JP7145002B2 - Method for producing zeolite - Google Patents

Description

The present invention relates to a method for producing a zeolite having a low Al content (high SiO ₂ /Al ₂ O ₃ molar ratio), high crystallinity, and low by-products (eg, zeolites other than the desired zeolite).

Zeolite is a generic term for crystalline aluminosilicates and crystalline metallosilicates. Beta zeolite is a type of crystalline aluminosilicate containing Si and Al, and has a three-dimensional pore structure containing pores of 12-membered oxygen rings. Beta zeolite having such a characteristic pore structure is widely used in various fields. For example, it is used as a catalyst for hydrodewaxing, synthesis of cumene, and purification of nitrogen oxides.

Methods for producing beta-type zeolite can be roughly divided into production methods using an organic structure-directing agent (also referred to as a template or OSDA) and production methods not using an organic structure-directing agent. In the method using OSDA, OSDA is expensive, and a waste liquid containing organic matter is generated during the synthesis of beta zeolite, thus causing a large environmental load. Therefore, in recent years, manufacturing methods that do not use OSDA have attracted attention.

As a production method that does not use OSDA, for example, as described in Patent Documents 1 to 3, there is a method of hydrothermally treating a mixture containing beta zeolite seed crystals, a Si source, an Al source, an alkali source, and water. Are known. In addition, as described in Non-Patent Document 1, a method of hydrothermally treating a mixture containing seed crystals of beta-type zeolite, faujasite-type zeolite, an alkalinity source, and water is also known. However, in these methods, beta-type zeolite with a low Al content, for example, beta-type zeolite in which the molar ratio of Si to Al is 15 or more in terms of SiO ₂ /Al ₂ O ₃ , and has high crystallinity , it was difficult to synthesize a product with few by-products.

Japanese Unexamined Patent Application Publication No. 2011-126768 Japanese Patent Publication No. 2013-526406 JP 2015-205277 A

Microporpus and Mesoporous Materials 142(2011) 161-167

The present invention has a low Al content (high SiO ₂ /Al ₂ O ₃ molar ratio), high crystallinity, and by-products (for example, other than the desired zeolite) in the conventional production method that does not use OSDA. This solves the problem that it is difficult to synthesize zeolite with a small amount of zeolite. Specifically, the present invention provides, for example, a production method capable of synthesizing beta-type zeolite having a SiO ₂ /Al ₂ O ₃ molar ratio of 15 or more, high crystallinity, and few by-products. . Further, the present invention applies not only to beta-type zeolite, but also to zeolite containing Si and Al, for example, chabazite-type zeolite (hereinafter also referred to as CHA-type zeolite), which has a high SiO ₂ /Al ₂ O ₃ molar ratio. Provided is a production method capable of synthesizing a CHA-type zeolite with high crystallinity.

The present invention relates to a production method for heat-treating a reaction slurry obtained by mixing a zeolite serving as a seed crystal, a zeolite having a different crystal system from that of the seed crystal, an alkali source, and water, wherein the composition of the reaction slurry during the heat treatment is It has been found that by changing the content, a zeolite with a low Al content, high crystallinity, and low by-products can be synthesized.

The present invention solves the conventional problems based on the above knowledge, and provides a method for producing zeolite having the following constitution.
[1] A method for producing zeolite without using an organic structure-directing agent,
a reaction slurry preparation step of preparing a reaction slurry by mixing a beta-type or chabazite-type zeolite as a seed crystal, an FAU-type zeolite whose crystal system is different from that of the seed crystal, an alkali source, and water;
_providing an additional slurry having a higher SiO2 /Al2O3 _molar ratio _than the reaction slurry or an additional slurry having a lower M2O/SiO2 molar ratio than the _{reaction slurry} ;
including a heat treatment step of heating the reaction slurry,
In the heat treatment step, the additional slurry is added to the reaction slurry over at least one hour to increase the SiO ₂ /Al ₂ O ₃ molar ratio of the reaction slurry, or to increase the M ₂ O/SiO ₂ molar ratio. A method for producing zeolite, characterized by lowering

In the production method of the present invention, changing the composition of the reaction slurry in the heat treatment step means, for example, the SiO ₂ /Al ₂ O ₃ molar ratio of the reaction slurry, or the M ₂ O / SiO ₂ molar ratio (M is an alkali metal ) is changed during heat treatment. In order to change the molar ratio of these, for example, a reaction slurry having a molar ratio different from that of the reaction slurry being heat-treated may be added during the heat treatment.

The change in the molar ratio of the reaction slurry includes, for example, making the SiO ₂ /Al ₂ O ₃ molar ratio higher than before heating or making the M ₂ O/SiO ₂ molar ratio lower than before heating. In order to make the SiO ₂ /Al ₂ O ₃ molar ratio of the reaction slurry higher than before heating, a reaction slurry having a higher SiO ₂ /Al ₂ O ₃ molar ratio than before heating may be added. In order to make the M ₂ O/SiO ₂ molar ratio of the reaction slurry lower than before heating, a reaction slurry having a lower M ₂ O/SiO ₂ molar ratio than before heating may be added.

According to the production method of the present invention, it is possible to synthesize beta-type zeolite with a low Al content, high crystallinity, and few by-products in a zeolite production method that does not use OSDA. Specifically, for example, it is possible to synthesize a beta-type zeolite having a SiO ₂ /Al ₂ O ₃ molar ratio of 15 or more, a crystallinity of 90% or more, and no by-products such as mordenite.

In addition, according to the production method of the present invention, in the method for producing zeolite without using OSDA, zeolite other than beta-type zeolite, such as CHA-type zeolite, has a low Al content and high crystallinity, and a by-product can obtain zeolite with less Specifically, for example, a CHA-type zeolite having a SiO ₂ /Al ₂ O ₃ molar ratio of 8 or more and a crystallinity of 100% or more can be synthesized.

The manufacturing method of the present invention will be specifically described below.
The present invention relates to a method for producing zeolites without using an organic structure directing agent (OSDA). That is, the production method of the present invention comprises a reaction slurry preparation step of preparing a reaction slurry by mixing a zeolite serving as a seed crystal, a zeolite having a crystal system different from that of the seed crystal, an alkali source, and water, and heating the reaction slurry. A manufacturing method comprising a heat treatment step, characterized in that the composition of the reaction slurry is gradually changed during the heating step.

In the present invention, OSDA is not used in each step. Depending on the production method of the zeolite used as the seed crystal, OSDA may remain in the pore structure of the zeolite. can be regarded as not The same is true for zeolites different from seed crystals.

[Difference between the production method of the present invention and a conventional production method that does not use OSDA]
A conventional manufacturing method that does not use OSDA is to heat-treat a slurry containing a Si source, an Al source, and seed crystals in the presence of an alkali source and water to obtain Si and Al supplied from the Si source and the Al source. is a method for growing zeolite as a seed crystal (Patent Documents 1 to 3).

On the other hand, Non-Patent Document 1 discloses a method for producing beta zeolite using faujasite-type zeolite, which is zeolite having pores with 12-membered oxygen rings similar to beta-type zeolite, as Si source and Al source. there is In this production method, by using zeolite having a pore structure close to that of beta-type zeolite as the Si source and Al source, Si and Al are supplied to the seed crystal while maintaining the pore structure close to that of beta-type zeolite, This seed crystal grows to produce beta zeolite.

However, in these production methods, if beta zeolite having a SiO ₂ /Al ₂ O ₃ molar ratio of 15 or more is to be synthesized, only a part of the beta zeolite used as the seed crystal remains, and the remaining beta zeolite The crystallinity of the synthesized zeolite is low because the type zeolite is also dissolved by alkali.

On the other hand, in the synthesis of zeolite, in order to obtain a zeolite with a high SiO ₂ /Al ₂ O ₃ molar ratio, it is necessary to increase the SiO ₂ /Al ₂ O ₃ molar ratio in the reaction slurry, or M ₂ O / SiO ₂ molar It is known to lower the ratio (M is an alkali metal). However, in the conventional beta-type zeolite production method that does not use OSDA, a reaction slurry having a high SiO ₂ /Al ₂ O ₃ molar ratio is used in advance, or a reaction slurry having a low M ₂ O/SiO ₂ molar ratio is used in advance. For this reason, a large amount of zeolite with a crystal system other than beta-type zeolite is produced as a by-product, and amorphous silica-alumina is produced without seed crystals growing, so the finally obtained beta-type zeolite crystallinity is reduced. Thus, in the conventional method for producing beta zeolite without using OSDA, it is difficult to produce beta zeolite with a high SiO ₂ /Al ₂ O ₃ molar ratio, high crystallinity, and few by-products. Have difficulty. In addition, the conventional production method not using OSDA has the same problem with CHA-type zeolite.

On the other hand, in the production method of the present invention, by gradually changing the composition of the reaction slurry during the heat treatment, beta zeolite with a high SiO ₂ /Al ₂ O ₃ molar ratio, high crystallinity, and few by-products can be synthesized. The zeolite production method of the present invention that changes the composition of the reaction slurry can be applied not only to beta zeolite but also to production methods for conventionally known zeolites such as CHA zeolite.

Specifically, in the production method of the present invention, the SiO ₂ /Al ₂ O ₃ molar ratio of the reaction slurry is adjusted to is gradually increased, or the M ₂ O/SiO ₂ molar ratio is gradually decreased, and this composition change results in a SiO ₂ /Al ₂ O ₃ molar ratio of 15 or more, high crystallinity, and a by-product It is possible to synthesize beta-type zeolite with less In addition, by this composition change, it is possible to synthesize a CHA-type zeolite having a SiO ₂ /Al ₂ O ₃ molar ratio of 8 or more, high crystallinity, and few by-products.

Thus, in the production method of the present invention, the SiO ₂ /Al ₂ O ₃ molar ratio of the reaction slurry is adjusted in the initial stage of the reaction to a range in which zeolite is easily formed, and as the heat treatment progresses, the SiO ₂ /Al ₂ O ₃ molar ratio increases. By gradually changing the composition of the reaction slurry to a range where the ratio is high and zeolite is difficult to form, it is possible to finally synthesize even zeolite with a high SiO ₂ /Al ₂ O ₃ molar ratio.

In addition, in the production method of the present invention, the M ₂ O / SiO ₂ molar ratio is changed from a range in which zeolite is easily generated to a range in which zeolite is difficult to generate by gradually decreasing this molar ratio. A zeolite with a high SiO ₂ /Al ₂ O ₃ molar ratio can be synthesized. By lowering the M ₂ O/SiO ₂ molar ratio, Si in the reaction slurry is promoted to be incorporated as a zeolite component, resulting in a zeolite with a high SiO ₂ /Al ₂ O ₃ molar ratio.

In addition, a zeolite with high crystallinity can be obtained by the production method of the present invention. In the production method of the present invention, zeolite is produced and grown starting from a range in which zeolite is easily produced, so that zeolite becomes highly crystalline in the initial stage of the reaction, and zeolite is grown by changing the composition of the reaction slurry. This high crystallinity is maintained for a long time, resulting in a highly crystalline zeolite.

Each step of the manufacturing method of the present invention will be described in detail below.
[Reaction slurry preparation step]
In this step, a zeolite serving as a seed crystal, a zeolite whose crystal system is different from that of the seed crystal (hereinafter also referred to as a zeolite different from the seed crystal), an alkali source, and water are mixed to prepare a reaction slurry. As the zeolite to be the seed crystal, it is preferable to use a zeolite of the same crystal system as the zeolite to be finally obtained. For example, to synthesize beta zeolite, beta zeolite is used as a seed crystal. A conventionally known beta-type zeolite can be used as the zeolite serving as the seed crystal. For example, beta zeolite synthesized by a production method not using OSDA may be used, and beta zeolite synthesized by a production method using OSDA may be used.

When synthesizing CHA-type zeolite, CHA-type zeolite can be used as a seed crystal. The CHA-type zeolite can be synthesized without using the CHA-type zeolite as seed crystals. When a CHA-type zeolite is used as a seed crystal, it may be a CHA-type zeolite synthesized by a production method that does not use OSDA, or a CHA-type zeolite synthesized by a production method that uses OSDA.

The zeolite to be the seed crystal preferably has a molar ratio of Si to Al in the range of 5≦SiO ₂ /Al ₂ O ₃ ≦100 in terms of SiO ₂ /Al ₂ O ₃ . Furthermore, when beta-type zeolite is used as the zeolite serving as the seed crystal, the molar ratio of Si to Al is preferably in the range of 10≦SiO ₂ /Al ₂ O ₃ ≦30. Beta zeolite with a molar ratio of Si to Al of less than 10 is not preferable as a seed crystal. In addition, when beta zeolite with a molar ratio of Si to Al higher than 30 is used, beta zeolite may undergo a phase transition to zeolite with a different crystal system, such as MFI zeolite or mordenite zeolite, during heat treatment. I don't like it. When CHA-type zeolite is used as the seed crystal zeolite, the molar ratio of Si to Al is preferably in the range of 4≦SiO ₂ /Al ₂ O ₃ <10.

As the zeolite different from the seed crystal, it is preferable to use a crystalline zeolite having a pore structure similar to that of the seed crystal. For example, when beta-type zeolite having pores of 12-membered oxygen rings is used as a seed crystal, faujasite-type zeolite (also referred to as FAU-type zeolite) having pores of 12-membered oxygen rings is used as the seed crystal. are preferably used as different zeolites. By using a zeolite having a pore structure close to that of a seed crystal in this way, by-products other than the finally obtained zeolite are reduced. In addition, FAU-type zeolite can also be used as a zeolite different from seed crystals when synthesizing CHA-type zeolite.

The zeolite different from the seed crystal preferably has a molar ratio of Si to Al in the range of 4≦SiO ₂ /Al ₂ O ₃ ≦100 in terms of SiO ₂ /Al ₂ O ₃ . Specifically, when synthesizing beta-type zeolite using FAU-type zeolite as a zeolite different from the seed crystal, the molar ratio of Si to Al is within the range of 10≦SiO ₂ /Al ₂ O ₃ ≦60. Preferably. When FAU zeolite having a molar ratio of Si to Al within this range is used, impurities other than the finally obtained zeolite are reduced, presumably because the FAU zeolite is less likely to break during heat treatment. Further, when CHA-type zeolite is synthesized using FAU-type zeolite as a zeolite different from the seed crystal, the molar ratio of Si to Al is in the range of 4≦SiO ₂ /Al ₂ O ₃ <10. preferable. Since it is necessary to decompose the FAU-type zeolite into nanoparts, it is preferable that the molar ratio between Si and Al is low.

As an alkali source, a compound containing a conventionally known alkali metal M such as Na or K can be used. For example, when synthesizing beta zeolite, it is preferable to use a compound containing Na. As the compound containing Na, for example, a compound easily dissolved in water such as sodium hydroxide, sodium carbonate, sodium nitrate, etc. is preferable, and sodium hydroxide is particularly preferable. These alkali sources vary depending on the type of zeolite to be synthesized. For example, when synthesizing CHA-type zeolite, it is preferable to use a compound containing K as the alkali source.

For example, when synthesizing beta zeolite with a molar ratio of Si to Al of 15 or more, the composition of the reaction slurry is preferably within the following range. When a reaction slurry having a composition within this range is used, beta zeolite is likely to be produced.
20≦SiO ₂ /Al ₂ O ₃ ≦60
0.22≦M ₂ O/SiO ₂ ≦0.3
10≦H ₂ O/SiO ₂ ≦30

Further, when synthesizing a CHA-type zeolite in which the molar ratio of Si to Al is in the range of 5≦SiO ₂ /Al ₂ O ₃ <10, the composition of the reaction slurry is preferably within the following range. CHA-type zeolite is likely to be produced when a reaction slurry having a composition within this range is used.
5≦SiO ₂ /Al ₂ O ₃ <10
0.15≦M ₂ O/SiO ₂ ≦0.25
20≦H ₂ O/SiO ₂ ≦40

The amount of zeolite to be seed crystals contained in the reaction slurry is preferably in the range of 1 to 30 mol % based on the amount of Si contained in the reaction slurry. For example, when the reaction slurry contains 1 mol of Si, it is preferable that 0.01 to 0.3 mol of Si is derived from the seed crystal. Specifically, when preparing the reaction slurry, the amount of Si derived from the seed crystal is 0.01 to 0.01 with respect to the total Si amount of the amount of zeolite used as the seed crystal and the amount of zeolite different from the seed crystal. The amount to be charged may be determined so as to be in the range of 0.3 mol.

If the amount of zeolite to be used as seed crystals is too small, the yield of the zeolite finally obtained is lowered, and by-products and the like may be produced, which is not preferred. On the other hand, if the amount of seed crystals is too large, the amount of zeolite obtained is less than the amount of zeolite used as seed crystals charged, which is not preferable.

The amount of zeolite different from the _seed crystals is adjusted to fall within the ranges of the _SiO2 / _Al2O3 molar ratio, the _M2O / _SiO2 molar ratio and the _H2O / _SiO2 molar ratio of the aforementioned reaction slurry. be.

[Heat treatment process]
The reaction slurry is heat-treated. The heating temperature of the reaction slurry is preferably in the range of 80°C ≤ temperature of reaction slurry ≤ 180°C, more preferably in the range of 100°C ≤ temperature of reaction slurry ≤ 160°C. If the temperature of the reaction slurry is too low, it takes a long time to grow zeolite as seed crystals, resulting in low economic efficiency. Also, if the temperature of the reaction slurry is too high, by-products may be produced, which is not preferable. This heat treatment is preferably carried out for about 1 to 200 hours, depending on the temperature of the reaction slurry.

When the temperature of the reaction slurry is less than 100°C, the heat treatment may be performed while the reaction vessel is open. is preferred. In addition, it is preferable to use an autoclave as a reaction vessel for the heat treatment (hydrothermal treatment) performed in a sealed reaction vessel.

Additional slurry is gradually added to the reaction slurry during heat treatment, and seed crystals grow from a composition that facilitates the growth of seed crystals (SiO ₂ /Al ₂ O ₃ molar ratio, M ₂ O/SiO ₂ molar ratio, etc.). Gradually change the composition of the reaction slurry to a composition that is difficult to remove.

For example, when synthesizing a beta zeolite having a molar ratio of Si to Al of 15 or more, an additional slurry having a higher SiO ₂ /Al ₂ O ₃ molar ratio than the reaction slurry is added to the reaction slurry during heat treatment. to gradually increase the SiO ₂ /Al ₂ O ₃ molar ratio of the reaction slurry, or add an additional slurry with a lower M ₂ O/SiO ₂ molar ratio than the reaction slurry to the reaction slurry during heat treatment. to gradually lower the M ₂ O/SiO ₂ molar ratio of the reaction slurry. If the M ₂ O/SiO ₂ molar ratio is lowered, the SiO ₂ /Al ₂ O ₃ molar ratio does not need to be changed.

When synthesizing beta-type zeolite, the composition of the reaction slurry after adding the additional slurry is preferably within the following range.
10≦SiO ₂ /Al ₂ O ₃ ≦60
0.1≦M ₂ O/SiO ₂ <0.22

When synthesizing a CHA-type zeolite in which the molar ratio of Si and Al is in the range of 5≦SiO ₂ /Al ₂ O ₃ <10, additional slurry is added to the reaction slurry during heat treatment to change the composition of the reaction slurry. is changed, for example, the SiO ₂ /Al ₂ O ₃ molar ratio is gradually increased, or the M ₂ O/SiO ₂ molar ratio is gradually decreased. If the M ₂ O/SiO ₂ molar ratio is lowered, the SiO ₂ /Al ₂ O ₃ molar ratio does not need to be changed.

When synthesizing a CHA-type zeolite, the composition of the reaction slurry after addition of the additional slurry is preferably within the following range.
5≦SiO ₂ /Al ₂ O ₃ <10
0.1≦M ₂ O/SiO ₂ <0.15

For both beta-type zeolite and CHA-type zeolite, the range of composition for producing zeolite with high crystallinity and few by-products is limited, and zeolite with low crystallinity tends to be obtained outside the above composition range.

The additional slurry can be prepared using the same raw materials as the reaction slurry. It is preferable to adjust the content of raw materials contained in the additional slurry so that the composition of the reaction slurry after addition of the additional slurry is within the above range. The raw material for the additional slurry may be prepared using a material other than the raw material for the reaction slurry.

The additional slurry is preferably added to the reaction slurry little by little over at least 1 hour to gradually change the composition of the slurry. If the additional slurry is added to the reaction slurry in a short period of time, the composition in the reaction slurry changes abruptly, so that by-products may be generated and the crystallinity of the finally obtained zeolite may decrease. I don't like it. It is not preferable to perform a two-step synthesis in which an additional slurry is added to the reaction slurry after heat treatment and heat treatment is performed again, because by-products are produced (for example, Comparative Example 3).

The zeolite contained in the heat-treated reaction slurry can be separated from the reaction slurry using conventionally known methods such as filtration, centrifugation, and drying. In addition, unreacted raw material components remaining in the zeolite can be removed by washing the zeolite with water, an acid solution, an alkaline solution, or the like before performing these separation operations. These operations may be performed as required. However, if a zeolite other than the target zeolite is produced as a by-product, it is difficult to separate it by these operations.

The production method of the present invention may include a step of ion-exchanging the zeolite obtained by the production method of the present invention. Beta-type zeolite, CHA-type zeolite, and the like can exhibit different functionality by substituting various elements for the ion-exchange sites of each zeolite. For example, when part of the ion exchange sites of beta-type zeolite or CHA-type zeolite is replaced with Cu or Fe, the function as an exhaust gas purifying catalyst is exhibited. As for the ion exchange method, ion exchange can be performed by a conventionally known method. For example, a method of immersing zeolite in a solution containing ions to be ion-exchanged can be used.

[Slurry pulverization process]
In the present invention, a slurry pulverization step may be provided in the reaction slurry preparation step. That is, after preparing a raw material slurry by mixing a zeolite as a seed crystal, a zeolite different from the seed crystal, and water, this raw material slurry is pulverized into a pulverized slurry (referred to as a slurry pulverization step), and this pulverization A step of adding an alkalinity source to the slurry to prepare a reaction slurry can be included. By including this slurry pulverization step, the crystallinity of the finally obtained zeolite can be further enhanced.

In the slurry pulverization step, zeolite serving as seed crystals, zeolite different from the seed crystals, and water are mixed to prepare a raw slurry, and then the raw slurry is pulverized to obtain zeolite serving as seed crystals in the slurry. and zeolite different from the seed crystals are finely dispersed, and the finely dispersed zeolite particles are aggregated again after pulverization, and the zeolite particles that will be the seed crystals are incorporated into the aggregates of the zeolite different from the seed crystals. Re-agglomerates in a state of sagging are formed.

A zeolite with even higher crystallinity can be obtained by adding an alkali source to a slurry containing such reaggregates to form a reaction slurry and subjecting this to heat treatment. The alkalinity source can be added before pulverization, but is preferably added after pulverization. For example, when synthesizing beta-type zeolite, if an alkali source is added before pulverization, the heat generated locally by pulverization may dissolve a portion of the zeolite whose alkali is different from that of the seed crystal. It becomes difficult to form the reaggregate.

In the slurry pulverization step, in addition to forming the reagglomerate, it is also important to destroy the zeolite structure different from the seed crystal to some extent. The growth of the seed crystal can be further promoted by supplying the zeolite to be the seed crystal in a state in which the zeolite different from the seed crystal is broken to some extent. The degree of destruction of the zeolite different from the seed crystal can be calculated from the diffraction pattern obtained by X-ray diffraction measurement of the zeolite different from the seed crystal.

Specifically, among the peaks included in this diffraction pattern, the top three peaks with the highest intensity are selected, and the sum of these peak intensities (intensity obtained by subtracting the background value from the maximum peak value) is obtained. can be compared before and after pulverization, and the degree of pulverization can be determined based on the difference. For example, the sum of the peak intensities before pulverization is H ₀ , the sum of the peak intensities after pulverization is H, and the structure retention ratio is obtained from the following formula, and the degree of pulverization can be determined.
Structural maintenance rate [%] = H/H ₀ × 100

In the slurry pulverization step, pulverization is preferably carried out until the zeolite different from the seed crystal has a structure retention rate of 15% to 40%, which further improves the crystallinity of the finally obtained zeolite. However, if the zeolite different from the seed crystal is pulverized to a state where the structure retention rate is close to 0%, the structure of the zeolite different from the seed crystal will be excessively collapsed, and the growth rate of the zeolite that will be the seed crystal will decrease. I don't like it because there is

As a method for pulverizing the raw material slurry, a conventionally known method can be used as long as the method can pulverize the slurry as it is. For example, the raw material slurry can be pulverized using a bead mill, sand mill, ball mill, or the like. When using a ball mill or a bead mill, it is preferable to grind using zirconia beads, which have high grinding efficiency. The diameter of the beads depends on the grain size of the seed crystals contained in the raw material slurry and the grain size of the zeolite different from the seed crystals, but beads with a diameter of 0.5 to 5 mm can be used.

In the slurry pulverization step, it is preferable to pulverize the slurry until the median diameter does not fluctuate. As the zeolite serving as the seed crystals contained in the slurry and the zeolite different from the seed crystals are pulverized, the median diameter of the slurry becomes smaller. When the median diameter of the slurry reaches a certain value, the median diameter does not fluctuate any more, so this median diameter should be used as an index for pulverization. When the pulverization of the slurry is completed in such a state, the zeolite that becomes the seed crystals pulverized in the slurry and the zeolite different from the seed crystals start to re-aggregate, and the seed crystals in the aggregates of the zeolite different from the seed crystals. It is possible to obtain a reaggregate in which the zeolite is incorporated.

Whether or not this reaggregate is generated is determined by using a laser diffraction/scattering particle size distribution analyzer and comparing the median diameters when ultrasonic treatment is performed and when ultrasonic treatment is not performed. be able to. For example, when re-aggregates are formed, ultrasonic treatment loosens the aggregates and reduces the median diameter. On the other hand, when no reaggregate is generated, the median diameter does not change even if the ultrasonic treatment is performed.

EXAMPLES The production method of the present invention will be specifically described below by way of examples. In addition, the manufacturing method of the present invention is not limited to the following examples. In these examples, intermediates in each step and final The obtained zeolite was evaluated.

[X-ray diffraction measurement]
The obtained zeolite was subjected to X-ray diffraction measurement under the following conditions to confirm the type of zeolite.
<X-ray diffraction measurement conditions>
Equipment: MiniFlex (manufactured by Rigaku Corporation)
Operation axis: 2θ/θ
Radiation source: CuKα
Measurement method: Continuous type Voltage: 40 kV
Current: 15mA
Start angle: 2θ=5°
End angle: 2θ=50°
Sampling width: 0.020°
Scan speed: 10.000°/min
<Judgment Criteria>
The type of zeolite obtained was determined from the X-ray diffraction pattern obtained by the above measurement. For example, when all of the X-ray diffraction peaks attributed to Miller indices (101), (205), and (302) were present, it was determined to be beta zeolite. Note that the position of the peak of the X-ray diffraction pattern may contain an error of about ±1°. Furthermore, the presence or absence of by-products was determined from this X-ray diffraction pattern. For example, when a peak attributed to mordenite was confirmed, it was assumed that mordenite was produced as a by-product.
In the case of CHA-type zeolite, the X-ray diffraction patterns obtained by the above measurements are (100), (200), (20-1), (21-1), (211), (3-1-1 ), (310), and (3-1-2), it was judged to have a chabazite structure (CHA).

[Measurement of composition]
For the obtained zeolite, the molar ratio of Si to Al was measured under the following conditions.
<Method for measuring molar ratio between Si and Al>
The Si and Al contents of the obtained zeolite were measured under the following conditions. The content of each component was calculated as % by mass in terms of oxide. Also, the content of each component was converted into a molar ratio to calculate the SiO ₂ /Al ₂ O ₃ molar ratio.
<Si, Al content measurement>
Measurement method: ICP emission spectrometer: ICP730-ES (manufactured by VARIAN Co., Ltd.)
Sample dissolution: acid dissolution

[Evaluation of crystallinity]
Crystallinity of the obtained zeolite was evaluated under the following conditions.
<X-ray diffraction measurement conditions>
Equipment: MiniFlex (manufactured by Rigaku Corporation)
Operation axis: 2θ/θ
Radiation source: CuKα
Measurement method: Continuous type Voltage: 40 kV
Current: 15mA
Start angle: 2θ=5°
End angle: 2θ=50°
Sampling width: 0.020°
Scan speed: 10.000°/min
<Crystalline-BEA>
From the X-ray diffraction pattern obtained by the above X-ray diffraction measurement, the height of the peak attributed to the Miller index (302) of beta zeolite was determined, and the crystallinity was determined by the following equation.
Crystallinity [%] = H/H _R × 100
H: Peak height of beta zeolite obtained in Examples _HR : Peak height of beta zeolite (HSZ-920NHA) manufactured by Tosoh Corporation <Crystallinity-CHA>
Website of the International Zeolite Society (http://www.iza-online.org/synthesis/) or "WERIFIED SYNTHESES OF ZEOLITIC MATERIALS" edited by H.Robson, K.P.Lillerud XRD diagram: published in 2001, 2nd edition , pp. 123-125.
This standard substance and the produced zeolite were subjected to X-ray diffraction measurement under the following conditions. The crystallinity (relative crystallinity) of the zeolite was obtained from each obtained X-ray diffraction pattern based on the following formula.
From the X-ray diffraction pattern obtained by the X-ray diffraction measurement, the total height of each peak attributed to the Miller indices (100), (20-1), and (3-1-1) is obtained, Relative crystallinity was determined by the formula.
Crystallinity [%] = H/H _R × 100
H: Total height of each of the above peaks of the zeolite obtained in Examples _HR : Total height of each of the above peaks of the standard substance

[Measurement of median diameter]
About the intermediate of each process, the median diameter was measured on condition of the following.
<Median diameter measurement>
Measuring device: HORIBA LA950V2 (manufactured by HORIBA, Ltd.)
Standard: Volume standard Dispersant: Sodium hexametaphosphate aqueous solution Refractive index: 1.465
Ultrasonic treatment: 1 minute (0 if no ultrasonic treatment)

[Structural maintenance rate]
A zeolite different from the seed crystal contained in the pulverized slurry was evaluated for its structure retention rate under the following conditions.
<X-ray diffraction measurement conditions>
Equipment: MiniFlex (manufactured by Rigaku Corporation)
Operation axis: 2θ/θ
Radiation source: CuKα
Measurement method: Continuous type Voltage: 40 kV
Current: 15mA
Start angle: 2θ=5°
End angle: 2θ=50°
Sampling width: 0.020°
Scan speed: 10.000°/min
<Structural maintenance rate>
Zeolites different from the seed crystals used in the examples were subjected to X-ray diffraction measurement under the above conditions. The top three peaks with the highest intensity were selected from the obtained diffraction pattern, and the sum H ₀ of these peak intensities (the intensity obtained by subtracting the background value from the maximum peak value) was determined. A powder obtained by drying the pulverized slurry was also measured in the same manner to determine the sum H of the peak intensities. Using the determined H ₀ and H, the structural maintenance rate was calculated from the following equation.
Structural maintenance rate [%] = H/H ₀ × 100

[Example 1]
[Preparation of FAU-type zeolite]
0.168 kg of an aqueous sodium aluminate solution having an Al ₂ O ₃ concentration of 22% by mass and a Na ₂ O concentration of 17% by mass was added with stirring to 1.35 kg of an aqueous sodium hydroxide solution having an NaOH concentration of 21.65% by mass to dissolve, Cool to 30°C. This solution was added with stirring to 1.361 kg of an aqueous sodium silicate solution having an SiO ₂ concentration of 24% by weight and an Na ₂ O concentration of 7.7% by weight. The composition of the solution at this time was as follows in terms of molar ratio in terms of oxide. Then, this solution was allowed to stand at 30° C. for 15 hours to prepare an aluminosilicate solution.
_Na2O / _{Al2O3 =} 16
_SiO2 / _{Al2O3 =} 15
_H2O / _Al2O3 = ₃₃₀

22.78 kg of sodium silicate aqueous solution with _SiO concentration of 24% by mass and Na O concentration of 7.7% by mass, 5.66 kg of water and SiO concentration of 30% by mass silica sol ₍ manufactured by Nikki _Shokubai Kasei Co., Ltd.: Cataloid SI-30: average particle 18.97 kg of a diameter of 10 nm) and 2.88 kg of the above aluminosilicate solution were added and mixed with stirring. To this, 10.03 kg of an aqueous sodium aluminate solution having an Al ₂ O ₃ concentration of 22 mass % and a Na ₂ O concentration of 17 mass % was added, and the mixture was stirred and aged at room temperature for 3 hours to prepare a mixed hydrogel slurry. The composition of the mixed hydrogel slurry at this time was as follows in terms of molar ratio in terms of oxide.
_Na2O / _Al2O3 = _2.80
SiO2 / _Al2O3 = _8.70
H2O / _{Al2O3 =} 108

60.3 kg of the mixed hydrogel slurry was hydrothermally treated in a crystallization tank at 95° C. for 35 hours. Then, it was cooled to 70° C. and filtered to obtain 29.5 kg of Na—Y zeolite cake. The obtained Na--Y zeolite cake was further washed, filtered and dried to prepare Na--Y zeolite.

5000 g of an aqueous solution containing 500 g of Na—Y type zeolite and 280 g of ammonium sulfate was heated to 80° C., ion-exchanged with stirring for 2 hours, filtered, washed, dried, and calcined at 550° C. for 5 hours. Further, the operations of ion exchange, filtration, washing, and drying were performed twice under the above conditions to obtain 0.95(NH ₄ ) ₂ O.0.05Na ₂ O.Al ₂ O _3.5SiO with an NH ₄ ion exchange rate of 95%. ₂ zeolite (also called NH ₄₍₉₅₎ Y-type zeolite) was prepared.
Then, water was added to the NH _{4 (95)} Y-type zeolite to adjust the water content to 50% by mass. An ultra-stable FAU zeolite was prepared by filling a container with water-adjusted NH _{4 (95)} Y zeolite and steaming at 600° C. for 2 hours.
1067 g of sulfuric acid having a concentration of 25% by mass was added dropwise to 500 g of this ultra-stable FAU zeolite for 0.5 hour to carry out a dealuminization treatment to prepare an FAU zeolite with SiO ₂ /Al ₂ O ₃ =30. The median diameter of this FAU-type zeolite was 7.4 μm. This FAU-type zeolite was used as a zeolite different from the seed crystal.

[Reaction slurry preparation step]
840 g of pure water, 300 g of the FAU-type zeolite as a zeolite different from the seed crystal, and 60 g of beta-type zeolite as a seed crystal (product of Tosoh Corporation: HSZ-920NHA, SiO ₂ /Al ₂ O ₃ molar ratio: 18, median diameter 8 .0 μm) were mixed to prepare a slurry. The molar ratio of Si and Al in this slurry was 27 in terms of SiO ₂ /Al ₂ O ₃ .

Using a slurry pulverizing bead mill (LMZ015, manufactured by Ashizawa Fine Tech Co., Ltd.), this slurry was wet-pulverized until the FAU-type zeolite had a structure retention rate of 20%. The conditions for this wet pulverization were zirconia beads of 1.0 mm, a peripheral speed of 10 m/s, and a bead filling amount of 85% of the volume of the vessel.

86 g of NaOH having a concentration of 48% by mass and 464 g of pure water were added to 450 g of the pulverized slurry to obtain a reaction slurry. The SiO ₂ /Al ₂ O ₃ molar ratio of this reaction slurry was 27, the Na ₂ O/SiO ₂ molar ratio was 0.25, and the H ₂ O/SiO ₂ molar ratio was 22.

[Heat treatment process]
The entire amount of the above reaction slurry was charged into an autoclave and hydrothermally treated at 140° C. for 48 hours, and additional slurry was added during this heat treatment.
The additional slurry was prepared by mixing 178 g of the reaction slurry obtained in the reaction slurry preparation step and 157 g of pure water to obtain the additional slurry of Example 1 in Table 1 . This additional slurry was added to the reaction slurry during heat treatment over 10 hours such that the reaction slurry during heat treatment had a Na ₂ O/SiO ₂ molar ratio of 0.18 and a H ₂ O/SiO ₂ molar ratio of 21. added in small portions. After the addition of the additional slurry was completed, further hydrothermal treatment was carried out at 140° C. for 48 hours.

After the hydrothermal treatment, the reaction slurry was taken out, filtered, washed and dried to obtain zeolite. The obtained zeolite was evaluated based on the aforementioned X-ray diffraction measurement method, composition measurement method, and crystallinity evaluation method. Table 1 shows the results.

[Example 2: Additional slurry addition time change]
A zeolite was prepared in the same manner as in Example 1, except that the additional slurry was added to the reaction slurry during heat treatment for 3 hours and the slurry was not pulverized. The obtained zeolite was evaluated in the same manner as in Example 1. Table 1 shows the results.

[Example 3: CHA-type zeolite]
[Reaction slurry preparation]
660 g of sulfuric acid having a concentration of 25% by mass was added dropwise to 500 g of the ultra-stable FAU-type zeolite obtained by the method described in Example 1 for 0.5 hours to carry out a dealuminization treatment, whereby SiO ₂ /Al ₂ O ₃ = An 8.9 FAU-type zeolite was prepared. The median diameter of this FAU-type zeolite was 7.4 μm. This was used as a zeolite different from the seed crystal.

[Reaction slurry preparation step]
840 g of pure water, 300 g of the above FAU zeolite as a zeolite different from the seed crystal, and the homepage of the International Zeolite Society as the seed crystal (http://www.iza-online.org/synthesis/) or "WERIFIED SYNTHESES OF ZEOLITIC CHA-type zeolite synthesized based on the Chabazite synthesis method described in H.Robson, K.P.Lillerud XRD diagram: published in 2001, 2nd edition, pp. (SiO ₂ /Al ₂ O ₃ molar ratio: 4.8) to prepare a slurry. The molar ratio of Si and Al in this slurry was 8.2 in terms of SiO ₂ /Al ₂ O ₃ .

[Slurry pulverization]
Using a bead mill, this slurry was wet pulverized until the FAU-type zeolite had a structure retention rate of 20%. The conditions for this wet pulverization were zirconia beads of 1.0 mm, a peripheral speed of 10 m/s, and a bead filling amount of 85% of the volume of the vessel.

34 g of KOH having a concentration of 85% and 510 g of pure water were added to 456 g of the pulverized slurry to obtain a reaction slurry. The SiO ₂ /Al ₂ O ₃ molar ratio of this reaction slurry was 8.2, the K ₂ O/SiO ₂ molar ratio was 0.17, and the H ₂ O/SiO ₂ molar ratio was 27.

[Heat treatment process]
The entire amount of the above reaction slurry was charged into an autoclave and hydrothermally treated at 150° C. for 48 hours, and additional slurry was added during this heat treatment.
The additional slurry was prepared by mixing 165 g of the reaction slurry obtained in the reaction slurry preparation step, 152 g of pure water, and 5 g of KOH having a concentration of 85%. This additional slurry was added in small portions to the reaction slurry during heat treatment for 8 hours such that the reaction slurry during heat treatment had a K ₂ O/SiO ₂ molar ratio of 0.14 and a H ₂ O/SiO ₂ molar ratio of 27. was added sequentially over a period of time. After the addition of the additional slurry was completed, further hydrothermal treatment was carried out at 150° C. for 48 hours.

After the hydrothermal treatment, the reaction slurry was taken out, filtered, washed and dried to obtain zeolite. The obtained zeolite was evaluated based on the aforementioned X-ray diffraction measurement method, composition measurement method, and crystallinity evaluation method. Table 1 shows the results.

[Comparative Example 1: No zeolite different from seed crystals, no addition of additional slurry]
SiO ₂ : Al ₂ O ₃ : Na ₂ O: H ₂ O ₌ 27.0: 1.0: 4.8: 561.6. Product: Cataloid SI-30: average particle size 10 nm) 590 g, 51 g of sodium aluminate aqueous solution with Al ₂ O ₃ concentration of 22% by mass and Na ₂ O concentration of 17% by mass, 87 g of 48% NaOH solution, and 606 g of pure water. After that, the mixture was stirred at room temperature for 1 hour to obtain a slurry. This slurry was hydrothermally treated at 140° C. for 48 hours. After the hydrothermal treatment, the slurry was taken out, filtered, washed and dried to obtain zeolite. The obtained zeolite was evaluated in the same manner as in Example 1. Table 1 shows the results.

[Comparative Example 2: No addition of additional reaction solution]
633 g of the reaction slurry of Example 1 and a concentration of 48 mass so as to have a composition of SiO ₂ : Al ₂ O ₃ : Na ₂ O: H ₂ O = 27.0: 1.0: 4.8: 561.6 % NaOH and 616 g of pure water were mixed and then stirred at room temperature for 1 hour. After stirring, this slurry was charged into an autoclave and hydrothermally treated at 140° C. for 48 hours. After the hydrothermal treatment, the slurry was taken out, filtered, washed and dried to obtain zeolite. The obtained zeolite was evaluated in the same manner as in Example 1. Table 1 shows the results.

[Comparative Example 3: Two-step synthesis]
A slurry was obtained by mixing 450 g of the reaction slurry of Example 1, 86 g of NaOH having a concentration of 48% by mass, and 464 g of pure water. The slurry had a Na ₂ O/SiO ₂ molar ratio of 0.245 and a H ₂ O/SiO ₂ molar ratio of 22. This slurry was put into an autoclave and hydrothermally treated at 140° C. for 48 hours (first time). After the slurry was hydrothermally treated, it was cooled to room temperature.

Next, 178 g of the reaction slurry of Example 1 and 157 g of pure water were mixed to prepare an additional slurry. The total amount of this additional slurry and the total amount of the hydrothermally treated slurry were mixed in an autoclave and hydrothermally treated (second time) at 140° C. for 48 hours. At this time, the Na ₂ O/SiO ₂ molar ratio of the slurry after adding the additional slurry was 0.18, and the H ₂ O/SiO ₂ molar ratio was 21. In Comparative Example 3, the composition of the slurry changes at once in the second heat treatment. After the hydrothermal treatment, the slurry was taken out, filtered, washed and dried to obtain zeolite. The obtained zeolite was evaluated in the same manner as in Example 1. Table 1 shows the results.

[Comparative Example 4: No addition of additional reaction solution—CHA-type zeolite]
_{458 g} of the _{reaction slurry} of Example ₃ and After mixing 27 g of KOH and 515 g of pure water, the mixture was stirred at room temperature for 1 hour. After stirring, this reaction slurry was charged into an autoclave and hydrothermally treated at 150° C. for 48 hours. After the hydrothermal treatment, the slurry was taken out, filtered, washed and dried to obtain zeolite. The obtained zeolite was evaluated in the same manner as in Example 3. Table 1 shows the results.

As shown in Table 1, the beta zeolite obtained by the production method of the present invention (Examples 1 and 2) has a SiO ₂ /Al ₂ O ₃ molar ratio of 15 or more and high crystallinity. Less is. On the other hand, in Comparative Examples 1 and 2 in which no additional slurry was added during the heat treatment, although the SiO ₂ /Al ₂ O ₃ molar ratio was high, only beta-type zeolite with low crystallinity due to the presence of an amorphous silica-alumina compound was mixed. I didn't get it. In Comparative Example 3, in which no additional slurry was added during the first heat treatment, and additional slurry was added after the second heat treatment and reheated, the SiO ₂ /Al ₂ O ₃ molar ratio was high and the crystallinity was high. However, mordenite is formed as a by-product due to the rapid change in the composition of the reaction slurry. As for CHA-type zeolite, in Example 3 according to the production method of the present invention, CHA-type zeolite having a SiO ₂ /Al ₂ O ₃ molar ratio of 15 or more, high crystallinity, and no by-products can be obtained. . On the other hand, for CHA-type zeolite, Comparative Example 4, in which no additional slurry was used, had a high SiO ₂ /Al ₂ O ₃ molar ratio and no by-products, but extremely low crystallinity.

Claims (6)

A method for producing a zeolite without using an organic structure-directing agent,
a reaction slurry preparation step of preparing a reaction slurry by mixing a beta-type or chabazite-type zeolite as a seed crystal, an FAU-type zeolite whose crystal system is different from that of the seed crystal, an alkali source, and water;
_providing an additional slurry having a higher SiO2 /Al2O3 _molar ratio _than the reaction slurry or an additional slurry having a lower M2O/SiO2 molar ratio than the _{reaction slurry} ;
including a heat treatment step of heating the reaction slurry,
In the heat treatment step, the additional slurry is added to the reaction slurry over at least one hour to increase the SiO ₂ /Al ₂ O ₃ molar ratio of the reaction slurry, or to increase the M ₂ O/SiO ₂ molar ratio. A method for producing zeolite, characterized by lowering In the heat treatment step, the M ₂ O/SiO ₂ molar ratio of the reaction slurry is adjusted from the range of 0.22≦M ₂ O/SiO ₂ ≦0.3 to 0.1≦M ₂ O/SiO ₂ <0. 2. The method for producing zeolite according to claim 1, wherein beta zeolite is synthesized by changing the range of 0.22. In the heat treatment step, the M ₂ O/SiO ₂ molar ratio of the reaction slurry is adjusted from the range of 0.15≦M ₂ O/SiO ₂ ≦0.25 to 0.1≦M ₂ O/SiO ₂ <0. 2. The method for producing a zeolite according to claim 1, wherein the chabazite-type zeolite is synthesized by changing it to the range of 0.15. _3. The method for producing zeolite according to claim 2 , wherein the molar ratio of Si and Al contained in the produced zebeta-type zeolite is 15 or more in terms of _SiO2 /Al2O3 _. The zeolite according to claim 3, wherein the molar ratio of Si and Al contained in the produced chabazite-type zeolite is in the range of 5≦SiO ₂ / Al ₂ O ₃ <10 in terms of SiO ₂ /Al ₂ O ₃ Production method. The reaction slurry preparing step includes mixing a zeolite serving as a seed crystal, a zeolite having a crystal system different from that of the seed crystal, an alkali source, and water to prepare a raw material slurry, and pulverizing the raw material slurry. 6. The method for producing zeolite according to any one of claims 1 to 5 , comprising a slurry pulverization preparation step of obtaining a pulverized slurry, and a step of adding an alkali source to the pulverized slurry to obtain a reaction slurry. .