JP2016107184A - Honeycomb catalyst and production method of honeycomb catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a honeycomb catalyst excellent in NOx purification performance at a low temperature, in which MnOis dispersed uniformly in a catalyst raw material.SOLUTION: There is provided a honeycomb catalyst comprising ceramic particles formed by attaching Mn and Ce onto titanium oxide particles. The honeycomb catalyst contains 20-35 wt% Mn in terms of MnOand 4.6-25 wt% Ce in terms of CeO, and a diffraction peak at 2θ=43.0±1° caused by MnOis not detected.SELECTED DRAWING: Figure 1

Description

The present invention relates to a honeycomb catalyst and a method for manufacturing a honeycomb catalyst.

As a system for purifying NOx in exhaust gas, an SCR (Selective Catalytic Reduction) system that uses ammonia to reduce NOx to nitrogen and water is known.
As a catalyst used in this SCR system, a TiO ₂ / V ₂ O ₅ / WO ₃ denitration catalyst is known.

The SCR system is also used to purify exhaust gas from a cement factory or the like.
In exhaust gas purification at cement factories, the exhaust gas contains a large amount of ash, so the denitration catalyst used for exhaust gas purification should be placed as far back as possible from the exhaust gas treatment device so that ash does not accumulate in the denitration catalyst. It is necessary to.
Therefore, the temperature of the exhaust gas in the denitration catalyst is as low as about 100 to 150 ° C.
However, it is difficult to improve the NOx purification performance at a low temperature with a denitration catalyst using a TiO ₂ / V ₂ O ₅ / WO ₃ type material.

Patent Document 1 discloses a catalyst in which manganese oxide and cerium oxide are supported on titanium dioxide as a denitration catalyst exhibiting a high NOx removal rate in a low temperature range.

JP-A-8-131828

Patent Document 1 describes a process in which cerium nitrate and manganese nitrate as raw materials are dissolved in water and kneaded with titanium oxide to obtain a catalyst raw material. In the examples, it is described that the diffraction peak of MnO ₂ is detected while being broad in XRD (X-ray crystal structure analysis).
The fact that a diffraction peak of MnO ₂ is detected in XRD indicates that large MnO ₂ crystal particles are formed in the catalyst raw material, and the catalyst is not uniformly dispersed.
If the catalyst is not uniformly dispersed, the NOx purification performance is lowered. In particular, in the low temperature region, the NOx purification performance declines significantly and becomes a problem.

The present invention has been made in view of the above-mentioned problems, and provides a honeycomb catalyst in which MnO ₂ is uniformly dispersed in a catalyst raw material and excellent in NOx purification performance at a low temperature, and the honeycomb It aims at providing the method of manufacturing a catalyst.

In order to solve the above-mentioned problems, the present inventor has made extensive investigations, and as a result, a predetermined amount of Mn and Ce is attached to titanium oxide, and MnO ₂ is not uniformly detected by XRD analysis. The present honeycomb catalyst was found to exhibit high NOx purification performance in a low temperature region, and the present invention was conceived.

That is, the honeycomb catalyst of the present invention is a honeycomb catalyst composed of ceramic particles in which Mn and Ce adhere to titanium oxide particles,
Mn is ₂₀ to 35% by weight in terms of MnO ₂ ,
Ce is contained from 4.6 to 25 wt% in terms of CeO _2,
In the XRD analysis, a diffraction peak of 2θ = 43.0 ± 1 ° due to MnO ₂ is not detected.

In the honeycomb catalyst of the present invention, Mn and Ce are attached to the titanium oxide particles.
The fact that Mn and Ce are attached to the titanium oxide particles means that the form of attachment is not limited as long as Mn and Ce are attached to the titanium oxide particles as elements. It is preferable that it adheres as an oxide.
The honeycomb catalyst of the present invention contains ₂₀ to 35% by weight of Mn in terms of MnO ₂ and 4.6 to 25% by weight of Ce in terms of CeO ₂ . When both the amount of Mn and the amount of Ce satisfy the above range, a honeycomb catalyst having high NOx purification performance at a low temperature can be obtained. If any of the amount of Mn and Ce is less than the above range, the NOx purification performance at low temperature is lowered. Moreover, when either of the amount of Mn and Ce is more than the said range, cost will become high too much.

Further, a diffraction peak due to MnO ₂ in an XRD analysis is not detected, diffraction 2θ = 25 ± 1 ° of the diffraction peak height of 2θ = 43.0 ± 1 ° due to MnO ₂ is due to TiO ₂ It means less than 1/20 with respect to the peak height.
The fact that a diffraction peak due to MnO ₂ is not detected in XRD analysis indicates that large crystal particles of MnO ₂ are not formed. In other words, Mn is uniformly dispersed and adhered to titanium oxide particles. It shows that. When Mn is uniformly dispersed, a honeycomb catalyst having high NOx purification performance at a low temperature can be obtained.

In the honeycomb catalyst of the present invention, the XRD analysis conditions are preferably as follows.
Scan axis: 2θ / θ, measurement method: continuous measurement, counting unit: cps, start angle: 10 °, end angle: 70 °, sampling width: 0.02 °, scan speed: 2 ° / min, voltage: 40 kV, Current: 20 mA, divergence slit: 2/3 °, divergence longitudinal restriction slit: 10 mm, scattering slit: 2/3 °, light receiving slit: 0.3 mm, offset angle: 0 °

The honeycomb catalyst of the present invention preferably has an aperture ratio of 40 to 85%.
When the aperture ratio is in the above range, the entire honeycomb catalyst can be effectively used for NOx purification, and a honeycomb structure having a particularly high NOx purification rate at a low temperature can be obtained.

The honeycomb catalyst of the present invention, it is preferable that Ce is contained from 9.2 to 25 wt% in terms of CeO _2.
When the amount of Ce is within the above range, a honeycomb structure having a higher NOx purification rate at a low temperature can be obtained.

The honeycomb catalyst of the present invention preferably further contains inorganic fibers and an inorganic binder.
By adhering the ceramic particles with an inorganic binder, the mechanical strength for maintaining the shape as the honeycomb catalyst is improved, and the reinforcing effect can be obtained by including inorganic fibers.

A method for manufacturing a honeycomb catalyst of the present invention includes a dispersion step of mixing titanium oxide particles, a Mn source, and a Ce source and dispersing in a solvent;
an adhesion step of obtaining a powder in which Mn and Ce are adhered to titanium oxide particles by adjusting the pH to 7.5 or more;
Heating the powder to obtain ceramic particles;
A step of obtaining a honeycomb catalyst by mixing the ceramic particles with a binder, forming and firing the mixture.

In the case of the above method, Mn and Ce are reliably attached to the titanium oxide particles particularly through the attaching step. And it can be set as the ceramic particle which Mn uniformly disperse | distributed to the titanium oxide atom, and adhered.
The honeycomb catalyst obtained by such a manufacturing method becomes a honeycomb catalyst excellent in NOx purification performance at a low temperature.

In the method for manufacturing a honeycomb catalyst of the present invention, it is preferable to adjust the pH to 7.5 to 10.0 in the adhesion step. By setting the pH to the alkali side, Mn ions can easily adhere to the titanium oxide particles, and Mn ions can be prevented from aggregating.
In the method for manufacturing a honeycomb catalyst of the present invention, it is preferable to adjust the pH by adding ammonium carbonate in the adhesion step. Since ammonium carbonate does not volatilize at room temperature, pH adjustment is facilitated.

FIG. 1 (a) is a perspective view schematically showing an example of the honeycomb catalyst of the present invention, and FIG. 1 (b) is a cross-sectional view taken along the line AA of the honeycomb catalyst shown in FIG. 1 (a). . FIG. 2 is a perspective view schematically showing an example of a honeycomb catalyst module including the honeycomb catalyst of the present invention.

(Detailed description of the invention)
Hereinafter, the present invention will be specifically described. However, the present invention is not limited to the following description, and can be appropriately modified and applied without departing from the scope of the present invention.

The honeycomb catalyst of the present invention is a honeycomb catalyst composed of ceramic particles in which Mn and Ce adhere to titanium oxide particles,
Mn is ₂₀ to 35% by weight in terms of MnO ₂ ,
Ce is contained from 4.6 to 25 wt% in terms of CeO _2,
In the XRD analysis, a diffraction peak of 2θ = 43.0 ± 1 ° due to MnO ₂ is not detected.

The honeycomb catalyst of the present invention is made of ceramic particles in which Mn and Ce adhere to titanium oxide particles.
Examples of the titanium oxide particles include anatase type, rutile type, amorphous type, and a mixture thereof, and anatase type titanium oxide particles are particularly preferable.

Each of Mn and Ce is preferably attached to the titanium oxide particles as an oxide.

The honeycomb catalyst of the present invention contains ₂₀ to 35% by weight of Mn in terms of MnO ₂ and 4.6 to 25% by weight of Ce in terms of CeO ₂ .
The content of Mn in terms of MnO ₂ is preferably 25 to 35% by weight. Further, the content of Ce in terms of CeO ₂ is preferably 9.2 to 25% by weight.
The contents of Mn and Ce in the honeycomb catalyst can be measured by ICP emission spectroscopy.

In the honeycomb catalyst of the present invention, a diffraction peak of 2θ = 43.0 ± 1 ° due to MnO ₂ is not detected in the XRD analysis.
This means that the diffraction peak height of 2θ = 43.0 ± 1 ° attributable to MnO ₂ is less than 1/20 with respect to the diffraction peak height of 2θ = 25 ± 1 ° attributable to TiO _2. To do.
This indicates that Mn is uniformly dispersed and adhered to the titanium oxide particles. When Mn is uniformly dispersed, a honeycomb catalyst having high NOx purification performance at low temperatures can be obtained. .

The honeycomb catalyst of the present invention preferably further contains inorganic fibers and an inorganic binder in addition to the ceramic particles.

The inorganic fiber is preferably at least one selected from the group consisting of alumina, silica, silicon carbide, silica alumina, glass, wollastonite, potassium titanate and aluminum borate. This is because all of them have high heat resistance, and even when used as a honeycomb catalyst, there is no melting damage and the effect as a reinforcing material can be maintained.
When the honeycomb catalyst of the present invention includes inorganic fibers, the content of inorganic fibers is preferably 3 to 15% by weight, and more preferably 4.5 to 15% by weight.

The inorganic binder is preferably at least one selected from the group consisting of alumina sol, silica sol, titania sol, water glass, sepiolite, attapulgite, bentonite and boehmite. By bonding the ceramic particles with an inorganic binder, the mechanical strength for maintaining the shape as the honeycomb catalyst is improved.
When the honeycomb catalyst of the present invention includes an inorganic binder, the content of the inorganic binder is preferably 3 to 15% by weight.

The honeycomb catalyst of the present invention is preferably formed by molding and firing the ceramic particles into a predetermined shape.
Hereinafter, examples of the shape of the honeycomb catalyst of the present invention will be described.
FIG. 1 (a) is a perspective view schematically showing an example of the honeycomb catalyst of the present invention, and FIG. 1 (b) is a cross-sectional view taken along the line AA of the honeycomb catalyst shown in FIG. 1 (a). .

In the honeycomb catalyst 10 shown in FIGS. 1A and 1B, the through holes 11 whose both ends are not sealed are separated by the partition wall 12 in the longitudinal direction (the direction of the double arrow a in FIG. 1A). ) And a single unit in which the outer peripheral wall 13 is formed on the outer periphery.

Therefore, the exhaust gas G (in FIG. 1 (b), flowing into one of the through holes 11 of the honeycomb catalyst 10 from one end (exhaust gas inflow side end) 14 is indicated by G, and the flow of the exhaust gas is indicated by an arrow. In some cases, the mixed gas G of the exhaust gas and a reducing agent such as ammonia comes into contact with the catalyst species when passing through the through-hole 11, thereby purifying NOx contained in the exhaust gas G. The The purified exhaust gas G is discharged from the other end (exhaust gas outflow side end) 15 of the through hole 11.
Thus, NOx in the exhaust gas can be suitably removed by using the honeycomb catalyst of the present invention.

The shape of the honeycomb catalyst of the present invention is not limited to a cylindrical shape, and may be a prismatic shape, an elliptical column shape, a long cylindrical shape, a rounded chamfered prismatic shape (for example, a rounded chamfered triangular prism shape), or the like. May be.

In the honeycomb catalyst of the present invention, the shape of the through hole is preferably a quadrangular prism shape, but may be a triangular prism shape, a hexagonal prism shape, or the like.

The honeycomb catalyst of the present invention preferably has an aperture ratio of 40 to 85%, more preferably 50 to 75%.
In the present specification, the aperture ratio of the honeycomb catalyst means an aperture ratio of a cross section perpendicular to the longitudinal direction.
When the aperture ratio is in the above range, the entire honeycomb catalyst can be effectively used for NOx purification, and a honeycomb structure having a particularly high NOx purification rate at a low temperature can be obtained.

The partition wall thickness of the honeycomb catalyst of the present invention is preferably 0.2 to 2.5 mm.
When the partition wall thickness is less than 0.2 mm, the honeycomb catalyst has insufficient strength. On the other hand, when the thickness of the partition wall exceeds 2.5 mm, the exhaust gas hardly enters the partition wall, so that the NOx purification performance decreases.

The thickness of the outer peripheral wall of the honeycomb catalyst of the present invention is preferably 0.3 to 3.0 mm.
When the thickness of the outer peripheral wall is less than 0.3 mm, the strength of the honeycomb catalyst is lowered and easily damaged by an external force. On the other hand, if the thickness of the outer peripheral wall exceeds 3.0 mm, the outer peripheral wall tends to be distorted when forming into a honeycomb shape.

The average pore diameter of the partition walls of the honeycomb catalyst of the present invention is preferably 0.01 to 0.5 μm.
When the average pore diameter of the partition walls of the honeycomb catalyst is less than 0.01 μm, the exhaust gas hardly enters the partition walls, so that the NOx purification performance decreases. On the other hand, when the average pore diameter of the partition walls of the honeycomb catalyst exceeds 0.5 μm, ash is accumulated in the pores of the honeycomb catalyst, and the NOx purification performance is lowered.
The average pore diameter of the partition walls of the honeycomb catalyst can be measured using a mercury intrusion method. The mercury contact angle is 130 ° and the surface tension is 485.25 mN / m.

The porosity of the partition walls of the honeycomb catalyst of the present invention is preferably 30 to 60%. If the porosity of the partition walls of the honeycomb catalyst is less than 30%, the exhaust gas does not easily enter the partition walls, and the NOx purification performance decreases. On the other hand, when the porosity of the partition walls of the honeycomb catalyst exceeds 60%, the strength of the honeycomb catalyst becomes insufficient.
Note that the porosity of the partition walls of the honeycomb catalyst can be measured by using Archimedes method.

Next, a method for manufacturing the honeycomb catalyst of the present invention will be described.
A method for manufacturing a honeycomb catalyst of the present invention includes a dispersion step of mixing titanium oxide particles, a Mn source, and a Ce source and dispersing in a solvent;
an adhesion step of obtaining a powder in which Mn and Ce are adhered to titanium oxide particles by adjusting the pH to 7.5 or more;
Heating the powder to obtain ceramic particles;
A step of obtaining a honeycomb catalyst by mixing the ceramic particles with a binder, forming and firing the mixture.
Hereinafter, each step will be described.

(1) Dispersing step In the mixing step, titanium oxide particles, a Mn source and a Ce source are mixed and dispersed in a solvent.
As the titanium oxide particles, it is preferable to use anatase-type titanium dioxide (TiO ₂ ) particles having a high specific surface area.
Examples of the Mn source include manganese nitrate, manganese acetate, manganese chloride, manganese sulfate and the like. Among these, manganese nitrate is preferable. As manganese nitrate, manganese nitrate (II) trihydrate, tetrahydrate, hexahydrate, manganese nitrate (III), or the like can be used.
Examples of the Ce source include cerium nitrate and cerium chloride. Among these, cerium nitrate is preferable, and cerium nitrate (III) hexahydrate or the like can be used as cerium nitrate.

In the dispersion step, titanium oxide particles, a Mn source, and a Ce source are mixed and dispersed in a solvent.
Titanium oxide particles, Mn source and Ce source may be charged into a solvent at once, or a dispersion in which titanium oxide particles are dispersed in a solvent and a solution in which Mn source and Ce source are dissolved in a solvent, respectively. It may be prepared and a Mn source-containing solution and a Ce source-containing solution may be added to the dispersion of titanium oxide particles.

Examples of the solvent include water, organic solvents such as benzene, alcohols such as methanol, and the like, and two or more kinds may be used in combination. Preferably it is water.

(2) Adhesion process In the adhesion process, the pH is adjusted to 7.5 or more, and Mn and Ce are adhered to the titanium oxide particles.
Since the dispersion prepared in the dispersion step is usually acidic, an alkali is added as a neutralizing agent, and Mn and Ce are deposited and adhered on the surface of the titanium oxide particles.
In the attaching step, it is preferable to adjust the pH to 7.5 to 10.0.
By performing this step, Mn and Ce, particularly Mn, are uniformly dispersed and adhered to the titanium oxide particles.

As the alkali as a neutralizing agent, ammonium carbonate, ammonia water or the like can be used. Of these, ammonium carbonate is preferred.
When adding the neutralizing agent, the neutralizing agent may be added while monitoring the pH using a pH meter, and the addition of the neutralizing agent may be stopped when the pH reaches the target value.
Moreover, it is preferable to perform stirring for 0.5 to 5 hours after addition of a neutralizing agent.

By adding a neutralizing agent, a dispersion liquid in which titanium oxide particles having Mn and Ce adhered thereto are dispersed in a solvent is obtained. Therefore, the dispersion liquid is filtered and dried, and powder in which Mn and Ce are adhered to titanium oxide particles. Get.
The drying conditions after filtration are preferably 80 to 150 ° C. and 1 to 12 hours.
Moreover, it is preferable to grind | pulverize the powder after drying as needed.

(3) Heating step In the heating step, the powder obtained in the above step is heated to obtain ceramic particles in which Mn and Ce adhere to titanium oxide particles.
The heating condition of the powder is preferably 300 to 500 ° C. and 0.5 to 2 hours.

(4) Step of obtaining a honeycomb catalyst Subsequently, a honeycomb catalyst is manufactured using the obtained ceramic particles.
First, ceramic particles, an inorganic binder, an organic binder, and inorganic fibers are mixed to prepare a kneaded product.

Examples of the inorganic binder include alumina sol, silica sol, titania sol, water glass, sepiolite, attapulgite, bentonite, and boehmite.

Examples of the organic binder include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyethylene glycol, phenol resin, and epoxy resin.

Examples of the inorganic fiber include alumina, silica, silicon carbide, silica alumina, glass, wollastonite, potassium titanate, and aluminum borate.
In addition, a lubricant, a dispersion medium, a molding aid, a pH adjuster, and the like may be appropriately added as necessary.
The lubricant is not particularly limited, and examples thereof include sorbitan trioleate.
Although it does not specifically limit as a dispersion medium, Alcohol, such as water, organic solvents, such as benzene, methanol, etc. are mentioned.

Although it does not specifically limit as a shaping | molding adjuvant, Ethylene glycol, dextrin, a fatty acid, fatty-acid soap, a polyalcohol etc. are mentioned.
Examples of the pH adjuster include aqueous ammonia and amine compounds.

When preparing the above-described raw material composition, it is preferable to mix and knead, and it may be mixed using a mixer, an attritor or the like, or may be kneaded using a kneader or the like.

Next, in the forming step, a columnar honeycomb formed body in which a plurality of through holes are juxtaposed in the longitudinal direction with a partition wall therebetween and an outer peripheral wall is formed on the outer periphery by extrusion molding using the raw material composition. Is made.
Thereafter, the honeycomb formed body is dried by using a dryer such as a microwave dryer, a hot air dryer, a dielectric dryer, a vacuum dryer, a vacuum dryer, a freeze dryer, or the like to produce a honeycomb dried body.

A columnar honeycomb catalyst is obtained by degreasing and firing the obtained honeycomb dried body. The degreasing and firing temperature is preferably 300 to 500 ° C. When the degreasing and firing temperature is less than 300 ° C., the amount of residual carbon in the organic component is excessive. On the other hand, when the degreasing and firing temperature exceeds 500 ° C., the reaction sites of the catalyst species decrease.

The honeycomb catalyst of the present invention is preferably used for exhaust gas treatment of a coal-fired power plant or a cement factory. In particular, it is preferably used for exhaust gas treatment where the temperature of the exhaust gas is low, and is preferably used for exhaust gas treatment where the temperature of the exhaust gas is 100 to 150 ° C.
When the honeycomb catalyst of the present invention is used, it is possible to efficiently purify NOx in low-temperature exhaust gas discharged from a coal-fired power plant or a cement factory.

The honeycomb catalyst of the present invention can be used singly according to the application, and a plurality of honeycomb catalysts can also be used as a honeycomb catalyst module.
For example, when the honeycomb catalyst is used as a denitration apparatus for a coal-fired power plant or a cement factory, the required size of the honeycomb catalyst is increased. Therefore, a method using a plurality of honeycomb catalysts has been adopted.

FIG. 2 is a perspective view schematically showing an example of a honeycomb catalyst module including the honeycomb catalyst of the present invention.
In the honeycomb catalyst module 100 shown in FIG. 2, a plurality of honeycomb catalysts 10 are aggregated to form an aggregate 40, and the aggregate 40 is accommodated inside a fixing tool 30 that forms the outer periphery of the honeycomb catalyst module 100. So that it is fixed.
When producing the aggregate 40, a plurality of honeycomb catalysts 10 may be temporarily fixed using an adhesive, a tape, or the like. In addition, it is preferable that the adhesive, the tape, and the like disappear due to the heat of the exhaust gas when the exhaust gas is processed using the denitration apparatus in which the honeycomb catalyst module 100 manufactured through the subsequent process is used. By using such an adhesive or a tape, the work of removing the adhesive or the tape can be omitted.
Further, when the aggregate 40 is produced, a blanket made of inorganic fibers may be interposed between the honeycomb catalysts 10.

The fixing tool 30 includes a plurality of plate-like members 31. The plurality of plate-like members 31 may be connected in any manner as long as the plurality of honeycomb catalysts 10 can be fixed, or may be connected by welding or connected by screws or the like. The fixing tool constituting the honeycomb catalyst module including the honeycomb catalyst of the present invention may have any shape as long as a plurality of honeycomb catalysts can be fixed. As such a fixing tool, for example, a plate-like metal connected by welding or a screw or a cylindrical casing can be cited. Further, a blanket made of inorganic fibers may be disposed in the gap between the honeycomb catalysts or in the gap between the honeycomb catalyst and the fixing tool.

A plurality of such honeycomb catalyst modules are usually arranged side by side inside the denitration apparatus. In the denitration apparatus, the exhaust gas is sent to the honeycomb catalyst module including the honeycomb catalyst of the present invention. The exhaust gas sent passes through the through holes of the honeycomb catalyst. Thereby, NOx in exhaust gas can be purified.
The means for sending the exhaust gas to the honeycomb catalyst module is not particularly limited, and it may be sent using a fan or the like, and the denitration device is designed so that the pressure of the exhaust gas becomes high so that the exhaust gas can be sent naturally to the honeycomb catalyst module. It may be.

By gathering a plurality of honeycomb catalysts of the present invention into a honeycomb catalyst module, the handleability of the honeycomb catalyst can be improved, and the working efficiency when manufacturing a denitration device comprising a plurality of honeycomb catalysts can be improved. .

(Example)
Hereinafter, examples in which the honeycomb catalyst of the present invention and the method for manufacturing the honeycomb catalyst of the present invention are disclosed more specifically will be shown. In addition, this invention is not limited only to these Examples.
Example 1
[1] Manufacture of ceramic particles (1) Dispersion process An anatase-type titanium dioxide powder is dispersed in water, and further an aqueous solution containing manganese (II) nitrate hexahydrate as a Mn source, and cerium (III) nitrate 6 water as a Ce source An aqueous solution containing a hydrate was mixed to obtain a dispersion in which titanium oxide particles, a Mn source, and a Ce source were dispersed in water.
The compounding amounts of the titanium oxide powder, the Mn source, and the Ce source were set so that the Mn content in terms of MnO ₂ and the Ce content in terms of CeO ₂ in the honeycomb catalyst were as shown in Table 1.

(2) Adhesion step Ammonium carbonate was added to the dispersion to adjust the pH to 8.5. Ammonium carbonate was added while stirring and monitoring the pH using a pH meter, and the addition of ammonium carbonate was stopped when the pH reached 8.5.
Subsequently, the dispersion was stirred at room temperature for 5 hours, filtered, dried at 120 ° C. for 12 hours, and further pulverized.
By the above procedure, a powder in which Mn and Ce were adhered to titanium oxide particles was obtained.

(3) Heating step The powder was heated at 400 ° C. for 2 hours to obtain ceramic particles.

[2] Manufacture of honeycomb catalyst (1) Preparation of kneaded material 54.8 parts by weight of ceramic particles obtained in the above step, 3.7 parts by weight of alumina sol as inorganic binder, 2.1 parts by weight of glass fiber as inorganic fiber, organic 4.5 parts by weight of methylcellulose as a binder, 2.6 parts by weight of sorbitan trioleate as a lubricant, and 32.2 parts by weight of ion-exchanged water were mixed and kneaded to prepare a kneaded product.

(2) Forming Step Next, the kneaded product was extruded to a predetermined size using an extruder, and a regular quadrangular prism-shaped honeycomb formed body was manufactured. Then, the honeycomb molded body was dried at a drying pressure of 86.7 kPa for 6 minutes using a batch microwave dryer to obtain a honeycomb dried body.

(3) Firing step Thereafter, the dried honeycomb body is put into a gas flow furnace, heated to 400 ° C. at a heating rate of 1 ° C./min, and fired while maintaining the temperature for 2 hours to produce a honeycomb fired body. did.
The manufactured honeycomb fired body is the honeycomb catalyst of Example 1.

The honeycomb catalyst according to Example 1 was a regular square column shape of 37.0 mm square × length 76.2 mm, and the cell density was 7.3 cells / cm ² (47 cpsi).
The partition wall thickness was 0.71 mm (28 mil), and the aperture ratio was 65.8%.

Table 1 shows the amount of Mn converted to MnO _{2 and} the amount of Ce converted to CeO ₂ in the honeycomb catalyst.
In Example 1, the amount of Mn in the honeycomb catalyst is 23% by weight, and the amount of Ce is 4.6% by weight.

(Examples 2 and 3, Comparative Examples 1 to 9)
Example 1 except that the blending amounts of titanium dioxide powder, Mn source, and Ce source were changed so that the Mn content in terms of MnO ₂ and the Ce content in terms of CeO ₂ in the honeycomb catalyst were the values shown in Table 1. A honeycomb catalyst was manufactured in the same manner as described above.

(Examples 4 and 5)
Using the ceramic particles having the composition of Example 2, a honeycomb catalyst was manufactured by changing the opening ratio by changing the partition wall thickness and cell density.
In Example 4, the partition wall thickness was 1.24 mm (49 mil), the cell density was 7.1 cells / cm ² (46 cpsi), and the aperture ratio was 44.5%.
In Example 5, the partition wall thickness was 0.76 mm (30 mil), the cell density was 2.0 cells / cm ² (13 cpsi), and the aperture ratio was 79.4%.

(Comparative Example 10)
The amount of manganese nitrate (II) 6 hydrate Mn content of MnO ₂ in terms of 15% by weight in the ceramic particles are dissolved in water, titanium dioxide powder, an inorganic binder, an organic binder, inorganic fibers, lubricants Then, it was mixed, kneaded and molded with water to obtain a honeycomb molded body.
This honeycomb formed body was heated at 400 ° C. for 2 hours to produce a honeycomb catalyst.
The amount of Mn in terms of MnO ₂ in the honeycomb catalyst is 13.8% by weight.

(XRD analysis)
A part of the honeycomb catalyst manufactured in each example and each comparative example was broken to a size capable of XRD analysis, and XRD analysis was performed to confirm whether a diffraction peak due to MnO ₂ was detected.
XRD analysis was performed using Rigaku Ultima IV.
The conditions for XRD analysis are as follows. Scan axis: 2θ / θ, measurement method: continuous measurement, counting unit: cps, start angle: 10 °, end angle: 70 °, sampling width: 0.02 °, scan speed: 2 ° / min, voltage: 40 kV, Current: 20 mA, divergence slit: 2/3 °, divergence longitudinal restriction slit: 10 mm, scattering slit: 2/3 °, light receiving slit: 0.3 mm, offset angle: 0 °
In Table 1, in the column of “MnO ₂ detection”, the case where a diffraction peak due to MnO ₂ is detected is indicated as “Yes”, and the case where it is not detected is indicated as “No”.

(NOx purification rate evaluation)
From the honeycomb catalyst manufactured in each Example and each Comparative Example, a square prism-shaped test piece having a side of 35 mm and a length of 40 mm was cut out using a diamond cutter. The test gas was discharged from the sample using a catalyst evaluation apparatus (SIGU-2000 / MEXA-1170NX, manufactured by Horiba, Ltd.) while flowing a simulated gas at 120 ° C. through these test pieces at a space velocity (SV) of 5,000 / hr. The NOx outflow amount was measured, and the NOx purification rate (%) represented by the following formula (1) was calculated.
The measurement point of the NOx purification rate was the saturation point of the outlet concentration of N ₃ H and NOx.
(NOx inflow amount−NOx outflow amount) / (NOx inflow amount) × 100 (1)
The constituent components of the simulated gas are 200 ppm nitrogen monoxide, 240 ppm ammonia, 2% oxygen, 10.0% water, and nitrogen (Balance). The results are shown in Table 1.

As shown in Table 1, the honeycomb catalyst according to each example in which the amount of Mn and the amount of Ce satisfy the ranges defined in the present invention and MnO ₂ is not detected in the XRD analysis has a high NOx purification rate at a low temperature (120 ° C.). It was. Although the honeycomb catalyst of Example 5 had a high aperture ratio of 79.4%, the NOx purification rate showed a high value of 30.0%.
On the other hand, the honeycomb catalysts according to Comparative Examples 1 to 9 in which the amount of Mn or Ce did not satisfy the range defined in the present invention had a low NOx purification rate at a low temperature (120 ° C.).
Further, the honeycomb catalyst according to Comparative Example 10 in which MnO ₂ was detected in XRD analysis had a lower NOx purification rate at a lower temperature (120 ° C.) than that of Comparative Example 2 having the same composition ratio.
In the honeycomb catalyst according to Comparative Example 10, since the ceramic particles are manufactured without performing the adhesion process after kneading the raw materials, large MnO ₂ crystal particles are formed in the catalyst raw materials, and the catalyst is uniformly dispersed. It is estimated that the NOx purification rate is low because it is not made.

DESCRIPTION OF SYMBOLS 10 Honeycomb catalyst 11 Through-hole 12 Partition 13 Outer wall 14 and 15 End

Claims (8)

A honeycomb catalyst comprising ceramic particles in which Mn and Ce adhere to titanium oxide particles,
Mn is ₂₀ to 35% by weight in terms of MnO ₂ ,
Ce is contained from 4.6 to 25 wt% in terms of CeO _2,
A honeycomb catalyst, wherein a diffraction peak of 2θ = 43.0 ± 1 ° due to MnO ₂ is not detected in XRD analysis. The honeycomb catalyst according to claim 1, wherein the measurement conditions of the XRD analysis are the following conditions.
Scan axis: 2θ / θ, measurement method: continuous measurement, counting unit: cps, start angle: 10 °, end angle: 70 °, sampling width: 0.02 °, scan speed: 2 ° / min, voltage: 40 kV, Current: 20 mA, divergence slit: 2/3 °, divergence longitudinal restriction slit: 10 mm, scattering slit: 2/3 °, light receiving slit: 0.3 mm, offset angle: 0 ° The honeycomb catalyst according to claim 1 or 2, wherein the opening ratio is 40 to 85%. Ce honeycomb catalyst according to claim 1 that contains from 9.2 to 25 wt% in terms of CeO _2. Furthermore, the honeycomb catalyst in any one of Claims 1-4 containing an inorganic fiber and an inorganic binder. A dispersion step of mixing titanium oxide particles, Mn source and Ce source and dispersing in a solvent;
an adhesion step of obtaining a powder in which Mn and Ce are adhered to titanium oxide particles by adjusting the pH to 7.5 or more;
Heating the powder to obtain ceramic particles;
And a step of obtaining a honeycomb catalyst by mixing the ceramic particles with a binder and then forming and firing the mixture. The method for manufacturing a honeycomb catalyst according to claim 6, wherein the pH is adjusted to 7.5 to 10.0 in the attaching step. The method for manufacturing a honeycomb catalyst according to claim 6 or 7, wherein the pH is adjusted by adding ammonium carbonate in the attaching step.

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