Intermediate for producing heterometal-doped cerium oxide, method for producing the same, and heterometal-doped cerium oxide using the same

Abstract

To provide an intermediate for producing a dissimilar-metal doped cerium oxide, a method for producing the same, and a dissimilar-metal doped cerium oxide using the same, wherein the dissimilar-metal doped cerium oxide is excellent in uniformity of particle size distribution of a dissimilar-metal doped cerium oxide, and improves productivity by increasing a yield, and is excellent in flowability and can improve productivity and reaction efficiency when used as a catalyst.SOLUTION: An intermediate for producing a dissimilar-metal doped cerium oxide has a water content of 7.0 wt.% or less, wherein dissimilar metal is one or two or more metal selected from the group consisting of manganese, cobalt, iron and nickel.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an intermediate for producing cerium oxide doped with a heterogeneous metal, a method for producing the same, and a heterogeneous metal-doped cerium oxide using the same. More specifically, the present invention realizes heterogeneous metal-doped cerium oxide particles having high particle size distribution uniformity and, as a result, high fluidity, and is particularly suitable for use as a catalyst.

Background Art

[0002] Inorganic materials mainly composed of cerium oxide have high heat resistance and remarkable oxygen storage and release ability, and thus are widely used industrially in various applications such as catalysts for reforming reactions and hydrogen production, catalyst carriers, photocatalyst paints, gas sensors, and solid electrolytes for fuel cells. Among them, spherical particles mainly composed of cerium oxide have been proposed for numerous applications due to the convenience of the material. Inorganic materials mainly composed of cerium oxide are required to have a uniform particle size for their applications. Therefore, if particles of the desired particle size can be uniformly prepared, an improvement in productivity can be expected.

[0003] As a method for producing spherical cerium oxide, generally, a method of mixing a cerium salt and another metal salt required for adding functions in an aqueous system and adding oxalate thereto to obtain a precipitate is described in Cited Document 1, a method of adding ammonia or ammonium carbonate as a precipitating agent is described in Cited Document 2, and a method of forming a precipitate using an alkoxide is shown in Cited Document 3. In addition, Cited Document 4 also discloses a method of obtaining a precipitate by adding an alkali.

[0004] However, when using oxalate, in the calcination process, it becomes a large lump of aggregates It shows the drawback of being prone to caking. Also, when using ammonia or ammonium carbonate, it has been reported that due to the residual ammonia component, it is likely to change from spherical to columnar substances in the calcination process. Moreover, alkoxides are of low practicality because they are expensive themselves. The coprecipitation method using alkali also has many practical problems in the manufacturing process as an industrial catalyst, such as low recovery rate, treatment of residues, and low productivity due to batch processes like the precipitation method or coprecipitation method.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the synthesis of spherical cerium oxide mainly by the coprecipitation method, there is still much room for improvement from the viewpoints of industrial cost and productivity, such as maintaining the spherical shape, cost, treatment of solvents and residues after precipitation formation, and from the viewpoint of the uniformity of the particle size distribution of the catalyst. There is a demand for a method for manufacturing oxide particles mainly composed of cerium oxide that can be manufactured at low cost and has a uniform particle size distribution with high efficiency. Among them, in the synthesis of cerium oxide as described later, preventing breakage of the shape during calcination and / or firing and obtaining particles with a uniform particle size distribution are very important for improving the fluidity and productivity of spherical cerium oxide. Since the breakage rate affects the amount of raw materials required for production and has a great impact on the production cost, particular improvement is required. In addition, by continuing production at a low recovery rate, it is said that it is difficult to reuse the by-products that have become oxides after passing through the firing process once. Furthermore, problems such as a large load on subsequent processes such as sieving to selectively remove broken pieces, etc., occur, resulting in a longer process time and an increase in the cost of operating equipment.

[0007] As manufacturing techniques up to now, mainly methods using the coprecipitation method have been proposed in many cases. This is a technique in which a precipitate is generated by adding an acid, ammonia, ammonium carbonate, alkoxide, aqueous alkali solution, etc. to a solution mainly composed of an aqueous cerium salt, recovered by a filter press, etc., and purified by a washing operation. However, considering the use and treatment of a large amount of solvents and additives, it is more efficient and preferable to continuously dry the cerium mixed solution with a continuous spray dryer such as a spray dryer (spray drying) in practical terms.

[0008] In the spray drying of the aqueous solution containing the above cerium salt, the spherical shape cannot be maintained after calcination and the particle size is non-uniform. Therefore, there are drawbacks that the proportion excluded in the classification process is large, the production cost increases, and the productivity decreases. As the cause, it is considered to be due to the handling method of the dry powder before calcination, but the details are unknown.

[0009] As a result of intensive studies on these above-mentioned current situations and problems, the inventors of the present application have found that the hetero-metal doped cerium oxide produced using an intermediate for producing hetero-metal doped cerium oxide having a specific water content has high uniformity in particle size distribution and particle shape and solves the above problems. Furthermore, from the perspective of improving efficiency, the inventors of the present application have found that by subjecting the preparation solution to a drying process such as spray drying or a similar drying process that continuously dries the preparation solution without forming a precipitate like the coprecipitation method, the spherical shape of the particles can be maintained, and it is possible to efficiently prepare an oxide mainly composed of cerium.

Means for Solving the Problems

[0010] That is, the present invention relates to the following 1) to 9). 1) An intermediate for producing a hetero-metal doped cerium oxide having a water content of 7.0 wt% or less. 2) The intermediate for producing a hetero-metal doped cerium oxide according to 1) above, wherein the hetero-metal is one or more metals selected from the group consisting of manganese (Mn), cobalt (Co), iron (Fe), and nickel (Ni). 3) A method for producing a hetero-metal doped cerium oxide using the intermediate for producing a hetero-metal doped cerium oxide according to 1) or 2) above. 4) Regarding the particles of the hetero-metal doped cerium oxide, the method for producing a hetero-metal doped cerium oxide according to 3) above, wherein D90 is 60 μm or more and 120 μm or less. 5) Regarding the particles of the hetero-metal doped cerium oxide, the method for producing a hetero-metal doped cerium oxide according to 3) or 4) above, wherein D10 is 25 μm or more and 40 μm or less. 6) A method for producing an intermediate for producing a hetero-metal doped cerium oxide according to 1) or 2) above, comprising a step of preparing an aqueous solution by formulating raw materials and a step of spray-drying the aqueous solution. 7) The method for producing an intermediate for producing a hetero-metal doped cerium oxide according to 6) above, further comprising a step (C) of adjusting the moisture after the step (B). 8) The method for producing a hetero-metal doped cerium oxide according to 7) above, further comprising a step (D) of firing after the step (C). 9) A hydrogen production method using a heterogeneous metal-doped cerium oxide obtained by the production method according to any one of 3) to 8) above.

Advantages of the Invention

[0011] According to the present invention, the uniformity of the particle size distribution of the heterogeneous metal-doped cerium oxide is excellent. As a result, the ratio excluded by classification in the manufacturing process is reduced, and the productivity is improved in that the yield is increased. In addition, it is possible to provide a heterogeneous metal-doped cerium oxide having excellent fluidity and capable of improving productivity and reaction efficiency particularly when used as a catalyst.

Embodiments for Carrying Out the Invention

[0012] [Water Content of Intermediate for Producing Heterogeneous Metal-Doped Cerium Oxide] In this specification, the intermediate for producing heterogeneous metal-doped cerium oxide means granules obtained by preparing an aqueous solution by formulating raw materials and drying the aqueous solution. The manufacturing method will be described in detail later. The water content of the intermediate for producing heterogeneous metal-doped cerium oxide of the present invention is 7 wt% or less. The present inventors have found that the particle size uniformity and fluidity of the final product, heterogeneous metal-doped cerium oxide, differ depending on the water content. Preferred upper limits of the water content are, in order, 6 wt% , 5 wt%, 4 wt%, 3 wt%, 2.5 wt%, 2 wt%, 1.5 wt%, 1 wt%. Also, preferred lower limits are, in order, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%. Therefore, a particularly preferred range of the water content is 0.4 wt% or more and 1 wt% or less. The water content is calculated from the weight change amount before and after the water adjustment step. Specifically, the weight of the sample is measured with an electronic balance (this result is designated as W1), and after passing through the water adjustment step, it is measured again with an electronic balance (this result is designated as W2), and calculated according to the following formula (1). [Equation 1] Water content (wt%) = (W2 ÷ W1 - 1) × 100 ··· (1) The heterogeneous metal-doped cerium oxide produced by the intermediate for producing heterogeneous metal-doped cerium oxide of the present invention is characterized by high productivity. The productivity is calculated by the following formula (2) from the results of the particle size distribution. Specifically, it is calculated from the ratio of particles with a particle size of 20 μm to 150 μm to the entire particle size distribution. If the particle size is 20 μm or less, it leads to a decrease in bulk density, and if it is 150 μm or more, it leads to a decrease in fluidity. Generally, it is preferable to use particles of 20 - 150 μm as the particles of heterogeneous metal-doped cerium oxide, and particles outside this range need to be excluded by classification or the like. The particle size distribution and D10, D50, and D90 described later are not limited to the details as long as they are general particle size distribution measuring instruments. For example, they can be measured under wet conditions using LMS-2000e USER manufactured by Seishin Enterprise Co., Ltd. [Equation 2] Productivity = (Ratio of volume distribution in the range of particle size from 20 μm to 150 μm) ÷ (Ratio of volume distribution in all particle size ranges) × 100 ···(2)

[0013] [Regarding heterogeneous metal-doped cerium oxide] The present invention relates to a method for producing heterogeneous metal-doped cerium oxide using an intermediate for producing heterogeneous metal-doped cerium oxide. Cerium oxide is a metal oxide represented by CeO2 and is also referred to as ceria. The heterogeneous metal is not particularly limited as long as it is a metal other than Ce (cerium). For example, transition metals such as Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mn, W, Sb, Sn, Mg, Si, Al, Ti, P, etc. can be used. Among these, manganese (Mn), cobalt (Co), iron (Fe), and nickel (Ni) are preferable, and Mn and Co are more preferable. In this specification, heterogeneous metal-doped cerium oxide may sometimes be simply referred to as cerium oxide.

[0014] The method for producing heterogeneous metal-doped cerium oxide of the present invention uses the above-mentioned intermediate for producing heterogeneous metal-doped cerium oxide. In the method for producing a hetero-metal-doped cerium oxide of the present invention, the intermediate for producing the hetero-metal-doped cerium oxide can be molded, supported on an inert carrier such as silica or alumina, or fired as it is. However, firing as it is is particularly preferred.

[0015] [D90 of hetero-metal-doped cerium oxide] Regarding the particles of the hetero-metal-doped cerium oxide obtained by the production method of the present invention, the D90 is preferably 60 μm or more and 120 μm or less. Here, D90 represents the particle size at the point where the cumulative volume fraction is 90%. The lower limit of this D90 is more preferably 70 μm, 80 μm, 90 μm, 95 μm in order of preference. The upper limit of D90 is more preferably 110 μm, 100 μm, 99 μm in order of preference. That is, the most preferable range of D90 is 95 μm or more and 99 μm or less.

[0016] [D10 of hetero-metal-doped cerium oxide] Regarding the particles of the hetero-metal-doped cerium oxide obtained by the production method of the present invention, the D10 is preferably 25 μm or more and 40 μm or less. Here, D10 represents the particle size at the point where the cumulative volume fraction is 10%. The lower limit of this D10 is more preferably 26 μm, 27 μm, 28 μm in order of preference. The upper limit of D10 is more preferably 36 μm, 34 μm, 32 μm in order of preference. That is, the most preferable range of D10 is 28 μm or more and 32 μm or less.

[0017] [D50 of hetero-metal-doped cerium oxide] Regarding the particles of the hetero-metal-doped cerium oxide obtained by the production method of the present invention, the D50 is preferably 40 μm or more and 59 μm or less. Here, D50 represents the particle size at the point where the cumulative volume fraction is 50%. ​

[0018] The heterogeneous metal-doped cerium oxide obtained by the production method of the present invention is excellent in the uniformity of particle size. The uniformity of the particle size can be determined, for example, by evaluating the non-uniformity according to the following mathematical formula (1). Note that since the following formula (3) represents non-uniformity, the larger the numerical value, the more non-uniform, that is, the poorer the uniformity. [Equation 3] Non-uniformity = (D90 - D10) / D50 ···(3)

[0019] The intermediate for producing heterogeneous metal-doped cerium oxide of the present invention, and the heterogeneous metal-doped cerium oxide obtained using the same, preferably satisfy the following formula (i) as the composition. [Chemical Formula 1] Ce 1-x M x O 2-y ···(i) In formula (i), x is 0.03 or more and 0.40 or less, and y is a numerical value depending on the oxidation state of the oxide. The value of x is more preferably 0.05 or more and 0.35 or less, and even more preferably 0.07 or more and 0.30 or less. In formula (i), M is the above-mentioned heterogeneous metal.

[0020] The heterogeneous metal-doped cerium oxide obtained by the production method of the present invention has a uniform particle size and a large sample amount per minimum fluidization velocity in a fluidized bed reactor. Therefore, it is particularly useful for applications in fluidized beds, especially for hydrogen production applications using fluidized beds. For hydrogen production, a catalytic reaction process for decomposing water has been developed, and the steps of reducing cerium oxide at a high temperature to release oxygen and reacting with water at a high temperature are carried out in a fluidized bed. When used in a fluidized bed, uniform particles such as those of the present invention result in a uniform flow of reaction gas and high efficiency due to the uniform fluidization of the particles. Also, the particles are uniformly refined until they become small and reach the end of their lifespan over time, enabling long-term stable operation. Furthermore, since the sample amount per minimum fluidization velocity is large, it becomes possible to use a large number of catalyst particles under the same conditions of gas flow rate and pressure required for fluidization, thus increasing the efficiency of the reaction and enabling miniaturization of the reactor and reduction of the reaction temperature.

[0021] [Regarding manufacturing processes (A) and (B)] The intermediate for producing heterogeneous metal-doped cerium oxide of the present invention and the production method of heterogeneous metal-doped cerium oxide preferably have (A) a step of preparing an aqueous solution by formulating raw materials and (B) a step of drying the aqueous solution. [Regarding step (A)] Step (A) is a step of formulating raw materials to prepare an aqueous formulation or an aqueous solution. Generally, the starting materials for each element constituting the metal-doped cerium oxide are not particularly limited. As the cerium component raw material, cerium oxides such as cerium oxide, ceric acid, cerium acetate, cerium carbonate, cerium hydroxide, and salts such as ammonium cerium nitrate can be used. However, cerium nitrate is preferred, as it provides good operability and a good particle size distribution in terms of solubility and exhaust gas treatment. As an example of the added metal, as the manganese component raw material, nitrates such as manganese nitrate, manganese sulfate, and manganese acetate, carbonates, organic acid salts, hydroxides, and mixtures thereof can be used. Salts, manganese oxide, and manganese metal can also be used. The metal raw material is preferably used as an organic acid salt, and most preferably as an acetate salt. For example, when manganese is used, organic acid salts such as manganese acetate are more preferred. Using these salts provides good operability, increases the recovery rate of the dried product, and ensures a uniform particle size distribution even after calcination. Regarding the blending process, the order of addition of raw materials is not particularly important; it is important that all raw materials are completely dissolved in distilled water. The temperature during blending is preferably 10° C. to 100° C., more preferably 20 to 90° C., and even more preferably 30 to 80° C. In this specification, the symbol "to" includes the numerical values before and after it. Specific examples of step (A) include the following, but are not limited to these. Cerium nitrate hexahydrate is dissolved in distilled water while heating and stirring at a temperature of 10-100°C to obtain an aqueous solution. After confirming complete dissolution of this aqueous solution, manganese acetate tetrahydrate is added and dissolved, and complete dissolution is confirmed. Ammonium nitrate is then dissolved to obtain the raw material aqueous solution. The lower limit of the stirring power for the heating and stirring is preferably 0.01 kW / m 3 , 0.10kW / m 3 , 0.15kW / m 3 , 0.20kW / m 3 and the upper limit is preferably 1.50 kW / m 3 , 1.00kW / m 3 , 0.75kW / m 3 That is, the most preferable range is 0.20 kW / m3 Above 0.75 kW / m 3 It is as follows. In addition, as the solution viscosity of the above aqueous solution, the lower limits are preferably 0.01 cP, 0.1 cP, 0.5 cP, 1 cP in this order, and the upper limits are preferably 1000 cP, 500 cP, 100 cP, 50 cP, 10 cP, 5 cP in this order. That is, the most preferable range is from 1 cP to 5 cP. Furthermore, as the time from the completion of Step A to the next step, the lower limits are preferably 1 minute, 5 minutes, 10 minutes, 30 minutes in this order, and the upper limits are preferably 1 month, 15 days, 7 days, 3 days, 1 day, 10 hours in this order. That is, the most preferable range is from 30 minutes to 10 hours. Furthermore, as the water content in the above aqueous solution, expressed as the content of solid matter, the lower limits are preferably 10% by weight, 20% by weight, 30% by weight in this order, and the upper limits are preferably 80% by weight, 70% by weight, 60% by weight in this order. That is, the most preferable range is from 30% by weight to 60% by weight. Here, the weight of the solid matter refers to the solid content of the reagent to be added, but the attached water and crystal water contained in the reagent are calculated as water by weight.

[0022] <Regarding Step (B)> Step (B) is a step of spray-drying the aqueous solution adjusted in Step (A). Through this step, the above-mentioned formulation or slurry is made into a dry powder. The drying method is not particularly limited as long as it can completely dry the formulation, and examples include drum drying, freeze drying, spray drying, evaporation to dryness, etc. Among these, in the present invention, spray drying, which can dry the slurry into powder or granules in a short time, is particularly preferable. The drying temperature of spray drying varies depending on the concentration of the slurry, the liquid feeding rate, etc., but generally, the temperature at the inlet of the dryer is 150 - 350°C, and the temperature at the outlet is 70 - 250°C. Also, it is preferable to dry so that the average particle size of the obtained dry powder becomes 10 - 500 μm. In this specification, methods similar to spray drying, such as jet turbo dryer, flash jet dryer, spray pyrolyzer, etc. are also included in spray drying. The upper limit of the temperature at the inlet in spray drying is more preferably 330°C, and even more preferably 310°C. The lower limit is more preferably 170°C, and even more preferably 190°C. Therefore, the particularly preferred range is 190°C to 310°C. The upper limit of the temperature at the outlet in spray drying is preferably 200°C, more preferably 180°C, more preferably 160°C, and even more preferably 150°C. The lower limit is more preferably 80°C, and even more preferably 90°C. Therefore, the particularly preferred range is 90°C to 150°C. Also, the residence time of the dry powder in the drying device in spray drying is preferably from 1 second to 3 minutes, more preferably from 5 seconds to 1 minute, even more preferably from 7 seconds to 45 seconds, and most preferably from 10 seconds to 30 seconds. The upper limit regarding the average particle size of the dry powder is more preferably 480 μm, and even more preferably 460 μm. The lower limit is more preferably 20 μm, and even more preferably 40 μm. Therefore, the particularly preferred range is 40 - 460 μm. The average particle size is determined as the volume average (median diameter D50) by measuring the particle size distribution with the above-mentioned laser diffraction scattering particle size distribution measuring device. Also, in order to achieve the above average particle size, in the case of rotary type spray drying, optimization of the rotation speed of the sprayer (atomizer) is suitable. The rotation of the atomizer varies depending on the composition of the catalyst precursor, but is preferably 8,000 rpm or more and 17,000 rpm or less. The upper limit of the more preferable atomizer rotation speed is 16,500 rpm, particularly preferably 16,000 rpm, and most preferably 15,500 rpm. The lower limit of the even more preferable is 8,500 rpm, particularly preferably 9,000 rpm, and most preferably 9,500 rpm. That is, the most preferable range of the atomizer rotation speed is 9,500 rpm or more and 16,000 rpm or less. Also, this rotation speed can also be represented by the relative centrifugal acceleration, and is preferably 2,000 G or more and 30,000 G or less. Also, in the case of nozzle type spray drying, in order to achieve the above average particle size, known techniques can be applied, and the use of any gas type, gas-liquid flow rate ratio, and nozzle shape is included in the present invention. Furthermore, as the time from the completion of Step B until moving to the next step, the lower limits are preferably 1 minute, 5 minutes, 10 minutes, and 30 minutes in that order, and the upper limits are preferably 1 month, 15 days, 7 days, 3 days, 1 day, and 10 hours in that order. That is, the most preferable range is 5 minutes or more and 10 hours or less. When storing the granules after the completion of Step (B), in order to prevent moisture absorption, put them in a plastic bag and then store them in an aluminum zip-lock bag.

[0023] <Regarding Step (D)> Heterogeneous metal-doped cerium oxide can be produced by subjecting the intermediate for producing heterogeneous metal-doped cerium oxide obtained in Steps (A) and (B) to Step (D). Step (D) is a step of calcining the dried powder obtained in Step (B). As the calcination conditions, by calcining at 250°C to 700°C, preferably 250°C to 600°C, under air circulation, salts such as unnecessary nitrate radicals can be removed. In addition, aggregation of the particles of heterogeneous metal-doped cerium oxide after the main firing process can be suppressed. The calcination time is preferably 1 hour to 12 hours, and the heating rate is preferably 0.1 to 10°C / min, more preferably 0.5 to 5°C / min. In this way, a calcined powder is obtained. Regarding the calcination, it is possible to use a tunnel furnace, a muffle furnace, a box-type firing furnace, etc., and furthermore, it is also possible to use a firing device such as a rotary kiln. Regarding the atmosphere during the calcination, air is simple and preferable as the gas to be circulated, but it is also possible to use other inert gases such as nitrogen, carbon dioxide, nitrogen oxide-containing gas for a reducing atmosphere, ammonia-containing gas, hydrogen gas, and mixtures thereof. Also, regarding the absolute humidity of the circulating gas during firing, 0.0001 kg / kgDA to 0.02 kg / kgDA is preferable, more preferably 0.0001 kg / kgDA to 0.015 kg / kgDA, and even more preferably 0.0001 kg / kgDA to 0.01 kg / kgDA.

[0024] <Regarding Step (C)> Step (C) is a moisture adjustment step between the above step (B) and step (D). In the present invention, an intermediate for producing a hetero-metal-doped cerium oxide and a method for producing a hetero-metal-doped cerium oxide passing through step (C) are preferred embodiments. As a specific operation, for example, an intermediate for producing a hetero-metal-doped cerium oxide is placed in a metal or magnetic container to a thickness of 1 to 30 mm and left in the air to adjust the water content. At this time, it is not essential to cover the container with a lid, but it is preferred to do so, and it is more preferred to use a lid without holes. As the environment for moisture adjustment, the absolute humidity is 5 g / m 3 or more and 25 g / m 3 or less is preferred. As the lower limit, more preferably, in order, it is 7 g / m 3 , 8 g / m 3 , 9 g / m 3 , 10 g / m 3 . Also, as the upper limit, more preferably, in order, it is 22 g / m 3 , 20 g / m 3 , 15 g / m 3 , 12 g / m 3 . That is, it is an environment with an absolute humidity of 10 g / m 3 or more and 12 g / m 3 or less, and the time for moisture adjustment is 10 minutes or more, preferably 1 hour or more, more preferably 3 hours or more, and most preferably 5 hours or more. Also, when considering the relative humidity, for example, it is preferred to perform moisture adjustment under humidity conditions of not less than 10% RH and not more than 45% RH in a temperature environment of 15°C to 30°C. The preferred lower limits of the temperature are 17°C, 19°C, and 20°C in order, and the upper limits are 27°C, 25°C, and 22°C in order. As for the humidity, the preferred lower limits are 12% RH, 15% RH, and 17% RH in order, and the upper limits are preferably 40% RH, 35% RH, 30% RH, 25% RH, and 20% RH in order.

[0025] <Regarding other steps> In the method for producing a hetero-metal-doped cerium oxide of the present invention, in addition to the above (A) to (D), a forming step, a step such as main firing, etc. can be performed. As the forming process, either a supported forming method in which a catalyst is supported on a carrier such as silica or an unsupported forming method without using a carrier can be adopted. Specific forming methods include, for example, tableting, pressing, extrusion, granulation, etc. As the shape of the formed product, for example, a columnar shape, a ring shape, a spherical shape, etc. can be appropriately selected in consideration of the operating conditions. However, it is preferably a supported catalyst in which a catalytically active component is supported on a spherical carrier, particularly an inert carrier such as silica or alumina, having an average particle size of 3.0 mm or more and 10.0 mm or less, preferably an average particle size of 3.0 mm or more and 8.0 mm or less. As the supporting method, a rolling granulation method, a method using a centrifugal fluid coating device, a washcoat method, etc. are widely known, and there is no particular limitation as long as the calcined powder can be uniformly supported on the carrier. However, considering the production efficiency of the catalyst, etc., the rolling granulation method is preferred. Specifically, it is a method in which a device having a flat or uneven disk is provided at the bottom of a fixed cylindrical container, and the disk is rotated at a high speed to vigorously stir the carrier charged in the container by repeating the rotation and revolution motions of the carrier itself, and the powder component is supported on the carrier by adding the calcined powder here. In addition, it is preferable to use a binder during the supporting. Specific examples of the binder that can be used include water, ethanol, methanol, propanol, polyhydric alcohols, polyvinyl alcohol as a polymer binder, silica sol aqueous solution as an inorganic binder, etc. However, ethanol, methanol, propanol, and polyhydric alcohols are preferred, diols such as ethylene glycol and triols such as glycerin are more preferred, and an aqueous solution having a glycerin concentration of 5% by mass or more is even more preferred. By using an appropriate amount of glycerin aqueous solution, the moldability becomes good, and a high-performance catalyst with high mechanical strength can be obtained. The amount of these binders used is usually 2 to 60 parts by mass with respect to 100 parts by mass of the pre-calcined powder, but in the case of glycerin aqueous solution, 15 to 50 parts by mass is preferred. During the supporting, the binder and the calcined powder may be alternately supplied to the molding machine or supplied simultaneously. Also, during the forming, a small amount of a known additive, for example, graphite, talc, etc. may be added.In addition, any of the molding aids, pore formers, and carriers added during molding shall not be considered as constituent elements of the active ingredient in the present invention, regardless of whether they have activity in the sense of converting the raw material into some other product. Also, in this final firing step, the purpose is to improve the stability of the particles and increase the purity as an oxide by treating at a temperature higher than that of the preliminary firing. The temperature range in this final firing can be from 600°C to 2000°C, preferably from 700°C to 1500°C, with the air flowing. The firing time is preferably from 1 hour to 40 hours, and the heating rate is preferably from 0.1 to 10°C / min, more preferably from 0.5 to 5°C / min. Regarding the atmosphere during this final firing, air is simple and preferable as the gas to be circulated, but it is also possible to use other inert gases such as nitrogen, carbon dioxide, nitrogen oxide-containing gases for a reducing atmosphere, ammonia-containing gases, hydrogen gas, and mixtures thereof. Also, regarding the absolute humidity of the gas flowing during firing, it is preferably from 0.0001 kg / kgDA to 0.02 kg / kgDA, more preferably from 0.0001 kg / kgDA to 0.015 kg / kgDA, and even more preferably from 0.0001 kg / kgDA to 0.01 kg / kgDA.

[0026] The hetero-metal-doped cerium oxide of the present invention is characterized in that the raw materials used in the above step (A) satisfy the following mathematical formula (4). By this, the particle size distribution of the particles after drying can be controlled. Furthermore, the recovery efficiency can be improved by reducing adhesion and the like in the drying step. Moreover, it is expected that there will be no change in quality even when firing is carried out under loading conditions of several centimeters in the firing step. If this value is too small, adhesion in the dryer may occur, and a sufficient recovery rate of the dried product may not be obtained. Conversely, if it is too large, the shape of the dried particles cannot maintain a spherical shape. [Equation 4] 0.7 ≦ (a + b) / c ≦ 8.0 ··· (4) Here, a to c have the following meanings. a: Amount of substance (mol) of cerium (Ce) in the raw material The amount of substance of cerium in the raw material means the content of cerium in the compound containing cerium used as the raw material. For example, when 1667.7 g of cerium nitrate hexahydrate is used as the raw material, a is 3.838 mol. b: Amount of substance (mol) of metals other than cerium in the raw material The amount of substance of metals other than cerium in the raw material means the content of the metals other than cerium in the compound containing metals other than cerium used as the raw material. For example, when 141.1 g of manganese acetate tetrahydrate is used as the raw material, it means the content of manganese, and b is 0.576 mol. c: Amount of substance (mol) of the moisture-proof agent It is the amount of substance of the moisture-proof agent used as the raw material. Ammonium nitrate is generally used as the moisture-proof agent, but other salts can also be used. For example, ammonium carbonate, ammonium chloride, ammonium acetate, ammonium hydroxide (aqueous ammonia), etc. may be mentioned. Preferably, it is ammonium nitrate, which has good effects and convenience.

[0027] The range of (a + b) / c in the above formula (4) is 0.7 to 8.0, but the upper limit may be 20, 10 is more preferable, 8.0 is more preferable, and 5.0 is particularly preferable. Also, as the lower limit, it is 0.7, but 1.2 is more preferable, 1.3 is more preferable, 1.4 is particularly preferable, and 1.5 is most preferable. Therefore, the range of (a + b) / c is most preferably 1.5 to 5.0.

[0028] In the method for producing a heterometal-doped cerium oxide of the present invention, it is preferable that the raw materials used in the above step (A) satisfy the above formula (4). As the upper limit of b / c in the above formula (4), 0.80 is more preferable, 0.60 is further preferable, 0.50 is particularly preferable, and 0.40 is most preferable. As the lower limit, 0.10 is more preferable, 0.15 is further preferable, 0.20 is particularly preferable, and 0.25 is most preferable. Therefore, the range of b / c is most preferably 0.25 to 0.40.

[0029] Incidentally, the preferable ranges for each of a to c above are as follows. However, the following values of a, b, and c in this section are the case where the distilled water charged during the raw material input in the blending step (A) is 1500 parts by mass, and it is necessary to adjust according to the ratio with distilled water as appropriate according to the scale. a is preferably 1.0 mol or more and 10 mol or less. As the lower limit, 2.0 mol and 3.0 mol are more preferable in this order, and as the upper limit, 5.0 mol and 4.0 mol are more preferable in this order. That is, it is most preferable that it is 3.0 mol or more and 4.0 mol or less. b is preferably 0.01 mol or more and 1.0 mol or less. As the lower limit, 0.1 mol, 0.3 mol, and 0.5 mol are more preferable in this order, and as the upper limit, 0.9 mol, 0.8 mol, and 0.7 mol are more preferable in this order. That is, it is most preferable that it is 0.5 mol or more and 0.7 mol or less. c is preferably 0.5 mol or more and 10.0 mol or less. As the lower limit, 0.6 mol and 0.7 mol are more preferable in this order, and as the upper limit, 5.0 mol and 4.0 mol are more preferable in this order. That is, it is most preferable that it is 0.7 mol or more and 4.0 mol or less.

[0030] The heterogeneous metal-doped cerium oxide obtained by the production method of the present invention preferably has a bulk specific gravity of 0.51 g / cc or more and 1.50 g / cc. The bulk specific gravity is important, for example, when it is used in a fluidized state. If it is too small, the amount that can be charged per unit volume will be reduced, and when used as a catalyst, the reaction efficiency may decrease, resulting in increased running costs. On the other hand, if it is too large, the velocity and pressure of the fluid required for fluidization will increase, which will also cause an increase in running costs. More preferably in descending order as the lower limit of the bulk specific gravity are 0.53 g / cc, 0.55 g / cc, 0.58 g / cc, 0.60 g / cc. Further preferably in descending order as the upper limit are 1.40 g / cc, 1.30 g / cc, 1.20 g / cc, 1.10 g / cc. That is, most preferably, the bulk specific gravity is 0.60 g / cc or more and 1.10 g / cc or less.

[0031] The heterogeneous metal-doped cerium oxide obtained by the production method of the present invention is characterized by high uniformity of particle size distribution. Furthermore, the heterogeneous metal-doped cerium oxide produced by the production method of the present invention is characterized by a low content of fine particles having a particle diameter of 10 μm or less. Therefore, for example, it has excellent properties in the following applications. In general industrial powders, such as when used as a catalyst, battery material, sensor material, pigment, dispersoid, cosmetic, abrasive itself or as a raw material thereof, the fluidity is improved, and it is excellent in handleability and operability as a powder. Specifically, the residual amount of powder in a freight container, feeder or hopper is reduced, and the manufacturing loss is reduced. Such operability as a powder can be easily evaluated by known methods. For example, in addition to true density, bulk density and compressibility, known methods can be applied to the angle of repose, angle of collapse, and angle of difference. Particularly when used as a catalyst, it can be used as an exhaust gas treatment catalyst, a catalyst for hydrogen production, etc. by forming. The performance is improved due to the uniform particle size distribution, and furthermore, the discharge from the reactor to the outside of the system is suppressed due to the small amount of fine particles, and a stable reaction result can be expected. When used as a battery material or a sensor material, densification can be expected due to the uniform particle size distribution, the conductivity is improved, and the performance can be improved. When used as an abrasive, for example, when used as a CMP abrasive for semiconductors, due to the uniform particle size distribution, polishing can be performed to improve the flatness of the surface unevenness in the plane after polishing.

Examples

[0032] Hereinafter, examples are shown with specific examples, but the present invention is not limited to the examples as long as it does not deviate from the gist thereof.

[0033] [Example 1] While heating and stirring 1500 parts by mass of distilled water at 80 ° C, 1667.7 parts by mass of cerium nitrate hexahydrate was dissolved to obtain an aqueous solution (A1). After confirming the complete dissolution of (A1), 141.1 parts by mass of manganese acetate tetrahydrate was added and dissolved to prepare an aqueous solution (B1). After confirming the complete dissolution of B1, 150.2 parts by mass of ammonium nitrate was dissolved to prepare an aqueous solution (C1). The above aqueous solutions were sequentially mixed while vigorously stirring to confirm a completely dissolved state, and a dry powder (D1) was obtained using a spray dryer. The inlet temperature of the spray was 240 ° C and the outlet temperature was 140 ° C, and the rotation speed of the atomizer was 10500 rpm. The composition ratio of the catalyst active component excluding oxygen at this time was Ce = 100 and Mn = 16 in atomic ratio. The elemental ratio was measured using an XRF apparatus (the same applies hereinafter). Thereafter, the dry powder was placed in a magnetic crucible having a diameter of 45 mm and a depth of 36 mm so that the thickness became 30 mm, and the one with a lid without holes was placed at room temperature of 21 ° C, relative humidity of 18%, and absolute humidity of 11.5 g / m 3 After leaving it for 5 hours in the environment of, an intermediate (E1) was obtained, and then calcination was carried out in the step of raising the temperature from 50 ° C to 300 ° C at 0.5 ° C / min under air circulation to obtain a hetero-metal doped cerium oxide catalyst (Catalyst 1). The elemental composition ratio of the obtained hetero-metal doped cerium oxide catalyst excluding oxygen was Ce = 100 and Mn = 16 in atomic ratio.

[0034] [Example 2] The dry powder was placed in a magnetic crucible with a diameter of 45 mm and a depth of 36 mm so that the thickness was 30 mm, covered with a lid without holes, and left in an environment of 21°C at room temperature, 18% relative humidity, and 11.5 g / m absolute humidity for 24 hours. After that, the intermediate (E2) was obtained in exactly the same manner as in Example 1, and then it was fired in exactly the same manner as in Example 1 to obtain a heterogeneous metal-doped cerium oxide catalyst (Catalyst 2). 3 After that, the intermediate (E2) was obtained in exactly the same manner as in Example 1, except that it was left in the environment of 21°C at room temperature, 18% relative humidity, and 11.5 g / m absolute humidity for 24 hours without a lid. Then, it was fired in exactly the same manner as in Example 1 to obtain a heterogeneous metal-doped cerium oxide catalyst (Catalyst 2).

[0035] [Example 3] The dry powder was placed in a magnetic crucible with a diameter of 45 mm and a depth of 36 mm so that the thickness was 30 mm, and left in an environment of 21°C at room temperature, 18% relative humidity, and 11.5 g / m absolute humidity for 5 hours without a lid. After that, the intermediate (E3) was obtained in exactly the same manner as in Example 1, and then it was fired in exactly the same manner as in Example 1 to obtain a heterogeneous metal-doped cerium oxide catalyst (Catalyst 3). 3 After that, the intermediate (E3) was obtained in exactly the same manner as in Example 1, except that it was left in the environment of 21°C at room temperature, 18% relative humidity, and 11.5 g / m absolute humidity for 5 hours without a lid. Then, it was fired in exactly the same manner as in Example 1 to obtain a heterogeneous metal-doped cerium oxide catalyst (Catalyst 3).

[0036] [Comparative Example 1] The dry powder was placed in a magnetic crucible with a diameter of 45 mm and a depth of 36 mm so that the thickness was 30 mm, and left in an environment of 21°C at room temperature, 18% relative humidity, and 11.5 g / m absolute humidity for 24 hours without a lid. After that, the intermediate (E4) was obtained in exactly the same manner as in Example 1, and then it was fired in exactly the same manner as in Example 1 to obtain a heterogeneous metal-doped cerium oxide catalyst (Catalyst 4). 3 After that, the intermediate (E4) was obtained in exactly the same manner as in Example 1, except that it was left in the environment of 21°C at room temperature, 18% relative humidity, and 11.5 g / m absolute humidity for 24 hours without a lid. Then, it was fired in exactly the same manner as in Example 1 to obtain a heterogeneous metal-doped cerium oxide catalyst (Catalyst 4).

[0037] [Evaluation] For the heterogeneous metal-doped cerium oxides and intermediates obtained in Examples 1 to 3 and Comparative Example 1, the median diameter (D10, D50, D90), the uniformity of the particle size distribution, productivity, and water content were measured and evaluated according to the following criteria. [Median Diameter] Measured under wet conditions using LMS-2000e USER manufactured by Seishin Enterprise Co., Ltd., and D50 (the particle diameter at the point where the cumulative volume fraction is 50%) in the obtained volume distribution was defined as the median diameter. In addition, D10 (the particle diameter at the point where the cumulative volume fraction is 10%), D50, and D90 (the particle diameter at the point where the cumulative volume fraction is 90%) obtained in the same manner are shown in Table 1. <Non-uniformity of particle size distribution> Using the above median diameter (D50), the uniformity of the particle size distribution was evaluated by the above formula (3). This value is a comparison made using an arbitrary particle diameter as a measure of the width of the volume distribution. The unit of the particle diameter used is μm. <Productivity> From the results of the particle size distribution, the ratio of particles with a particle size of 20 μm to 150 μm calculated by the above formula (2) to the entire particle size distribution. <Water content> The weight of the sample was measured with an electronic balance (this result is denoted as W1), and after passing through the moisture adjustment process, it was measured again with an electronic balance (this result is denoted as W2), and calculated according to the above formula (1).

[0038]

Table 1

Industrial applicability

[0039] By the intermediate of the present invention, heterogeneous metal-doped cerium oxide with high uniformity of particle size distribution can be obtained, and furthermore, the productivity in manufacturing heterogeneous metal-doped cerium oxide is high, and it can be manufactured with high efficiency using less raw materials.

Claims

1. (A) A step of preparing a raw material to adjust an aqueous solution, (B) A step of spray-drying the aqueous solution having A method for producing particles for producing hetero-metal-doped cerium oxide, wherein the water content is 7.0 wt% or less, and the hetero-metal doped into cerium oxide is one or more metals selected from transition metals Note that Hetero-metal-doped cerium oxide refers to a composite metal oxide that satisfies the following formula (i) as a composition Ce １－ｘ M ｘ O ２－ｙ ...(i) (In formula (i), x is 0.03 or more and 0.40 or less, and y is a numerical value depending on the oxidation state of the oxide. In formula (i), M is the above-mentioned hetero-metal.) The water content means that the weight of the sample is measured with an electronic balance (this result is designated as W1), and after passing through the moisture adjustment step, it is measured again with an electronic balance (this result is designated as W2), and the value calculated according to the following formula (1) is shown Water content (wt%) = (W2 ÷ W1 - 1) × 100... (1)

2. The method for producing particles for producing hetero-metal-doped cerium oxide according to claim 1, having (C) a moisture adjustment step after the above step (B).

3. The method for producing particles for producing hetero-metal-doped cerium oxide according to claim 1 or 2, wherein the hetero-metal is one or more metals selected from the group consisting of manganese (Mn), cobalt (Co), iron (Fe), and nickel (Ni).

4. A method for producing hetero-metal-doped cerium oxide using the particles for producing hetero-metal-doped cerium oxide produced by the method according to any one of claims 1 to 3

5. Regarding the particles of hetero-metal-doped cerium oxide, the method for producing hetero-metal-doped cerium oxide according to claim 4, wherein D90 is 60 μm or more and 120 μm or less

6. Regarding the particles of hetero-metal-doped cerium oxide, the method for producing hetero-metal-doped cerium oxide according to claim 4 or 5, wherein D10 is 25 μm or more and 40 μm or less

7. The method for producing hetero-metal-doped cerium oxide according to claim 6, having (D) a firing step after the above step (C).

8. A method for producing hydrogen using hetero-metal-doped cerium oxide obtained by the production method according to any one of claims 4 to 7

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