JP2009269788A - Method of synthesizing hollow zeolite, hollow zeolite and drug support comprising hollow zeolite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of synthesizing hollow zeolite having no pore except pores existing in a zeolite crystal and having hollow parts free from the variation of the size therein. <P>SOLUTION: The hollow parts are formed in the core shell zeolite by forming core zeolite having a metal, growing the zeolite crystal containing no metal around the formed core zeolite to form the core/shell zeolite, removing the metal from the formed core/shell zeolite and bringing it into contact with a silica decomposing agent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for synthesizing hollow zeolite composed only of pores of a crystal structure of zeolite crystals, a hollow zeolite synthesized by the synthesis method, and a drug carrier comprising the hollow zeolite.

A porous body is a solid having pores, and the size of the pores is defined by IUPAC (International Union of Pure and Applied Chemistry). The pores of 2 to 50 nm are classified as mesopores, and the pores of 50 nm or more are classified as macropores. The porous body has a high surface area of several tens to several thousand m ² / g due to its pore structure.

  Examples of the porous material include zeolite and ordered mesoporous silica. Zeolite is a crystalline oxide in which silicon and aluminum are bonded through oxygen. This zeolite has regular micropores resulting from the crystal structure, and the regular mesoporous material is widely known as a porous material having mesopores of uniform size.

  The hollow porous body has a structure having a porous shell and a hollow inside, and various materials can be included by the hollow inside, and the porous shell allows the internal And the outside are connected by pores, and the substance can move through the pores. The hollow porous body has such a characteristic structure, and studies on the application of various hollow porous bodies using this structural feature have been conducted.

  For example, a capsule is formed using a hollow porous body having this characteristic structure, and a substance such as a drug is included in the capsule, that is, inside the hollow of the porous body, and the substance is diffused through the pores of the capsule. Therefore, application as a sustained-release capsule that gradually releases the drug out of the capsule is expected. Further, it is expected to be effective as a molecular sieve in which a catalyst larger than the pores of the shell of the porous body is confined in the hollow and only those that can pass through the pores are selectively generated. Furthermore, when a homogeneous catalyst is confined inside, it is considered that the catalyst can be easily separated.

  A typical hollow porous body expected to be used in many ways is hollow silica. Hollow silica is a particle whose shell is porous silica and hollow inside, and is characterized in that macropores and mesopores are formed in the shell in which silica fine particles are gathered.

  At present, the following method is used as a commonly used method for synthesizing hollow silica. For example, polystyrene beads are used as a template, and silica is grown on the outside of the template so as to cover the periphery of the beads. Thereafter, hollow silica is synthesized by removing the polystyrene beads. FIG. 17A is an SEM image of hollow silica particles synthesized by this synthesis method.

  As another synthesis method, there is a method of synthesizing hollow particles by covering the outside of polystyrene beads used as a template with regular mesoporous silica. FIG. 17B is an SEM image of hollow silica particles synthesized using regular mesoporous silica.

  According to these synthesis methods, a porous body having a hollow inside can be generated. However, in the hollow particles shown in FIG. 17A, the shell is formed of a collection of silica particles. There will be non-uniform macropores. In the hollow silica shown in FIG. 17B, the shell has three-dimensionally formed mesopores and non-uniform macropores between the silica particles. Thus, in the hollow particles synthesized by the above-described method, macropores and mesopores that are non-uniform and have large pore diameters are formed in the shell, so that the pores are significantly larger than the molecular size. As a result, the effect as a molecular sieve as described above, the sustained release effect and the like cannot be sufficiently exhibited.

  Another typical hollow porous material is hollow zeolite. The hollow zeolite is a zeolite having pores in the angstrom order at the molecular level smaller than the above-described hollow silica in the shell and having cavities inside. The hollow zeolite having such micropores is also expected to be applied to a shape-selective catalyst, a diffusion control capsule, and the like because of its structural characteristics.

  As a method for producing hollow zeolite, the following methods have been reported so far. For example, a method of forming hollow zeolite particles by subjecting zeolite crystals to alkali treatment. Usually, in zeolite crystals, the concentration of aluminum in the crystal is low and the concentration of silica is high. When such a zeolite crystal is subjected to alkali treatment, the inside of the crystal having a high silica concentration is preferentially dissolved, and as a result, hollow particles are formed.

  As another method for synthesizing hollow silica, a method is proposed in which spherical polystyrene particles such as polystyrene beads are used as a template, zeolite particles are grown outside the template, and then the template is removed to synthesize. (For example, see Non-Patent Documents 1 to 3.)

X.D.Wang et al., Chem. Commun., 2000, 2161. V. Valtchev et al., Micropor. Mesopor. Mater., 43 (2000) 41. S.P.Naik et al., Chem. Mater., 15 (2003) 787.

  The hollow zeolite produced by the synthesis method described above has micropores in the shell and has cavities formed inside, so it can be used for various purposes by utilizing its structural features. Has been.

  However, the above-described conventional synthesis method has the following problems. That is, in the above-described method of synthesizing hollow zeolite by alkali treatment of zeolite crystals, the silica is preferentially melted by alkali treatment from the portion having a high silica concentration in the crystal. Therefore, a hollow with a variation is formed. In addition, this alkali treatment forms mesopores having a large pore diameter, and the above-described effect as a molecular sieve and efficient sustained release control of the drug cannot be fully exhibited. 18A and 18B are an SEM image and a TEM image of hollow zeolite particles synthesized by a synthesis method using an alkali treatment.

  Also, in the synthesis method using spherical polystyrene particles, the shell of the hollow particles is composed of zeolite microcrystals, so that they are formed as gaps between the aggregated crystals separately from the micropores of the crystals themselves. As a result, mesopores are generated, and as described above, the effect as a sufficient molecular sieve, the sustained release effect, and the like cannot be exhibited. FIGS. 18C and 18D are SEM images of hollow zeolite particles synthesized using spherical polystyrene particles as a template.

  The present invention has been proposed in view of such circumstances, and a method for synthesizing a hollow zeolite that has no voids other than the pores present in the zeolite crystal and has a hollow with no variation in size. The purpose is to provide.

  As a result of intensive research from various viewpoints, the present inventors have formed a core-shell zeolite having a core containing a metal that can be dissolved by an acidic solution, and selectively decomposed and removed the core part. Thus, the inventors have found that a hollow zeolite can be stably formed and a hollow zeolite with few defects can be formed, and the present invention has been completed.

  That is, in the method for synthesizing a hollow zeolite according to the present invention, a core zeolite forming step for synthesizing a metal-containing core zeolite, and a zeolite crystal is grown around the core zeolite formed in the core zeolite forming step, A core / shell zeolite forming step for forming a core / shell zeolite, a metal removing step for removing the metal from the core / shell zeolite formed in the core / shell zeolite forming step, and a silica decomposing agent. A hollow formation step of decomposing the core zeolite from which the metal has been removed in the metal removal step to form a hollow in the core-shell zeolite.

  The hollow zeolite according to the present invention is synthesized by the above-described method for synthesizing hollow zeolite, and the pores of the hollow zeolite are composed only of pores derived from the pores of the crystal structure of the zeolite crystal.

  The drug carrier according to the present invention comprises a hollow zeolite synthesized by the above-described method for synthesizing hollow zeolite, and the pores of the hollow zeolite are only pores derived from the pores of the crystal structure of the zeolite crystal. Consists of.

  According to the method for synthesizing hollow zeolite according to the present invention, the core portion of the core-shell zeolite is selectively decomposed and removed to form a hollow, thus enabling the formation of a hollow having a stable shape, It is possible to synthesize a hollow zeolite with few defects that does not have pores having a larger pore diameter than the pores inherent in the crystal structure.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic view schematically showing a procedure of a method for synthesizing a hollow zeolite according to the present embodiment. As shown in FIG. 1, the method for synthesizing a hollow zeolite according to the present embodiment includes a core zeolite forming step for synthesizing a core zeolite containing a metal, and a core zeolite formed in the core zeolite forming step. A core / shell zeolite forming step for growing a zeolite crystal to form a core / shell zeolite; a metal removing step for removing the metal from the core / shell zeolite formed in the core / shell zeolite forming step; A hollow forming step of contacting the cracking agent and decomposing the core zeolite from which the metal has been removed in the metal removing step to form a hollow in the core-shell zeolite.

In the following description, an example of synthesizing ^* BEA type hollow zeolite based on ^* BEA type zeolite as zeolite will be described for specific and clear explanation, but the synthesis method according to the present embodiment will be described. The applicable zeolite is not limited to this ^* BEA type zeolite, and other various zeolites can be used to synthesize hollow zeolite. In selecting a zeolite, for example, when a drug is supported on a synthesized hollow zeolite and used as a drug carrier such as a sustained-release capsule, the molecular size of a substance such as a drug included and supported in the hollow is determined. Therefore, it is preferable to select appropriately. Details will be described later.

Here, ^* BEA type zeolite used in the present embodiment will be described. ^* BEA zeolite, composition formula _{M n Al n Si 64-n} O 128: represented by (n <7, M monovalent cation), a zigzag shape composed of 12-membered ring 5.5 × 5.5 Å Zeolite having two types of micropores having relatively large pore diameters, and a linear pore consisting of 7.6 × 6.4 angstroms of a 12-membered ring. This ^* BEA-type zeolite has two types of micropores with relatively large pore diameters in a three-dimensional manner, so a relatively large molecular substance adsorbed inside the pores via the pores. Can be efficiently diffused in multiple directions. In the following, including this point, the description using the ^* BEA type zeolite will be continued.

<Formation of core>
In the method for synthesizing hollow zeolite according to the present embodiment, first, a zeolite core (core zeolite) is formed. Specifically, in the present embodiment, when the core zeolite is formed, the core zeolite is formed by containing a metal together with a silicon (Si) source constituting the zeolite.

As the metal contained in the formation of the core zeolite, it is preferable to use a metal that can be dissolved by an acid. That is, it is preferable to use a metal having a higher ionization tendency than hydrogen (H). Specifically, for example, a metal such as aluminum (Al), iron (Fe), boron (B), or zinc (Zn) is used. be able to. More specifically, for example, aluminum nitrate (Al (NO ₃ ) ₃ ) or the like is contained as a metal source to form a core zeolite.

As the metal content, for example, when Al (NO ₃ ) ₃ or the like is used as a metal source, the amount of the standard gel is Al (NO ₃ ) in terms of the molar ratio with hydrogen fluoride (HF) described later. ₃ : It is preferable to contain so that it may become a ratio of HF = 1: 1. When the metal is contained at this ratio, the formed core zeolites do not aggregate with each other, and a uniform core zeolite having a crystalline form can be formed.

  As described above, in the method for synthesizing the hollow zeolite according to the present embodiment, the metal that can be dissolved in the acidic solution is contained together with the Si source constituting the zeolite. Therefore, the core zeolite containing the metal is contained. It is possible to intentionally form a core zeolite with many defects by forming the metal and dissolving and removing the metal in a later step. Furthermore, by forming a core part with many defects, the core part can be selectively decomposed and removed to form a hollow, so that a hollow zeolite having a hollow with a stable shape can be formed. Details will be described later.

  Examples of the Si source that can be used for forming the core zeolite include tetraethoxysilane, tetrabutoxysilane, tetrapropoxysilane, triethoxymethoxysilane, trimethoxyethoxysilane, diethoxydimethoxysilane, and dimethoxydiethoxysilane. Various alkoxysilanes, sodium silicate, water glass, colloidal silica, and the like can be used, and are not particularly limited.

  Further, in the method for synthesizing hollow zeolite according to the present embodiment, it is preferable to form a core zeolite by containing a fluorine compound such as hydrogen fluoride (HF). In this hollow zeolite synthesis method, after the formation of the core zeolite, the zeolite crystals constituting the shell are grown around the core to form the core-shell zeolite. There is no pore other than the pores inherent in the structure (no defects), and it is necessary to have only micropores derived from zeolite crystals. In this case, when there are many defects in the core zeolite, if a shell is formed by growing a crystal around the core, the shell is affected by the defects in the core, resulting in many defects (crystal structure). Macro pores other than the micro pores of the body are generated). Therefore, in the method for synthesizing a hollow zeolite according to the present embodiment, HF is contained when forming the core zeolite. Thus, a zeolite with almost no defects can be formed by synthesizing zeolite by containing HF.

In addition, as a fluorine compound which can be contained in formation of the core zeolite with few defects, it is not restricted to the above-mentioned HF. That is, in addition to HF, a fluorine compound such as ammonium fluoride (NH ₄ F) can be used. It is also possible to form a defect-free zeolite by including F in the structure directing agent to be contained for forming the desired zeolite described later. For example, a core zeolite having almost no defects can be formed by using tetraethylammonium fluoride (TEAF) instead of tetraethylammonium hydroxide (TEAOH) described later. Below, the description continues about the synthesis example which specifically forms a zeolite using HF.

In addition, in the method for synthesizing hollow zeolite according to the present embodiment, a structure-defining agent that defines the structure of the zeolite is included in addition to the above-described containing elements. The synthesis method can be applied to various zeolites, and a core zeolite composed of the desired zeolite can be formed by containing a structure-directing agent that serves as a template for forming a desired zeolite crystal. ^{Specifically,} * the case of forming the core zeolite consisting of BEA zeolite, by including tetraethylammonium hydroxide and (TEAOH) as a structure-directing agent, for example, tetraethoxysilane (TEOS) as an Si ^{source, *} A BEA type zeolite can be formed.

The selection of the type of zeolite can be determined according to the use of the hollow zeolite to be synthesized. For example, when a drug is supported in a hollow zeolite synthesized by a synthesis method that will be described in detail below and used as a drug carrier as a sustained-release capsule, the molecule of the drug to be supported It is preferable to determine the type of zeolite according to the size. As is well known, zeolite can be roughly classified according to the size of its pores. Specifically, in general, 8 or less silicon constituting the zeolite pores are referred to as small pores, 10 as medium pores, 12 as large pores, and 14 or more as super-large pores for convenience. The zeolite can be classified based on the pore size. At this time, for example, when a hollow zeolite is synthesized with ^* BEA type zeolite having large pores and a drug with a small molecule is to be supported on the ^* BEA type hollow zeolite, the drug is easily finely divided into hollow zeolite. You can pass through the hole. As a result, the sustained release effect of the drug cannot be expected sufficiently. Therefore, when using, for example, a hollow zeolite synthesized as a sustained-release capsule, etc., considering the molecular size of the drug to be supported, the desired sustained-release time of the drug is set. It is preferable to determine the type of zeolite in consideration.

As described above, hydrothermal synthesis is performed by a known method using at least the Si source, the metal source, the fluorine compound such as HF, and the structure directing agent described above. Specifically, the hydrothermal synthesis includes, for example, a Si source such as TEAOH, a metal source such as Al (NO ₃ ) ₃ , ^* TEOS that is a structure directing agent that forms BEA type zeolite, and HF. The synthesis solution is put into a sealable container such as an autoclave, and is synthesized by setting an appropriate temperature and time (for example, 175 hours under a temperature condition of 150 ° C.) to form a core zeolite. In addition, after hydrothermal synthesis, it filters and wash | cleans by a well-known method, It bakes in a dry air stream (for example, 550 degreeC temperature conditions for 6 hours).

  As described above, in the method for synthesizing a hollow zeolite according to the present embodiment, a metal that can be dissolved by an acidic solution such as Al is contained to form a core zeolite, and the metal is contained in the process described later. Defects are formed in the formed portions. This makes it possible to form defects only in the core part that specifically contains a metal such as Al, and to selectively decompose and remove the defect parts to form a hollow with a stable shape. I have to.

In the following description, description will be continued with respect to an example in which Al is used as the metal contained in the core zeolite synthesis described above and Al (NO ₃ ) ₃ is used as the metal source.

<Formation of shell (crystal growth)>
When a core zeolite containing a metal such as Al is formed by the above-described method, a shell of zeolite crystals is then formed around the core zeolite to form a core-shell zeolite.

  Specifically, unlike the case of forming the core zeolite, pure zeolite crystals are grown from a Si source without containing a metal such as Al. In this way, unlike the core part, a metal-containing core is obtained by growing pure and defect-free zeolite crystals with a Si source without containing a metal that can be dissolved by an acidic solution such as Al. I try to increase the specificity of the part. And in the process mentioned later, a hollow zeolite is synthesize | combined by selectively decomposing and removing only a core part.

In the formation of the shell, it is preferable to form a zeolite constituting a shell having no defects by containing a fluorine compound such as HF, as in the formation of the core zeolite. By containing a fluorine compound such as HF and forming a shell composed of zeolite crystals with almost no defects, the pores connecting the inside and the outside of the synthesized hollow zeolite are only micropores inherent in the zeolite crystal structure. Thus, the effect as a molecular sieve and the release of a drug impregnated and supported in the hollow interior can be controlled efficiently and easily. In the formation of the shell, as in the formation of the core zeolite described above, the fluorine compound to be contained is not limited to HF, and a fluorine compound such as ammonium fluoride (NH ₄ F) can be used. Moreover, it is possible to form a shell without defects by including F in the structure directing agent to be contained in order to form the desired zeolite described later.

  As a specific core / shell zeolite formation method (zeolite crystal growth method), a core formed in the previous step by adding HF to a container containing a Si source and a structure-directing agent and adjusting the gel ratio. Zeolite crystals are grown around the core zeolite by adding zeolite and performing hydrothermal synthesis treatment at a temperature condition of 140 ° C. for 110 hours, for example. Needless to say, the operation method is not limited to the above-described operation method, and it is needless to say that temperature conditions, processing time, and the like can be changed as appropriate.

<Removal of metal (Al) (dealuminization treatment)>
When the core-shell zeolite is formed by the above-described method, next, Al contained in the core portion of the core-shell zeolite is dissolved and removed. Specifically, by dissolving and removing Al contained in the core portion with an acidic solution, pores having a pore diameter larger than that of the micropores are formed in the portion where aluminum is contained, that is, defects are formed. In this way, by forming defects in the core part of the core-shell zeolite, it is possible to selectively decompose and remove the core part to form a hollow in the process described later. Hereinafter, the dealumination removal process will be specifically described.

  There is no restriction | limiting in particular as an acidic solution which dissolves Al, Various acidic solutions, such as hydrochloric acid, nitric acid, a sulfuric acid, can be used. However, these acidic solutions are preferably made hydrophobic by dissolving them in an organic solvent such as ethanol, for example. The reason for making them hydrophobic will be described below.

  In general, a zeolite having many defects, that is, a zeolite having pores having a pore diameter larger than that of micropores has many silanol groups (Si-OH), and the zeolite having many defects due to the silanol groups. Indicates hydrophilicity. On the other hand, in the case of a zeolite having almost no defects, silanol groups are hardly formed, and thus it exhibits hydrophobicity. As described above, in this embodiment, the shell of the core-shell zeolite formed by growing zeolitic crystals containing HF has pores other than the micropores inherently possessed by the zeolite crystal structure. It is composed of zeolite with few defects and few defects. Therefore, the surface of the core-shell zeolite in the present embodiment is hydrophobic. On the other hand, although the core part formed by containing Al is formed using HF, since it is formed by containing Al, an acidic OH group is formed, which is more hydrophilic than the shell side. Yes. At this time, even if Al is dissolved and removed with an aqueous solution, since the zeolite surface is composed of hydrophobicity, the solution cannot be penetrated to the core portion showing hydrophilicity, and the core portion is sufficiently absorbed. The contained Al cannot be removed.

  Therefore, in the present embodiment, an acidic solution for dissolving and removing Al is dissolved in an organic solvent such as ethanol, and the mixed solution is slightly hydrophobic, so that acidic mixing is performed up to the core portion showing hydrophilicity. The solution is allowed to penetrate. As a result, Al is dissolved and removed by the acidic solution that has penetrated into the core portion, and a large defect (cavity) is formed in the portion containing Al in the core portion.

  As this dealumination removal treatment, for example, a mixed solution of hydrochloric acid and ethanol is prepared, and this mixed solution is added to zeolite and stirred overnight at a temperature of 80 ° C. Dissolve and remove. Needless to say, the acidic solution, temperature conditions, treatment time, and the like are not limited to these, and can be changed as appropriate.

<Internal removal>
When Al, which is a metal contained in the core portion, is dissolved and removed by an acidic solution by the above-described method, the inside of the zeolite, which has many defects, is decomposed and removed to form a hollow. That is, the core part of the core-shell zeolite having many defects due to dealumination treatment is decomposed by bringing it into contact with a silica decomposing agent to synthesize a hollow zeolite in which the core part is decomposed to become hollow.

  In the hollow zeolite synthesis method according to the present embodiment, in this internal removal step, the alkali metal salt is impregnated and supported on the zeolite as a decomposition catalyst, for example, dimethyl carbonate (DMC) is contacted and reacted as a silica decomposition agent. To decompose and remove the core part of the core-shell zeolite to form a hollow. The following equation is a reaction equation when the core portion is decomposed and removed using DMC.

As shown in this reaction formula, in this internal removal reaction, silica constituting the core zeolite and DMC react to generate tetramethoxysilane (Si (OMe) ₄ ) and carbon dioxide (CO ₂ ). It is a reaction. In this way, a hollow having a stable shape can be easily formed by decomposing and removing the silica in the core portion constituting the inside of the zeolite. In addition, what can be used as a silica decomposing agent is not limited to the above-mentioned DMC, and diethyl carbonate, trimethoxymethane, and the like can be used as a silica decomposing agent. The description will be continued by taking the case of using as an example.

  By the way, in order to decompose and remove only the silica constituting the core part of the core-shell zeolite to form a hollow, DMC must be selectively reacted with the core part. Therefore, in the method for synthesizing the hollow zeolite according to the present embodiment, the DMC selectively supports only the silica in the core part by selectively supporting the alkali metal salt, which is a silica decomposition catalyst, on the core part having many defects. I try to break it down.

  More specifically, as described above, generally, a zeolite having many defects, that is, a zeolite having a pore having a pore diameter larger than that of a micropore has a large number of silanol groups (Si-OH), This silanol group exhibits hydrophilicity. On the other hand, in the case of zeolite having almost no defects, silanol groups are hardly formed, and thus it exhibits hydrophobicity. In the present embodiment, the dealumination process is performed in the previous step to remove the aluminum contained in the core part. Therefore, the core part has a defect having a gap larger than the micropores. Many zeolites have become hydrophilic. On the other hand, since the shell part of the core-shell zeolite is composed of zeolite having almost no defects, it exhibits hydrophobicity. In the present embodiment, as described above, the core portion to be decomposed and removed by DMC is selectively made hydrophilic and has a different property from the shell portion. Furthermore, in the present embodiment, the silica decomposition catalyst made of an alkali metal salt used in this internal removal step is dissolved in an organic solvent such as ethanol to form a slightly hydrophobic mixed solution.

  In the present embodiment, in this way, the core part of the core-shell zeolite is made hydrophilic, the shell part is made hydrophobic, and an alkali metal salt used as a silica decomposition catalyst is mixed with a mixed solution showing a little hydrophobicity. Thus, the mixed solution of the silica decomposition catalyst is selectively supported on the core portion. In addition, since the mixed solution of the alkali metal salt that is the silica decomposition catalyst is impregnated and supported only in the core portion, the DMC that is the silica decomposing agent acts only on the core portion and only the silica constituting the zeolite of the core portion. The shell portion can be maintained in a form without being decomposed by the DMC.

  The alkali metal salt that can also be used as a silica decomposition catalyst is not particularly limited. For example, various alkalis such as sodium acetate, potassium acetate, lithium acetate, cesium acetate, rubidium acetate, and sodium oxalate can be used. Metal salts can be used.

  As described above, in the method for synthesizing the hollow zeolite according to the present embodiment, the silica decomposition catalyst made of an alkali metal salt is dissolved in an organic solvent to form a mixed solution showing a little hydrophobicity, thereby mixing the decomposition catalyst. The solution is selectively supported only on the core portion showing hydrophilicity. Then, after supporting the silica decomposition catalyst, only the core portion having many defects is selectively decomposed and removed by DMC by contacting DMC. As a result, the core part possessed by the pores other than the micropores is selectively removed, and a hollow having a stable shape is formed. The hollow zeolite thus formed originally has a zeolite. It becomes possible to synthesize a defect-free hollow zeolite having no pores other than micropores derived from the crystal structure.

  As described above, according to the method for synthesizing hollow zeolite according to the present embodiment, the zeolite is composed of only micropores inherently possessed by the crystal structure of the zeolite crystal without any defects, and is stable inside. A hollow zeolite having a hollow shape can be synthesized.

  Moreover, according to the hollow zeolite particles having a hollow with a stable shape and forming almost no large pores due to the gap between the zeolite particles, it is possible to include chemical substances in the hollow. Thus, it is possible to apply as a sustained release capsule for controlling the release of the substance to the outside.

  FIG. 2 is a schematic diagram for explaining the sustained release effect when hollow zeolite is used as a capsule for sustained drug release. In the sustained-release capsule containing this drug, the drug confined inside the hollow zeolite capsule can be diffused in the pores and gradually released to the outside of the hollow zeolite.

  In order to exhibit such a sustained release effect, it is necessary that capsules made of hollow zeolite have micropores having a substantially uniform pore diameter. In other words, if the crystal structure of the zeolite crystal has pores with a large pore diameter other than the micropores inherently possessed or the pores are non-uniform, the drug trapped inside However, it is easy to release to the outside through the large pores, and a sufficient sustained release effect cannot be expected. In addition, when the pore diameter is not uniform, the sustained release time of the drug cannot be controlled efficiently, and a sufficient sustained release effect cannot be realized.

  According to the method for synthesizing a hollow zeolite according to the present embodiment, as described above, it is possible to form a hollow having a stable shape, and a hollow zeolite having only micropores having a uniform pore diameter. Can be synthesized. Therefore, by using the hollow zeolite in the present embodiment, the drug or the like can be sufficiently impregnated and supported in the hollow, and more efficient drug slowdown can be achieved through pores consisting of only uniform micropores. Drug sustained-release capsules can be produced as drug carriers that allow controlled release.

In addition, in this specification, although the method of synthesize | combining ^* BEA type | mold hollow zeolite as a zeolite was demonstrated, as a zeolite, it is not restricted to these. That is, ^* in addition to the BEA type as zeolite having a large pore, based for example AFI type, zeolite of FAU type, etc., can be synthesized hollow zeolite. Further, not only zeolite having large pores, but also zeolite having medium pores such as MFI type, MEL type and HEU type, and zeolite having ultra large pores such as CFI type and DON type. However, it is possible to apply the present invention. As described above, in selecting the type of zeolite, for example, when applied as a drug sustained-release capsule as described above, depending on the size of the drug molecule to be impregnated and supported in the hollow, It is preferable to select appropriately.

  In addition, the present invention is not limited to the above-described embodiment, and an invention appropriately modified within the scope not changing the gist of the present invention is also included in the present invention.

[ ^* Synthesis of BEA type hollow zeolite]
Example 1
^* BEA type hollow zeolite was synthesized using the method of synthesizing hollow zeolite according to the present embodiment. In the synthesis measurement, the form of the zeolite particles was observed by using a scanning electron microscope (SEM: Scanning Electron Microscope; JSM-5200 manufactured by JEOL Ltd.) and measuring at an acceleration voltage of 20 kV. Further, Rigaku MiniFlex (manufactured by Rigaku Corporation) was used, and X-ray diffraction (XRD) measurement was also performed at the same time. The X-ray source was Cu-Kα ray (λ = 1.5418 angstrom), and the measurement was performed at 30 kV and 50 mA.

<Formation of core>
・ Operation method: An aqueous solution (25.1 g) of tetraethylammonium hydroxide (TEAOH; manufactured by Sigma-Aldrich Co., Ltd. (25.1 g)) is added to a 500 ml Teflon (registered trademark) container, and aluminum nitrate nonahydrate (Kanto Chemical Co., Ltd.) is stirred. (98.0%)) (1.58 g) was added. Thereafter, after aluminum nitrate nonahydrate was completely dissolved, tetraethoxysilane (TEOS; manufactured by Shin-Etsu Silicone) (20.7 g) was added dropwise. And after stirring the obtained solution at room temperature for 1.5 hours, the produced | generated ethanol was removed using the rotary evaporator, and the gel ratio was adjusted after that. Furthermore, hydrogen fluoride (HF; manufactured by Kanto Chemical Co., Inc. (46%)) (gel ratio TEOS: TEAOH: aluminum (Al): HF: H ₂ O = 1: 0.6: 0.04: 0. 6: 7.5) was added, and hydrothermal synthesis was performed using an autoclave at a temperature of 150 ° C. over 175 hours. Then, it is filtered and washed, and calcined in a dry air stream (2 hours at 200 ° C. for 6 hours and 550 ° C. for 6 hours (heating rate 1 ° C./min)) to form the core zeolite. It was.

- form confirmation and X-ray diffraction measurement FIG 3 by SEM image, ^* after BEA type zeolite of the core synthetic forms of particles (prior to crystal growth) (FIG. 3 (A)) and the particle size distribution (FIG. 3 (B )). As shown in the SEM image of FIG. 3 (A), it was observed to have a decahedral structure peculiar to ^* BEA type zeolite. Further, as can be seen from the graph of the XRD pattern of the synthesized core zeolite shown in FIG. 4, only peaks peculiar to ^* BEA type zeolite were observed in the synthesized core zeolite.

From these facts, it was confirmed that in the synthesis of this core, only ^* BEA type zeolite was produced. Further, as shown in the particle size distribution of FIG. 3B derived from this SEM image, it was confirmed that zeolite particles having a particle size of about 3 to 6 μm were produced.

<Synthesis of shell (crystal growth)>
-Operation method After generating the core, TEAOH was added to a 500 ml Teflon (registered trademark) container, and TEOS was added dropwise little by little while stirring. After stirring the obtained solution at room temperature for 1.5 hours, the produced ethanol was removed using a rotary evaporator, and then the gel ratio was adjusted. After adding HF dropwise, the synthesized core zeolite was added (gel ratio TEOS: TEAOH: Si (core): HF: H ₂ O = 1: 0.6: 1: 0.6: 7.5). And hydrothermal synthesis was performed over a period of 110 hours under a temperature condition of 140 ° C. Thereafter, it is calcined in a dry air flow (2 hours at a temperature of 200 ° C., 6 hours at a temperature of 550 ° C. (temperature increase rate: 1 ° C./min)) to grow a zeolite crystal, and a core-shell zeolite Formed.

-Morphological confirmation and X-ray diffraction measurement by SEM image Fig. 5 shows the particle morphology (Fig. 5 (A)) and particle size distribution (Fig. 5) after crystal growth (before internal decomposition treatment with dimethyl carbonate (DMC)). It is a figure which shows (B)). As shown in the SEM image of FIG. 5 (A), it was clearly observed that even after crystal growth, it has a decahedral structure peculiar to ^* BEA type zeolite. Further, as can be seen from the graph of the XRD pattern shown in FIG. 6, only a peak peculiar to the ^* BEA type was observed in the synthesized zeolite.

From these facts, it was confirmed that ^* BEA-type zeolite crystals grew and formed shells around the ^* BEA-type core zeolite. In addition, as shown in the particle size distribution of FIG. 5B, the particle size distribution after crystal growth is about 4 to 7 μm except for the fine particles generated during crystal growth, and it is in the gel used for crystal growth. It was found that almost all of silicon was used for crystal growth.

Furthermore, when an experiment was conducted in which the crystal-grown ^* BEA-type zeolite particles were placed in water, the particles floated on the water surface. This indicates that the synthesized ^* BEA type zeolite particles are hydrophobic and have few defects. More specifically, in the process after crystal growth, in order to remove the core containing aluminum having many defects and to produce a hollow zeolite having almost no defects, it is essential that the shell has few defects. When there are many defects, it means that there are many silanol groups, and as a result, the zeolite shows hydrophilicity, so by putting the synthesized zeolite particles in water and checking the sedimentation rate, the shell with few defects It is possible to determine whether or not As described above, the zeolite particles synthesized by crystal growth by the method of Example 1 floated on the surface of the water, so it was concluded that hydrophilic particles were not shown and defects-free particles could be formed. it can.

<Dealuminization treatment>
·Method of operation
^* BEA-type zeolite formed by crystal growth ^* BEA-type core-shell zeolite was added with 7 ml of 6M hydrochloric acid and 3 ml of ethanol and stirred overnight at a temperature of 80 ° C., and the aluminum contained in the core part Was removed. Then, it is filtered, washed, and finally fired in a stream of dry air (2 hours at a temperature of 200 ° C. for 6 hours at a temperature of 550 ° C. (temperature increase rate: 1 ° C./min)) and contains aluminum. No ^* BEA type core-shell zeolite was formed.

-Aluminum content measurement and X-ray diffraction measurement The following Table 1 is a table | surface which shows the measurement result of the aluminum content before and behind this aluminum removal process.

  As shown in Table 1, since the ratio of silicon and aluminum was 495/1 after dealumination treatment, it was found that almost all aluminum could be removed by dealumination treatment. .

  Further, as clearly seen from the XRD pattern graph of FIG. 7, there was no change in the pattern before and after dealumination, so that the treatment did not change the structure of the core-shell zeolite. It was confirmed that can be removed.

  It should be noted that the dealumination treatment eliminated the aluminum in the zeolite, and therefore, the core / shell zeolite was composed of zeolite with many defects, and thus is considered to be hydrophilic.

<Internal removal (DMC treatment)>
-Operation method 1 wt% sodium acetate (Wako Co., Ltd. (98.5%)) is dissolved in ethanol (Wako Co., Ltd. (99.5%)) with respect to the core-shell zeolite after dealumination treatment. The mixed solution was impregnated and supported on zeolite. Then, the zeolite carrying the mixed solution of sodium acetate was filled in a quartz reactor, and pretreatment was performed at 380 ° C. for 1 hour under a helium stream. Then, dimethyl carbonate (DMC: manufactured by Kanto Chemical Co., Ltd. (special grade> 98.0%)) was supplied at 80 kPa and 64 mmol / h at 380 ° C. to perform a decomposition reaction. The decomposition rate was calculated by integrating the decomposition rate of tetraethoxysilane, which is a decomposition product (see the graphs in FIGS. 8A and 8B). The supply of dimethyl carbonate was stopped when the decomposition rate of the zeolite was 50%.

-Morphological confirmation by SEM image and X-ray diffraction measurement FIG. 9 is a diagram showing the morphology (FIG. 9A) and particle size distribution (FIG. 9B) of particles after DMC treatment. As shown in the SEM image of FIG. 9 (A), it was observed that the zeolite particles after the DMC treatment had a decahedral structure peculiar to ^* BEA type zeolite. Further, as can be seen from the particle size distribution of FIG. 9B, the particle size of the synthesized particles is about 4 to 7 μm, and changes compared to the particle size distribution before the DMC treatment (FIG. 5B). It was confirmed that there was not.

From this, it can be concluded that the DMC treatment did not decompose the outside of the particles, but only the core with many defects could be decomposed. Furthermore, in the XRD pattern after the DMC processing in FIG. 10, a pattern similar to the XRD pattern before the DMC processing (FIG. 4 or FIG. 7) appeared. From this, it was found that the DMC treatment can decompose only the core without breaking ^* BEA type crystals and without producing other crystals.

<Evaluation of hollow formation of synthetic zeolite>
Evaluation of hollow ^* BEA type zeolite having a particle diameter of about 4 to 7 μm synthesized through the above synthesis steps was performed. That is, in order to confirm whether or not the zeolite particles obtained by the above synthesis method formed a hollow, the following three methods were evaluated.

  First, an external force was applied to destroy the hollow particles, and the broken particles were confirmed by SEM. As the external force, a hammer was used. FIG. 11 is an SEM image of particles broken by a hammer. As clearly seen from the SEM image of FIG. 11, it was confirmed that the zeolite particles obtained by the synthesis method formed a hollow.

  As another method, the DMC-treated zeolite particles are introduced into Epok812 resin, solidified in an oven overnight at a temperature of 60 ° C., and the solidified zeolite-containing resin is cut with a diamond cutter. Was observed with a reflected electron beam. For the observation, FESEM (Field-Emission Scanning Electron Microscope; Hitachi S4700 type) was used, and the acceleration voltage was measured at 15 kV. 12A and 12B are reflected electron beam images of the particle cross section. As can be clearly seen from the reflected electron beam images of FIGS. 12A and 12B, it was found that almost all of the zeolite particles obtained by the synthesis method were hollow.

  Further, as another method, similarly to the above, the zeolite particles after the DMC treatment are introduced into Epok812 resin, and are solidified in an oven overnight at a temperature of 60 ° C. The slice was sliced and observed using a transmission electron microscope (TEM: Transmission Electron Microscope; JFE2000CX manufactured by JEOL Ltd.). FIGS. 13A and 13B are TEM images of synthesized zeolite particles. As can be clearly seen from the TEM images of FIGS. 13A and 13B, it was clearly observed that the zeolite particles obtained by the synthesis method were hollow.

<Surface observation of synthetic hollow zeolite>
In order to confirm whether or not the outer surface of the hollow zeolite particles was decomposed by the DMC treatment, the synthesized hollow zeolite particles were further observed using SEM. At the time of observation, as described above, the acceleration voltage was measured at 15 kV using FESEM.

  FIG. 14 is SEM images obtained by observing the outer surface of the zeolite particles before and after the DMC treatment. 14A is an SEM image before DMC processing, FIG. 14B is an SEM image after DMC processing, and (A-2) and (B-2) are (A-1) and (B-1) It is each enlarged image.

As shown in FIGS. 14 (A-1) and (A-2), it was observed that the zeolite particles before DMC treatment had a decahedral structure peculiar to the ^* BEA type and consisted of dense microcrystals. . On the other hand, also in the zeolite particles after DMC process shown in FIG. 14 (B-1), ^* decahedron structure specific to BEA type zeolite particles is observed, the structure of the pre-treatment and the same shape was confirmed. From this, it was found that the outer surface was not decomposed by the DMC treatment.

Moreover, as can be seen from the SEM image of the enlarged allowed outer surface of FIG. 14 (B-2), ^* microcrystals BEA type zeolite, regularly in one plane, also was found to have grown densely.

  From the results of the hollow formation evaluation observation and surface observation of the zeolite particles described above, it can be concluded that zeolite particles having large and clean hollows can be synthesized by the synthesis method shown in Example 1 above.

[Nitrogen adsorption experiment]
(Example 2)
Using the ^* BEA type hollow zeolite synthesized by Example 1, a nitrogen adsorption experiment was conducted. Specifically, measurement was performed at a liquid nitrogen temperature after pretreatment for 2 hours under a temperature condition of 200 ° C. under a helium stream.

The graph shown in FIG. 15 is a graph of nitrogen adsorption isotherms of zeolite particles before and after the internal removal treatment (DMC treatment) with dimethyl carbonate. As shown in this graph, the relative ratio (P / P ₀ ) is near ₀ at both before and after the DMC treatment, and a large amount of nitrogen is adsorbed. It was confirmed to have pores. From this result and the decahedral structure that can be confirmed in the SEM images shown in FIGS. 14A and 14B, it can be concluded that ^* BEA type zeolite is formed.

  In addition, in the adsorption isotherm before the DMC treatment, a small number of steps due to mesopores were seen, while in the adsorption isotherm after the DMC treatment, the same steps as before the treatment were seen. The heights of the steps of the adsorption isotherm before the DMC treatment and the adsorption isotherm after the DMC treatment were substantially the same. From this, it was confirmed that mesopores were not generated again by this DMC treatment. Note that these adsorption isotherm steps before and after the DMC treatment are considered to be caused by defects formed during zeolite synthesis or the Tensile strength effect.

[Drug sustained release effect experiment]
One method for using the hollow zeolite synthesized in Example 1 is application as a capsule for sustained release of drugs and the like. Therefore, in the following, using ^* BEA type hollow zeolite having micropores synthesized in Example 1, ^* BEA type zeolite having micropores, and silica gel having pores having diameters larger than the micropores, From the measurement of the diffusion rate, an evaluation experiment on the drug sustained release effect was conducted.

(Example 3)
^* BEA type hollow zeolite produced in Example 1 was introduced into one leg of a Y-type glass tube with a thread, and ibuprofen (Wako Co., Ltd. (98.5%)) was introduced into the other leg (1 g). ^* 0.5 g of ibuprofen was introduced into the BEA type hollow zeolite). ^* Ribbon heaters were wound around the legs of glass tubes containing BEA type hollow zeolite. And after making the inside of a Y-type glass tube into a vacuum state, it heated for 30 minutes on 50 degreeC temperature conditions, temperature was raised to 200 degreeC after that, and ^* BEA type | mold hollow zeolite was vacuum-dried for 2 hours.

Then, the temperature was lowered to 100 ° C., by tilting the Y-shaped glass tube, were transferred into the micropores of the liquefied ibuprofen was heated to 100 ° C. ^* BEA hollow zeolite. Then, it left still at 100 degreeC for 4 hours, ^* Ibuprofen was made to adsorb | suck to the micropore of a BEA type | mold hollow zeolite.

The solvent for sustained release of ibuprofen using a mixed solution of ion-exchanged water 800ml and ethanol 1200 ml, in ice bath, the release experiments by deriving the adsorbed ibuprofen ^* BEA hollow zeolite in a mixed solution of water and ethanol went.

  The evaluation was performed by measuring the concentration of ibuprofen dissolved in the solvent every 15 minutes using an ultraviolet / visible spectrum (UV-vis; V-650 manufactured by JASCO Corporation). Since the wavelength at 225 nm is an absorption peak derived from the benzene ring of ibuprofen, the ibuprofen concentration was traced over time depending on the absorption rate and concentration.

(Comparative Example 1)
^* BEA zeolite was introduced into one leg of a Y-shaped glass tube with a thread, and ibuprofen (Wako Co., Ltd. (98.5%)) was introduced into the other leg (0 to 1 g of ^* BEA zeolite). Except that 5 g of ibuprofen was introduced), an ibuprofen release experiment was conducted in the same manner as in Example 3.

(Comparative Example 2)
The silica gel produced in Example 1 was introduced into one leg of a Y-shaped glass tube with a thread, and ibuprofen (manufactured by Wako Co., Ltd. (98.5%)) was introduced into the other leg (0 to 1 g of silica gel). Except that 5 g of ibuprofen was introduced), an ibuprofen release experiment was conducted in the same manner as in Example 3.

<Results of drug sustained release effect>
FIG. 16 (A) is a graph showing the relationship between the dissolution time and concentration of ibuprofen when ibuprofen is eluted in a mixed solution of 800 ml of ion-exchanged water and 1200 ml of ethanol without using a porous material. In an experiment conducted without using this porous material, it was dissolved almost completely in about 5 minutes after being introduced into the solvent. As can be seen from this graph, the concentration of ibuprofen did not increase thereafter.

On the other hand, FIG. 16B is a graph of experimental results showing the relationship between the dissolution time and concentration of ibuprofen in Example 3 and Comparative Examples 1 and 2. As can be seen from this graph, in the experiment in Comparative Example 2 performed using silica gel, all of ibuprofen adhering to the surface of the silica gel was dissolved in about 5 minutes after being introduced into the solvent, and then into the pores. The incorporated ibuprofen was completely eluted in about 1 hour. Moreover, in the experiment in Comparative Example 1 conducted using ordinary ^* BEA type zeolite, ibuprofen adhering to the outer surface was eluted about 5 minutes after introduction into the solvent, and then compared with Comparative Example 2 using silica gel. Then, although the time until complete dissolution became longer, all of ibuprofen contained in the pores was eluted after about 2 hours.

In contrast, in the experiment (Example 3) using the ^* BEA type hollow zeolite produced using the synthesis method in Example 1, ibuprofen on the outer surface of the hollow zeolite was dissolved in the solvent in about 1 hour. Thereafter, the encapsulated ibuprofen was slowly released over about 20 hours.

From the above results, it is considered that when silica gel is used, since the pores are large, ibuprofen encapsulated in the pores immediately eluted in the solvent and did not exhibit the sustained release effect. In addition, when using normal ^* BEA type zeolite, it took about 1 hour longer to completely elute because it has pores with a smaller pore size than silica gel. Since the amount of ibuprofen contained in is small, most of ibuprofen is adsorbed only to the outside of the particles, and it is considered that an effective sustained release effect could not be exhibited.

On the other hand, when the ^* BEA type hollow zeolite produced by the synthesis method in Example 1 was used (Example 3), a remarkable sustained release effect could be confirmed. This is because the synthesized ^* BEA type hollow zeolite has a stable hollow inside, so that ibuprofen could be adsorbed not only on the outer surface of the zeolite but also inside the hollow. it is conceivable that. Further, the synthesized hollow zeolite, ^* only micropores crystal structure has inherent BEA type zeolite is formed, since no pores formed by gaps between the particles are formed , Because ibuprofen adsorbed in the hollow interior was easily eluted from pores with large pore diameters, and it was possible to gradually elute outside through the micropores. It is thought that the sustained release effect of 20 hours was exhibited.

It is the schematic which showed typically the procedure of the synthesis | combining method of the hollow zeolite which concerns on this Embodiment. It is a schematic diagram for demonstrating the sustained release effect in the case of using a hollow zeolite as a capsule for drug sustained release. It is a graph of the SEM image (A) and particle diameter distribution (B) of the formed core zeolite. It is a graph which shows the result of the X ray diffraction measurement of the formed core zeolite. It is a graph of the SEM image (A) and particle size distribution (B) of the core-shell zeolite which carried out crystal growth based on the formed core zeolite. It is a graph which shows the result of the X-ray-diffraction measurement of the core-shell zeolite which carried out crystal growth based on the formed core zeolite. It is a graph which shows the result of the X-ray-diffraction measurement of a core shell zeolite before and after dealumination treatment. It is a graph (A) which shows the relationship of the production | generation rate of tetramethoxysilane with respect to DCM processing time, and a graph (B) which shows the relationship of a zeolite decomposition rate. It is a graph of the SEM image (A) and particle size distribution (B) of the zeolite after a DCM process. It is a graph which shows the result of the X-ray-diffraction measurement of the zeolite after a DCM process. It is the SEM image after destroying the zeolite synthesize | combined with the synthesis | combining method of the hollow zeolite which concerns on this Embodiment with a hammer. The cross section of a particle obtained by cutting a resin produced by introducing a zeolite synthesized by the method for synthesizing hollow zeolite according to the present embodiment into Epok812 resin and solidifying it with a diamond cutter is a reflected electron beam image, and (B) is (A) FIG. It is a TEM image of a resin sliced into a thickness of 60 nm obtained by introducing and solidifying a zeolite synthesized by the hollow zeolite synthesis method according to the present embodiment into Epok812 resin, and (B) is an enlargement of (A) It is a TEM image. It is the SEM image which observed the outer surface of the zeolite particle before and after DMC processing (before (A) processing and after (B) processing). It is a graph of the nitrogen adsorption isotherm before and after the DCM treatment. It is a graph which shows the result of the sustained-release effect experiment of ibuprofen, (A) is a graph which shows the relationship between melt | dissolution time at the time of eluting ibuprofen without using a porous body, (B) is a silica, ^* It is a graph which shows the relationship between the melt | dissolution time and density | concentration of ibuprofen at the time of using each porous body of a BEA type | mold zeolite and ^* BEA type | mold hollow zeolite in this Embodiment. It is an observation image of the hollow silica particle synthesize | combined by the conventional method, (A) is a TEM image of a hollow silica particle, (B) is a SEM image of a hollow mesoporous silica, (B-1) is ( It is an enlarged SEM image of B-2). It is an observation image of the hollow zeolite particle synthesize | combined by the conventional method, (a) and (b) are the SEM image and TEM image of the hollow zeolite particle respectively synthesize | combined by alkali treatment, (c) and (d) are polystyrene. 2 is an SEM image of hollow zeolite particles synthesized using beads as a template.

Claims (10)

A core zeolite forming step for forming a core zeolite containing a metal;
A core-shell zeolite forming step of growing a zeolite crystal around the core zeolite formed in the core zeolite forming step to form a core-shell zeolite;
A metal removal step of removing the metal from the core-shell zeolite formed in the core-shell zeolite formation step;
A hollow forming step of contacting a silica decomposing agent and decomposing the core zeolite from which the metal has been removed in the metal removing step to form a hollow in the core-shell zeolite.   The method for synthesizing a hollow zeolite according to claim 1, wherein, in the hollow forming step, a hydrophilic alkali metal salt is supported on the core-shell zeolite as a decomposition catalyst.   The method for synthesizing a hollow zeolite according to claim 1 or 2, wherein the silica decomposing agent contains dimethyl carbonate.   The method for synthesizing a hollow zeolite according to any one of claims 1 to 3, wherein in the metal removal step, the metal is dissolved and removed with an acidic solution.   The method for synthesizing a hollow zeolite according to claim 4, wherein the metal is a metal having a higher ionization tendency than hydrogen.   The method for synthesizing a hollow zeolite according to claim 5, wherein the metal is aluminum. It is synthesized by the method for synthesizing hollow zeolite according to any one of claims 1 to 6,
A hollow zeolite in which the pores of the hollow zeolite are composed only of pores derived from the pores of the crystal structure of the zeolite crystal.   The hollow zeolite according to claim 7, wherein the pore is a micropore. A hollow zeolite synthesized by the hollow zeolite synthesis method according to any one of claims 1 to 6,
A drug carrier in which the pores of the hollow zeolite are composed only of pores derived from the pores of the crystal structure of zeolite crystals.   The drug carrier according to claim 9, wherein the pore is a micropore.

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