JP7254319B2 - Manufacturing method of porous rutile titania particles - Google Patents

Description

TECHNICAL FIELD The present invention relates to porous rutile titania particles and a method for producing the same.

Titania has been widely used in paints, pigments, cosmetics, catalysts and catalyst carriers. In addition, several reports have been made on porous titania particles (for example, Patent Documents 1 to 3, etc.). Patent Document 1 discloses spherical porous anatase-titania fine particles composed of spherical particles in which anatase-type ultrafine crystals having a crystallite diameter of 300 Å or less are aggregated. Patent Document 2 describes porous titania particles having an average particle diameter of 0.5 to 2.0 μm and a specific surface area of 100 m ² /g or more, formed by aggregation of titania nanoparticles having a primary particle diameter of 5 to 30 nm. disclosed. In the porous titania particles of Patent Document 2, the crystal form of anatase is completely retained when fired at 800°C, and only a portion of the anatase transitions to rutile even when fired at 1000°C. Patent Document 3 discloses a titania pigment for cosmetics having an average particle size of 0.1 to 5 μm, a pore diameter peak of 5 to 50 nm, and a pore volume of 0.05 to 0.3 cm ³ /g. there is Patent Document 3 explains that if the baking temperature of the titania pigment is higher than 600° C., rutile-type titania is partially formed and changes its shape, which is undesirable.

On the other hand, Patent Document 4 describes hollow titanium oxide particles having a crystal form of rutile, an average particle diameter of 0.31 μm, an average pore diameter of 28.3 nm, and a pore volume of 0.024 cm ³ /g. Something is stated. Also, in Non-Patent Document 1, when amorphous titania particles are treated at a sintering temperature of 900° C., they all become rutile, and the pore volume is 1.33×10 ⁻⁷ m ³ /g (0.133 cm ³ / g).

JP-A-4-367512 JP 2007-230824 A JP 2013-28563 A JP 2017-114721 A

J. Mater. Sci., Vol.37, No.7, pp.1455-1460, 2002

However, Patent Documents 1 to 3 do not describe porous titania particles whose main crystal form is rutile. Although Patent Document 4 describes hollow titanium oxide particles, it does not describe porous titania particles that can be impregnated with chemical components. Hollow titanium oxide particles are weak in strength and may be crushed during use. Although Non-Patent Document 1 describes the properties of aggregates of rutile-type titania particles, the properties of individual titania particles are unknown.

The present invention has been made in order to solve the above-mentioned problems, and the main object of the present invention is to provide porous rutile-type titania particles whose main crystal form is rutile and which can carry an active ingredient.

The porous rutile-type titania particles of the present invention have an average particle size of 0.5 μm or more, a large number of pores on the surface, a porosity of 10% or more, and a rutilization rate of 95% or more.

The porous rutile titania particles have a large number of pores on the surface and a porosity of 10% or more. Therefore, active ingredients (for example, functional ingredients such as hyaluronic acid and enzymes) can be supported. Moreover, the main crystal type of the porous rutile-type titania particles is the rutile type. Since the rutile type has a lower photocatalytic function than the anatase type, it has less effect on living organisms. Therefore, the porous rutile-type titania particles are expected to be used for cosmetics, etc., in which an active ingredient is carried in the pores and applied to the skin.

1 is a photograph of an SEM image of porous rutile-type titania particles of Experimental Example 1. FIG.

The porous rutile titania particles of this embodiment have a large number of pores on the surface. Having a large number of pores on the particle surface can be easily recognized, for example, by observing an SEM image of the porous rutile titania particles at a magnification of 5,000.

The porous rutile-type titania particles of this embodiment have an average particle size of 0.5 μm or more, a porosity of 10% or more, and a rutilization rate of 95% or more. If the porosity is 10% or more, a relatively large amount of active ingredients can be supported. Further, when the rutilization rate is high, the porosity tends to decrease, but even if the rutilization rate is 100%, the porosity can be increased to 10% or more by adopting the manufacturing method described later. The porosity of the porous rutile-type titania particles of the present embodiment is preferably 10% or more and 70% or less, more preferably 10% or more and 50% or less. Considering the strength, the porosity is preferably 35% or less. The rutilization rate is preferably 98% or more.

The porous rutile titania particles of the present embodiment are not particularly limited, but have an average particle size of 0.5 μm or more and 30 μm or less (preferably 0.5 μm or more and 10 μm or less), and pores measured by a nitrogen adsorption method It is preferable that the peak in the distribution is in the range of 30 nm or more and 200 nm or less. Also, the specific surface area is preferably 1 m ² /g or more, more preferably 10 m ² /g or more. The pore volume is preferably 0.027 cm ³ /g or more, more preferably 0.25 cm ³ /g or more. The porous rutile-type titania particles may have one peak in the pore distribution range of 30 nm to 100 nm and one peak in the range of 80 nm to 200 nm.

The porous rutile-type titania particles of the present embodiment are produced, for example, by the following production examples. However, the porous rutile-type titania particles may be produced by methods other than the following production examples.

[Manufacturing example]
In this production example, (a) a dispersion containing soluble particles that are soluble in a predetermined liquid, a titanium (IV) alkoxide, a chelating agent, a phase separation agent, and an inorganic salt, and in which the soluble particles are dispersed is stirred. (b) removing the chelating agent from the obtained gel; and (c) after removing the chelating agent and first baking the gel at a baking temperature of 800° C. or higher and 1000° C. or lower. (d) obtaining primary fired particles from which the soluble particles have been removed by immersing them in a predetermined liquid to dissolve the soluble particles in the predetermined liquid; and a step of secondary firing at a firing temperature of 900° C. or less to obtain porous rutile-type titania particles.

- Step a: Gelation step Particles that dissolve in a predetermined liquid are used as the soluble particles. Examples of the predetermined liquid include an alkaline solution and the like. In that case, particles that dissolve in an alkaline solution are used as the soluble particles. Examples of such particles include silica particles and silicate particles (silicate glass particles, etc.). Silica particles are used to form pores in titania particles, and the particle size is preferably 7 to 500 nm, more preferably 20 to 300 nm, even more preferably 30 to 200 nm. Silica particles include hydrophilic ones and hydrophobic ones, and either one may be used. Examples of silica particles include Seahoster (registered trademark) KE-S10 and KE-P10 manufactured by Nippon Shokubai Co., Ltd., trade name NAX-50 manufactured by Nippon Aerosil Co., Ltd., and the like. The amount of soluble particles used is preferably 2 to 50% by weight, more preferably 5 to 40%, relative to titanium (IV) alkoxide.

Examples of titanium (IV) alkoxides include titanium (IV) methoxide, titanium (IV) ethoxide, titanium (IV) n-propoxide, titanium (IV) isopropoxide, titanium (IV) n-butoxide, and titanium (IV). isobutoxide, titanium (IV) sec-butoxide, titanium (IV) tert-butoxide and the like. Among these, titanium (IV) n-propoxide and titanium (IV) isopropoxide are preferred.

As the chelating agent, those capable of coordinating with titanium ions and decarboxylating after hydrolysis are preferred, and examples thereof include β-ketoesters. Examples of β-ketoesters include alkyl acetoacetates such as ethyl acetoacetate. The molar ratio of the chelating agent to titanium (IV) alkoxide is preferably 0.1 to 2.0, more preferably 0.5 to 1.5.

A phase separation agent is an additive substance for forming primary pores and a substance that induces phase separation in a sol-gel reaction. Phase separation agents that generally cause spinodal decomposition include, for example, cellosolves such as methyl cellosolve and ethyl cellosolve, esters such as ethylene glycol monomethyl ether acetate and propylene glycol monomethyl ether acetate, polyethylene glycol, polypropylene glycol, and triethylene glycol. , glycols such as diethylene glycol. Polyalkylene glycols such as polyethylene glycol and polypropylene glycol are preferable for forming the porous rutile titania particles of the present embodiment, and the molecular weight is preferably 400 to 500,000, more preferably 1,000 to 100,000. Polyalkylene glycols are sometimes referred to as polyalkylene oxides depending on their molecular weight, but in the present specification, they are collectively referred to as polyalkylene glycols. The particle size can be controlled by adjusting the molecular weight and addition amount of the phase separation agent. A phase separation agent may use not only one type but also multiple types together. The amount of the phase separation agent used is preferably 1 to 300% by weight, more preferably 5 to 200%, relative to the titanium (IV) alkoxide.

As the inorganic salt, a salt containing a conjugate base of a strong acid is preferred. Conjugate bases of strong acids include, for example, nitrate ions and halogen ions. Such inorganic salts include, for example, ammonium nitrate, ammonium chloride, ammonium bromide, ammonium iodide, and the like. Note that the conjugate base of the strong acid functions as a blocking agent to prevent exposure of the titanium atoms to nucleophilic reactions. The amount of the inorganic salt to be used is preferably 0.005 to 0.5, more preferably 0.01 to 0.3 in molar ratio to titanium (IV) alkoxide.

Gelation is performed by, for example, adding an aqueous solution of an inorganic salt dropwise to a dispersion obtained by dispersing soluble particles in a mixed solution of a chelating agent, a phase separation agent, and a titanium (IV) alkoxide dissolved in a solvent, and gelling the mixture while stirring. Let After that, it is allowed to stand for an appropriate time to complete gelation. Stirring is for homogenizing the reaction system. Alternatively, a chelating agent, soluble particles and a solvent are placed in a pot mill, pulverized, and classified if necessary, a phase separating agent is added, titanium (IV) alkoxide is added to chelate, and an aqueous solution of an inorganic salt is added thereto. may be added dropwise and gelled under stirring. Examples of the solvent include, but are not particularly limited to, alcohol solvents, ester solvents, glycol solvents, and the like. A titania sol in which the soluble particles are dispersed is obtained by dropping an aqueous solution of an inorganic salt into the dispersion in which the soluble particles are dispersed. The temperature of the dispersion when the titania sol is dropped and the temperature of the titania sol when the titania sol is allowed to stand may be appropriately set. When the titania sol gels, phase separation occurs and solid-liquid separates to form a titania skeleton (solid phase) and a network portion (liquid phase) forming a three-dimensional network structure. is considered to separate into At this time, soluble particles are attached to the surface of the titania particles. That is, when looking at one soluble particle, part of it is buried in the surface of the titania particle and the rest is exposed on the surface of the titania particle. Silica and the like used for the soluble particles are fine and tend to aggregate, so instead of single particles, a part of the aggregates may be buried on the surface of the titania particles. The stirring method is not particularly limited, and examples thereof include a method using a stirrer (such as a magnetic stirrer bar), a method using a stirring blade, and a method using vibration.

- Process b: Chelating agent removal process A chelating agent is removed from the obtained gel. If a β-ketoester is used as the chelating agent, an alcohol-water mixture is used to remove the chelating agent. In this step, gas is generated due to hydrolysis of the β-ketoester followed by decarboxylation. Therefore, it is preferable to perform this step while the container is open without being sealed. If the obtained gel is immediately immersed in water, carbon dioxide is rapidly generated due to the decomposition of the chelating agent, resulting in cracks, which is not preferable. By removing the chelating agent, titania in the resulting gel is believed to change from amorphous to crystalline (eg, anatase crystals).

- Step c: primary firing step and soluble particle removal step The gel after removing the chelating agent is first fired at a firing temperature of 800°C or higher and 1000°C or lower, and then immersed in a predetermined liquid to remove the soluble particles from the predetermined liquid. to obtain primary fired particles from which soluble particles have been removed. Since the firing temperature is set in the range of 800° C. or more and 1000° C. or less, most of the organic compounds (for example, chelating agent) remaining in the gel are burned off. If the firing temperature exceeds 1000° C., the porosity becomes too low although the rutilization ratio increases, which is not preferable. If the firing temperature is lower than 800° C., the porosity increases, but the rutilization rate becomes too low, which is not preferable. It is presumed that the soluble particles play a role in preventing sintering of the titania particles during firing. Also, during firing, after the anatase type is once generated, it transitions to the rutile type while maintaining the porosity. It is presumed that pores remain in the rutile-type titania particles because the soluble particles inhibit particle size enlargement even when the rutile-type titania particles are formed. The firing time may be appropriately set, and may be, for example, 2 hours or more and 10 hours or less. After sintering, the soluble particles are dissolved in a predetermined liquid and removed to obtain primary sintered particles having pits. The pits are the portions after the soluble particles adhering to the surface of the primary fired particles are dissolved and removed, and finally become pores of the porous rutile titania particles.

Step d: Secondary firing step The primary fired particles from which the soluble particles have been removed are subjected to secondary firing at a firing temperature of 700°C or higher and 900°C or lower to obtain porous rutile titania particles. Before the secondary firing, pulverization and classification may be performed as necessary. In the primary baking of step c, once the anatase form is produced, it transitions to the rutile form while maintaining its porosity, but the transition to the rutile form does not proceed sufficiently. A possible reason for this is that the soluble particles contained in the gel inhibit the transition to the rutile type. Therefore, in step d, the primary fired particles from which the soluble particles have been removed are secondary fired at a firing temperature of 700° C. or higher and 900° C. or lower. At this stage, the primary sintered particles do not contain soluble particles, so the transition to the rutile type proceeds smoothly. If the firing temperature exceeds 900° C., the porosity becomes too low although the rutile rate increases, which is not preferable. If the firing temperature is lower than 700° C., the porosity increases, but the rutilization rate becomes too low, which is not preferable.

The porous rutile-type titania particles of this embodiment described above have a large number of pores on the surface, an average particle size of 0.5 μm or more, and a porosity of 10% or more. Therefore, active ingredients (for example, functional ingredients such as hyaluronic acid and enzymes) can be supported. Moreover, the main crystal type of the porous rutile-type titania particles is the rutile type. Since the rutile type has a lower photocatalytic function than the anatase type, it has less effect on living organisms. Therefore, the porous rutile-type titania particles are expected to be used for cosmetics, etc., in which an active ingredient is carried in the pores and applied to the skin. The pores may be depressions on the surface, or may extend inward from the surface.

Further, according to the method for producing porous rutile-type titania particles described above, after obtaining the primary fired particles having pits by removing the soluble particles adhering to the surface of the primary fired particles, the primary fired particles By further secondary firing, porous rutile-type titania particles having a very high rutile ratio and a relatively high porosity can be obtained.

It goes without saying that the present invention is not limited to the above-described embodiments, and can be implemented in various forms as long as they fall within the technical scope of the present invention.

For example, in the above-described embodiment, a production example including steps (a) to (d) was shown, but step (d), that is, the secondary firing step may be omitted. In that case, in step (c), it is preferable to bake the gel after removing the chelating agent at a baking temperature of 950° C. or more and 1050° C. or less.

[Experimental example 1]
Porous rutile-type titania particles were produced as follows.
・ Gelation process 1-propanol (manufactured by Tokyo Kasei) 2.0 g, ethyl acetoacetate (manufactured by Tokyo Kasei) 2.58 g, and hydrophilic silica particles as soluble particles (Nippon Shokubai, Seahoster (registered trademark) KE- 1.0 g of P10 (particle size: about 100 nm) was placed in a pot mill and pulverized for 20 hours. Subsequently, 1.1 g of polyethylene glycol having a molecular weight of 2000 (PEG2000, manufactured by Aldrich) was added as a phase separation agent to the mixed liquid after pulverization, and the mixture was stirred at 60°C for 30 minutes, and then the liquid temperature was lowered to 40°C. 5.04 g of titanium (IV) propoxide (manufactured by Aldrich) was added thereto and stirred at 40° C. for 30 minutes for chelation reaction. Subsequently, 1 mL of 1 M ammonium nitrate aqueous solution was added dropwise at 40° C. while sufficiently stirring with a stirrer, and after gelation, the mixture was allowed to stand at 60° C. for 24 hours for phase separation.

- Chelating Agent Removal Step A solution of ethyl alcohol:water (mass ratio) of 1:1 was put in a container that had finished gelation, and the solution was discarded after standing at room temperature for 6 hours. Subsequently, the container was filled with water and immersed at room temperature for 18 hours. In this step, the chelating agent ethyl acetoacetate was hydrolyzed to acetoacetic acid, and the acetoacetic acid was rapidly decarboxylated to produce acetone and carbon dioxide gas. Subsequently, water was distilled off from the gel after removing the chelating agent, and the gel was dried by heating at 70° C. for 24 hours.

- Primary firing step and silica particle removal step A sufficiently dried gel was heated to 800°C at a rate of temperature increase of 1°C per minute, and then held at that temperature for 2 hours to perform primary firing. The primary fired particles were placed in 43 mL of a 1 M sodium hydroxide aqueous solution, allowed to stand at room temperature for 24 hours, the aqueous solution was discarded, and then washed several times with ion-exchanged water to dissolve and remove the silica particles from the surfaces of the primary fired particles. . The primary fired particles from which the silica particles were removed were vacuum-dried at 100° C. for 24 hours.

-Secondary calcination process The dried, primarily calcined particles were heated to 700°C at a rate of temperature increase of 1°C per minute, and then held at that temperature for 2 hours for secondary calcination. FIG. 1 shows a photograph of an SEM image (5000 times) of the obtained secondary fired particles. From FIG. 1, it can be seen that the obtained secondary fired particles have a large number of pores on the surface.

The rutilization rates of the obtained primary fired particles and secondary fired particles were measured by XRD (RIR method) and found to be 31% and 95%, respectively. Moreover, the porosities of the primary fired particles and the secondary fired particles were 32% and 31%, respectively. The porosity (%) was determined by converting the pore volume (cm ³ /g) determined by BET specific surface area measurement in the range from 2.5 nm to 200 nm, assuming that the specific gravity of titanium dioxide is 4. Those results are shown in Table 1. Moreover, when the SEM image (5000 times) of the secondary fired particles was observed, it was confirmed that a large number of pores were formed on the surface as shown in FIG. The average particle size of the secondary fired particles was 6.5 μm. The average particle size was measured with a laser diffraction particle size distribution analyzer. The strength of the secondary fired particles was 250 MPa. Strength was measured by a compression test according to JIS R 1639-5. The strength was obtained by sandwiching the particles between two flat plates, breaking the particles by applying a load to the flat plates, and using the following calculation formula from the load at the time of breaking. The particle size d of the secondary fired particles used for strength calculation was the average value (d=(d1+d2)/2) of the major diameter d1 and the minor diameter d2 of the individual secondary fired particles whose strength was measured.
Cs=2.48×P/(πd ² )
(Cs: strength, P: breaking load, d: average particle diameter of minor and major diameters of measured particles)

[Experimental Examples 2 to 28]
For Experimental Examples 2 to 28, experiments were conducted in the same manner as in Experimental Example 1, except that the conditions of the primary firing process and the secondary firing process were set as shown in Table 1. The rutile ratio, porosity, average particle diameter and strength of the obtained primary and secondary fired particles were obtained in the same manner as in Experimental Example 1. Those results are shown in Table 1. In Experimental Examples 4, 8, 12, 16, 20, 24, and 28, secondary firing was not performed. Further, in Experimental Examples 25 to 28, the average particle size of the secondary fired particles was reduced by changing the formulation composition of Experimental Example 1. Specifically, in Experimental Examples 25 to 28, experiments were conducted in the same manner as in Experimental Example 1, except that polyethylene glycol having a molecular weight of 2000 (PEG2000, manufactured by Aldrich), which is a phase separation agent in the gelling step, was changed to 1.6 g. (However, the conditions of the primary firing process and the secondary firing process were set as shown in Table 1). As shown in Table 1, for Experimental Examples 1 to 3, 5 to 7, and 9 to 28, the average particle size was 0.8 μm to 6.5 μm, and the strength was 250 MPa to 290 MPa.

[Discussion]
As shown in Experimental Example 4 in Table 1, when the primary firing was performed at 800 ° C. for 2 hours, the rutile rate of the primary fired particles was as low as 31%, the porosity was 32%, and the average particle size was The diameter was 6.9 μm and the strength was 150 MPa, which was low. As shown in Experimental Examples 1 to 3, when the subsequent secondary firing was performed at 700 to 900° C. for 2 hours, the rutile rate of the secondary fired particles was as high as 95% or more, and the porosity was 22. The value was good at ~31%, the average particle size was 5.5 μm or more, and the strength was high at 250 MPa or more. In Experimental Example 4, in which the secondary firing was not performed, the rutilization rate was extremely low. This seems to be the cause.

As shown in Experimental Example 8 in Table 1, when the primary firing was performed at 900 ° C. for 2 hours, the rutile rate of the primary fired particles was as low as 66%, the porosity was 27%, and the average particle size was was 6.8 μm, and the strength was 210 MPa, which was low. As shown in Experimental Examples 5 to 7, when the subsequent secondary firing was performed at 700 to 900° C. for 2 hours, the rutile rate of the secondary fired particles was as high as 96% or more, and the porosity was 20%. The value was good at ~26%, the average particle size was 5.2 μm or more, and the strength was high at 250 MPa or more. In Experimental Example 8 in which the secondary firing was not performed, the rutilization rate was low. seems to be the cause.

As shown in Experimental Example 12 in Table 1, when the primary firing was performed at 950 ° C. for 2 hours, the primary fired particles had a high rutile rate of 95%, a porosity of 24%, and an average particle size of was 6.5 μm, and the strength was 250 MPa, which was high. As shown in Experimental Examples 9 to 11, when the subsequent secondary firing was performed at 700 to 900° C. for 2 hours, the rutile rate of the secondary fired particles was as high as 97% or more, and the porosity was 17. The value was good at ~23%, the average particle size was 4.0 μm or more, and the strength was high at 250 MPa or more.

As shown in Experimental Example 16 in Table 1, when the primary firing was performed at 1000 ° C. for 2 hours, the primary fired particles had a high rutile rate of 98%, a porosity of 23%, and an average particle size of was 5.8 μm, and the strength was 250 MPa, which was high. As shown in Experimental Examples 13 to 15, when the subsequent secondary firing was performed at 700 to 900° C. for 2 hours, the rutilization rate of the secondary fired particles was as high as 99% or more, and the porosity was 12. The value was good at ~22%, the average particle size was 3.4 μm or more, and the strength was high at 260 MPa or more.

As shown in Experimental Example 20 in Table 1, when the primary firing was performed at 1050 ° C. for 2 hours, the rutile rate of the primary fired particles was as high as 99%, the porosity was 18%, and the average particle size was was 4.6 μm, and the strength was 270 MPa, which was high. As shown in Experimental Examples 17 to 19, when the subsequent secondary firing was performed at 700 to 900° C. for 2 hours, the rutile rate of the secondary fired particles was as high as 99% or more, and the porosity was 10. The value was good at ~17%, the average particle size was 2.5 μm or more, and the strength was high at 260 MPa or more.

As shown in Experimental Example 24 in Table 1, when the primary firing was performed at 950 ° C. for 10 hours, the primary fired particles had a high rutile rate of 96%, a porosity of 25%, and an average particle size of was 5.5 μm, and the strength was 275 MPa, which was high. As shown in Experimental Examples 21 to 23, when the subsequent secondary firing was performed at 700 to 900° C. for 2 hours, the rutilization rate of the secondary fired particles was as high as 97% or more, and the porosity was 18. The value was good at ~24%, the average particle size was 3.7 μm or more, and the strength was high at 250 MPa or more.

As shown in Experimental Example 28 in Table 1, a formulation composition different from Experimental Examples 1 to 24 was adopted, and the primary firing was performed at 1000 ° C. for 2 hours. It had a high porosity of 96%, a porosity of 26%, an average particle size of 2.5 μm, and a strength of 270 MPa. As shown in Experimental Examples 25 to 27, when the subsequent secondary firing was performed at 700 to 900° C. for 2 hours, the rutilization rate of the secondary fired particles was as high as 96% or more, and the porosity was 15. The value was good at ~23%, the average particle size was 0.8 μm or more, and the strength was high at 265 MPa or more.

Aside from the experimental example described above, the hollow titanium oxide particles of Example 2 of Patent Document 4 were produced, and the strength was measured in the same manner as in the experimental example described above. Therefore, hollow titanium oxide particles may break during use. On the other hand, the sintered particles of Experimental Examples 1 to 3, 5 to 7, and 9 to 29 were not hollow, so it is considered that they had a high strength of 250 MPa or more.

Experimental Examples 1 to 3, 5 to 7, and 9 to 28 correspond to examples of the present invention, and Experimental Examples 4 and 8 correspond to comparative examples. It goes without saying that the embodiments described above do not limit the invention in any way.

INDUSTRIAL APPLICABILITY The present invention can be used, for example, in the fields of cosmetics, chromatography, etc., although it is not particularly limited.

Claims (2)

(a) contains soluble particles that dissolve in a predetermined liquid, a titanium (IV) alkoxide, a chelating agent, a phase separation agent, and an inorganic salt, and the amount of the chelating agent used is relative to the titanium (IV) alkoxide the molar ratio is 0.1 to 2.0, the amount of the phase separation agent used is 1 to 300% by weight relative to the titanium (IV) alkoxide, and the amount of the inorganic salt used is relative to the titanium (IV) alkoxide. a step of gelling the dispersion liquid in which the soluble particles are dispersed in a molar ratio of 0.005 to 0.5 with stirring;
(b) removing the chelating agent from the resulting gel;
(c) after removing the chelating agent, the gel is first baked at a baking temperature of 800° C. or higher and 1000° C. or lower, and then immersed in a predetermined liquid to dissolve the soluble particles in the predetermined liquid, a step of obtaining primary fired particles from which the soluble particles have been removed;
(d) obtaining porous rutile-type titania particles by secondarily firing the primary fired particles from which the soluble particles have been removed at a firing temperature of 700° C. or higher and 900° C. or lower;
including
the predetermined liquid is an alkaline solution,
The soluble particles are silica particles or silicate particles,
the chelating agent is a β-ketoester,
The phase separation agent is cellosolves or glycols,
The inorganic salt is a salt containing a conjugate base of a strong acid,
A method for producing porous rutile titania particles. The porous rutile titania particles have a large number of pores on the surface, an average particle size of 0.5 μm or more, a porosity of 10% or more, and a rutilization rate of 95% or more.
A method for producing the porous rutile titania particles according to claim 1 .

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