Powder containing porous tertiary particle, and producing method thereof

Abstract

To provide porous particles capable of more effectively exhibiting performance of an active component.SOLUTION: A powder of porous tertiary particles, which are composed of aggregates of porous secondary particles is provided, where the average particle diameter of the powder is in the range of 0.1 to 5.0 mm, and in the pore size distribution of the powder, a first peak exists in the range of pore diameters of 5 nm or more and less than 100 nm (PdR1), and a second peak exists in the range of pore diameters of 100 nm or more and 10,000 nm or less (PdR2). When the pore diameter of the first peak is Pd1, the total pore volume (PV1) of pores with diameters of 0.75×Pd1 or more and 1.25×Pd1 or less accounts for 60% or more of the total pore volume of pores with diameters less than 100 nm (PVR1). When the total volume of pores with diameters less than 100 nm is defined as the first total volume (PVR1) and the total volume of pores with diameters of 100 nm or more is defined as the second total volume (PVR2), the value of PVR1 / (PVR1+PVR2) is in the range of 0.2 to 0.6.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to porous particles useful as carriers for carrying active components such as enzymes and catalysts, and in particular to porous tertiary particles formed by the aggregation of porous secondary particles. [Background technology]

[0002] Conventionally, porous secondary particles having a void structure (pores) between primary particles have been used as carriers (see, for example, Patent Document 1). These secondary particles are formed by closely bonding spherical primary particles with a narrow particle size distribution (monodisperse), resulting in highly uniform pore sizes. This suppresses aggregation of active components (such as metal fine particles), allowing the active components to function effectively. Furthermore, the pore size can be controlled by adjusting the primary particle size. Therefore, an optimal pore size can be set depending on the size of the active component. In Patent Document 1, primary particles with an average particle size of 10 to 50 nm are aggregated to form porous secondary particles with an average particle size of 0.5 to 50 μm.

[0003] It is also known that primary particles are aggregated to form aggregated particles with an average particle size of 5 μm or less, and then pores are formed in the primary particles to make them porous (see, for example, Patent Document 2). At this time, void layers are also formed between the primary particles.

[0004] It is also known that a spherical molded body (carrier) having a large pore volume and an average particle diameter of 0.3 to 5 mm can be formed (see, for example, Patent Document 3). Patent Document 3 describes that the spherical molded body is made of an inorganic oxide, and that a carrier having excellent compressive strength and abrasion resistance can be realized despite the large pore volume. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-138021 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-073681 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-058932 Summary of the Invention [Problem to be solved by the invention]

[0006] When a carrier with a small particle size (approximately 30 μm) as disclosed in Patent Document 1 is used in a continuous system (column packing), there is a problem of high pressure loss and reduced processing capacity. Furthermore, simply increasing the particle size of the carrier makes it difficult for the active ingredient to be supported inside the carrier, and also makes it difficult for the reaction solution to sufficiently penetrate and diffuse inside the carrier, resulting in poor reaction efficiency. Therefore, an object of the present invention is to provide porous particles that can more effectively demonstrate the performance of the active ingredient. [Means for solving the problem]

[0007] The present inventors have found that porous tertiary particles that meet certain requirements are extremely useful as carriers. That is, the powder of the present invention contains porous tertiary particles that are formed by the aggregation of porous secondary particles, and has the following characteristics:

[0008] (1) The average particle size of the powder is in the range of 0.1 to 5.0 mm. (2) In the powder pore size distribution (X axis: pore size, Y axis: pore volume differentiated by pore size), the pore size ranges from 5 nm to less than 100 nm (Pd R1 ) the first peak is in the pore diameter range of 100 nm to 10,000 nm (Pd R2 ) there is a second peak. (3) When the pore diameter of the first peak is Pd1, the sum of the volumes of pores (PV1) of Pd1 × 0.75 or more and Pd1 × 1.25 or less is the total volume of pores with a pore diameter of less than 100 nm (PV R1 ) is more than 60%. (4) The total volume of pores with a pore diameter of less than 100 nm is defined as the first total volume (PV R1 ), and the total volume of pores with a pore diameter of 100 nm or more is the second total volume (PVR2 ), then PV R1 / (PV R1 +PV R2 ) is in the range of 0.2 to 0.6.

[0009] In such powders, the pores formed in the secondary particles constituting the tertiary particles have a relatively uniform diameter. Furthermore, there is a good balance between the pore diameter and pore volume within the secondary particles that support the active ingredient and the pore volume of the gaps (pores) between the secondary particles through which the reaction liquid passes, allowing the performance of the active ingredient to be more effectively exhibited.

[0010] The method for producing porous tertiary particles according to the present invention includes: a first step of preparing a dispersion of primary particles, which are silica particles having an average particle size of 10 to 300 nm, a particle size coefficient of variation of 10% or less, and a sphericity of 0.85 or more; a second step of spraying a spray liquid containing the dispersion of primary particles into an air stream to granulate aggregates of the primary particles, and heat-treating the aggregates at a temperature in the range of 150 to 700°C to prepare secondary particles; a third step of mixing the secondary particles and a binder so that the mass ratio of the secondary particles to the binder particles (secondary particles:binder particles) is 98:2 to 50:50 to prepare a mixture; a fourth step of granulating the aggregates of secondary particles using the mixture; and a fifth step of firing the aggregates of secondary particles obtained in the fourth step to obtain tertiary particles, wherein the particle size coefficient of variation (CV value) of the secondary particles obtained in the second step is 50% or less. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing a state in which the porous tertiary particles of the present invention are packed into a column and reacted. [Figure 2] FIG. 1 is a schematic diagram showing a state in which large-diameter porous secondary particles are packed into a column and reacted. [Figure 3] FIG. 1 is a schematic diagram showing a state in which small-diameter porous secondary particles are packed into a column and reacted. DETAILED DESCRIPTION OF THE INVENTION

[0012] The powder of the present invention contains porous tertiary particles, which are aggregates of porous secondary particles. The secondary particles have uniform pores, with an average pore diameter in the range of 5 to 100 nm. The tertiary particles are formed by aggregations of multiple secondary particles, and gaps exist between the secondary particles within the tertiary particles. That is, the tertiary particles have pores formed in the secondary particles and gaps between the secondary particles. The support is basically supported in the pores of the secondary particles. The pore diameter size of the secondary particles can be determined depending on the support (active component). When a reaction liquid (including a reaction gas) is passed through the gaps between the secondary particles, the reaction liquid diffuses into the pores of the secondary particles and comes into contact with the support material in the pores, allowing the support material to function effectively.

[0013] The pore size distribution (X axis: pore size, Y axis: value obtained by differentiating pore volume by pore size) is calculated for such porous tertiary particle powder. This makes it possible to know the characteristics (information) of the pore size of the group of tertiary particles contained in the powder. In this pore size distribution, the characteristics (information) of the pores of secondary particles are in the pore size range of 5 nm or more and less than 100 nm (Pd R1 ) and the characteristics (information) of the gaps between secondary particles are in the pore diameter range of 100 nm to 10,000 nm (Pd R2 ) appears.

[0014] The tertiary particle powder of the present invention has an average particle diameter d 50 The pore size distribution of the powder is in the range of 0.1 to 5.0 mm, and the pore size is in the range of 5 nm or more and less than 100 nm (Pd R1 ) the first peak is in the pore diameter range of 100 nm to 10,000 nm (Pd R2 When the pore diameter of the first peak is Pd1, the sum of the volumes of pores (PV1) between Pd1 × 0.75 and Pd1 × 1.25 is smaller than the total volume of pores with a pore diameter of less than 100 nm (PV R1 This indicates that the pore diameter of the secondary particles is uniform to a certain extent. The total volume of pores with a diameter of less than 100 nm is called the primary total volume (PV R1 ), and the total volume of pores with a pore diameter of 100 nm or more is the second total volume (PV R2 ), then PVR1 / (PV R1 +PV R2 ) is in the range of 0.2 to 0.6. This represents the ratio between the total volume of the pores of the secondary particles and the total volume of the gaps between the secondary particles. In other words, it represents the balance between the amount of supported material and the amount of reaction liquid passing through. Note that, when viewed as porous tertiary particles, both the pores of the secondary particles and the gaps between the secondary particles are considered to be pores.

[0015] Also, here, if the Y-axis value [dV / dlog(D)] is 0.2 or less, it is not considered to be a peak.

[0016] The average particle diameter of the powder is in the range of 0.1 to 5.0 mm. The tertiary particles contained in the powder are an aggregate of porous secondary particles and are larger than conventional particles. With such an average particle diameter, when the powder is packed into a column or the like, it is possible to ensure a relatively large gap between the tertiary particles, allowing the reaction liquid to flow smoothly and efficiently contacting the reaction liquid with the tertiary particles, resulting in efficient contact between the reaction liquid and the support material (active ingredient).

[0017] FIG. 1 shows a schematic diagram of a column packed with the powder (porous tertiary particles) of the present invention for reaction. The reaction liquid or reaction gas (hereinafter simply referred to as the reaction liquid) flows smoothly between the tertiary particle gaps and the secondary particle gaps, rapidly diffusing into the pores of the secondary particles. This allows efficient contact between the active component supported in the pores and the reaction liquid, thereby effectively demonstrating the performance of the active substance. On the other hand, when secondary particles of a size comparable to the tertiary particles of the present invention are used (FIG. 2), the reaction liquid is less likely to diffuse into the interior of the secondary particles and only comes into contact with the support material near the surface of the secondary particles. This results in insufficient contact between the reaction liquid and the support material, preventing the support material from fully demonstrating its performance. Furthermore, when the secondary particles constituting the tertiary particles of the present invention are used as is (FIG. 3), handling them as a powder is difficult, and the small gaps between the secondary particles make it difficult for the reaction liquid to flow, preventing efficient contact between the reaction liquid and the support material, preventing the support material from fully demonstrating its performance. It is most preferable to use it in a continuous column, but it may also be used in a batchwise vessel. Also, it can be used as an adsorbent rather than as a carrier.

[0018] The pore volume of the powder is the sum of the volume of the pores within the secondary particles and the gaps between the secondary particles, and is preferably in the range of 0.10 to 0.75 ml / g. If the pore volume is less than 0.10 ml / g, the amount of the supported material will be small. If the pore volume exceeds 0.75 ml / g, the strength of the particles will be insufficient. The pore volume is more preferably in the range of 0.20 to 0.60 ml / g, and even more preferably in the range of 0.30 to less than 0.50 ml / g.

[0019] As mentioned above, the characteristics of the pores in the secondary particles are as follows: the pore diameter is in the first range of 5 nm or more and less than 100 nm (Pd R1 ) When the pore diameter of the peak value within the first range is Pd1, it can be said that the larger the sum of the volumes of pores within Pd1 ± 25% (PV1), the more uniform the pore diameters within the secondary particles. This sum of volumes (PV1) and the total volume of pores with a pore diameter of less than 100 nm (PV R1 ) and the ratio (PV1 / PV R1) is 0.6 or more. Since the active ingredient is supported in the pores of the secondary particles, it is preferable that the pore diameter is as uniform as possible in order to efficiently contain the active ingredient. This ratio (PV1 / PV R1 ) is preferably 0.7 or more. The pore size within the secondary particles can be controlled by the size of the primary particles. This is because secondary particles are made up of uniformly sized primary particles tightly bonded together. Therefore, the average particle size of the primary particles can be set according to the size of the active ingredient.

[0020] The characteristics of the secondary particle gaps are in the second range of pore diameters between 100 nm and 10,000 nm (Pd R2 ) is expressed in terms of the total volume of the secondary particle gaps (PV R2 ) needs to be increased. R2 / (PV R1 +PV R2 The value of (PV2) is set in the range of 0.4 to 0.8, preferably in the range of 0.5 to 0.75. In this case, the sum of the volumes of pores (PV2) within ±25% of the pore diameter Pd2 of the peak value in the second range and the total volume of pores with a pore diameter of 100 nm or more (PV R2 ) and the ratio (pore diameter peak ratio: PV2 / PV R2 The larger the pore diameter, the more uniform the gaps between the secondary particles. The peak rate of pore diameters of 100 nm or more is preferably 30% or more. PV, which corresponds to the total volume of the pores in the secondary particles, R1 and PV, which corresponds to the total volume of the secondary particle voids. R2 It is necessary to form tertiary particles so as to achieve a balance between the above.

[0021] To form such tertiary particles, it is preferable to optimize the size and distribution of the secondary particles. That is, the particle coefficient of variation (CV value) of the secondary particles is preferably less than 50%. The smaller the particle coefficient of variation, the more uniform the size of the secondary particles will be, and the easier it will be to uniform the pore diameter within the tertiary particles. This allows the reaction liquid to flow evenly inside the tertiary particles, improving reaction efficiency.

[0022] It is also preferable to optimize the pore size distribution of the secondary particles. That is, when the pore size value corresponding to the maximum value on the Y axis is the peak pore size Pd, the sum of the volumes (PV) of pores greater than or equal to Pd × 0.75 and less than or equal to Pd × 1.25 is preferably 70% or more of the total volume (TPV) of all pores. Furthermore, to make the pores in the secondary particles uniform, it is preferable that the primary particles have a particle size coefficient of variation (CV value) of 2 to 10%, an average particle size of 10 to 300 nm, and a sphericity of 0.85 or more.

[0023] In addition, by binding secondary particles together with a binder, the strength of the tertiary particles is improved. When secondary particles are bonded together with a binder, the binder exists in the gaps between the particles, and the PV, which corresponds to the total volume of the gaps between the secondary particles, is increased. R2 Therefore, when a binder is added, the mass ratio of the secondary particles to the binder (secondary particles:binder) needs to be 98:2 to 50:50. This mass ratio is preferably 95:5 to 75:25, and more preferably 90:10 to 70:30.

[0024] The porosity of the tertiary particles is preferably in the range of 15 to 65%. If the porosity is less than 15%, the amount of support will be small and it will not be practical. If the porosity is more than 65%, the strength of the particles may not be maintained. The porosity is more preferably in the range of 30 to 60%, and even more preferably in the range of 40 to 55%.

[0025] The tertiary particles may have various shapes depending on the application, including spherical shapes such as ellipsoids and circles, as well as cylindrical and rod-like shapes.

[0026] [Method of manufacturing porous tertiary particles] The porous tertiary particles described above can be produced, for example, as follows: a first step of preparing a dispersion of primary particles, which are silica particles having an average particle size of 10 to 300 nm, a particle size coefficient of variation of 10% or less, and a sphericity of 0.85 or more; a second step of spraying a spray containing the dispersion of primary particles into an airflow to granulate aggregates of the primary particles and heat-treating the aggregates at a temperature in the range of 150 to 700°C to prepare secondary particles having a particle size coefficient of variation (CV value) of 50% or less; a third step of mixing the secondary particles with a binder so that the mass ratio of the secondary particles to the binder particles (secondary particles:binder particles) is 98:2 to 50:50; a fourth step of granulating the aggregates of secondary particles using the mixture obtained in the third step; and a fifth step of firing the aggregates of secondary particles obtained in the fourth step to obtain tertiary particles.

[0027] Each step will be described below. (first step) In this step, a dispersion of silica particles (primary particles) with a particle size variation coefficient of 10% or less, an average particle size of 10 to 300 nm, and a sphericity of 0.85 or more is prepared. For example, a dispersion of spherical silica particles with an average particle size of 10 to 300 nm, preferably 10 to 100 nm, is prepared, and centrifuged to separate coarse particles, adjusting the particle size variation coefficient to within the range of 2 to 10%.

[0028] (Second process) The spray liquid containing the primary particles obtained in the first step is sprayed into an airflow to granulate aggregates of primary particles. The granulated aggregates are fired at 150 to 700°C to form secondary particles. If tertiary particles are granulated without firing, the secondary particles will be destroyed, making it impossible to obtain a good pore size distribution. Furthermore, it is preferable to classify the granulated aggregates in order to reduce the particle coefficient of variation (CV value) of the secondary particles. The classification conditions are adjusted so as to obtain the desired CV value. Classification is preferably performed before firing.

[0029] The solvent for the spray liquid can be water or an organic solvent, such as monohydric alcohols such as ethanol, propanol, and butanol, or polyhydric alcohols such as ethylene glycol.

[0030] The particle concentration in the spray liquid is preferably in the range of 2 to 60% by mass, more preferably in the range of 4 to 50% by mass. By performing spray drying within this concentration range, desired secondary particles can be stably obtained.

[0031] As the spray drying method, a conventionally known method such as a rotating disk method, a pressure nozzle method, a two-fluid nozzle method, etc. In particular, the two-fluid nozzle method disclosed in Japanese Patent Publication No. 2-61406 is preferred because it can obtain secondary particles with a uniform particle size distribution and it is easy to control the average particle size.

[0032] The drying temperature at this time varies depending on the concentration of the primary particle dispersion, the processing speed, etc., but for example, the inlet temperature of the spray dryer is preferably in the range of 100 to 300° C. and the outlet temperature is preferably in the range of 40 to 100° C. More preferably, the inlet temperature is in the range of 210 to 250° C. and the outlet temperature is in the range of 50 to 55° C. The spray rate also depends on the shape of the spray dryer, etc., but is preferably in the range of 0.1 to 3 L / hour, for example.

[0033] (Third step) In this step, the secondary particles and binder were mixed so that the mass ratio of the secondary particles to the binder (secondary particles:binder) was 98:2 to 50:50. This mass ratio is preferably 95:5 to 75:25, and more preferably 90:10 to 70:30. As the binder, the primary particles prepared in the first step or a layered silicate may be used.

[0034] (Fourth step) In this step, a molding aid was mixed with the mixture prepared in the third step and kneaded to a uniform consistency. The resulting kneaded mixture was molded using an extrusion molding machine and a tumbling granulator. Adding a molding aid can prevent adhesion during granulation and also produce a molded product with sufficient compressive strength. When a molding aid is used, the amount added is preferably 15% by mass of the total solids, more preferably 1 to 10% by mass. If the amount of molding aid added exceeds 15% by weight of the total solids, powdering during spheronization and the resulting molded product tends to have reduced compressive strength and abrasion resistance. Examples of molding aids include crystalline cellulose, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, starch, and lignin.

[0035] (Fifth step) In this step, the molded body obtained in the fourth step is fired to obtain porous tertiary particles. Firing can increase the bonding strength between the secondary particles. The heat treatment temperature is preferably 150°C or higher. The temperature range at which firing is possible varies depending on the binder used. When silica particles are used as the binder, a firing temperature of 150 to 700°C is suitable. When layered silicate is used as the binder, high strength can be obtained by setting the firing temperature to 1000°C. In general, if the temperature is too high, the particles may shrink, which may result in smaller voids between the final secondary particles.

[0036] The tertiary particles thus obtained may be surface treated by the following steps. The tertiary particles are allowed to cool or are cooled to room temperature to 40°C, and then dispersed in water and / or an organic solvent to prepare a dispersion. Examples of organic solvents that can be used include monohydric alcohols such as ethanol, propanol, and butanol, and polyhydric alcohols such as ethylene glycol. The particle concentration in the dispersion is preferably in the range of 0.1 to 40% by mass, and more preferably in the range of 0.5 to 20% by mass.

[0037] The following i) or ii) is added to this dispersion to perform surface treatment on the outer surfaces of the tertiary particles. i) Acid or alkali ii) An acid or alkali and an organosilicon compound represented by the following general formula and / or its partial hydrolyzate General formula: R n Si(OR′) 4-n (wherein R and R' are hydrocarbon groups selected from alkyl groups having 1 to 18 carbon atoms, aryl groups having 1 to 18 carbon atoms, vinyl groups, and acrylic groups, and n is an integer of 0, 1, 2, or 3.)

[0038] In case i), an aqueous solution of an acid or alkali is usually used. The type of acid or alkali is not particularly limited, but examples include an aqueous solution of hydrochloric acid, an aqueous solution of boric acid, and an aqueous solution of ammonium.

[0039] The acid or alkali in case ii) is defined in the same way as in case i). Specific examples of the organosilicon compound represented by the general formula include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, 3,3,3-trifluoropropyltrimethoxysilane, methyl-3,3,3-trifluoropropyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxytripropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrieth ... Examples of the silane include γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, trimethylsilanol, methyltrichlorosilane, methyldichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, vinyltrichlorosilane, trimethylbromosilane, and diethylsilane.

[0040] The acid or alkali added together with the organosilicon compound and / or its partial hydrolyzate also functions as a catalyst for hydrolysis, but a hydrolysis catalyst may also be added if desired. When a basic catalyst such as an alkali metal hydroxide, aqueous ammonia, or an amine is used as the hydrolysis catalyst, the basic catalyst can be removed after hydrolysis and the resulting solution can be used as an acidic solution. When an acidic catalyst such as an organic acid or inorganic acid is used to prepare the hydrolyzate, it is preferable to remove the acidic catalyst by ion exchange or the like after hydrolysis. The obtained hydrolyzate of the organosilicon compound is preferably used in the form of an aqueous solution. Here, "aqueous solution" refers to a state in which the hydrolyzate is transparent and not in a cloudy gel state.

[0041] Next, the silica particles are separated from the obtained dispersion, dried, and then heat-treated at 100 to 300° C. This gives surface-treated tertiary particles.

[0042] Examples of the present invention will be specifically described below. [Example 1] (Granulation of secondary particles) 5000 g of commercially available silica sol (JGC Catalysts and Chemicals: SS-160 [average particle size 160 nm, silica concentration 18% by mass]) was centrifuged to remove coarse particles. A continuous high-speed centrifuge (Kokusan H-660) was used, and the silica sol was continuously injected into a rotor (QNS model, 1 L capacity) at 9000 G and a rate of 400 g / min, followed by collection. This allowed the coarse particles to settle within the rotor.

[0043] The recovered silica sol (A1) contains spherical silica microparticles (primary particles). This silica sol was diluted with water to a silica concentration of 15% by mass. 2000 g of this water-diluted product was subjected to cation exchange and adjusted to a pH of 2.0. A silicic acid solution (silica concentration 4.8% by mass) was added to this silica sol and stirred. This resulted in a slurry. The mass ratio of silica in the silica sol to silica in the silicic acid solution was approximately 9:1.

[0044] The resulting slurry was subjected to a spray dryer, where it was spray-dried to produce aggregates of primary particles (secondary particles). The slurry was supplied to one of the two-fluid nozzles at a flow rate of 2 L / Hr, and gas was supplied to the other nozzle at a pressure of 0.75 MPa. The inlet temperature of the spray dryer was set at 240°C, and the outlet temperature was 50-55°C. The granulated powder was calcined at 450°C for 3 hours to obtain porous secondary particles.

[0045] (Tertiary particle granulation) These secondary particles were mixed with a molding aid (Isoban-110 manufactured by Kuraray Co., Ltd.) and kneaded uniformly using a Henschel mixer. The formulation is shown in Table 1. The resulting kneaded material was molded using an extrusion molding machine and a tumbling granulator, and then fired at 600°C. It was then classified using a sieve. Here, the material was passed through a 1.4 mm sieve and then further passed through a 0.8 mm sieve. The material remaining on the sieve was collected to obtain a powder of tertiary particles.

[0046] [Table 1] The physical properties of the powder obtained as described above were measured and evaluated as follows. The results, along with the preparation conditions, are shown in Table 1. The same procedures were basically carried out in other examples and comparative examples.

[0047] 1) Average particle size and particle coefficient of variation (CV value) of powder (porous tertiary particles) Using a scanning electron microscope (JEOL, JSM-5300 model), the powder was photographed (3,000x magnification) so that tertiary particles did not overlap, and the particle diameter was measured from the photograph with a vernier caliper. The minor and major diameters were measured, and the particle diameter was calculated as (minor diameter + major diameter) / 2. The particle diameters of 20 particles were determined, and their average value was taken as the average particle diameter. The standard deviation of the particle diameters was also determined, and the particle variation coefficient was calculated using the formula "(CV value) = (particle diameter standard deviation (σ) / average particle diameter (Dn)) × 100 (%)".

[0048] 2) Pore size distribution, peak pore size, pore volume Ten grams of powder was placed in a crucible and dried at 300°C for 1 hour. After cooling to room temperature in a desiccator, the pore size distribution was measured by mercury intrusion using an automatic porosimeter (Counterchrome Instruments, PoreMaster PM33GT). Specifically, mercury was intruded at pressures ranging from 1.5 kPa to 231 MPa, and the pore size distribution (X-axis: pore size, Y-axis: pore volume differentiated by pore size) was obtained from the relationship between pressure and pore size. This method allowed mercury to be intruded into pores ranging from approximately 5 nm to approximately 1000 μm. The pores present inside the secondary particles and the gaps between the secondary particles are reflected in the pore size distribution. The pore size distribution for the pores present inside the secondary particles is in the pore size range of 5 to less than 100 nm. The pore size corresponding to the peak value in this range was designated the peak pore size Pd1. That is, the pore diameter (X-axis) corresponding to the maximum value on the Y-axis within this range was taken as the peak pore diameter. The gaps between secondary particles (secondary particle gaps) appear in the pore diameter distribution in the pore diameter range of 100 to 10,000 nm. The pore diameter corresponding to the peak value (maximum value) within this range was taken as the peak pore diameter Pd2. The pore volume was calculated based on this pore diameter distribution.

[0049] 3) Specific surface area 10 g of sample was placed in a crucible, dried at 300°C for 1 hour, and then cooled to room temperature in a desiccator. 0.15 g was placed in a glass cell, and nitrogen gas was adsorbed onto the sample while it was being evacuated using a Belsorp mini II (manufactured by Japan Bell Co., Ltd.), and the specific surface area was determined.

[0050] 4) Porosity The porosity was calculated from the pore volume determined by the mercury injection method using the following formula (1). 3 / g) is the volume of 1g of silica, and the density of silica is 2.2g / cm 3 was calculated from Porosity (%) = (pore volume / (pore volume + 0.4545)) × 100 Equation (1)

[0051] 5) Strength The strength of 20 particles was measured using a texture analyzer (TA XT Plus, manufactured by Stable Micro Systems), and the average value was calculated.

[0052] The properties of the primary particles and secondary particles were measured as follows: Properties other than those listed below can be measured in the same way as for tertiary particles.

[0053] 6) Average particle size of primary particles, coefficient of variation of particle size (CV value) The particles were photographed (magnification 250,000 times) using a scanning electron microscope (JEOL, JSM-5300 model), and the average particle size of 250 particles in this image was measured using an image analyzer (Asahi Kasei, IP-1000), and the coefficient of variation (CV value) was calculated. Specifically, the particle size of each of the 250 particles was measured, and the average particle size and standard deviation of the particle size were calculated from the values. The coefficient of variation of the particles was calculated using the above formula.

[0054] 7) Average particle size of secondary particles, coefficient of variation of particle size (CV value) The particle size distribution was measured in a dry state using a laser diffraction / scattering particle size distribution analyzer (Seishin Enterprise Co., Ltd. Laser Micronsizer LMS-3000). This device calculates the average particle size and CV value of porous secondary particles.

[0055] [Example 2] A binder was added during granulation of the tertiary particles. The silica sol (A1) used as the material for the secondary particles in Example 1 was used as the binder. Except for this, porous tertiary particles were prepared in accordance with Example 1.

[0056] [Example 3] When granulating the tertiary particles, layered silicate (Sumecton-SA, manufactured by Kunimine Industries Co., Ltd.) was added as a binder. Except for this, porous tertiary particles were prepared in accordance with Example 1. The unit crystal of the layered silicate used here had a thickness of 1 nm and a width of 100 to 1,000 nm.

[0057] [Example 4] In Example 3, when granulating the tertiary particles, after firing at 600° C., the particles were further fired at 1000° C. for 3 hours. Except for this, porous tertiary particles were prepared in the same manner as in Example 1.

[0058] [Example 5] In Example 2, the particles remaining on the 1.4 mm sieve during classification were collected as porous tertiary particles.

[0059] [Example 6] In Example 2, the particles that passed through a 0.8 mm sieve were collected as porous tertiary particles.

[0060] [Example 7] Aggregates of primary particles (secondary particles) were granulated in the same manner as in Example 1. Next, using a cyclone manufactured by our company, the flow rate of the powder transport line was set to 5 m / s, and the granulated powder was subjected to dry centrifugal classification (classification process). Particles that passed through the cyclone without being captured were collected using a bag filter. This allows for the removal of coarse particles. The classified powder was fired at 450°C for 3 hours to obtain porous secondary particles. In this example, the secondary particles were classified so that the CV value was 35%. Other than this, tertiary particles were granulated in the same manner as in Example 1.

[0061] [Example 8] Classification was carried out in the same manner as in Example 7, and tertiary particles were granulated in the same manner as in Example 2 except for this.

[0062] [Example 9] Classification was carried out in the same manner as in Example 7, and tertiary particles were granulated in the same manner as in Example 3 except for this.

[0063] [Example 10] The classification treatment of Example 7 was carried out twice in succession. In this example, classification was carried out so that the CV value of the secondary particles was 25%. Other than this, tertiary particles were granulated in the same manner as in Example 7.

[0064] [Comparative Example 1] During granulation of the tertiary particles, 80 nm silica sol (SI-80P manufactured by JGC Catalysts and Chemicals, average particle size 80 nm, concentration 40 mass%) was used as a binder. Except for this, porous tertiary particles were prepared in accordance with Example 1.

[0065] Comparative Example 2 The secondary particles were prepared in the same manner as in Example 2 except that the granulated powder was not fired.

[0066] Comparative Example 3 In Example 2, when the tertiary particles were granulated, after the sintering at 600° C., the particles were further sintered at 1000° C. for 3 hours to obtain porous tertiary particles.

[0067] [Table 2]

Claims

1. A powder of porous tertiary particles formed by the aggregation of porous secondary particles, The powder has an average particle size in the range of 0.1 to 5.0 mm, In the pore size distribution of the powder (X axis: pore size, Y axis: value obtained by differentiating pore volume with pore size), the pore size is in the range of 5 nm or more and less than 100 nm (Pd Ｒ１ ) the first peak is in the pore diameter range of 100 nm or more and 10,000 nm or less (Pd Ｒ２ ) there is a second peak, The total volume of pores having a pore diameter of less than 100 nm is defined as the first total volume (PV Ｒ１ ), and the total volume of pores having a pore diameter of 100 nm or more is defined as the second total volume (PV Ｒ２ ) and then PV Ｒ１ / (PV Ｒ１ +PV Ｒ２ ) is in the range of 0.2 to 0.6, When the pore diameter of the first peak is Pd1, the sum of the volumes of pores of Pd1 × 0.75 or more and Pd1 × 1.25 or less (PV １ ) is the first total volume (PV Ｒ１ ) powder having 60% or more of the above.

2. 2. The powder according to claim 1, wherein the secondary particles have a particle coefficient of variation (CV value) of less than 50%.

3. 2. The powder according to claim 1, wherein, in a pore size distribution of the secondary particles (X axis: pore size, Y axis: value obtained by differentiating pore volume with pore size), when the pore size value corresponding to the maximum value on the Y axis is defined as a peak pore size Pd, the sum of the volumes (PV) of pores that are Pd × 0.75 or more and Pd × 1.25 or less is 70% or more of the total volume (TPV) of all pores.

4. 2. The powder according to claim 1, wherein the primary particles constituting the secondary particles have a particle size coefficient of variation (CV value) of 2 to 10%, an average particle size of 10 to 300 nm, and a sphericity of 0.85 or more.

5. 2. The powder according to claim 1, wherein the secondary particles are bonded together with a binder to form tertiary particles.

6. a first step of preparing a dispersion of primary particles, which are silica particles having an average particle size of 10 to 300 nm, a particle size variation coefficient of 10% or less, and a sphericity of 0.85 or more; a second step of spraying a spray liquid containing a dispersion of the primary particles into an air stream to granulate aggregates of the primary particles, and then heat-treating the aggregates at a temperature in the range of 150 to 700°C to prepare secondary particles; a third step of preparing a mixture by mixing the secondary particles and a binder so that the mass ratio of the secondary particles to the binder particles (secondary particles:binder particles) is 98:2 to 50:50; a fourth step of granulating the aggregates of the secondary particles using the mixture; a fifth step of firing the aggregate of secondary particles obtained in the fourth step to obtain tertiary particles, A method for producing porous tertiary particles, wherein the secondary particles obtained in the second step have a particle size coefficient of variation (CV value) of 50% or less.

7. 7. The method for producing porous tertiary particles according to claim 6, wherein, in the pore size distribution of the secondary particles obtained by the second step (X axis: pore size, Y axis: value obtained by differentiating pore volume with pore size), when the pore size value corresponding to the maximum value on the Y axis is defined as the peak pore size Pd, the sum of the volumes (PV) of pores equal to or greater than Pd × 0.75 and equal to or less than Pd × 1.25 is 70% or more of the total volume (TPV) of all pores.

8. 7. The method for producing porous tertiary particles according to claim 6, wherein the primary particles are used as the binder.

9. 9. The method for producing porous tertiary particles according to claim 8, wherein the aggregate of secondary particles is fired at 150 to 700° C. in the fifth step.

10. 7. The method for producing porous tertiary particles according to claim 6, wherein a layered silicate is used as the binder.

Images