JP7794619B2 - Method for producing CHA-type zeolite - Google Patents

Description

This disclosure relates to a method for producing CHA-type zeolite.

CHA-type zeolite is a zeolite with a skeletal structure designated by the Structure Commission of the International Zeolite Association (ISEA), and is used in a variety of catalytic applications, including cracking catalysts and nitrogen oxide reduction catalysts.

Because CHA-type zeolites are sometimes used at high temperatures, they are required to have heat resistance that allows them to maintain catalytic activity even at high temperatures. It is known that the heat resistance of CHA-type zeolites can be improved by subjecting them to steam treatment to remove aluminum from the framework structure (see, for example, Patent Document 1).

Patent No. 6817022

The inventors have been studying the steam treatment performed on CHA-type zeolite and have concluded that, depending on the steam treatment conditions, excessive aluminum may be removed from the framework structure of CHA-type zeolite, causing the crystal structure to become unstable.

The present invention is as set forth in the claims, and the gist of the present disclosure is as follows.
[1] A method for producing CHA-type zeolite, comprising: a crystallization step of crystallizing a composition containing a crystalline silica-alumina source, an alkali source, an organic structure-directing agent, and water; an organic structure-directing agent removal step of removing the organic structure-directing agent contained in the CHA-type zeolite obtained in the crystallization step; and a steam treatment step of contacting the CHA-type zeolite obtained in the organic structure-directing agent removal step with a gas containing water vapor, wherein the water vapor concentration in the gas is 5% by volume or more and less than 50% by volume.
[2] The method for producing a CHA-type zeolite according to [1], wherein the CHA-type zeolite obtained in the organic structure-directing agent removal step satisfies the following formula (1):
0≦M ₂ O _bulk /Al ₂ O _{3 bulk} ≦0.80 (1)
In the above formula (1), M ₂ O _bulk indicates the number of moles [mol] of alkali metal M in the bulk of CHA-type zeolite, converted into M ₂ O, and Al ₂ O _{3 bulk} indicates the number of moles [mol] of aluminum in the bulk of CHA-type zeolite, converted into Al ₂ O ₃ .
[3] A method for producing a CHA-type zeolite described in [1] or [2], wherein the organic structure-directing agent removal process is a process for removing the organic structure-directing agent contained in the CHA-type zeolite by calcining the CHA-type zeolite obtained in the crystallization process.
[4] The method for producing a CHA-type zeolite described in [3], wherein the calcination in the organic structure-directing agent removal step is carried out in an air atmosphere at 500°C or higher and 800°C or lower.
[5] The method for producing a CHA-type zeolite according to any one of [1] to [4], wherein the crystalline silica-alumina source is an FAU-type zeolite, and the FAU-type zeolite satisfies the following formula (2):
6≦SiO _{2 bulk} /Al ₂ O _{3 bulk} ratio≦50 (2)
In the above formula (2), SiO2 _bulk indicates the number of moles [mol] of silicon in the bulk of FAU zeolite in terms of _SiO2 , and _{Al2O3 bulk} indicates the number of moles [ _{mol] of aluminum in the bulk of FAU zeolite in terms of Al2O3 .}
[6] A method for producing a CHA-type zeolite described in any one of [1] to [5], wherein the CHA-type zeolite obtained in the steam treatment step has an intraframework Al ratio, represented by the following formula (3), that is 20% or more lower than the CHA-type zeolite obtained in the organic structure-directing agent removal step.
Al ratio in framework [%] = (SiO2 _bulk / _{Al2O3 bulk ratio} ) / (SiO2 _framework / _{Al2O3 framework} ratio) × 100 (3)
In the above formula (3), SiO2 _bulk indicates the number of moles [mol] of silicon in the bulk of CHA-type zeolite, converted into _SiO2 , _{Al2O3 bulk} indicates the number of moles [ _mol ] of aluminum in the bulk of CHA-type zeolite, converted into _Al2O3 , _{SiO2 skeleton} indicates the number of moles [mol] of silicon in the skeleton of CHA-type zeolite, converted into _SiO2 , and _Al2O3 skeleton indicates the number of moles [mol] of aluminum in the skeleton of _CHA -type zeolite, converted into _Al2O3 .

First, let us explain the meaning of each term used in this specification.

As used herein, "zeolite" refers to a compound in which skeletal atoms (hereinafter also referred to as "T atoms") have a regular structure with oxygen (O) tethered between them, and the T atoms are composed solely of at least one of metal atoms and metalloid atoms. Examples of metal atoms include one or more atoms selected from the group consisting of aluminum (Al), titanium (Ti), iron (Fe), zinc (Zn), gallium (Ga), and tin (Sn). Examples of metalloid atoms include at least one atom selected from the group consisting of boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te).

"Zeolite" is distinguished from compounds (hereinafter also referred to as "zeolite-related substances") that have a regular structure in which the T atoms are oxygen-mediated and contain at least one atom other than a metal or metalloid in the T atoms. Examples of "zeolite-related substances" include complex phosphorus compounds that contain phosphorus (P) as the T atom, such as aluminophosphate (AlPO) and silicoaluminophosphate (SAPO).

In this specification, "crystalline aluminosilicate" refers to a zeolite in which the T atoms are aluminum (Al) and silicon (Si). "Crystalline aluminosilicate" exhibits crystalline XRD peaks in its powder X-ray diffraction (hereinafter also referred to as "XRD") pattern, and is distinguished from "amorphous aluminosilicate," which does not exhibit crystalline XRD peaks.

In this specification, the "ordered structure" of a zeolite refers to a skeletal structure specified by a structure code (hereinafter simply referred to as "structure code") established by the Structure Commission of the International Zeolite Association. For example, "CHA-type zeolite" is a zeolite having a skeletal structure specified by the structure code "CHA," and "FAU-type zeolite" is a zeolite having a skeletal structure specified by the structure code "FAU." The framework structure (structure code) of each zeolite can be identified, for example, by comparison with the XRD pattern (hereinafter also referred to as the "reference pattern") described in "Collection of Simulated XRD Powder Patterns for Zeolites," Fifth Revised Edition, Page 113 (2007).

In this specification, the XRD patterns include those obtained by XRD measurement under the following conditions.
Acceleration voltage/current: 40 kV/20 mA
Radiation source: CuKα radiation (λ=1.5405Å)
Measurement mode: Continuous scan
Scan condition: 2.0°/min
Measurement range: 2θ = 3° to 53°
Detector: Semiconductor detector A crystalline XRD peak is a peak detected by identifying the 2θ of the peak top in an analysis of an XRD pattern using general analysis software (for example, SmartLab Studio II, manufactured by Rigaku Corporation), and an example of such a peak is an XRD peak having a half-width of 2θ = 0.50° or less.

In this specification, "SiO2 _skeleton " and " _{Al2O3 skeleton} " respectively refer to the number of moles [mol] of silicon in terms of _SiO2 and the number of moles [mol] of aluminum in terms of _Al2O3 that constitute the skeleton structure of a zeolite (hereinafter also referred to as "skeleton"). The ratio of the _{SiO2 skeleton} to the _{Al2O3 skeleton} (SiO2 _skeleton / _{Al2O3 skeleton} ratio) is also referred to as the silica-alumina ratio in the skeleton in the explanation below. The silica-alumina ratio in the skeleton (SiO2 _skeleton / _{Al2O3 skeleton} ratio) can be determined by ^29Si DDMAS NMR spectrum measurement.

In this specification, the term " ²⁹ Si DDMAS NMR spectrum" refers to a ²⁹ Si DDMAS NMR spectrum of a CHA-type zeolite that does not substantially contain an organic structure-directing agent, measured under the following conditions.
^1H resonance frequency: 600MHz
²⁹ Si resonance frequency: 119.2MHz
Rotor rotation speed: 10kHz
Repeat time: 30.0 seconds Total number of times: 2048
The ²⁹ Si DDMAS NMR spectrum can be measured using a general solid-state nuclear magnetic resonance apparatus (for example, AVANCE III 600, manufactured by Bruker). Peak fitting of the obtained NMR spectrum can be performed using standard NMR data processing software (software name: ALICE2, manufactured by JEOL) by performing surface integration for each peak using a mixed function of Gaussian distribution and Lorentzian distribution, and then calculating the SiO2 _skeleton / _{Al2O3 skeleton} ratio.

In this specification, "SiO2 _bulk " and " _{Al2O3 bulk} " refer to the number of moles of oxides of components contained in the entire zeolite (hereinafter also referred to as "bulk"), including the framework and non-framework, and are respectively the number of moles [mol] of silicon in the bulk in terms of _SiO2 and the number of moles [ _mol ] of aluminum in the bulk in terms of _Al2O3 . The ratio of SiO2 _{bulk to Al2O3 bulk ( SiO2 bulk} / _{Al2O3 bulk} ratio) is also referred to as the silica-alumina ratio in the bulk in the explanation below. The silica-alumina ratio in the bulk (SiO2 _bulk / _{Al2O3 bulk} ratio) can be determined by composition analysis. Composition analysis can be performed, for example, by inductively coupled plasma atomic emission spectroscopy (ICP-AES).

In this specification, "excessive" removal of aluminum from the framework structure means that the ratio of the _SiO2 / _{Al2O3 framework} ratio after steaming to the _SiO2 / _{Al2O3 framework} ratio before steaming (( _SiO2 / _{Al2O3 framework} ratio after steaming)/( _SiO2 / _{Al2O3 framework} ratio before steaming)) is greater than 13.0.

In this specification, the term "moderate" removal of aluminum from the framework structure means that the ratio of framework silica-alumina ratios before and after steam treatment (after steam treatment ( _{SiO2 framework} / _{Al2O3 framework} ratio)/before steam treatment (SiO2 _framework / _{Al2O3 framework} ratio)) is greater than 1.0 and not greater than 13.0.

One embodiment of the present disclosure is described below.

The manufacturing method of this embodiment relates to a method for manufacturing CHA-type zeolite, which includes a crystallization step, an organic structure-directing agent removal step, and a steam treatment step. According to the manufacturing method of CHA-type zeolite of this embodiment, aluminum can be appropriately removed from the framework structure.

The crystallization process is a process for crystallizing a composition containing a crystalline silica-alumina source, an alkali source, an organic structure-directing agent, and water (hereinafter also referred to as the "raw material composition"), and CHA-type zeolite (hereinafter referred to as "CHA-type zeolite Z1") is obtained through this crystallization process.

The crystalline silica-alumina source used in the crystallization step is a crystalline substance containing silicon and aluminum, and for example, a zeolite containing at least silicon and aluminum as T atoms can be used. Zeolites that can be used as the crystalline silica-alumina source include, for example, zeolites having any of the ANA, *BEA, CHA, EMT, FAU, FER, GIS, LTA, LTL, and MFI crystal structures. Among these zeolites, the CHA zeolite obtained by the production method of this embodiment (hereinafter also referred to as "CHA zeolite Z3") is preferred because it tends to have a silica-alumina ratio more suitable as a catalyst (for example, a SiO2 _framework / _{Al2O3 framework} ratio of 10 to 30). Therefore, FAU zeolite is preferred, a crystalline aluminosilicate having an FAU structure is more preferred, and zeolite Y is even more preferred.

The zeolite that can be used as the crystalline silica-alumina source is not particularly limited in terms of silica-alumina ratio, but since the CHA-type zeolite Z3 obtained by the production method of this embodiment is likely to have a silica-alumina ratio that can improve heat resistance and catalytic activity, it is preferable that the silica-alumina ratio in the bulk (SiO2 _bulk / _{Al2O3 bulk} ratio) satisfies the following formula (2).
6≦SiO _{2 bulk} /Al ₂ O _{3 bulk} ratio≦50 (2)

Furthermore, regarding the zeolite that can be used as the crystalline silica-alumina source, since the CHA-type zeolite Z3 obtained by the production method of this embodiment tends to have a silica-alumina ratio that is more suitable as a catalyst (for example, a SiO2 _skeleton / _{Al2O3 skeleton} ratio of 10 or more and 30 or less), it is more preferable that the silica-alumina ratio in the bulk (SiO2 _bulk / _{Al2O3 bulk} ratio) satisfies the following formula (4), and particularly preferably the following formula (5):
6≦SiO _{2 bulk} /Al ₂ O _{3 bulk} ratio≦25 (4)
6≦SiO _{2 bulk} /Al ₂ O _{3 bulk} ratio≦15 (5)

The cation type of zeolite that can be used as the crystalline silica-alumina source is not particularly limited, and for example, a proton type (H ⁺ type) can be used.

The alkali source used in the crystallization process is a compound containing an alkali metal, preferably an alkali metal hydroxide, more preferably at least one hydroxide selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, and even more preferably at least one hydroxide of sodium and potassium.

The source of the organic structure-directing agent used in the crystallization process is a substance containing an organic structure-directing agent that directs the CHA structure, specifically a salt containing an organic cation that directs the CHA structure.

The organic cation directing the CHA structure (organic structure-directing agent directing the CHA structure) can be a quaternary ammonium cation directing the CHA structure, preferably at least one selected from the group consisting of (1-adamantyl)trimethylammonium, choline cation, and trimethylbenzylammonium cation, and more preferably the (1-adamantyl)trimethylammonium (hereinafter also referred to as "TMada") cation.

The salt containing a cation that directs the CHA structure is preferably at least one selected from the group consisting of sulfates, nitrates, halides, and hydroxides, more preferably at least one of halides and hydroxides, and even more preferably hydroxides.

The water used in the crystallization process may be water contained separately from the above-mentioned raw materials, such as ion-exchanged water, but the water used in the crystallization process may also be structured water derived from the above-mentioned raw materials or water in the solvent in which the raw materials are dissolved.

The raw material composition crystallized in the crystallization step may be composed only of the above-mentioned crystalline silica-alumina source, alkali source, organic structure-directing agent, and water, but may also contain other raw materials in addition to these raw materials in order to fine-tune the composition of the raw material composition. Examples of other raw materials include an alumina source contained separately from the crystalline silica-alumina source, a silica source contained separately from the crystalline silica-alumina source, and seed crystals.

The silica source is a silicon-containing compound, and examples thereof include at least one selected from the group consisting of silica sol, fumed silica, colloidal silica, precipitated silica, and amorphous silicic acid.

The alumina source is a compound containing aluminum, and examples thereof include at least one selected from the group consisting of aluminum hydroxide, aluminum oxide, aluminum sulfate, aluminum chloride, aluminum nitrate, metallic aluminum, pseudoboehmite, alumina sol, and aluminum alkoxide.

The seed crystals are not particularly limited as long as they are directed toward the CHA structure, but for example, CHA-type zeolite can be used.

The molar ratio of alumina to silica in the raw material composition is not particularly limited, but is preferably 6 or more and 50 or less, since this tends to result in a silica-alumina ratio that can improve the heat resistance and catalytic activity of the CHA-type zeolite Z3 obtained by the production method of this embodiment. Since the CHA-type zeolite Z3 obtained by the production method of this embodiment tends to have a silica-alumina ratio that is more suitable as a catalyst (for example, a SiO2 _skeleton / _{Al2O3 skeleton} ratio of 10 or more and 30 or less), the SiO2 _bulk / _{Al2O3 bulk} ratio in the raw material composition is preferably 6 or more and 25 or less, and more preferably 6 or more and 15 or less.

The molar ratio of the organic structure-directing agent (hereinafter also referred to as "SDA") to silica in the raw material composition (hereinafter also referred to as "SDA/ _SiO2 ratio") is preferably 0.01 or more and 0.50 or less, more preferably 0.05 or more and 0.30 or less, and even more preferably 0.10 or more and 0.20 or less.

The molar ratio of alkali metal to silica in the raw material composition (hereinafter also referred to as "M/ _SiO2 ratio") is preferably 0.1 or more and 1.0 or less, more preferably 0.1 or more and 0.5 or less. In the M/ _SiO2 ratio, when the raw material composition contains two or more alkali metals, M refers to the total number of moles of the alkali metals.

The molar ratio of water (H ₂ O) to silica in the raw material composition (hereinafter also referred to as the "H ₂ O/SiO ₂ ratio") is preferably 3 or more and 50 or less, and more preferably 10 or more and 40 or less. From the viewpoint of imparting appropriate fluidity to the raw material composition, the H ₂ O/SiO ₂ ratio is preferably 20 or more and 35 or less.

When the raw materials contained in the raw material composition contain hydroxide, the molar ratio of hydroxide ions (hereinafter also referred to as "OH") to silica in the raw material composition (hereinafter also referred to as the "OH/ _SiO2 ratio") is preferably 0.1 or more and 1.0 or less, and more preferably 0.3 or more and 0.7 or less.

Preferable molar ratios of the raw material compositions are in the following ranges.
SiO ₂ /Al ₂ O ₃ ratio: 6 or more and 50 or less SDA/SiO ₂ ratio: 0.01 or more and 0.50 or less M/SiO ₂ ratio: 0.1 or more and 1.0 or less H ₂ O/SiO ₂ ratio: 3 or more and 50 or less OH/SiO ₂ ratio: 0.1 or more and 1.0 or less

Hydrothermal treatment can be used to crystallize the raw material composition in the crystallization step. Hydrothermal treatment can be carried out by placing the raw material composition in a sealed pressure-resistant container and heating it.

The temperature for the hydrothermal treatment is not particularly limited as long as it is a temperature at which the crystallization of the raw material composition proceeds, but is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 120°C or higher. Once the raw material composition crystallizes, there is no need to increase the hydrothermal treatment temperature more than necessary. Therefore, the hydrothermal treatment temperature should be 200°C or lower, preferably 180°C or lower, and more preferably 170°C or lower.

The hydrothermal treatment time is not particularly limited as long as it is sufficient for the raw material composition to crystallize, but is preferably from 1 hour to 168 hours, and particularly preferably from 24 hours to 120 hours. The treatment pressure during the hydrothermal treatment can be autogenous pressure.

In the hydrothermal treatment, the raw material composition may be crystallized in a stirred state or in a static state.

Here, in the crystallization step, only the above-mentioned crystallization treatment for crystallizing the raw material composition may be performed, but after the crystallization treatment of the raw material composition, a washing treatment and a drying treatment may also be performed.

In the washing process, CHA-type zeolite Z1 (solid phase) and the liquid phase are separated by a known method, and the CHA-type zeolite Z1 obtained as a solid phase is washed with pure water.

Drying treatment removes moisture from CHA-type zeolite Z1. The conditions for the drying treatment are arbitrary, but an example is leaving CHA-type zeolite Z1 in air at a temperature of 50°C to 150°C for at least 2 hours. The air may contain water vapor or may not contain water vapor. Specific examples of air include dry air generated in general dry air generators and industrial plants.

The above-described crystallization process can produce CHA-type zeolite Z1 as a crystalline substance. CHA-type zeolite Z1 contains at least silicon and aluminum as T atoms, but preferred CHA-type zeolite Z1 is a CHA-type crystalline aluminosilicate.

After crystallization, CHA-type zeolite Z1 contains the SDA and alkali metal ions contained in the raw material composition. In the organic structure-directing agent removal process described below, the SDA contained in CHA-type zeolite Z1 obtained in the crystallization process is removed to obtain a CHA-type zeolite that is substantially free of SDA (hereinafter also referred to as "CHA-type zeolite Z2"). "Substantially free of SDA" can be exemplified by the fact that the SDA content in CHA-type zeolite Z2 is 1% by mass or less.

To remove SDA in the organic structure-directing agent removal process, a calcination process can be used, in which the CHA-type zeolite Z1 obtained in the crystallization process is calcined. Note that, in this specification, calcination refers to a process carried out in an atmosphere with a water vapor concentration of less than 5% by volume, and is a process that is distinct from the steam treatment described below.

The firing conditions may be any conditions that allow the organic structure-directing agent to be removed, and are preferably carried out in an air atmosphere at 500°C or higher and 800°C or lower, as this facilitates efficient removal of the organic structure-directing agent. The firing time may be any conditions that allow the organic structure-directing agent to be removed, and is not particularly limited, but can be, for example, 1 to 24 hours.

When CHA-type zeolite Z1 is subjected to the above-mentioned calcination treatment, the SDA contained in CHA-type zeolite Z1 is replaced with protons (H ⁺ ), and the SDA is removed from the CHA-type zeolite.

Here, in the organic structure-directing agent removal process, only the above-described SDA removal treatment for removing the SDA contained in the CHA-type zeolite Z1 may be performed, or an ion exchange treatment may be further performed after the SDA removal treatment.

The ion exchange treatment is a process in which at least a portion of the counter cations of CHA-type zeolite Z2 after the SDA removal treatment are replaced with arbitrary cations. Examples of the arbitrary cations to be replaced include one or more selected from the group consisting of protons, ammonium ions, alkali metal ions, alkaline earth metal ions, and transition metal ions.

For example, the ion exchange treatment can be performed by contacting CHA-type zeolite Z2 with a solution containing any cation. Known ion exchange methods, such as the batch method or the flow method, can be used to contact CHA-type zeolite Z2 with a solution containing any cation, and known treatment conditions, such as contact time and number of contacts, can also be used.

The lower the alkali metal content of CHA-type zeolite Z2, the more easily aluminum is removed from the framework structure in the steam treatment step described below. Therefore, when attempting to remove a larger amount of aluminum from the framework structure (within a range in which aluminum removal from the framework structure is appropriate), the counter cation of CHA-type zeolite Z2 after the SDA removal treatment is preferably substituted with a cation other than an alkali metal, and more preferably with an ammonium ion (NH ₄ ⁺ ).

To replace the counter cation of CHA-type zeolite Z2 with ammonium ions (NH ₄ ⁺ ), for example, the CHA-type zeolite Z2 after the SDA removal treatment is dispersed (immersed) in an ammonium aqueous solution (for example, at least one of a 0.1 to 30 wt % ammonium nitrate aqueous solution and a 0.1 to 30 wt % ammonium chloride aqueous solution), and the CHA-type zeolite Z2 is brought into contact with the ammonium aqueous solution at 50 to 90°C for 1 to 48 hours, and the CHA-type zeolite Z2 is recovered and then dried. The above-mentioned treatment may be repeated two or more times.

The ion exchange treatment may be a treatment in which the counter cations of CHA-type zeolite Z2 are replaced with one type of cation, or a treatment in which the counter cations of CHA-type zeolite Z2 are replaced with two or more types of cations. Specifically, the ion exchange treatment may be a treatment in which the counter cations of CHA-type zeolite Z2 are replaced with ammonium ions and alkali metal ions.

When the counter cation of CHA type zeolite Z2 is substituted with ammonium ions and alkali metal ions, for example, the counter cation of CHA type zeolite Z2 is substituted with ammonium ions (NH ₄ ⁺ ) by a method similar to that described above, and the resulting CHA type zeolite Z2 is dispersed (immersed) in a 0.01 to 20.0 wt % aqueous alkali metal solution (e.g., one or more selected from the group consisting of an aqueous sodium nitrate solution, an aqueous potassium nitrate solution, an aqueous sodium chloride solution, and an aqueous potassium chloride solution), and the CHA type zeolite Z2 is contacted with the aqueous alkali metal solution at 50 to 100°C for 1 to 48 hours. The CHA type zeolite Z2 is recovered and then dried. The replacement treatment with alkali metal ions may be repeated two or more times. By this operation, a CHA type zeolite Z2 containing ammonium ions and alkali metal ions as counter cations of CHA type zeolite Z2 can be obtained.

The above-described conditions for the ion exchange treatment are merely examples, and the type of cation in the solution brought into contact with CHA-type zeolite Z2 can be changed depending on the type of cation to be replaced. Furthermore, the content of counter cations in CHA-type zeolite Z2 after the ion exchange treatment may be adjusted by adjusting the time for which CHA-type zeolite Z2 is brought into contact with the solution or the concentration of cations in the solution brought into contact with CHA-type zeolite Z2. Furthermore, the type of cation in the solution brought into contact with CHA-type zeolite Z2 may be a single type or multiple types.

CHA-type zeolite Z2 is obtained by removing the SDA from CHA-type zeolite Z1, and is a CHA-type zeolite containing at least silicon and aluminum as T atoms, but is preferably a CHA-type crystalline aluminosilicate.

The composition of CHA-type zeolite Z2 is not particularly limited as long as it does not substantially contain SDA. However, from the viewpoint of facilitating the removal of aluminum from the framework structure in the steam treatment step described later (within a range in which the removal of aluminum from the framework structure is moderate), it is preferable that the ratio of the number of moles of alkali metal M in _bulk , calculated as M ₂ O (hereinafter also referred to as "M ₂ O _bulk ") to Al 2 O ₃ bulk (hereinafter also referred to as "M ₂ O _bulk /Al ₂ O _{3 bulk} ") satisfies the following formula (1):
0≦M ₂ O _bulk /Al ₂ O _{3 bulk} ≦0.80 (1)

In the above formula (1), when _{M2O bulk} / _{Al2O3 bulk} is 0, it means that no alkali metal is contained in CHA-type zeolite Z2 (i.e., the detection limit). The _{M2O bulk} / _{Al2O3 bulk} can be determined by the method described in the examples below.

When CHA-type zeolite Z2 contains an alkali metal ion as a counter cation (the cation type is alkali metal type), it is more preferable that the _{M2O bulk} / _{Al2O3 bulk} of CHA-type zeolite Z2 satisfies the following formula (6): By performing the steam treatment described later using alkali metal-type CHA-type zeolite Z2 that satisfies the following formula (6), the CHA-type zeolite Z3 obtained by the production method of this embodiment is more likely to have a silica-alumina ratio that is more suitable as a catalyst (for example, a SiO2 _skeleton / _{Al2O3 skeleton} ratio of 10 or more and 30 or less), compared to alkali metal-type CHA-type zeolite Z2 that does not satisfy the following formula (6).
0.40≦M ₂ O _bulk /Al ₂ O _{3 bulk} ≦0.80 (6)

In CHA-type zeolite Z2, the silica-alumina ratio in the framework (SiO2 _framework / _{Al2O3 framework} ratio) is not particularly limited, but since the CHA-type zeolite Z3 obtained by the production method of this embodiment is likely to have a silica-alumina ratio that can improve heat resistance and catalytic activity, it is preferably 6 or more and 50 or less. Since the CHA-type zeolite Z3 obtained by the production method of this embodiment is likely to have a silica-alumina ratio that is more suitable as a catalyst (for example, a SiO2 _framework / _{Al2O3 framework} ratio of 10 or more and 30 or less), the SiO2 _framework / _{Al2O3 framework} ratio in CHA-type zeolite Z2 is preferably 6 or more and 25 or less, and more preferably 6 or more and 15 or less.

In CHA-type zeolite Z2, the silica-alumina ratio in the bulk (SiO2 _bulk / _{Al2O3 bulk} ratio) is not particularly limited, but is preferably 6 or more and 50 or less. Since the CHA-type zeolite Z3 obtained by the production method of this embodiment tends to have a silica-alumina ratio that is more suitable as a catalyst (for example, a SiO2 _skeleton / _{Al2O3 skeleton} ratio of 10 or more and 30 or less), the SiO2 _bulk / _{Al2O3 bulk} ratio in CHA-type zeolite Z2 is preferably 6 or more and 25 or less, and more preferably 6 or more and 15 or less.

In CHA-type zeolite Z2, the framework Al ratio is not particularly limited, but can be, for example, more than 80% and 110% or less. The framework Al ratio is the ratio of the silica-alumina ratio in the framework (SiO2 _framework / _{Al2O3 framework} ratio) to the silica-alumina ratio in the bulk (SiO2 _bulk / _{Al2O3 bulk} ratio), and can be calculated from the following formula (3). A framework Al ratio of less than 100% means that the alumina ratio in the framework (alumina to silica ratio) is lower than the alumina ratio in the bulk (alumina to silica ratio).
Al ratio in framework [%] = (SiO2 _bulk / _{Al2O3 bulk} ratio) / (SiO2 _framework / _{Al2O3 framework} ratio) × 100 (3)

CHA-type zeolite Z3 is produced by subjecting CHA-type zeolite Z2 to steam treatment, as described below.

In the steam treatment step, CHA-type zeolite Z2 is contacted with a gas containing steam. The water vapor concentration in the gas contacted with CHA-type zeolite Z2 is 5% by volume or more and less than 50% by volume, relative to 100% by volume of the gas contacted with CHA-type zeolite Z2. If the water vapor concentration in the gas contacted with CHA-type zeolite Z2 is 50% by volume or more, excessive removal of aluminum from the framework structure will occur. On the other hand, if the water vapor concentration in the gas contacted with CHA-type zeolite Z2 is less than 5% by volume, aluminum may not be removed from the framework structure.

The water vapor concentration in the gas brought into contact with CHA type zeolite Z2 may be 5% by volume or more and less than 50% by volume, but is preferably 5% by volume or more and 40% by volume or less, and more preferably 5% by volume or more and 30% by volume or less, because CHA type zeolite Z3 is likely to have a silica-alumina ratio more suitable as a catalyst (for example, a SiO2 _skeleton / _{Al2O3 skeleton} ratio of 10 to 30). Note that the water vapor concentration can be determined from the water vapor partial pressure in the gas brought into contact with CHA type zeolite Z2, assuming an ideal gas.

The treatment temperature for the steam treatment is, for example, 500° C. or higher and lower than 900° C., and preferably 550° C. or higher and 850° C. or lower. When the cation type of CHA type zeolite Z2 is _NH4 type (containing ammonium ions as counter cations), the treatment temperature for the steam treatment is more preferably 550° C. or higher and 750° C. or lower. For CHA type zeolite Z2 whose cation type is _NH4 type, when the treatment temperature for the steam treatment is 550° C. or higher and 750° C. or lower, CHA type zeolite Z3 is more likely to have a silica-alumina ratio more suitable as a catalyst (for example, a SiO2 _skeleton / _{Al2O3 skeleton} ratio of 10 or higher and 30 or lower) compared to when the temperature is outside this range.

The steam treatment time can be, for example, from 1 hour to 72 hours, and is preferably from 10 hours to 30 hours because CHA-type zeolite Z3 tends to have a silica-alumina ratio more suitable for use as a catalyst (for example, a SiO2 _skeleton / _{Al2O3 skeleton} ratio of from 10 to 30).

The gas to be contacted with CHA-type zeolite Z2 contains other gases in addition to water vapor. Examples of such other gases include air and an inert gas such as argon or nitrogen. An inert gas is preferable, and a mixture of an inert gas and air may also be used. The air may contain water vapor or may not contain water vapor. If the gas contains water vapor, the amount of water vapor contained in the air is adjusted so that the total concentration of the water vapor in the air and the water vapor separately contained in the air is 5% to less than 50% by volume relative to 100% by volume of the gas to be contacted with CHA-type zeolite Z2. If the water vapor contained in the air alone results in a water vapor concentration of 5% to less than 50% by volume of the gas to be contacted with CHA-type zeolite Z2, it is not necessary to separately add water vapor to the air. Specific examples of such air include air with a water vapor concentration of less than 50% by volume, dry air generated in general dry air generators or industrial plants, and pressurized air such as instrumentation air. When the gas is an inert gas, the inert gas contains water vapor in an amount of 5% to 50% by volume relative to 100% by volume of the gas contacted with CHA-type zeolite Z2. Specific examples of inert gases include argon with a water vapor concentration of less than 50% by volume and pressurized nitrogen such as instrument nitrogen.

Steam treatment may be carried out under atmospheric pressure or under pressure. Furthermore, steam treatment may be carried out in a sealed container, or in a stream of air or an inert gas. When steam treatment is carried out in a stream of air or an inert gas, the gas flow rate may be, for example, 10 to 50 mL/min, and preferably 20 to 40 mL/min.

The method for generating water vapor is not particularly limited, and examples include vaporizing water and mixing it with gas, or treating the CHA-type zeolite Z2 to be steamed while it is still moist.

In the steam treatment step, by contacting the CHA-type zeolite Z2 obtained in the organic structure-directing agent removal step with a gas having a water vapor concentration of 5% by volume or more and less than 50% by volume, aluminum can be appropriately removed from the framework structure (i.e., the _ratio of the SiO2 _framework / _Al2O3 framework ratio (ratio of framework silica-alumina ratio before and after steam treatment) of CHA-type zeolite Z3 (after steam treatment) to the SiO2 _framework / _{Al2O3 framework} ratio of CHA-type zeolite Z2 (before steam treatment) is more than 1.0 and 13.0 or less).

The skeletal silica-alumina ratio before and after the steam treatment may be greater than 1.0 and less than or equal to 13.0, but is more preferably 1.30 or greater and 13.0 or less. When the skeletal silica-alumina ratio before and after the steam treatment is 1.30 or greater, it is believed that the heat resistance of CHA-type zeolite Z3 is further improved. Furthermore, the skeletal silica-alumina ratio before and after the steam treatment is even more preferably 1.30 or greater and 10 or less, and particularly preferably 1.30 or greater and 2.5 or less. When the skeletal silica-alumina ratio before and after the steam treatment is 10 or less (particularly, 2.5 or less), CHA-type zeolite Z3 is more likely to have a silica-alumina ratio that is more suitable as a catalyst (for example, a SiO2 _skeleton / _{Al2O3 skeleton} ratio of 10 or greater and 30 or less), compared to when it is outside that range.

In CHA-type zeolite Z3, the silica-alumina ratio in the skeleton (SiO2 _skeleton / _{Al2O3 skeleton} ) is not particularly limited as long as it is more than 1.0 times and not more than 13.0 times the silica-alumina ratio in the skeleton of CHA-type zeolite Z2. However, from the viewpoint of obtaining a silica-alumina ratio more suitable as a catalyst, it is preferably 10 or more and 50 or less, and more preferably 10 or more and 30 or less.

In CHA-type zeolite Z3, the silica-alumina ratio in the bulk (SiO2 _bulk / _{Al2O3 bulk} ratio) is not particularly limited, but usually the silica-alumina ratio in the bulk is unlikely to change before and after steam treatment. Therefore, in CHA-type zeolite Z3, the silica-alumina ratio in the bulk (SiO2 _bulk / _{Al2O3 bulk} ratio) is preferably 6 or more and 50 or less, more preferably 6 or more and 25 or less, and particularly preferably 6 or more and 15 or less, similar to CHA-type zeolite Z2.

The Al ratio in the framework of CHA-type zeolite Z3 is calculated from the silica-alumina ratio in the framework and the silica-alumina ratio in the bulk. It is not particularly limited as long as it satisfies these silica-alumina ratio restrictions, but it is preferably 20% or more and 80% or less.

As mentioned above, the silica-alumina ratio in the framework increases by steam treatment, but the silica-alumina ratio in the bulk usually does not change much before and after steam treatment. For this reason, the framework Al ratio of CHA-type zeolite Z3 is usually smaller than the framework Al ratio of CHA-type zeolite Z2. The difference in the framework Al ratios between CHA-type zeolite Z3 and CHA-type zeolite Z2 (the value obtained by subtracting the framework Al ratio of CHA-type zeolite Z3 from the framework Al ratio of CHA-type zeolite Z2) is preferably 20% or more. When the difference in the framework Al ratios between CHA-type zeolite Z3 and CHA-type zeolite Z2 is 20% or more, Al released from the framework by steam treatment is more likely to interact with T atoms in the framework, compared to when the difference is less than 20%. As a result, it is believed that the heat resistance of CHA-type zeolite Z3 is further improved.

The difference in the framework Al ratio between CHA-type zeolite Z3 and CHA-type zeolite Z2 tends to vary depending on the steaming temperature, steam concentration, and steaming time. For example, when the steaming temperature is 500°C or higher but lower than 900°C and the steam concentration is 5% by volume or higher but lower than 50% by volume, the difference in the framework Al ratio between CHA-type zeolite Z3 and CHA-type zeolite Z2 can be made 20% or higher by setting the steaming time to 10 hours or longer.

In CHA-type zeolite Z3, the BET specific surface area is not particularly limited, but can be 500 m ² /g or more and 900 m ² /g or less, 520 ^{m 2} /g or more and 850 m ² /g or less, or 540 m ² /g or more and 800 m ² /g or less.

In CHA-type zeolite Z3, the micropore volume is not particularly limited, but can be 0.20 mL/g or more and 0.40 mL/g or less, 0.21 mL/g or more and 0.38 mL/g or less, or 0.22 mL/g or more and 0.36 mL/g or less.

CHA-type zeolite Z3 is a CHA-type zeolite obtained by removing some of the aluminum from the framework of CHA-type zeolite Z2, and contains at least silicon and aluminum as T atoms, but is preferably a CHA-type crystalline aluminosilicate.

The manufacturing method of this embodiment described above makes it possible to produce CHA-type zeolite Z3 with an appropriate amount of aluminum removed from the framework structure. CHA-type zeolite Z3 obtained by the manufacturing method of this embodiment can be used in a variety of catalytic applications, such as cracking catalysts and nitrogen oxide reduction catalysts, and is thought to be a zeolite with a stable crystal structure. Furthermore, if the framework silica-alumina ratio before and after steam treatment is set to 1.30 or higher, it is thought that the resulting zeolite will have even better heat resistance.

The present embodiment will be described below using examples. However, the present embodiment is not limited to these examples.

(Crystal structure)
The samples were subjected to XRD measurement using a general powder X-ray diffractometer (device name: Ultima IV, manufactured by Rigaku Corporation). The measurement conditions are as follows. The obtained XRD pattern was compared with a reference pattern to identify the crystal structure of the sample.
Acceleration voltage/current: 40 kV/20 mA
Radiation source: CuKα radiation (λ=1.5405Å)
Measurement mode: Continuous scan
Scan condition: 2.0°/min
Measurement range: 2θ = 3° to 53°

( ^29Si DDMAS NMR measurement)
The ²⁹ Si DDMAS NMR spectrum of the sample was measured using a general solid-state nuclear magnetic resonance spectrometer (apparatus name: AVANCE III 600, manufactured by Bruker). The measurement conditions were as follows:
^1H resonance frequency: 600MHz
²⁹ Si resonance frequency: 119.2MHz
Rotor rotation speed: 10kHz
Repeat time: 30.0 seconds Total number of times: 2048

In the obtained ²⁹ Si DDMAS NMR spectrum, the area of the peak having its top between -114 ppm and -107 ppm was assigned to Q ⁴ (0Al)(Si(OSi) ₄ ), the area of the peak having its top between -107 ppm and -103 ppm was assigned to Q ⁴ (1Al)(Si(OAl)(OSi) ₃ ), the area of the peak having its top between -103 ppm and -100 ppm was assigned to Q ³ (0Al)(Si(OH)(OSi) ₃ ), and the area of the peak having its top between -100 ppm and -96 ppm was assigned to Q ⁴ (2Al)(Si(OAl)(OSi) ₃ ).

Peak fitting was performed using standard NMR data processing software (software name: ALICE2, JEOL), and surface integration was performed for each peak using a mixed function of Gaussian distribution and Lorentzian distribution, and the SiO2 _skeleton / _{Al2O3 skeleton} ratio was calculated using the following equation (7).
SiO _{2 skeleton} /Al ₂ O _{3 skeleton} ratio = 2 × (Q ⁴ (0Al) + Q ⁴ (1Al) + Q ⁴ (2Al) + Q ⁴ (3Al) + Q ³ (0Al)) / (0.25 × Q ⁴ (1Al) + 0.50 × Q ⁴ (2Al) + 0.75 × Q ⁴ (3Al))) ... (7)

(composition analysis)
A sample solution was prepared by dissolving the sample in hydrofluoric acid. The sample solution was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES) using a general ICP device (device name: ICPE-9000, manufactured by Shimadzu Corporation) to determine the SiO2 _bulk / _{Al2O3 bulk} ratio, _{Na2O bulk} / _{Al2O3 bulk ratio} , and _{K2O bulk} / _{Al2O3 bulk ratio} in the sample.

(BET specific surface area and micropore volume)
The amount of nitrogen gas adsorbed to the sample was measured using a general nitrogen adsorption apparatus (apparatus name: BELSORP Max, manufactured by Microtrac BEL). The BET specific surface area of the sample was determined by applying the BET method to the nitrogen gas adsorption isotherm. Furthermore, the micropore volume was determined by applying the t-plot method to the nitrogen gas adsorption isotherm. For the t-plot method, analysis software attached to the nitrogen adsorption apparatus (product name: BEL Master (version 7), manufactured by Microtrac BEL) was used. For nitrogen gas adsorption, a normal constant volume method was used. The measurement conditions are as shown below.
Gas used: 99.999% nitrogen
Measurement temperature: -196℃
Pretreatment: 400°C, 12 hours of reduced pressure heating (2 Pa or less)

(Steam treatment)
The zeolite powders were packed into atmospheric pressure fixed-bed flow reactors. Steam containing water vapor was passed through the reactors to treat the zeolite samples with steam. The gas composition and treatment conditions are shown below.
Sample mass: 0.4 g, 0.5 g, or 1.0 g
Gas composition: Water 10% or 20% by volume
Argon, balance Gas flow rate: 30 mL/min Treatment temperature: 600°C, 700°C or 800°C
Heating time from room temperature: 1 hour Holding time: 24 hours Pressure: atmospheric pressure

[Example 1]
A raw material composition having the following composition was obtained by mixing an aqueous solution of (1-adamantyl)trimethylammonium hydroxide (TMadaOH), pure water, sodium hydroxide, and FAU-type zeolite (product name: HSZ-350HUA, manufactured by Tosoh Corporation, cation type: H-type, bulk SiO ₂ /Al ₂ O ₃ ratio = 11.1, crystalline aluminosilicate).
_SiO2 / _{Al2O3 ratio} = 11.1
SDA(TMada)/ _SiO2 ratio =0.20
Na/ _SiO2 ratio =0.10
K/ _SiO2 ratio =0.10
_H2O / _SiO2 ratio =20.0
OH/ _SiO2 ratio =0.40

The resulting raw material composition was filled into a 23 mL sealed container, and the sealed container was rotated at 20 rpm to agitate the raw material composition, followed by hydrothermal treatment at 170°C for 96 hours. The crystallized product after hydrothermal treatment was separated into solid and liquid, washed with pure water, and then dried in air at 80°C for 24 hours to obtain CHA-type zeolite Z1 (CHA-type crystalline aluminosilicate).

The CHA-type zeolite Z1 was calcined in air at 600°C for 10 hours to remove SDA (TMAda) contained in the CHA-type zeolite Z1, thereby obtaining CHA-type zeolite Z2 (a CHA-type crystalline aluminosilicate). The obtained CHA-type zeolite Z2 had a SiO2 _bulk / _{Al2O3 bulk} ratio of 9.9, a SiO2 _framework / _{Al2O3 framework} ratio of 9.8, a framework Al ratio of 101%, a _{Na2O bulk} / _{Al2O3 bulk} ratio of 0.25, a _{K2O bulk} / _{Al2O3 bulk} ratio of 0.38, and a _{bulk M2O} / _Al2O3 ratio of 0.63.

The aforementioned CHA-type zeolite Z2 was dispersed in a 4 wt% aqueous ammonium nitrate solution and subjected to ion exchange treatment at 80°C for 24 hours under static conditions. The solid matter was subjected to solid-liquid separation, washed with pure water, and then dried in air at 80°C for 24 hours. This procedure was repeated three times to obtain CHA-type zeolite Z2 (CHA-type crystalline aluminosilicate) whose cation type was _NH4 . The obtained NH4 _- type CHA-type zeolite Z2 had a SiO2 _bulk / _{Al2O3 bulk} ratio of 9.9, a SiO2 _framework / _{Al2O3 framework} ratio of 11.2, an intra-framework Al ratio of 88%, a _{Na2O bulk} / _{Al2O3 bulk} ratio of less than 0.02 (detection limit), a _{K2O bulk} / _{Al2O3 bulk} ratio of less than 0.03 (detection limit), and a _{M2O bulk} / _{Al2O3 bulk} ratio of less than 0.05 (detection limit).

NH4 _- type CHA-type zeolite Z2 was subjected to steam treatment at 600°C for 24 hours under a steam concentration of 10% by volume. The resulting CHA-type zeolite Z3 (CHA-type crystalline aluminosilicate) had a BET specific surface area of 749 ^m2 /g, a micropore volume of 0.27 mL/g, a SiO2 _bulk / _{Al2O3 bulk} ratio of 9.9, a SiO2 _framework / _{Al2O3 framework} ratio of 15.2, a framework Al ratio of 65%, a bulk _{Na2O bulk} / _{Al2O3 bulk} ratio of less than 0.02 (detection limit), a _{K2O bulk} / _{Al2O3 bulk} ratio of less than 0.03 (detection limit), and a _{M2O bulk} / _{Al2O3 bulk} ratio of less than 0.05 (detection limit).

[Example 2]
CHA-type zeolite Z3 (CHA-type crystalline aluminosilicate) was obtained in the same manner as in Example 1, except that the steam treatment temperature was 700° C. The obtained CHA-type zeolite Z3 had a BET specific surface area of 720 m ² /g, a micropore volume of 0.27 mL/g, a SiO _{2 bulk} /Al ₂ O _{3 bulk} ratio of 9.9, a SiO _{2 skeleton} /Al ₂ O _{3 skeleton} ratio of 26.0, an intraskeletal Al ratio of 38%, a Na ₂ O _bulk /Al ₂ O _{3 bulk} ratio of less than 0.02 (detection limit), a K ₂ O _bulk /Al ₂ O _{3 bulk} ratio of less than 0.03 (detection limit), and a M ₂ O _bulk /Al ₂ O _{3 bulk} ratio of less than 0.05 (detection limit).

[Example 3]
CHA-type zeolite Z3 (CHA-type crystalline aluminosilicate) was obtained in the same manner as in Example 1, except that the steam treatment temperature was 800° C. The obtained CHA-type zeolite Z3 had a BET specific surface area of 546 m ² /g, a micropore volume of 0.23 mL/g, a SiO _{2 bulk} /Al ₂ O _{3 bulk} ratio of 9.9, a SiO _{2 skeleton} /Al ₂ O _{3 skeleton} ratio of 140.0, an intraskeletal Al ratio of 7%, a Na ₂ O _bulk /Al ₂ O _{3 bulk} ratio of less than 0.02 (detection limit), a K ₂ O _bulk /Al ₂ O _{3 bulk} ratio of less than 0.03 (detection limit), and a M ₂ O _bulk /Al ₂ O _{3 bulk} ratio of less than 0.05 (detection limit).

[Example 4]
CHA-type zeolite Z2 (CHA-type zeolite Z2 not subjected to ion exchange treatment) was obtained by the same method as in Example 1, and then subjected to steam treatment in a water vapor concentration of 20% by volume at 800°C for 24 hours. The obtained CHA-type zeolite Z3 (CHA-type crystalline aluminosilicate) had a BET specific surface area of 724 ^m2 /g, a micropore volume of 0.25 mL/g, a SiO2 _bulk / _{Al2O3 bulk} ratio of 9.9, a SiO2 _framework / _{Al2O3 framework} ratio of 13.4, a framework Al ratio of 74%, a _{Na2O bulk} / _{Al2O3 bulk} ratio of 0.25, a _{K2O bulk} / _{Al2O3 bulk} ratio of 0.38, and a _{M2O bulk} / _{Al2O3 bulk} ratio of 0.63.

[Example 5]
CHA-type zeolite Z2 with an NH4 _cation type was obtained in the same manner as in Example 1, and then 1.01 g of the zeolite was dispersed in 50.5 g of a 0.22 wt % aqueous sodium nitrate solution and subjected to ion exchange treatment at 80°C for 24 hours under static conditions. The solid was subjected to solid-liquid separation, washed with pure water, and then dried in air at 80°C for 24 hours. This operation was repeated three times to obtain CHA-type zeolite Z2 (CHA-type crystalline aluminosilicate) containing ammonium ions and sodium ions as counter cations. The obtained zeolite Z2 had a SiO2 _bulk / _{Al2O3 bulk} ratio of 9.8, a SiO2 _framework / _{Al2O3 framework} ratio of 11.2, an intra-framework Al ratio of 87%, a _{Na2O bulk} / _{Al2O3 bulk} ratio of 0.23, a _{K2O bulk} / _{Al2O3 bulk} ratio of less than 0.03 (detection limit), and a _{M2O bulk} / _{Al2O3 bulk} ratio of 0.23 to 0.26.

0.4 g of CHA-type zeolite Z2 was subjected to steam treatment in a steam concentration of 10% by volume at 800°C for 24 hours. The resulting CHA-type zeolite Z3 (CHA-type crystalline aluminosilicate) had a SiO2 _bulk / _{Al2O3 bulk} ratio of 9.8, a SiO2 _skeleton / _{Al2O3 skeleton} ratio of 40.8, an intraskeletal Al ratio of 24%, a _{Na2O bulk} / _{Al2O3 bulk} ratio of 0.22, a _{K2O bulk} / _{Al2O3 bulk} ratio of less than 0.03 (detection limit), and an _{M2O bulk} / _{Al2O3 bulk} ratio of 0.23 to 0.26.

[Example 6]
CHA-type zeolite Z2 with an NH4 _cation type was obtained in the same manner as in Example 1, and then 1.01 g of the zeolite was dispersed in 50.8 g of a 0.43 wt % aqueous sodium nitrate solution and subjected to ion exchange treatment at 80°C for 24 hours under static conditions. The solid matter was subjected to solid-liquid separation, washed with pure water, and then dried in air at 80°C for 24 hours. This operation was repeated three times to obtain CHA-type zeolite Z2 (CHA-type crystalline aluminosilicate) containing ammonium ions and sodium ions as counter cations. The obtained CHA-type zeolite Z2 had a SiO2 _bulk / _{Al2O3 bulk} ratio of 9.7, a SiO2 _framework / _{Al2O3 framework} ratio of 11.0, an Al ratio in the framework of 88%, a _{Na2O bulk} / _{Al2O3 bulk} ratio of 0.35, a _{K2O bulk} / _{Al2O3 bulk} ratio of less than 0.03 (detection limit), and a _{M2O bulk} / _{Al2O3 bulk} ratio of 0.35 to 0.38.

0.5 g of CHA-type zeolite Z2 was subjected to steam treatment in a 10% by volume water vapor concentration at 800°C for 24 hours. The resulting CHA-type zeolite Z3 (CHA-type crystalline aluminosilicate) had a SiO2 _bulk / _{Al2O3 bulk} ratio of 9.7, a SiO2 _skeleton / _{Al2O3 skeleton} ratio of 32.2, a framework Al ratio of 30%, a _{Na2O bulk} / _{Al2O3 bulk} ratio of 0.35, a _{K2O bulk} / _{Al2O3 bulk} ratio of less than 0.03 (detection limit), and a _{M2O bulk} / _{Al2O3 bulk} ratio of 0.35 to 0.38.

[Comparative Example 1]
A raw material composition having the following composition was obtained by mixing an aqueous TMA DaOH solution, pure water, sodium hydroxide, aluminum hydroxide, amorphous silica (product name: Nipsil LP, manufactured by Tosoh Silica Corporation), and FAU-type zeolite (product name: HSZ-320NAA, manufactured by Tosoh Corporation, cation type: Na type, bulk SiO ₂ /Al ₂ O ₃ ratio = 5.7, crystalline aluminosilicate).
_SiO2 / _Al2O3 ratio = ₃₄
TMada/ _SiO2 ratio =0.19
Na/ _SiO2 ratio =0.24
OH/ _SiO2 ratio =0.43
H ₂ O/SiO ₂ ratio = 12

The obtained raw material composition was filled into an 80 mL sealed container, and the raw material composition was stirred while rotating the sealed container at 40 rpm, followed by hydrothermal treatment for 5 days at 150° C. The crystallized product (CHA-type zeolite Z1) after the hydrothermal treatment was subjected to solid-liquid separation, washed with pure water, and then calcined in air at 600° C. for 10 hours to remove SDA (TMAda) contained in the CHA-type zeolite Z1. The obtained CHA-type zeolite Z2 was a CHA-type zeolite having a SiO2 _bulk / _{Al2O3 bulk} ratio of 22.4, a SiO2 _framework / _{Al2O3 framework} ratio of 22.9, an Al ratio in the framework of 98%, a _{Na2O bulk} / _{Al2O3 bulk} ratio of 0.53, a _{K2O bulk} / _{Al2O3 bulk} ratio of 0, and a _{M2O bulk} / _{Al2O3 bulk} ratio of 0.53.

For each Example and Comparative Example, the composition of zeolite Z2, the composition of zeolite Z3, and the ratio of the _SiO2 / _{Al2O3 skeletal} ratio of zeolite Z3 to _{the SiO2} / _{Al2O3 skeletal} ratio of zeolite Z2 (the ratio of silica-alumina ratios before and after steam treatment) are shown in Tables 1 to 3 below, respectively.

As can be seen from Table 3 above, the silica-alumina ratio before and after the steam treatment was 1.36 to 12.50 in Examples 1 to 6. From these results, it was understood that the production methods of Examples 1 to 6 were able to adequately remove aluminum from the skeletal structure.

Claims (5)

A crystallization step of crystallizing and washing a composition comprising a crystalline silica-alumina source, an alkali source, an organic structure directing agent, and water;
an organic structure directing agent removal step of removing the organic structure directing agent contained in the CHA-type zeolite obtained in the crystallization step;
a steam treatment step of contacting the CHA-type zeolite obtained in the organic structure-directing agent removal step with a gas containing water vapor,
The water vapor concentration in the gas is 5% by volume or more and less than 50% by volume ,
The CHA-type zeolite obtained in the steam treatment step has a framework Al ratio, represented by the following formula (3), that is 20% or more lower than that of the CHA-type zeolite obtained in the organic structure-directing agent removal step.
Al ratio in framework [%] = (SiO2 _bulk / _{Al2O3 bulk} ratio) / (SiO2 framework _/ Al2O3 _framework ratio ₎ × 100 (3)
In the above formula (3), SiO2 _bulk indicates the number of moles [mol] of silicon in the bulk of CHA-type zeolite , converted into _SiO2 , _{Al2O3 bulk} indicates the number of moles [mol] of aluminum in the bulk of CHA-type zeolite, converted into Al2O3 , SiO2 _skeleton indicates the number of moles [mol] of silicon in the skeleton _{of CHA -} type zeolite , converted into _SiO2 , and Al2O3 _skeleton indicates the number of moles [mol ] of aluminum in the skeleton of _CHA -type zeolite, converted into _Al2O3 . The method for producing a CHA-type zeolite according to claim 1, wherein the CHA-type zeolite obtained in the organic structure-directing agent removal step satisfies the following formula (1):
0≦M ₂ O _bulk /Al ₂ O _{3 bulk} ≦0.80 (1)
In the above formula (1), M ₂ O _bulk indicates the number of moles [mol] of alkali metal M in the bulk of CHA-type zeolite, converted into M ₂ O, and Al ₂ O _{3 bulk} indicates the number of moles [mol] of aluminum in the bulk of CHA-type zeolite, converted into Al ₂ O ₃ . The method for producing CHA-type zeolite according to claim 1 or 2, wherein the organic structure-directing agent removal step is a step of calcining the CHA-type zeolite obtained in the crystallization step to remove the organic structure-directing agent contained in the CHA-type zeolite. The method for producing CHA-type zeolite described in claim 3, wherein the calcination in the organic structure-directing agent removal step is carried out in an air atmosphere at 500°C or higher and 800°C or lower. The crystalline silica-alumina source is an FAU-type zeolite,
The method for producing CHA-type zeolite according to any one of claims 1 to 4, wherein the FAU-type zeolite satisfies the following formula (2):
6≦SiO _{2 bulk} /Al ₂ O _{3 bulk} ratio≦50 (2)
In the above formula (2), SiO2 _bulk indicates the number of moles [mol] of silicon in the bulk of FAU zeolite in terms of _SiO2 , and _{Al2O3 bulk} indicates the number of moles [ _{mol] of aluminum in the bulk of FAU zeolite in terms of Al2O3 .}