JP7780180B2 - Titanosilicate and its manufacturing method, method for oxidizing phenols, and method for manufacturing dihydric phenols - Google Patents

Description

The present invention relates to a titanosilicate and a method for producing the same, a method for oxidizing phenols, and a method for producing dihydric phenols.

The aluminosilicate MCM-68 is a relatively new zeolite first synthesized by Mobil (Patent Document 1). This zeolite has a structure in which large pores (12-membered ring pores) and medium pores (10-membered ring pores) intersect three-dimensionally. This type of zeolite generally has a large surface area and large internal space, making it useful as a catalyst in oil refining and petrochemical processes, as well as for catalysts using relatively bulky organic molecules as substrates.

MCM-68 has a Si/Al ratio of 9 to 12, meaning it has a relatively high Al content, i.e., a relatively high number of active sites, and is therefore stable, making it suitable for use as an acid catalyst. Furthermore, MCM-68 has a high hydrocarbon adsorption capacity and exhibits high activity in reactions involving these compounds, such as the alkylation of aromatic hydrocarbons and the transalkylation, isomerization, disproportionation, and dealkylation of alkylaromatic hydrocarbons. For this reason, MCM-68 is expected to be a base material for catalysts used in hydrocarbon conversion reactions.

Zeolites with the FAU topology (FAU aluminosilicates) are known as starting materials for synthesizing 8-membered ring zeolites such as CHA, AEI, AFX, and ERI. FAU aluminosilicates are widely used industrially because they do not require structure-directing agents for synthesis and can be obtained at low cost.

FAU-type aluminosilicates are classified into X-type zeolites, which have a silicon-to-aluminum content ratio (Si/Al) of less than 2, and Y-type zeolites, which have a silicon-to-aluminum content ratio (Si/Al) of more than 2. X-type zeolites can be used, for example, as adsorbents with high ion exchange capacity and hydrophilicity. Y-type zeolites can be used, for example, as solid acid catalysts for fluid catalytic cracking in the petrochemical industry.

Since the safety of general zeolites improves as the Si/Al ratio increases, Y-type zeolites, which have a relatively low Al content, are used as solid acid catalysts that are stable under high-temperature conditions. By treating Y-type zeolites with steam and acid to remove the aluminum, zeolites with even greater stability can be obtained. The resulting zeolites are called USY (Ultra Stable Y)-type zeolites, and are important industrial catalysts.

On the other hand, titanium silicalite-1 (TS-1) is a representative titanosilicate zeolite, and is known to exhibit high activity and selectivity as a catalyst for the oxidation reaction of organic compounds, etc. (Patent Document 2). One known method for synthesizing a zeolite with high catalytic activity like TS-1 is to introduce titanium into the zeolite by treating dealuminated mordenite with high-temperature _TiCl4 vapor (Non-Patent Document 1). Furthermore, a method for producing a titanosilicate with catalytic performance equivalent to or superior to that of TS-1 by replacing the aluminum in MCM-68 with titanium is also known (Patent Document 3).

Special Publication No. 2002-535227 Japanese Patent Application Laid-Open No. 2004-175801 Patent No. 4923248

J. Phys. Chem. 1996, 100, 10316-10322

Conventional methods for producing titanosilicate are based on the idea of treating aluminosilicate with acid, removing the aluminum and modifying the vacant sites with titanium. However, when acid treatment is performed on the highly versatile FAU-type aluminosilicate, silicon fills the vacant sites left by the removal of aluminum atoms before titanium can reach them, making it difficult to modify with titanium. Therefore, several studies have been conducted to introduce zeolites with new structures that allow for titanium modification after acid treatment, but the challenge is that these zeolites are not easy to produce.

The present invention was made in light of the above circumstances, and its first object is to provide a titanosilicate with catalytic properties that has a basic skeleton of zeolite, which can be easily produced, and a method for producing the same. A second object of the present invention is to provide a method for oxidizing phenols and a method for producing dihydric phenols using the titanosilicate as a catalyst.

To solve the above problems, the present invention adopts the following measures.

(1) In one embodiment of the titanosilicate of the present invention, part of the aluminum in the framework of FAU zeolite is replaced with titanium, and the silicon to titanium content ratio (Si/Ti) is 20 or more.

(2) In the titanosilicate described in (1) above, it is preferable that the silicon to aluminum content ratio (Si/Al) is 1.5 or more.

(3) In the titanosilicate described in either (1) or (2), it is preferable that the titanosilicate has a peak in the wavelength range of 200 nm to 230 nm in the UV-vis spectrum.

(4) In the titanosilicate described in any one of (1) to (3), it is preferable that the water vapor adsorption amount is 50% or less compared to when the aluminum in the framework of the FAU-type zeolite is not replaced with titanium.

(5) In the titanosilicate described in any one of (1) to (4), it is preferable that hydrogen is contained in the pores of the FAU-type zeolite.

(6) A method for producing titanosilicate according to one aspect of the present invention is a method for producing titanosilicate according to any one of (1) to (5) above, which includes a titanium treatment step in which the FAU zeolite, while containing aluminum in its framework, is heated together with a gaseous titanium source and a reaction gas, and the FAU zeolite has a silicon-to-aluminum content ratio (Si/Al) of 1.5 or more.

(7) In the method for producing titanosilicate described in (6) above, it is preferable to further include an unreacted titanium removal step in which the FAU zeolite after the titanium treatment step is heated together with a reaction gas.

(8) The method for producing titanosilicate described in either (6) or (7) above may further include a calcination step of calcining the mixture at a temperature of 300°C or higher and 800°C or lower after the titanium treatment step or the unreacted titanium removal step.

(9) A method for oxidizing phenols according to one embodiment of the present invention uses the titanosilicate described in any one of (1) to (5) above as a catalyst to oxidize phenols.

(10) A method for producing a dihydric phenol according to one embodiment of the present invention involves oxidizing a phenol using the method for oxidizing a phenol described in (9) above, and using phenol as the phenol.

(11) In the method for producing a dihydric phenol described in (10) above, ethanol may be added as a solvent for the phenol and the titanosilicate.

(12) In the method for producing a dihydric phenol described in (10) above, dihydric propanol may be added as a solvent for the phenol and the titanosilicate.

The present invention provides a titanosilicate with catalytic properties that has a basic skeleton of easily produced zeolite, as well as a method for producing the same. The present invention also provides a method for oxidizing phenols and a method for producing dihydric phenols using the titanosilicate as a catalyst.

FIG. 1 is a diagram showing an example of the configuration of an apparatus for performing titanium treatment on an aluminosilicate. FIG. 2 is a diagram illustrating heating conditions associated with titanium treatment. FIG. 1 is a diagram illustrating heating conditions for a firing treatment after titanium treatment. 1 is a graph showing the results of X-ray diffraction analysis of the titanosilicates of Examples 1 to 4. 1 is a graph showing the results of X-ray diffraction analysis of the titanosilicates of Examples 5 to 7. 1 is a graph showing the results of X-ray diffraction analysis of the titanosilicate of Example 8. 1 is a graph showing the DR/UV-vis measurement results for titanosilicates of Examples 1 to 4 and Comparative Example 1. 1 is a graph showing the DR/UV-vis measurement results for titanosilicates of Examples 5 to 7 and Comparative Example 1. 1 is a graph showing the results of DR/UV-vis measurement for titanosilicates of Examples 1, 5, 7, and 8 and Comparative Example 1. 1 is a graph showing, on a real scale, the evaluation results of the amount of water vapor adsorption for the titanosilicate of Example 8. 1 is a graph showing the evaluation results of the water vapor adsorption amount for the titanosilicate of Example 8 on a semi-logarithmic scale.

The titanosilicate and its production method, the method for oxidizing phenols, and the method for producing dihydric phenol according to embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that the drawings used in the following description may show characteristic parts enlarged for ease of understanding, and the dimensional proportions of the components may not be the same as in reality. Furthermore, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited to them. Appropriate modifications can be made within the scope of the present invention.

The titanosilicate according to one embodiment of the present invention has a basic skeleton of a large-pore zeolite with FAU topology (hereinafter referred to as FAU aluminosilicate or FAU zeolite), with some of the aluminum in the skeleton replaced with titanium. FAU aluminosilicates are classified into X-type zeolites, Y-type zeolites, USY-type zeolites, etc., depending on the silicon-to-aluminum ratio (Si/Al) in the skeleton. Zeolites with a ratio (Si/Al) of 1.0 to 1.5 are called X-type zeolites, zeolites with a ratio (Si/Al) of 1.5 to 3.0 are called Y-type zeolites, and zeolites with a ratio of more than 5.0 are called USY-type zeolites.

In the titanosilicate of this embodiment, the silicon (Si) to titanium (Ti) content ratio (Si/Ti) within the skeleton is 20 or greater, preferably 50 or greater, and more preferably 100 or greater. While even a small amount of titanium may be present within the skeleton, it is preferable for the content ratio (Si/Ti) to be 1000 or less. The content ratio (Si/Ti) can be measured, for example, using ICP-AES.

Furthermore, in the titanosilicate of this embodiment, the silicon (Si) to aluminum (Al) content ratio (Si/Al) is 1.5 or more, preferably 100 or more, and more preferably 500 or more. Furthermore, aluminum need not be contained in the skeleton at all, and the content ratio (Si/Al) may be 1000 or less. The content ratio (Si/Al) can be measured, for example, using the ICP-AES method.

The titanium atoms contained in the titanosilicate of this embodiment have a tetracoordinated crystal structure and are properly incorporated into the framework. The crystalline structure of the titanium atoms can be confirmed by the peak position in the UV-vis spectrum. If the peak in the UV-vis spectrum is in the wavelength range of 200 nm to 230 nm, the titanium atoms are considered to have a tetracoordinated crystal structure.

The water vapor adsorption capacity of the titanosilicate of this embodiment is 10% to 50%, preferably 10% to 20%, based on the state in which the aluminum in the framework is not replaced with titanium (i.e., the state without titanium treatment). In other words, the titanosilicate of this embodiment, which has an FAU zeolite framework, has increased hydrophobicity due to titanium treatment. Therefore, even in an uncalcined state, the titanosilicate of this embodiment has a high hydrophobicity equivalent to that of calcined titanosilicates with frameworks other than FAU zeolite.

The titanosilicate of this embodiment contains hydrogen atoms in the pores that make up the FAU-type zeolite. The hydrogen atom content (H/(Na+H)) based on the total amount of hydrogen atoms and sodium atoms located at the ion exchange sites is preferably 95% or more and 100% or less.

As described above, the titanosilicate of this embodiment has a basic skeleton of the highly versatile FAU-type zeolite and is highly hydrophobic. Therefore, a high proportion of titanium atoms are introduced into the skeleton, resulting in excellent catalytic performance, as will be described later in the examples.

[Method for producing titanosilicate]
The method for producing titanosilicate of this embodiment mainly includes a first step of preparing an FAU-type aluminosilicate, and second and third steps of introducing titanium into the FAU-type aluminosilicate. A fourth step of firing may be included after the third step. The treatment in each production step will be described below.

(First step)
First, a crystallized FAU-type aluminosilicate (FAU-type zeolite) is prepared. Commercially available FAU-type aluminosilicates can be used. As examples, commercially available products from Tosoh Corporation and Zeolyst International are listed in Tables 1 and 2, respectively. The contents of Table 1 are disclosed on the Internet at URL: https://www.tosoh.co.jp/zeolite/hsz/list01.html. The contents of Table 2 are disclosed on the Internet at URL: https://www.zeolyst.com/our-products/standard-zeolite-powders/zeolite-y.html. The structure of any FAU-type aluminosilicate, including those listed in Tables 1 and 2, can be uniquely identified from the results of X-ray diffraction (XRD) analysis.

(Second process)
The prepared FAU-type aluminosilicate powder is subjected to a titanium treatment, i.e., a treatment for introducing (modifying) titanium into each site constituting the FAU-type framework. Specifically, the FAU-type aluminosilicate powder is heated together with a gaseous titanium source (e.g., titanium chloride, titanium alkoxide, etc.) and a reactive gas (e.g., an inert gas such as argon, nitrogen, or helium) in a state where the framework contains aluminum at a ratio of about 5% to 20%. This treatment introduces titanium into at least some of the aluminum sites constituting the framework of the FAU-type aluminosilicate, while also removing aluminum from the aluminum sites where titanium has been introduced. As a result, at least some of the aluminum constituting the FAU-type aluminosilicate is replaced with titanium. FIG. 1 is a diagram showing an example of the configuration of a titanium treatment apparatus 10.

The titanium processing device 10 mainly comprises a glass tube 11, a heater 12 arranged around the glass tube 11, a temperature controller 13 connected to the heater 12, a container 14 containing a titanium source, and an inert gas supply source 15. The glass tube 11, titanium source container 14, and inert gas supply source 15 are connected to each other by tubing via a four-way valve 16, and are configured so that the inert gas can be switched between a flow path that goes directly to the glass tube 11 and a flow path that goes via the titanium source container 14 to the glass tube 11 at any time.

The titanium treatment procedure is explained using Figure 1. First, powdered FAU-type aluminosilicate crystals S are surrounded by a fibrous material (not shown) such as quartz wool, and then fixed inside the glass tube 11 via this fibrous material.

First, the flow path is switched so that the inert gas flows directly into the glass tube 11, and the FAU-type aluminosilicate crystals S are heated while an inert gas such as argon, nitrogen, or helium is circulating through the glass tube 11. The heating temperature is preferably 300°C or higher and 800°C or lower, and more preferably around 500°C. The heating time is preferably 1 hour or higher and 12 hours or lower, and more preferably around 4 hours.

Then, the inert gas is switched to a flow path that passes through the titanium source container 14 and heads toward the glass tube 11, and the FAU-type aluminosilicate crystals S are heated while the inert gas and the titanium source, titanium chloride or titanium alkoxide in gas phase, are circulating through the glass tube 11.

Figure 2 is a diagram explaining the heating conditions associated with titanium treatment. First, the FAU-type aluminosilicate crystals S are heated at a nearly constant rate over a period of approximately four hours to a predetermined heating temperature. The heating temperature is preferably between 300°C and 800°C, and more preferably around 600°C. Once the heating temperature is reached, that temperature is maintained for the set heating time. The heating time is preferably between 0.5 hours and 6 hours, and more preferably around 1 hour. This heating introduces titanium into at least some of the sites that make up the framework of the FAU-type aluminosilicate. After the heating time has elapsed, heating is stopped and the crystals are cooled.

Examples of titanium chlorides used here include TiCl ₄ and TiCl _3. Examples of titanium alkoxides used here include Ti(OMe) ₄ , Ti(OEt) ₄ , Ti(OPr) ₄ , Ti(OPr-i) ₄ , and Ti(OBu) ₄ .

(Third step)
Next, the flow path is switched so that the inert gas flows directly into the glass tube 11, and the inert gas is again circulated through the glass tube 11 without changing the heating temperature or heating time. This removes any unreacted titanium source remaining in the crystal structure of the FAU-type aluminosilicate after the introduction of titanium. After the removal of the unreacted titanium source, the FAU-type aluminosilicate is allowed to cool to room temperature, washed with distilled water, and dried in an oven at approximately 80°C.

The above-described process allows for the synthesis of a titanosilicate with a basic FAU-type aluminosilicate skeleton, in which some of the aluminum has been replaced with titanium. The silicon-to-titanium (Si/Ti) content ratio within the skeleton of the synthesized titanosilicate is generally 50 or higher. This content ratio can be adjusted by adjusting the heating conditions.

(Fourth step)
From the viewpoint of increasing the ortho selectivity, the synthesized titanosilicate may be further calcined. FIG. 3 is a diagram illustrating the heating conditions for the calcination treatment after the titanium treatment. First, the titanosilicate is heated to the calcination temperature at a substantially constant rate in the range of about 0.8°C/min to 1.2°C/min, preferably at a rate of about 1°C/min. The calcination temperature is preferably in the range of 300°C to 800°C, and more preferably about 650°C. Once the calcination temperature is reached, the temperature is maintained for the set calcination time. The calcination time is preferably in the range of 1 hour to 12 hours, and more preferably about 4 hours. After the calcination time has elapsed, the calcination is stopped and the mixture is allowed to cool.

As described above, the titanosilicate manufacturing method of this embodiment makes it possible to obtain titanosilicate with an FAU-type basic skeleton. FAU-type aluminosilicate is easy to manufacture and is one of the most widely used zeolites, so this technology, which makes it possible to introduce titanium into this zeolite, is expected to make a significant contribution to industrial development.

According to the method for producing titanosilicate of this embodiment, aluminum atoms are present at each site constituting the skeleton until just before the titanium atoms reach it, thereby avoiding the problem of silicon atoms interfering with the introduction of titanium atoms. Furthermore, titanosilicates with an FAU-type aluminosilicate as their basic skeleton are sufficiently hydrophobic even in an uncalcined state, making it easy to attract titanium atoms to each site constituting the skeleton and maintaining a stable crystal structure. Therefore, according to the method for producing titanosilicate of this embodiment, acid treatment is not required when introducing titanium into a skeleton other than the FAU-type, and the calcination treatment can also be omitted, thereby significantly simplifying the process compared to conventional production methods.

[Method for oxidizing phenol, method for producing dihydric phenol]
Phenols can be oxidized by an oxidation reaction using the titanosilicate as a catalyst. The phenols to be oxidized are not particularly limited, but examples thereof include phenol, cresol, aminophenol, salicylic acid, etc.

Dihydric phenols can be produced by oxidizing phenol. As described in the examples below, the dihydric phenols produced mainly include hydroquinone HQ (the para-isomer of dihydric phenol), catechol CL (the ortho-isomer of dihydric phenol), and parabenzoquinone p-BQ, which is obtained by further oxidizing hydroquinone HQ. Solvents for the phenol and titanosilicate used in the reaction are not essential, but examples include ethanol, dihydric propanol, acetonitrile, and sulfolane.

The phenol oxidation reaction of this embodiment tends to produce catechol CL, which can be used in pharmaceuticals, etc., in high yield. This yield can be adjusted by changing the ratio of silicon to titanium (Si/Ti) contained in the titanosilicate catalyst.

The following examples will make the effects of the present invention clearer. Note that the present invention is not limited to the following examples, and can be modified as appropriate within the scope of its gist.

Examples 1 to 4
Four samples of approximately 1.0 g of HSZ-360HUA manufactured by Tosoh Corporation were prepared as FAU-type aluminosilicate crystals. Using the titanium treatment apparatus 10 shown in Figure 1, each of the four samples (Examples 1 to 4) was separately subjected to titanium treatment (second step) according to the following procedure. The ratio of silicon to aluminum (Si/Al) contained in HSZ-360HUA was 8.07.

First, HSZ-360HUA crystal S was surrounded by quartz wool and fixed inside the quartz tube 11 via the quartz wool.

Next, the flow path was switched so that the argon gas was directed directly into the glass tube 11, and the crystal S was heated while argon gas was circulating inside the quartz tube 11. The temperature was raised from room temperature to approximately 700°C at a nearly constant rate over approximately four hours.

Then, the argon gas flow path was switched to pass through the titanium source container 14 and head toward the glass tube 11. The crystal S was heated while argon gas and titanium tetrachloride gas, which serves as the titanium source, were flowing through the quartz tube 11. The heating temperature was approximately 700°C, and the heating time was approximately 1 hour. The flow rate of the argon gas was 30 mL/min.

Next, the flow path was switched so that the inert gas was directed directly toward the quartz tube 11, and the inert gas was again circulated through the quartz tube 11 for approximately one hour without changing the heating temperature or heating time, thereby removing any unreacted titanium source remaining in the crystals S (third step).

Finally, Crystal S was allowed to cool to room temperature over approximately 10 minutes, washed with distilled water, and dried in an oven at approximately 80°C.

Through the above-described process, we were able to synthesize the titanosilicates of Examples 1 to 3, which have the basic skeleton of an FAU-type aluminosilicate and in which some of the Al has been replaced with Ti.

The synthesized titanosilicates of Examples 1 and 3 were further calcined (fourth step). Specifically, the temperature was raised at a constant rate from room temperature to approximately 650°C over approximately 10 hours and 20 minutes in an air atmosphere, then held at approximately 650°C for approximately 4 hours, and finally allowed to cool.

(Examples 5 and 6)
Two samples of approximately 1.0 g each of HSZ-360HUA manufactured by Tosoh Corporation were prepared as FAU-type aluminosilicate crystals. The two samples (Examples 5 and 6) were subjected to the same treatment as in Examples 1 and 3, except that the temperature at which they were heated together with the titanium source was approximately 600°C.

Example 7
As the FAU-type aluminosilicate crystals, one sample of approximately 1.0 g of HSZ-360HUA manufactured by Tosoh Corporation was prepared. This sample (Example 7) was subjected to the same treatment as in Examples 1 and 3, except that the temperature at which it was heated together with the titanium source was set to approximately 650°C.

(Example 8)
As the FAU-type aluminosilicate crystals, one sample of approximately 1.0 g of HSZ-370HUA manufactured by Tosoh Corporation was prepared. The ratio of silicon to aluminum (Si/Al) contained in HSZ-370HUA was 15. This sample (Example 8) was subjected to the same treatment as in Examples 5 and 6.

The silicon-to-aluminum content ratio (Si/Al) and silicon-to-titanium content ratio (Si/Ti) were measured for the titanosilicates obtained in Examples 1 to 8. The measurement results are shown in Table 3.

(Comparative Example 1)
Titanium silicalite-1 (TS-1), designated and distributed by the Catalysis Society as the Asia Reference Catalyst (ARC), was prepared.

[Evaluation of X-ray diffraction patterns]
X-ray diffraction (XRD) analysis was performed on the samples of Examples 1 to 8. Diffraction patterns showing the analysis results are shown in the graphs of Figures 4 to 6. The horizontal axis of the graph represents the diffraction angle, and the vertical axis represents the diffraction intensity.

The graph in FIG. 4 shows an array of diffraction patterns obtained for a crystalline sample of HSZ-360HUA under the following conditions:
First stage: Initial state before titanium treatment (state after the first step in the above embodiment)
Second row: As in Example 1, titanium treatment was performed but no firing was carried out. Third row: As in Example 1, titanium treatment was performed but no firing was carried out. Fourth row: As in Example 2, titanium treatment was performed but no firing was carried out. Fifth row: As in Example 3, titanium treatment was performed but no firing was carried out. Sixth row: As in Example 3, titanium treatment was performed but no firing was carried out. Seventh row: As in Example 4, titanium treatment was performed but no firing was carried out.

The graph in FIG. 5 shows an array of diffraction patterns obtained for a crystalline sample of HSZ-360HUA under the following conditions:
First stage: Initial state before titanium treatment (state after the first step in the above embodiment)
Second row: As in Example 5, titanium treatment was performed but not calcined. Third row: As in Example 5, titanium treatment was performed but calcined. Fourth row: As in Example 6, titanium treatment was performed but not calcined. Fifth row: As in Example 6, titanium treatment was performed but calcined. Sixth row: As in Example 7, titanium treatment was performed but not calcined. Seventh row: As in Example 7, titanium treatment was performed but calcined.

The graph in FIG. 6 shows an array of diffraction patterns obtained for a crystalline sample of HSZ-370HUA under the following conditions:
First stage: Initial state before titanium treatment (state after the first step in the above embodiment)
Second row: Example 8, titanium treatment was performed but not sintered. Third row: Example 8, titanium treatment was performed and sintered.

Comparing the graphs in Figures 4 to 6, it can be seen that similar XRD patterns were obtained for all samples. These results show that high crystallinity was maintained before and after each process, whether the Si/Al ratio was varied between 6.8 and 15, or the titanium treatment temperature was varied between 600°C and 700°C. It also shows that reproducibility was achieved between different samples processed under the same conditions.

[Evaluation of Ti Coordination State]
DR/UV-Vis measurements were performed on the samples of Examples 1 to 8. The DR/UV-Vis spectra showing the measurement results are shown in the graphs of Figures 7 to 9. The horizontal axis of the graph represents wavelength (nm), and the vertical axis represents the Kubelka-Munk function.

The graph in FIG. 7 shows the DR/UV-Vis spectra obtained under the following conditions for a crystalline sample of HSZ-360HUA and a crystalline sample of titanium silicalite-1.
First row: Comparative example 1, titanium treatment was performed but not fired. Second row: Example 1, titanium treatment was performed but not fired. Third row: Example 1, titanium treatment was performed but not fired. Fourth row: Example 2, titanium treatment was performed but not fired. Fifth row: Example 3, titanium treatment was performed but not fired. Sixth row: Example 3, titanium treatment was performed but not fired. Seventh row: Example 4, titanium treatment was performed but not fired.

The graph in FIG. 8 shows the DR/UV-Vis spectra obtained under the following conditions for a crystalline sample of HSZ-360HUA and a crystalline sample of titanium silicalite-1.
First row: Comparative example 1, titanium treatment was performed but not fired. Second row: Example 5, titanium treatment was performed but not fired. Third row: Example 5, titanium treatment was performed but not fired. Fourth row: Example 6, titanium treatment was performed but not fired. Fifth row: Example 6, titanium treatment was performed but not fired. Sixth row: Example 7, titanium treatment was performed but not fired. Seventh row: Example 7, titanium treatment was performed but not fired.

The graph in FIG. 9 shows the DR/UV-Vis spectra obtained under the following conditions for a crystalline sample of HSZ-370HUA and a crystalline sample of titanium silicalite-1.
First row: Comparative example 1, titanium treatment was performed but not calcined. Second row: Example 8, titanium treatment was performed but not calcined. Third row: Example 8, titanium treatment was performed but not calcined. Fourth row: Example 5, titanium treatment was performed but not calcined. Fifth row: Example 5, titanium treatment was performed but not calcined. Sixth row: Example 7, titanium treatment was performed but not calcined. Seventh row: Example 1, titanium treatment was performed but not calcined.

The wavelength region of 200 to 230 nm is the region that shows absorption corresponding to tetracoordinated Ti within the framework. The wavelength region of 250 to 290 nm is the region that shows absorption corresponding to pentacoordinated or hexacoordinated Ti outside the framework.

In the graphs of Figures 7 to 9, the DR/UV-Vis spectra corresponding to the samples of Examples 1 to 8 all have peaks in the wavelength region of 200 to 230 nm. These results demonstrate that titanium was properly incorporated into the FAU-type framework of the synthesized titanosilicate, regardless of whether the Si/Al ratio was varied between 6.8 and 15, or whether the titanium treatment temperature was varied between 600°C and 700°C. It also demonstrates that reproducibility was achieved between different samples treated under the same conditions.

[Evaluation of water vapor adsorption amount]
The water vapor adsorption amount at 25°C was evaluated for samples in the following three states of Example 1 (state before titanium was introduced, state immediately after titanium was introduced, and state after titanium was introduced and calcined). The water vapor adsorption isotherms used for the evaluation are shown in the graphs of Figures 10 and 11 on a linear scale and a semi-logarithmic scale, respectively. The horizontal axis of the graph represents relative pressure, and the vertical axis represents the water vapor adsorption amount. Here, the state before titanium was introduced is plotted with a square, the state immediately after titanium was introduced is plotted with a triangle, and the state after titanium was introduced and calcined is plotted with a circle.

A comparison of the state before and immediately after the introduction of titanium shows that the introduction of titanium significantly reduces the amount of water vapor adsorption, resulting in hydrophobicity. More specifically, the amount of water vapor adsorption by the aluminum in the framework of the FAU-type aluminosilicate is approximately 30% to 50% less than when it is not replaced with titanium. On the other hand, a comparison of the state immediately after the introduction of titanium with the state after calcination after the introduction of titanium shows that the amount of water vapor adsorption is roughly the same before and after calcination, with almost no hydrophobicity due to calcination being observed.

[Evaluation of catalytic performance for phenol oxidation reaction]
Using the samples of Examples 5 to 7 as catalysts, an experiment was carried out on the phenol oxidation reaction shown in the following chemical reaction formula.

The specific experimental procedure is as follows: First, 20 mg of catalyst, 2.00 g (21.3 mmol) of phenol, and 0.48 g (4.25 mmol) of hydrogen peroxide (30 wt%) were mixed in a glass pressure vessel and stirred at 100°C for 60 minutes. After the reaction was completed, the vessel was cooled on ice and diluted with 2.0 g (16.64 mmol) of sulfolane. 0.225 g (2.08 mmol) of anisole was added as an internal standard substance and mixed thoroughly, after which the reaction mixture was separated from the catalyst by centrifugation (3500 rpm, 10 minutes).

Next, to approximately 150 mg of the supernatant, excess acetic anhydride (approximately 0.4 g) and potassium carbonate (approximately 0.6 g) were added, and the entire reaction mixture was kept at approximately 20-50°C and left for 30 minutes with occasional shaking to thoroughly acetylate any phenolic compounds present. The mixture was then diluted with chloroform and analyzed using a gas chromatograph (Shimadzu GC-2014, detector: FID, column: DB-1 0.25 mm x 30 m x 1.00 μm). Additionally, to quantify the amount of unreacted hydrogen peroxide, 0.5 g of the centrifuged supernatant and 0.8 g of potassium iodide were added to 50 mL of 2.0 mol/L aqueous hydrochloric acid, and the mixture was titrated with an aqueous sodium thiosulfate solution with an exact concentration of approximately 0.1 mol/L.

The results of the above analysis detected hydroquinone (a para-isomer of dihydric phenol) HQ, catechol (an ortho-isomer of dihydric phenol) CL, and parabenzoquinone p-BQ, which is formed by further oxidation of HQ.

Table 4 shows the calcination status of each sample, the Ti content, catalyst turnover number (TON), yield, para-isopropyl selectivity (p-sel. (%)), H ₂ O ₂ conversion (H ₂ O ₂ (%) conv.), and effective utilization rate of H ₂ O ₂ (H ₂ O ₂ (%) eff.) in this experiment. (eff. is an abbreviation for efficiency.)

The sum of the yields of HQ, p-BQ, and CL is shown as the total yield. The selectivity of the para isomer (p-sel.) is shown as the sum of HQ and p-BQ divided by the total. TON (catalytic turnover number) is the total amount of product substance (number of moles) divided by the number of moles of Ti active sites. In other words, TON is an indicator of how many times the catalytic cycle has been completed from the start of the reaction to the end of the reaction (60 minutes in this case).

H ₂ O ₂ (%) eff. (effective H ₂ O ₂ utilization rate) is the effective utilization rate of hydrogen peroxide, and is an index showing the efficiency with which oxygen in hydrogen peroxide is involved in phenol oxidation.

The results in Table 4 show that all samples exhibited phenol oxidation activity and para selectivity, indicating that titanosilicates with catalytic functionality were obtained. In particular, it can be seen that in all samples, the catalytic functionality (yield, TON, etc.) in the uncalcined state exceeded the catalytic functionality in the calcined state. This result is unique and cannot be seen when a framework other than FAU is used.

The results in Table 4 also show that calcination reduces para selectivity and increases ortho selectivity. These results suggest that para selectivity and ortho selectivity can be adjusted by changing the calcination temperature.

10 Titanium processing device 11 Quartz tube 12 Heater 13 Temperature controller 14 Titanium source container 15 Inert gas supply source 16 Four-way valve S Crystal

Claims (11)

A part of aluminum in the framework of FAU zeolite is replaced with titanium,
The silicon to titanium content ratio (Si/Ti) is 20 or more,
A titanosilicate characterized in that the amount of water vapor adsorption is 50% or less compared to when the aluminum in the framework of the FAU-type zeolite is not replaced with titanium. The titanosilicate according to claim 1, characterized in that the silicon to aluminum content ratio (Si/Al) is 1.5 or more. The titanosilicate described in either 1 or 2, characterized in that it has a peak in the wavelength range of 200 nm to 230 nm in the UV-vis spectrum. The titanosilicate according to any one of claims 1 to 3, characterized in that hydrogen is contained in the pores of the FAU-type zeolite. A method for producing the titanosilicate according to any one of claims 1 to 4,
a titanium treatment step of heating the FAU zeolite, with aluminum contained in the framework, together with a gaseous titanium source and a reaction gas;
A method for producing titanosilicate, characterized in that the FAU-type zeolite has a silicon to aluminum content ratio (Si/Al) of 1.5 or more. The method for producing titanosilicate described in claim 5 further comprises a step of removing unreacted titanium by heating the FAU-type zeolite together with a reaction gas after the titanium treatment step. 7. The method for producing titanosilicate according to claim 6 , further comprising a calcination step of performing calcination at 300° C. or higher and 800° C. or lower after the unreacted titanium removal step. A method for oxidizing phenols, comprising oxidizing phenols using the titanosilicate according to any one of claims 1 to 4 as a catalyst. The phenols are oxidized using the method for oxidizing phenols according to claim 8,
A method for producing a dihydric phenol, wherein phenol is used as the phenol. The method for producing a dihydric phenol according to claim 9, characterized in that ethanol is added as a solvent for the phenol and the titanosilicate. The method for producing dihydric phenol described in claim 9, characterized in that dihydric propanol is added as a solvent for the phenol and the titanosilicate.