Method for producing am-4 type titanosilicate using layered silicate compound as raw material

Abstract

To provide a method for producing an AM-4 type titanosilicate by which the AM-4 type titanosilicate can be produced without requiring a previous preparation process of a silica source solution and a titanium source solution carried out in a conventional production method.SOLUTION: The method for producing the AM-4 type titanosilicate comprises mixing a layered alkali metal silicate, a titanium compound, an alkali metal hydroxide and water to prepare a raw material mixture, and subjecting the raw material mixture to hydrothermal synthesis at a temperature of ≥ 210 °C to obtain the AM-4 type titanosilicate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing an AM-4 type titanosilicate using a layered silicate compound as a raw material. [Background technology]

[0002] In recent years, various types of titanosilicates, such as TS-1, ETS-4, and AM-4, have attracted attention as catalysts for the oxidation of organic compounds or as molecular sieves for separating specific substances from mixtures.

[0003] Non-Patent Documents 1 to 7 describe AM-4 type titanosilicate. AM-4 type titanosilicate is typically represented by the chemical formula Na3(Na,H)Ti2O2(SiO2O6)2·2H2O, and is produced by preparing a basic silica source solution (e.g., a mixture containing silica, sodium hydroxide, and deionized water) and an acidic titanium source solution (e.g., a mixture containing titanium chloride, hydrochloric acid, and deionized water), mixing these solutions, and then subjecting this raw material mixture to hydrothermal synthesis (e.g., Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] MSDadachov,et al.,Chem.Commun.,1997,2371-2372 [Non-patent document 2] Zhi Lin,et al.,J.Phys.Chem.B,1997,101,7114-7120 [Non-patent document 3] CBLopes,et al.,Microporous and Mesoporous Materials,2007,103,325-332 [Non-patent document 4] Clara Casado,et al.,Eur.J.Inorg.Chem.,2011,14,2247-2253 [Non-Patent Document 5] Javier Perez-Carvajal,et al.,Applied Clay Science,2012,56,30-35 [Non-patent document 6] Maria N. Timofeeva,et al.,Applied Catalysis A, General,2019,587,117240 [Non-Patent Document 7] Maria N. Timofeeva,et al.,Applied Clay Science,2020,186,105445 Summary of the Invention [Problem to be solved by the invention]

[0005] As described in Non-Patent Document 1, conventional methods for producing AM-4 type titanosilicate require steps of preparing a silica source solution and a titanium source solution of appropriate concentrations before preparing a raw material mixture to be subjected to hydrothermal synthesis.

[0006] However, the steps of preparing the silica source solution and the titanium source solution in advance are complicated, and from the viewpoint of industrial production, the number of steps increases, which is likely to lead to an increase in costs.

[0007] Therefore, it is preferable to be able to produce AM-4 type titanosilicate without requiring a step of preparing a silica source solution and a titanium source solution in advance.

[0008] The present invention has been made in view of the above problems, and has as its object to provide a method for producing AM-4 type titanosilicate that does not require the prior preparation of a silica source solution and a titanium source solution. [Means for solving the problem]

[0009] The above-mentioned problem was solved by carrying out hydrothermal synthesis under predetermined conditions on a raw material mixture obtained by mixing a layered alkali metal silicate, a titanium compound, an alkali metal hydroxide, and water. Specifically, the following means were used. <1> Preferably, <2> The above problem was solved by the following means. [1] A method for producing AM-4 type titanosilicate, comprising: mixing a layered alkali metal silicate, a titanium compound, an alkali metal hydroxide, and water to prepare a raw material mixture; and subjecting the raw material mixture to hydrothermal synthesis at a temperature of 210°C or higher to obtain AM-4 type titanosilicate. [2] The method according to [1], wherein the temperature of the hydrothermal synthesis is 220°C or higher. [3] The method according to [1] or [2], wherein the hydrothermal synthesis time is 75 hours or more. [4] When the temperature of the hydrothermal synthesis is 210°C or more and less than 220°C, the time of the hydrothermal synthesis is 192 hours or more; When the temperature of the hydrothermal synthesis is 220°C or more and less than 230°C, the time of the hydrothermal synthesis is 144 hours or more; When the temperature of the hydrothermal synthesis is 230°C or more and less than 240°C, the time of the hydrothermal synthesis is 96 hours or more; When the temperature of the hydrothermal synthesis is 240°C or more and less than 260°C, the time of the hydrothermal synthesis is 72 hours or more; When the temperature of the hydrothermal synthesis is 260°C or more, the time of the hydrothermal synthesis is 23 hours or more; The method for producing a semiconductor device according to any one of [1] to [3]. [5] The method according to any one of [1] to [4], wherein the layered alkali metal silicate includes at least one of kanemite, makatite, illaite, magadiite, and kenyaite. [6] The method according to any one of [1] to [5], wherein the titanium compound is at least one of titanium oxide, titanium halide, and organic titanium compound. [7] The method according to any one of [1] to [6], wherein the alkali metal hydroxide is at least one of sodium hydroxide and potassium hydroxide. [8] The method according to any one of [1] to [7], wherein the temperature of the hydrothermal synthesis is 350° C. or less. [9] The method according to any one of [1] to [8], wherein the pH of the raw material mixture is 12.0 or higher. [Effects of the Invention]

[0010] According to the production method of the present invention, it is possible to produce AM-4 type titanosilicate without the need for a step of preparing a silica source solution and a titanium source solution in advance. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 shows the XRD patterns of Examples 1 to 4 and Comparative Example 1. [Figure 2] FIG. 2 shows the XRD patterns of Example 5 and Comparative Examples 2 to 4. [Figure 3] FIG. 3 shows the XRD patterns of Example 6 and Comparative Examples 5 to 7. [Figure 4] FIG. 4 shows the XRD patterns of Examples 7 to 9. [Figure 5] FIG. 5 shows the XRD patterns of Examples 10 to 12. [Figure 6] FIG. 6 shows the XRD patterns of Examples 13 to 15 and Comparative Example 8. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention is a method for producing AM-4 type titanosilicate, which comprises mixing a layered alkali metal silicate, a titanium compound, an alkali metal hydroxide, and water to prepare a raw material mixture, and subjecting the raw material mixture to hydrothermal synthesis at a temperature of 210°C or higher for 72 hours or more to obtain AM-4 type titanosilicate. In the present invention, the reaction mechanism of the raw materials is not clear, but as will be described in detail later, it is thought that during the hydrothermal synthesis, ion exchange occurs between the alkali metal ions in the layered alkali metal silicate and the titanium ions dissolved in the solvent, and the silicate, affected by the ion exchange and thermal energy, undergoes a phase change to AM-4 type titanosilicate.

[0013] The production method of the present invention includes preparing a raw material mixture by mixing a layered alkali metal silicate, a titanium compound, an alkali metal hydroxide, and water. The layered alkali metal silicate and the titanium compound serve as a silica source and a titanium source, respectively, in the production of titanosilicate. Thus, in the production method of the present invention, a silica source solution in which a silica source is dissolved and a titanium source solution in which a titanium source is dissolved are not separately prepared, but the prepared layered alkali metal silicate and the titanium compound are directly mixed with the same solvent (water).

[0014] The method for mixing the layered alkali metal silicate, titanium compound, alkali metal hydroxide, and water is not particularly limited. The mixing may be carried out by a method of adding the layered alkali metal silicate and titanium compound to an aqueous solution of alkali metal hydroxide, by a method of adding an aqueous solution of alkali metal hydroxide to the layered alkali metal silicate and titanium compound, or by a method of adding the layered alkali metal silicate, titanium compound, and alkali metal hydroxide in that order to water.

[0015] The layered alkali metal silicate is a silicate containing an alkali metal and having a layered structure, and is a compound that has cleavage properties and is thin and easily peeled off. The type of layered alkali metal silicate is not particularly limited, and the layered alkali metal silicate may be a natural mineral or a synthetic product.

[0016] Examples of alkali metals contained in the layered alkali metal silicate include lithium, sodium, and potassium. The alkali metal preferably contains at least one of sodium and potassium, and more preferably sodium. The total content of sodium and potassium in the alkali metal is preferably 50 atomic % or more, more preferably 75 atomic % or more, and even more preferably 90 atomic % or more, based on the total number of alkali metal atoms. The total content of sodium and potassium in the alkali metal can be 100 atomic % or less, or even 95 atomic % or less. In particular, the alkali metal is preferably at least one of sodium and potassium, and more preferably sodium.

[0017] The layered alkali metal silicate may contain, in addition to alkali metals, metal ions other than alkali metals, such as alkaline earth metals (e.g., magnesium, calcium, and strontium), aluminum, and zinc. From the viewpoint of reducing impurities in the titanosilicate, the content of metal ions other than alkali metals in the layered alkali metal silicate is preferably 10 atomic % or less, more preferably 5 atomic % or less, and even more preferably 1 atomic % or less, based on the total number of metal ions. In particular, it is preferable that the layered alkali metal silicate does not contain metal ions other than alkali metals.

[0018] In the manufacturing method of the present invention, a layered alkali metal silicate containing sodium is preferably used. Examples of such silicates include kanemite, makatite, illaite, magadiite, and Kenyaite. The layered alkali metal silicate preferably contains at least one of kanemite, makatite, illaite, magadiite, and Kenyaite, and more preferably at least one of magadiite and Kenyaite. The total amount of magadiite and Kenyaite in the layered alkali metal silicate is preferably 50% by mass or more, more preferably 75% by mass or more, and even more preferably 90% by mass or more, based on the total mass of the layered alkali metal silicate. The total amount of magadiite and Kenyaite in the layered alkali metal silicate can be 100% by mass or less, or even 95% by mass or less, based on the total mass of the layered alkali metal silicate. In particular, the layered alkali metal silicate preferably comprises at least one of magadiite and kenyaite.

[0019] The typical chemical formula of magadiite is Na2Si 14 O 29 nH2O, and the typical chemical formula of Kenyaite is Na2Si 22 O 45 nH2O. In the above chemical formula, n is a number between 1 and 20, more commonly between 5 and 15. These compounds may have a structure in which a hydrogen atom is substituted for one Na atom (the "Na2" part is represented by "NaH") or a structure in which an additional hydrogen atom is added to two Na atoms (the "Na2" part is represented by "Na2H"). The synthesis method for magadiite and kenyaite is not particularly limited and is described, for example, in Kosuge Katsunori et al., "Hydrothermal Synthesis of Magadiite and Kenyaite," Journal of the Ceramic Society of Japan, Vol. 100(3), pp. 326-331 (1992).

[0020] It is also possible to use silica materials other than layered alkali metal silicates (e.g., commercially available silica particles, aluminosilicates) as the silica source. However, it is preferable that the silica source contains layered alkali metal silicates as the main component. The content of the layered alkali metal silicate in the silica source is preferably 50% by mass or more, more preferably 75% by mass or more, and even more preferably 90% by mass or more, based on the total mass of the silica source. The content of the layered alkali metal silicate in the silica source can be 100% by mass or less, or may be 95% by mass or less, based on the total mass of the silica source. It is preferable that the silica source consists of layered alkali metal silicates.

[0021] The titanium compound is not particularly limited as long as it is a compound that can be dissolved in water or an aqueous solution of an alkali metal hydroxide. The titanium compound can be a titanium compound that can be generally used in the production method of titanosilicate. The titanium compound can be in powder, granular, or liquid form. Examples of titanium compounds that can be preferably used in the production method of the present invention include titanium dioxide (titania), organic titanium compounds (e.g., titanium alkoxides containing an alkoxy group having 1 to 4 carbon atoms), and titanium halides (e.g., titanium chloride, titanium bromide, titanium iodide). From the viewpoint of reducing impurities in the titanosilicate, the titanium compound is more preferably titanium dioxide.

[0022] The amounts and blending ratios of the layered alkali metal silicate and the titanium compound are adjusted in advance according to the target production amount of the resulting titanosilicate. The amount of the layered alkali metal silicate is preferably 3 to 50 parts by mass, more preferably 5 to 40 parts by mass, and even more preferably 7 to 30 parts by mass, per part by mass of the titanium compound. The mass ratio Si / Ti of the Si atoms in the layered alkali metal silicate to the Ti atoms in the titanium compound is preferably 5 to 20, more preferably 6 to 15. In particular, when the layered alkali metal silicate is magadiite and the titanium compound is titanium dioxide, the mass ratio of magadiite / titanium dioxide is preferably 5 to 30, more preferably 11 to 27. When the layered alkali metal silicate is kenyaite and the titanium compound is titanium dioxide, the mass ratio of kenyaite / titanium dioxide is preferably 5 to 30, more preferably 10 to 25.

[0023] The alkali metal hydroxide is not particularly limited, but is preferably at least one of sodium hydroxide and potassium hydroxide. From the viewpoint of reducing impurities in the titanosilicate, the alkali metal hydroxide is more preferably sodium hydroxide. The water is not particularly limited, but is preferably distilled water or deionized water.

[0024] The amounts of alkali metal hydroxide and water are preferably adjusted so that when they are mixed to prepare an aqueous solution of alkali metal hydroxide, the concentration is 0.5 to 2.0 M. The amount of water is preferably 300 mL to 1.5 L, and more preferably 400 mL to 1.0 L, per 10 g of layered alkali metal silicate. As the alkali metal hydroxide and water, commercially available aqueous solutions of alkali metal hydroxides can also be used.

[0025] The pH of the raw material mixture after preparation, i.e., before hydrothermal synthesis, is preferably strongly alkaline (greater than pH 11). When the pH of the raw material mixture is strongly alkaline, the layered alkali metal silicate and titanium compound are easily dissolved in the solvent. From the viewpoint of increasing the solubility of the materials, the pH of the raw material mixture is preferably 12.0 or higher, more preferably 12.5 or higher, and even more preferably 12.7 or higher. The pH of the raw material mixture is, for example, 13.5 or lower, and may be 13.3 or lower.

[0026] The production method of the present invention involves obtaining AM-4 type titanosilicate by subjecting a raw material mixture to hydrothermal synthesis at a temperature of 210° C. or higher. A pressure-resistant apparatus such as an autoclave is used for the hydrothermal synthesis.

[0027] The hydrothermal synthesis temperature is 210°C or higher. In the hydrothermal synthesis of the present invention, ion exchange occurs between the alkali metal ions in the layered alkali metal silicate and the titanium ions dissolved in the solvent. The silicate, affected by the ion exchange and thermal energy, undergoes a phase change to a silica-rich titanosilicate of another phase type, such as ETS-4 titanosilicate (approximately Si:Ti=12:5). It is believed that subsequent phase change to AM-4 titanosilicate (approximately Si:Ti=2:1) ​​with a relatively low silica concentration occurs due to a further increase in titanium ions or silica elution. A temperature of 210°C or higher can induce this phase change. To promote this phase change, the hydrothermal synthesis temperature is preferably 220°C or higher, more preferably 230°C or higher, even more preferably 235°C or higher, and may be 240°C or higher. If the temperature of the hydrothermal synthesis is too high, pressure-resistant equipment may not be able to withstand it, and in addition, the layer structure of the layered alkali metal silicate may be completely destroyed, which may prevent the benefits of using the layered alkali metal silicate as a silica source. Therefore, the temperature of the hydrothermal synthesis is preferably 350°C or less, more preferably 300°C or less, and even more preferably 270°C or less.

[0028] The hydrothermal synthesis time (the time for which the raw material mixture is subjected to hydrothermal synthesis) can be adjusted appropriately depending on the hydrothermal synthesis temperature so that AM-4 titanosilicate is obtained. As mentioned above, it is believed that silicates affected by ion exchange and thermal energy undergo a phase change to AM-4 titanosilicate via other phase types of titanosilicate (e.g., ETS-4), and it takes a relatively long time for AM-4 titanosilicate to be produced. It is important to perform the hydrothermal synthesis for a sufficient time until AM-4 titanosilicate is obtained. In addition, the longer the hydrothermal synthesis time, the more likely it is that a single-phase compound of AM-4 titanosilicate will be obtained. The time for hydrothermal synthesis can be set to, for example, 20 hours or more, 30 hours or more, 40 hours or more, 50 hours or more, 60 hours or more, 70 hours or more, 75 hours or more, 80 hours or more, 90 hours or more, 100 hours or more, 110 hours or more, 120 hours or more, 130 hours or more, 140 hours or more, 150 hours or more, 160 hours or more, 170 hours or more, 180 hours or more, 190 hours or more, or 200 hours or more, depending on the hydrothermal synthesis temperature. The upper limit of the time for hydrothermal synthesis is not particularly limited, and may be, for example, 350 hours or less, 300 hours or less, or 270 hours or less.

[0029] The higher the set temperature for hydrothermal synthesis (above 210°C), the shorter the time until AM-4 titanosilicate begins to form and the time until a single-phase AM-4 titanosilicate compound is obtained. Therefore, the higher the set temperature, the shorter the hydrothermal synthesis time can be. However, the time until AM-4 titanosilicate begins to form and the time until a single-phase AM-4 titanosilicate compound is obtained may vary depending on synthesis conditions other than temperature (such as the type and composition of raw materials) and the condition of the container (such as heat transfer efficiency and the presence or absence of scratches on the container inner wall). It is important to set the hydrothermal synthesis time within a range that will allow AM-4 titanosilicate to be obtained, depending on the specific circumstances.

[0030] When the hydrothermal synthesis temperature is 210°C or higher but lower than 220°C, the hydrothermal synthesis time is preferably 192 hours or longer. A hydrothermal synthesis time of 192 hours or longer facilitates the production of AM-4 type titanosilicate in this temperature range. The longer the hydrothermal synthesis time, the greater the proportion of AM-4 type titanosilicate produced, making it easier to obtain a single-phase compound of AM-4 type titanosilicate. Therefore, in this temperature range, the hydrothermal synthesis time is more preferably 200 hours or longer.

[0031] When the hydrothermal synthesis temperature is 220°C or higher but lower than 230°C, the hydrothermal synthesis time is preferably 144 hours or longer. A hydrothermal synthesis time of 144 hours or longer facilitates the production of AM-4 type titanosilicate in this temperature range. The longer the hydrothermal synthesis time, the greater the production rate of AM-4 type titanosilicate, making it easier to obtain a single-phase compound of AM-4 type titanosilicate. Therefore, in this temperature range, the hydrothermal synthesis time is more preferably 150 hours or longer.

[0032] When the hydrothermal synthesis temperature is 230°C or higher but lower than 240°C, the hydrothermal synthesis time is preferably 96 hours or longer. A hydrothermal synthesis time of 96 hours or longer facilitates the production of AM-4 type titanosilicate in this temperature range. The longer the hydrothermal synthesis time, the greater the production rate of AM-4 type titanosilicate, making it easier to obtain a single-phase compound of AM-4 type titanosilicate. Therefore, in this temperature range, the hydrothermal synthesis time is more preferably 120 hours or longer.

[0033] When the temperature of the hydrothermal synthesis is 240°C or higher but lower than 260°C, the hydrothermal synthesis time is preferably 72 hours or longer. A hydrothermal synthesis time of 72 hours or longer facilitates the production of AM-4 type titanosilicate in this temperature range. The longer the hydrothermal synthesis time, the greater the production rate of AM-4 type titanosilicate, making it easier to obtain a single-phase compound of AM-4 type titanosilicate. Therefore, in this temperature range, the hydrothermal synthesis time is more preferably 96 hours or longer.

[0034] When the hydrothermal synthesis temperature is 260°C or higher, the hydrothermal synthesis time is preferably 23 hours or longer. A hydrothermal synthesis time of 23 hours or longer makes it easier to produce AM-4 type titanosilicate in this temperature range. The longer the hydrothermal synthesis time, the greater the production rate of AM-4 type titanosilicate, making it easier to obtain a single-phase compound of AM-4 type titanosilicate. Therefore, in this temperature range, the hydrothermal synthesis time is more preferably 30 hours or longer.

[0035] When a general pressure-resistant apparatus is used, the pressure for the hydrothermal synthesis is generally 10 to 20 atmospheres, but is not limited to this.

[0036] In the AM-4 type titanosilicate obtained by the production method of the present invention, the atomic ratio of Si atoms to Ti atoms, Si / Ti, is preferably 2-10, more preferably 2-5, and even more preferably 2-4.

[0037] In the AM-4 type titanosilicate obtained by the production method of the present invention, the atomic ratio M / Si of alkali metal atoms M and Si atoms is preferably 0 to 10, more preferably 0.1 to 5, and even more preferably 0.5 to 3. The atomic ratio M / Si=0 indicates that all of the alkali metal atoms in the layered alkali metal silicate are substituted with Ti atoms.

[0038] In the AM-4 type titanosilicate obtained by the production method of the present invention, the atomic ratio M / Ti of the alkali metal atom M and the Ti atom is preferably 1-5, more preferably 1-4, and even more preferably 1.5-3.

[0039] The contents of Si atoms, Ti atoms, and alkali metal atoms in the compound can be adjusted by the amounts of layered alkali metal silicate, titanium compound, and alkali metal hydroxide used. For example, to increase the sodium ion concentration, the amount of layered alkali metal silicate or sodium hydroxide can be increased, and to decrease the sodium ion concentration, the amount of layered alkali metal silicate or sodium hydroxide can be decreased. To increase the titanium ion concentration, the amount of titanium compound can be increased, and to decrease the titanium ion concentration, the amount of titanium compound can be decreased.

[0040] The structure of the obtained titanosilicate can be evaluated based on the XRD (X-ray diffraction) pattern.

[0041] According to the production method of the present invention, it is possible to produce AM-4 type titanosilicate by simply subjecting a raw material mixture prepared by mixing a layered alkali metal silicate and a titanium compound directly with a single solvent (water or an aqueous solution of an alkali metal hydroxide) to hydrothermal synthesis. Therefore, the production method of the present invention makes it possible to produce AM-4 type titanosilicate without requiring the prior preparation of a silica source solution and a titanium source solution.

[0042] The reason why the production method of the present invention can produce AM-4 type titanosilicate is unclear, but it can be speculated as follows. Layered alkali metal silicates are composed of multiple layer structures, and these layer structures are believed to be bonded to each other via hydroxyl groups and alkali metal ions present in the interlayer spaces. It is believed that when a layered alkali metal silicate having such a structure is subjected to hydrothermal synthesis, the bonds between the layer structures are broken, and titanium ions are introduced through the expanded interlayer spaces. It is believed that the titanium ions are then replaced by alkali metal ions with a strong tendency to ionize (ion exchange), and the silicate, affected by the ion exchange and thermal energy, undergoes a phase change to AM-4 type titanosilicate via another phase type (e.g., ETS-4). [Example]

[0043] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[0044] Example 1 1 g of Kenyaite powder, 0.1 g of titania powder, and 50 mL of 1 M sodium hydroxide aqueous solution were mixed and stirred thoroughly to prepare a raw material mixture. The pH of the raw material mixture was 13. This raw material mixture was placed in an autoclave and hydrothermal synthesis was carried out at 240°C for 72 hours (3 days). XRD measurements were also performed on the resulting product to analyze its phase type.

[0045] <Examples 2 to 12 and Comparative Examples 1 to 7> The hydrothermal synthesis was carried out by changing the temperature and time of the hydrothermal synthesis as shown in Table 1 below, compared to Example 1. The other conditions were the same as in Example 1. The phase type of the resultant product was analyzed by XRD measurement.

[0046] Example 13 A raw material mixture was prepared by mixing 1 g of magadiite powder, 0.1 g of titania powder, and 50 mL of a 1 M sodium hydroxide solution and stirring thoroughly. The pH of the raw material mixture was 13-14. This raw material mixture was placed in an autoclave and hydrothermal synthesis was carried out at 240°C for 144 hours. The resulting product was also analyzed for phase type by XRD measurement.

[0047] <Examples 14 to 15 and Comparative Example 8> The hydrothermal synthesis was carried out by changing the temperature and time of the hydrothermal synthesis as shown in Table 2 below, compared to Example 13. The other conditions were the same as in Example 13. The phase type of the resultant product was analyzed by XRD measurement.

[0048] <Result> Fig. 1 shows the XRD patterns of Examples 1 to 4 and Comparative Example 1, Fig. 2 shows the XRD patterns of Example 5 and Comparative Examples 2 to 4, Fig. 3 shows the XRD patterns of Example 6 and Comparative Examples 5 to 7, Fig. 4 shows the XRD patterns of Examples 7 to 9, Fig. 5 shows the XRD patterns of Examples 10 to 12, and Fig. 6 shows the XRD patterns of Examples 13 to 15 and Comparative Example 8. The phase types of the resultant products analyzed from the XRD patterns are shown in Tables 1 and 2.

[0049] [Table 1]

[0050] [Table 2]

[0051] <Explanation of results> The presence or absence of AM-4 type titanosilicate can be confirmed based on the presence of a peak in the XRD pattern at around 6 degrees. From Figures 1 to 6, it was confirmed that AM-4 type titanosilicate was produced in Examples 1 to 15 of the present invention.

[0052] When the silica source is Kenyaite, it was found that a single-phase AM-4 type titanosilicate is produced, for example, in about 72 hours (Example 1) under a temperature condition of about 240°C, and in about 34 hours (Example 11) under a temperature condition of about 260°C.

[0053] From the results of Example 6, it is presumed that a temperature of approximately 210°C is required to produce AM-4 type titanosilicate. In Example 6, an unknown phase was also confirmed in addition to AM-4 and ETS-4. The unknown phase may simply be a phase of AM-4 type titanosilicate with a different amount of interlayer water.

[0054] The results of Example 13 show that when the silica source is magadiite, AM-4 type titanosilicate is produced in about 144 hours under temperature conditions of about 240°C.

Claims

1. A method for producing AM-4 type titanosilicate, comprising mixing a layered alkali metal silicate, a titanium compound, an alkali metal hydroxide, and water to prepare a raw material mixture, and subjecting the raw material mixture to hydrothermal synthesis at a temperature of 210°C or higher to obtain AM-4 type titanosilicate.

2. The method according to claim 1, wherein the temperature of the hydrothermal synthesis is 220°C or higher.

3. The method according to claim 1 or 2, wherein the hydrothermal synthesis time is 75 hours or more.

4. When the temperature of the hydrothermal synthesis is 210°C or more and less than 220°C, the time of the hydrothermal synthesis is 192 hours or more; When the temperature of the hydrothermal synthesis is 220°C or more and less than 230°C, the time of the hydrothermal synthesis is 144 hours or more; When the temperature of the hydrothermal synthesis is 230°C or more and less than 240°C, the time of the hydrothermal synthesis is 96 hours or more; When the temperature of the hydrothermal synthesis is 240°C or more and less than 260°C, the time of the hydrothermal synthesis is 72 hours or more; When the temperature of the hydrothermal synthesis is 260°C or more, the time of the hydrothermal synthesis is 23 hours or more; The method according to claim 1 or 2.

5. 3. The method according to claim 1, wherein the layered alkali metal silicate comprises at least one of kanemite, makatite, illaite, magadiite, and kenyaite.

6. 3. The method according to claim 1, wherein the titanium compound is at least one of titanium oxide, titanium halide, and organic titanium compound.

7. 3. The method according to claim 1, wherein the alkali metal hydroxide is at least one of sodium hydroxide and potassium hydroxide.

8. The method according to claim 1 or 2, wherein the temperature of the hydrothermal synthesis is 350°C or less.

9. The method according to claim 1 or 2, wherein the pH of the raw material mixture is 12.0 or higher.

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