JP2016068033A - Method for producing exhaust gas treatment catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an exhaust gas treatment catalyst which is significantly increased in mechanical strength without impairing catalytic activity.SOLUTION: There are provided: a method for producing an exhaust gas treatment catalyst in which when a titanium-vanadium-based catalyst is produced, a dried powder obtained by pulverizing an unused catalyst obtained in a drying step of producing a catalyst and/or a baked powder obtained by pulverizing an unused catalyst obtained in a baking step of a catalyst and a used catalyst powder obtained by pulverizing a catalyst containing a used titanium-based oxide and vanadium-based oxide which were used for treating exhaust gas are mixed with a raw material powder of a catalyst; and an exhaust gas treatment method for treating exhaust gas containing a nitrogen oxide (NOx) and/or an organic halogen compound using the catalyst obtained by the production method.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing an organic halogen compound removal catalyst or exhaust gas treatment catalyst for removing nitrogen oxides (NOx) in exhaust gas, and in particular, mechanical strength is significantly improved without impairing denitration activity. The present invention relates to a method for producing an exhaust gas treatment catalyst.

  A method of reducing and removing nitrogen oxides in exhaust gas from power plants and chemical plants with ammonia in the presence of a catalyst is widely used. The catalyst used in this reaction (denitration catalyst) usually contains an active component such as tungsten or molybdenum together with titanium and vanadium, and after kneading these raw materials, it is formed into a honeycomb-like or plate-like structure, further dried, Manufactured by firing.

  Since the catalyst itself is a structural body, damage during transportation (transport) and catalyst filling work, cracks and wear due to vibration during operation of the actual machine and collision of dust in the exhaust gas occur. For this reason, it is necessary to have a certain compressive strength, crushing strength or wear strength.

As a method for improving the strength and wear resistance of the catalyst, a catalyst manufactured by mixing a raw material for exhaust gas denitration catalyst, clay minerals and inorganic fibers with water and then molding the mixture into a predetermined shape (Patent Document 1), gas inlet side After the tip portion is coated with zirconia sol, zirconium silicate sol or the like, dried and calcined (Patent Document 2), and the catalyst pore diameter is substantially uniform and substantially from two independent pore groups. And a catalyst having a vertical crushing strength of 15 kg / cm ² or more when forming a honeycomb having an opening ratio of 70% or more is disclosed (Patent Document 3).

  Although all the catalysts have the effect of improving the strength and reducing the wear, they require inorganic fibers, sols, and additives for pore formation, leading to an increase in catalyst production costs. There was room for improvement. In order for the denitration catalyst to be widely used in the future, a production process of a denitration catalyst that is excellent in performance, strong, and inexpensive is desired.

JP 2006-223959 A JP-A-5-177144 JP-A-10-323570

  An object of the present invention is to provide a method for inexpensively producing an exhaust gas treatment catalyst having a significantly increased mechanical strength without impairing catalyst activity.

  As a result of intensive studies in order to solve the above problems, the present inventor has found that a catalyst obtained by the following production method is effective.

That is, the present invention relates to (1) a method for treating exhaust gas containing a titanium-based oxide and a vanadium oxide, wherein the production method kneads the raw material powder of the titanium-based oxide and the vanadium compound; And at least one of a dry powder obtained by pulverizing an unused catalyst obtained in the drying step and a calcined powder obtained by pulverizing an unused catalyst obtained in the calcining step. And a used catalyst powder obtained by pulverizing a catalyst containing a used titanium-based oxide and a vanadium-based oxide used for exhaust gas treatment, is mixed with the titanium-based oxide powder. A method for producing an exhaust gas treatment catalyst.
(2) The method for producing an exhaust gas treatment catalyst according to claim 1, wherein an average particle size (median diameter) of the dry powder, the calcined powder and the used catalyst is 5 to 80 μm.
(3) When mixing at least one of the dry powder and the fired powder and the used catalyst powder with the titanium-based raw material powder, the titanium-based raw material powder, the dry powder, The blending ratio of the titanium-based raw material powder in the mixed powder is 5 to 90% by mass with respect to the total mass of at least one kind of the calcined powder and the used catalyst powder, and the dry powder and the calcined powder. (1) or (2) characterized in that the blending ratio of at least one powder in the body is 5 to 30% by mass, and the blending ratio of the used catalyst powder is 5 to 80% by mass. The manufacturing method of the catalyst for exhaust gas description of description.
(4) An exhaust gas treatment method comprising treating exhaust gas containing nitrogen oxides using a catalyst obtained by the production method according to any one of (1) to (3).
(5) An exhaust gas treatment method comprising treating an exhaust gas containing an organic halogen compound using a catalyst obtained by the production method according to any one of (1) to (3).

  By using the present invention, it is possible to obtain a catalyst having excellent mechanical strength, in particular, significantly improved compressive strength, without impairing catalytic activity. Further, since no special raw material is required for improving the strength, an inexpensive catalyst can be obtained.

  Hereinafter, although the manufacturing method of the exhaust gas treatment catalyst according to the present invention will be described in detail, the scope of the present invention is not limited to these descriptions, and other than the following examples, the scope of the present invention is not impaired. Changes can be made as appropriate.

  The method for producing an exhaust gas treatment catalyst according to the present invention is a method for obtaining an exhaust gas treatment catalyst containing titanium-based oxide and vanadium-based oxide (hereinafter sometimes referred to as “titanium-vanadium-based catalyst”). A dry powder obtained by pulverizing an unused catalyst obtained in the drying step, and a firing step, which includes a step of kneading the raw material powder of the base oxide and the vanadium compound, a molding step, a drying step and a firing step The used catalyst powder obtained by pulverizing the catalyst containing at least one kind of the calcined powder obtained by pulverizing the obtained unused catalyst and the used titanium oxide and vanadium oxide used in the exhaust gas treatment is used as the titanium. It is made to mix with the raw material powder of a system oxide.

  Hereinafter, a general method for producing an exhaust gas treatment catalyst for carrying out the present invention will be described, and adjustment of the vanadium content in the powder of the catalyst material used for molding, which is a feature of the production method of the present invention, will also be described. This will be described in detail.

  The production method of the present invention generally comprises a step of obtaining a titanium oxide powder (hereinafter also referred to as titanium raw material powder or raw material powder) as a raw material from a titanium compound (hereinafter referred to as raw material powder preparation). A step), a step of mixing and further kneading the titanium-based raw material powder and vanadium with a chemical solution containing a catalytically active component (hereinafter also referred to as a kneading step), and a step of forming the kneaded product (hereinafter referred to as a step). , Also referred to as a molding step), a step of cutting the obtained molded body into a desired size (hereinafter also referred to as a cutting step), and a step of drying the cut body obtained by cutting (hereinafter also referred to as a drying step). And a step of obtaining a fired body by a step of firing a dried body obtained by drying (hereinafter also referred to as a firing step). In the present invention, Pre-fired powder obtained by grinding the fired body Prepared advance, it may be mixed with the titanium-based material powder in the kneading step at least one powder of the obtained dry powder and calcined powder.

  In the present invention, the dried product and the calcined product are unused catalysts, and those obtained by pulverizing the unused catalyst are dried powder and calcined powder, respectively. As a preferable form, a dry powder obtained by pulverizing a cut piece produced in the cutting process, or a baked powder obtained by pulverizing a powder that does not conform to the quality specifications of the product due to cracks or breakage produced in the firing process is used. It is to use. Conventionally, since cut pieces generated in each process and those that do not conform to the specifications have been discarded, this has been a factor in increasing manufacturing costs and increasing environmental waste due to a decrease in the yield of catalyst raw materials. Therefore, these problems can be solved.

  In this invention, the powder of the used catalyst used for exhaust gas treatment is included. Although the used catalyst used for this invention is not specifically limited, The used catalyst of the titanium-vanadium type catalyst mentioned later is used suitably.

  In the present invention, when mixing at least one of the dry powder and the calcined powder and the used catalyst powder with the titanium-based material powder, the titanium-based material powder, the dry powder and the calcined powder are used. The blending ratio of at least one of the dry powder and the calcined powder in the mixed powder is 5 to 30% by mass with respect to the total mass of at least one of the above and the used catalyst powder. What is necessary is just 7-28 mass%, More preferably, it is 10-25 mass%. The blending ratio of the spent catalyst powder may be 5 to 80% by mass, preferably 7 to 70% by mass, and more preferably 10 to 60% by mass. If it is the said range, this invention can be applied more effectively.

  In the present invention, the method for pulverizing the dried body, the calcined body, and the like and the used catalyst is not particularly limited. For example, a pulverization method using a hammer mill, a roller mill, a ball mill, an airflow pulverizer, or the like can be employed. . The dry powder or fired powder obtained by pulverization preferably has an average particle diameter (median diameter) of 100 μm or less, more preferably 5 to 80 μm, and still more preferably 10 to 60 μm. If the average particle diameter (median diameter) is larger than 100 μm, the strength may decrease.

  The titanium-vanadium catalyst of the present invention contains a titanium-based oxide and a vanadium-based oxide as essential components.

  The titanium-based oxide is an oxide containing titanium as an essential metal element. Specifically, even a titanium oxide (single oxide) is a composite oxide containing titanium and another metal element. It may be a thing.

  Examples of titanium oxides that are composite oxides include titania-silica composite oxide, titania-silica-zirconia composite oxide, titania-zirconia composite oxide, titania-silica-molybdenum composite oxide, and titania-molybdenum composite. Examples thereof include oxides, titania-silica-tungsten composite oxides, titania-tungsten composite oxides, titania-alumina composite oxides, and titania-silica composite oxides are preferable. There are no particular limitations on the preparation of the composite oxide, and a conventionally known method may be used. For example, a solution of a compound of each element is mixed, a precipitate is formed and then filtered, and the resulting filtrate is dried. After firing, it can be obtained by pulverization.

  The titanium-based oxide content (as oxide) is preferably 30 to 99.9% by weight, more preferably 50 to 99.9% by weight, and even more preferably 70 to 70% by weight based on the total mass of the finished catalyst. 99.9% by weight.

  In the titanium-vanadium catalyst of the present invention, the vanadium oxide can be contained by using a compound containing a vanadium element in the kneading step. Examples of the compound containing vanadium element include oxides, hydroxides, ammonium salts, oxalates, and sulfates of vanadium elements.

  The vanadium-based oxide content (as oxide) is preferably 0.1 to 25% by weight, more preferably 0.1 to 20% by weight, and still more preferably 0.8% by weight based on the total mass of the finished catalyst. 1 to 15% by weight.

  In the present invention, the titanium-vanadium catalyst may contain a metal oxide other than titanium oxide and vanadium oxide, such as tungsten, molybdenum, copper, iron, chromium, manganese, Examples thereof include oxides containing at least one element selected from the group consisting of zinc, cerium, tin and the like. Among these, tungsten and molybdenum are preferable.

  In the present invention, at least one of dry powder and calcined powder, a powder of a used catalyst, a titanium-based raw material powder, a chemical solution containing a catalytically active component essential for vanadium, and a molding aid are provided. Although it does not specifically limit as a form in the case of using and knead | mixing, For example, the following three are mentioned. That is, the first form is a mixture of at least one of dry powder and calcined powder, spent catalyst powder, titanium-based raw material powder and a solution containing an active ingredient, and a molding aid is added. The second form is a mixture of at least one of the dry powder and calcined powder, the spent catalyst powder and the titanium-based raw material powder, and then a solution containing the active ingredient is formed. In addition to the auxiliary agent, etc., the form of kneading, the third form is at least one kind of dry powder and calcined powder, used catalyst powder, titanium-based raw material powder and active ingredient In addition to a mixture of a solution and a molding aid or the like, it is a form of kneading.

  In the kneading step, if necessary, in addition to a mixture of at least one of dry powder and calcined powder and spent catalyst powder, inorganic fiber, sol, pore-forming agent, etc. are added and molded. These may be used in the range of the amount usually used for catalyst preparation.

  In the forming step, a part of the kneaded product obtained in the kneading step is used to form a desired catalyst shape. The molding is performed by using, for example, an extrusion molding machine that contains at least one of dry powder and calcined powder and a catalyst material that includes spent catalyst powder (including other components such as a molding aid as necessary). It may be formed into a desired shape using a catalyst and may be integrally molded so as to obtain a molded body made only of a catalyst material, or on a carrier having a desired shape (for example, a non-water-absorbing heat-resistant substrate). And coating with a catalyst material, which requires at least one of a dry powder and a calcined powder and a powder of a used catalyst (including other components such as a molding aid as necessary). It may be molded. The carrier that can be used in the case of supported molding is not particularly limited as long as it is made of a material that is usually used for obtaining a supported catalyst. Examples of the non-water-absorbing heat-resistant substrate include stainless steel and the like. Metals, ceramics such as cordierite, mullite, and SiC, and ceramic paper made from fibrous ceramics on paper-like materials, honeycombs, plates, nets, columns, cylinders, corrugated plates , Pipe shape, donut shape, lattice shape, plate shape (a shape in which a plurality of corrugated plates are stacked so that a space is provided between adjacent plates) or a corrugated shape.

  The shape of the catalyst is not particularly limited, and for example, it can be adopted in shapes such as a plate shape, a corrugated plate shape, a net shape, a honeycomb shape, a pellet shape, a columnar shape, and a cylindrical shape (pipe shape). A fine catalyst having a granular shape, a rod shape, a spherical shape, a ring shape, a cylindrical shape, or the like can be formed and used in a state of being filled or deposited in a container.

  In the drying step of the present invention, the drying temperature is not particularly limited, and may be appropriately set in consideration of the conditions of the subsequent firing step. The drying temperature is preferably 20 to 150 ° C, more preferably. Is 40 to 120 ° C, more preferably 50 to 100 ° C. The drying time is preferably 0.5 to 20 hours.

  In the calcination drying step of the present invention, the calcination temperature is not particularly limited and can be set within a range set in normal catalyst production. For example, it is preferably 300 to 600 ° C., more preferably 350 It is -580 degreeC, More preferably, it is 400-550 degreeC. If the calcination temperature is too low, the catalyst strength may be reduced, and if it is too high, the active component may be sintered or the catalyst specific surface area may be reduced, and the catalyst activity may be reduced. The firing time is preferably 1 to 40 hours.

  The present invention is also an exhaust gas treatment method for treating exhaust gas containing nitrogen oxides (NOx) and / or organic halogen compounds using the exhaust gas treatment catalyst obtained by the above production method.

  The exhaust gas treatment catalyst obtained by the production method of the present invention is suitable for the treatment of exhaust gas discharged from coal fired boilers and heavy oil fired boilers, incinerator exhaust gas discharged by incineration of industrial waste, municipal waste, etc. Used. The composition of the exhaust gas to be treated is not particularly limited, but as described above, the exhaust gas treatment catalyst obtained by the present invention is used as a denitration catalyst for removing nitrogen oxides (NOx) or an organic material for removing organic halogen compounds. It can be used effectively as a catalyst for removing halogen compounds.

  When the exhaust gas treatment catalyst obtained by the production method of the present invention is used as an organic halogen compound removal catalyst, the composition of the exhaust gas to be treated is not particularly limited as long as it contains an organic halogen compound, but particularly dioxins. Exhaust gas containing PCB (at least one selected from polyhalogenated dibenzodioxins, polyhalogenated dibenzofurans and polyhalogenated biphenyls) and PCB is preferred. In order to remove the organic halogen compound using the exhaust gas treatment catalyst obtained by the present invention, it is desirable that the exhaust gas is brought into contact with the catalyst and circulated at a temperature of 130 to 350 ° C., preferably 150 to 250 ° C. .

  When the exhaust gas treatment catalyst obtained by the production method of the present invention is used as a denitration catalyst, the catalyst is brought into contact with exhaust gas in the presence of a reducing agent such as ammonia or urea to reduce and remove nitrogen oxides in the exhaust gas. Like that. The treatment conditions at this time are not particularly limited, and the treatment can be performed under the treatment conditions generally used for this type of reaction. Specifically, it may be determined appropriately in consideration of the type and properties of exhaust gas, the required decomposition rate of nitrogen oxides, etc., but the temperature is preferably 150 to 600 ° C. If the exhaust gas temperature during the treatment is lower than 150 ° C., the denitration efficiency may be lowered, and if it exceeds 600 ° C., problems such as the sintering of the active component and the specific surface area of the catalyst may be caused.

  The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following examples as long as the effects of the present invention are achieved. Hereinafter, for the sake of convenience, “liter” may be simply referred to as “L”.

(Reference Example 1)
<Preparation of titanium-based raw material powder A (Ti-Si oxide)>
To a solution obtained by mixing 8 kg of silica sol (containing 30 wt% as SiO ₂ ) and 250 L of 10 mass% aqueous ammonia, 180 L of sulfuric acid solution of titanyl sulfate (containing 100 g / L as TiO ₂ , sulfuric acid concentration 400 g / L) is stirred well. After gradually dropping to form a precipitate, an appropriate amount of 25% by mass aqueous ammonia was added to adjust the pH to 8. This slurry was filtered, washed, and dried at 150 ° C. for 20 hours. This was fired at 550 ° C. for 5 hours in an air atmosphere, and further pulverized using a hammer mill to obtain titanium-based raw material powder A (Ti—Si oxide) having an average particle diameter (median diameter) of 35 μm. For the measurement of the average particle diameter (median diameter), a laser diffraction / scattering particle size distribution measuring apparatus LA-920 manufactured by Horiba Ltd. was used. The composition of the titanium-based raw material powder A was 88/12% by mass in terms of a TiO ₂ / SiO ₂ mass ratio (as oxide).

(Reference Example 2)
<Preparation of dry powder B>
A homogeneous solution in which 2.1 kg of ammonium metavanadate (containing 78 wt% as V ₂ O ₅ ), 3 kg of oxalic acid, and 1 kg of monoethanolamine were mixed and dissolved in 3 L of water and ammonium paratungstate (containing 90 wt% as WO ₃₎ ) Ti-Si oxide powder (powder A) prepared in Reference Example 1 with a uniform solution prepared by mixing and dissolving 1.3 kg and 0.5 kg of monoethanolamine in 2 L of water together with a molding aid and an appropriate amount of water. In addition to 20 kg, the mixture was kneaded with a kneader, and then formed into a honeycomb shape having an outer shape of 80 mm square, a length of 500 mm, an aperture of 2.9 mm, and a wall thickness of 0.4 mm by an extruder. This was dried at 80 ° C. for 1 hour and further pulverized using a hammer mill to obtain a dry powder B having an average particle diameter (median diameter) of 20 μm. The composition of the dry powder B was 77/11/ ₇ / ₅ % by mass in terms of the mass ratio of TiO ₂ / SiO ₂ / V ₂ O ₅ / WO ₃ (as oxide).

(Reference Example 3)
<Preparation of calcined powder C>
A homogeneous solution in which 2.1 kg of ammonium metavanadate (containing 78 wt% as V ₂ O ₅ ), 3 kg of oxalic acid, and 1 kg of monoethanolamine were mixed and dissolved in 3 L of water and ammonium paratungstate (containing 90 wt% as WO ₃₎ ) Ti-Si oxide powder (powder A) prepared in Reference Example 1 with a uniform solution prepared by mixing and dissolving 1.3 kg and 0.5 kg of monoethanolamine in 2 L of water together with a molding aid and an appropriate amount of water. In addition to 20 kg, the mixture was kneaded with a kneader, and then formed into a honeycomb shape having an outer shape of 80 mm square, a length of 500 mm, an aperture of 2.9 mm, and a wall thickness of 0.4 mm by an extruder. This was dried at 80 ° C. for 1 hour and then calcined at 450 ° C. for 5 hours in an air atmosphere. This was pulverized using a hammer mill to obtain calcined powder C having an average particle diameter (median diameter) of 15 μm. The composition of the calcined powder C was 77/11/ ₇ / ₅ % by mass in terms of a mass ratio of TiO ₂ / SiO ₂ / V ₂ O ₅ / WO ₃ (as oxide).

(Reference Example 4)
<Preparation of spent catalyst powder D>
The spent catalyst used in the examples of the present invention is a catalyst having the following course.
First, the spent catalyst a was prepared by mixing 2.1 kg of ammonium metavanadate (containing 78 wt% as V ₂ O ₅ ), 3 kg of oxalic acid, and 1 kg of monoethanolamine in 3 L of water and ammonium paratungstate. (Contains 90% by weight as WO ₃ ) 1.3 kg, Ti-Si oxidation prepared in Reference Example 1 together with a molding aid and an appropriate amount of water obtained by mixing and dissolving 0.5 kg of monoethanolamine in 2 L of water In addition to 20 kg of the product powder (titanium-based raw material powder A), it was kneaded with a kneader, and then molded into a honeycomb shape having an outer shape of 80 mm square, a length of 500 mm, an aperture of 2.9 mm, and a wall thickness of 0.4 mm by an extruder. . This was dried at 80 ° C. for 1 hour and then calcined at 450 ° C. for 5 hours in an air atmosphere.
The composition of the catalyst a is 88/ ₇ / ₅ % by mass (as oxide) of titanium-based raw material powder A / V ₂ O ₅ / WO ₃ , TiO ₂ / SiO ₂ / V ₂ O ₅ / WO ₃ The mass ratio (as oxide) was 77/11/7/5% by mass.
The catalyst a was charged into a coal-fired boiler exhaust gas treatment device and the exhaust gas was circulated, and operation was performed for 8000 hours. The exhaust gas treatment conditions and exhaust gas composition are shown below. The catalyst a after operation was pulverized using a hammer mill to obtain a used catalyst powder D having an average particle diameter (median diameter) of 20 μm.

<Exposure conditions>
Gas temperature: 350-380 ° C
Space velocity (STP): 3000 to 6000 hr ⁻¹
<Syngas composition>
NO _X: 150~200ppm, dry
NH _3: 120~160ppm, dry,
SO _X : 400 to 600 ppm, dry,
O ₂ : 2 to 4%, dry
H ₂ O: 7 to 10%, wet
N ₂ : balance
Example 1
<Preparation of catalyst A>
11.3 kg of Ti—Si oxide powder (titanium-based raw material powder A) prepared in Reference Example 1, 2.2 kg of Powder B obtained in Reference Example 2, and calcined powder obtained in Reference Example 3 C2.2 kg and 4.3 kg of the used catalyst powder D obtained in Reference Example 4 were mixed (B + C + D blending ratio: 44%). Next, ammonium metavanadate (containing 78 wt% as V ₂ O ₅ ) 1.2 kg, oxalic acid 1.7 kg, monoethanolamine 0.6 kg mixed and dissolved in 1.7 L of water and ammonium paratungstate (Contains 90% by weight as WO ₃ ) 0.7 kg, Ti-Si oxidation previously mixed with a homogeneous solution of 0.3 kg monoethanolamine mixed and dissolved in 1.1 L water together with molding aid and appropriate amount of water In addition to the product powder (titanium-based raw material powder A), dry powder B, calcined powder C and used catalyst powder D, after kneading with a kneader, the outer shape is 80 mm square, the length is 500 mm, It was molded into a honeycomb shape with an opening of 2.9 mm and a wall thickness of 0.4 mm. This was dried at 80 ° C. for 1 hour and then calcined at 450 ° C. for 5 hours in an air atmosphere to obtain Catalyst A. The composition of the catalyst A is 52/10/10 in terms of mass ratio (as oxide) of titanium-based raw material powder A / dry powder B / calcined powder C / used catalyst powder D / V ₂ O ₅ / WO _3. It was 77/11/7/5 mass% in mass ratio (as oxide) of / 20/4/3 mass% and TiO ₂ / SiO ₂ / V ₂ O ₅ / WO ₃ .

(Example 2)
<Preparation of catalyst B>
11.3 kg of Ti—Si oxide powder (titanium-based raw material powder A) prepared in Reference Example 1, 2.2 kg of Powder B obtained in Reference Example 2, and used catalyst obtained in Reference Example 4 Powder D (6.5 kg) was mixed (B + D blending ratio: 44%). Next, ammonium metavanadate (containing 78 wt% as V ₂ O ₅ ) 1.2 kg, oxalic acid 1.7 kg, monoethanolamine 0.6 kg mixed and dissolved in 1.7 L of water and ammonium paratungstate (Contains 90% by weight as WO ₃ ) 0.7 kg, Ti-Si oxidation previously mixed with a homogeneous solution of 0.3 kg monoethanolamine mixed and dissolved in 1.1 L water together with molding aid and appropriate amount of water In addition to the product powder (titanium-based raw material powder A), dry powder B and used catalyst powder D, after kneading with a kneader, the outer shape is 80 mm square, the length is 500 mm, the opening is 2.9 mm, Molded into a honeycomb with a thickness of 0.4 mm. This was dried at 80 ° C. for 1 hour and then calcined at 450 ° C. for 5 hours in an air atmosphere to obtain Catalyst B. The composition of the catalyst B is 52/10/30/4/3 mass by mass ratio (as oxide) of titanium-based raw material powder A / dry powder B / used catalyst powder D / V ₂ O ₅ / WO _3. %, And the mass ratio of TiO ₂ / SiO ₂ / V ₂ O ₅ / WO ₃ (as oxide) was 77/11/ ₇ / ₅ % by mass.

(Example 3)
<Preparation of catalyst C>
11.3 kg of the Ti—Si oxide powder (titanium-based raw material powder A) prepared in Reference Example 1, 2.2 kg of the calcined powder C obtained in Reference Example 3, and the used product obtained in Reference Example 4 Catalyst powder D (6.5 kg) was mixed (C + D blending ratio: 44%). Next, ammonium metavanadate (containing 78 wt% as V ₂ O ₅ ) 1.2 kg, oxalic acid 1.7 kg, monoethanolamine 0.6 kg mixed and dissolved in 1.7 L of water and ammonium paratungstate (Contains 90% by weight as WO ₃ ) 0.7 kg, Ti-Si oxidation previously mixed with a homogeneous solution of 0.3 kg monoethanolamine mixed and dissolved in 1.1 L water together with molding aid and appropriate amount of water In addition to the product powder (titanium-based raw material powder A), the calcined powder C, and the used catalyst powder D, after being kneaded by a kneader, the outer shape is 80 mm square, the length is 500 mm, the opening is 2.9 mm, Molded into a honeycomb with a thickness of 0.4 mm. This was dried at 80 ° C. for 1 hour and then calcined at 450 ° C. for 5 hours in an air atmosphere to obtain Catalyst C. The composition of the catalyst C is 52/10/30/4/3 mass by mass ratio (as oxide) of titanium-based raw material powder A / calcined powder C / used catalyst powder D / V ₂ O ₅ / WO _3. %, And the mass ratio of TiO ₂ / SiO ₂ / V ₂ O ₅ / WO ₃ (as oxide) was 77/11/ ₇ / ₅ % by mass.

Example 4
<Preparation of catalyst D>
9.4 kg of the Ti—Si oxide powder (titanium-based raw material powder A) prepared in Reference Example 1, 2.1 kg of the powder B obtained in Reference Example 2, and the fired powder obtained in Reference Example 3 C2.1 kg and 6.4 kg of the used catalyst powder D obtained in Reference Example 4 were mixed (B + C + D blending ratio: 53%). Next, 0.9 kg of ammonium metavanadate (containing 78 wt% as V ₂ O ₅ ), 1.4 kg of oxalic acid, and 0.5 kg of monoethanolamine were mixed and dissolved in 1.4 L of water and ammonium paratungstate. (Contains 90% by weight as WO ₃ ) 0.6kg, Ti-Si oxidation previously mixed with 0.9L of monoethanolamine mixed and dissolved in 0.9L of water together with molding aid and appropriate amount of water In addition to the product powder (titanium-based raw material powder A), dry powder B, calcined powder C and used catalyst powder D, after kneading with a kneader, the outer shape is 80 mm square, the length is 500 mm, It was molded into a honeycomb shape with an opening of 2.9 mm and a wall thickness of 0.4 mm. This was dried at 80 ° C. for 1 hour and then calcined at 450 ° C. for 5 hours in an air atmosphere to obtain Catalyst D. The composition of the catalyst D is 44/10/10 in terms of mass ratio (as oxide) of titanium-based raw material powder A / dry powder B / calcined powder C / used catalyst powder D / V ₂ O ₅ / WO _3. It was 77/11/7/5 mass% in mass ratio (as oxide) of / 30/3/3 mass% and TiO ₂ / SiO ₂ / V ₂ O ₅ / WO ₃ .

(Comparative Example 1)
<Preparation of catalyst E>
A homogeneous solution in which 2.1 kg of ammonium metavanadate (containing 78 wt% as V ₂ O ₅ ), 3 kg of oxalic acid, and 1 kg of monoethanolamine were mixed and dissolved in 3 L of water and ammonium paratungstate (containing 90 wt% as WO ₃₎ ) Ti-Si oxide powder (titanium-based raw material powder) prepared in Reference Example 1 with a uniform solution prepared by mixing and dissolving 1.3 kg and 0.5 kg of monoethanolamine in 2 L of water together with a molding aid and an appropriate amount of water Body A) In addition to 20 kg, the mixture was kneaded with a kneader, and then molded into a honeycomb shape having an outer shape of 80 mm square, a length of 500 mm, an aperture of 2.9 mm, and a wall thickness of 0.4 mm by an extruder. This was dried at 80 ° C. for 1 hour and then calcined at 450 ° C. for 5 hours in an air atmosphere to obtain Catalyst E. The composition of catalyst E is 88/ ₇ / ₅ % by mass in terms of mass ratio (as oxide) of titanium-based raw material powder A / V ₂ O ₅ / WO ₃ , TiO ₂ / SiO ₂ / V ₂ O ₅ / WO ₃ The mass ratio (as oxide) was 77/11/7/5% by mass.

(Measurement of compressive strength)
Using the catalysts A to D obtained in Examples 1 to 4 and the catalyst E obtained in Comparative Example 1, the compressive strength was measured under the following conditions.
In addition, the precision universal testing machine Autograph AG-250kNIS of Shimadzu Corporation was used for the measurement of compressive strength.
<Measurement conditions>
(1) A sample having an external shape of 80 mm square and a length of 80 mm is dried at 150 ° C. for 20 hours and then cooled to room temperature in a desiccator.
(2) A 2 mm thick kao wool sheet is sandwiched between the sample and the pressure plate 400 mmφ as shown in FIG.
(3) A load is applied until the sample is completely destroyed at a crosshead speed of 3 mm / min and a load cell of 250 kN.

Under the above conditions, the maximum load at the time of sample breakage of Catalysts A to D (Examples 1 to 4) and Catalyst E (Comparative Example 1) was measured, and the compressive strength was determined according to the following Equation 1. The obtained compressive strength is shown in Table 1. As can be seen from Table 1, the catalysts A to D (Examples 1 to 4) have higher compressive strength than the catalyst E (Comparative Example 1).
[Figure 1]

[Formula 1]

(Evaluation of denitration performance)
Catalysts A to D obtained in Examples 1 to 4 and Catalyst E obtained in Comparative Example 1 were filled in a stainless steel reaction tube immersed in a molten salt bath, and a synthesis gas having the following composition was charged under the following conditions. was introduced in the layer was measured NO _X removal rate.

NO _X removal rate reaction tube inlet and the NOx concentration in the reaction tube exit a NOx meter (chemiluminescent, Nippon Thermo Co. MODEL5100) was measured by, determined in accordance with Equation 2 below. The obtained NO _X removal rate is shown in Table 2. Catalyst A~D As can be seen from Table 2 (Examples 1-4) are compared to the catalyst E (Comparative Example 1), it can be seen NO _X removal rate is the same.

<Reaction conditions>
Gas temperature: 350 ° C
Space velocity (STP): 26000 hr ⁻¹
<Syngas composition>
NO _X : 100 ppm, dry
NH ₃ : 100 ppm, dry,
O ₂ : 15%, dry
H ₂ O: 10%, wet
N ₂ : balance
[Formula 2]

(Evaluation of dioxin removal performance)
Using the catalysts A to D obtained in Examples 1 to 4 and the catalyst E obtained in Comparative Example 1, a synthesis gas having the following composition was introduced into the catalyst layer under the following conditions, and the dioxin removal rate was measured. .

  The dioxin removal rate was determined according to the following formula 3. The obtained dioxins removal rate is shown in Table 3. As can be seen from Table 3, it can be seen that Catalysts A to D (Examples 1 to 4) have the same dioxin removal rate as compared to Catalyst E (Comparative Example 1).

<Reaction conditions>
Gas temperature: 200 ° C
Space velocity (STP): 4100 hr ⁻¹
<Syngas composition>
Dioxin concentration: 1 ng
O ₂ : 15%, dry
H ₂ O: 10%, wet
N ₂ : balance
[Formula 3]

  From the results of Examples and Comparative Examples, the catalyst obtained by the production method of the present invention has a markedly improved compressive strength of 4 to 5 times or more without impairing the denitration performance and dioxin removal performance. I understand.

Claims (5)

  A catalyst for exhaust gas treatment containing a titanium-based oxide and a vanadium-based oxide, the method comprising a step of kneading a raw material powder of a titanium-based oxide and a vanadium-based compound, a molding step, a drying step, A dry powder obtained by pulverizing an unused catalyst obtained in the drying step, and at least one kind of powder obtained by pulverizing an unused catalyst obtained in the calcination step, and an exhaust gas treatment. Production of exhaust gas treatment catalyst comprising mixing used catalyst powder obtained by pulverizing used titanium-based oxide and catalyst containing vanadium-based oxide with raw material powder of titanium-based oxide Method.   2. The method for producing an exhaust gas treatment catalyst according to claim 1, wherein an average particle diameter (median diameter) of the dry powder, the calcined powder and the used catalyst is 5 to 80 μm.   When mixing at least one of the dry powder and the fired powder and the spent catalyst powder with the titanium raw material powder, the titanium raw material powder, the dry powder and the fired powder The blending ratio of the titanium-based raw material powder in the mixed powder is 5 to 90% by mass with respect to the total mass of at least one kind of powder and the used catalyst powder, of the dry powder and the calcined powder. 3. The exhaust gas treatment catalyst according to claim 1, wherein the blending ratio of at least one kind of powder is 5 to 30 mass%, and the blending ratio of the used catalyst powder is 5 to 80 mass%. Manufacturing method.   An exhaust gas treatment method comprising treating exhaust gas containing nitrogen oxides using the catalyst obtained by the production method according to claim 1.   An exhaust gas treatment method comprising treating exhaust gas containing an organic halogen compound using the catalyst obtained by the production method according to claim 1.