JP6528615B2 - Method of producing fine zeolite - Google Patents

Description

  The present invention relates to a method for producing fine zeolite, and more particularly to a method for producing fine zeolite having good crystallinity.

  Zeolite is a generic term for crystalline porous aluminosilicates, and is widely used industrially, such as ion exchange materials, adsorbents and catalysts. For example, the non-phosphorus detergent using ion exchange material of zeolite, which has been put into practical use since around 1980, dramatically improved the deterioration of water quality (eutrophication) of lakes due to domestic drainage and contributed greatly to the environmental protection of Japan. At present, research on precise control of structure, physical properties and functions is being made in many fields as a key material for realizing a sustainable society. For example, although the particle size of the zeolite used as an ion exchange material or catalyst is 0.5 to several μm, the diffusion of the ion to be subjected to ion exchange or the reactive molecule of the catalytic reaction becomes limited in the zeolite pore. In order to improve ion exchange and catalytic reaction rate, research on synthesis of zeolite nanoparticles has been actively conducted.

  In the synthesis of the zeolite nanoparticles, a bottom-up method, that is, a method of controlling nucleation and crystal growth using a quaternary ammonium salt or a special organic substance is employed. For example, when synthesizing nanoparticles of LTA type zeolite which is a typical ion exchange material, tetramethyl ammonium salt which is an organic structure specifying agent is used (for example, Non-patent document 1). However, such organic structure directing agents are generally expensive at present, and the synthesis of LTA-type zeolite nanoparticles requires the addition of 1/4 to 1/2 of tetramethylammonium salt based on the weight of the zeolite obtained. is there. In addition, tetramethyl ammonium salt needs to be finally fired and removed, but since the exhaust gas at that time contains nitrogen oxides (NOx), it is necessary to set up a facility to process this. As described above, mass production of nanoparticles of LTA-type zeolite by the bottom-up method has problems in cost.

  As a measure to cope with such a problem by the bottom-up method, the zeolite represented by a predetermined general formula having a large particle size which can be manufactured inexpensively without using an organic structure specifying agent is pulverized and refined Method to recrystallize in aluminosilicate solution or silicate solution (patent documents 1 and 2), the method of carrying out the solvothermal processing of what refined the zeolite from which the framework structure of zeolite differs from patent documents 1 and 2 (patent document 3) ) Has been proposed. In addition, after the slurry for zeolite synthesis is subjected to hydrothermal treatment, the zeolite particles in the slurry are separated from the synthesis mother liquor, and the obtained zeolite particles are pulverized and refined, then mixed with the synthesis mother liquor and subjected to hydrothermal treatment Has been proposed (Patent Document 4). According to the methods described in Patent Documents 1 to 4, the crystallinity of the finely pulverized zeolite is reduced, but the crystallinity is recovered to the same degree as that before the pulverization treatment by recrystallization under predetermined conditions. be able to.

JP, 2011-246292, A JP, 2013-49602, A JP, 2014-189476, A JP, 2014-139124, A

Svetlana Mintova et. Al, 'Mechanizm of Zeoiite A Nanocrystal Growth from Colloids at Room Temperature', Science, 1999, Vol. 283 no. 5404 pp. 958-960

According to the methods described in Patent Documents 1 to 4, it is possible to produce a fine zeolite having the same degree of crystallinity as that before grinding by recrystallizing the ground zeolite. However, in these methods, the temperature at the time of recrystallizing the crushed zeolite is 50 ° C. or more (Patent Document 1), 100 ° C. or more (Patent Document 2), or the crushed zeolite is 100 ° C. or more A method is adopted in which solvothermal treatment is carried out at a temperature of 5 (Patent Document 3) or hydrothermal treatment is carried out at a temperature of 50 ° C. or higher after mixing the ground zeolite with a mixed mother liquid (Patent Document 4). Also, in the examples in these documents, only higher temperatures are described. For example, in Example 1 of Patent Document 1, recrystallization is performed at 80 ° C. for 2 hours, and in Example 3 at 150 to 230 ° C. for 10 to 24 hours. In Example 1 of Patent Document 2, Recrystallization is performed at 180 ° C. Recrystallization is performed for 24 hours, and in Example 1 of Patent Document 3, solvothermal treatment is performed at 190 ° C. for 3 hours to perform recrystallization. In Examples 1, 4, and 5 of Patent Document 4, 95 ° C. Hydrothermal treatment is carried out by performing the hydrothermal treatment for 15 hours in Example 2, 3 for 15 hours at 170 ° C. in Example 2, and for 15 hours at 120 ° C. in Example 6. As described above, in the prior art, it can be said that heating at 50 ° C. or more and actually at 80 ° C. or more for 2 hours or more was essential in recrystallization. In addition, since heating is performed at 50 ° C. or more for a predetermined time, there is a problem that the energy cost is large. Furthermore, in the case of heating to 100 ° C. or higher, there is also a problem that a special pressure-resistant recrystallization apparatus is required.
Although it is a bottom-up method, non-patent document 1 describes that the synthesis of zeolite is carried out at a room temperature of 30 ° C. or less, but the obtained zeolite particles have low crystallinity and the particle diameter is increased. There is a problem of
Therefore, the object of the present invention is to reduce the energy cost for heating at the time of recrystallization compared to the prior art, and to make the fine zeolite particles having the same crystallinity as the prior art cheaper than before. It is an object of the present invention to provide a method for producing a fine zeolite which can be produced by

  In view of the above-mentioned subject, the present inventors diligently studied. As a result, it has been found that even if recrystallization is performed at a temperature lower than 50 ° C., it is possible to improve the crystallinity of the crushed zeolite particles to the same extent as before, and the present invention is completed. The The gist of the present invention is as follows.

The present invention have the general _{formula: M 2 O · xSiO 2 ·} Al 2 O 3 ( where, M represents an alkali metal, ^{H +} or _NH ^{4 +,} an x = 2 to 6.) Mean represented by Pulverizing process step of pulverizing raw material zeolite having a particle size of 0.5 μm or more,
The crushed zeolite is recrystallized in an alkaline solution at 15 ° C. or more and 45 ° C. or less, and an average particle diameter of 0.3 μm or less, crystals after recrystallization with respect to the degree of crystallization (A) before recrystallization The present invention relates to a method for producing a fine zeolite, comprising a recrystallization step of obtaining a zeolite having a degree of conversion (B) (B / A) of 1.2 or more.

In the present invention, as a raw material zeolite, the general _{formula: M 2 O · 2SiO 2 ·} Al 2 O 3 ( where, M is an alkali metal, represents a ^{H +} or _NH ^{4 +.)} To use a zeolite represented by Preferably, the zeolite structure defined by the International Zeolite Association (IZA) is LTA.

  In the present invention, the degree of crystallinity after recrystallization is preferably 85% or more of that of the raw material zeolite.

  In the present invention, the alkali solution may be an aqueous solution of an alkali metal hydroxide.

  In the present invention, the weight ratio (W / Z) of the ground zeolite (Z) to the alkali solution (W) is preferably 0.1 or more and 30 or less.

  According to the present invention, it is possible to carry out recrystallization at a temperature lower than that of the prior art, so that it is possible to reduce the energy cost for heating, and fine zeolite particles with good crystallinity can be obtained. It becomes possible to manufacture cheaply compared with the former.

It is an image of the scanning electron microscope (SEM) of the raw material zeolite used in Examples 1-3. It is an image of the scanning electron microscope (SEM) of the crushed zeolite used in Examples 1-3. It is a scanning electron microscope (SEM) image of fine zeolite after recrystallization (recrystallization time: 22 hours) in Example 1. It is a scanning electron microscope (SEM) image of fine zeolite after recrystallization (recrystallization time: 26 hours) in Example 2. It is a scanning electron microscope (SEM) image of fine zeolite after recrystallization (recrystallization time: 243 hours) in Example 3.

  Hereinafter, an embodiment of the method for producing fine zeolite of the present invention will be described.

Method for producing a fine zeolite of the present invention have the general _formula: M 2 O _· xSiO in 2 · _Al 2 _{O 3} (wherein, M represents an alkali metal, ^{H +} or _NH ^{4 +,} an x = 2 to 6. A grinding process step of grinding the raw material zeolite having an average particle diameter of 0.5 μm or more represented by
The crushed zeolite is recrystallized in an alkaline solution at 15 ° C. or more and 45 ° C. or less, and an average particle diameter of 0.3 μm or less, crystals after recrystallization with respect to the degree of crystallization (A) before recrystallization It includes a recrystallization step to obtain a zeolite having a conversion degree (B) ratio (B / A) of 1.2 or more.
As described above, in the present invention, since the raw material zeolite having an average particle diameter of 0.5 μm or more represented by the above general formula is used, inexpensive zeolite can be used as the raw material unlike the conventional bottom-up method. In addition, energy cost can be reduced compared to the prior art because the crushed zeolite is recrystallized in an alkaline solution at 15 ° C. or more and 45 ° C. or less. In addition, the zeolite obtained by the present invention is as fine as 0.3 μm or less in average particle diameter, and the degree of crystallinity is comparable to that of the prior art.

  In the present invention, first, a pulverizing treatment step of pulverizing the raw material zeolite having an average particle diameter of 0.5 μm or more represented by the above-mentioned general formula is performed.

Raw material zeolite used in the present invention have the general _{formula: M 2 O · xSiO 2 ·} Al 2 O 3 ( where, M represents an alkali metal, ^{H +} or _NH ^{4 +,} an x = 2 to 6.) In It is represented.
M represents a cation present in the zeolite skeleton, and this cation is often an alkali metal at the time of zeolite production, but depending on the application, this alkali metal may be substituted by H + or NH 4 +. In the present invention, these can be suitably used as raw material zeolite. As the alkali metal, lithium (Li), sodium (Na) and potassium (K) are preferable, and Na and K are more preferable.
x is 2 to 6, that is, Si / Al is 1 to 3. From the viewpoint of being easily available and reducing the manufacturing cost, x is preferably 2 to 4, and x is more preferably 2.

Examples of the type of raw material zeolite represented by the general formula include LTA, FAU, ABW, SOD, GIS, OFF, GME, ERI, LTL and the like as the zeolite structure defined by the International Zeolite Association (IZA). Among these, from the viewpoint of efficiently performing recrystallization in the temperature range of the present invention, LTA, FAU, GIS, and SOD are preferable, and LTA is particularly preferable. The raw material zeolite may be represented by the same composition formula, or may be a combination of those represented by different composition formulas.
The raw material zeolite has such a predetermined crystal structure and serves as a reference for the degree of crystallinity described later.

As the raw material zeolite, one having an average particle diameter of 0.5 μm or more can be used. In the present invention, from the viewpoint of finally obtaining a fine zeolite of 0.3 μm or less, using a raw material zeolite having a particle diameter close to 0.3 μm as the starting material also facilitates the pulverizing treatment. It is preferable from the viewpoint of suppressing the amorphization due to the pulverizing treatment. From such a viewpoint, the average particle diameter is preferably 3 μm or less, and more preferably 1 μm or less.
The average particle size can be calculated, for example, by the method described later.

  The grinding treatment may be performed by any method as long as the raw material zeolite can be ground so that a fine zeolite having an average particle size of 0.3 μm or less after recrystallization can be obtained. As a method of such a grinding process, a bead mill, a ball mill, a planetary ball mill, a jet mill etc. are mentioned, for example. Among them, a bead mill is preferred from the viewpoint of minimizing the amorphization of the zeolite at the time of grinding. A bead mill is an apparatus which grinds and disintegrates normally, using the ceramic bead of particle diameter 30-1000 micrometers as a grinding | pulverization media. As described above, since fine beads are used, unlike the ball mill and the planetary ball mill, the powder to be treated frequently collides with the beads, and the force applied to the particles at one collision is small. It can grind | pulverize efficiently, suppressing amorphousization. However, even when using a bead mill, the amorphization of zeolite can not be avoided, and some amorphization occurs. Although the addition amount of the ceramic beads is not particularly limited, it is preferably 60 to 80% in terms of bulk density with respect to the volume in the bead mill grinding chamber, from the viewpoint of efficiently grinding while suppressing amorphization of zeolite. 70% is more preferable.

  The grinding treatment may be either wet or dry, but is preferably carried out wet from the viewpoint of ease of grinding and the uniformity of the particle diameter of the zeolite. When the pulverization treatment is carried out wet, the raw material zeolite is dispersed in a dispersion medium. As such a dispersion medium, water, alcohols such as ethanol, mixed solvents thereof and the like can be mentioned. Among them, it is preferable to use water from the viewpoint of handleability and cost. Moreover, from the viewpoint of preventing reaggregation of the crushed zeolite, an alcohol such as ethanol is preferable. From the viewpoint of uniformly dispersing the raw material zeolite and the crushed zeolite in the dispersion medium, a surfactant, an aggregation inhibitor, and the like may be added as needed.

  The time of the pulverization treatment can be appropriately determined according to the method of the pulverization treatment, the desired particle diameter, the recrystallization treatment time and the like. The degree of amorphization tends to increase as the grinding time increases.

  Next, the zeolite ground as described above is recrystallized in an alkali solution at 15 ° C. or more and 45 ° C. or less, and has an average particle diameter of 0.3 μm or less, and the crystallinity degree before recrystallization (A ) Is performed to obtain a zeolite having a ratio (B / A) of crystallinity (B) after recrystallization of 1.2 or more.

  The alkaline solution used in the present invention is not particularly limited as long as it has a pH of 13 or more and can accelerate recrystallization of zeolite which has been made amorphous by pulverization treatment. As such an alkaline solution, for example, an aluminosilicate solution as described in Patent Document 1 or a solution according thereto, a silicate solution as described in Patent Document 2 or a solution according thereto, an alkali metal hydroxide And the like. Among them, an aqueous solution of an alkali metal hydroxide is preferable from the viewpoint of cost and the viewpoint of suppressing crystal growth. As the alkali metal hydroxide, LiOH, NaOH, KOH and the like can be mentioned, but NaOH, KOH is preferable, and NaOH is more preferable. In the present invention, it has been found that recrystallization can be performed even with an aqueous solution of an alkali metal hydroxide, without using a special solution such as a conventional aluminosilicate solution or silicate solution. There is. A portion of the amorphous portion of the ground zeolite is dissolved in an aqueous solution of an alkali metal hydroxide, and substantially converted into an aluminosilicate solution, which promotes recrystallization to promote the aluminosilicate solution. As in the case of using, it is considered that the increase in grain size can be suppressed without crystal growth.

  When an aqueous solution of an alkali metal hydroxide is used as the alkali solution, the concentration of the alkali metal hydroxide is appropriately determined in consideration of the content of the crushed zeolite, the degree of crystallization of the zeolite, the treatment of waste liquid after recrystallization, etc. Although it can be determined, if the concentration is too low, recrystallization tends to be difficult, and if it is too high, the viscosity of the alkali solution is high and the diffusion of alkali metal ions tends to be too low. From the viewpoint of improving the degree of crystallinity, 0.5 to 4 M is preferable, 0.75 to 3 M is more preferable, and 1 to 2.5 M is particularly preferable.

The aluminosilicate _{solution, aM 2 O / bAl 2 O} 3 / cSiO 2 / dH 2 O ( wherein, M represents K or Na, a / d is 0.001~0.040, b / d is 0 Preferably, the composition has a composition of 0.0003 to 0.000250, and c / d is 0.0001 to 0.1000. When the ratio of Si to Al (Si / Al) in the zeolite is 2 or less, a / d is 0.0100 to 0.0390, b / d is 0.0000005 to 0.00024, and c / d is 0. When the ratio of Si to Al of the zeolite (Si / Al) is more than 2 and 3 or less, a / d is 0.00160 to 0.00500, and b / d is preferably 0.000330 to 0.100000. It is preferable that it is 0.0000031-0.0001000 and c / d is 0.000500-0.003000.

As a silicate solution, aM ₂ O / bSiO ₂ / cH ₂ O (wherein, M represents an alkali metal, a / c (molar ratio) is 0.001 to 0.040, and b / c is It is preferable to have a composition of 0.0001 to 0.1000.

  In the present invention, the temperature at which the crushed zeolite is recrystallized in an alkaline solution is 15 ° C. or more and 45 ° C. or less. The temperature is preferably 20 ° C. or more and 45 ° C. or less, more preferably 30 ° C. or more and 45 ° C. or less, and particularly preferably 40 ° C. or more and 45 ° C. or less. If it is less than 15 ° C., productivity tends to be low due to slow recrystallization rate, and if it exceeds 45 ° C., the recrystallization rate is fast but productivity corresponding to the energy cost for heating is obtained. It tends to be difficult to The present invention, for the first time, has found that, unlike the conventional method, it is possible to recrystallize the amorphized zeolite by grinding even in such a temperature range. And since recrystallization is possible in such a temperature range, depending on the case, recrystallization is possible without heating at room temperature (25 ° C. to 35 ° C.), and heating in the recrystallization treatment is It will be possible to significantly reduce the energy costs to do.

  When heating is required in such a temperature range, a conventionally known heating device may be used. For example, there is a method of providing a heater in a mixed solution of an alkaline solution and zeolite, or providing a heater or the like around a mixing tank containing the mixed solution, but the method is not limited thereto. In addition, heating may be performed while controlling the temperature of the alkali solution, that is, the mixed solution to be within a predetermined temperature range.

  The weight ratio (W / Z) of the ground zeolite (Z) to the alkali solution (W) during recrystallization treatment is not particularly limited, but from the viewpoint of production efficiency, W / Z is 0 1 or more and 30 or less are preferable, and 2 or more and 5 or less are more preferable.

In the present invention, the recrystallization treatment may be allowed to stand or be stirred after mixing the ground zeolite and the alkali solution. Stirring tends to improve the rate of recrystallization.
The treatment time of the recrystallization treatment may be appropriately determined so as to be a desired recrystallization degree described later according to various conditions.

In the present invention, the recrystallization treatment is performed such that the ratio (B / A) of the degree of crystallization (B) after recrystallization to the degree of crystallization (A) before recrystallization is 1.2 or more. Since the more preferable range of the ratio of B / A may vary depending on the degree of crystallinity immediately before the recrystallization treatment, when A is low (approximately 30% or less), preferably, the ratio of B / A is Is 2 or more.
By performing recrystallization treatment such that the ratio of the degree of crystallinity is obtained, a fine zeolite with excellent crystallinity that can withstand various uses can be obtained.
The degree of crystallinity is obtained by dividing the sum (H) of the areas of major peaks by X-ray diffraction of zeolite before or after recrystallization by the sum (H ₀ ) of the areas of major peaks of raw material zeolite. And expressed as a percentage value. The degree of crystallization is calculated, for example, as described later.

  The crystallinity of the zeolite after the recrystallization treatment may be such that the crystallinity that can withstand various applications is ensured, but in order to further improve the functions of various applications, from the viewpoint of obtaining fine zeolite with better crystallinity. The crystallization degree after recrystallization is preferably 85% or more of the raw material zeolite, more preferably 90% or more, and particularly preferably 95% or more.

The average particle size of the zeolite after recrystallization treatment is preferably 0.3 μm or less.
In the present invention, the grain size is reduced by pulverizing the raw material zeolite, but even if recrystallization is performed, crystal growth can be suppressed. In particular, this is remarkable when using the above-described silicate solution or an aqueous solution of alkali metal hydroxide as the alkali solution. Therefore, the grain size is substantially not affected by various conditions such as recrystallization treatment time. That is, the average particle size after recrystallization is substantially determined by the grinding process.
The average particle size may be appropriately determined in accordance with the application etc., but the particle size after the pulverization process is approximately the average particle size of the zeolite after recrystallization, and it is necessary to consider the conditions at the time of the recrystallization process There is no Therefore, in the recrystallization treatment step, conditions for obtaining a desired degree of crystallinity may be adjusted.
The average particle size can be calculated, for example, by the method described later.

  The yield after the recrystallization treatment is preferably 85% or more by dry weight before the recrystallization treatment, and more preferably 90% or more.

In the present invention, after the recrystallization step is completed, a separation step of separating the recrystallized fine zeolite and the alkali solution can be performed. In the present invention, since a fine zeolite having a desired degree of crystallinity and particle diameter can be obtained by the recrystallization step performed in a predetermined temperature range, it is possible to carry out the reheat treatment without requiring heating energy as in Patent Document 4 After the crystallization step, the separation step can be continued. The separation method is not particularly limited, and filtration, centrifugation and the like can be used. Further, washing may be performed in the separation step. Furthermore, drying may be performed after washing. The conditions of the drying treatment can be appropriately determined according to the desired final form and the like.
These steps after the recrystallization step may be appropriately performed depending on the final form of the fine zeolite.

  The fine zeolite obtained as described above has a particle diameter of 0.3 μm or less and a desired degree of crystallinity, and thus can be suitably used for various applications such as catalysts, adsorbents, ion exchange materials, etc. .

  Hereinafter, embodiments of the present invention will be described more specifically.

(Measurement of average particle size)
Photograph the raw material zeolite and the recrystallized zeolite with a scanning electron microscope (SEM) (JSM-7000F, manufactured by Nippon Denshi Co., Ltd.), and select at least 30 particles that do not overlap other particles in the SEM photograph. The length of the major axis and the minor axis of each particle is measured, and the arithmetic mean is taken as the particle size. The arithmetic mean of this particle size is calculated as an average particle size.

(Calculation of crystallinity)
(I) Calculation of each spectrum area a) Using an X-ray diffractometer (D2 PHASER manufactured by Bruker AXS Co., Ltd.), the raw material zeolite, and the XRD spectra of the zeolite before and after regrind treatment after grinding treatment are 2θ Measure at about 3 ° to 50 °.
b) With reference to spectral data such as IZA, select a peak between 2θ of 19 ° and 35 °.
c) Choose a fitting function (usually a Lorentz function, or a Gaussian function if there is a lot of noise and a large shift in the Lorentz function), and fit to the peak selected in b).
d) Add the areas of the peaks fitted in c), and let this be the spectral area of the sample.
(II) Calculation of crystallinity degree a) The spectrum area (H ₀ ) of the raw material zeolite is calculated by the procedure of (I).
b) Calculate the spectral area (H) of the zeolite before recrystallization treatment or after recrystallization treatment according to the procedure of (I).
c) Calculate the crystallinity (%) from H ₀ and H according to the following equation.
Crystallinity (%) = H / H ₀ × 100

(Example 1): When recrystallization temperature is 45 ° C. LTA type zeolite (Si / Al ratio is 1, Na: cation manufactured by Tosoh Corp. Zeoram A-4, 100 mesh) which is a raw material in 100 ml of water as a dispersion medium 60 g of (average particle diameter 4 μm, 100% crystal structure, see FIG. 1) was added to adjust the slurry. On the other hand, a bead mill (LM Z015 manufactured by Ashizawa Finetech Co., Ltd.) using ZrO ₂ beads of 300 μm in diameter was filled with 150 mL of water, the rotation shaft was rotated at a rotational speed of 3000 rpm, and the slurry was charged over 8 minutes. The amount of ZrO ₂ used was such that the bulk density was 70%. What was crushed for 2 hours after charging was recovered as crushed zeolite (pulverization process).
The crystallinity of the recovered crushed zeolite was measured.
Moreover, the image of the scanning electron microscope (SEM) of ground zeolite is shown in FIG.

1 g of crushed zeolite (in terms of solid content) was placed in a container containing 2 g of 2 M aqueous NaOH solution, and the container was immersed in a water tank controlled to 45 ° C. and allowed to stand for a predetermined time to perform recrystallization treatment (recrystallization Treatment process).
The liquid containing the crushed zeolite was centrifuged using a centrifuge to separate the precipitate (zeolite) and the solution. The precipitate (zeolite) was recovered, dispersed in ion-exchanged water, and the zeolite was sufficiently washed by repeating the same centrifugation (separation step).
The washed product was dried and brought to an anhydrous state to obtain a fine zeolite powder (drying step).
The crystallinity of the obtained fine zeolite powder was measured. The relationship between the recrystallization treatment time and the degree of crystallinity is shown in Table 1. In Tables 1 to 3, the degree of crystallization when the recrystallization time is 0 h corresponds to the degree of crystallization before the recrystallization treatment (after the pulverization treatment).
Moreover, the image of the scanning electron microscope (SEM) of the fine zeolite in which recrystallization time is 22 hours is shown in FIG. From the comparison of FIGS. 1 and 2, it can be seen that the raw material zeolite is reduced in particle size by the pulverizing treatment. Further, from the comparison between FIGS. 2 and 3, it can be seen that the size of the particles after the recrystallization treatment does not greatly fluctuate from the size of the particles after the grinding treatment, and the crystal growth is suppressed.
Further, the yields (based on solid content) at recrystallization times of 3, 4 and 22 hours in Table 1 were 94, 97 and 100%, respectively, of the amount of ground zeolite added in the recrystallization treatment.

Example 2 When Recrystallization Temperature is 30 ° C. A fine zeolite powder was obtained in the same manner as Example 1, except that the recrystallization temperature was set to 30 ° C. The relationship between the recrystallization treatment time and the degree of crystallinity is shown in Table 2. Moreover, the image of the scanning electron microscope (SEM) of the fine zeolite whose recrystallization time is 26 hours is shown in FIG. From the comparison of FIGS. 2 and 4, it can be seen that the size of the particles after the recrystallization treatment does not greatly fluctuate from the size of the particles after the grinding treatment, and the crystal growth is suppressed.
Moreover, the yield (solid content basis) in 22.6, 26 and 43 hours of recrystallization time in Table 2 is 100, 94 and 97% of the quantity of the grinding zeolite thrown in in the recrystallization process, respectively. The

Example 3 When Recrystallization Temperature is 15 ° C. A fine zeolite powder was obtained in the same manner as Example 1, except that the recrystallization temperature was 15 ° C. The relationship between the recrystallization treatment time and the degree of crystallinity is shown in Table 3. Moreover, the image of the scanning electron microscope (SEM) of the fine zeolite whose recrystallization time is 243 hours is shown in FIG. From the comparison of FIGS. 2 and 5, it can be seen that the size of the particles after the recrystallization treatment does not greatly fluctuate from the size of the particles after the grinding treatment, and the crystal growth is suppressed.
In addition, the yield (based on solid content) at a recrystallization time of 243 hours in Table 3 was 95% of the amount of ground zeolite charged in the recrystallization treatment.

As described above, according to the present invention, a fine zeolite having a desired degree of crystallinity and an average particle diameter of 0.3 μm or less is obtained under the temperature condition of 15 ° C. or more and 45 ° C. or less. It is possible to provide a fine zeolite having good crystallinity while reducing energy costs without heating at 50 ° C. or higher.

Claims (6)

General _formula: M 2 O _· xSiO (. Wherein, M represents an alkali metal, ^{H +} or _NH ^{4 +,} is _{x = 2~6) 2 · Al 2} O 3 Average particle size 0, represented by. Grinding process to grind raw material zeolite of 5 μm or more,
The ground zeolite is recrystallized in an alkaline solution at 15 ° C. or more and 45 ° C. or less, and after crystallization with respect to the degree of crystallization (A) before recrystallization with an average particle diameter of 0.3 μm or less A method for producing a fine zeolite, comprising a recrystallization step of obtaining a zeolite having a degree (B) ratio (B / A) of 1.2 or more. Raw material zeolite has the general _{formula: M 2 O · 2SiO 2 ·} Al 2 O 3 ( where, M is an alkali metal, represents a ^{H +} or _NH ^{4 +.)} Manufacture of fine zeolite according to claim 1, which is represented by Method.   The method for producing a fine zeolite according to claim 1 or 2, wherein the raw material zeolite has a zeolite structure defined by International Zeolite Association (IZA) is LTA.   The method for producing fine zeolite according to any one of claims 1 to 3, wherein the degree of crystallinity after recrystallization is 85% or more of that of the raw material zeolite.   The method for producing fine zeolite according to any one of claims 1 to 4, wherein the alkali solution is an aqueous solution of an alkali metal hydroxide. The weight ratio (W / Z) of the crushed zeolite (Z) to the alkali solution (W) is 0.1 or more and 30 or less, The method for producing fine zeolite according to any one of claims 1 to 5. .