JP4680748B2 - Exhaust gas treatment catalyst and exhaust gas treatment method - Google Patents

Description

  The present invention relates to an exhaust gas treatment catalyst and an exhaust gas treatment method, and more particularly to an exhaust gas treatment catalyst suitable for decomposing and removing harmful substances such as nitrogen oxides and dioxins contained in the exhaust gas, and an exhaust gas using the catalyst. It relates to the processing method.

  Many catalysts and treatment methods have already been proposed in order to decompose and remove harmful substances such as nitrogen oxides and dioxins contained in exhaust gas.

  For example, (a) a sulfur-containing composite oxide containing sulfur and titanium and silicon, or titanium, zirconium and silicon, A nitrogen oxide removal catalyst containing an oxide of at least one element selected from b) vanadium oxide, (c) tungsten, molybdenum, tin and cerium has been proposed (see, for example, Patent Document 1).

In addition, focusing on the specific surface area and solid acid content of the catalyst, the exhaust gas treatment catalyst, which specifically identifies these physical properties and catalyst composition, specifically, the oxidation of vanadium, tungsten, molybdenum, etc. on a carrier such as titanium-silicon composite oxide. In addition, a catalyst having a specific surface area of 10 m ² / g or more and a solid acid amount of 0.36 mmol / g or more is effective in removing harmful substances such as nitrogen oxides and dioxins contained in exhaust gas. It has been proposed (see, for example, Patent Document 2).

However, conventional exhaust gas treatment catalysts are still not fully satisfactory in terms of their performance, and catalysts for more efficiently removing harmful substances such as nitrogen oxides and dioxins contained in exhaust gas, such as nitrogen In the case of oxides, development of exhaust gas treatment catalysts having higher denitration efficiency is desired.
Japanese Patent Publication No.62-14339 Japanese Patent No. 3457717

  An object of the present invention is to provide an exhaust gas treatment catalyst suitable for removing harmful substances such as nitrogen oxides and dioxins contained in exhaust gas, and a method for efficiently treating exhaust gas using this catalyst. is there.

  The inventors of the present invention have made extensive studies in order to achieve the above object, and have obtained the following knowledge. That is, the surface of the solid catalyst generally has a Bronsted acid point that donates protons and a Lewis acid point that accepts electron pairs. For example, in the case of denitration treatment, both Bronsted acid point and Lewis acid point are active in denitration catalyst activity. It was found that the highest denitration efficiency was obtained especially when the abundance ratio between Bronsted acid point and Lewis acid point was in a specific range.

  Further, in the exhaust gas treatment catalyst containing a titanium-based oxide, the amount of solid acid having an acid strength of pKa ≦ + 3.3 is 0.3 mmol / g or more as the titanium-based oxide, and further the solid acid point is protonated. The ratio (B / L) between the Bronsted acid amount (B) and the Lewis acid amount (L) is 0/1 to 1/1 /. It was found that a catalyst having excellent decomposing performance of harmful substances can be obtained by using those having 1.

  The present invention has been completed based on the above findings and is as follows.

(1) An exhaust gas treatment catalyst for decomposing and removing harmful substances in exhaust gas containing a titanium-based oxide and other catalytically active components, the ratio of Bronsted acid (B) to Lewis acid (L) (B / L) Ri 0/10/1 by weight near, the titanium-containing oxide is at least one selected and titanium, aluminum, silicon, chromium, zirconium, from the group consisting of molybdenum and tungsten When the ratio (B / L) of the titanium-based oxide is 0/1 to 1/1, the amount of solid acid with pKa ≦ + 3.3 is 0. exhaust gas treatment catalyst according to claim der Rukoto than 3 mmol / g.

  (2) The catalyst according to (1), wherein the ratio is 0/1 to 9/1.

( 3 ) The catalyst according to (1) or (2) , wherein the titanium-based oxide is a composite oxide of titanium and at least one element selected from the group consisting of aluminum, silicon, chromium, and zirconium. .

( 4 ) The titanium-based oxide is any one of the above (1) to (3), which is a composite oxide of titanium and at least one element selected from the group consisting of aluminum, silicon, and zirconium. The catalyst described.

( 5 ) The catalyst according to any one of (1) to (4), wherein the other catalytically active component is at least one element selected from the group consisting of vanadium, tungsten and molybdenum or a compound thereof. .

( 6 ) The titanium content in the titanium-based composite oxide is 40 to 95% by mass, and the other catalytically active component is 60 to 5% by mass (however, the total of these is 100% by mass). The catalyst according to any one of (1) to (5) .

( 7 ) The catalyst according to any one of (1) to (6), wherein the content of the titanium-based oxide is 75 to 99.9% by mass based on the total amount of the catalyst .

( 8 ) The catalyst according to any one of (1) to (7), further containing sulfur.

( 9 ) The catalyst according to any one of (1) to (8), wherein the solid acid amount satisfying pKa ≦ + 3.3 is 0.3 to 0.8 mmol / g.

( 10 ) The catalyst according to (8) or (9) , wherein the sulfur content is 0.01 to 3 mass% with respect to the total mass of the catalyst .

( 11 ) An acid solution containing a titanium compound is added with an aqueous ammonia solution containing at least one element selected from the group consisting of aluminum, silicon, chromium, zirconium, molybdenum and tungsten to produce a precipitate. Any one of the above (1) to (10), wherein the titanium-based composite oxide obtained through a process in which the time from the start to the completion of addition of the total amount is 40 minutes or more is used. The manufacturing method of the catalyst as described in one .

( 12 ) When an acidic solution containing a titanium compound is added to an aqueous ammonia solution containing at least one element selected from the group consisting of aluminum, silicon, chromium, zirconium, molybdenum and tungsten, a precipitate is generated. Any one of the above (1) to (10), wherein the titanium-based composite oxide obtained through the process of starting from the start and finishing the addition of the total amount of 40 minutes or more is used. The manufacturing method of the catalyst as described in one .

( 13 ) Addition of an aqueous ammonia solution to an acidic solution containing at least one element selected from the group consisting of aluminum, silicon, chromium, zirconium, molybdenum, and tungsten and a titanium compound, and starting the addition Any one of the above (1) to (10), wherein the titanium-based composite oxide obtained through a step of 40 minutes or more from the completion of the addition of the total amount is used. A process for producing the catalyst as described in 1. above.

( 14 ) An addition is started when an acidic solution containing at least one element selected from the group consisting of aluminum, silicon, chromium, zirconium, molybdenum and tungsten and a titanium compound is added to an aqueous ammonia solution to form a precipitate. Any one of the above (1) to (10), wherein the titanium-based composite oxide obtained through a step of 40 minutes or more from the completion of the addition of the total amount is used. A process for producing the catalyst as described in 1. above.

( 15 ) An exhaust gas treatment method comprising contacting an exhaust gas containing a harmful substance with the exhaust gas treatment catalyst according to any one of (1) to (10) to decompose and remove the harmful substance.

  By using the catalyst of the present invention, harmful substances such as nitrogen oxides and dioxins can be efficiently decomposed and removed.

  The “hazardous substance” in the present invention means organic halogen compounds such as nitrogen oxides and chlorinated dioxins, brominated dioxins, polychlorinated biphenyls, chlorobenzenes, chlorophenol and chlorotoluene. The exhaust gas treatment when the harmful substance is nitrogen oxide is a so-called denitration treatment, in which the nitrogen oxide is reductively decomposed using a reducing agent such as ammonia or urea. The exhaust gas treatment catalyst of the present invention is particularly preferably used for reductive decomposition (denitration treatment) of nitrogen oxides.

An exhaust gas treatment catalyst according to the present invention is an exhaust gas treatment catalyst for decomposing and removing harmful substances in exhaust gas containing titanium-based oxides and other catalytically active components, and includes Bronsted acid (B) and Lewis acid. (L) ratio (B / L) in the range near 0 / 1-10 / 1 and is, the titanium-based oxide, and titanium, aluminum, silicon, chromium, zirconium, from the group consisting of molybdenum and tungsten When it is a complex oxide with at least one selected element and the ratio (B / L) of the titanium-based oxide is 0/1 to 1/1, pKa ≦ + 3.3. weight solid acid is the catalyst for exhaust gas treatment, characterized in der Rukoto than 0.3 mmol / g.

  The ratio B / L is 0/1 to 10/1, preferably 0/1 to 9/1, more preferably 0.1 / 1 to 8/1, most preferably 0.1 / 1 to 1. It is in the range of 7/1. When the ratio (B / L) is less than 0/1 or exceeds 10/1, the treatment performance of the catalyst is lowered.

  The “titanium-based oxide” in the present invention means titanium oxide and composite oxides of titanium and other metal elements. As the titanium oxide, anatase type titanium, rutile type titanium or a mixture thereof is used. A representative example of the composite oxide is selected from the group consisting of titanium (Ti) and aluminum (Al), silicon (Si), chromium (Cr), zirconium (Zr), molybdenum (Mo) and tungsten (W). A composite oxide with at least one element can be given. A mixture of titanium oxide and titanium-based composite oxide may be used.

  Among the titanium-based composite oxides, titanium (Ti), aluminum (Al), silicon (Si), chromium (Cr) and zirconium (Zr), particularly aluminum (Al), silicon (Si) and zirconium (Zr). A composite oxide with at least one element selected from (1) is preferably used. This complex oxide may be a binary complex oxide such as a Ti—Si complex oxide or a ternary complex oxide such as a Ti—Si—Zr complex oxide. Note that “composite oxide” does not show an obvious intrinsic peak attributed to a substance other than titanium oxide in an X-ray diffraction pattern. For titanium oxide, an intrinsic peak attributed to anatase-type titanium oxide is not observed. It means not showing or showing a broader diffraction peak than that of anatase-type titanium oxide.

  In addition, about molybdenum and tungsten, respectively, even if the total amount constitutes a titanium-based composite oxide together with titanium, or the total amount exists in the catalyst in a form other than the titanium-based composite oxide, or A part thereof may constitute a titanium-based composite oxide, and the remainder may be included in the catalyst in other forms.

  A typical example of the composition of the exhaust gas treatment catalyst of the present invention is as follows.

(1) Ti—Si composite oxide + (V, W and / or Mo),
(2) Ti—Al composite oxide + (V, W and / or Mo),
(3) Ti—Zr composite oxide + (V, W and / or Mo),
(4) Ti-W composite oxide + (V, W and / or Mo),
(5) Ti—Si—Zr composite oxide + (V, W and / or Mo),
(6) Ti-Si-Mo composite oxide + (V and / or W),
(7) Ti—Si—Mo composite oxide + (V, W and / or Mo),
(8) Ti-Si-W composite oxide + (V and / or Mo),
(9) Ti—Si—W composite oxide + (V, W and / or Mo),
(10) Ti oxide + (V, W and / or Mo).

The Bronsted acid amount (B) and Lewis acid amount (L) can be accurately measured by infrared spectroscopy (FT-IR) using pyridine as a probe. Pyridine has an infrared absorption band derived from in-plane vibration of the pyridine ring in the region of 1700 to 1400 cm −1, and whether pyridine has a hydrogen bond (PyH), a coordinate bond (PyL), or a proton sum ( PyB), the absorption band is remarkably different. Among them, is due Pyl (1450 cm ^-1 vicinity) and PyB (1540 cm ^-1 vicinity) 19b vibration modes of the respective absorption band of pyridine adsorbed on Lewis acid sites and Bronsted acid sites, Pyl the peak area of PyB By determining the peak area ratio (B / L) divided by the peak area, the ratio of the Bronsted acid amount to the Lewis acid amount can be determined.

  In the present invention, “Bronsted acid amount (B)” and “Lewis acid amount (L)” are peaks derived from Bronsted acid points measured by the following FT-IR analysis method using pyridine as a probe, respectively. It means the peak area derived from the area and Lewis acid point.

<FT-IR analysis method>
As the FT-IR apparatus, PROTEGE 460 manufactured by Nicorey is used, and a diffuse reflection type in situ cell is attached to the apparatus and measured. 0.02 g of the sample pulverized to 100 mesh or less is placed on the sample stage of the diffuse reflection type cell as powder without being diluted with KBr or the like, and helium gas containing 5% by volume of oxygen (O2) is flowed at a flow rate of 40 ml / min. Heat to 400 ° C. and hold at 400 ° C. for 60 minutes. Thereafter, the sample is cooled to 150 ° C. while flowing helium gas, and 10 μL (microliter) of pyridine is injected at 150 ° C. to allow the sample to absorb pyridine. Thereafter, helium gas is allowed to flow at 150 ° C. for 120 minutes to remove pyridine physically adsorbed on the sample, and then allowed to cool to room temperature, and an FT-IR spectrum is measured with a resolution of 4 cm ⁻¹ . The Bronsted acid amount (B) is obtained by integrating the range of 1515 to 1565 cm ⁻¹ of the obtained FT-IR spectrum, and the Lewis acid amount (L) is obtained by integrating the range of 1425 to 1465 cm ^−1. .

  The ratio (B / L) between the Bronsted acid amount (B) and the Lewis acid amount (L) is the Bronsted acid amount (B) and Lewis acid amount (L) determined by the FT-IR analysis method. Can be easily obtained.

  There is no restriction | limiting in particular in the composition of the catalyst for exhaust gas treatment of this invention, As long as the said ratio (B / L) exists in the range of 0/1-10/1, any may be sufficient. Of these, those containing a titanium-based oxide and at least one element selected from vanadium (V), tungsten (W), and molybdenum (Mo) are preferable.

  When the ratio (B / L) is 0/1 to 1/1, the “titanium-based oxide” used in the present invention has a solid acid amount of pKa ≦ + 3.3 of 0.3 mmol / g or more. , Preferably 0.3 to 0.8 mmol / g, more preferably 0.35 to 0.7 mmol / g, and still more preferably 0.4 to 0.6 mmol / g. When the amount of solid acid with pKa ≦ + 3.3 is less than 0.3 mmol / g, the adsorption of harmful substances on the catalyst surface is lowered, and as a result, the hazardous substance decomposition performance of the catalyst is lowered. The solid acid amount is considered to be the total acid amount of Bronsted acid and Lewis acid on the surface of the titanium-based oxide.

  The “solid acid amount satisfying pKa ≦ + 3.3” in the present invention is measured by the following method.

<Measurement method of solid acid amount>
Using p-dimethylaminoazobenzene as an indicator of pKa = + 3.3, it is determined according to the n-butylamine titration method. 0.2 g of a powder sample dried at 120 ° C. for 3 hours or more is weighed with a precision balance, put into a test tube, and about 20 ml of benzene is added thereto. When a few drops of a solution of the above indicator dissolved in benzene are added thereto, the stopper is capped and shaken well, the indicator becomes red, which is the acidic color of the indicator. To this, 0.13 mmol / ml of benzene solution of n-butylamine was added with microburette, and the point at which the sample turned yellow, which is the basic color of the indicator, was taken as the end point of titration. The solid acid amount (mmol / g) is calculated according to the following formula.

  In the case of the solid acid amount, the “titanium-based oxide” used in the present invention has a ratio (B / L) of the Bronsted acid amount (B) to the Lewis acid amount (L) of 0/1 to 1/1, It is preferably in the range of 0.1 / 1 to 1/1, more preferably 0.1 / 1 to 0.8 / 1. When the ratio (B / L) exceeds 1/1, the exhaust gas treatment catalyst obtained using this titanium-based oxide has a low hazardous substance decomposition performance, which is not preferable.

  The solid acid amount of pKa ≦ + 3.3 of the present invention is 0.3 mmol / g or more, and the ratio (B / L) between the Bronsted acid amount and the Lewis acid amount is in the range of 0/1 to 1/1. The titanium-based oxide can be prepared by various methods. As the titanium-based oxide, a titanium-based composite oxide of titanium and at least one element selected from aluminum, silicon, and zirconium is taken as an example. The preparation method will be described below.

  The starting material is not particularly limited, and a compound generally used for preparing a composite oxide containing titanium can be used.

  As the titanium source, for example, inorganic titanium compounds such as titanium tetrachloride and titanium sulfate, and organic titanium compounds such as titanium oxalate and tetraisopropyl titanate can be appropriately selected and used.

  As an aluminum source, for example, an inorganic aluminum compound such as aluminum nitrate and aluminum sulfate, and an organic aluminum compound such as aluminum acetate can be appropriately selected and used.

  As the silicon source, for example, an inorganic silicon compound such as colloidal silica, water glass, fine particle silicon, silicon tetrachloride and silica gel, and an organic silicon compound such as tetraethyl silicate can be appropriately selected and used.

  As the zirconium source, for example, inorganic zirconium compounds such as zirconium chloride and zirconium sulfate, and organic zirconium compounds such as zirconium oxalate can be appropriately selected and used.

  When the titanium-based composite oxide of the present invention is, for example, a titanium-silicon composite oxide, a solution (A) is prepared by dispersing a silicon compound such as colloidal silica in an aqueous ammonia solution, and the solution (A) is stirred. The time from the start of dropping a solution of a titanium compound such as titanyl sulfate until the pH of the mixed solution reaches 8 is 40 minutes or more, preferably 40 to 1440 minutes, more preferably 60 to 1080 minutes, Preferably, it is added dropwise so as to be 90 to 720 minutes, and the obtained slurry is filtered, further dried, and then fired at a temperature of 300 to 600 ° C. In the case of a titanium-silicon-aluminum composite oxide, a solution of an aluminum compound is dropped into the solution (A) in addition to the titanium compound. The time until it becomes 8 is 40 minutes or more, preferably 40 to 1440 minutes, more preferably 60 to 1080 minutes, and still more preferably 90 to 720 minutes, and the resulting slurry is filtered and further dried Then, it may be fired at a temperature of 300 to 600 ° C.

  Even when an aqueous ammonia solution is dropped into a mixed solution of a titanium compound and a silicon compound or a solution of a titanium compound is dropped, the time from the start of dropping until the pH of the mixed solution reaches 8 is 40. If it is dropped under such a condition that it is less than 5 minutes, a titanium-based oxide having the desired acidity cannot be obtained, and sufficient exhaust gas treatment performance may not be obtained.

The content of titanium in the titanium-based composite oxide (titanium-containing oxide) is the total mass of the titanium, silicon, chromium, and at least one element selected from Mo Ribuden and tungsten, 40 to 95 wt% , Preferably 50 to 95% by mass, particularly preferably 60 to 95% by mass. The content of other elements (silicon, chromium, molybdenum or tungsten) differs depending on whether it is a binary complex oxide or a ternary complex oxide. In the former case, the content of other elements is different from that of titanium. 5 to 60% by mass, preferably 5 to 50% by mass, more preferably 5 to 40% by mass with respect to the total mass with other elements. In the latter case, the content of other elements is titanium and other elements. 1 to 60% by mass, preferably 5 to 50% by mass, and more preferably 5 to 40% by mass with respect to the total mass with the above elements. (However, the total of titanium and other elements (silicon, chromium, molybdenum or tungsten) is 100 % by mass.)
The content of the titanium-based oxide in the exhaust gas treatment catalyst of the present invention is 75 to 99.9% by mass, preferably 80 to 99.5% by mass, more preferably 85 to 99% by mass based on the total mass of the catalyst. %. When the content of the titanium-based oxide exceeds 99.9% by mass, the content of at least one element selected from vanadium, tungsten, and molybdenum is excessively decreased, so that the catalyst performance is deteriorated, and less than 75% by mass. As a result, the content of elements such as vanadium is increased, and an improvement in catalyst performance commensurate with the content is not recognized.

  The shape of the titanium-based oxide is not particularly limited, and the titanium-based oxide obtained by the preparation method as described above may be used as it is, or may be a plate shape, a corrugated plate shape, a net shape, a honeycomb shape, a cylindrical shape, a spherical shape. Alternatively, it may be used by appropriately forming it into a cylindrical shape, a pellet shape or the like. In general, the shape of the titanium-based oxide is determined in consideration of the shape of the finished catalyst.

  The exhaust gas treatment catalyst having a ratio (B / L) between the Bronsted acid amount (B) and the Lewis acid amount (L) of the present invention in the range of 1/1 to 10/1 was prepared as described above. It is obtained by using a titanium-based composite oxide and adding at least one element selected from vanadium, tungsten and molybdenum to this. For example, a precipitation method (coprecipitation method), a hydrolysis method, a sol-gel method, a deposition method, a kneading method, or the like can be used. Specifically, in addition to an aqueous solution containing a starting material of vanadium, tungsten and / or molybdenum in a titanium-based oxide powder, together with an organic or inorganic forming aid generally used when performing this type of molding, mixing, Method of evaporating moisture by heating while kneading to form an extrudable paste, forming this into a honeycomb or the like with an extruder, drying, and firing in air at a high temperature (preferably 200 to 600 ° C.) Etc. As another method, titanium oxide powder is pre-shaped into a spherical, cylindrical pellet, lattice-shaped honeycomb, and fired, and then an aqueous solution containing vanadium, tungsten and / or molybdenum starting materials is prepared. An impregnation method can also be employed. Further, a method of directly kneading titanium oxide powder with vanadium, tungsten and / or molybdenum oxide powder can be employed. In addition, a method of adding an aqueous solution of a compound containing vanadium, tungsten and / or molybdenum to a solution or slurry containing titanium or the like in the step of preparing a titanium-based oxide, or a step of preparing a titanium-based oxide by filtration or the like A method of adding an aqueous solution of a compound containing vanadium, tungsten and / or molybdenum to a cake obtained by removing moisture from the slurry, mixing, drying, and firing can also be employed.

  As the vanadium source, for example, in addition to vanadium oxide, a vanadium compound such as hydroxide, ammonium salt, oxalate, halide, sulfate, and the like can be appropriately selected and used.

  As the tungsten source, for example, tungsten oxide, ammonium paratungstate, ammonium metatungstate, tungstic acid, and the like can be appropriately selected and used.

  Any molybdenum source may be used as long as it generates molybdenum oxide by firing. For example, molybdenum oxide, hydroxide, ammonium salt, halide, etc., specifically ammonium paramolybdate, molybdic acid, etc. It can select suitably from etc. and can be used.

  The content of vanadium, tungsten and / or molybdenum in the exhaust gas treatment catalyst of the present invention is 0.1 to 25% by mass, preferably 0.5 to 20% by mass, more preferably 1 based on the total mass of the catalyst. ˜15 mass%.

The exhaust gas treatment catalyst of the present invention preferably contains sulfur (S). As a method for adding sulfur, for example, a method of immersing the catalyst in an aqueous solution of sulfuric acid or sulfate, a method of bringing the catalyst into contact with a gas containing sulfur dioxide (SO ₂ ), or the like is used as appropriate. Can do.

  As the sulfur source, for example, sulfuric acid, ammonium sulfate, ammonium hydrogen sulfate, sulfur dioxide gas and the like can be appropriately selected and used.

  When the exhaust gas treatment catalyst of the present invention contains sulfur, the content thereof is 0.01 to 3% by mass, preferably 0.1 to 3% by mass, more preferably 0.5 to 0.5%, based on the total mass of the catalyst. 3% by mass.

  As the exhaust gas treatment catalyst according to the present invention, only the titanium-based oxide and vanadium, tungsten and / or molybdenum (hereinafter sometimes collectively referred to as catalyst components) are used as constituent materials of the catalyst. Although a mold-type catalyst formed by molding a catalyst component in a certain shape is a preferred form, even a supported-type catalyst in which a catalyst component is supported on an arbitrary inert carrier having a desired shape, or the above-mentioned molding A catalyst obtained by appropriately combining a type catalyst and a supported catalyst may be used.

  The shape of the exhaust gas treatment catalyst of the present invention is not particularly limited, and is a shape generally used for this type of catalyst, for example, honeycomb shape, spherical shape, plate shape, net shape, columnar shape, cylindrical shape, corrugated shape (corrugated) It can be determined by appropriately selecting from a shape, a pipe shape, a donut shape, and the like.

  The pore volume of the exhaust gas treatment catalyst of the present invention is usually 0.2 to 0.8 cm 3 / g, preferably 0.25 to 0.7 m 3 / g, more preferably 0.25 to 0.6 cm 3 / g. g.

  The BET specific surface area of the exhaust gas treatment catalyst of the present invention is not particularly limited, but is preferably 30 to 250 m2 / g, more preferably 40 to 250 m2 / g, and still more preferably 45 to 250 m2 / g. .

The exhaust gas containing the harmful substances such as nitrogen oxides and dioxins can be brought into contact with the exhaust gas treatment catalyst of the present invention as described above to decompose the harmful substances and treat the exhaust gas. The contact conditions are not particularly limited, and the contact conditions can be carried out under conditions generally used for this type of treatment. The space velocity of the exhaust gas is usually 100~100,000hr ^-1 (STP), preferably 200~50,000hr ^-1 (STP), more preferably 200~29,000hr ^-1 (STP). About processing temperature, the temperature of the waste gas which should be processed is 100-500 degreeC normally, Preferably it is 200-500 degreeC, More preferably, it is 250-500 degreeC.

  The invention is further illustrated by the following examples, which illustrate advantageous embodiments of the invention.

Example 1
<Ti-Si composite oxide (a)>
After adding 10 kg of Snowtex-20 (Nissan Chemical Co., Ltd., containing about 20% by mass of SiO ₂ ) to 137 liter of 25% by mass ammonia water, stirring and mixing, sulfuric acid solution of titanyl sulfate (70 g / L as TiO ₂₎ 257 liters of sulfuric acid concentration 287 g / liter) was added dropwise over 120 minutes with stirring (pH 8). The obtained gel was allowed to stand for 20 hours, then filtered, washed with water, and then dried at 120 ° C. for 20 hours. This was fired at 500 ° C. for 5 hours, further pulverized using a hammer mill, and classified by a classifier to obtain a powder having an average particle size of 12 μm.

The X-ray diffraction pattern of the obtained powder is shown in FIG. No obvious intrinsic peak of SiO ₂ was observed, and a broad diffraction peak was obtained at 2θ = 25.3 °. Therefore, the powder was a composite oxide of titanium and silicon (Ti-Si composite oxide). ) (A) was confirmed.

<Honeycomb catalyst>
In 8 liters of water, 1.3 kg of ammonium metavanadate, 1.9 kg of ammonium paratungstate, 2.0 kg of oxalic acid and 1.2 kg of monoethanolamine were mixed and dissolved to prepare a uniform solution. 18.0 kg of the previously prepared Ti-Si composite oxide (a) powder was put into a kneader, and then the above homogeneous solution was added together with a molding aid such as an organic binder (starch 1.5 kg), followed by thorough stirring. Further, after adding a proper amount of water and thoroughly mixing with a blender, the mixture was sufficiently kneaded with a continuous kneader, and extruded into a honeycomb shape having an outer shape of 80 mm square, an opening of 4.0 mm, a wall thickness of 1.0 mm, and a length of 500 mm. The obtained molded product was dried at 60 ° C. and then calcined at 450 ° C. for 5 hours to obtain a catalyst (1). The composition of this catalyst was Ti: Si: V: W (TiO ₂ : SiO ₂ : V ₂ O ₅ : converted ratio as WO ₃ ) = 78.3: 8.7: 5: 8.

  For the catalyst (1), a chart obtained by FT-IR analysis is shown in FIG. 2, and the ratio (B / L) obtained based on this chart is shown in Table 1.

Example 2
A catalyst (2) was obtained in the same manner as in Example 1, except that 2.0 kg of ammonium paramolybdate was used instead of 1.9 kg of ammonium paratungstate. The composition of the catalyst (2) was Ti: Si: V: Mo (equivalent ratio as TiO ₂ : SiO ₂ : V ₂ O ₅ : MoO ₃ ) = 78.3: 8.7: 5: 8. The ratio (B / L) of the catalyst (2) determined by the FT-IR analysis method is shown in Table 1.

Example 3
<Ti-Si-Mo composite oxide (b)>
Silica sol (Snowtex-30, manufactured by Nissan Chemical Co., Ltd., containing 30% by mass in terms of SiO ₂ ) 3.3 kg, industrial ammonia water (containing 25% by mass ammonia) 103 kg, and 58 liters of water were mixed with molybdic acid 3 .4 kg was added and stirred well to completely dissolve the molybdic acid to obtain a uniform solution. To this solution, 228 liters of a sulfuric acid solution of titanyl sulfate (70 g / liter as TiO ₂ , sulfuric acid concentration 287 g / liter) was added dropwise with stirring over 120 minutes to form a precipitate (pH 8). The coprecipitated slurry was allowed to stand for about 40 hours, filtered, thoroughly washed with water, and dried at 100 ° C. for 1 hour. Further, it was fired at 500 ° C. for 5 hours in an air atmosphere. The powder was pulverized using a hammer mill and classified by a classifier to obtain a powder having an average particle size of 12 μm.

In the X-ray diffraction chart of the obtained powder, no obvious intrinsic peaks of SiO ₂ and MoO ₃ were observed, and a broad diffraction peak was obtained at 2θ = 25.3 °, and composite oxidation of titanium, silicon and molybdenum Product (Ti-Si-Mo composite oxide) (b).

<Honeycomb catalyst>
In 8 liters of water, 1.8 kg of ammonium metavanadate, 1.67 kg of oxalic acid, and 0.4 kg of monoethanolamine were mixed and dissolved to prepare a uniform solution. 18.6 kg of the previously prepared Ti-Si-Mo composite oxide powder was put into a kneader, and the above vanadium-containing solution was added together with a molding aid such as an organic binder (starch 1.5 kg), followed by thorough stirring. Further, after mixing well with a blender while adding an appropriate amount of water, the mixture was sufficiently kneaded with a continuous kneader and extruded into a honeycomb shape having an outer shape of 80 mm square, an aperture of 44.0 mm, a wall thickness of 1.0 mm, and a length of 500 mm. The obtained molded product was dried at 60 ° C. and then calcined at 450 ° C. for 5 hours to obtain a catalyst (3). The composition of this catalyst was Ti: Si: Mo: V (converted ratio as TiO ₂ : SiO ₂ : MoO ₃ : V ₂ O ₅ ) = 74.3: 4.7: 14: 7. Table 1 shows the ratio (B / L) of the catalyst (3) obtained by the FT-IR analysis method.

Comparative Example 5
In 8 liters of water, 1.8 kg of ammonium metavanadate, 1.7 kg of ammonium sulfate, 1.67 kg of oxalic acid, and 0.4 kg of monoethanolamine were mixed and dissolved to prepare a uniform solution. After putting 6.2 kg of commercially available TiO ₂ powder (DT-51 (trade name), manufactured by Millennium) into a kneader, the above vanadium-containing solution is added together with a molding aid such as an organic binder (starch 1.5 kg). Stir. Further, after adding a proper amount of water and thoroughly mixing with a blender, the mixture was sufficiently kneaded with a continuous kneader, and extruded into a honeycomb shape having an outer shape of 80 mm square, an opening of 4.0 mm, a wall thickness of 1.0 mm, and a length of 500 mm. The obtained molded product was dried at 60 ° C. and then calcined at 450 ° C. for 5 hours to obtain a catalyst (4). The composition of this catalyst was Ti: V: S (a conversion ratio as TiO ₂ : V ₂ O ₅ : S) = 92.5: 7: 0.5. The ratio (B / L) of the catalyst (4) determined by the FT-IR analysis method is shown in Table 1.

Comparative Example 1
<Ti-Si composite oxide (d)>
10 kg of SNOWTEX-20 was added to 257 liters of a sulfuric acid solution of titanyl sulfate (70 g / liter as TiO ₂ , sulfuric acid concentration 287 g / liter), stirred and mixed, and this mixed aqueous solution was heated to 70 ° C. To the heated mixed aqueous solution, 137 liters of 25% by mass ammonia water was added dropwise over 30 minutes with stirring, and then adjusted to pH = 7. The obtained gel was stirred at 70 ° C. for 2 hours, filtered, washed with water, and then dried at 100 ° C. for 20 hours. This was fired at 500 ° C. for 5 hours, further pulverized using a hammer mill, and classified by a classifier to obtain a powder having an average particle size of 12 μm.

An X-ray diffraction pattern of the obtained powder is shown in FIG. According to this, a clear intrinsic peak of SiO ₂ was not recognized, and a broad diffraction peak was obtained at 2θ = 25.3 °, and the powder was a composite oxide of titanium and silicon (Ti-Si composite oxide). ) (D) was confirmed.

<Honeycomb catalyst>
In 8 liters, 1.3 kg of ammonium metavanadate, 1.9 kg of ammonium paratungstate, 2.0 kg of oxalic acid and 1.2 kg of monoethanolamine were mixed and dissolved in water to prepare a uniform solution. 18 kg of the Ti-Si composite oxide (d) prepared previously was put into a kneader, and the above vanadium and tungsten-containing solution was added together with a molding aid of an organic binder (starch 1.5 kg), followed by thorough stirring. Further, after mixing well with a blender while adding an appropriate amount of water, the mixture was sufficiently kneaded with a continuous kneader and extruded into a honeycomb shape having an outer shape of 80 mm square, an opening of 4.0 mm, a wall thickness of 1.0 mm, and a length of 500 mm. The obtained molded product was dried at 60 ° C. and then calcined at 450 ° C. for 5 hours to obtain a catalyst (5). The composition of this catalyst (5) was Ti: Si: V: W (a conversion ratio as TiO ₂ : SiO ₂ : V ₂ O ₅ : WO ₃ ) = 78.3: 8.7: 5: 8. With respect to the catalyst (5), a chart obtained by the FT-IR analysis method is shown in FIG. 4, and a ratio (B / L) obtained based on this chart is shown in Table 1.

Comparative Example 2
1.4 kg of commercially available V ₂ O ₅ powder was mixed with 18.6 kg of commercially available anatase-type oxidized titania powder (DT-51 (trade name), manufactured by Millennium), put into a kneader, and then an organic binder (starch 1.5kg), etc., and mixing well with a blender while adding an appropriate amount of water, and then kneaded purely with a continuous kneader. External shape 80mm square, 4.0mm aperture, 1.0mm wall thickness, length Extruded into a 500 mm honeycomb. The obtained molded product was dried at 60 ° C. and then calcined at 500 ° C. for 5 hours to obtain a catalyst (6). The composition of this catalyst was Ti: V = 95: 5 (a conversion ratio of TiO ₂ : V ₂ O ₅ ).

  The X-ray diffraction pattern of the anatase-type titania powder is shown in FIG. The ratio (B / L) of the catalyst (6) determined by the FT-IR analysis method is shown in Table 1.

Example 5
Using the catalysts (1) to (6) obtained in Examples 1 to 3 and Comparative Examples 1 , 2 , and 5 , activity evaluation tests (denitration reaction test and chlorotoluene decomposition test) were performed under the following conditions.

(Activity evaluation test)
36.3 ml of each of the catalysts (1) to (6) was filled into a stainless steel reaction tube having a length of 1200 mm and a diameter of 50 mm, and the following reaction gas was allowed to flow at the following reaction gas temperature and space velocity, respectively, NOx concentration and chlorotoluene concentration were measured to obtain NOx removal rate (denitration rate) and chlorotoluene decomposition rate.

(Denitration test conditions)
Reaction gas = NOx: 200 ppm, NH ₃ : 200 ppm, SO ₂ : 50 ppm, O ₂ : 10%, H ₂ O: 12%, N ₂ : balance Reaction gas temperature: 200 ° C., 300 ° C. and 400 ° C.
Space velocity: 17,000 hr ⁻¹ (STP)
The denitration rate was determined according to the following formula.

(Chlorotoluene decomposition test conditions)
Reaction gas = chlorotoluene: 20 ppm, SO ₂ : 50 ppm, O ₂ : 10%, H ₂ O: 12%, N ₂ : balance Reaction gas temperature = 200 ° C.
Space velocity = 3800 hr ⁻¹
The chlorotoluene decomposition rate was determined according to the following formula.

  The results are shown in Table 1.

Example 6
In Example 1, except that by changing the amount of 25 wt% ammonia water 69 liters with 88 liters of titanium tetrachloride aqueous solution (36% by mass as TiO ₂ containing) instead of sulfuric acid solution 257 l of titanyl sulfate Similarly, a Ti—Si composite oxide (e) was obtained. With respect to the obtained Ti—Si composite oxide (e), the solid acid amount satisfying pKa ≦ + 3.3 is shown in Table 1, and the chart obtained by the FT-IR analysis method is shown in FIG. The ratio (B / L) obtained in this manner is shown in Table 2.

<Honeycomb catalyst>
In 8 liters of water, 1.3 kg of ammonium metavanadate, 1.9 kg of ammonium paratungstate, 2.0 kg of oxalic acid and 1.2 kg of monoethanolamine were mixed and dissolved to prepare a uniform solution. 18 kg of the previously prepared Ti-Si composite oxide (e) powder was put into a kneader, and then the above homogeneous solution was added together with a molding aid such as an organic binder (starch 1.5 kg), followed by thorough stirring. Further, after adding a proper amount of water and thoroughly mixing with a blender, the mixture was sufficiently kneaded with a continuous kneader, and extruded into a honeycomb shape having an outer shape of 80 mm square, an opening of 4.0 mm, a wall thickness of 1.0 mm, and a length of 500 mm. The obtained molded product was dried at 60 ° C. and then calcined at 450 ° C. for 5 hours to obtain a catalyst (1). The composition of this catalyst was Ti: Si: V: W (TiO ₂ : SiO ₂ : V ₂ O ₅ : converted ratio as WO ₃ ) = 78.3: 8.7: 5: 8.

Example 7
In Example 6, a catalyst (8) was obtained in the same manner except that 2.0 kg of ammonium paramolybdate was used instead of 1.9 kg of ammonium paratungstate when preparing the honeycomb catalyst. The composition of the catalyst (8) was Ti: Si: V: Mo (equivalent ratio as TiO ₂ : SiO ₂ : V ₂ O ₅ : MoO ₃ ) = 78.3: 8.7: 5: 8.

Example 8
In Example 3, the amount of aqueous ammonia was changed to 52 kg, and instead of using 228 liters of a sulfuric acid solution of titanyl sulfate, 78 liters of an aqueous solution of titanium tetrachloride (containing 36% by mass as TiO ₂ ) was used. A Ti—Si—Mo composite oxide (f) was obtained. Regarding the obtained Ti—Si—Mo composite oxide (f), the solid acid amount satisfying pKa ≦ + 3.3 is shown in Table 2, and the ratio (B / L) obtained by FT-IR analysis is shown in Table 2. Indicated.

<Honeycomb catalyst>
In 8 liters of water, 1.29 kg of ammonium metavanadate, 1.67 kg of oxalic acid, and 0.4 kg of monoethanolamine were mixed and dissolved to prepare a uniform solution. After adding 19 kg of the previously prepared Ti-Si-Mo composite oxide (f) powder to a kneader, the above vanadium-containing solution was added together with a molding aid such as an organic binder (starch 1.5 kg) and stirred well. Further, after adding a proper amount of water and thoroughly mixing with a blender, the mixture was sufficiently kneaded with a continuous kneader, and extruded into a honeycomb shape having an outer shape of 80 mm square, an opening of 4.0 mm, a wall thickness of 1.0 mm, and a length of 500 mm. The obtained molded product was dried at 60 ° C. and then calcined at 450 ° C. for 5 hours to obtain a catalyst (3). The composition of this catalyst was Ti: Si: Mo: V (equivalent ratio as TiO ₂ : SiO ₂ : MoO ₃ : V ₂ O ₅ ) = 76.4: 4.8: 14.2: 5.

Comparative Example 6
<TiO ₂ powder (g)>
300 liters of a sulfuric acid solution of titanyl sulfate (70 g / liter as TiO ₂ , sulfuric acid concentration 287 g / liter) was dropped into 160 liters of 25 mass% aqueous ammonia over 120 minutes with stirring (pH 8). The obtained gel was allowed to stand for 20 hours, then filtered, washed with water, and then dried at 120 ° C. for 20 hours. This was fired at 520 ° C. for 3 hours, further pulverized using a hammer mill, and classified by a classifier to obtain TiO ₂ powder (g) having an average particle diameter of 12 μm.

Regarding this TiO ₂ powder (g), the solid acid amount satisfying pKa ≦ + 3.3 is shown in Table 2, and the ratio (B / L) obtained by FT-IR analysis is shown in Table 2.

<Honeycomb catalyst>
In Example 8, a catalyst (10) was obtained in the same manner as in Example 8 except that the above powder TiO ₂ (g) was used instead of the Ti—Si—Mo composite oxide (f). The composition of the catalyst (10) was Ti: V (equivalent ratio as TiO ₂ : V ₂ O ₅ ) = 95: 5.

Comparative Example 3
In Comparative Example 1, the amount of aqueous ammonia was changed to 69 kg, and the same procedure was performed except that 88 liters of titanium tetrachloride aqueous solution (containing 36% by mass as TiO ₂ ) was used instead of 257 liters of sulfuric acid solution of titanyl sulfate. Ti-Si composite oxide (h) was obtained. Regarding the obtained Ti—Si composite oxide (h), the solid acid amount satisfying pKa ≦ + 3.3 is shown in Table 2, and the chart obtained by the FT-IR analysis method is shown in FIG. The ratio (B / L) obtained in this manner is shown in Table 2.

<Honeycomb catalyst>
In 8 liters, 1.3 kg of ammonium metavanadate, 1.9 kg of ammonium paratungstate, 2.0 kg of oxalic acid and 1.2 kg of monoethanolamine were mixed and dissolved in water to prepare a uniform solution. 18 kg of the previously prepared Ti—Si composite oxide (h) was put into a kneader, and the above vanadium and tungsten-containing solution was added together with a molding aid of an organic binder (starch 1.5 kg), followed by thorough stirring. Further, after mixing well with a blender while adding an appropriate amount of water, the mixture was sufficiently kneaded with a continuous kneader and extruded into a honeycomb shape having an outer shape of 80 mm square, an opening of 4.0 mm, a wall thickness of 1.0 mm, and a length of 500 mm. The obtained molded product was dried at 60 ° C. and then calcined at 450 ° C. for 5 hours to obtain a catalyst (11). The composition of this catalyst was Ti: Si: V: W (TiO ₂ : SiO ₂ : V ₂ O ₅ : converted ratio as WO ₃ ) = 78.3: 8.7: 5: 8.

Comparative Example 4
<TiO ₂ powder (i)>
In Comparative Example 6 , when the TiO ₂ powder (g) was prepared, the gel was filtered and not washed with water, and dried at 120 ° C. for 20 hours. This was fired at 520 ° C. for 3 hours, further pulverized using a hammer mill, and classified by a classifier to obtain TiO ₂ powder (i) having an average particle diameter of 12 μm.

Regarding the powder TiO ₂ (i), solid acid amounts satisfying pKa ≦ + 3.3 are shown in Table 2, and ratios (B / L) obtained by FT-IR analysis are shown in Table 2.

Hereinafter, a honeycomb catalyst was prepared in the same manner as in Comparative Example 6 except that TiO ₂ powder (i) was used instead of TiO ₂ powder (g) to obtain catalyst (12). The composition of this catalyst was Ti: V: S = 85: 5: 10 (a conversion ratio of TiO ₂ : V ₂ O ₅ : S).

Example 10
Using the catalysts (7) to (12) obtained in Examples 6 to 8 and Comparative Examples 3 , 4 , and 6, activity evaluation tests (denitration reaction test and chlorotoluene decomposition test) were performed under the following conditions.

(Activity evaluation test)
Using the catalysts (7) to (12), the NOx removal rate (denitration rate) and the chlorotoluene decomposition rate were determined in the same manner as in Example 5.

(Denitration reaction conditions)
Reaction gas = NOx: 200 ppm, NH ₃ : 200 ppm, SO ₂ : 50 ppm, O ₂ : 9%, H 2 O: 15%, N 2: balance Reaction gas temperature: 200 ° C., 300 ° C. and 400 ° C.
Space velocity: 15,000 hr-1 (STP)
The denitration rate was determined according to the following formula.

(Chlorotoluene decomposition test conditions)
Reaction gas = chlorotoluene: 40 ppm, SO ₂ : 50 ppm, O ₂ : 9%, H ₂ O: 15%, N ₂ : balance Reaction gas temperature = 200 ° C.
Space velocity = 3100hr-1
The chlorotoluene decomposition rate was determined according to the following formula.

  The results are shown in Table 2.

Example 11
In Example 1, Ti-Si composite oxide (j) and catalyst (13) were obtained in the same manner as in Example 1 except that a sulfuric acid solution of titanyl sulfate was added dropwise over 90 minutes. The ratio (B / L) of the catalyst (13) determined by the FT-IR method is shown in Table 3, and the solid acid amount of pKa ≦ + 3.3 for the Ti—Si composite oxide (j) is shown in Table 4. The ratios (B / L) determined by the FT-IR method are shown in Table 4, respectively.

Example 12
In Example 1, a Ti—Si composite oxide (k) and a catalyst (14) were obtained in the same manner as in Example 1 except that a sulfuric acid solution of titanyl sulfate was dropped over 60 minutes. The ratio (B / L) of the catalyst (14) determined by the FT-IR method is shown in Table 3, and the solid acid amount of pKa ≦ + 3.3 for the Ti—Si composite oxide (k) is shown in Table 4. The ratios (B / L) determined by the FT-IR method are shown in Table 4, respectively.

Example 13
In Example 1, a mixed solution of 137 liters of 25 % by mass ammonia water and 10 kg of Snowtex-20 was added dropwise to 257 liters of a sulfuric acid solution of titanyl sulfate over 120 minutes with stirring, as in Example 1. Thus, Ti-Si composite oxide (l) and catalyst (15) were obtained. The ratio (B / L) of the catalyst (15) determined by the FT-IR method is shown in Table 3, and the solid acid amount of pKa ≦ + 3.3 for the Ti—Si composite oxide (l) is shown in Table 4. The ratios (B / L) determined by the FT-IR method are shown in Table 4, respectively.

Example 14
Using the catalysts (1), (13), (14), (15) and (5) obtained in Examples 1, 11, 12, 13 and Comparative Example 1, the activity was carried out under the same conditions as in Example 5. Each evaluation test was conducted. The results are shown in Table 3.

Example 15
Using the catalysts (7), (13), (14), (15) and (11) obtained in Examples 6, 11, 12, 13 and Comparative Example 3, the activity was performed under the same conditions as in Example 10. Each evaluation test was conducted. The results are shown in Table 4 .

2 is an X-ray diffraction pattern of the Ti—Si composite oxide obtained in Example 1. FIG. 2 is an FT-IR spectrum of the adsorbed pyridine of the catalyst (1) obtained in Example 1. 2 is an X-ray diffraction diagram of a Ti—Si composite oxide obtained in Comparative Example 1. FIG. 4 is an FT-IR spectrum of an adsorbed pyridine of the catalyst (5) obtained in Comparative Example 1. 4 is an X-ray diffraction pattern of anatase-type titania powder used in Comparative Example 2. FIG. 4 is an FT-IR spectrum of an adsorbed pyridine of the Ti—Si composite oxide (e) obtained in Example 6. 4 is an FT-IR spectrum of an adsorbed pyridine of a Ti—Si composite oxide (h) obtained in Comparative Example 3.

Claims (13)

A catalyst for treating exhaust gas for decomposing and removing harmful substances in exhaust gas containing a titanium-based oxide and other catalytically active components, the ratio of Bronsted acid (B) and Lewis acid (L) in the catalyst (B / L) is in the range of 0/1 to 10/1, and the titanium-based oxide is selected from the group consisting of a composite oxide of titanium and silicon, or a group consisting of titanium, silicon, chromium, molybdenum, and tungsten. and a composite oxide of at least one element, the other catalytically active components, characterized vanadium, at least one element or a compound der Rukoto selected from the group consisting of tungsten and molybdenum Exhaust gas treatment catalyst. 2. The exhaust gas according to claim 1, wherein the ratio (B / L) of the titanium-based oxide is 0/1 to 1/1, and the solid acid amount satisfying pKa ≦ + 3.3 is 0.3 mmol / g or more. Treatment catalyst. The catalyst according to claim 1 or 2 , wherein the ratio of the catalyst is 0/1 to 9/1. The catalyst according to any one of claims 1 to 3, wherein the titanium-based oxide is a composite oxide of titanium and silicon or a composite oxide of titanium, silicon, and chromium . The catalyst according to any one of claims 1 to 4 , wherein the titanium-based oxide is a composite oxide of titanium and silicon . The titanium content in the titanium-based oxide is 40 to 95 mass% with respect to the total mass of titanium and silicon, chromium, molybdenum, and tungsten, according to any one of claims 1 to 5. catalyst.   The catalyst according to any one of claims 1 to 6, wherein the content of the titanium-based oxide is 75 to 99.9 mass% based on the total amount of the catalyst. The catalyst according to any one of claims 2 to 8, wherein a solid acid amount of pKa ≦ + 3.3 of the titanium-based oxide is 0.3 to 0.8 mmol / g. In an acidic solution containing a titanium compound, silicon or silicic element and chromium, when to produce by the addition of aqueous ammonia solution containing at least one element selected from the group consisting of Mo Ribuden and tungsten precipitate, start the addition through the steps is time to finish the addition of the entire amount from the the 40 minutes or more, according to any one of claims 1-8, characterized by using the resulting titanium-based oxides catalysts Manufacturing method. Silicon or silicon and chromium, the aqueous ammonia solution containing at least one element selected from Mo Ribuden the group consisting of tungsten,, when to produce a precipitate by adding an acidic solution containing a titanium compound, to start added from through the steps time to finish the addition of the total amount is more than 40 minutes, the preparation of the catalyst according to any one of claims 1-8, characterized by using the resulting titanium-based oxides Method. Silicon or silicon and chromium, in an acidic solution containing at least one element and a titanium compound selected from the group consisting of Mo Ribuden and tungsten,, when to produce a precipitate by the addition of aqueous ammonia solution, to start added from through the steps time to finish the addition of the total amount is more than 40 minutes, the preparation of the catalyst according to any one of claims 1-8, characterized by using the resulting titanium-based oxides Method. Aqueous ammonia solution, silicon or silicic element and chromium, when to produce an acidic solution by adding a precipitate containing at least one element and a titanium compound selected from the group consisting of Mo Ribuden and tungsten, and start added through the steps is time to finish the addition of the entire amount from the the 40 minutes or more, according to any one of claims 1-8, characterized by using the resulting titanium-based oxides catalysts Manufacturing method. An exhaust gas treatment method comprising contacting an exhaust gas containing a hazardous substance with the exhaust gas treatment catalyst according to any one of claims 1 to 8 to decompose and remove the harmful substance.

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