JP7679603B2 - Method for producing AEI zeolite, catalyst, and adsorbent - Google Patents

Description

The present invention relates to a method for producing AEI zeolite, and to a catalyst and an adsorbent containing the obtained AEI zeolite.

Zeolites have properties such as a molecular sieve effect due to the pores derived from their framework structure, as well as ion exchange ability, catalytic ability, and adsorption ability, and are widely used as adsorbents, ion exchange agents, industrial catalysts, environmental catalysts, etc.
Zeolites carrying metals such as copper are known as catalysts for exhaust gas, and specifically, CHA-type aluminosilicate zeolites and silicoaluminophosphate (SAPO) zeolites have been developed. The designations AEI and CHA are codes stipulated by the International Zeolite Association (IZA) that define the skeletal structure of zeolites.

AEI zeolite has the same pore size as CHA zeolite, but is known to have a structure with higher catalytic activity. AEI zeolite is used, for example, as an SCR (Selective Catalytic Reduction) catalyst. When using zeolite as an SCR catalyst for treating exhaust gas from automobiles, etc., it is thought that a catalyst with a low Si/Al ratio is more suitable for reliable exhaust gas treatment, especially during low-temperature operation such as start-up. This is because in the case of aluminosilicate zeolites, the coordination sites of transition metals, etc., which become active sites, become aluminum sites, so a catalyst with a low Si/Al ratio, which has more active sites, is more advantageous.

Known as a general method for producing AEI zeolite is the method disclosed in Patent Document 1. Specifically, Patent Document 1 discloses that AEI zeolite is obtained by using Y zeolite (framework density: 12.7T/1000 Å ³ ) and colloidal silica as raw materials, adding thereto, for example, DMDMPOH (N,N-dimethyl-3,5-dimethylpiperidinium hydroxide) as an organic structure directing agent (SDA), stirring in the presence of NaOH, and carrying out hydrothermal synthesis for 8 days.
The examples in Patent Document 1 are experiments in which Y-type zeolite was actually used as a raw material and the SDA was changed. Thus, it is currently common knowledge that AEI-type zeolite cannot be synthesized without using Y-type zeolite. This is supported by the statement in, for example, Non-Patent Document 1 that "synthesis was attempted using Al(OH) ₃ as a raw material, but no crystalline oxide was obtained."

Patent Document 2 discloses a method for producing AEI zeolite using inexpensive aluminum nitrate as a raw material, in which aluminum nitrate and TEOS (tetraethyl orthosilicate) are used, mixed with SDA, and then hydrofluoric acid is added to obtain AEI zeolite. The method disclosed in Patent Document 2 uses hydrofluoric acid to produce AEI zeolite with a Si/Al ratio of 200 or more while minimizing the incorporation of Al into the zeolite.

Patent Document 3 discloses a method for producing AEI zeolite having a Si/Al ratio of 50 or less, the method including the steps of preparing a mixture containing a silicon atom raw material, an aluminum atom raw material, an alkali metal atom raw material, an organic structure-directing agent, and water, and hydrothermally synthesizing the mixture obtained in the above step.
This manufacturing method is characterized in that the aluminum atom raw material contains aluminum with a Si content of 20% by weight or less, and the mixture contains zeolite with a framework density of 14T/1000 ^Å3 or more in an amount of 0.1% by weight or more relative to _SiO2 when all of the Si in the mixture is converted into _SiO2 .

U.S. Pat. No. 5,958,370 International Publication No. 2005/063624 JP 2017-81809 A

Chemical,Communications, 48, 8264-8266.

The hydrofluoric acid used in Patent Document 2 is a very dangerous acid, and its use during hydrothermal synthesis at high temperatures is not practical from an industrial standpoint. Furthermore, since Y-type zeolite is expensive, there is a problem in terms of cost when it is used in large quantities, such as in the selective catalytic reduction (SCR) catalyst for NOx contained in exhaust gases from automobiles, etc.
Furthermore, in the method for producing AEI zeolite, as described above, it is considered preferable to lower the Si/Al ratio, but the production methods disclosed in Patent Documents 1 and 2 do not disclose the ability to produce AEI zeolite with a lower Si/Al ratio.

On the other hand, Patent Document 3 does not show that it is possible to obtain an AEI zeolite with a sufficiently low Si/Al ratio and high AEI purity while suppressing the amount of organic structure-directing agent used, which is relatively expensive, and there is room for further improvement.

Therefore, the objective of the present invention is to provide a method for safely and inexpensively producing AEI zeolite with a low Si/Al ratio and high purity.

As a result of intensive research, the present inventors have found that the above-mentioned problems can be solved by mixing and maturing raw materials for zeolite, adding a zeolite containing d6r, which is defined as a composite building unit by the International Zeolite Association (IZA), in its framework, and then carrying out hydrothermal synthesis, thereby completing the present invention described below.
That is, the present invention provides the following [1] to [11].
[1] preparing a composition containing silicon atoms, aluminum atoms, alkali metal atoms, and water;
Aging the composition;
adding a zeolite containing d6r in its framework, which is defined as a composite building unit by the International Zeolite Association (IZA), after the aging;
and hydrothermally synthesizing the composition after the addition of the zeolite.
[2] The method for producing the AEI zeolite described in [1] above, characterized in that the molar ratio calculated as C/B×100 is less than 100%, where "B" is the molar ratio of silicon atoms/aluminum atoms in the solid content of the composition before aging, and "C" is the molar ratio of silicon atoms/aluminum atoms in the solid content of the composition after aging.
[3] The method for producing the AEI zeolite described in [1] or [2] above, characterized in that the aging is carried out by heating.
[4] The method for producing AEI zeolite according to the above [3], characterized in that the heating is carried out at 30 to 180° C. for 10 minutes to 24 hours.
[5] A method for producing AEI zeolite described in any one of [1] to [4] above, characterized in that the molar ratio of silicon atoms/aluminum atoms of the AEI zeolite is 10 or less.
[6] A method for producing an AEI zeolite described in any one of [1] to [5] above, characterized in that amorphous silica is used as the silicon atoms contained in the composition before aging.
[7] The method for producing AEI zeolite described in any one of [1] to [6] above, wherein the silicon atoms contained in the composition before aging do not contain zeolite, or the silicon atoms derived from zeolite contained in the composition before aging are 10 mol% or less relative to the total amount of silicon atoms.
[8] A method for producing an AEI zeolite described in any one of [1] to [7] above, characterized in that the composition after the addition of the zeolite contains an organic structure-directing agent in a molar ratio of 0.01 or more and 1 or less relative to silicon atoms.
[9] A catalyst comprising AEI zeolite produced by the method for producing AEI zeolite according to any one of [1] to [8] above.
[10] The catalyst according to the above [9], which is a reduction catalyst for nitrogen oxides.
[11] An adsorbent comprising AEI zeolite produced by the method for producing AEI zeolite described in any one of [1] to [8] above.

According to the present invention, it is possible to safely and inexpensively produce AEI zeolite with a low Si/Al ratio and high purity.

1 is a chart showing the XRD pattern of the AEI zeolite synthesized in Example 1.

The following describes in detail the embodiments of the present invention. However, the following description is an example (representative example) of the embodiments of the present invention, and the present invention is not limited to these contents in any way.

The method for producing AEI zeolite of the present invention (hereinafter, may be referred to as "the present production method") is characterized by comprising a step of preparing a composition containing silicon atoms, aluminum atoms, alkali metal atoms, and water, an aging step of aging the composition, an addition step of adding, after the aging, a zeolite containing d6r defined by the International Zeolite Association (IZA) as a composite building unit in its framework, and a hydrothermal synthesis step of hydrothermally synthesizing the composition after the addition of the zeolite.
In the following description, the composition to be subjected to aging may be referred to as the "pre-aging composition." Furthermore, the composition to be subjected to hydrothermal synthesis after the addition of the zeolite may be referred to as the "pre-reaction composition" or the "aged composition."

<Preparation of Composition>
In this production method, the pre-aging composition containing silicon atoms, aluminum atoms, alkali metal atoms and water can be prepared by any method. Here, silicon atoms, aluminum atoms and alkali metal atoms are used as silicon atom raw materials, aluminum atom raw materials and alkali metal atom raw materials, respectively. However, raw materials containing each may be used, or compounds containing multiple raw materials such as compounds containing silicon atoms and aluminum atoms may be used. In this specification, unless otherwise specified, the silicon atom raw material and the aluminum atom raw material refer to the silicon atom raw material and the aluminum atom raw material used in the pre-reaction composition other than the zeolite added after aging. In the following description, the zeolite containing d6r in the framework added to the pre-aging composition may be simply referred to as "d6r zeolite".

The method for preparing the pre-aged composition is not particularly limited, but from the viewpoint of making it easier to dissolve each raw material uniformly, it is preferable to add the silicon atom raw material and the aluminum atom raw material to the alkaline solution. Here, the alkaline solution is preferably an aqueous solution of the alkali metal atom raw material (aqueous alkali metal solution).

When an organic structure-directing agent is used in the present production method, the organic structure-directing agent may be contained in the pre-ripening composition. In this case, the organic structure-directing agent is preferably contained in the alkaline solution.
The raw materials used in the preparation of the pre-ripening composition may be mixed at the same time, or may be mixed in any order or amount. When the raw materials are mixed in parts, they may be mixed in two or more parts, or may be mixed before and after ripening. The organic structure-directing agent may be added at any time before the hydrothermal synthesis, and may be added before ripening as described above, may be added after ripening, or may be added both before and after ripening.

However, since it is considered that the aluminum atom raw material is easily incorporated into the solid content by aging, it is preferable to charge a large amount of the aluminum atom raw material before aging. Specifically, it is preferable that the aluminum atoms contained in the aluminum atom raw material are charged before aging in an amount of preferably 50 mol % or more, more preferably 70 mol % or more, and particularly preferably 90 mol % or more, based on the total amount of the aluminum atom raw material used.
In addition, for the silicon atom raw material, since aging makes it easier to form a zeolite precursor with a high aluminum atom content, it is preferable to lower the Si/Al molar ratio before aging. Specifically, the Si/Al molar ratio before aging is preferably 10 or less, more preferably 8 or less, and particularly preferably 7 or less.
Here, unless otherwise specified, the total amount used means the total amount of aluminum atoms or the total amount of silicon atoms contained in the pre-reaction composition other than d6r zeolite, and the same applies hereinafter.

The raw materials used in the production method of the present invention will be described in more detail below.
(Silicon atom source)
The silicon atom source is a compound having a silicon atom. The silicon atom source is preferably a silicon-containing compound other than Y-type zeolite, and more preferably a compound other than zeolite.
The silicon atom raw material is preferably an amorphous silicon compound, since it is thought to be easily mixed with the aluminum atom raw material and to be easily dissolved in the aging step so as to have a Si/Al ratio suitable for crystallization of AEI zeolite. As the amorphous silicon compound, amorphous silica such as colloidal silica, amorphous silica, fumed silica, and sodium silicate; trimethylethoxysilane, tetraethylorthosilicate, and aluminosilicate gel can be used. These may be used alone or in any combination of two or more kinds in any ratio.
Among these, amorphous silica is preferred because it is easily dissolved and inexpensive. Also, colloidal silica, trimethylethoxysilane, tetraethylorthosilicate, and aluminosilicate gel are preferred because they are easily mixed uniformly with other raw materials and are particularly easily dissolved in water. Among the above, colloidal silica is more preferred as the silicon atom raw material.

It is preferable that the silicon atom raw material contains a large proportion of amorphous silica, which is easily soluble and inexpensive. Therefore, it is preferable that the silicon atoms of the amorphous silica are 50 mol % or more, and more preferably 70 mol % or more, of the total amount of silicon atoms contained in the silicon atom raw material (silicon atom raw material used in the unaged composition), and it is most preferable that the entire amount of the silicon atom raw material is amorphous silica.

In addition, since the amount of d6r zeolite added after aging is usually small, as described below, it is preferable that the silicon atom source used in the pre-reaction composition also contains a large amount of amorphous silica. Specifically, the silicon atoms of the amorphous silica are preferably 50 mol% or more, and more preferably 70 mol% or more, of the total amount of silicon atoms contained in the silicon atom source used in the pre-reaction composition.

As described above, the present production method can produce AEI zeolite using inexpensive amorphous silica as a silicon atom raw material. That is, the silicon atom raw material of the pre-aging composition does not contain zeolite, or the silicon atoms derived from zeolite in the pre-aging composition are preferably 10 mol% or less, more preferably 5 mol% or less, based on the total amount of silicon atoms, and further preferably the zeolite does not contain silicon atoms.
Similarly, the silicon atom raw material of the pre-aging composition preferably does not contain Y-type zeolite, or the Y-type zeolite content is 10 mol% or less, more preferably 5 mol% or less, relative to the total amount of silicon atoms, and even more preferably does not contain silicon atoms as Y-type zeolite.

The amount of d6r zeolite added after aging is preferably 10% by mass or less, more preferably 8% by mass or less, and particularly preferably 5% by mass or less, based on the total amount of silicon atom raw material including d6r zeolite. The amount of d6r zeolite is preferably 1% by mass or more, and more preferably 3% by mass or more.

(Aluminum atom source)
The aluminum atom source is a compound containing aluminum atoms. The aluminum atom source is preferably a compound containing aluminum other than Y-type zeolite, more preferably a compound containing aluminum other than zeolite.
The aluminum atom raw material is preferably a compound that is easily soluble in water. Also, it is preferable that the compound is well mixed with the silicon atom raw material and is easily soluble so that the Si/Al ratio is suitable for crystallization of AEI zeolite in the aging process. Therefore, the aluminum atom raw material is preferably amorphous aluminum hydroxide, aluminum hydroxide having a gibbsite structure, aluminum hydroxide having a bayerite structure, aluminum nitrate, aluminum sulfate, aluminum oxide, sodium aluminate, boehmite, pseudo-boehmite, aluminum alkoxide, etc. These may be used alone or in any ratio and combination of two or more.
Among these, particularly preferred are amorphous aluminum hydroxide, aluminum hydroxide having a gibbsite structure, and aluminum hydroxide having a bayerite structure.
It is also preferable to use an amorphous aluminum atom source as the aluminum atom source, and among the above, amorphous aluminum hydroxide is particularly preferable.

It is preferable to use the aluminum atom raw material so that the molar ratio of the total amount of silicon atoms to the total amount of aluminum atoms in the pre-reaction composition (Si/Al molar ratio) is 2.5 or more and 10 or less. The above-mentioned Si/Al ratio is more preferably 3 or more, and even more preferably 5 or more, while on the other hand, more preferably 8 or less, and even more preferably 7 or less. By setting the above-mentioned Si/Al molar ratio in the above-mentioned preferred range, it becomes easier to obtain AEI zeolite with the desired above-mentioned Si/Al ratio.

In addition, since aging makes it easier to form a zeolite precursor with a higher aluminum atom content, it is preferable that the Si/Al molar ratio of the composition before aging is low. And, it is preferable that the molar ratio of silicon atoms to aluminum atoms in the composition before aging (Si/Al molar ratio, hereinafter also referred to as "feed ratio (A)") is also within the same range as the above Si/Al molar ratio.

(alkali metal atom)
The alkali metal atom used in the present production method is not particularly limited, and any known alkali metal used in the synthesis of zeolite can be used, but it is preferably at least one selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium. By containing these alkali metal atoms, the crystallization can proceed more easily, and by-products (impurity crystals) are less likely to be generated. As described above, the alkali metal atom is used as an alkali metal atom raw material.

The alkali metal atoms particularly preferably contain sodium atoms. The reason is as follows. That is, when zeolite is used, for example, as an adsorbent or catalyst, the alkali metal atoms incorporated into the crystal structure during the synthesis of the zeolite may be removed from the crystals by ion exchange. In this case, in order to simplify the alkali metal atom removal process, it is preferable that the alkali metal atoms used in the synthesis are sodium atoms. Therefore, it is preferable that the alkali metal atoms contained in the alkali metal atom raw material are sodium atoms, and it is even more preferable that they are 50 mol % or more, more preferably 80 mol % or more, and it is particularly preferable that substantially all of them are sodium atoms.

Of course, the alkali metal atoms contained in the alkali metal atom raw material may be less than 50 mol% sodium atoms. In this case, the main alkali metal atoms contained in the pre-reaction composition are preferably, for example, potassium atoms, cesium atoms, or a mixture of potassium atoms and cesium atoms.

The alkali metal atoms are preferably contained in the pre-reaction composition as alkali metal ions. As the alkali metal atom raw material, inorganic acid salts such as hydroxides, oxides, sulfates, nitrates, phosphates, chlorides, and bromides of the above alkali metal atoms, and organic acid salts such as acetates, oxalates, and citrates can be used. The alkali metal atom raw materials may be used alone or in any combination of two or more types in any ratio.

When an organic structure directing agent is used, as described below, it is believed that the alkali metal atom raw material can easily form a crystal structure by facilitating the coordination of the organic structure directing agent with the aluminum atom in a suitable state. The molar ratio of alkali metal atoms to the organic structure directing agent in the pre-reaction composition is preferably 0.5 or more, more preferably 1.0 or more, even more preferably 2.0 or more, particularly preferably 3.0 or more, especially preferably 4.0 or more, and most preferably 6.0 or more. On the other hand, it is preferably 20 or less, more preferably 15 or less, even more preferably 12 or less, especially preferably 10 or less, especially preferably 8.0 or less, and most preferably 6.0 or less.

(water)
From the viewpoint of facilitating crystal formation, the amount of water, in terms of a molar ratio to silicon atoms other than d6r zeolite contained in the pre-reaction composition, is usually 5 or more, preferably 7 or more, more preferably 9 or more, and even more preferably 10 or more. In order to reduce the amount of waste liquid treatment and obtain a cost reduction effect, the amount of water, in terms of a molar ratio to silicon atoms other than d6r zeolite contained in the pre-reaction composition, is usually 50 or less, preferably 40 or less, more preferably 30 or less, and even more preferably 25 or less.

(Zeolite containing d6r in the framework)
In this production method, as described above, a zeolite containing d6r in the framework is added to the aged composition. The added zeolite serves as a seed crystal in the synthesis of AEI zeolite. Note that d6r means d6r (double 6-membered ring) defined as a composite building unit by the International Zeolite Association (IZA).
Zeolites containing d6r in the framework specifically include AEI, AFT, AFX, CHA, EAB, ERI, GME, KFI, LEV, LTL, LTN, MOZ, MSO, MWW, OFF, SAS, SAT, SAV, SZR, and WEN. Among these, more preferably AEI, AFT, AFX, CHA, ERI, KFI, LEV, LTL, MWW, and SAV, even more preferably AEI, AFT, and CHA, even more preferably CHA and AEI, and particularly preferably CHA.
The zeolite containing d6r in its framework to be added to the composition may be used alone or in any combination of two or more kinds in any ratio.

The zeolite used in this manufacturing method may be either uncalcined, that is, not calcined after hydrothermal synthesis, or calcined, that is calcined after hydrothermal synthesis. Uncalcined zeolite is preferred because it is less soluble in alkali and more likely to function as a crystal nucleus. However, depending on the composition of the composition or temperature conditions, etc., if uncalcined zeolite is less soluble, calcined zeolite may be used.

The amount of d6r zeolite added is preferably 0.1% by mass or more based on SiO ₂ when it is assumed that all silicon atoms contained in the pre-reaction composition other than d6r zeolite are SiO ₂ , and in order to proceed with the reaction more smoothly, it is more preferably 0.5% by mass or more, even more preferably 2% by mass or more, particularly preferably 3% by mass or more, and most preferably 4% by mass or more. In addition, since zeolite is expensive, the amount of zeolite added is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 8% by mass or less, and particularly preferably 6% by mass or less, from the viewpoint of reducing costs.

(Organic structure directing agent)
The pre-reaction composition preferably contains an organic structure-directing agent, since this makes it easier to obtain a high-purity AEI zeolite.
As the organic structure directing agent (also called "template". Hereinafter, the organic structure directing agent may be referred to as "SDA"), various known substances such as tetraethylammonium hydroxide (TEAOH) and tetrapropylammonium hydroxide (TPAOH) can be used. For example, the following substances can be used as the organic structure directing agent.

Examples include N,N-diethyl-2,6-dimethylpiperidinium cation, N,N-dimethyl-9-azoniabicyclo[3.3.1]nonane cation, N,N-dimethyl-2,6-dimethylpiperidinium cation, N-ethyl-N-methyl-2,6-dimethylpiperidinium cation, N,N-diethyl-2-ethylpiperidinium cation, N,N-dimethyl-2-(2-hydroxyethyl)piperidinium cation, N,N-dimethyl-2-ethylpiperidinium cation, N,N-dimethyl-3,5-dimethylpiperidinium cation, N-ethyl-N-methyl-2-ethylpiperidinium cation, 2,6-dimethyl-1-azonium[5.4]decane cation, and N-ethyl-N-propyl-2,6-dimethylpiperidinium cation. The organic structure directing agent is preferably a nitrogen-containing organic structure directing agent or a phosphorus-containing organic structure directing agent, and as a nitrogen-containing organic structure directing agent, N,N-dimethyl-3,5-dimethylpiperidinium cation is more preferable, and N,N-dimethyl-3,5-dimethylpiperidinium hydroxide is even more preferable.

Also, as the phosphorus-containing organic structure directing agent, materials such as tetrabutylphosphonium and diphenyldimethylphosphonium can be used. However, since phosphorus compounds may generate diphosphorus pentoxide, a harmful substance, when the synthesized zeolite is calcined to remove SDA, nitrogen-containing organic structure directing agents are preferred.
These organic structure-directing agents may be used alone or in any combination of two or more kinds in any ratio.

The pre-reaction composition preferably contains an organic structure-directing agent in a molar ratio of 0.01 or more and 1 or less relative to the silicon atoms contained in the pre-reaction composition. By setting the content of the organic structure-directing agent within the above range, it is possible to reduce the amount of expensive organic structure-directing agent used, and it is easy to obtain a high-purity AEI zeolite at a low cost. In addition, it is easy to reduce the Si/Al molar ratio of the AEI zeolite.
From the above viewpoints, the content of the organic structure directing agent is more preferably 0.02 or more, even more preferably 0.04 or more, and even more preferably 0.06 or more, and is more preferably 0.5 or less, even more preferably 0.3 or less, even more preferably 0.2 or less, and particularly preferably 0.15 or less.

(Other ingredients)
In this production method, in addition to the above aluminum atom raw material, silicon atom raw material, alkali metal atom raw material, zeolite containing d6r in the framework, water, and organic structure directing agent, an auxiliary agent that serves as a component for assisting the synthesis of zeolite, for example, an acid component that promotes the reaction, an additive such as a metal stabilizer such as polyamine, etc. may be added at any step as necessary to prepare a pre-reaction composition. Also, as described later, a metal such as copper that acts as a catalyst may be added during hydrothermal synthesis.

In addition, in the present production method, an alkaline earth metal may be added during the hydrothermal synthesis. It is generally known that the addition of an alkaline earth metal to a zeolite improves the hydrothermal resistance. In the present production method, an AEI zeolite can also be produced by adding a compound containing an alkaline earth metal to the pre-reaction composition.
The alkaline earth metal may be magnesium, calcium, strontium, barium, etc., preferably magnesium or calcium, and most preferably calcium. The alkaline earth metal can be usually supplied in the form of a compound, such as an oxide, hydroxide, sulfide, etc., but is not particularly limited thereto, and is preferably added in the form of a hydroxide.

<Aging>
In the present production method, the pre-aging composition obtained as described above is aged. In the present production method, the molar ratio of silicon atoms/aluminum atoms in the solid content of the pre-aging composition is reduced by aging, which is presumed to result in the production of high-purity AEI zeolite. The principle by which the molar ratio is reduced by aging and the principle by which high-purity AEI zeolite is obtained are not clear, but are presumed to be as follows.
The aluminum atom raw material added to the alkali metal aqueous solution is easily dissolved. Here, when the silicon atom raw material is added, it reacts with the aluminum atoms in the liquid to form an aluminosilicate gel. The aluminosilicate gel is a colloid with water as a dispersion medium, and is a solid that forms a cross-linked structure by silicon and aluminum. At this time, some of the aluminum atoms do not react with the silicon atom raw material, and are not included in the aluminosilicate gel and are dissolved in the liquid. Therefore, the Si/Al ratio of the aluminosilicate gel becomes higher than the added feed ratio. And, when the composition in which the Si/Al ratio is higher than the feed ratio, that is, the Si/Al ratio is deviated from the feed ratio, is hydrothermally synthesized, impurities other than the AEI type are also crystallized, and it is considered that the purity of the AEI type is reduced.
On the other hand, it is believed that by carrying out aging, silicon atoms in the solid (aluminosilicate gel) dissolve into the liquid phase and aluminum atoms in the liquid phase are incorporated into the solid, lowering the Si/Al ratio of the solid to a composition suitable for obtaining an AEI type, thereby enabling a high-purity AEI type to be obtained.

The aging is preferably carried out so that the molar ratio of silicon atoms to aluminum atoms (Si/Al molar ratio) in the solid content of the composition is as follows:
If the molar ratio of silicon atoms to aluminum atoms (Si/Al molar ratio) in the solid content in the composition before aging is "B" and the molar ratio of silicon atoms to aluminum atoms (Si/Al molar ratio) in the solid content in the composition after aging is "C", the molar ratio calculated as C/B x 100 is preferably less than 100%, more preferably 90% or less, even more preferably 80% or less, and particularly preferably 74% or less, from the viewpoint of easily obtaining a high-purity AEI zeolite.
On the other hand, by increasing the ratio of the above molar ratio, it is possible to prevent an increase in the silicon atom raw material that does not contribute to zeolite production due to dissolution, and to increase the yield of AEI zeolite. Therefore, from the viewpoint of the yield of AEI zeolite, the ratio of the molar ratio calculated by C/B×100 is preferably 30% or more, more preferably 40% or more, and particularly preferably 50% or more.
For the same reason, the Si/Al molar ratio (C) relative to the charge ratio (A) in the composition before aging (C/A×100) is preferably 110% or less, more preferably 100% or less, while the ratio is preferably 20% or more, more preferably 30% or more, particularly preferably 40% or more, and particularly preferably 50% or more.
The molar ratio of silicon atoms to aluminum atoms in the solid content of the composition can be obtained by filtering the composition at room temperature (25° C.) to separate the solid content from the liquid content, and then analyzing the solid content by X-ray fluorescence spectrometry (hereinafter referred to as XRF) to measure the molar ratio of silicon atoms to aluminum atoms (Si/Al molar ratio).

The maturation is preferably carried out by heating since the maturation proceeds more quickly.
Heating is preferably performed at a low temperature in that impurities are less likely to crystallize during aging. On the other hand, heating is preferably performed at a high temperature in that aging is likely to proceed in a short time. Specifically, the composition is heated to a temperature of preferably 180° C. or less, more preferably 140° C. or less, and particularly preferably 120° C. or less for aging. On the other hand, the heating temperature is preferably 30° C. or more, and more preferably 40° C. or more. The temperature may be constant during aging, or may be changed stepwise or continuously.

The maturation time is not particularly limited. A short time is preferable from the viewpoint of production efficiency, but a long time is preferable from the viewpoint of purity and uniformity. When maturation is performed at high temperature or high pressure, maturation is likely to occur in a short time. The maturation time is preferably 10 minutes or more, more preferably 30 minutes or more, and particularly preferably 1 hour or more. On the other hand, 48 hours or less is preferable, more preferably 36 hours or less, and particularly preferably 24 hours or less.
The aging is preferably carried out under normal pressure because the equipment required is simple. The aging temperature, time, and pressure are interrelated, but it is particularly preferable to carry out the aging by heating at 30 to 180° C. for 10 minutes to 24 hours.
The maturation is preferably carried out with stirring since the raw materials are easily homogenized. The stirring method is not particularly limited.

<Addition of Zeolite>
In this production method, after the pre-aging composition is aged, a zeolite containing d6r in its framework is added. In this production method, by adding d6r zeolite to the composition after aging, it becomes easier to safely and inexpensively produce AEI zeolite with a low Si/Al ratio and high purity. The d6r zeolite added to the composition serves as seed crystals for obtaining AEI zeolite.
The zeolite containing d6r in its framework is added after aging and before hydrothermal synthesis, which will be described later. The method of adding the zeolite is not particularly limited, but it may be added to the composition in a heated state after aging, or it may be added after the composition is cooled after aging. After the addition, the composition is usually stirred.

<Hydrothermal synthesis>
In this production method, the pre-reaction composition after the addition of zeolite is subjected to hydrothermal synthesis. AEI zeolite is synthesized by hydrothermal synthesis. The hydrothermal synthesis is usually performed by placing the composition after the addition of zeolite in a pressure-resistant container and maintaining it at a predetermined temperature under self-generated pressure or under gas pressure that does not inhibit crystallization, while stirring, rotating or rocking the container, or in a stationary state.

The hydrothermal synthesis is usually carried out at 120° C. or higher. The hydrothermal synthesis is usually carried out at 230° C. or lower, preferably 220° C. or lower, more preferably 200° C. or lower, and even more preferably 190° C. or lower. The reaction time is not particularly limited, but is usually 2 hours or more, preferably 3 hours or more, more preferably 5 hours or more, and particularly preferably 1 day or more, and is usually 30 days or less, preferably 10 days or less, more preferably 7 days or less, and even more preferably 5 days or less. The reaction temperature may be constant during the reaction, or may be changed stepwise or continuously.
By carrying out the hydrothermal synthesis under the above conditions, the yield of the target AEI zeolite is improved and it becomes difficult to produce zeolites of other types than the target, which is preferable.

<Recovery of AEI zeolite>
After the hydrothermal synthesis, the product AEI zeolite is separated from the composition after the hydrothermal synthesis (hydrothermal synthesis reaction liquid). The obtained zeolite usually contains alkali metal atoms in the pores. In addition, when an organic structure-directing agent is used, the organic structure-directing agent is usually contained in the pores. Hereinafter, the substances contained in the pores of the zeolite after the hydrothermal synthesis, such as the organic structure-directing agent and the alkali metal, may be referred to as "organic structure-directing agent, etc.", and the zeolite containing this in the pores may be referred to as "SDA, etc.-containing zeolite."
The method for separating the SDA-containing zeolite from the hydrothermal synthesis reaction liquid is not particularly limited, but typically includes filtration, decantation, direct drying, and the like.

The SDA-containing zeolite separated and recovered from the hydrothermal synthesis reaction liquid is washed with water, dried, and then calcined or otherwise treated to remove the organic structure-directing agent, etc., used during the production.
When AEI zeolite is used as a catalyst (including a catalyst support) or an adsorbent, it is usually used after removing the organic structure-directing agent, etc.

Methods for removing organic structure-directing agents from SDA-containing zeolite include liquid-phase treatment using an acidic solution or a chemical solution containing an organic structure-directing agent decomposition component, ion exchange treatment using resin, etc., and thermal decomposition treatment, and these treatments may be used in combination. Usually, the organic structure-directing agents contained in the zeolite can be removed by methods such as calcining at a temperature of 300 to 1000°C in air or an oxygen-containing inert gas or in an inert gas atmosphere, or extraction with an organic solvent such as an ethanol aqueous solution. From the viewpoint of manufacturability, removal of organic structure-directing agents by calcination is preferred. In this case, the calcination temperature is preferably 400°C or higher, more preferably 450°C or higher, and even more preferably 500°C or higher, and is preferably 900°C or lower, more preferably 850°C or lower, and even more preferably 800°C or lower. Nitrogen, etc. can be used as the inert gas.

<Recycling of separated liquid containing organic structure directing agent>
The separated liquid remaining after separating and recovering the AEI zeolite from the hydrothermal synthesis reaction liquid usually contains unreacted organic structure-directing agent, etc. Therefore, the separated liquid may be recycled. The recycling method is not particularly limited, but for example, the missing silicon atom raw material, aluminum atom raw material, organic structure-directing agent, water, etc. may be added to the separated liquid containing the unreacted organic structure-directing agent to prepare a pre-aging composition. Then, as described above, the obtained pre-aging composition may be subjected to aging, addition of zeolite, and hydrothermal synthesis in this order to produce the AEI zeolite.

<AEI type zeolite>
The AEI zeolite produced by this production method (hereinafter, sometimes referred to as "AEI zeolite of the present invention") is a code that specifies the skeletal structure of zeolite, as defined by the International Zeolite Association (IZA), and indicates an AEI structure. The structure is characterized by X-ray diffraction data. However, when actually measuring a produced zeolite, the intensity ratio and peak position of each peak are affected by the growth direction of the zeolite, the ratio of constituent elements, adsorbed substances, the presence of defects, the drying state, etc., and therefore, the values obtained are not completely the same as the parameters of the AEI structure specified by the IZA, and a margin of about 10% is allowed.
Major peaks observed in X-ray diffraction of AEI zeolite, for example, when CuKα radiation is used as the radiation source, include the peak of the 110 plane at 2θ=9.5°±0.2°, the peaks of the 202 and −202 planes (which are very close and often overlap) at 2θ=16.1°±0.2°, the peak of the 022 plane at 16.9°±0.2°, and the peak of the 310 plane at 20.6°±0.2°.

The zeolite obtained by this manufacturing method is a zeolite as defined by the International Zeolite Association (IZA), but is preferably an aluminosilicate zeolite. An aluminosilicate zeolite contains at least oxygen (O), aluminum (Al), and silicon (Si) as atoms that constitute the framework structure, and some of these atoms may be replaced with other atoms (Me). The other atoms Me may be one type or two or more types. The preferred Me is an element belonging to the third or fourth period of the periodic table.

The total amount of Si atoms and Al atoms contained in AEI zeolite is preferably 70% by mass or more, and more preferably 80% by mass or more, based on the total amount of Al atoms, Si atoms, and Me atoms. On the other hand, the total amount of Si atoms and Al atoms contained in the zeolite is preferably 99% by mass or less.

This manufacturing method makes it possible to obtain AEI zeolite with high purity and a low Si/Al molar ratio without using Y zeolite and while reducing the amount of organic structure-directing agent used.

Specifically, the molar ratio of silicon atoms to aluminum atoms (Si/Al molar ratio) in the AEI zeolite of the present invention is preferably 10 or less. Since the AEI zeolite has a low Si/Al molar ratio, the number of active sites increases, and therefore, for example, when the AEI zeolite of the present invention is used as an SCR catalyst, it is possible to have high purification performance for exhaust gases containing nitrogen oxides. From the viewpoint of increasing the number of active sites and improving the catalytic performance, the Si/Al molar ratio is more preferably 8 or less, even more preferably 6.5 or less, and most preferably 5 or less.
In addition, by reducing the amount of Al in the zeolite framework, the hydrothermal durability of the zeolite is improved, and even when the zeolite comes into contact with a gas containing water vapor, structural destruction due to elimination of Al in the framework is unlikely to occur. From these viewpoints, the Si/Al ratio is preferably 2 or more, more preferably 3 or more, particularly preferably 4 or more, and particularly preferably 4.5 or more.

As the purity of AEI zeolite increases, its performance, such as catalytic activity, improves when used as a catalyst. Therefore, the purity of AEI zeolite is preferably 83% or more, more preferably 85% or more, even more preferably 88% or more, and particularly preferably 90% or more. The higher the purity of AEI zeolite, the better, with the upper limit being 100%.

The purity of AEI zeolite can be calculated by the following procedure. First, the by-product content in the zeolite is calculated. The by-product content can be obtained from the following formula (1) using an XRD pattern obtained by XRD measurement using CuKα radiation as a radiation source.
By-product content (%)
= I (by-product) / (I (AEI) + I (by-product)) × 100 (1)

In the above formula, I(AEI) is the intensity of the main peak of AEI zeolite. Note that the main peak is the most intense peak among the XRD peaks that characterize each zeolite, and in AEI zeolite, it is typically the peak at 2θ=9.5°±0.2°.
I (by-product) is the intensity of the main peak of the by-product zeolite. I (by-product) is the intensity of the XRD peak that characterizes the structure of the by-product zeolite. For example, when the by-product zeolite is a MOR type zeolite, I (by-product) is the intensity of the XRD peak having a peak top at 2θ=6.5±0.1°. When the by-product zeolite is a GME type zeolite, I (by-product) is the intensity of the XRD peak having a peak top at 2θ=7.5±0.1°. In addition, when there are two or more types of by-products, I (by-product) is calculated by adding up the peak intensities.

From the by-product content (%) calculated as above, the purity of the AEI zeolite can be calculated from the following formula (2).
Purity of AEI zeolite (%)=100−by-product content (%) (2)

The AEI zeolite produced by the present production method can be used after converting the alkali metal atom raw material, or the alkali metal moiety derived from the alkali metal atom contained in the aluminum atom raw material, the silicon atom raw material, the organic structure directing agent, and the d6r zeolite, to H type or NH4 _type , and a known technique can be used for this purpose. For example, this can be done by treating with an ammonium salt such as _NH4NO3 or _NaNO3 or _an acid such as hydrochloric acid, usually at room temperature to 100°C, followed by washing with water.

<Improvement of heat resistance by post-loading of metal>
As a method for improving the hydrothermal resistance of the AEI zeolite obtained by the present production method, a metal may be supported on the AEI zeolite after hydrothermal synthesis or on the catalyst after supporting a metal (e.g., Cu) for use as a catalyst described later. Examples of the metal to be supported include Mg, Ca, Sr, La, Pr, B, Zr, Ce, and Fe. These metals may be used alone or in any ratio and combination of two or more. In addition, a salt of these metals may be added to the gel before the hydrothermal synthesis of the AEI zeolite to produce an AEI zeolite containing a metal. In this case, inorganic acid salts such as sulfates, phosphates, nitrates, chlorides, and bromides of transition metals, organic acid salts such as acetates, oxalates, and citrates, and organometallic compounds such as pentacarbonyl and ferrocene are usually used. Among these salts, inorganic acid salts and organic acid salts are preferred from the viewpoint of solubility in water. The effect of supporting these metals is believed to be that the metals are coordinated to the Al in the zeolite framework, providing a protection effect against water vapor.

<Applications of AEI zeolite>
The use of the AEI zeolite of the present invention is not particularly limited, but it is preferably used as a catalyst, an adsorbent, a separation material, etc. Among them, it is preferable to use it as a catalyst or an adsorbent. AEI zeolite is particularly preferably used as a catalyst for purifying exhaust gases of automobiles, etc. In addition, AEI zeolite is also preferably used as an adsorbent for purifying exhaust gases of automobiles, etc.

[catalyst]
When the AEI zeolite of the present invention is used as a catalyst, the catalyst contains the AEI zeolite produced by the above-mentioned production method. The catalyst is used as various industrial catalysts and environmental catalysts, but is preferably used as a reduction catalyst for nitrogen oxides.
The nitrogen oxide reduction catalyst can be used in exhaust purification systems and the like, and can be used, for example, as an exhaust gas treatment catalyst capable of purifying nitrogen oxides contained in a wide variety of exhaust gases discharged from various diesel engines for diesel automobiles, gasoline automobiles, stationary power generation, ships, agricultural machinery, construction machinery, motorcycles, and aircraft, boilers, gas turbines, etc. The catalyst containing the AEI zeolite of the present invention can exhibit high purification performance for exhaust gases containing nitrogen oxides by lowering the Si/Al molar ratio as described above.
The exhaust gas may contain components other than nitrogen oxides, such as hydrocarbons, carbon monoxide, carbon dioxide, hydrogen, nitrogen, oxygen, sulfur oxides, and water.

In addition, the exhaust purification system may use known reducing agents such as nitrogen-containing compounds (excluding nitrogen oxides), such as ammonia, urea, hydrazine, ammonium carbonate, ammonium carbamate, ammonium hydrogen carbonate, and ammonium formate, and hydrocarbons.
In an exhaust purification system, a catalyst containing AEI zeolite may be used as a selective catalytic reduction catalyst (SCR catalyst), in which a reducing agent such as ammonia is adsorbed on the SCR catalyst, and nitrogen oxides are selectively reduced by the adsorbed reducing agent.
An exhaust gas purification system using an SCR catalyst has a reducing agent supplying unit that supplies a reducing agent, and the reducing agent is supplied from the reducing agent supplying unit to the SCR catalyst. The reducing agent supplying unit may supply the reducing agent to the SCR catalyst by a known means, for example, by spraying the reducing agent and supplying it to the SCR catalyst. The reducing agent supplied may be ammonia itself, or may be a compound capable of generating ammonia. An example of a compound capable of generating ammonia is urea.

When the AEI zeolite of the present invention is used as a catalyst, it may be used as it is, or AEI zeolite containing a metal may be used as necessary. The metal may be any metal other than Si and Al. For example, transition metals are preferred as metal elements used in SCR catalysts, and among them, it is more preferred to select from the group consisting of iron (Fe), cobalt (Co), palladium (Pd), iridium (Ir), platinum (Pt), copper (Cu), silver (Ag), gold (Au), cerium (Ce), lanthanum (La), praseodymium (Pr), titanium (Ti), zirconium (Zr), etc., with copper (Cu) being even more preferred.

Specific methods for incorporating metals include impregnation and ion exchange in the liquid or solid phase. As described above, metal-containing zeolite may be directly synthesized by adding the metal (either as a simple substance or as a compound) before hydrothermal synthesis. The state of the metal in metal-containing zeolite may be either included in the framework structure or not.

The catalyst containing the AEI zeolite of the present invention can be mixed with a binder, granulated, or molded into a predetermined shape such as a honeycomb. Specifically, for example, the catalyst is mixed with an inorganic binder such as silica, alumina, or clay mineral, or inorganic fibers such as alumina fiber or glass fiber, and then granulated or molded into a predetermined shape such as a honeycomb by an extrusion method or compression method, and then fired to obtain a granular catalyst, honeycomb catalyst, or molded catalyst product.

The catalyst containing the AEI zeolite of the present invention may also be used by applying it to a substrate such as a sheet or honeycomb. Specifically, for example, a method can be used in which the catalyst containing the AEI zeolite of the present invention is mixed with an inorganic binder such as silica, alumina, or clay mineral to prepare a slurry, which is then applied to the surface of a substrate made of an inorganic material such as cordierite, and then fired. Preferably, the catalyst is applied to a substrate having a honeycomb shape, thereby obtaining a honeycomb-shaped honeycomb catalyst coated with the catalyst.

In the above explanation, an inorganic binder is used because an exhaust gas treatment catalyst is used as an example, but it goes without saying that an organic binder may also be used depending on the application and conditions of use.

[Adsorbent]
When the AEI zeolite of the present invention is used as an adsorbent, the adsorbent contains the AEI zeolite produced by the above-mentioned production method.
The adsorbent is preferably used as a nitrogen oxide adsorbent for adsorbing nitrogen oxides, and the nitrogen oxide adsorbent is used, for example, in an exhaust gas purification system.
More specifically, the exhaust gas purification system comprises the above-mentioned nitrogen oxide adsorbent and a nitrogen oxide reduction catalyst, and it is preferable that the nitrogen oxide adsorbent is disposed upstream of the nitrogen oxide reduction catalyst in the exhaust path of the exhaust gas.
The nitrogen oxide reducing catalyst is preferably a selective catalytic reduction catalyst (SCR catalyst) that reduces nitrogen oxides with a reducing agent, and the reducing agent and the reducing agent supply unit for supplying the reducing agent are as described above. As the SCR catalyst, a known SCR catalyst may be a catalyst containing the AEI zeolite of the present invention.

Nitrogen oxide adsorbents normally adsorb nitrogen oxides in exhaust gas when the exhaust gas temperature is in the low temperature range (e.g., below 150°C). When the exhaust gas temperature is in the high temperature range (e.g., 150°C or higher), the nitrogen oxides adsorbed to the adsorbent are released as high-temperature exhaust gas. On the other hand, SCR catalysts are catalysts that can reduce nitrogen oxides with a reducing agent in the high temperature range (e.g., 150°C or higher). Generally, exhaust gas is at a low temperature at the beginning of operation, but becomes hot after a certain amount of time has passed since the start of operation.

Therefore, in an exhaust gas treatment system using the AEI zeolite of the present invention, when low-temperature exhaust gas is discharged and passes through the nitrogen oxide adsorbent, the nitrogen oxides contained in the exhaust gas are adsorbed by the nitrogen oxide adsorbent, thereby reducing the amount of nitrogen oxides in the exhaust gas.
On the other hand, when high-temperature exhaust gas is discharged and passes through the nitrogen oxide adsorbent, the nitrogen oxides are not adsorbed by the nitrogen oxide adsorbent, and the adsorbed nitrogen oxides are desorbed. Therefore, the exhaust gas including the desorbed nitrogen oxides is sent from the nitrogen oxide adsorbent to the SCR catalyst. In the SCR catalyst, the nitrogen oxides contained in the exhaust gas are reduced to nitrogen and the like by a reducing agent. As a result, the exhaust gas treatment system using the AEI zeolite of the present invention is capable of reducing the nitrogen oxides contained in the exhaust gas even when the exhaust gas is at a high temperature.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples as long as they do not exceed the gist of the invention.

[Analysis and Evaluation]
The analysis and performance evaluation of the zeolites obtained in the following Examples and Comparative Examples were carried out by the following methods.

[Powder XRD Measurement]
<Sample preparation>
100 mg of a zeolite sample that had been manually crushed using an agate mortar was set in a sample holder of the same shape so that the sample amount was constant.
<Apparatus specifications and measurement conditions>
The specifications of the powder XRD measuring device and the measuring conditions are as follows.

[Purity of AEI zeolite]
In the XRD pattern obtained by the XRD measurement, the purity of the AEI zeolite was calculated from the intensity of the main peak of the AEI zeolite and the intensity of the main peak of each by-product according to the above-mentioned formulas (1) and (2).

[Measurement of Si/Al ratio by X-ray fluorescence analysis]
The zeolite sample as the standard specimen was dissolved by heating in an alkaline aqueous solution and an aqueous solution of hydrofluoric acid, and the Si/Al ratio was determined by inductively coupled plasma (ICP) emission spectrometry. Then, a calibration curve of the fluorescent X-ray intensity of the analyzed element in the standard specimen and the atomic concentration of the analyzed element was created.
Using this calibration curve, the zeolite obtained in each example was analyzed by X-ray fluorescence analysis (XRF) to determine its Si/Al ratio. The ICP analysis was performed using a Thermo Fisher Scientific device named iCAP7600 Duo. The XRF was performed using a Rigaku device named Supermini200. By this method, the Si/Al molar ratios (B) and (C) in the solid content of the composition and the Si/Al ratio in the zeolite framework were determined.

Example 1
5.9g of water, 1.1g of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (35% by mass, manufactured by Seichem Co., Ltd.) as an organic structure directing agent (SDA), and 0.48g of NaOH (97% by mass, manufactured by Kishida Chemical Co., Ltd.) were mixed, and 0.43g of amorphous Al(OH) ₃ (Al ₂ O ₃ : 54.3% by mass, manufactured by Kyowa Chemical Co., Ltd.) was added and stirred to dissolve, forming a transparent solution. 4.5g of Snowtex 40 (colloidal silica, silica concentration: 40% by mass, manufactured by Nissan Chemical Co., Ltd.) was added thereto and stirred at room temperature (25°C) for 2 hours to obtain a pre-ripening composition. Here, the Si/Al molar ratio (A) was 6.5. The molar ratio of the organic structure directing agent to the silicon atoms contained in the composition was 0.08.
The pre-aging composition was placed in a pressure-resistant container, aged in an oven at 40°C for 4 hours, and then cooled to room temperature. The compositions before and after aging were filtered under reduced pressure for 30 minutes using a glass funnel (Kiriyama Seisakusho, diameter 60 mm) and cellulose filter paper (Kiriyama Seisakusho, diameter 60 mm, thickness 0.21 mm, retention particles 1 μm, model No. 5C) at room temperature (25°C). The Si/Al molar ratio of the solid component obtained was 8.85 before aging (B) and 6.7 after aging (C). The ratio of the Si/Al molar ratio (C) of the solid component after aging to the charge ratio (A) was 103%. 0.1 g of uncalcined CHA-type zeolite (Si/Al molar ratio = 12) was added as seed crystals to the aged composition, and the mixture was stirred for 1 hour to obtain a pre-reaction composition. Here, the amount of zeolite added was 5 mass % based on SiO ₂ on the assumption that all silicon atoms contained in the pre-reaction composition other than zeolite are SiO ₂ .
The pre-reaction composition was placed in a pressure vessel and rotated (15 rpm) in an oven at 180 ° C. for 1 day to carry out hydrothermal synthesis. The reaction solution after the hydrothermal synthesis reaction was cooled and then filtered to recover the produced zeolite. The recovered zeolite was dried at 100 ° C. for 12 hours, and the XRD of the resulting zeolite powder was measured. It was confirmed that AEI type zeolite 1 was synthesized, which shows an XRD pattern with peaks and relative intensities at the positions shown in Table 3 in terms of lattice spacing. The XRD pattern of this zeolite 1 is shown in Figure 1. In Figure 1, the vertical axis is intensity (cps) and the horizontal axis is diffraction angle 2θ (°). The Si/Al ratio of zeolite 1 by XRF analysis was 4.8.

Example 2
Zeolite powder was obtained in the same manner as in Example 1, except that the aging conditions were 40° C. and 6 hours. The compositions before and after aging were filtered, and the Si/Al molar ratios of the solid components obtained were 8.85 before aging (B) and 6.4 after aging (C). The ratio of the Si/Al molar ratio (C) of the solid component after aging to the feed ratio (A) was 98%.
When the XRD of the obtained zeolite powder was measured, it was confirmed that AEI type zeolite 2 was synthesized, which exhibited an XRD pattern having peaks and relative intensities at the positions shown in Table 4 in terms of lattice spacing. The Si/Al ratio of zeolite 2 by XRF analysis was 4.7.

Example 3
Zeolite powder was obtained in the same manner as in Example 1, except that the aging conditions were 80° C. and 2 hours. The compositions before and after aging were filtered, and the Si/Al molar ratios of the solid components obtained were 8.85 before aging (B) and 5.7 after aging (C). The ratio of the Si/Al molar ratio of the solid component after aging (C) to the feed ratio (A) was 87%.
When the XRD of the obtained zeolite powder was measured, it was confirmed that AEI type zeolite 3 was synthesized, which exhibited an XRD pattern having peaks and relative intensities at the positions shown in Table 5 in terms of lattice spacing. The Si/Al ratio of zeolite 3 by XRF analysis was 4.8.

Example 4
Zeolite powder was obtained in the same manner as in Example 1, except that the aging conditions were 120° C. and 1 hour. The compositions before and after aging were filtered, and the Si/Al molar ratios of the solid components obtained were 8.85 before aging (B) and 5.4 after aging (C). The ratio of the Si/Al molar ratio of the solid component after aging (C) to the feed ratio (A) was 82%.
The XRD of the obtained zeolite powder was measured, and it was confirmed that AEI type zeolite 4 was synthesized, which shows an XRD pattern having peaks and relative intensities at the positions shown in Table 6, expressed in lattice spacing. The Si/Al ratio of zeolite 4 by XRF analysis was 4.7.

(Example 5)
Zeolite powder was obtained in the same manner as in Example 1, except that the aging conditions were 120° C. and 24 hours. The compositions before and after aging were filtered, and the Si/Al molar ratios of the solid components obtained were 8.85 before aging (B) and 5.2 after aging (C). The ratio of the Si/Al molar ratio (A) of the solid component after aging to the feed ratio (A) was 79%.
When the XRD of the obtained zeolite powder was measured, it was confirmed that AEI type zeolite 5 was synthesized, which exhibited an XRD pattern having peaks and relative intensities at the positions shown in Table 7 in terms of lattice spacing. The Si/Al ratio of zeolite 5 by XRF analysis was 4.7.

(Comparative Example 1)
The same procedure as in Example 9 of JP 2017-081809 A was carried out to obtain a zeolite powder. Specifically, all raw materials were added and stirred at room temperature for 2 hours to obtain a pre-reaction composition. The Si/Al molar ratio of the solid component obtained by filtering the pre-reaction composition was 11.5, and the ratio of the Si/Al molar ratio of the solid component to the charge ratio (A) was 126%.
The XRD of the obtained zeolite powder was measured, and it was confirmed that AEI type zeolite 6 was synthesized, which shows an XRD pattern with peaks and relative intensities at the positions shown in Table 8 in terms of lattice spacing. The Si/Al ratio of zeolite 7 by XRF analysis was 5.1.

(Comparative Example 2)
Zeolite powder was obtained in the same manner as in Example 1, except that aging was not performed. That is, the seed crystals were added to a pre-aging composition obtained by stirring the raw materials other than the seed crystals at room temperature (25° C.) for 2 hours. The SI/Al molar ratio of the solid component obtained by filtering the pre-reaction composition obtained by mixing the raw materials was 8.85, and the ratio of the Si/Al molar ratio of the solid component to the charge ratio (A) was 136%.
When the XRD of the obtained zeolite powder was measured, it was confirmed that zeolite 7, which is a mixed phase of AEI type and impurities of GME type and MOR type, was synthesized, which shows an XRD pattern having peaks and relative intensities at the positions shown in Table 9 in lattice spacing notation. The Si/Al ratio of zeolite 7 by XRF analysis was 4.8.

(Comparative Example 3)
Zeolite powder was obtained in the same manner as in Example 1, except that seed crystals were added before aging and aging conditions were set at 80°C for 2 hours. The compositions before and after aging were filtered, and the Si/Al molar ratios of the solid components obtained were 8.85 before aging (B) and 5.8 after aging (C). The ratio of the Si/Al molar ratio of the solid component after aging (C) to the feed ratio (A) was 88%.
When the XRD of the obtained zeolite powder was measured, it was confirmed that zeolite 8 was synthesized, which is a mixed phase of AEI type and impurities GME type and MOR type, which show an XRD pattern having peaks and relative intensities at the positions shown in Table 10 in lattice spacing representation. The Si/Al ratio of zeolite 8 by XRF analysis was 4.7.

The results are summarized in Tables 11 and 12.

In Table 11, SDA/Si is the molar ratio of the organic structure directing agent to the silicon atoms contained in the pre-reaction composition. The amount of seed crystals added is the mass% relative to _SiO2 when it is assumed that all silicon (Si) contained in the pre-reaction composition other than the seed crystals is _SiO2 .

In Table 12, the Si/Al molar ratio (B) in Comparative Examples 1 and 2 indicates the Si/Al molar ratio of the pre-reaction composition obtained by mixing the respective raw materials.

From the above examples, it was confirmed that AEI zeolite with low Si/Al and high AEI purity can be obtained by aging a composition containing each raw material, adding d6r zeolite, and then performing hydrothermal synthesis. Here, in each example, since no Y zeolite is used as a raw material other than the seed crystals, and the amount of organic structure-directing agent used is small, it was found that AEI zeolite with low Si/Al and high AEI purity can be produced inexpensively.
In contrast, in Comparative Examples 1 and 2, the step of adding d6r zeolite after aging was not performed, and therefore, when the amount of the organic structure-directing agent used was reduced as in Comparative Example 2, AEI zeolite with a low Si/Al ratio and high AEI purity could not be obtained. Also, it was found that in order to obtain AEI zeolite, it is necessary to use a large amount of an expensive organic structure-directing agent as in Comparative Example 1. Furthermore, it was found from Comparative Example 3 that even if seed crystals are added to the composition before aging, AEI zeolite with a low Si/Al ratio and high purity cannot be obtained.

Claims (11)

preparing a composition comprising silicon atoms, aluminum atoms, alkali metal atoms , an organic structure directing agent , and water;
Aging the composition;
adding a zeolite containing d6r in its framework, which is defined as a composite building unit by the International Zeolite Association (IZA), after the aging;
and hydrothermally synthesizing the composition after the addition of the zeolite. The method for producing AEI zeolite according to claim 1, characterized in that the molar ratio calculated as C/B×100 is less than 100%, where "B" is the molar ratio of silicon atoms/aluminum atoms in the solid content of the composition before aging, and "C" is the molar ratio of silicon atoms/aluminum atoms in the solid content of the composition after aging. The method for producing AEI zeolite according to claim 1 or 2, characterized in that the aging is carried out by heating. The method for producing AEI zeolite according to claim 3, wherein the heating is carried out at 30 to 140 ° C. for 10 minutes to 24 hours. The method for producing AEI zeolite according to any one of claims 1 to 4, characterized in that the molar ratio of silicon atoms/aluminum atoms of the AEI zeolite is 10 or less. The method for producing AEI zeolite according to any one of claims 1 to 5, characterized in that amorphous silica is used as the silicon atoms contained in the composition before aging. The method for producing AEI zeolite according to any one of claims 1 to 6, wherein the silicon atoms contained in the composition before aging do not contain zeolite, or the silicon atoms derived from zeolite contained in the composition before aging are 10 mol% or less based on the total amount of silicon atoms. The method for producing AEI zeolite according to any one of claims 1 to 7, characterized in that the composition after the addition of the zeolite contains an organic structure directing agent in a molar ratio of 0.01 to 1 relative to silicon atoms. The method for producing AEI zeolite according to claim 4, wherein the heating is carried out at 120°C or less, and the silicon atom raw material contains amorphous silica. A method for producing a nitrogen oxide reduction catalyst, comprising using an AEI zeolite produced by the method for producing an AEI zeolite according to any one of claims 1 to 9 . A method for producing an adsorbent, which uses AEI zeolite produced by the method for producing AEI zeolite according to any one of claims 1 to 9 .