JP5419042B2 - Method for producing RTH-type zeolite - Google Patents

Description

  The present invention relates to a method for producing an RTH type zeolite, and more particularly to a method for producing an RTH type zeolite without using a structure-directing agent.

  In addition to the naturally occurring zeolite minerals, many synthetic zeolites are known. RTH-type zeolite is one of the synthetic zeolites having oxygen 8-membered ring pores, and has a topology classified into the structure code RTH described in “Atlas of Zeolite framework types fifth revised edition 2001 (ELSEVIER)”. . By using this as a catalyst, RTH type zeolite can selectively synthesize olefins having 4 or less carbon atoms from methanol, and also hydrocracking, dewaxing reaction, catalytic cracking, oligomerization reaction, olefin It is a useful zeolite that also functions as a catalyst for reactions such as isomerization reaction, methane upgrading, and alcohol condensation reaction.

  RUB-13 (Patent Document 1) has been reported as a zeolite having an RTH type structure. The synthesis of RUB-13 requires a structure-directing agent, and RUB-13 is synthesized from a gel using ethylenediamine and pentamethylpiperidine as a structure-directing agent with respect to a silica raw material.

USP 5,614,166

As described above, the RTH zeolite is a zeolite that is a useful catalyst for various reactions, but a structure-directing agent is required for its synthesis. That is, normally, when the RTH type zeolite was hydrothermally synthesized without using a structure-directing agent, it took an amorphous structure without crystallization, and no zeolite was obtained. In some cases, the quartz structure is a SiO ₂ crystal having no pores. For this reason, a structure directing agent has been considered an essential component for the synthesis of RTH type zeolite.
However, the structure-directing agent occupies a large part of the synthesis cost of zeolite, and the zeolite synthesized using the structure-directing agent is more expensive than those not using it. In addition, when hydrothermal synthesis is performed using a structure directing agent, a process for removing the structure directing agent by firing or solvent extraction is necessary as a subsequent processing step, and the cost is increased due to an increase in the number of steps. It was.
For these reasons, conventional RTH zeolite synthesized using a structure-directing agent is expensive, and thus is restricted for use as an industrial zeolite.
For this reason, development of the manufacturing method of the RTH type zeolite which reduced the usage-amount of the structure-directing agent or does not use has been desired.

  Accordingly, an object of the present invention is to provide a method for producing an RTH type zeolite without using a structure-directing agent or using a small amount of a structure-directing agent.

In order to solve the above-mentioned problems, the present inventors have studied the synthesis conditions of RTH zeolite under the condition that the amount of the structure-directing agent is reduced or the structure-directing agent is not used.
As described above, in the past, it was considered that a structure-directing agent was essential for the production of RUB-13. However, under the conditions in which only the point that the structure-directing agent was not added was simply changed from the synthesis conditions of Patent Document 1. The product became amorphous and no RTH type zeolite was obtained.

However, as a result of intensive studies by the present inventors, there was no structure-directing agent when an alkali metal element and / or alkaline earth metal element was added to the aqueous mixture of the precursor of hydrothermal synthesis at a certain ratio. However, it has been found that RTH type zeolite can be synthesized. In the method described in Patent Document 1, synthesis is performed using a structure-directing agent under the condition that no alkali metal element or alkaline-earth metal element is present, but when no structure-directing agent is used, an alkali metal element or alkaline earth is used. Due to the presence of the metal-like element, crystallization of the zeolite became possible.
Moreover, by adding seed crystals to the aqueous mixture of hydrothermal synthesis precursors, crystallization was further promoted, and an RTH zeolite with higher crystallinity was successfully obtained, leading to the present invention.

  That is, the first gist of the present invention is a silica raw material, an alkali metal element and / or an alkaline earth metal element, and at least one kind of hetero element other than oxygen, silicon, an alkali metal element, and an alkaline earth metal element. And the molar ratio of the alkali metal element and / or alkaline earth metal element to silica is in the range of 0.01 to 0.45 and does not contain a structure directing agent or The present invention resides in a method for producing an RTH type zeolite, which comprises hydrothermally synthesizing an aqueous mixture containing an agent / Si molar ratio of 0.018 or less.

  The second gist lies in a method for producing an RTH type zeolite, characterized in that, in the above method, the aqueous mixture does not contain a structure-directing agent.

  The third gist lies in a method for producing an RTH-type zeolite, characterized in that, in the above method, only an alkali metal element is contained as an alkali metal element and / or an alkaline earth metal element.

  The fourth gist lies in a method for producing an RTH type zeolite, characterized in that, in the above method, the alkali metal element is sodium.

  The fifth gist lies in a method for producing an RTH type zeolite characterized in that, in the above method, zeolite is added as a seed crystal to the aqueous mixture and hydrothermal synthesis is performed.

  The sixth gist lies in a method for producing an RTH type zeolite, characterized in that, in the above method, the seed crystal is a zeolite having a 4-membered ring as a secondary building unit.

  The seventh gist lies in a method for producing an RTH type zeolite, characterized in that, in the above method, the zeolite as the seed crystal is an RTH type zeolite.

The eighth gist lies in a method for producing an RTH type zeolite, characterized in that, in the above method, the ratio of water in the aqueous mixture is 40 or more in terms of H ₂ O / Si molar ratio.

  The ninth gist lies in a method for producing an RTH type zeolite, characterized in that, in the above method, the hetero element is at least one element selected from the group consisting of aluminum, gallium and boron.

According to the present invention, an RTH-type zeolite can be synthesized without using a structure-directing agent, or with a smaller amount of structure-directing agent used than before, and without using a structure-directing agent, or with a structure-directing agent. By reducing the amount used, the production cost of the RTH type zeolite can be significantly reduced. In addition, according to the present invention, RTH type zeolite can be synthesized without using the structure directing agent itself, so that not only the preparation process of the structure directing agent itself but also the structure prescribing such as firing after hydrothermal synthesis and solvent extraction. The removal step of the agent can be omitted, and the manufacturing process can be greatly improved in efficiency.
Furthermore, in the present invention, by not using a structure-directing agent or by reducing the amount of use thereof, amines as a synthesis raw material for the structure-directing agent are unnecessary or reduced as much as possible. The safety of the work environment is also improved.

It is a figure which shows the XRD pattern of the product obtained in Example 1 of this invention. It is a figure which shows the SEM image of the product obtained in Example 1 of this invention. It is a diagram showing the ²⁹ Si-MAS NMR spectrum of the product obtained in Example 1 of the present invention. It is a diagram showing the ¹¹ B-MAS NMR spectra of Example 1 the product obtained in the present invention. It is a figure which shows the XRD pattern of the product obtained in Example 2-5 of this invention. It is a figure which shows the SEM image of the product obtained in Example 2 of this invention. It is a figure which shows the SEM image of the product obtained in Example 3 of this invention. It is a figure which shows the SEM image of the product obtained in Example 4 of this invention. It is a figure which shows the SEM image of the product obtained in Example 5 of this invention. It is a diagram showing the ²⁹ Si-MAS NMR spectrum of the product obtained in Example 2 of the present invention. It is a diagram showing the ¹¹ B-MAS NMR spectra of Example 2 the product obtained in the present invention. It is a diagram showing the ²⁷ Al-MAS NMR spectra of the product obtained in Example 2 of the present invention. It is a figure which shows the XRD pattern of the product obtained in Example 6 of this invention. It is a figure which shows the SEM image of the product obtained in Example 6 of this invention. It is a figure which shows the XRD pattern of the product obtained in Example 7 of this invention. It is a figure which shows the XRD pattern of the product obtained in the comparative example 1. It is a figure which shows the XRD pattern of the product obtained in the comparative example 2. It is a figure which shows the XRD pattern of the product obtained by the comparative example 3. It is a figure which shows the XRD pattern of the product obtained in the comparative example 4. It is a figure which shows the XRD pattern of the product obtained in Example 8 of this invention.

  Hereinafter, typical embodiments for carrying out the present invention will be specifically described. However, the present invention is not limited to the following embodiments as long as the gist thereof is not exceeded.

  The present invention is a method of synthesizing an RTH type zeolite without using a structure directing agent that has been conventionally required for the production of RTH type zeolite or using a small amount of a structure directing agent.

In the present invention, an alkali metal element and / or an alkaline earth metal element (hereinafter, referred to as “gel”) is added to an aqueous mixture (hereinafter sometimes referred to as “gel”) as a crystal precursor when producing zeolite by hydrothermal synthesis. These may be collectively referred to as “alkali (earth) metal elements.”) In a certain ratio, so that no structure-directing agent is used or a small amount of structure-directing agent is used. Makes it possible to synthesize RTH-type zeolite.
In the method for producing an RTH type zeolite of the present invention, an RTH type zeolite can be synthesized according to a conventional method of hydrothermal synthesis of zeolite except for this feature. That is, an aqueous mixture of a crystal precursor containing a silica raw material, a hetero element source, and an alkali (earth) metal element source can be prepared and synthesized by heating. Here, the “aqueous mixture” refers to a mixture obtained by dissolving or dispersing a raw material compound using water as a main solvent.
Hereinafter, an example of the manufacturing method will be described.

<Silica raw material>
The silica raw material used in the present invention is not particularly limited, and examples thereof include fine silica, silica sol, silica gel, silicon dioxide, water glass and other silicates, silicon alkoxides such as tetraethoxyorthosilicate and tetramethoxysilane, silicon halides, and the like. It is done. Moreover, you may use silica containing zeolites, such as MFI and FAU, as a silica raw material.
These silica raw materials may be used individually by 1 type, and 2 or more types may be mixed and used for them.
Of these silica raw materials, one or more of silicates such as finely divided silica, silica sol, silica gel, silicon dioxide, and water glass are preferably used in view of cost advantage and ease of handling. More preferably, fine powder silica and water glass are used in terms of reactivity.

<Hetero element>
The gel according to the present invention contains at least one hetero element (hereinafter simply referred to as “hetero element”) other than silicon, oxygen, and an alkali (earth) metal element as an inorganic substance forming zeolite. Although it does not specifically limit as this hetero element, Preferably it is a metal element or boron, More preferably, aluminum, gallium, boron, tin, iron, titanium, zinc, indium, manganese, chromium, cobalt, zirconium etc. are mentioned. Only 1 type may be contained in the gel and 2 or more types may be contained in the gel.

  Particularly preferred hetero elements for the present invention are aluminum, gallium and boron, and particularly preferred is boron. This is because an RTH structure is easily obtained when boron is present in the gel during hydrothermal synthesis.

The hetero element source (hetero element raw material compound) used for the preparation of the aqueous mixture is not particularly limited, and is selected from, for example, sulfates, nitrates, hydroxides, oxides, and alkoxides of these hetero elements.
Of these hetero element sources, sulfates, nitrates, hydroxides, and alkoxides are preferable in terms of reactivity. In terms of cost and work, sulfate, nitrate and hydroxide are more preferable.

  For example, as the aluminum source, aluminum alkoxide such as pseudoboehmite, aluminum isopropoxide, aluminum triethoxide, aluminum hydroxide, alumina sol, sodium aluminate, aluminum nitrate, and alumina sulfate sol are usually used. Aluminum oxide, aluminum nitrate, and aluminum sulfate are more preferable.

  Moreover, as a boron source, boric acid, sodium borate, boron oxide etc. are used normally, Preferably they are boric acid and sodium borate, More preferably, it is boric acid.

  As the gallium source, gallium sulfate, gallium nitrate, gallium phosphate, gallium chloride, gallium bromide, and gallium hydroxide are usually used, preferably gallium nitrate and gallium chloride, and more preferably gallium nitrate. .

  These hetero element sources may be used alone, in combination of two or more of the same hetero elements, or in combination of one or more of the different hetero elements. It may be used.

<Alkali (earth) metal element>
The alkali (earth) metal element contained in the gel according to the present invention is not particularly limited, and examples thereof include sodium, potassium, calcium, and the like. These may be included alone or in combination of two or more. However, it is preferable that it contains only an alkali metal element in terms of high alkalinity and in particular, when a solid silica raw material is used, the zeolite is likely to be crystallized.

  Examples of the alkali (earth) metal element source (the raw material compound of the alkali (earth) metal element) include hydroxides, bicarbonates, carbonates and the like thereof. These compounds are basic in an aqueous solution state. Specific examples include sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, and calcium carbonate. Among these, alkali metals such as sodium hydroxide and potassium hydroxide Elemental hydroxide has high alkalinity, especially when solid silica raw material is used. By improving the solubility, the silica raw material is sufficiently dissolved, thereby promoting the subsequent crystallization of silica. It is preferable in a certain point.

  These alkali (earth) metal element sources may use only 1 type, and may use 2 or more types together.

<Structure directing agent>
In the present invention, RTH type zeolite can be synthesized without using a structure-directing agent, but a small amount of structure-directing agent may be used as necessary.

  When a structure directing agent is used, the structure directing agent is not particularly limited, but is usually a quaternary alkyl ammonium salt, monoalkylamines, dialkylamines, trialkylamines, diamines, alcohol amines, alcohols. , Ethers, alkylureas, alkylthioureas, cyanoalkanes and the like are used. These may be used alone or in combination of two or more.

  When a structure directing agent is used, the amount used is a small amount below the value described below, but it is expensive in the present invention, and RTH without using a structure directing agent that requires a removal step such as firing after hydrothermal synthesis. It is preferable to synthesize type zeolite in terms of cost and manufacturing process.

<Seed crystal>
In the present invention, a seed crystal may be added to the gel subjected to hydrothermal synthesis. As this seed crystal, a zeolite having a 4-membered ring as a secondary building unit is preferable, and it is particularly preferable to use an RTH type zeolite, particularly an RTH type zeolite having boron as a skeleton. Only one type of seed crystal may be used, or a combination of materials having different structures and compositions may be used. However, from the viewpoint of the production efficiency of the RTH type zeolite by using the seed crystal, it is preferable to use a zeolite having a 4-membered ring as the secondary building unit, preferably only one type of the RTH type zeolite.

<Preparation of aqueous mixture>
An aqueous mixture as a precursor for hydrothermal synthesis is prepared by mixing the silica raw material, an alkali (earth) metal element source, a hetero element source, a structure directing agent used as necessary, and water. The order of mixing is not limited and may be appropriately selected depending on the conditions to be used. Usually, an alkali (earth) metal element source is first dissolved in water, and a hetero element source is mixed therewith. Further, the silica raw material is mixed and stirred. In the present invention, an RTH-type zeolite can be obtained without using a structure-directing agent, but a small amount of a structure-directing agent may be added as necessary. In addition, seed crystals may be added to the gel, and it becomes easier to obtain RTH type zeolite when seed crystals are added.
When a structure directing agent is used, the structure directing agent is preferably added and mixed in a stage where an alkali (earth) metal element source is dissolved in water.
Moreover, when using a seed crystal, it is preferable to add and mix a seed crystal after adding and mixing a silica raw material.
Further, the aqueous mixture only needs to be mixed with each of the above components, and may be in a slurry state or a gel state, or may be in a very diluted slurry state.

<Composition of aqueous mixture>
In the present invention, the preferred composition of the aqueous mixture (slurry or gel) subjected to hydrothermal synthesis is as follows.

As described above, the hetero element preferably includes aluminum, gallium, and boron, and particularly preferably includes boron.
When at least one kind of heteroelement other than boron is present in the gel without boron, the molar ratio of Si / heteroelement in the gel is usually 20 or more, preferably 50 or more, more preferably 100 or more, usually 1000 or less, preferably 700 or less. When only a hetero element other than boron is present in the gel, if the Si / hetero element molar ratio is too small, crystallization hardly occurs, which is not preferable. However, if this value is excessively large, generation of impurities such as quartz may occur, which is not preferable.

  When boron is present alone in the gel as a heteroelement, the molar ratio of Si / boron in the gel is usually 0.1 or more, preferably 0.5 or more, more preferably 1 or more. Moreover, it is 5000 or less normally, Preferably it is 2000 or less, More preferably, it is 1000 or less.

When both a boron and a hetero element other than boron are present in the gel, the preferred content ratio of the hetero element other than boron varies depending on the amount of boron as follows.
When the boron content in the gel is 0.1 or more and less than 1000 in terms of the Si / boron molar ratio in the gel, the content of the other heteroelement is usually 5 in terms of the Si / other heteroelement molar ratio. Above, preferably 15 or more, more preferably 30 or more, usually 1500 or less, preferably 1000 or less.
When the boron content in the gel is 1000 or more and 5000 or less in terms of the Si / boron molar ratio in the gel, the content of the other heteroelement is usually 30 or more in terms of the Si / other heteroelement molar ratio. Preferably it is 50 or more, More preferably, it is 100 or more, Usually 1200 or less, Preferably it is 800 or less.

  In either case, if the content of the hetero element is too small, crystallization is difficult to occur, and if it is too much, crystallization is difficult to occur.

The content of the alkali (earth) metal element in the gel is usually 0.01 or more, preferably 0.1 or more, more preferably 0.15 or more in terms of the molar ratio of alkali (earth) metal element / SiO _2. is there. Moreover, it is 0.45 or less normally, Preferably it is 0.4 or less, More preferably, it is 0.3 or less. If the content of the alkali (earth) metal element in the gel is too much or too little, an RTH type zeolite cannot be synthesized.

The water content in the gel is usually 40 or more, preferably 100 or more, more preferably 200 or more, and usually 400 or less, preferably 250 or less, in terms of the molar ratio of H ₂ O / Si. This is because the crystallization of the RTH type zeolite is promoted more when the water content in the gel is within the above range, and when it is too much, the productivity becomes worse.

In the present invention, the structure directing agent is preferably not used, but when the structure directing agent is used, the molar ratio of the structure directing agent / Si in the gel is usually 0.018 or less, preferably 0.10 or less, more preferably It is preferable to use at a ratio of 0.05 or less.
The smaller the amount of the structure directing agent used, the lower the synthesis cost of the RTH type zeolite, which is preferable. Most preferred is an embodiment in which RTH type zeolite is synthesized without using a structure-directing agent.

In the present invention, seed crystals may be used in combination, and the use of seed crystals facilitates the synthesis of RTH type zeolite.
When seed crystals are used, the amount used is not particularly limited, but is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 2% by weight or more, based on the silica raw material in the gel. It is 40% by weight or less, preferably 20% by weight or less.
This is because if the amount of the seed crystal used is too small, the effect of adding the seed crystal cannot be sufficiently obtained, and if too large, it is disadvantageous in terms of productivity.

  In addition, it is preferable to adjust said aqueous mixture composition suitably according to the kind and quantity of the hetero element to employ | adopt.

<Hydrothermal synthesis>
In the present invention, the above aqueous mixture is subjected to hydrothermal synthesis to produce RTH type zeolite. That is, the above-mentioned aqueous gel is usually heated to 80 ° C. or higher, preferably 90 ° C. or higher, and usually 260 ° C. or lower, preferably 220 ° C. or lower to produce RTH zeolite by hydrothermal synthesis. Hydrothermal synthesis is performed without stirring and / or stirring, and the pressure is autogenous pressure or higher. The time required for the hydrothermal synthesis is usually 1 hour or longer, preferably 5 hours to 30 days.

  The aqueous mixture used for hydrothermal synthesis may contain silica raw materials or organic materials derived from hetero element sources, such as alcohols, and these may be removed by distillation or distillation as necessary. Also good.

The product obtained by hydrothermal synthesis is separated from the reaction solution by filtration, etc., washed with water to remove impurities, and then dried at about 50 to 100 ° C. to obtain the intended RTH type zeolite. be able to.
When RTH-type zeolite is synthesized using a structure-directing agent, calcination and extraction with a solvent are then required to remove the structure-directing agent, but when RTH-type zeolite is synthesized without using a structure-directing agent In such a case, such a structure-directing agent removal process is unnecessary.

  When the RTH type zeolite synthesized in this way is used as a catalyst or the like, it can be converted into a desired ion exchange type by a conventional method according to its use. Usually, when used as a catalyst, conversion to the proton type is often performed, but depending on the application, the trivalent element counter cation element (alkali metal or alkaline earth metal) is sodium, potassium, lithium, etc. Alkaline metal elements different from the original counter cation, alkaline earth metal elements different from the original counter cation such as magnesium, calcium, strontium, rare earth metals such as lanthanum, cerium, iron, cobalt, nickel ruthenium, palladium, The elements may be exchanged for elements from Group 4 to Group 12 of the periodic table, such as platinum, titanium, zirconium, hafnium, chromium, molybdenum, tungsten, thorium, and zinc. Of course, these may coexist.

  EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples. In the following, hydrothermal synthesis was performed under autogenous pressure conditions. In addition, the mother gel composition shown below excludes the seed crystal.

[Synthesis example with boron added to mother gel]
<Example 1>
After 0.22 g of 8N sodium hydroxide solution and 25.0 g of water were mixed, 0.11 g of boric acid was added thereto and stirred, and then 0.42 g of Cab-O-Sil M5 (manufactured by Cabot) was used as a silica raw material. In addition, the mixture was sufficiently stirred.
Furthermore, 2 wt% of RTH type zeolite having boron as a skeleton as a seed crystal was added to Cab-O-Sil M5 and stirred. The composition of the mother gel thus obtained was 1SiO ₂ : 0.25H ₃ BO ₃ : 200H ₂ O: 0.2NaOH.
This mother gel was charged into an autoclave and heated at 170 ° C. for 7 days under a tumbling condition of 20 rpm. The product was filtered, washed with water, and dried at 100 ° C.

According to FIG. 1 showing the XRD pattern of the product (according to CuKα line), a peak peculiar to the RTH structure was observed.
The SEM image of the product is shown in FIG. 2, and rod-like crystals having a large aspect ratio were observed. These crystals have the same shape as when a structure directing agent is used.
FIG. 3 shows the ²⁹ Si-MAS-NMR spectrum. The Q4 peak is caused by the Si species in which all four atoms adjacent to −112 ppm are Si, and one of the four atoms adjacent to −107 ppm. One Q4 peak is observed due to the Si species where one is B and three is Si. Since the Q3 peak indicating Si species having one silanol is not seen, it can be seen that the crystal has almost no defects.
FIG. 4 shows an ¹¹ B-MAS NMR spectrum, and peaks are seen in the Tetrahedral due to boron incorporated into the skeleton and the Trigonal due to boron outside the skeleton. Since the intensity of the Tetrahedral boron peak is smaller than that of the Trigonal peak, it is considered that the amount of boron incorporated into the skeleton is less than the charge ratio of SiO ₂ / B = 4.

[Synthesis example with aluminum and boron added to mother gel]
<Example 2>
0.22 g of 8N sodium hydroxide solution and 25.0 g of water were mixed. To this, 0.11 g of boric acid and 0.012 g of aluminum sulfate anhydride were added and stirred. Then, as a silica raw material, Cab-O-Sil M5 0.42 g was added and sufficiently stirred. Further, RTH type zeolite having 5% by weight of boron as a skeleton relative to the weight of Cab-O-Sil M5 was added as a seed crystal and stirred. The composition of the mother gel thus obtained was 1SiO ₂ : 0.25H ₃ BO ₃ : 0.005Al ₂ (SO ₄ ) ₃ : 200H ₂ O: 0.2 NaOH.
This mother gel was charged into an autoclave and heated at 170 ° C. for 7 days under a tumbling condition of 20 rpm. The product was filtered, washed with water, and dried at 100 ° C.

<Example 3>
The compound was synthesized under the same conditions as in Example 2 except that the molar ratio of sodium hydroxide to silica was doubled. The composition of the mother gel was 1SiO ₂ : 0.25H ₃ BO ₃ : 0.005Al ₂ (SO ₄ ) ₃ : 200H ₂ O: 0.4 NaOH.

<Example 4>
The synthesis was performed under the same conditions as in Example 2 except that the molar ratio of aluminum sulfate to silica was halved. The composition of the mother gel _{1SiO 2: 0.25H 3 BO 3:} 0.0025Al 2 (SO 4) 3: 200H 2 O: was 0.2NaOH.

<Example 5>
The compound was synthesized under the same conditions as in Example 4 except that the molar ratio of sodium hydroxide to silica was doubled. The composition of the mother gel was 1SiO ₂ : 0.25H ₃ BO ₃ : 0.0025Al ₂ (SO ₄ ) ₃ : 200H ₂ O: 0.4NaOH.

According to FIG. 5 showing the XRD pattern (by CuKα line) of the products obtained in Examples 2 to 5, a peak peculiar to the RTH structure was observed.
SEM images of these products are shown in FIGS. 6 to 9, and rod-like crystals having a large aspect ratio were observed. This crystal has the same shape as when the structure-directing agent is used, and is the same as the RTH zeolite of Example 1 containing boron alone in the skeleton.
FIG. 10 shows the ²⁹ Si-MAS-NMR spectrum of the product obtained in Example 2. The Q4 peak attributed to Si species adjacent to four Si atoms in the vicinity of −112 ppm, 3 adjacent to −107 ppm. Q4 peak due to Si species close to one Si atom and one B atom is seen. Since the Q3 peak is not observed, it can be seen that the crystal has almost no defects.
FIG. 11 shows the ¹¹ B-MAS NMR spectrum of the product obtained in Example 2. Two peaks due to Tetrahedral boron and Trigonal boron are observed. The intensity of the Tetrahedral boron peak is smaller than that of the Trigonal peak, and the boron incorporated into the skeleton is considered to be less than the charge ratio of SiO ₂ / B = 4.
FIG. 12 shows the ²⁷ Al-MAS NMR spectrum of the product obtained in Example 2. Since a sharp peak derived from the 4-coordinate in the skeleton can be confirmed, aluminum is incorporated in the skeleton. I understand. On the other hand, since a broad peak derived from the extracoordinate 6-coordination can be confirmed also in the vicinity of 0 ppm, it is understood that a part of Al exists outside the skeleton.

<Example 8>
The synthesis was performed under the same conditions as in Example 2 except that the amount of seed crystals to be added was quadrupled and the molar ratio of aluminum sulfate to silica was doubled. The composition of the mother gel was 1SiO ₂ : 0.25H ₃ BO ₃ : 0.01Al ₂ (SO ₄ ) ₃ : 200H ₂ O: 0.2NaOH.

  According to FIG. 20 which shows the XRD pattern (by CuKα line) of the product, a peak specific to the RTH structure was observed.

[Synthesis example with gallium and boron added to mother gel]
<Example 6>
After mixing 0.22 g of 8N sodium hydroxide solution and 25.0 g of water, 0.11 g of boric acid and 0.014 g of gallium nitrate hydrate (7-9 hydrate) were added and stirred. As a silica raw material, 0.42 g of Cab-O-Sil M5 was added and sufficiently stirred. Further, RTH type zeolite having 2% by weight of boron as a skeleton relative to the weight of Cab-O-Sil M5 was added as a seed crystal and stirred. The composition of the mother gel thus obtained was 1SiO ₂ : 0.25H ₃ BO ₃ : 0.005Ga (NO ₃ ) ₃ : 200H ₂ O: 0.2NaOH.
This mother gel was charged into an autoclave and heated at 170 ° C. for 7 days under a tumbling condition of 20 rpm. The product was filtered, washed with water, and dried at 100 ° C.

According to FIG. 13, which shows the XRD pattern (by CuKα line) of the product, a peak peculiar to the RTH structure was observed.
An SEM image of this product is shown in FIG. 14, and rod-like crystals having a large aspect ratio were observed. This crystal has the same shape as that when the structure-directing agent is used, and has the same peak as the RTH zeolite obtained in Examples 1 to 5.

[Synthesis example without adding seed crystals and adding boron to the mother gel]
<Example 7>
The synthesis was performed under the same conditions as in Example 1 except that the molar ratio of water to silica was halved without adding seed crystals. The composition of the mother gel was 1SiO ₂ : 0.25H ₃ BO ₃ : 100H ₂ O: 0.2NaOH.

According to FIG. 15 showing the XRD pattern of the product (according to CuKα line), although the peak intensity is lower than that of the product obtained in Example 1, a peak peculiar to the RTH structure was observed.
That is, if an alkali metal element is present in the mother gel, an RTH type zeolite can be synthesized without using a structure-directing agent, but a zeolite with higher crystallinity can be obtained with a seed crystal. I understand.

<Comparative Example 1>
The synthesis was attempted under the same conditions as in Example 7 except that the molar ratio of sodium hydroxide to silica was 0. The composition of the mother gel was 1SiO ₂ : 0.25H ₃ BO ₃ : 100H ₂ O: 0NaOH.

  The XRD pattern of the obtained product is shown in FIG. The peak was not confirmed and was amorphous.

<Comparative example 2>
The synthesis was attempted under the same conditions as in Example 7 except that the molar ratio of sodium hydroxide to silica was 2.5 times. The composition of the mother gel was 1SiO ₂ : 0.25H ₃ BO ₃ : 100H ₂ O: 0.5 NaOH.

The XRD pattern of the obtained product is shown in FIG. A peak derived from the RTH structure was not observed, and quartz was generated. That is, even if an alkali metal element is present in the mother gel, the RTH zeolite could not be synthesized if the molar ratio of alkali metal element / SiO ₂ was too large.

<Comparative Example 3>
As a seed crystal, RTH type zeolite having boron as a skeleton was added in an amount of 2% by weight with respect to the weight of Cab-O-Sil M5, and the same as in Example 7 except that the molar ratio of sodium hydroxide to silica was 0. Synthesis was attempted under conditions. The composition of the mother gel was 1SiO ₂ : 0.25H ₃ BO ₃ : 100H ₂ O: 0NaOH.

  The XRD pattern of the obtained product is shown in FIG. The peak was not confirmed and was amorphous. Even if the seed crystal was added, no RTH type zeolite was obtained from the gel containing no alkali metal element.

<Comparative Example 4>
Example 7 except that RTH-type zeolite having boron as a skeleton as a seed crystal was added in an amount of 2% by weight based on the weight of Cab-O-Sil M5, and the molar ratio of sodium hydroxide to silica was 2.5 times. The synthesis was attempted under the same conditions. The composition of the mother gel was 1SiO ₂ : 0.25H ₃ BO ₃ : 100H ₂ O: 0.5 NaOH.

  The XRD pattern of the obtained product is shown in FIG. A peak derived from the RTH structure was not observed, and quartz was generated. That is, when the ratio of alkali metal element / Si was too large, RTH type zeolite could not be obtained even if seed crystals existed.

  Table 1 summarizes the composition of the mother gel and the presence or absence of seed crystals in Examples 1 to 8 and Comparative Examples 1 to 4.

Claims (9)

  A silica raw material, an alkali metal element and / or an alkaline earth metal element, and oxygen, silicon, an alkali metal element and at least one hetero element other than the alkaline earth metal element, the alkali metal element and / or The molar ratio of the alkaline earth metal element to silica is in the range of 0.01 to 0.45 and does not contain a structure directing agent, or the structure directing agent has a molar ratio of structure directing agent / Si of 0.018 or less A method for producing an RTH type zeolite, comprising hydrothermally synthesizing an aqueous mixture.   The method for producing an RTH type zeolite according to claim 1, wherein the aqueous mixture does not contain a structure-directing agent.   The method for producing an RTH type zeolite according to claim 1 or 2, wherein only the alkali metal element is contained as the alkali metal element and / or alkaline earth metal element.   The method for producing an RTH type zeolite according to any one of claims 1 to 3, wherein the alkali metal element is sodium.   The method for producing an RTH type zeolite according to any one of claims 1 to 4, wherein zeolite is added as seed crystals to the aqueous mixture and hydrothermal synthesis is performed.   6. The method for producing an RTH type zeolite according to claim 5, wherein the seed crystal is a zeolite having a 4-membered ring as a secondary building unit.   The method for producing an RTH type zeolite according to claim 6, wherein the zeolite as the seed crystal is an RTH type zeolite. The method for producing an RTH type zeolite according to any one of claims 1 to 7, wherein a ratio of water in the aqueous mixture is 40 or more in terms of H ₂ O / Si molar ratio.   The method for producing an RTH type zeolite according to any one of claims 1 to 8, wherein the hetero element is at least one element selected from the group consisting of aluminum, gallium, and boron.

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