JP7143682B2 - Cerium-containing delta-type manganese dioxide monodisperse particles and method for producing the same - Google Patents

Description

The present invention relates to cerium-containing delta-type manganese dioxide monodisperse particles and a method for producing the same.

It has been reported that a mixture of manganese dioxide particles and cerium oxide particles is effective as a technique for oxidizing and detoxifying formaldehyde in the air (Patent Document 1).

On the other hand, a technique has been reported in which cerium ion exchange is performed on delta-type manganese dioxide in an acidic to neutral liquid (Patent Document 2). This reaction has been applied to the heptane oxidation reaction. This patent document requires that the cerium component of the manganese component be dispersed relatively uniformly and that the alkali metal content be 0.05 or less in terms of manganese molar ratio.

Moreover, there is a report that a mixture of cerium hydroxide, manganese dioxide, and silver phosphate is effective as an adsorbent for radioactive metals (Patent Document 3). The content of cerium hydroxide is described as at least 90 wt% or more.

JP-A-2000-79157 JP-A-57-12828 JP 2017-116407 A

Regarding the physical mixture of manganese dioxide and cerium oxide of Patent Document 1, the catalytically active site is considered to be the interface between manganese dioxide and cerium oxide. It is expected to be easy to manufacture, but since it is a mixture of two types of particles, the reaction area of the active sites can be considered limited. It is considered preferable that the cerium and manganese components be dispersed at the atomic or nano level.

Moreover, the cerium ion-exchanged delta-type manganese dioxide of Patent Document 2 needs to be ion-exchanged mainly with an acidic cerium aqueous solution after obtaining the delta-type manganese dioxide containing an alkali metal. In addition, it is expected that multiple ion exchanges will be required in order to make the sodium manganese molar ratio 0.05 or less. From the above, it is clear that the manufacturing process is complicated.

Patent document 3 uses a mixture of manganese oxide and cerium oxide as a radioactive metal adsorbent, but since cerium is the main component, there is a problem that the cost of the adsorbent is high.

The present invention solves these problems and provides cerium-containing delta-type manganese dioxide monodisperse particles in which manganese and cerium are dispersed at the atomic or nano level, which are typical requirements for environmental purification materials for formaldehyde removal. With the goal.

The present inventors have extensively studied catalysts, metal ion adsorption properties, and production methods of cerium-containing delta-type manganese dioxide monodisperse particles.

That is, a mixture of cerium oxide and manganese dioxide exhibits catalytic performance, but does not have sufficient performance because it is an interfacial reaction between cerium oxide and manganese dioxide. In response to these problems, manganese and cerium are used as essential components, and high dispersion control at the atomic or nano level has led to the realization of excellent catalytic performance. In addition, by making the crystal structure delta type, it is possible to adsorb and remove metal ions by fixing the sodium component, which may be a catalyst poison, between the crystal layers, suppressing the surface abundance, and providing ion exchange capacity. and

As for the method for producing the cerium-containing delta-type manganese dioxide, conventionally known methods include a method in which delta-type manganese dioxide is once prepared and then ion-exchanged with an acidic cerium solution. However, the production process is likely to be more expensive and complicated than the one-step reaction crystallization. Furthermore, since monodisperse particles are obtained according to the production method of the present invention, it is extremely advantageous for the powder production process.

Based on the above results, the inventor has completed the present invention. That is, the present invention contains cerium at a metal molar ratio of 3% or more and 25% or less, has a delta crystal structure, has a BET specific surface area of 50 m ² /g or more and 150 m ² /g or less, and has an average particle diameter of 3 μm or more and 30 μm or less, and a monomodal in which the peak intensity ratio of the cumulative 10% and 90% particle diameters to the peak intensity of the particle diameter showing the maximum frequency in the volume particle size distribution measurement is 0.5 or less. Cerium-containing delta-type manganese dioxide monodisperse particles characterized by having a uniform particle size distribution, and a method for producing the same.

The present invention will be described in detail below.

The cerium-containing delta-type manganese dioxide monodisperse particles of the present invention contain cerium in a metal molar ratio of 3% to 25%. When cerium is contained in a metal molar ratio of 3% or more and 25% or less, excellent catalyst or adsorption performance is exhibited. In addition, metals other than manganese, cerium, and sodium may be contained within the range in which the delta-type manganese dioxide structure is maintained. Examples include potassium, magnesium, calcium, strontium, barium, titanium, iron, cobalt, nickel, copper, zinc, zirconium and aluminum.

A delta-type manganese dioxide structure is essential as the crystal structure of the cerium-containing delta-type manganese dioxide monodisperse particles of the present invention. Unlike tunnel structures such as alpha, beta, and gamma types, the delta type has a layered structure, so it has a high ion exchange capacity and tends to fix sodium between crystal layers more easily than other crystal structures. In this case sodium exists between the layers of the MnO ₆ sheets and cerium exists both between the layers or in the MnO ₆ sheets. A delta-type structure is optimal for highly dispersing cerium, imparting ion-exchange ability, and suppressing the amount of sodium on the particle surface.

It is essential that the cerium-containing delta-type manganese dioxide monodisperse particles of the present invention have a BET specific surface area of 50 m ² /g or more and 150 m ² /g or less. If the BET specific surface area is less than 50 ^{m 2} /g, it is disadvantageous for gas adsorption or oxidation and metal ion adsorption. Adsorption performance decreases. It is preferably 60 m ² /g or more and 120 m ² /g or less. In general, catalytic activity, adsorption performance, and specific surface area are closely related, so a catalyst or adsorbent with a high specific surface area is more likely to be obtained with high activity.

The cerium-containing delta-type manganese dioxide monodisperse particles of the present invention must have an average particle diameter of 3 μm or more and 30 μm or less when being slurry and applied to a structure such as a honeycomb. If it is 3 μm or less, the slurry may increase in viscosity, or filtration after particle crystallization may be hindered. On the other hand, if it exceeds 30 μm, particle sedimentation becomes apparent during slurry preparation, making it difficult to prepare a uniform slurry. 3 μm or more and 10 μm or less is preferable. In addition, the average particle size is the average particle size of secondary particles obtained by aggregating primary particles, that is, the so-called agglomerated particle size.

Regarding the particle size distribution of the cerium-containing delta-type manganese dioxide monodisperse particles of the present invention, the peak intensity ratio of the cumulative 10% and 90% particle size to the peak intensity of the particle size showing the maximum frequency in volume particle size distribution measurement It is necessary to have a monomodal particle size distribution in which is 0.5 or less. Having such a monomodal particle size distribution is advantageous because it improves filterability and flowability of particles, and can suppress clogging of pipes and adhesion of particles in the manufacturing process.

A specific chemical composition of the cerium-containing delta-type manganese dioxide monodisperse particles of the present invention is, for example, Na:Ce:Mn (molar ratio)=0.15:0.07:0.78, 0.15:0. 0.03:0.82, 0.15:0.15:0.70, 0.00:0.08:0.92, 0.00:0.20:0.80 and the like.

The cerium-containing delta-type manganese dioxide monodisperse particles of the present invention can contain sodium between crystal layers. In order to obtain highly dispersed cerium and manganese at the atomic or nano level, it is preferable to prepare a coprecipitate by the neutralization reaction that is characteristic of the production method of the present invention. In this case, as an alkali, an aqueous caustic soda solution is the least expensive agent, but there is a concern that alkalis such as sodium may lead to deterioration in performance. However, in the present invention, since sodium, which is an alkaline component, is fixed between crystal layers, the probability of it existing on the surface is low. Therefore, excellent catalytic performance can be exhibited even if sodium is contained. The metal molar ratio of sodium is preferably 10% or more and 25% or less, more preferably 15% or more and 20% or less. Since the ion exchange capacity and the catalyst performance are in a trade-off relationship depending on the amount of sodium, it can be said that the optimum amount of sodium is in the range of 10% or more and 20% or less in terms of metal molar ratio.

Next, the method for producing the cerium-containing delta-type manganese dioxide monodisperse particles of the present invention will be described.

In the method for producing cerium-containing delta-type manganese dioxide monodisperse particles of the present invention, an aqueous solution containing at least manganese, cerium and sulfate ions is mixed with an alkaline aqueous solution and peroxodisulfate as an oxidizing agent for crystallization, followed by filtration. , washed and dried.

The aqueous solution containing manganese, cerium and sulfate ions used in the method for producing cerium-containing delta-type manganese dioxide monodisperse particles of the present invention dissolves sulfates, nitrates, acetates, etc. containing manganese and cerium as metal salts. and an aqueous solution obtained by dissolving manganese and cerium in inorganic acids such as sulfuric acid, nitric acid and acetic acid. An aqueous solution containing manganese sulfate and cerium sulfate can be exemplified as a preferable metal raw material. The cerium valence of cerium sulfate is III or IV, or a mixture thereof. Moreover, metal sulfate, sulfuric acid, ammonium sulfate, etc. can be mentioned as a raw material of a sulfate ion.

Moreover, the ratio of manganese and cerium in the aqueous solution may be adjusted to the ratio of manganese and cerium in the target cerium-containing manganese dioxide. Furthermore, when the metal molar ratio of cerium is 3% or more and 25% or less, the performance as an oxidation catalyst can be improved.

The total concentration of all metals of manganese and cerium in the aqueous solution (metal concentration) is arbitrary, but is preferably 0.5 mol/L or more, more preferably 1.0 mol/L or more, in order to improve productivity.

The alkaline aqueous solution preferably contains an alkali metal such as sodium hydroxide (caustic soda). Alkaline aqueous solutions that do not contain metals can also be used, such as ammonia water and non-metallic alkaline aqueous solutions such as amines. Among them, caustic soda aqueous solution is most preferable. As the concentration of caustic soda, 5% by weight or more and 20% by weight or less can be exemplified.

In order to obtain the desired cerium-containing delta-type manganese dioxide monodisperse particles, peroxodisulfate is essential as an oxidizing agent. Examples of peroxodisulfates include sodium salts (sodium peroxodisulfate) and ammonium salts (ammonium peroxodisulfate). The peroxodisulfate can be mixed as an aqueous solution in the same manner as an aqueous metal salt solution or an alkaline aqueous solution containing no metals. The concentration at that time can be exemplified from 3% by weight to 50% by weight.

By mixing an aqueous solution containing manganese, cerium and sulfate ions, an alkaline aqueous solution and an aqueous peroxodisulfate solution as an oxidizing agent, the cerium-containing delta-type manganese dioxide monodisperse particles of the present invention can be obtained.

The pH of the liquid during crystallization is not particularly limited as long as the crystallization can achieve the target metal composition, but in order to obtain more uniform particles, the pH of the liquid is preferably higher than 9.0 and lower than 10.0.
The temperature at which the aqueous solution containing manganese, cerium and sulfate ions, the alkaline aqueous solution containing no metal and the oxidizing agent are mixed is preferably a low temperature of 10° C. or higher and 39° C. or lower. By setting the temperature to 10° C. or higher, reprecipitation of the metal salt in the raw material metal salt aqueous solution is prevented. Further, when using ammonia, which is used as an alkaline aqueous solution, since the boiling point is low, it is possible to suppress the vapor pressure as much as possible and use it efficiently by keeping the liquid temperature at 39° C. or lower.

The method for producing cerium-containing delta-type manganese dioxide monodisperse particles of the present invention does not require atmosphere control and can be carried out in a normal atmospheric atmosphere.

If cerium-containing delta-type cerium-containing manganese dioxide monodisperse particles are obtained, the production can be performed either batchwise or continuously. Mixing time is arbitrary in the case of batch type. Examples include 3 to 48 hours, and further 6 to 24 hours. On the other hand, in the case of the continuous type, the average residence time of the delta-type cerium-containing manganese dioxide monodisperse particles in the reaction vessel is preferably 1 to 30 hours, more preferably 3 to 20 hours.

In the method for producing monodisperse cerium-containing delta-type manganese dioxide particles of the present invention, the cerium-containing delta-type manganese dioxide monodisperse particles are crystallized, followed by filtration, washing and drying.

Filtration is a general solid-liquid separation operation, and there is no particular limitation.

In the washing, impurities adhering to and adsorbed to the cerium-containing delta-type manganese dioxide monodisperse particles are removed. As a washing method, for example, a method of adding cerium-containing delta-type manganese dioxide monodisperse particles to water (eg, pure water, tap water, river water, etc.) and washing the same can be exemplified.

Drying removes water from the cerium-containing delta-type manganese dioxide monodisperse particles. Examples of the drying method include drying the cerium-containing delta-type manganese dioxide monodisperse particles at 110 to 150° C. for 2 to 15 hours. Although there are no particular restrictions on the drying atmosphere, it is preferable to use the air for convenience.

In the method for producing cerium-containing delta-type manganese dioxide monodisperse particles of the present invention, pulverization may be performed after drying.

In pulverization, a powder having an average particle size suitable for the application is obtained. Pulverization conditions are arbitrary as long as the desired average particle size is obtained. For example, wet pulverization, dry pulverization, or the like can be used.

The cerium-containing delta-type manganese dioxide monodisperse particles of the present invention can be used as an oxidation catalyst, particularly as an environmental purification catalyst. In addition, it can also be used as a metal adsorbent utilizing the ion-exchange property characteristic of delta-type manganese dioxide. Furthermore, it can also be used as an electrode catalyst for oxygen reactions.

Since the cerium-containing delta-type manganese dioxide monodisperse particles of the present invention are delta-type manganese dioxide having a high specific surface area and ion exchange ability, they exhibit excellent performance as catalysts and adsorbents. In addition, since it has an extremely uniform particle size, it is suitable for producing slurry and moldings.

1 is an XRD pattern of the manganese-based composite oxide of Example 1. FIG. 2 is a particle size distribution curve of the manganese-based composite oxide of Example 1. FIG. 1 is a scanning electron microscope image of a manganese-based composite oxide of Example 1. FIG. 4 is an XRD pattern of the manganese-based composite oxide of Example 2. FIG. 4 is a particle size distribution curve of the manganese-based composite oxide of Example 2. FIG. 4 is a scanning electron microscope image of the manganese-based composite oxide of Example 2. FIG. 4 is an XRD pattern of manganese oxide of Comparative Example 1. FIG. 4 is a particle size distribution curve of manganese oxide of Comparative Example 1. FIG. 4 is a scanning electron microscope image of manganese oxide of Comparative Example 1. FIG.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

<Measurement of chemical composition>
Composition analysis of the obtained sample was performed by inductively coupled plasma emission spectrometry (ICP method). Specifically, a sample powder, hydrogen peroxide solution, and hydrofluoric acid were dissolved under pressure to prepare a measurement solution. The chemical composition of the obtained sample was analyzed by measuring the obtained measurement solution using a general inductively coupled plasma emission spectrometer (trade name: OPTIMA3000DV, manufactured by PERKIN ELMER).

<Powder X-ray diffraction measurement>
Using a general X-ray diffractometer (trade name: Ultima4, manufactured by Rigaku), the obtained sample was subjected to powder X-ray diffraction measurement. CuKα rays (λ = 1.5405 Å) were used as the radiation source, the measurement mode was step scan, the scan conditions were 0.04° per second, the measurement time was 0.25 seconds, and the measurement range was 2θ from 10° to 90°. measured in range.

<Measurement of BET specific surface area>
Using a fluid type specific surface area automatic measuring device (trade name: Flowsorb 3-2305, manufactured by Micrometrics), 1.0 g of the obtained sample was pretreated in a nitrogen stream at 150 ° C. for 1 hour, and then absorbed by the BET 1-point method. After measuring the desorption area, the BET specific surface area (m ² /g) was obtained by dividing by the weight.

<Measurement of particle size distribution>
The particle size distribution of the samples was measured as follows. 0.5 g of the sample was put into 50 mL of 0.1N-ammonia water and subjected to ultrasonic irradiation for 10 seconds to form a dispersion slurry. A predetermined amount of the dispersed slurry was put into a laser diffraction particle size distribution analyzer (trade name: Microtrack HRA, manufactured by HONEWELL), and volume distribution was measured by a laser diffraction method. From the obtained volume distribution, the volume particle size was obtained and the particle size distribution was evaluated.

<Formaldehyde removal test>
As a formaldehyde adsorbent, 1 g of a sample was sealed in a Tedlar bag and degassed under reduced pressure, and then 1 L of 6.8 ppm (volumetric concentration) formaldehyde gas was injected. After standing at room temperature for 2 hours, the gas in the Tedlar bag was adsorbed on a cartridge carrying 2,4-dinitrophenylhydrazine (DNPH) (trade name: Presep-C DNPH, manufactured by Wako Pure Chemical Industries). The DNPH-aldehyde condensate is eluted from this cartridge (eluent = acetonitrile), and the DNPH-aldehyde condensate in the eluate is quantified by liquid chromatography (trade name: Agilent 1220 Infinity LC, manufactured by Agilent Technologies) and remains. Formaldehyde concentration was calculated.

<Measurement of strontium adsorption amount>
Using an artificial seawater reagent (trade name: Marine Art SF-1, manufactured by Tomita Seiyaku Co., Ltd.) for testing and research, an aqueous solution to be treated (hereinafter referred to as "simulated seawater") containing the same components as seawater was prepared. The simulated seawater contains strontium at a concentration of 7 ppm.

To 25 mL of simulated seawater was added 0.05 g of adsorbent sample. An adsorption test was conducted by stirring this at a temperature of 25° C. for 24 hours.

The strontium concentration in the aqueous sample solution was measured by inductively coupled plasma emission spectrometry (ICP method). A general inductively coupled plasma emission spectrometer (trade name: OPTIMA3000DV, manufactured by Perkin Elmer) was used for the measurement, and the strontium concentration was obtained by measuring the obtained measurement solution.

The strontium concentration of the simulated seawater before the adsorption test is C ₀ (mg/L), the simulated seawater after the adsorption test is C ₀ (mg/L), and the weight of the adsorbent sample is W (g). It was obtained by the formula.

Strontium adsorption amount (mg/g) = (C ₀ -C)/W
Example 1
Manganese sulfate and cerium sulfate were dissolved in pure water to form an aqueous solution containing manganese, cerium and sulfate ions at a Mn:Ce molar ratio of 9:1 (the total concentration of all metals in the aqueous solution was 2.0 mol/L). Manganese sulfate and cerium sulfate were both special grade reagents (manufactured by Kishida Chemical Co., Ltd.).

The aqueous solution was added to the reactor at a feed rate of 0.5 g/min. Further, a 40 wt % sodium peroxodisulfate aqueous solution was bubbled into the reaction vessel as an oxidizing agent at a supply rate of 0.45 g/min. When supplying the raw material liquid, a 10% by weight aqueous solution of caustic soda was intermittently added so that the pH became 9.5, and the coprecipitate was crystallized to obtain a slurry. The mixing temperature at this time was 20°C. After filtering and washing the resulting slurry, the washed wet cake was dried at 150° C. for 10 hours to obtain a manganese-based composite oxide.

The resulting sample was found to have Na:Ce:Mn (molar ratio) = 0.15:0.07:0.78 from the results of composition analysis.

FIG. 1 shows the XRD pattern of the obtained sample. The XRD peaks could be indexed as a δ-MnO ₂ -type structure with a layered structure.

In addition, it was found that the BET specific surface area of the manganese-based composite oxide was as high as 112 m ² /g.

The particle size distribution curve of the obtained sample is shown in FIG. 2, and the scanning electron microscope image is shown in FIG. The average particle size is 17.2 μm, and the peak intensity ratios of the cumulative 10% and 90% particle sizes to the peak intensity of the particle size showing the maximum frequency in volume particle size distribution measurement are 0.243 and 0.412, respectively. there were. The results regarding particle size distribution are shown in Table 1.

From the above results, it was found that the manganese-based composite oxide was cerium-containing delta-type manganese dioxide monodisperse particles.

Table 2 shows the results of the formaldehyde adsorption test. When the manganese-based composite oxide was used as an adsorbent, the formaldehyde concentration was remarkably lowered, confirming that it exhibits good adsorption properties.

Moreover, the measurement result of the strontium adsorption amount was 1.1 mg/g. It was confirmed that when the manganese-based composite oxide was used as an adsorbent, it exhibited good adsorption properties for strontium in seawater.

Example 2
Synthesis was carried out in the same manner as in Example 1 except that 10 wt % ammonia water was used instead of caustic soda and 40 wt % ammonium peroxodisulfate was used instead of the aqueous sodium peroxodisulfate solution to obtain a manganese-based composite oxide.

The obtained sample was found to have Na:Ce:Mn (molar ratio) = 0.00:0.08:0.92 from the result of composition analysis.

FIG. 4 shows the XRD pattern of the obtained sample. The intensity of the 001 and 002 diffraction peaks was lower than that of Example 1, but the other diffraction peaks were the same as those of Example 1. It is considered that the peak intensity of the 00L peak (L=1, 2) decreased because cerium, which has a relatively large X-ray atomic scattering factor, was present between the crystal layers. Therefore, the manganese-based composite oxide also had a δ-MnO ₂ type structure.

In addition, it was found that the BET specific surface area of the manganese-based composite oxide was as high as 67.3 m ² /g.

The particle size distribution curve of the obtained sample is shown in FIG. 5, and the scanning electron microscope image is shown in FIG. The average particle diameter is 26.8 μm, and the peak intensity ratios of the cumulative 10% and 90% particle diameters to the peak intensity of the particle diameter showing the maximum frequency in the volume particle diameter distribution measurement are 0.394 and 0.413, respectively. there were. The results regarding particle size distribution are shown in Table 1.

From the above results, it was found that the manganese-based composite oxide was cerium-containing delta-type manganese dioxide monodisperse particles.

Table 2 shows the results of the formaldehyde adsorption test. When the manganese-based composite oxide was used as an adsorbent, the formaldehyde concentration decreased, confirming that it exhibits good adsorption properties.

Moreover, the measurement result of the strontium adsorption amount was 0.46 mg/g. It was confirmed that when the manganese-based composite oxide was used as an adsorbent, it exhibited good adsorption properties for strontium in seawater.

Comparative example 1
Manganese sulfate was dissolved in pure water to obtain a 2.0 mol/L manganese sulfate aqueous solution. Manganese sulfate was a reagent special grade (manufactured by Kishida Chemical Co., Ltd.).

The aqueous solution was added to the reactor at a feed rate of 0.5 g/min. Further, a 40 wt % ammonium peroxodisulfate aqueous solution was bubbled into the reaction vessel as an oxidizing agent at a supply rate of 0.45 g/min. When the raw material liquid was supplied, 10% by weight aqueous ammonia was intermittently added to the raw material liquid so that the pH became 9.5, and the manganese oxide was crystallized to obtain a slurry. The mixing temperature at this time was 20°C. After filtering and washing the resulting slurry, the washed wet cake was dried at 150° C. for 10 hours to obtain manganese oxide.

FIG. 7 shows the XRD pattern of the obtained sample. The XRD peaks can be indexed as a δ-MnO ₂ -type structure with a layered structure.

Moreover, it was found that the BET specific surface area of the manganese oxide was sufficiently high as 69.9 m ² /g.

The particle size distribution curve of the obtained sample is shown in FIG. 8, and the scanning electron microscope image is shown in FIG. The average particle diameter was 122 μm, and the peak intensity ratios of the cumulative 10% and 90% particle diameters to the peak intensity of the particle diameter showing the maximum frequency in the volume particle diameter distribution measurement were 0.391 and 0.380, respectively. . The results regarding particle size distribution are shown in Table 1.

Comparative example 2
Table 2 shows the results of a formaldehyde adsorption test conducted in the same manner as in Example 1 except that silica gel (product name: PSQ60B, manufactured by Fuji Silysia Ltd.) was used as the formaldehyde adsorbent.

As is clear from Examples 1 and 2 and Comparative Example 2, the cerium-containing delta-type manganese dioxide monodisperse particles of the present invention exhibited higher formaldehyde adsorption performance than existing formaldehyde adsorbents.

The cerium-containing delta-type manganese dioxide monodisperse particles of the present invention can be used as adsorbents for environmental purification, oxidation catalysts and batteries, and electrode catalysts for electrolysis. In particular, it can be used as a purification catalyst for household odors containing formaldehyde, acetaldehyde, and the like.

Claims (5)

It contains cerium at a metal molar ratio of 3% or more and 25% or less, has a delta crystal structure, has a BET specific surface area of 50 m ² /g or more and 150 m ² /g or less, and has an average particle diameter of 3 μm or more and 30 μm or less. and having a monomodal particle size distribution in which the peak intensity ratio of the cumulative 10% and 90% particle sizes to the peak intensity of the particle size showing the maximum frequency in volume particle size distribution measurement is 0.5 or less. Cerium-containing delta-type manganese dioxide monodisperse particles characterized by: 2. The cerium-containing delta-type manganese dioxide monodisperse particles according to claim 1, containing sodium between crystal layers and having a metal molar ratio of 10% to 25%. According to claim 1 or 2, obtained by mixing an aqueous solution containing manganese, cerium and sulfate ions with an alkaline aqueous solution and peroxodisulfate to crystallize, followed by filtration, washing and drying. A method for producing the cerium-containing delta-type manganese dioxide monodisperse particles described above. 4. The method for producing cerium-containing delta-type manganese dioxide monodisperse particles according to claim 3, wherein the pH of the liquid during crystallization is higher than 9.0 and lower than 10.0. 5. The method for producing cerium-containing delta-type manganese dioxide monodisperse particles according to claim 3 or claim 4, wherein the liquid temperature during crystallization is 10°C or higher and 39°C or lower.

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