JP7416441B2 - Hydrotalcite compounds and photoactive catalysts - Google Patents

Description

The present invention relates to hydrotalcite compounds and photoactive catalysts.

Hydrotalcite compounds have conventionally been used for various purposes.

The hydrotalcite compound is a layered double hydroxide having an anion exchange function, for example, the general formula (1):
[M ₁ ²⁺ _1-x M ₂ ³⁺ _x (OH) ₂ ] [(A ^n- ) _x/n・mH ₂ O] (1)
[In the formula, M ₁ represents a divalent metal. _M2 represents a trivalent metal. Indicates 0<x<1. A ^n- represents an anion. n represents 1 or 2. m represents an integer of 1 or more. ]
Layered Double Hydrocxide (LDH)
Also called.

The above-mentioned hydrotalcite is also used as an ultraviolet absorber. For example, Patent Document 1 discloses a composite in which a compound that absorbs ultraviolet rays is incorporated between the layers of LDH, and a topical preparation containing the same. There is.

However, hydrotalcite is required to have performance that allows it to be used in a wider variety of applications. For example, hydrotalcite, which can absorb not only ultraviolet rays but also infrared rays, is useful as an additive in resin sheets used in disaster prevention tents, agricultural greenhouses, etc. that require heat retention.

In addition, when designing materials, there is a need for hydrotalcite that exhibits additional value in addition to ultraviolet and infrared absorption performance and can be used in a wide range of applications. As a result of extensive studies, the present inventors have found that hydrotalcite having a structure containing a specific metal and anion absorbs ultraviolet rays and infrared rays and exhibits photocatalytic activity. In addition to being used in disaster prevention tents, agricultural greenhouses, etc. that require heat retention, hydrotalcite can also be used as weather-resistant paints, paints, resin fillers, mouthguard fillers, etc. due to its photocatalytic activity. The present invention was achieved based on the discovery that the present invention can be used for various purposes.

Japanese Patent Application Publication No. 2002-167570

The present invention has been made in view of the above circumstances, and provides a hydrotalcite compound that absorbs ultraviolet and infrared rays and exhibits photocatalytic activity, and a photocatalytic activator containing the hydrotalcite compound. The purpose is to

As a result of extensive research to achieve the above object, the present inventors have discovered a hydrotalcite compound containing a specific metal and anion, and a photocatalytic activity containing a hydrotalcite compound containing a specific metal and anion. The inventors have discovered that the above object can be achieved by using the agent, and have completed the present invention.

That is, the present invention relates to the following hydrotalcite compound and photocatalyst activator.
1. General formula (1) below
[Zn _1-x Al _x (OH) ₂ ] [A ^n- _x/n・mH ₂ O] (1)
(In the formula, A ^n- represents an anion that is a carbonate ion, fluorine ion, or chloride ion. x is 0.2 to 0.4, n is the valence of the anion, and m is an integer of 1 or more .)
A photocatalyst activator containing a hydrotalcite compound represented by:
2. Item 2. The photocatalytic activator according to Item 1, wherein the A ^n- represents an anion that is a fluorine ion or a chlorine ion.
3. Item 3. The photocatalyst activator according to item 1 or 2, wherein x is 0.25 to 0.35.
4. General formula (2) below
[M ¹ _1-x M ² _x (OH) ₂ ] [A ^n- _x/n・mH ₂ O] (2)
(In the formula, M ¹ represents Zn or Cu, M ² represents Al or Fe, ^{A n-} represents an anion that is a carbonate ion, a fluorine ion, or a chloride ion. x is 0.2 to 0.4, and n is The valence of the anion, m indicates an integer of 1 or more .)
A photocatalyst activator containing a hydrotalcite compound represented by:
5. Item 5. The photocatalytic activator according to Item 4, wherein the A ^n- represents an anion that is a fluorine ion or a chlorine ion.
6. Item 5. The photocatalyst activator according to item 4 or 5, wherein x is 0.25 to 0.35.
7. Item 7. The photocatalyst activator according to any one of Items 4 to 6, wherein the content of the hydrotalcite compound is 90.0 to 99.9% by mass relative to 100% by mass of the photocatalyst activator.

The hydrotalcite compound of the present invention can absorb ultraviolet and infrared rays and exhibit photocatalytic activity. Moreover, the photocatalytic activator of the present invention can absorb ultraviolet rays and infrared rays and exhibit photocatalytic activity.

FIG. 2 is a diagram showing a synthesis flow of carbonate type Zn-Al (powder A (CO ₃ ^2- type)) LDH in Example 1. FIG. 3 is a diagram showing a synthesis flow of sulfuric acid type Zn-Al (powder B (SO ₄ ^2- type)) LDH in Comparative Example 1. 3 is a diagram showing a synthesis flow of nitric acid type Zn-Al (powder C(NO ₃ ^- type)) LDH in Comparative Example 2. FIG. FIG. 3 is a diagram showing the synthesis flow of chlorine-type Zn-Al (powder D(Cl ⁻ type)) LDH in Example 2. FIG. 3 is a diagram showing the synthesis flow of chlorine-type Zn-Al (powder E (Cl ⁻ type)) LDH in Example 3. FIG. 6 is a diagram showing the synthesis flow of fluorine-type Zn-Al (powder F (F ^- type)) in Example 4 and fluorine-type Zn-Al (powder G (F ^- type)) LDH in Example 5. 3 is a powder X-ray diffraction diagram of powder A (CO ₃ ^2- type) of Example 1. FIG. 2 is a powder X-ray diffraction diagram of powder B (SO ₄ ^2- type) of Comparative Example 1. FIG. 2 is a powder X-ray diffraction diagram of powder C (NO ₃ ⁻ type) of Comparative Example 2. FIG. FIG. 2 is an X-ray diffraction diagram of powder D (Cl − type) of Example 2 and powder E (Cl ⁻ type) of Example 3. FIG. 3 is a powder X-ray diffraction diagram of powder E (Cl ^- type) of Example 3, powder F (F ^- type) of Example 4, and powder G (F ^- type) of Example 5. Powder A of Example 1 (CO ₃ ^2- type), Powder B of Comparative Example 1 (SO ₄ ^2- type), Powder C of Comparative Example 2 (NO ₃ ^-type ), Powder E of Example 3 (Cl ^- FIG. 3 is a diagram showing the reflection spectra of powder G (F ^{− type) of Example 5 and powder G (F −} type) measured by ultraviolet-visible near-infrared spectroscopy. FIG. 2 is a diagram showing the decomposition activity index R [nmol/L/min] measured by irradiating ultraviolet light with a wavelength of 254 nm. FIG. 2 is a diagram showing the decomposition activity index R [nmol/L/min] measured by irradiating ultraviolet light with a wavelength of 365 nm.

As used herein, "containing" is a concept that encompasses all of "comprise," "consist essentially of," and "consist of." Furthermore, in this specification, when a numerical range is expressed as "A to B", it means greater than or equal to A and less than or equal to B.

1. Hydrotalcite compound The hydrotalcite compound of the present invention has the following general formula (1).
[Zn _1-x Al _x (OH) ₂ ] [A ^n- _x/n・mH ₂ O] (1)
(In the formula, A represents an anion that is a carbonate ion, fluorine ion, or chloride ion. x is 0.2 to 0.4, n is the valence of the anion, and m is an integer of 1 or more .)
It is a hydrotalcite compound represented by Since the hydrotalcite compound of the present invention contains zinc ions and aluminum ions as metal ions, and carbonate ions, fluoride ions, or chloride ions as anions, it is formed by a combination of these ions. , can absorb ultraviolet and infrared rays and also exhibit photocatalytic activity. Since the hydrotalcite compound of the present invention has the above-mentioned properties, it can be usefully used in various applications requiring the above-mentioned properties.

Hydrotalcite compounds cause intercalation due to anion exchange between layers. Anion exchange is a phenomenon in which, for example, by immersing a hydrotalcite compound in a solution containing anions, the hydrotalcite nanocompound releases its own anions and incorporates the anions in the solution into itself. Furthermore, anions can be eliminated by heat-treating the hydrotalcite compound.

The hydrotalcite compound of the present invention has _a host layer consisting of a positively charged octahedral layer represented by Zn _{1-x Al} It is preferable to have a hydrotalcite structure in which guest layers represented by ⁿ⁻ _x/n · m H ₂ O are alternately laminated.

In the above general formula (1), x is 0.2 to 0.4. When x is outside the above range, the ultraviolet and infrared absorption of the hydrotalcite compound decreases, and the photocatalytic activity is insufficient. The above x is preferably 0.25 to 0.35.

In the hydrotalcite compound of the present invention, the anion A ^n- of the guest layer is a carbonate ion (CO ₃ ^2- ), a fluorine ion (F ^- ), or a chloride ion (Cl ^- ). Among these, fluorine ions or chloride ions are preferred because the hydrotalcite compound of the present invention can better absorb ultraviolet rays and infrared rays and exhibit better photocatalytic activity.

In the anion (anion) A ^n- of the guest layer, n indicates the valence of the anion. n is preferably 1 or 2, and more preferably 1, since the hydrotalcite compound of the present invention can better absorb ultraviolet rays and infrared rays and exhibit better photocatalytic activity.

The above anions may be used alone or in combination of two or more.

In the hydrotalcite compound of the present invention, for example, when sodium carbonate is used as a precipitant, the carbonate ion CO ₃ ^2- can remain as the anion A ^n- . At this time, the hydrotalcite compound has the following general formula (1-2):
[Zn _1-x Al _x (OH) ₂ ] [(A ^n- ) _y・(CO ₃ ^2- ) _z・m H ₂ O] (1-2)
[In the formula, x represents a number from 0.2 to 0.4, and x=yn+2z. A ^n- represents an anion. n indicates the valence of the anion. m represents an integer of 1 or more (for example, an integer of 1 to 10). ]
The guest layer can have a composition expressed as (A ^n- ) _y ·(CO ₃ ^2- ) _z · m H ₂ O. At this time, when anions other than carbonate ions are not included, that is, when y is 0, the guest layer can be (CO ₃ ²⁻ ) _x/2 ·H ₂ O.

2. Photocatalyst activator (hydrotalcite compound)
The photocatalyst activator of the present invention has the following general formula (2):
[M ¹ _1-x M ² _x (OH) ₂ ] [A ^n- _x/n・mH ₂ O] (2)
(In the formula, M ¹ represents Zn or Cu, M ² represents Al or Fe, ^{A n-} represents an anion that is a carbonate ion, a fluorine ion, or a chloride ion. x is 0.2 to 0.4, and n is The valence of the anion, m indicates an integer of 1 or more .)
It is a photocatalyst activator containing a hydrotalcite compound represented by:

In the above general formula (2), M ¹ represents Zn or Cu. Among these, Zn is preferred because the photocatalytic activator of the present invention can better absorb ultraviolet rays and infrared rays and exhibit better photocatalytic activity.

For ^M1 , either Zn or Cu may be used alone, or a mixture of Zn and Cu may be used.

In the above general formula (2), M ² represents Al or Fe. Among these, Al is preferred because the photocatalytic activator of the present invention can better absorb ultraviolet rays and infrared rays and exhibit better photocatalytic activity.

For ^M2 , either Al or Fe may be used alone, or a mixture of Al and Fe may be used.

In the hydrotalcite compound contained in the photocatalyst activator of the present invention, x and n other than the above M ¹ and M ² are the same as x and n explained in the above hydrotalcite compound, and A ^n- is also the same as above. The same anions used in the hydrotalcite compound can be used.

The content of the hydrotalcite compound in the photocatalyst activator of the present invention is preferably as high as possible, but when the photocatalyst activator is 10% by mass, it is preferably 70.0% by mass or more, more preferably 80.0% by mass or more, and 90% by mass or more. It is more preferably .0% by mass or more, particularly preferably 99.9% by mass or more, and most preferably 100.0% by mass. When the lower limit of the content of the hydrotalcite compound is within the above range, the photocatalytic activator of the present invention can exhibit more excellent photocatalytic activity.

(Other additives)
The photocatalyst activator of the present invention may contain, in addition to the above-mentioned hydrotalcite compound, other additives commonly used for photocatalyst activators.

3. Method for producing hydrotalcite compound and photocatalyst activator The method for producing the hydrotalcite compound and photocatalyst activator of the present invention is not particularly limited, and examples include known LDH methods such as coprecipitation method and ion exchange method. It can be manufactured by the manufacturing method. When the anion is a carbonate ion or a chloride ion, it may be produced by a coprecipitation method, and when the anion is a fluorine ion, it may be produced by an ion exchange method.

As a coprecipitation method, for example, an aqueous solution containing an anion source is mixed with an aqueous solution containing metal salts of two metals so that the pH is maintained at 7.0 to 12, more preferably 8.5 to 10. , a method of gradually adding and reacting with a pH adjuster, and filtering, washing, drying and crushing the obtained product.

Examples of the ion exchange method include a method in which a powder of a hydrotalcite compound produced by the coprecipitation method described above is added to an aqueous sodium fluoride solution, and the resulting product is filtered, washed, dried, and crushed. Manufacturing raw materials, conditions, etc. may be appropriately selected and set depending on the desired hydrotalcite compound.

Examples of the metal salt used in the coprecipitation method include zinc nitrate, aluminum nitrate, zinc chloride, aluminum chloride, and the like. Hydrates of these metal salts may be used. In the coprecipitation method, metal salts of two types of metals may be appropriately selected and used from these metal salts, taking into consideration the metals forming the desired hydrotalcite compound and photocatalyst activator.

The above metal salts may be used alone or in combination of two or more.

Examples of the anion source used in the coprecipitation method include sodium hydrogen carbonate, sodium sulfate, sodium chloride, and sodium fluoride. In the above-mentioned coprecipitation method, an anion that forms the desired hydrotalcite compound and photocatalyst activator may be taken into consideration, and an anion source may be appropriately selected and used from these anion sources.

The above anion sources may be used alone or in combination of two or more.

The aqueous solution containing the metal salts of two types of metals and the aqueous solution containing the anion source are mixed and stirred to facilitate co-precipitation of the hydrotalcite compound and photocatalyst activator of the present invention. It is preferable to do so, and it is preferable to add a pH adjuster if necessary. Specific examples of the pH adjuster include bases such as sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, and lithium carbonate. These bases may be used alone or in combination of two or more. Furthermore, these bases may be in the form of an aqueous solution.

The amount of the pH adjuster used is not particularly limited, and the pH when mixing the aqueous solution containing the zinc salt and aluminum salt and the aqueous solution containing the surfactant is preferably 7.0 to 12 as described above. It is preferable to adjust as appropriate so that the ratio is maintained at 8.5 to 10.

In the above production method, the reaction temperature is not particularly limited, and may be set to a predetermined temperature for hydrothermal synthesis, for example, 20 to 60°C, particularly 30 to 50°C, if necessary.

Subsequently, the mixture is stirred while being maintained at the above-mentioned predetermined temperature to obtain the hydrotalcite compound and photocatalyst activator of the present invention. The stirring speed and time can be set as appropriate, but it is usually preferable to carry out the stirring at 500 to 1500 rpm for 6 to 48 hours.

Thereafter, if necessary, centrifugation, suction filtration, drying, etc. can be performed according to conventional methods to obtain the solid hydrotalcite compound and photocatalyst activator of the present invention. Thereafter, the particles can be adjusted to a predetermined particle size by classification, crushing, or the like. Further, it can be prepared in various forms, such as in the form of a slurry or in the form of granules by adding a binder or the like.

Hereinafter, the present invention will be explained in detail in the form of examples. The following examples do not limit the application of the present invention in any way.
Example 1: Synthesis of carbonate type Zn-Al (powder A (CO ₃ ^2- type)) LDH
Carbonate type Zn-Al LDH [Zn _1-x Al _x (OH) ₂ ][A ^n- _x/n・mH ₂ O] (A ^n- =CO ₃ ^2- , x=0.33) was prepared as follows by coprecipitation method. It was synthesized using the following procedure. The synthesis flow is shown in Figure 1. Specifically, 300 mL of ultrapure water and 5.0875 g (0.048 mol) of sodium carbonate (NA ₂ CO ₃ MW 105.99 Wako Pure Chemical Industries special grade) were added to a 500 mL beaker to prepare a 0.16 M aqueous sodium carbonate solution. Next, in a 300 mL beaker, add 100 mL of ultrapure water, 5.9494 g (0.02 mol) of zinc nitrate hexahydrate (Zn(NO ₃ ) ₂ 6H ₂ O MW297.47 Kishida Chemical Special Grade), and aluminum nitrate nonahydrate ( 3.7513 g (0.01 mol) of Al(NO ₃ ) ₃ ·6H ₂ O MW375.13 (Wako Pure Chemical Industries, Ltd. Special Grade) was added to prepare a nitrate mixed solution. Furthermore, 100 mL of ultrapure water and 8 g (0.2 mol) of sodium hydroxide (NaOH MW40 Kishida Chemical Special Grade) were added to another beaker to prepare a 2M aqueous sodium hydroxide solution.

Separately, use a hot stirrer (AS ONE REXIM RSH-1DN) and a stirrer to stir a 0.16M sodium carbonate aqueous solution at 1000 rpm at room temperature, and mix 100mL of a nitrate mixed solution and a 2M sodium hydroxide aqueous solution to keep the pH around 10.5. were added little by little using a Pasteur pipette. A pH meter (Horiba, Ltd. pH METER D-51) was used to measure pH. After each solution was added, the mixture was further stirred at room temperature for 24 hours at 1000 rpm to age. The aged solution was filtered by suction using a Buchner funnel (As One SU-60), filter paper (As One 60Φm/m No5-C), and an aspirator (EYELA Tokyo Rika Kikai A-3S). The residue was dried at 80°C for 18 hours in a programmed constant temperature dryer (Azu One DRYING OVEN DO-300PC), and the dried product was crushed in an agate mortar. As described above, powder A (CO ₃ ^2- type) was prepared.

Comparative example 1: Synthesis of sulfuric acid type Zn-Al (powder B (SO ₄ ^2- type)) LDH Sulfuric acid type Zn-Al LDH [Zn _1-x Al _x (OH) ₂ ][A ^n- _x/n・mH ₂ O] (A ^n- = SO ₄ ^2- , x=0.33) was synthesized by the coprecipitation method as follows. The synthesis flow is shown in Figure 2. Specifically, 300 mL of ultrapure water and 6.8179 g (0.048 mol) of sodium sulfate (Na ₂ SO ₄ MW 142.04 Kishida Kagaku 1st grade) were added to a 500 mL beaker to prepare a 0.16 M aqueous sodium sulfate solution. Next, 100 mL of ultrapure water, 5.9494 g (0.02 mol) of zinc nitrate hexahydrate, and 3.7513 g (0.01 mol) of aluminum nitrate nonahydrate were added to a 300 mL beaker to prepare a nitrate mixed solution. Furthermore, 100 mL of ultrapure water and 8 g (0.2 mol) of sodium hydroxide were added to another beaker to prepare a 2M aqueous sodium hydroxide solution.

Separately, use a hot stirrer and a stirrer to stir a 0.16M sodium sulfate aqueous solution at 60°C and 1000 rpm, and alternately add 100mL of a nitrate mixed solution and a 2M sodium hydroxide aqueous solution little by little to keep the pH around 10.5. added. This solution was stirred and aged at 60° C. and 1000 rpm for 24 hours. The residue after filtration was dried at 80°C for 18 hours, and the dried product was crushed in an agate mortar. As described above, powder B (SO ₄ ^2- type) was prepared.

Comparative Example 2: Synthesis of nitric acid type Zn-Al (powder C (NO ₃ ^- type)) LDH Nitric acid type Zn-Al LDH [Zn _1-x Al _x (OH) ₂ ][A ^n- _x/n・mH ₂ [O] (A ^n- = NO ₃ ^- , x=0.33) was synthesized by the coprecipitation method as follows. The synthesis flow is shown in Figure 3. Specifically, 200 mL of ultrapure water was placed in a 300 mL separable round flask with a four-necked separable cover, and stirred at 95° C. and 600 rpm using a hot stirrer, stirring bar, and oil bath. The four ports were a nitrogen inlet tube connected to a tube from a high-purity nitrogen cylinder using a pipette with a rubber stopper, a common sliding cooling tube with a calcium chloride tube attached, a sample input port, and a pH meter electrode insertion port. The sample input port and the pH electrode insertion port were covered with a common sliding stopper. Silicone grease (Shin-Etsu Chemical Co., Ltd., for high-temperature lubrication) was applied to the adhesive surfaces of the separable cover, flask, and glass stopper to make them adhere tightly. Next, high purity nitrogen gas (Neriki Gas, 99.999% or higher) was bubbled for 40 minutes. Next, 100 mL of ultrapure water, 5.9494 g (0.02 mol) of zinc nitrate hexahydrate, and 3.7513 g (0.01 mol) of aluminum nitrate nonahydrate were added to a 300 mL beaker to prepare a nitrate mixed solution. Furthermore, 100 mL of ultrapure water and 4 g (0.1 mol) of sodium hydroxide were added to another beaker to prepare a 1M aqueous sodium hydroxide solution. While bubbling was continued, the nitrate mixed solution and 1M sodium hydroxide solution were added little by little to adjust the pH to 9.34. After adjustment, the sample inlet and pH meter insertion port were each covered with a common sliding stopper and a silicone stopper. After 50 minutes, the nitrogen inlet and common sliding cooling pipe were replaced with a common sliding stopper. Stirring was continued for an additional 15 hours to ripen. The residue after filtration was dried at 80°C for 20 hours, and the dried product was crushed in an agate mortar. As described above, powder C (NO ₃ ⁻ type) was prepared.

Example 2: Synthesis of chlorine-type Zn-Al (powder D (Cl ^- type)) LDH Chlorine-type Zn-Al LDH [Zn _1-x Al _x (OH) ₂ ][A ^n- _x/n・mH ₂ O ] (A ^n- =Cl ^- , x=0.25) was synthesized by the coprecipitation method as follows. The synthesis flow is shown in Figure 4. Specifically, 300 mL of ultrapure water and 8.766 g (0.15 mol) of sodium chloride (NaCl MW58.44 Kishida Chemical Special Grade) were added to a 500 mL beaker to prepare a 0.5 M aqueous sodium chloride solution. Next, 100 mL of ultrapure water, 8.9241 g (0.03 mol) of zinc nitrate hexahydrate, and 3.7513 (0.01 mol) g of aluminum nitrate nonahydrate were added to a 300 mL beaker to prepare a nitrate mixed solution. Furthermore, 100 mL of ultrapure water and 8 g (0.2 mol) of sodium hydroxide (Kishida Chemical Special Grade, molecular weight 40) were added to another beaker to prepare a 2M aqueous sodium hydroxide solution.

Separately, use a hot stirrer and a stirrer to stir a 0.5M sodium chloride aqueous solution at 40°C and 1000 rpm, and add 100 mL of a nitrate mixed solution and a 2M sodium hydroxide aqueous solution little by little at a time to keep the pH around 10.0. Ta. This solution was stirred and aged at 40° C. and 1000 rpm for 24 hours. The residue after filtration was dried at 80°C for 18 hours, and the dried product was crushed in an agate mortar. As described above, powder D (Cl ^- type) was prepared.

Example 3: Synthesis of chlorine-type Zn-Al (powder E (Cl ^- type)) LDH Chlorine-type Zn-Al LDH [Zn _1-x Al _x (OH) ₂ ][A ^n- _x/n・mH ₂ O ] (A ^n- =Cl ^- , x=0.25) was synthesized by the coprecipitation method as follows. The synthesis flow is shown in Figure 5. Specifically, 300 mL of ultrapure water and 8.766 g (0.15 mol) of sodium chloride (NaCl MW58.44 Kishida Chemical Special Grade) were added to a 500 mL beaker to prepare a 0.5 M aqueous sodium chloride solution. Next, in a 300 mL beaker, add 100 mL of ultrapure water, 4.09 g (0.03 mol) of zinc chloride (ZnCl ₂ MW136.32, Wako Pure Chemical Industries, Ltd., special grade), and aluminum chloride hexahydrate (AlCl ₃ 6H2O MW241.43, Wako Pure Chemical Industries, Ltd.) 2.414 g (0.01 mol) of special grade) was added to prepare a chloride salt mixed solution. Furthermore, 100 mL of ultrapure water and 8 g (0.2 mol) of sodium hydroxide (Kishida Chemical Special Grade, molecular weight 40) were added to another beaker to prepare a 2M aqueous sodium hydroxide solution.

Separately, use a hot stirrer and a stirrer to stir a 0.5M sodium chloride aqueous solution at 40℃ at 1000 rpm, and alternately add 100mL of a chloride salt mixture solution and a 2M sodium hydroxide aqueous solution little by little to keep the pH around 10.0. added to. This solution was stirred and aged at 40° C. and 1000 rpm for 24 hours. The residue after filtration was dried at 80°C for 18 hours, and the dried product was crushed in an agate mortar. As described above, powder E (Cl ^- type) was prepared.

Example 4: Synthesis of fluorine-type Zn-Al (powder F (F ^- type) LDH) Fluorine-type Zn-Al LDH [Zn _1-x Al _x (OH) ₂ ][A ^n- _x/n・mH ₂ O] (A ^n- = F ^- , x=0.25) was synthesized using the ion exchange method using the following procedure. The synthesis flow diagram is shown in Figure 6. Specifically, in a 500 mL beaker, 300 mL of ultrapure water and 1.2595 g of sodium fluoride ( 0.03 mol) was added to prepare a 0.1M aqueous sodium fluoride solution.

Next, 1 g of powder E obtained in Example 3 was dropped into a 0.1M sodium fluoride solution. The pH of the 0.1M sodium fluoride solution was about 6.7, but by adding 1 g of powder E, the pH became about 7.6. Next, the mixture was stirred at room temperature at 500 rpm for 24 hours using a hot stirrer and a stirrer, and the residue after filtration was dried at 80° C. for 18 hours, and the dried product was crushed in an agate mortar. As described above, powder F (F ^- type) was prepared.

Example 5: Synthesis of fluorine-type Zn-Al (powder G (F ^- type)) LDH Fluorine-type Zn-Al LDH [Zn _1-x Al _x (OH) ₂ ][A ^n- _x/n・mH ₂ O ] (A ^n- = F ^- , x=0.25) was synthesized by the ion exchange method using the following procedure. The synthesis flow is shown in Figure 6. Specifically, 300 mL of ultrapure water and 1.2595 g (0.03 mol) of sodium fluoride were added to a 500 mL beaker to prepare a 0.1M aqueous sodium fluoride solution.

Next, 1 g of the powder E obtained in Example 3 was added to a 0.1 M aqueous sodium fluoride solution, and then a small amount of a 2 M aqueous sodium hydroxide solution was added dropwise, and the mixture was stirred at 20° C. and 500 rpm for 24 hours while keeping the pH at 10. The residue after filtration was dried at 80°C for 18 hours, and the dried product was crushed in an agate mortar. As described above, powder G (F ^- type) was prepared.

Test Example 1: Identification of crystalline phase by XRD The crystalline phase of the obtained product was identified by powder X-ray diffraction (XRD). The measurement was performed using an X-ray diffractometer (RINT2200, Rigaku Co., Ltd.) with a Co target as a monochromator, and the crystal phase was identified using analysis software (JADE6, Rigaku Co., Ltd.). The measurement conditions were: scan range 5 to 80 degrees, sampling width 0.02 degrees, scan speed 1.0 degrees/min, applied voltage 40 kV, applied current 20 mA, emission slit 1 degree, scattering slit 1 degree, light receiving slit 0.3 mm. And so.

FIG. 7 shows a powder X-ray diffraction diagram of powder A of Example 1. FIG. 7(a) shows the diffraction peak of powder A (CO ₃ ^2- type), and FIG. 7(b) shows the diffraction peak of zinc aluminum carbonate hydroxide hydrate (ICDD#48-1025). Comparing (a) and (b), the diffraction angle and intensity of the peaks are almost the same, and it is considered that a single phase of zinc aluminum carbonate hydroxide hydrate was obtained. Moreover, the peak is relatively sharp, and the crystallinity is considered to be relatively high.

FIG. 8 shows a powder X-ray diffraction diagram of Powder B of Comparative Example 1. FIG. 8(a) shows the diffraction peak of powder B (SO ₄ ^2- type). For comparison, FIG. 8(b) shows the diffraction peak of powder A (CO ₃ ^2- type), and FIG. 8(c) shows the diffraction peak of zinc aluminum carbonate hydroxide hydrate (ICDD#48-1025). Comparing the diffraction peak of (a) Powder B (SO ₄ ^2- type) and (b) the diffraction peak of A (CO ₃ ^2- type), the diffraction peak of (a) Powder B (SO ₄ ^2- type) There is a peak between (003) and (006), suggesting the possibility of a by-product. In addition, the strongest peak (003) has been significantly shifted to a lower angle, making it slightly asymmetrical. In addition, the interplanar spacing d ₀₀₃ = 11.1 [Å], which is larger than the diffraction peak of powder A (CO ₃ ^2- type). The sizes of the sulfate roots (SO ₄ ^2- ) and carbonate roots (CO ₃ ^2- type) suggest that the interlayer carbonate roots may be replaced by sulfate roots.

FIG. 9 shows a powder X-ray diffraction diagram of powder C (NO ₃ ⁻ type) of Comparative Example 2. The diffraction peak of powder C (NO ₃ ^- type) of Comparative Example 2 in Figure 9 is somewhat similar to the diffraction peak of powder A (CO ₃ ^2- type) in Figure 7(a), but the peak is broad. This suggests variations in the periodic structure. Also, although it is asymmetrical, if the strongest peak is the (003) plane, the interplanar spacing d ₀₀₃ =8.806 [Å], which is larger than the d ₀₀₃ of powder A (CO ₃ ^2- type), and the carbonate radical (CO ₃ ^2- type) and the size of nitrate roots (NO ^3- ) suggest that the interlayers are partially replaced by nitrate roots.

FIG. 10 shows powder X-ray diffraction patterns of powder B of Example 2 and powder E of Example 3. FIG. 10(a) shows the diffraction peak of powder D (Cl ^- type), and FIG. 10(b) shows the diffraction peak of powder E (Cl ^- type). Further, for comparison, the diffraction peak of ZnO is shown in FIG. 10(c). From FIG. 10(a), a small peak is seen around 35° for powder D, but it does not match ZnO and is thought to be unwashed chloride. The angle of the strongest peak was 13.08°.

FIG. 11 shows powder X-ray diffraction patterns of powder E (Cl ⁻ type) of Example 3, powder F (F ⁻ type) of Example 4, and powder G (F ⁻ type) of Example 5. Figure 11(a) shows the diffraction peak of powder E (Cl ^- type), Figure 11(b) shows the diffraction peak of powder F (F ^- type), and Figure 11(c) shows the diffraction peak of powder G (F ^- type) of powder X. This is a line diffraction peak.

From the above, the interplanar spacing of each sample determined from the strongest peak position of (003) under Bragg's diffraction conditions is shown in Table 1 below. The (003) lattice spacing is proportional to the distance between the layers, and the fact that the lattice spacing changes depending on the introduced anion suggests that at least a portion of the lattice has been replaced.

Test Example 2: Measurement of reflection spectrum by ultraviolet-visible-near infrared absorption spectroscopy The reflection spectrum of the obtained product was measured by ultraviolet-visible-near infrared absorption spectroscopy (UV-Vis-NIR). It was measured. Ultraviolet-visible-near-infrared spectroscopy is a method of determining the absorbance and transmittance of a sample by irradiating the sample with light separated by wavelength and measuring the intensity of the light reflected and transmitted by the sample. Absorbance measurement allows qualitative and quantitative analysis of target components in a sample and evaluation of the wavelength characteristics of the sample. Furthermore, transmittance measurement allows evaluation of transmittance characteristics specific to components in a sample.

Specifically, the reflection spectrum was measured using an ultraviolet-visible near-infrared spectrophotometer (Shimadzu SolidSpec-3700). After measuring the background using a standard white plate Spectralon, the sample was filled in a sample holder and measured. The measurement conditions were a measurement range of 240 nm to 2500 nm, a high scanning speed, and a sampling pitch of 1.0.

FIG. 12 shows powder A of Example 1 (CO ₃ ^2- type), powder B of Comparative Example 1 (SO ₄ ^2- type), powder C of Comparative Example 2 (NO ₃ ^-type ), and powder of Example 3. The reflection spectra of powder E (Cl ^- type) and powder G (F ^- type) of Example 5 measured by ultraviolet-visible-near-infrared spectroscopy are shown.

From the results shown in Figure 12, absorption was confirmed in the near-infrared region of around 1450 nm and 1930 nm in all powders, but it was observed that absorption was observed in the near ^-infrared region of _{1450 nm} and 1930 nm. ₃ ^- type), powder E of Example 3 (Cl ^- type), and powder G of Example 5 (F ^- type) were found to exhibit absorption even in the ultraviolet region (near 300 nm). In particular, powder E (Cl ^- type) of Example 3 and powder G (F ^- type) of Example 5 were found to exhibit excellent absorption in the ultraviolet region (near 300 nm).

Test Example 3: Wet decomposition performance test In order to evaluate the photocatalytic activity of the powder, a wet decomposition performance test was conducted. The measurement method referred to JIS R 1703-2.

Specifically, dissolve 0.0075 g (0.02 mmol) of methylene blue powder (C ₁₆ H ₁₈ ClN ₃ S・3H ₂ O MW373.90 Kishida Chemical Special Grade) in 1 L of ultrapure water, and add 0.02 mmol/L methylene blue test solution. Prepared. 30 mL of the methylene blue test solution was accurately weighed using a 10 mL measuring cylinder, placed in a glass petri dish, and 0.1 g of the synthesized LDH powder was immersed therein to prepare a test sample. Using an ultraviolet lamp (As One Handy UV Lamp SLUV-6 9W), ultraviolet light with a wavelength of 254 nm or 365 nm was irradiated for 20 minutes. Immediately after irradiation, the methylene blue test solution was sucked up with a pipette and collected into a standard quartz cell (As One CUVENT 10 mm), and the absorption spectrum of the test solution was measured using a UV-visible photometer (JASCO Model V-550). The measurement conditions were as shown in Table 2 below.

After measuring the absorption spectrum, the liquid used for the measurement was immediately returned to the Petri dish and irradiated with ultraviolet light for 20 minutes again. This procedure was repeated nine times until the total irradiation time was 3 h.

Since absorbance is generally proportional to concentration (Beer's law), concentration was calculated from absorbance using a conversion factor. First, the conversion coefficient K was calculated from the following formula (1) using the absorbance Abs(0).

Next, the absorbance Abs(t) was converted to the methylene blue test solution concentration C(t) [μM] after t [min] using the conversion factor K and the following formula (2).

The vertical axis shows the concentration C(t) [μM], and the horizontal axis shows the ultraviolet irradiation time t [min], and each powder has 9 data points (t=20, 40, 60, 80, 100, 120, 140, 160 , 180) were plotted. The plotted points for each test piece were linearly approximated using the least squares method, and 1/1000 of the absolute value of the slope was determined to be the decomposition activity index R [nmol/L/min].

FIG. 13 shows the decomposition activity index R [nmol/L/min] measured by irradiating ultraviolet light with a wavelength of 254 nm. In FIG. 13, the LDH powders are Powder A of Example 1 (CO ₃ ^2- type), Powder B of Comparative Example 1 (SO ₄ ^2- type), Powder C of Comparative Example 2 (NO 3 -type), and Powder C of Comparative Example 2 (NO ₃ ^-type ). Powder E (Cl ^- type) from Example 3 and powder G (F ^- type) from Example 5 were used. From the results in Figure 13, when irradiated with short wavelength ultraviolet light of 254 nm, the decomposition activity index, which is an index of photocatalytic activity, becomes large for carbonate type, chlorine type, and fluorine type, exceeding 5, which is a guideline for photocatalytic activity. It was found that it shows value. In particular, it was found that the chlorine type and fluorine type exhibited values significantly exceeding 5, which is the standard for catalytic activity.

FIG. 14 shows the decomposition activity index R [nmol/L/min] measured by irradiating ultraviolet light with a wavelength of 365 nm. In FIG. 14, the LDH powders are Powder A of Example 1 (CO ₃ ^2- type), Powder B of Comparative Example 1 (SO ₄ ^2- type), Powder C of Comparative Example 2 (NO 3 -type), and Powder C of Comparative Example 2 (NO ₃ ^-type ). Powder E (Cl ^- type) from Example 3 and powder G (F ^- type) from Example 5 were used. From the results in Figure 14, it can be seen that even when irradiated with 365 nm ultraviolet rays, the decomposition activity index, which is an index of photocatalytic activity, is large for carbonate type, chlorine type, and fluorine type, as when irradiated with short wavelength ultraviolet rays of 254 nm. It was found that the value exceeds 5, which is a standard for photocatalytic activity. In particular, it was found that the chlorine type and fluorine type exhibited values significantly exceeding 5, which is the standard for catalytic activity.

Claims (5)

General formula (1) below
[Zn _1-x Al _x (OH) ₂ ] [A ^n- _x/n・mH ₂ O] (1)
(In the formula, A ^n- represents an anion that is a fluorine ion or a chlorine ion. x is 0.2 to 0.4, n is the valence of the anion, and m is an integer of 1 or more .)
A photocatalyst activator containing a hydrotalcite compound represented by: The photocatalyst activator according to claim 1 , wherein the x is 0.25 to 0.35. General formula (2) below
[M ¹ _1-x M ² _x (OH) ₂ ] [A ^n- _x/n・mH ₂ O] (2)
(In the formula, M ¹ represents Zn or Cu, M ² represents Al or Fe, ^{A n-} represents an anion that is a fluorine ion or a chlorine ion, x is 0.2 to 0.4, and n is an anion. valence, m indicates an integer greater than or equal to 1. )
A photocatalyst activator containing a hydrotalcite compound represented by: The photocatalyst activator according to claim 3 , wherein the x is 0.25 to 0.35. The photocatalyst activator according to claim 3 or 4 , wherein the content of the hydrotalcite compound is 90.0 to 99.9% by mass relative to 100% by mass of the photocatalyst activator.

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