Intermediate for manufacturing hetero-metal doped cerium oxide, manufacturing method of the same, and hetero-metal doped cerium oxide using the same

Abstract

To provide an intermediate for manufacturing cerium oxide doped with hetero-metals, a method for producing the same, and hetero-metal doped cerium oxide using the same, which exhibits excellent uniformity in particle size distribution of hetero-metal doped cerium oxide, resulting in a reduced proportion excluded by classification during the manufacturing process and thus improved productivity due to higher yield, and which also has excellent fluidity, thereby enabling enhanced productivity and reaction efficiency, particularly when used as a catalyst.SOLUTION: An intermediate of hetero-metal doped cerium oxide has a water content of 7.0 wt% or less.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 uniformity in particle size distribution 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 capabilities, and are therefore 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 their convenience as materials. Inorganic materials mainly composed of cerium oxide are required to have uniform particle sizes 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 disclosed in Cited Document 1, a method of adding ammonia or ammonium carbonate as a precipitant is disclosed 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 step, it becomes a large lump of aggregates It exhibits 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 a spherical to a columnar substance in the calcination process. Moreover, alkoxides are of low practicality because they are expensive themselves. The coprecipitation method using an 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 the solvent 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 high-efficiency and uniform particle size distribution. Among these, 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. Also, by continuing production with a low recovery rate, it is said that it is difficult to reuse by-products that have become oxides after passing through the firing process. 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. This is a technique in which a precipitate is formed 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. The cause 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 a high uniformity in particle size distribution and particle shape and solves the above problems. In addition, from the perspective of improving efficiency, the inventors of the present application have found that by passing through a drying process such as spray drying that continuously dries the preparation liquid without forming a precipitate like the coprecipitation method, or a drying process similar thereto, 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 the 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 the 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) a step of preparing an aqueous solution by formulating raw materials; and (B) 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, after the step (B), (C) a moisture adjustment step. 8) The method for producing a hetero-metal doped cerium oxide according to 7) above, further comprising, after the step (C), (D) a firing step. 9) A hydrogen production method using hetero-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 hetero-metal-doped cerium oxide has excellent uniformity in particle size distribution. As a result, the proportion 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 hetero-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 the intermediate for producing hetero-metal-doped cerium oxide] In the present specification, the intermediate for producing hetero-metal-doped cerium oxide means granules obtained by preparing an aqueous solution by formulating raw materials and drying the aqueous solution. Details of the production method will be described later. The water content of the intermediate for producing hetero-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, hetero-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. Note that the water content is calculated from the amount of weight change 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 using 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 with a size 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 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 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 preferred, and Mn and Co are more preferred. 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 the 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, but 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 diameter 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. The upper limit of D90 is more preferably 110 μm, 100 μm, 99 μm in order. 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 diameter 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. The upper limit of D10 is more preferably 36 μm, 34 μm, 32 μm in order. 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 diameter at the point where the cumulative volume fraction is 50%. The lower limit of this D50 is more preferably 45 μm, 48 μm, 50 μm, 51 μm in order. The upper limit of D50 is more preferably 58 μm, 57 μm, 56 μm, 55 μm in order. That is, the most preferable range of D50 is 51 μm or more and 55 μm or less.

[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 the heterogeneous metal-doped cerium oxide of the present invention and the heterogeneous metal-doped cerium oxide obtained by 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. Note that 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. Also 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 since the sample amount per minimum fluidization velocity is large in a fluidized bed reactor, 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 high temperature to release oxygen and reacting with water at 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, since the particles are uniformly refined until they become small and reach the end of their lifespan over time, long-term stable operation is possible. Furthermore, since the sample amount relative to the minimum fluidization velocity is large, it becomes possible to use a large number of catalyst particles under the same conditions of gas flow velocity and pressure required for fluidization, thereby increasing the efficiency of the reaction and enabling miniaturization of the reactor and reduction of the reaction temperature.

[0021] [Regarding production 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-added cerium oxide are not particularly limited. As the cerium component raw material, cerium oxides such as cerium oxide, cerium acid, cerium acetate, cerium carbonate, cerium hydroxide, salts such as ammonium cerium nitrate, etc. can be used. Preferably, when cerium nitrate is used, good operability can be obtained from the viewpoints of solubility and exhaust gas treatment, and a good particle size distribution can be obtained. In the example of the added metal, as the manganese component raw material, nitrates such as manganese nitrate, manganese sulfate, manganese acetate, carbonates, organic acid salts, hydroxides, etc. or mixtures thereof can be used. Salts, manganese oxide, metallic manganese, etc. can be used. In addition, as the metal raw material, it is preferably used as an organic acid salt, and most preferably used as an acetate. For example, when manganese is used, it is more preferably an organic acid salt such as manganese acetate. When this is used, the operability is good, the recovery rate of the dried product is increased, and a uniform particle size distribution can be obtained even after firing. Regarding the formulation, the order of adding raw materials is not particularly relevant. It is important that all raw materials are completely dissolved in distilled water. Regarding the temperature during the formulation, 10°C to 100°C is preferable, 20 to 90°C is more preferable, and more preferably 30 to 80°C. In this specification, "~" includes the numerical values before and after. Specific examples of step (A) include the following. However, it is not limited to this description. While maintaining distilled water at 10 to 100°C and heating and stirring, cerium nitrate hexahydrate is dissolved to obtain an aqueous solution. After confirming the complete dissolution of this aqueous solution, manganese acetate tetrahydrate is added and dissolved, and complete dissolution is confirmed. Then, ammonium nitrate is dissolved to obtain an aqueous solution of the raw materials. As the stirring power for the above heating and stirring, in order of preference for the lower limit, it is 0.01 kW / m 3 , 0.10 kW / m 3 , 0.15 kW / m 3 , 0.20 kW / m 3 , and in order of preference for the upper limit, it is 1.50 kW / m 3 , 1.00 kW / m 3 , 0.75 kW / 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 order of preference, and the upper limits are preferably 1000 cP, 500 cP, 100 cP, 50 cP, 10 cP, 5 cP in order of preference. 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 order of preference, and the upper limits are preferably 1 month, 15 days, 7 days, 3 days, 1 day, 10 hours in order of preference. 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 order of preference, and the upper limits are preferably 80% by weight, 70% by weight, 60% by weight in order of preference. 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 component of the reagent to be added, and 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 equivalent to spray drying, such as jet turbo dryers, flash jet dryers, and spray pyrolizers, 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, still 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 apparatus in spray drying is preferably from 1 second to 3 minutes, more preferably from 5 seconds to 1 minute, still 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 to 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 apparatus. 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 more preferable one is 8,500 rpm, the particularly preferable lower limit is 9,000 rpm, and the most preferable lower limit is 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 on 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 preferred 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)> By subjecting the intermediate for producing hetero-metal doped cerium oxide obtained in steps (A) and (B) to step (D), hetero-metal doped cerium oxide can be produced. Step (D) is a step of calcining the dried powder obtained in step (B). As the conditions for calcination, 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 hetero-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 - 10°C / min, more preferably 0.5 - 5°C / min. In this way, a calcined powder is obtained. Regarding 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 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 gases for a reducing atmosphere, ammonia-containing gases, hydrogen gas, and mixtures thereof. Also, regarding the absolute humidity of the gas circulated 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, a preferred embodiment is a method for producing an intermediate for producing a hetero-metal-doped cerium oxide and a hetero-metal-doped cerium oxide through step (C). 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, 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. As the time for moisture adjustment, it 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 relative humidity, for example, it is preferred to perform moisture adjustment under humidity conditions of 10% RH or more and 45% RH or less in a temperature environment of 15°C to 30°C. The preferred lower limits for 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 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, cylindrical, ring-shaped, spherical, etc. can be appropriately selected in consideration of the operating conditions. However, it is preferably a supported catalyst having an average particle size of 3.0 mm or more and 10.0 mm or less, preferably 3.0 mm or more and 8.0 mm or less, in which a catalyst active component is supported on a spherical carrier, particularly an inert carrier such as silica or alumina. Widely known supported methods include a rolling granulation method, a method using a centrifugal fluid coating device, a washcoat method, etc. There is no particular limitation as long as it is a method capable of uniformly supporting the calcined powder 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 placed at the bottom of a fixed cylindrical container, and the disk is rotated at high speed to vigorously stir the carrier charged in the container by repeating the rotation and revolution movements of the carrier itself, and the calcined powder is added here to support the powder component on the carrier. In addition, it is preferable to use a binder during the supporting process. 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. 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 with a glycerin concentration of 5% by mass or more is even more preferred. By using an appropriate amount of the glycerin aqueous solution, the moldability becomes good, and a high-performance catalyst with high mechanical strength can be obtained. The usage amount of these binders 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 the glycerin aqueous solution, 15 to 50 parts by mass is preferred. During the supporting process, the binder and the calcined powder may be alternately supplied to the molding machine or supplied simultaneously. Also, during the forming process, a small amount of known additives such as graphite and talc may be added.In addition, the molding aids, pore formers, and carriers added during molding are not 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 materials 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. However, it is also possible to use other inert gases such as nitrogen, carbon dioxide, nitrogen oxide-containing gases, ammonia-containing gases, hydrogen gas, and mixtures thereof for a reducing atmosphere. 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 heterogeneous 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, it is expected to improve the recovery efficiency by reducing adhesion and the like in the drying process, and moreover, 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 may occur in the dryer 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: The 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. As the moisture-proof agent, ammonium nitrate is common, but other salts can also be used. For example, ammonium carbonate, ammonium chloride, ammonium acetate, ammonium hydroxide (aqueous ammonia), etc. can 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 the hetero-metal doped cerium oxide of the present invention, it is preferable that the raw material used in the above step (A) satisfies the above mathematical formula (4). As the upper limit of b / c in the above mathematical formula (4), 0.80 is more preferable, 0.60 is more preferable, 0.50 is particularly preferable, and 0.40 is most preferable. Also, as the lower limit, 0.10 is more preferable, 0.15 is more 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] For each of a to c above, the preferred ranges are as follows. However, the following values of a, b, and c in this section are applicable when 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. Preferably, a is 1.0 mol or more and 10 mol or less. As its lower limit, 2.0 mol and 3.0 mol are more preferable in order, and as its upper limit, 5.0 mol and 4.0 mol are more preferable in order. That is, it is most preferable when it is 3.0 mol or more and 4.0 mol or less. Preferably, b is 0.01 mol or more and 1.0 mol or less. As its lower limit, 0.1 mol, 0.3 mol, and 0.5 mol are more preferable in order, and as its upper limit, 0.9 mol, 0.8 mol, and 0.7 mol are more preferable in order. That is, it is most preferable when it is 0.5 mol or more and 0.7 mol or less. Preferably, c is 0.5 mol or more and 10.0 mol or less. As its lower limit, 0.6 mol and 0.7 mol are more preferable in order, and as its upper limit, 5.0 mol and 4.0 mol are more preferable in order. That is, it is most preferable when it is 0.7 mol or more and 4.0 mol or less.

[0030] The hetero-metal doped cerium oxide obtained by the production method of the present invention preferably has a bulk density of 0.51 g / cc or more and 1.50 g / cc. The bulk density 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 small, and when used as a catalyst, the reaction efficiency may decrease, resulting in an increase in running costs. On the other hand, if it is too large, the fluid velocity and pressure required for fluidization will increase, which will also cause an increase in running costs. As the lower limit of the bulk density, 0.53 g / cc, 0.55 g / cc, 0.58 g / cc, and 0.60 g / cc are more preferable in order. As the upper limit, 1.40 g / cc, 1.30 g / cc, 1.20 g / cc, and 1.10 g / cc are more preferable in order. That is, most preferably, the bulk density 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 in that the content of fine particles having a particle diameter of 10 μm or less is small. Therefore, for example, it is excellent in characteristics in the following applications. In general industrial powders, for example, when used as a catalyst, battery material, sensor material, pigment, dispersoid, cosmetic, abrasive itself or 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 frecon, feeder or hopper is reduced, and the manufacturing loss is reduced. Such operability as a powder can be easily evaluated by a known method. For example, in addition to true density, bulk density and compressibility, known methods can be applied for the angle of repose, angle of collapse and difference angle. Particularly when used as a catalyst, it can be used for an exhaust gas treatment catalyst, a hydrogen production catalyst, etc. by molding. The performance is improved due to the uniform particle size distribution, and 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, high densification can be expected due to the uniform particle size distribution, the conductivity is improved, and an improvement in performance can be expected. When used as an abrasive, for example, when used as a CMP abrasive for semiconductors, polishing with improved in-plane unevenness uniformity after polishing can be achieved due to the uniform particle size distribution.

Examples

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

[0033] [Example 1] 1500 parts by mass of distilled water was heated and stirred at 80 °C, and 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 stirring vigorously, and the complete dissolution state was confirmed, and a dry powder (D1) was obtained using a spray dryer. The inlet temperature of the spray was 240 °C, 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 with a diameter of 45 mm and a depth of 36 mm so that the thickness was 30 mm, and covered with a lid without holes. It was left for 5 hours in an environment of room temperature 21 °C, relative humidity 18%, and absolute humidity 11.5 g / m 3 to obtain an intermediate (E1), and then calcination was carried out in a step of raising the temperature from 50 °C to 300 °C at 0.5 °C / min under air flow 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, and covered with a lid without holes. An intermediate (E2) was obtained in exactly the same manner as in Example 1 except that it was left for 24 hours in an environment of room temperature 21 °C, relative humidity 18%, and absolute humidity 11.5 g / m 3 and then this was calcined in exactly the same manner as in Example 1 to obtain a hetero-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 without a lid, at room temperature 21 °C, relative humidity 18%, and absolute humidity 11.5 g / m 3An intermediate (E3) was obtained in the same manner as in Example 1 except that it was left standing for 5 hours in the environment, and then this was fired in 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 without a lid, at room temperature of 21 °C, relative humidity of 18%, and absolute humidity of 11.5 g / m 3 An intermediate (E4) was obtained in the same manner as in Example 1 except that it was left standing for 24 hours in the environment, and then this was fired in the same manner as in Example 1 to obtain a heterogeneous metal-doped cerium oxide catalyst (Catalyst 4).

[0037] [Evaluation] Regarding the heterogeneous metal-doped cerium oxides and intermediates obtained in Examples 1 to 3 and Comparative Example 1, the median diameters (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> Using LMS-2000e USER manufactured by Seishin Enterprise Co., Ltd., it was measured under wet conditions, and D50 (the particle size at the point where the cumulative volume fraction is 50%) in the obtained volume distribution was taken as the median diameter. In addition, D10 (the particle size at the point where the cumulative volume fraction is 10%), D50, and D90 (the particle size 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 the width of the volume distribution with an arbitrary particle size. The unit of the particle size 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 it was calculated according to the above formula (1).

[0038]

Table 1

Industrial Applicability

[0039] By using the intermediate of the present invention, heterogeneous metal-doped cerium oxide with high uniformity in particle size distribution can be obtained. 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. 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 Claim 1, 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 Claim 1 or 2.

4. The method for producing a hetero-metal doped cerium oxide according to Claim 3, wherein, with respect to the particles of the hetero-metal doped cerium oxide, D90 is 60 μm or more and 120 μm or less.

5. The method for producing a hetero-metal doped cerium oxide according to Claim 3 or 4, wherein, with respect to the particles of the hetero-metal doped cerium oxide, 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 Claim 1 or 2, comprising: (A) a step of preparing an aqueous solution by formulating raw materials; and (B) 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 Claim 6, further comprising, after the step (B), (C) a moisture adjustment step.

8. The method for producing a hetero-metal doped cerium oxide according to Claim 7, further comprising, after the step (C), (D) a firing step.

9. A method for producing hydrogen using a hetero-metal doped cerium oxide obtained by the production method according to any one of Claims 3 to 8.

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