V ₇
It is preferably a Cr ₃ O ₂₂ or V ₄ Cr ₂ O ₁₃ composite oxide.

The reason why the vanadia-based composite oxide is used as the active component is that the addition of the second component to vanadia causes the vanadium to have a mixed valence state of pentavalent, tetravalent and trivalent, Since the oxidation-reduction cycle is smoothly repeated, the activity is improved, and the oxidation of the impurity gas such as SO ₂ contained in the exhaust gas is suppressed, and the deterioration of the catalyst due to the adhesion of side reaction products is reduced. Is.

Method for producing exhaust gas treatment catalyst according to the present invention
Are titanium compounds and small amounts of silicon compounds and tin compounds.
Prepare a first solution containing at least one and
% To 30% by weight required to support active ingredient
Of vanadium pentoxide (V ₂O_Five) Or vanadate
MONMONIUM (NH_FourVO₃) Containing a second solution
Then, using a reducing agent in the second solution, the valence of vanadium
Vanadium ion reduced from pentavalent to trivalent and necessary
Depending on at least one of copper ion and molybdenum ion
To prepare a third solution containing
Mix the third solution and add water or water-soluble alcohol.
And the titanium compound concentration in the solution is 0.05 mol.
/ L or more and 10 mol / L or less
The solution was prepared and then stirred to give a solution of 15N concentration.
Co-precipitated product is generated by neutralization with Lucari aqueous solution
The coprecipitated product is washed, then dried, and
Heat treatment in an oxidizing atmosphere at a temperature of 250 ° C to 550 ° C.
The valence of vanadium from 3 to 5
Valency control and active ingredient as carrier by coprecipitation method
It is characterized by high dispersion.

The present invention provides NO at low temperatures of 100 ° C to 300 ° C, preferably 150 ° C to 200 ° C.
Disclosed is a vanadia-based exhaust gas treatment catalyst capable of treating x and dioxins in one step, which uses an inexpensive pentavalent vanadium compound as a starting material for vanadium. Further, the present invention is a vanadia-based exhaust gas treatment catalyst capable of treating NOx and dioxins in one step at a low temperature of 100 ° C. or higher and 300 ° C. or lower, preferably 150 ° C. or higher and 200 ° C. or lower, as a vanadium starting material. Provided is a method for producing a vanadia-based exhaust gas treatment catalyst using an inexpensive pentavalent vanadium compound. Furthermore, the present invention is a vanadia-based exhaust gas treatment catalyst capable of treating NOx and dioxins in a single step at a low temperature of 100 ° C. or higher and 300 ° C. or lower, preferably 150 ° C. or higher and 200 ° C. or lower, and as a vanadium starting material. An exhaust gas treatment apparatus using a vanadia-based exhaust gas treatment catalyst using an inexpensive pentavalent vanadium compound is provided.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a denitration catalyst of the present invention uses titanium dioxide or a titanium oxide-based composite oxide as a carrier,
In the process of manufacturing an exhaust gas treatment catalyst in which the active component is a vanadia-based composite oxide or the active component is a vanadium oxide-chromium oxide-based composite oxide, the starting material of vanadium is 5
Valent vanadium compound vanadium pentoxide (V
₂ O ₅ ) or ammonium vanadate (NH ₄ VO ₃ ) and coprecipitating them with a solution obtained by reducing the valence of vanadium from pentavalent to trivalent in an aqueous solution using a reducing agent, The active ingredient can be highly dispersed in the carrier.

In the present invention, vanadium pentoxide (V ₂ O ₅ ) or ammonium vanadate (NH ₄ VO ₃ ) is reduced in an aqueous solution with a reducing agent at low cost and is easy to handle, and the valence of vanadium ion is reduced. These problems can be solved by using a solution in which is reduced from pentavalent to trivalent.
Dicarboxylic acid or sulfite can be used as the reducing agent. As the sulfite, for example, ammonium sulfite ((NH ₄ ) ₂ SO ₃ ) or sodium sulfite (Na ₂ SO ₃ ) can be used.

When oxalic acid is used as the reducing agent, the amount thereof is preferably such that the molar ratio of oxalic acid molecules to vanadium pentoxide molecules is 2 or more and 12 or less. When the molar ratio of the oxalic acid molecule to the vanadium pentoxide molecule is less than 2, vanadium is not sufficiently reduced, and when it is more than 12, no further effect is observed and excessive addition leads to cost increase. When maleic acid is used as the reducing agent, its amount is preferably such that the molar ratio of maleic acid molecules to vanadium pentoxide molecules is 5 or more and 13 or less. When the molar ratio of the maleic acid molecule to the vanadium pentoxide molecule is less than 5, vanadium is not sufficiently reduced, and when it is more than 13, no further effect is observed, and excessive addition causes cost increase.

The denitration catalyst of the present invention is a denitration catalyst which uses TiO ₂ as a carrier and carries 3 wt% to 30 wt% of a composite oxide described below as an active component, and has a specific surface area of 50 m ² / g or more. There is something. The carrier used in the present invention is TiO ₂ , and preferably TiO ₂ having an anatase structure. There are three types of crystal forms of TiO ₂ , namely, red pearl (rutile) type, anatase (anatase) type, and plate titanium (brookite) type. The rutile type is a high temperature stable type, and the anatase type is a low temperature stable type.

The active ingredient of the present invention is vanadium.
Oxidation of at least one of copper and molybdenum oxides
Complex vanadia-based oxide or vanadium and black
V which is a complex oxide of ROM_FourCr₂O₁₃Or V₇Cr₃
O_{twenty two}Is. In addition, vanadium and chromium composite oxide
Is V_FourCr₂O₁₃And V₇Cr₃O_{twenty two}Using a mixture with
You can Further, the active ingredient is the complex oxide and acid.
Coexistence with vanadium chloride or chromium oxide, for example
V₇Cr₃O_{twenty two}, V_FourCr₂O₁₃And V₂O_Five, VCrO _Four, C
r₂O₃It is also possible to use two-phase mixed oxides such as
it can.

Next, the method for producing the denitration catalyst of the present invention will be described. 3% by weight or more and 30% by weight in an aqueous solution containing one or more of titanium compounds, silicon compounds and tin compounds
A solution containing one or more trivalent vanadium ions prepared by the above-mentioned method necessary for supporting the following active ingredients, and copper ions and molybdenum ions, or a trivalent vanadium ion prepared by the above-mentioned method And a solution containing chromium ions are added, and then water or water and a water-soluble alcohol are added so that the concentration of the titanium compound in the solution is adjusted to 0.05 mol / liter or more and 10 mol / liter or less, Subsequently, while stirring, the solution is neutralized with an alkaline aqueous solution having a concentration of 15 N to form a precipitate, which is washed, dried, and heat-treated in an oxidizing atmosphere at a temperature of 250 ° C. or higher and 550 ° C. or lower. . As a result, 3% by weight or more of the active ingredient of the complex oxide is added to the carrier.
A denitration catalyst having a specific surface area of 0% by weight or less and a specific surface area of 50 m ² / g or more can be obtained.

In the present invention, by using a solution in which vanadium pentoxide is reduced from pentavalent to trivalent with a reducing agent, the above-mentioned difficulty of handling and high cost when VCl ₃ is used. While solving the above, it is possible to obtain a composite oxide catalyst in which an active component is highly dispersed in a carrier. In addition, V and C in the aqueous solution when preparing the precipitate
The required concentration of u, Mo, Cr metal ions can be calculated from the amount of the active ingredient loaded on the carrier. Furthermore, the titanium compound includes titanium chloride (TiCl ₄ ) and titanium sulfate (Ti (SO ₄ ).
₂ ) can be used.

Next, water is added to an aqueous solution containing titanium and vanadium, copper, molybdenum, and chromium so that the titanium ion concentration in the aqueous solution is 0.05 mol / liter or more 10
It is prepared so as to be not more than mol / liter, preferably not less than 0.05 mol / liter and not more than 2 mol / liter. When the concentration of titanium ions in the aqueous solution is higher than 10 mol / liter, the concentration is too high, and it becomes difficult to handle when the precipitate is formed, which makes handling difficult, which is not preferable. On the other hand, if the concentration is less than 0.05 mol / liter, the aqueous solution is so thin that a large amount of aqueous solution is required to make the catalyst, which is not practical and is not preferable.

Subsequently, this aqueous solution is neutralized with an alkaline aqueous solution having a concentration of 0.5 N or more and 15 N or less to form a precipitate. The concentration of alkaline aqueous solution is 0.5
If it is over the specified value, a uniform precipitate will be formed by neutralization. When the concentration of the alkaline aqueous solution is less than 0.5 N, the precipitate is uniformly formed, but a large amount of the alkaline aqueous solution needs to be added for neutralization, and the volume of the aqueous solution increases too much, which is not preferable because it is not practical. In addition, it is also possible to perform neutralization with ammonia gas instead of ammonia water.

When neutralized with aqueous ammonia to form a precipitate,
A large amount of NH ₄ Cl is produced, which is removed by washing. Finally, the NH ₄ Cl-free precipitate is dried and heat-treated at a temperature of 250 ° C. or higher and 550 ° C. or lower in an oxidizing atmosphere. As a result, the carrier has an active ingredient of the composite oxide of 3% by weight or more and 30% by weight or less and a specific surface area of 5%.
It is possible to obtain a denitration catalyst having a density of 0 m ² / g or more. When the heat treatment temperature is lower than 250 ° C., an amorphous oxide is included and a crystalline composite oxide cannot be obtained, which is not preferable. On the other hand, if the temperature is higher than 550 ° C., the oxide particles in the catalyst grow, the specific surface area becomes low, and the activity at low temperature decreases, which is not preferable. A more preferable heat treatment temperature is 30
It is 0 ° C or higher and 500 ° C or lower. The heat treatment time does not need to be particularly limited, but is sufficient for 1 hour to 5 hours.

The catalyst used for the treatment of exhaust gas may be in any shape integrally molded such as pellet, plate, cylinder, corrugated, honeycomb and the like. Naturally, it is preferable that the contact area between the catalyst and the exhaust gas is large, but depending on the packing density of the powdery catalyst, the flow back pressure of the exhaust gas increases, which is not preferable. As a countermeasure against this, it is particularly preferable to use, for example, a honeycomb-shaped molded body obtained by compressing the powder to a predetermined density without excessively reducing the specific surface area. When the bag filter contains a catalyst component and both dust removal and catalyst decomposition are performed, a method of coating the bag filter with the powder component of the catalyst can also be adopted. Further, as other usage forms, it is possible to use in a granular form, and to use the catalyst powder on the honeycomb by wash-coating.

Hereinafter, the present invention will be described in detail with reference to each experimental example, but the present invention is not limited to these experimental examples.

[0033]

Experimental Example (Experimental Example 1) V ₂ O ₅ was used as a vanadium raw material, oxalic acid was used as a reducing agent, and water was added so that the molar ratio of oxalic acid molecules to V ₂ O ₅ molecules was 1 or more and 15 or less. It was added and dissolved to prepare a vanadium-oxalic acid aqueous solution having a concentration of 0.25 mol / liter. The composition of the exhaust gas treatment catalyst in the aqueous titanium chloride solution at the time of completion was 90% by weight TiO ₂ -9% by weight V ₂ O ₅ -1% by weight Mo.
The vanadium-oxalic acid aqueous solution and the molybdenum chloride aqueous solution were added so as to obtain O ₃ , and water and 5% by volume of ethanol were added to adjust the titanium chloride concentration in the solution to 1 mol / liter, and the solution was adjusted with 15N ammonia water. The precipitate obtained by neutralization and coprecipitation was dried at 120 ° C. for 20 hours and further heat-treated at 400 ° C. for 2 hours in an oxidizing atmosphere to obtain a catalyst. Here, TiCl ₄ and MoCl ₆ become metal ions Ti ⁴⁺ and Mo ^{6+ in} an oxalic acid aqueous solution, and then become oxides TiO ₂ and MoO ₃ by heat treatment in an oxidizing atmosphere. The denitration rate was evaluated by filling the glass catalyst with the obtained catalyst and reacting with a constant composition of reaction gas (NO: 100 ppm, N
_{H 3: 100ppm, SO 2:} 10ppm, CO 2: 10
%, O ₂ : 10%, H ₂ O 20%, balance N ₂ ), space velocity 5
The flow was carried out at 000 h ^-1 and continued at 150 ° C and 130 ° C for 100 hours. The NO concentration was measured using a NOx meter. Vanadium material of the catalyst, vanadium - a molar ratio of oxalic acid molecules to V ₂ O ₅ molecules of oxalic acid aqueous solution (referred to in Table 1 is "reducing agent / V ₂ O ₅ molar ratio"), the specific surface area, 0.99 ° C. and 130 Table 1 shows the denitration rate at ° C. Sample Nos. 1 and 5 had a low denitrification rate and had a reducing agent / V ₂
It was inferior to the case where the O ₅ molar ratio was 2 to 10.

(Conventional Example 1) R1 shown in Table 1 is NH ₄ V
The data of a catalyst having the same composition is additionally shown by a conventional impregnation method using O ₃ as a raw material. (Conventional Example 2) R2 shown in Table 1 is VCl as a vanadia raw material.
₃ The data of the catalyst of the same composition is added using the aqueous solution.

(Experimental Example 2) V ₂ O ₅ was used as a vanadium raw material, maleic acid was used as a reducing agent, and added so that the molar ratio of maleic acid molecules to V ₂ O ₅ molecules was 3 or more and 15 or less. It was dissolved in water to prepare an aqueous vanadium-maleic acid solution having a concentration of 0.25 mol / liter. A catalyst was prepared and denitration activity was evaluated in the same manner as in Experimental Example 1 except that this solution was used as a vanadium raw material. Vanadia raw material of catalyst, V of vanadium-maleic acid aqueous solution
Molar ratio of maleic acid molecule to ₂ O ₅ molecule (referred to as “reducing agent / V ₂ O ₅ molar ratio” in Table 1), specific surface area, 1
Table 1 shows the NOx removal rates at 50 ° C and 130 ° C. Sample Nos. 6 and 10 had a low denitration rate and were inferior to the cases where the reducing agent / V ₂ O ₅ molar ratio was 6 to 12.

(Experimental Example 3) V ₂ O ₅ or NH ₄ VO ₃ was used as the vanadium raw material, ammonium sulfite or sodium sulfite was used as the reducing agent, and the molar ratio of the reducing agent molecule to the V ₂ O ₅ molecule (see Table 1). Is added so that the "reducing agent / V ₂ O ₅ molar ratio" is 2 and dissolved in water to prepare a vanadium-sulfurous acid aqueous solution having a concentration of 0.25 mol / liter. A catalyst was prepared and denitration activity was evaluated in the same manner as in Experimental Example 1 except that this solution was used as a vanadium raw material. Vanadium material of the catalyst, vanadium - a molar ratio of sulfite molecules to V ₂ O ₅ molecules of sulfite aqueous solution (referred to in Table 1 is "reducing agent / V ₂ O ₅ molar ratio"), the specific surface area, at 0.99 ° C. and 130 ° C. Denitration rate of
Shown in 1.

[0037]

[Table 1]

[0038] The oxalic acid (Experiment _{4) V 2 O 5, V} 2 O 5
A molar ratio of oxalic acid molecules to molecules is added so as to be 5 and dissolved in water to prepare an aqueous vanadium-oxalic acid solution having a concentration of 0.25 mol / liter. Amount of ethyl silicate, SnC
l ₂ , an aqueous solution of hydrochloric acid containing an additive of Na ₂ SiO ₃ ,
The vanadium-oxalic acid aqueous solution having a composition ratio necessary for preparing a composite oxide, MoCl ₅ , CuCl _{2 and the} like are added in an amount necessary to carry a predetermined concentration, and a precipitate is prepared under the same conditions as in Experimental Example 1, Dried. More than 250 ℃ 550 ℃
Then, heat treatment was performed for 2 hours in an oxidizing atmosphere to obtain a catalyst as shown in Table 2. The denitration activity was measured under the same conditions as in Experimental Example 1. Table 2 shows the composition of the catalyst, the heat treatment temperature, the specific surface area, and the denitration rate at 150 ° C and 130 ° C.

(Experimental Example 5) The catalyst was prepared and the denitration activity was evaluated by the same method as in Experimental Example 4 except that titanium sulfate was used as the titanium raw material. The composition of the catalyst, the heat treatment temperature, the specific surface area, and the denitration rate at 150 ° C. and 130 ° C. are shown in S of Table 2.
1 and S2.

[0040]

[Table 2]

[0041] (Experimental Example 6) V ₂ O ₅ was added to oxalic acid so that the molar ratio of oxalic acid molecules to V ₂ O ₅ molecules is 5, the concentration of 0.25 mol / liter were dissolved in water Of vanadium-oxalic acid aqueous solution, and when the total number of moles of Cr and V in the titanium chloride aqueous solution is relatively set to 1, the number of moles of Cr (“Cr / (Cr + V)” in Table 3)
The above-mentioned aqueous solution of vanadium-oxalic acid and Cr (NO ₃ ) ₃ were added so that the value of () is 0.15 or more and 0.5 or less, and a precipitate was prepared and dried under the same conditions as in Experimental Example 1. 25 more
Heat treatment was performed at 0 ° C. or higher and 550 ° C. or lower for 2 hours in an oxidizing atmosphere to obtain a catalyst as shown in Table 3. The denitration activity was measured under the same conditions as in Experimental Example 1. Table 3 shows the composition of the catalyst, the Cr / (Cr + V) molar ratio, the heat treatment temperature, the specific surface area, and the denitration rate at 150 ° C. and 130 ° C.

[0042] (Experimental Example 7) V ₂ O ₅ in the oxalic acid was added so that the molar ratio of oxalic acid molecules to V ₂ O ₅ molecules is 5, was dissolved in water concentration of 0.25 mol / l An aqueous solution of vanadium-oxalic acid is prepared, and an aqueous solution of titanium chloride and one-twentieth the amount of ethyl silicate, SnCl ₂ ,
When the total of the number of moles of Cr and the number of moles of V is relatively 1 in an acidic aqueous hydrochloric acid solution containing an additive of Na ₂ SiO _3, the number of moles of Cr (referred to as “Cr / (Cr + V)” in Table 3). ) Was 0.3, the vanadium-oxalic acid aqueous solution and Cr (NO ₃ ) ₃ were added, and a precipitate was prepared and dried under the same conditions as in Experimental Example 1. Further, heat treatment was performed at 400 ° C. for 2 hours in an oxidizing atmosphere to obtain a catalyst as shown in Table 3. The denitration activity was measured under the same conditions as in Experimental Example 1. Catalyst composition, Cr /
(Cr + V) molar ratio, heat treatment temperature, specific surface area, 150 ° C
And the denitration rate at 130 ° C. are shown in Table 3.

(Experimental Example 8) The catalyst was prepared and the denitration activity was evaluated in the same manner as in Experimental Example 6 except that titanium sulfate was used as the titanium raw material. Catalyst composition, Cr mole number and V
When the total number of moles is relatively set to 1, the number of moles of Cr (in Table 3, referred to as “Cr / (Cr + V)”), heat treatment temperature, specific surface area, denitration rate at 150 ° C. and 130 ° C. It shows in S3 of Table 3.

[0044]

[Table 3]

(Experimental Example 9) In the same manner as in Experimental Example 1, the denitration rate of catalysts 3, 17, 23, 24, 29 and 37 was set to 1
It was measured in the range of 30 ° C or higher and 250 ° C or lower. The reaction time is 200 hours each. The results are shown in Table 4. Both catalysts have a higher denitrification rate than R1 prepared by the impregnation method,
A denitrification rate equivalent to that of R2 using ₃ was exhibited. Sample number 2
For Nos. 7 and 32, the denitration rate is low, and Cr / (Cr + V)
It was inferior to the case where the molar ratio was 0.2 to 0.4.

[0046]

[Table 4]

(Experimental Example 10) Orthochlorophenol was used as an example of a halogenated aromatic compound, and its decomposition rate by a catalyst was tested. Orthochlorophenol was passed through a microreactor containing a granular catalyst at a space velocity of 5000 h ^{−1 using} air as a carrier gas, and the resulting gas was analyzed by gas chromatography. As a result, as shown in Table 5, the catalysts 3, 23, and 29 all had an initial performance of the decomposition rate at 150 ° C. of 80% or more, and had a lower decomposition activity at a lower temperature than the conventional example R1 by the conventional impregnation method. high.

[0048]

[Table 5]

(Experimental Example 11) 150 in a refuse incinerator
Part of the exhaust gas after passing through the dust remover at ℃,
Exhaust gas treatment filled with the catalyst of the present invention formed into a honeycomb shape
Nitrogen oxide at the inlet and outlet of the processing equipment.
The concentrations of substances and dioxins were measured. NO at the device entrance
The concentration is 110ppm, the concentration of dioxins is 1.2n
g-TEQ / Nm³And the space velocity is 9000h^-1so
is there. NH added as a reducing agent for NO₃The amount is in the exhaust gas
Is equivalent to the NO amount of. Denitration rate at each temperature and outlet
Table 6 shows the dioxin concentration. Catalysts 3 and 2 of the present invention
By using 3 and 29, desorption is possible even in the low temperature region of 150 ° C.
The glass content is higher than R1 produced by the impregnation method and is 90% or less.
It was on top. Dioxin concentration is low at 150 ℃
Even if there is 0.1 ng-TEQ / Nm ³Is below
The exhaust gas temperature below 200 ° C, which is lower than the conventional exhaust gas temperature
Can also decompose nitrogen oxides and halogenated aromatic compounds simultaneously
It was Act on Dioxin Emissions (Fiscal 1998)
The emission concentration is 0.1 ngT according to the Ministry of Health and Welfare emission control value)
EQ / Nm³Although enacted below, the catalyst of the present invention
It becomes possible to meet this standard by applying
ing.

[0050]

[Table 6]

FIG. 1 is an example of a schematic view of an exhaust gas treating apparatus using the catalyst of the present invention. As shown in FIG. 1, the exhaust gas treatment device includes a dust removal device 2 for removing soot and dust in exhaust gas 1 discharged from various incinerators such as an urban refuse incinerator, an industrial waste incinerator, and a sludge incinerator; It is composed of a catalyst device 3 having the exhaust gas treatment catalyst 4 for removing nitrogen oxides and dioxins of substances, and a chimney 5 for discharging the exhaust gas from which harmful substances are decomposed and removed to the outside. The dust remover 2 can collect soot dust and solid dioxins in the exhaust gas 1 to prevent deterioration of the catalyst device 3 and clogging of the catalyst 4. The ammonia injection nozzle 6 is installed to supply the ammonia necessary for causing the denitration reaction in the catalyst device 3.

[0052]

The catalyst of the present invention is prepared by a coprecipitation method using an inexpensive pentavalent vanadium compound as a starting material and a trivalent vanadium solution obtained by reduction as a starting material.
The active ingredient can be dispersed more highly than the catalyst prepared by the conventional impregnation method, and the cost can be reduced as compared with the catalyst prepared by using the conventional VCl ₃ as the starting material. According to the present invention, by providing an exhaust gas treatment catalyst having a higher decomposition treatment activity at a lower temperature than conventional catalysts for exhaust gas containing harmful substances such as nitrogen oxides and halogenated aromatic compounds,
It can contribute to environmental purification and has high industrial utility value. Particularly in the treatment of exhaust gas from a refuse incinerator, etc., after passing the exhaust gas through the dust remover in a low temperature range of about 150 ° C., harmful substances can be decomposed without reheating to 200 ° C. or higher. Miniaturization and cost reduction are possible.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an exhaust gas treatment device.

[Explanation of symbols]

1 exhaust gas 2 Dust remover 3 catalyst equipment 4 Exhaust gas treatment catalyst 5 chimney 6 Ammonia injection nozzle

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01J 23/847 B01J 37/16 37/03 B01D 53/36 102D 37/14 G 37/16 B01J 23/84 301A (72 ) Inventor Akihiro Sawada 1-8-1 Koura, Kanazawa-ku, Yokohama-shi, Kanagawa Mitsubishi Heavy Industries, Ltd. Basic Technology Research Institute (72) Inventor, Yuichiro Murakami 12 Nishiki-cho, Naka-ku, Yokohama-shi, Kanagawa F, Ryohi Engineering Co., Ltd. Terms (reference) 4D048 AA06 AA11 AB02 AB03 BA06X BA07X BA13X BA21X BA23X BA25X BA26X BA35X BA42X BB01 BB02 CD03 CD08 4G069 AA03 AA08 BA01B BACA BC08BC08BC08BC08BC58BC58BC58BC58BC58B59B59B59B59B59B59B59B59B59B59B59B59B59B59B59B59B59B59B59BBCBBCBBC59B59B59B59B59B59B59C02B01B CA11 CA13 CA19 EA02Y EA19 EC02Y FA01 FA02 FB09 FB40 FB45 FB46 FC04 FC07 FC08

Claims (11)

[Claims] 1. A step of preparing a first solution containing a titanium compound, or at least one of a silicon compound and a tin compound and a titanium compound, and a step of preparing a second solution containing a pentavalent vanadium compound, Reducing the valence of at least part of vanadium in the second solution from pentavalent to trivalent to obtain a third solution containing a trivalent vanadium compound, the first solution and the first solution A step of coprecipitating by mixing with the solution of three and neutralizing with an alkali; and a step of washing the coprecipitated product and then oxidizing it.
Of a valent vanadium hydroxide to a pentavalent vanadium oxide. 2. The method for producing an exhaust gas treatment catalyst according to claim 1, wherein the pentavalent vanadium compound is V ₂ O ₅ or NH ₄ VO ₃ . 3. The method for producing an exhaust gas treatment catalyst according to claim 1, wherein the reduction is due to the action of a dicarboxylic acid. 4. The dicarboxylic acid is oxalic acid, the pentavalent vanadium compound is V ₂ O ₅ , and the number of moles of oxalic acid molecules is at least twice the number of moles of V ₂ O ₅ molecules. The method for producing an exhaust gas treatment catalyst according to claim 3, wherein the amount is not more than double. 5. The dicarboxylic acid is maleic acid, the pentavalent vanadium compound is V ₂ O ₅ , and the number of moles of maleic acid molecules is 5 times or more the number of moles of V ₂ O ₅ molecules.
It is 3 times or less, The manufacturing method of the exhaust gas treatment catalyst according to claim 3, which is characterized in that. 6. The method for producing an exhaust gas treatment catalyst according to claim 3, wherein the reduction is due to the action of sulfite. 7. The method for producing an exhaust gas treatment catalyst according to claim 1, wherein the oxidation is carried out in an oxidizing atmosphere at 250 ° C. or higher and 550 ° C. or lower, preferably 300 ° C. or higher and 500 ° C. or lower. 8. A carrier comprising titanium dioxide or a titanium oxide-based complex oxide and an active ingredient comprising vanadia or a vanadia-based complex oxide, wherein the carrier contains 3% by weight or more and 30% by weight or less of the active ingredient. An exhaust gas treatment catalyst carried, which is produced by the production method according to any one of claims 1 to 7. 9. The exhaust gas treatment catalyst according to claim 8, wherein the titanium oxide-based composite oxide is a titanium oxide-based composite oxide obtained by adding at least one of silicon oxide and tin oxide to titanium dioxide. . 10. The exhaust gas treatment according to claim 8, wherein the vanadia-based composite oxide is a vanadia-based composite oxide in which at least one oxide selected from copper and molybdenum is added to vanadium oxide. catalyst. 11. A dust remover for removing soot and dust in exhaust gas,
An exhaust gas treatment catalyst produced by the production method according to any one of claims 1 to 7, and an exhaust gas treatment catalyst which is provided on the downstream side of the dust removing device and has the catalyst inside so that the catalyst can come into contact with the exhaust gas. And an exhaust gas treatment device.