MFI-type zeolite and method for manufacturing the same

Abstract

The objective is to provide at least one of the following: an MFI-type zeolite having excellent catalytic activity, as well as excellent durability and handling properties, and a method for producing the same. [Solution] An MFI-type zeolite having a molar ratio of silica to alumina of 40 to 150, an average primary crystal diameter of 0.1 μm to 5 μm, a standard deviation of volume particle size distribution of 15 μm or less, and an acid content of 0.50 mmol / g or more.

Description

[Technical Field]

[0001] This disclosure relates to MFI-type zeolite and a method for producing the same. [Background technology]

[0002] MFI-type zeolites are used in various industrial fields as catalysts and adsorbents. Among them, MFI-type zeolites with a high acid content exhibit high catalytic activity. On the other hand, if the acid content of MFI-type zeolites is made too high, the crystalline structure is prone to collapse when it comes into contact with high-temperature steam due to the desorption of contained aluminum, and generally the durability is low. Catalytic activity and durability in MFI-type zeolites are inversely related.

[0003] One of the Sustainable Development Goals (SDGs) targets is to "significantly reduce waste generation by 2030 through prevention, reduction, recycling and reuse," which is an important theme for manufacturing industries, including the chemical industry. Against this backdrop of the need to reduce environmental impact, there has been a growing demand for MFI-type zeolites to exhibit catalytic activity under more severe conditions. There is a strong desire for MFI-type zeolites that possess excellent catalytic activity while also exhibiting durability to withstand harsh conditions. One example of an MFI-type zeolite with excellent catalytic activity is one obtained by using a quaternary ammonium cation as a structure-directing agent (hereinafter also referred to as "SDA") (for example, Patent Document 1).

[0004] Furthermore, MFI-type zeolites are transported in the form of powder or zeolite slurry containing them, and processed into molded bodies or other forms as needed for use in specified applications such as catalysts and adsorbents. If the volume particle size distribution of the MFI-type zeolite is broad (i.e., there is a large variation in the particle size of the zeolite), the MFI-type zeolite may accumulate or clog during transport, reducing handling performance. As a result, yield may decrease or waste may be generated. From the perspective of "significantly reducing waste generation," high handling performance is also required for zeolites. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-145085 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] MFI-type zeolites obtained using quaternary ammonium cations as the SDA, as described in Patent Document 1, possess excellent catalytic activity. However, their small average primary crystal diameter makes them susceptible to the effects of water vapor, resulting in low durability under harsh conditions. Furthermore, MFI-type zeolites obtained using quaternary ammonium cations as the SDA, as described in Patent Document 1, can sometimes exhibit a broad volume particle size distribution depending on the raw materials used in their production, leading to poor handling.

[0007] This disclosure aims to provide at least one of the following: an MFI-type zeolite having excellent catalytic activity, as well as excellent durability and handling properties, and a method for producing the same. [Means for solving the problem]

[0008] The present inventors investigated a method for producing MFI-type zeolite using n-butylamine as the SDA, focusing on the crystallization step in which the raw material composition is crystallized. As a result, they found that by controlling the pressure during the crystallization process and performing a predetermined treatment after the crystallization process, it is possible to obtain an MFI-type zeolite with excellent catalytic activity, durability, and handling properties.

[0009] In other words, the present invention is as described in the claims, and the gist of this disclosure is as follows: [1] An MFI-type zeolite having a molar ratio of silica to alumina of 40 to 150, an average primary crystal diameter of 0.1 μm to 5 μm, a standard deviation of volume particle size distribution of 15 μm or less, a structure directing agent content of 1.0 mass% or less, an alkali metal content of 0.05 mass% or less, and an acid content of 0.50 mmol / g or more. [2] The MFI type zeolite according to [1], wherein the crystallinity retention rate is 70% or more when the MFI type zeolite is hydrothermally treated at 1050°C for 3 hours in an atmosphere containing 50 volume% water vapor. [3] The MFI type zeolite according to [1] or [2], wherein the amount of water vapor adsorbed at a temperature of 25°C and a relative humidity of 90% is 15% by mass or less. [4] An MFI type zeolite according to any one of [1] to [3] above, wherein the amount of water vapor adsorbed at a temperature of 25°C and a relative humidity of 60% is 14% by mass or less. [5] BET specific surface area is 300m 2 / g or more 450m 2 An MFI-type zeolite according to any one of the above [1] to [4], wherein the amount is less than or equal to / g. [6] An MFI type zeolite according to any one of [1] to [5] above, wherein the aspect ratio of the primary particles is 3.0 or less. [7] The method for producing an MFI-type zeolite according to any one of [1] to [6] above, comprising a silica source, an alumina source, an alkali source, normal butylamine and water, and having a composition with a SiO2 / Al2O3 ratio of 40 or more and 200 or less, is hydrothermally treated at 100°C or higher and 180°C or lower, and 0.30 MPa or higher, and then further hydrothermally treated at 100°C or higher and 160°C or lower while reducing the pressure at a pressure reduction rate of 0.03 MPa / hour or higher; and a post-treatment step of performing a firing treatment and an acid treatment on the crystallized product obtained in the crystallization step. A method for producing an MFI-type zeolite.

Advantages of the Invention

[0010] According to the present disclosure, it is possible to provide an MFI-type zeolite having excellent catalytic activity and excellent durability and handling properties, and a method for producing the same.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, an example of an embodiment of the MFI-type zeolite of the present disclosure will be shown and described.

[0012] The terms in this embodiment are as follows.

[0013] "Zeolite" is a compound having a regular structure in which framework atoms (hereinafter, also referred to as "T atoms") are bonded via oxygen (O), and the T atoms are composed of at least one of metal atoms and metalloid atoms. Examples of the metal atom include one or more selected from the group consisting of aluminum (Al), titanium (Ti), iron (Fe), zinc (Zn), gallium (Ga), and tin (Sn). Examples of the metalloid atom include one or more selected from the group consisting of boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te).

[0014] A "zeolite-like substance" is a compound in which the T atom has a regular structure mediated by oxygen, and which contains at least one atom other than a metal or metalloid in the T atom. Examples of zeolite-like substances include aluminophosphate (AlPO) and silicoaluminophosphate (SAPO), which are complex phosphorus compounds containing phosphorus (P) as the T atom. In this embodiment, for convenience, a "zeolite-like substance" is distinguished from a "zeolite" in which the T atom consists of at least one of a metal atom and a metalloid atom.

[0015] The "regular structure" in zeolites and zeolite-like materials refers to zeolites that have a skeletal structure specified by the structural code (hereinafter also simply referred to as the "structural code") established by the Structure Commission of the International Zeolite Association (hereinafter also referred to as the "IZA"). For example, "MFI-type zeolite" is a zeolite that has a skeletal structure specified by the structural code "MFI". The skeletal structure of each zeolite can be identified, for example, by comparing it with the XRD pattern (hereinafter also referred to as the "reference pattern") described in Zeolite Framework Types on the International Zeolite Association's website (http: / / www.iza-structure.org / databases / ). Note that, with respect to the skeletal structure of zeolites, the terms skeletal structure, crystalline structure, and crystalline phase are used synonymously.

[0016] In this embodiment, the XRD pattern can be obtained from an XRD measurement under the following conditions. The XRD pattern can be measured using a general powder X-ray diffractometer (for example, instrument name: Ultima IV, manufactured by Rigaku). Acceleration current / voltage: 40mA / 40kV Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Continuous scan Scanning conditions: 10° / min Measurement range: 2θ = 5° to 40° Divergence vertical limiting slit: 10mm Divergence / Induction Slit: 1° Scattering slit: Open Light-receiving slit: Open Detector: Semiconductor detector (D / teX Ultra2) Filter: Not used

[0017] Aluminosilicate is a composite oxide having a structure consisting of repeating networks of aluminum (Al) and silicon (Si) mediated by oxygen (O). Among aluminosilicates, those having crystalline XRD peaks in their XRD pattern are called "crystalline aluminosilicates," while those not having crystalline XRD peaks are called "amorphous aluminosilicates." Zeolites in which the T atoms are substantially composed of aluminum (Al) and silicon (Si) are considered crystalline aluminosilicates. Here, "substantially composed of aluminum (Al) and silicon (Si)" means not only that the T atoms consist only of aluminum (Al) and silicon (Si), but also that they may contain T atoms other than aluminum (Al) and silicon (Si) to the extent that the effects of the present invention are achieved.

[0018] Crystalline XRD peaks are peaks whose peak top 2θ is identified and detected in XRD pattern analysis using common analysis software (e.g., Integral Analysis for Windows Version 6.2, Rigaku Corporation). Examples of crystalline XRD peaks with a full width at half maximum (FMAX) of 2θ = 0.50° or less are typical.

[0019] The composition in this embodiment, such as the molar ratio of silica to alumina (hereinafter also referred to as the "SiO2 / Al2O3 ratio"), can be determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES) using a general inductively coupled plasma atomic emission spectrometer (ICP instrument) (for example, instrument name: OPTIMA5300DV, manufactured by PerkinElmer). For compositional analysis, a sample solution obtained by dissolving the sample in a mixed aqueous solution of hydrofluoric acid and nitric acid can be used.

[0020] The MFI type zeolite of this embodiment will be described below. This disclosure includes any combination of each configuration and parameter disclosed herein, and the upper and lower limits of the values ​​disclosed herein also include any combination.

[0021] The MFI-type zeolite of this embodiment has an SiO2 / Al2O3 ratio of 40 to 150, an average primary crystal diameter of 0.1 μm to 5 μm, a standard deviation of volume particle size distribution of 15 μm or less, a structure directing agent content (hereinafter also referred to as "SDA content") of 1.0 mass% or less, an alkali metal content of 0.05 mass% or less, and an acid content of 0.50 mmol / g or more.

[0022] In the MFI-type zeolite of this embodiment, the SiO2 / Al2O3 ratio is between 40 and 150. This ratio allows the MFI-type zeolite of this embodiment to possess excellent catalytic activity while also exhibiting superior durability and handling properties. On the other hand, if the SiO2 / Al2O3 ratio of the MFI-type zeolite exceeds 150, the acid content decreases, leading to a decline in catalytic activity. Furthermore, if the SiO2 / Al2O3 ratio of the MFI-type zeolite is less than 40, the relative amount of aluminum, which is susceptible to the effects of high-temperature water vapor, increases, resulting in reduced durability. In this embodiment, durability refers to the ability of the MFI-type zeolite to maintain its crystal structure (how easily the crystal structure collapses) even when subjected to external physical factors such as heat (temperature) and moisture (humidity). This can be evaluated, for example, by the crystallinity retention rate described later.

[0023] The SiO2 / Al2O3 ratio of the MFI-type zeolite in this embodiment may be 40 to 150, but from the viewpoint of further improving catalytic activity and durability, it is preferable to have a ratio of 50 or higher, more preferably 60 or higher, and even more preferably 70 or higher. Furthermore, the SiO2 / Al2O3 ratio of the MFI-type zeolite in this embodiment may be 40 to 150, but from the viewpoint of further improving catalytic activity and durability, it is preferable to have a ratio of 120 or lower, more preferably 100 or lower, and even more preferably 90 or lower. The combination of the upper and lower limits of the SiO2 / Al2O3 ratio described above is arbitrary, but from the viewpoint of further improving catalytic activity and durability, the SiO2 / Al2O3 ratio of the MFI-type zeolite in this embodiment is preferably 50 to 120, more preferably 50 to 100, even more preferably 60 to 100, and particularly preferably 70 to 90.

[0024] In this embodiment, the MFI-type zeolite may contain T atoms other than aluminum (Al) and silicon (Si) as T atoms constituting the framework structure, provided that the SiO2 / Al2O3 ratio is 40 to 150. However, from the viewpoint of improving catalytic activity, it is preferable that the total molar ratio of aluminum and silicon in the T atoms is 95 mol% to 100 mol%, and it is more preferable that the T atoms consist substantially of aluminum (Al) and silicon (Si). In other words, it is more preferable that the MFI-type zeolite in this embodiment is an MFI-type crystalline aluminosilicate.

[0025] The MFI-type zeolite of this embodiment has an average primary crystal diameter of 0.1 μm to 5 μm. This average primary crystal diameter makes the MFI-type zeolite less susceptible to the effects of high-temperature water vapor, resulting in excellent durability. On the other hand, if the average primary crystal diameter of the MFI-type zeolite exceeds 5 μm, the effective area of ​​active sites due to acid sites decreases, potentially reducing its activity as a catalyst or adsorbent. Furthermore, if the average primary crystal diameter of the MFI-type zeolite is less than 0.1 μm, it becomes more susceptible to the effects of high-temperature water vapor, leading to reduced durability.

[0026] The average primary crystal diameter of the MFI-type zeolite in this embodiment may be 0.1 μm or more and 5 μm or less, but from the viewpoint of further improving durability, it is preferable to be 0.3 μm or more, more preferably 0.5 μm or more, and even more preferably 0.7 μm or more. Furthermore, the average primary crystal diameter of the MFI-type zeolite in this embodiment may be 0.1 μm or more and 5 μm or less, but from the viewpoint of further improving catalytic activity, it is preferable to be 3 μm or less, more preferably 1.5 μm or less, and even more preferably 1 μm or less. The combination of the upper and lower limits of the average primary crystal diameter as described above is arbitrary, but from the viewpoint of further improving catalytic activity and durability, the average primary crystal diameter of the MFI-type zeolite in this embodiment is preferably 0.1 μm or more and 3 μm or less, more preferably 0.3 μm or more and 3 μm or less, and even more preferably 0.5 μm or more and 1.5 μm or less.

[0027] The average primary crystal diameter is the average particle size of the primary particles contained in the zeolite. Primary particles contained in zeolite are the smallest units of particles that can be observed independently (observed without interruption of their outline) by scanning electron microscopy (hereinafter also referred to as "SEM") under the following conditions, and are different from aggregates of multiple particles (multiple primary particles). SEM observation can be performed using a general scanning electron microscope (for example, instrument name: JSM-IT200, manufactured by JEOL Ltd.). Acceleration voltage: 10±5kV Magnification: 10,000±5,000x

[0028] To measure the average primary crystal diameter, first, arbitrarily select 100 ± 10 primary particles whose contours are observed without interruption in the SEM observation image. Measure the distance between the two parallel lines that are tangent to the contour of each selected primary particle, and take the average of these distances as the average primary crystal diameter. The number of SEM observation images should be sufficient to observe the aforementioned number of primary particles; one or more SEM observation images may be used.

[0029] In the MFI-type zeolite of this embodiment, the standard deviation of the volume particle size distribution is 15 μm or less. Since the handling properties of zeolite tend to decrease as the variation in zeolite particle size increases, a zeolite exhibiting excellent handling properties is obtained if the standard deviation of the volume particle size distribution, which indicates the variation in zeolite particle size, is 15 μm or less. In the MFI-type zeolite of this embodiment, the standard deviation of the volume particle size distribution may be 15 μm or less, but from the viewpoint of further improving handling properties, it is preferable to be 12 μm or less, and more preferably 10 μm or less. In the MFI-type zeolite of this embodiment, the lower limit of the standard deviation of the volume particle size distribution is not particularly limited, but can be greater than 0 μm or 1 μm or more. The combination of the upper and lower limits of the standard deviation of the volume particle size distribution described above is arbitrary, but from the viewpoint of further improving handling performance, the standard deviation of the volume particle size distribution is preferably greater than 0 μm and 15 μm or less, more preferably greater than 0 μm and 12 μm or less, and even more preferably between 1 μm and 12 μm.

[0030] The volume particle size distribution is a particle size distribution based on volume measured using a general laser diffraction / scattering particle size distribution analyzer (for example, device name: Microtrac MT3300EXII, manufactured by Microtrac-Bell Co., Ltd.), and shows the particle size distribution of zeolite. Zeolites generally contain not only independently existing primary particles (non-aggregated primary particles) but also secondary particles such as aggregated particles, so the particle size of zeolite, which represents the size of these secondary particles, does not necessarily correlate with the particle size of the primary particles.

[0031] The following conditions can be used for measurement using a laser diffraction / scattering particle size distribution analyzer. For the sample to be measured using a laser diffraction / scattering particle size distribution analyzer, a sample prepared by suspending zeolite in pure water and dispersing it for 2 minutes using an ultrasonic homogenizer set to a frequency of 20 kHz can be used. Measurement range: 0.02~2000μm Particle refractive index: 1.66 Particle permeability: permeation Particle shape: non-spherical Solvent type: Water (pure water) Solvent refractive index: 1.333 Ultrasonic pretreatment: Frequency 20kHz, 2 minutes

[0032] The standard deviation of the volume particle size distribution is an indicator of the variation in particle size of the zeolite. In this embodiment, it can be calculated from the following formula (1) using the particle size at which the cumulative volume from the smallest particles accounts for 90% of the volume particle size distribution (hereinafter also referred to as "D90") and the particle size at which the cumulative volume from the smallest particles accounts for 10% of the volume particle size distribution (hereinafter also referred to as "D10"). As can be understood from the following formula (1), the larger the standard deviation of the volume particle size distribution, the greater the variation in particle size of the zeolite. The particle size at which the cumulative volume from the smallest particles accounts for 50% of the volume particle size distribution (hereinafter also referred to as "D50") is also called the median diameter. Standard deviation [μm]=(D90[μm]-D10[μm]) / 2 ··· (1)

[0033] The D90 of the MFI-type zeolite in this embodiment is not particularly limited as long as the standard deviation of the volume particle size distribution is 15 μm or less, but from the viewpoint of further improving handling performance, it is preferable that it is 3 μm or more, and more preferably 10 μm or more. Also, the D90 of the MFI-type zeolite in this embodiment is not particularly limited as long as the standard deviation of the volume particle size distribution is 15 μm or less, but from the viewpoint of further improving handling performance, it is preferable that it is 50 μm or less, and more preferably 30 μm or less. The combination of the upper and lower limits of D90 as described above is arbitrary, but from the viewpoint of further improving handling performance, the D90 of the MFI-type zeolite in this embodiment is preferably 3 μm or more and 50 μm or less, more preferably 3 μm or more and 30 μm or less, and more preferably 10 μm or more and 30 μm or less.

[0034] The D10 of the MFI-type zeolite in this embodiment is not particularly limited as long as the standard deviation of the volume particle size distribution is 15 μm or less, but from the viewpoint of further improving handling, it is preferably 0.5 μm or more, and more preferably 1 μm or more. Also, the D10 of the MFI-type zeolite in this embodiment is not particularly limited as long as the standard deviation of the volume particle size distribution is 15 μm or less, but from the viewpoint of further improving handling, it is preferably 10 μm or less, and more preferably 5 μm or less. The combination of the upper and lower limits of D10 as described above is arbitrary, but from the viewpoint of further improving handling, the D10 of the MFI-type zeolite in this embodiment is preferably 0.5 μm or more and 10 μm or less, more preferably 1 μm or more and 10 μm or less, and more preferably 1 μm or more and 5 μm or less.

[0035] The SDA content of the MFI-type zeolite in this embodiment is 1.0% by mass or less. By having an SDA content of 1.0% by mass or less, the MFI-type zeolite in this embodiment can suppress the inhibition of contact with the reaction substrate by SDA and exhibit excellent catalytic activity. On the other hand, if the SDA content exceeds 1.0% by mass, SDA inhibits contact with the reaction substrate, and the catalytic activity decreases.

[0036] The SDA content of the MFI-type zeolite in this embodiment may be 1.0% by mass or less, but it is preferable to have 0.8% by mass or less, 0.6% by mass or less, or 0.4% by mass or less, in order to further improve catalytic activity. The lower limit of the SDA content is not particularly limited, but for example, it may be 0% by mass or more, greater than 0% by mass, or 0.1% by mass or more. The combination of the upper and lower limits of the SDA content described above is arbitrary, but the SDA content of the MFI-type zeolite in this embodiment is preferably 0% by mass or more and 1.0% by mass or greater than 0% by mass and 1.0% by mass or less, more preferably 0% by mass or more and 0.8% by mass or greater than 0% by mass and 0.8% by mass or less, and even more preferably 0.1% by mass or more and 0.6% by mass or less, in order to further improve catalytic activity. In this embodiment, a content of 0% by mass or 0 mol% means that the component is substantially absent, and substantially absent means that the component is not detected (below the detection limit).

[0037] The SDA content can be determined by dividing the mass of SDA contained in the MFI-type zeolite (hereinafter also referred to as "SDA mass") by the mass of the MFI-type zeolite (hereinafter also referred to as "zeolite mass") and converting this to a percentage. For determining the SDA content, the dry mass of the MFI-type zeolite dried in an air atmosphere at 110°C for 4 hours should be used. For determining the SDA content, the change in mass when the MFI-type zeolite is heated from 300°C to 700°C should be used. The change in mass when the MFI-type zeolite is heated can be measured using a general differential thermogravimetric analyzer (e.g., STA 2500 Regulus, manufactured by NETZSCH) under the following conditions. Atmosphere: air Atmospheric flow rate: 20cc / min Heating rate: 10°C / min Measurement temperature: 20~800℃

[0038] In this embodiment, the mass change (mass decrease) of the MFI-type zeolite up to 300°C is determined to be a mass change due to the desorption of adsorbed water, and the mass change (mass decrease) of the MFI-type zeolite above 700°C is determined to be a mass change due to the condensation of silanols at the polymorphic bonding surfaces of the MFI-type zeolite. Therefore, in this embodiment, the mass change (mass decrease) of the MFI-type zeolite when heated from 300°C to 700°C is determined to be a mass change due to at least one of the decomposition and combustion of SDA.

[0039] The alkali metal content of the MFI-type zeolite in this embodiment is 0.05% by mass or less. By having an alkali metal content of 0.05% by mass or less, the MFI-type zeolite in this embodiment can suppress the destruction of its crystal structure by alkali metals in a high-temperature atmosphere containing water vapor (hereinafter also referred to as a "hydrothermal atmosphere"), and can exhibit excellent durability. On the other hand, if the alkali metal content exceeds 0.05% by mass, the destruction of the crystal structure by alkali metals in a hydrothermal atmosphere becomes more likely to progress, resulting in reduced durability.

[0040] The alkali metal content of the MFI-type zeolite in this embodiment may be 0.05% by mass or less, but from the viewpoint of further improving durability, it is preferable to have 0.03% by mass or less, or 0.01% by mass or less. The lower limit of the alkali metal content is not particularly limited, but for example, it may be 0% by mass or more, or greater than 0% by mass. The combination of the upper and lower limits of the alkali metal content described above is arbitrary, but from the viewpoint of further improving durability, the alkali metal content of the MFI-type zeolite in this embodiment is preferably 0% by mass or more and 0.05% by mass or greater than 0% by mass and 0.05% by mass or less, more preferably 0% by mass or more and 0.03% by mass or greater than 0% by mass and 0.03% by mass or less, and even more preferably 0% by mass or more and 0.01% by mass or greater than 0% by mass and 0.01% by mass or less.

[0041] The alkali metal content is the ratio of the mass of alkali metal (M) contained in the MFI-type zeolite to the total mass of silicon (Si) converted to SiO2, aluminum (Al) converted to Al2O3, and alkali metal (M) converted to M2O, and can be calculated using the following formula (6). In formula (6), SiO2 represents the mass of silicon (Si) contained in the MFI-type zeolite converted to SiO2 [g], Al2O3 represents the mass of aluminum (Al) contained in the MFI-type zeolite converted to Al2O3 [g], M2O represents the mass of alkali metal (M) contained in the MFI-type zeolite converted to M2O [g], and M represents the mass of alkali metal (M) contained in the MFI-type zeolite [g]. Alkali metal content [mass%] ={M / (SiO2+Al2O3+M2O)}×100 ··· (6)

[0042] Here, the mass of alkali metal (M) should be the total mass of the alkali metals if the zeolite contains two or more alkali metals. For example, if the zeolite contains sodium (Na) and potassium (K) as alkali metals (M), the mass of alkali metal (M) should be the total mass of sodium (Na) and potassium (K).

[0043] Examples of alkali metals that may be included in the MFI-type zeolite of this embodiment include one or more selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs), and further, at least one of sodium (Na) and potassium (K) may be included, and further, sodium (Na) may be included.

[0044] The alkali metals that can be contained in the MFI-type zeolite of this embodiment are not particularly limited and may be compounds (e.g., oxides), metals (elemental), ions, alloys, or two or more of these states. From the viewpoint of further improving catalytic activity, the alkali metals are preferably in the form of ions.

[0045] In the MFI-type zeolite of this embodiment, the acid content is 0.50 mmol / g or more. Since the acid sites present in the MFI-type zeolite become active sites as catalysts, the MFI-type zeolite of this embodiment can exhibit excellent catalytic activity when the acid content is 0.50 mmol / g or more. In the MFI-type zeolite of this embodiment, the acid content should be 0.50 mmol / g or more, but from the viewpoint of further improving catalytic activity, it is preferable to have an acid content of 0.60 mmol / g or more, and more preferably 0.70 mmol / g or more. In the MFI-type zeolite of this embodiment, the upper limit of the acid content is not particularly limited, but can be 2.0 mmol / g or less, or 1.5 mmol / g or less. The combination of the upper and lower limits of the acid amount mentioned above is arbitrary, but from the viewpoint of further improving catalytic activity, the acid amount is preferably 0.50 mmol / g or more and 2.0 mmol / g or less, more preferably 0.50 mmol / g or more and 1.5 mmol / g or less, and even more preferably 0.60 mmol / g or more and 1.5 mmol / g or less.

[0046] The acid amount is the amount of acid sites present in the zeolite per unit mass. The acid amount can be measured by the ammonia-TPD method using a general catalyst analyzer (for example, device name: BELCAT II, manufactured by Microtrac BEL Corporation). Zeolite saturated with ammonia adsorbed at room temperature (25 °C) is heated at 100 °C for 1 hour in an inert gas to remove ammonia not adsorbed on the zeolite from the treatment atmosphere, and then the temperature is raised from 100 °C to 600 °C at a heating rate of 10 °C / min, and the amount of ammonia released from the zeolite during the heating process (hereinafter, also referred to as "ammonia release amount") [mmol] is measured. Considering that the ammonia release amount [mmol] is the amount of acid sites [mmol] present in the zeolite (the amount of ammonia adsorbed on the acid sites of the zeolite) [mmol], the acid amount can be determined from the mass [g] of the zeolite used for ammonia adsorption and the amount of acid sites [mmol] (ammonia release amount [mmol]) present in the zeolite. In addition, for the zeolite (measurement sample) saturated with ammonia adsorption, zeolite pretreated at 500 °C for 1 hour in an inert gas can be used. Moreover, examples of the inert gas used in the ammonia-TPD method include at least one of helium and argon gases, and helium is preferred.

[0047] The MFI-type zeolite of this embodiment is not particularly limited, but from the perspective of further improving the catalytic activity, the BET specific surface area is preferably 300 m 2 / g or more, and more preferably 330 m 2 / g or more. Also, from the perspective of further improving the durability, the BET specific surface area of the MFI-type zeolite of this embodiment is preferably 450 m 2 / g or less, and more preferably 400 m 2 / g or less. The combination of the upper and lower limits of the BET specific surface area described above is arbitrary, but from the perspective of further improving the catalytic activity and durability, the BET specific surface area is preferably 300 m 2 / g or more and 450 m 2 / g or less, and more preferably 300 m 2 / g or more and 400 m 2It is more preferable that it be less than or equal to / g, and 330m 2 / g or more 400m 2 It is even more preferable that the value be less than or equal to / g.

[0048] The BET specific surface area can be determined using a general specific surface area measuring device (e.g., device name: BELSORP-miniII, manufactured by Microtrac-Bell Co., Ltd.) by the BET single-point method using nitrogen adsorption in accordance with JIS Z 8830:2013. For the zeolite (measurement sample) used to measure the BET specific surface area, a zeolite pre-treated at 350°C for 2 hours in a vacuum atmosphere (10 Pa or less) can be used.

[0049] The MFI type zeolite of this embodiment is not particularly limited, but from the viewpoint of further improving durability, the aspect ratio (L1 / L2) of the primary particles, determined by the following formula (2), is preferably 1.2 or higher, and more preferably 1.5 or higher. Furthermore, from the viewpoint of further improving handling properties, the aspect ratio (L1 / L2) of the primary particles of the MFI type zeolite of this embodiment is preferably 3.0 or lower, and more preferably 2.0 or lower. The combination of the upper and lower limits of the aspect ratio (L1 / L2) of the primary particles described above is arbitrary, but from the viewpoint of further improving durability and handling properties, the aspect ratio (L1 / L2) of the primary particles is preferably 1.2 or higher and 3.0 or lower, more preferably 1.2 or higher and 2.0 or lower, and even more preferably 1.5 or higher and 2.0 or lower. Aspect ratio [-] = Average longest diameter L1 [μm] / Average shortest diameter L2 [μm] ··· (2)

[0050] The average longest diameter L1 [μm] in equation (2) above can be determined by arbitrarily selecting 100 ± 10 primary particles whose contours are observed without interruption in the SEM observation image, measuring the distance between the two parallel lines that are tangent to the contour of each selected primary particle to obtain the longest distance, and averaging these distances. Similarly, the average shortest diameter L2 [μm] in equation (2) above can be determined by arbitrarily selecting 100 ± 10 primary particles whose contours are observed without interruption in the SEM observation image, measuring the distance between the two parallel lines that are tangent to the contour of each selected primary particle to obtain the shortest distance, and averaging these distances. As is clear from the average longest diameter L1 and average shortest diameter L2, the aspect ratio (L1 / L2) obtained by equation (2) above is the aspect ratio of primary particles and differs from the aspect ratio of secondary particles such as aggregated particles. The number of SEM observation images used to determine the average longest diameter L1 and average shortest diameter L2 should be such that the aforementioned number of primary particles can be observed; one or more SEM observation images may be used. Furthermore, the SEM observation method (conditions) can be the same as the SEM observation method (conditions) used to calculate the average primary crystal diameter.

[0051] In this embodiment, from the viewpoint of further improving durability, the crystallinity retention rate (hereinafter simply referred to as "crystallinity retention rate") when the MFI type zeolite is subjected to hydrothermal treatment at 1050°C for 3 hours in an atmosphere containing 50% by volume of water vapor (hereinafter also referred to as "hydrothermal durability treatment") is preferably 65% ​​or more, and more preferably 70% or more. The upper limit of the crystallinity retention rate is not particularly limited, but examples include 100% or less, or 95% or less. The above-mentioned combination of the upper and lower limits of the crystallinity retention rate is arbitrary, but from the viewpoint of further improving durability, the crystallinity retention rate is preferably 65% ​​or more and 100% or less, more preferably 65% ​​or more and 95% or less, and even more preferably 70% or more and 95% or less.

[0052] The crystallinity retention rate can be calculated using the following equation (3), with respect to the integrated intensity of XRD peaks in the XRD pattern of zeolite before hydrothermal treatment where the diffraction angle 2θ is in the range of 22° to 25° (hereinafter also referred to as "crystallinity before hydrothermal treatment (I0)") and the integrated intensity of XRD peaks in the XRD pattern of zeolite after hydrothermal treatment where the diffraction angle 2θ is in the range of 22° to 25° (hereinafter also referred to as "crystallinity after hydrothermal treatment (I1)"). Since the XRD peaks in the XRD pattern where the diffraction angle 2θ is in the range of 22° to 25° are the main peaks of MFI-type zeolite, the higher the crystallinity retention rate, the less likely the crystal structure is to collapse even after hydrothermal treatment, and the higher the durability. Crystallinity maintenance rate [%]=I1 / I0×100 (3) In equation (3) above, I0 represents the degree of crystallinity before hydrothermal treatment, and I1 represents the degree of crystallinity after hydrothermal treatment.

[0053] The hydrothermal endurance treatment performed on zeolite to determine the crystallinity retention rate can be carried out in an atmosphere containing 50% by volume of water vapor, but it is preferable to carry it out in an atmosphere containing 50% by volume of water vapor and 50% by volume of air. An atmosphere containing 50% by volume of water vapor is an atmosphere in which 50% by volume of water vapor is introduced relative to the total volume of all introduced gases (including water vapor) introduced into the atmosphere for hydrothermal endurance treatment. Specifically, an atmosphere containing 50% by volume of water vapor can be described as an atmosphere in which 150°C water vapor at a flow rate of 15 L / min and room temperature (25°C) air at a flow rate of 15 L / min are introduced.

[0054] The XRD patterns of zeolites obtained to determine the crystallinity retention rate should be acquired under the same conditions as those used to identify the crystal structure. Furthermore, the integrated intensity of XRD peaks with diffraction angles 2θ between 22° and 25° can be calculated by analyzing the XRD pattern using general analysis software (e.g., Integral Analysis for Windows Version 6.2, Rigaku Corporation). The following analysis conditions should be used for analyzing the XRD pattern. Background removal method: Sonneveld-visser method Peak width threshold: 0.10 Intensity threshold: 1.00 Peak calculation method: Peak top method

[0055] The MFI type zeolite of this embodiment is not particularly limited, but from the viewpoint of further improving durability, it is preferable that the amount of water vapor adsorbed at a temperature of 25°C and a relative humidity of 90% (hereinafter also referred to as "90% water vapor adsorption amount") is 15% by mass or less, more preferably 14% by mass or less, and even more preferably 13% by mass or less. The lower limit of the 90% water vapor adsorption amount is not particularly limited, but can be 0% by mass or more, or 3% by mass or more. The combination of the upper and lower limits of the 90% water vapor adsorption amount described above is arbitrary, but from the viewpoint of further improving durability, it is preferable that the 90% water vapor adsorption amount is 0% by mass or more and 15% by mass or less, more preferably 0% by mass or more and 14% by mass or less, and even more preferably 3% by mass or more and 13% by mass or less.

[0056] The MFI type zeolite of this embodiment is not particularly limited, but from the viewpoint of further improving durability, it is preferable that the amount of water vapor adsorbed at a temperature of 25°C and a relative humidity of 60% (hereinafter also referred to as "60% water vapor adsorption amount") is 14% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less. The lower limit of the 60% water vapor adsorption amount is not particularly limited, but can be 0% by mass or more, or 3% by mass or more. The combination of the upper and lower limits of the 60% water vapor adsorption amount described above is arbitrary, but from the viewpoint of further improving durability, it is preferable that the 60% water vapor adsorption amount is 0% by mass or more and 14% by mass or less, more preferably 0% by mass or more and 12% by mass or less, and even more preferably 3% by mass or more and 10% by mass or less.

[0057] The 90% water vapor adsorption amount and the 60% water vapor adsorption amount can be determined from the following formula (4). In the following formula (4), W1 (amount of water adsorbed on the MFI type zeolite by water vapor adsorption treatment [g]) can be measured using a general water vapor adsorption amount measuring device (for example, device name: BELSORP-MAXII, manufactured by Microtrac-Bel Co., Ltd.). It is thought that most of the water adsorbed on the MFI type zeolite is water adsorbed on silanol defects (Si-OH defects) formed in the zeolite's skeletal structure. Since the crystal structure is more easily destroyed by heat the more silanol defects there are, it can be said that the lower the water vapor adsorption amount of the MFI type zeolite, the higher its heat resistance. Water vapor adsorption amount [%] = W1 / W0 × 100 ... (4) In equation (4) above, W0 represents the mass [g] of the MFI-type zeolite before water vapor adsorption treatment, and W1 represents the amount of water [g] adsorbed onto the MFI-type zeolite by water vapor adsorption treatment.

[0058] For the MFI type zeolite (measurement sample) to be subjected to water vapor adsorption treatment, an MFI type zeolite that has been pre-treated at 350°C for 2 hours in a vacuum atmosphere (10 Pa or less) can be used. In the above equation (4), W0 can be determined by measuring the mass of the measurement sample with a general water vapor adsorption amount measuring device before the water vapor adsorption treatment. The water vapor adsorption treatment performed to determine the 90% water vapor adsorption amount (hereinafter also referred to as "90% water vapor treatment") is performed in an atmosphere in which the measurement sample is treated at 10 -5 This process involves reducing the pressure to below Pa, changing the temperature from 25°C to 90% relative humidity, and then exposing the sample to an atmosphere of 25°C and 90% relative humidity until the amount of water vapor adsorbed by the sample reaches equilibrium. For W1 (amount of water adsorbed on MFI-type zeolite by water vapor adsorption treatment [g]) to determine the 90% water vapor adsorption amount, the amount of water adsorbed on the sample by the 90% water vapor treatment, measured by the constant volume method, should be used. Furthermore, the water vapor adsorption treatment performed to determine the 60% water vapor adsorption amount (hereinafter also referred to as "60% water vapor treatment") involves changing the atmosphere in which the sample is treated to 10 -5This process involves reducing the pressure to below Pa, changing the temperature and relative humidity from 0% to 60% at 25°C, and then exposing the sample to an atmosphere of 25°C and 60% relative humidity until the amount of water vapor adsorbed by the sample reaches equilibrium. For W1 (amount of water adsorbed on the MFI type zeolite by the water vapor adsorption treatment [g]) to determine the 60% water vapor adsorption amount, the amount of water adsorbed on the sample by the 60% water vapor treatment can be the value measured by the constant volume method. The relative humidity can be determined from the ratio of the water vapor pressure at adsorption equilibrium (adsorption equilibrium pressure) P (kPa) to the saturated vapor pressure of water vapor P0 (kPa) at 25°C (P / P0 × 100). Furthermore, if the pressure change remains within ±0.3% for 300 seconds during the water vapor adsorption treatment, it can be assumed that adsorption equilibrium has been reached.

[0059] The MFI-type zeolite of this embodiment, when used as a slurry with a solid content concentration of 40% by mass, exhibits a shear rate of 100 s. -1 The viscosity is preferably 100 mPa·s or less, more preferably 80 mPa·s or less, and even more preferably 60 mPa·s or less. Shear rate 100 s -1 The viscosity at which the MFI-type zeolite of this embodiment is made into a slurry is 100 mPa·s or less, which makes it easier to apply to a substrate such as a carrier. Shear rate 100 s -1 The lower limit of viscosity is not particularly limited, but for example, it may be 5 mPa·s or higher, or 10 mPa·s or higher. The combination of the upper and lower limits of viscosity mentioned above is arbitrary, but from the viewpoint of further improving the handling properties when it is made into a slurry, a shear rate of 100 s is recommended. -1 The viscosity is preferably 5 mPa·s to 100 mPa·s, more preferably 5 mPa·s to 80 mPa·s, and even more preferably 10 mPa·s to 60 mPa·s.

[0060] Shear rate 100s -1The viscosity can be measured using a general-purpose viscometer (for example, device name: MCR 92, manufactured by Anton Paar) by the following method: Mix MFI type zeolite with pure water to make a slurry with a solid content concentration of 40% by mass (hereinafter also referred to as "sample slurry"). Drop 2 mL of the sample slurry onto the stage of the measuring device fitted with a parallel plate type measuring jig (PP50), and measure at a shear rate of 100 s. -1 The viscosity should be measured. For the measurement, the stage temperature should be 20°C, and the gap between the measuring fixture and the stage should be 0.2 mm.

[0061] The solid content concentration of the slurry is the mass ratio of zeolite to the slurry and can be determined from the following formula (5). In formula (5), the slurry mass [g] is the value obtained by measuring the mass of the slurry. Also, in formula (5), the zeolite mass [g] is the value obtained by drying the slurry after measuring the slurry mass to obtain the solid content, and then measuring the mass after treating it in air at 600°C for 1 hour. Solid content concentration [mass%] = (Zeolite mass [g] / Slurry mass [g]) × 100 ... (5)

[0062] The MFI-type zeolite of this embodiment is not limited to its applications and can be used in the same applications as conventionally known MFI-type zeolites, for example, in at least one of the applications of a catalyst and an adsorbent. The adsorbent can also function as a separation agent for separating specific components. Examples of catalysts using MFI-type zeolites include a toluene disproportionation catalyst for catalyzing toluene disproportionation, a xylene isomerization catalyst for catalyzing xylene isomerization, an MTO (Methanol To Olefins) reaction catalyst, a polyolefin decomposition catalyst for catalyzing polyolefin decomposition reactions, and an MTA (Methanol To Aromatics) reaction catalyst. Examples of adsorbents using MFI-type zeolites include a VOC adsorbent for adsorbing VOCs, an aromatic compound adsorbent for adsorbing aromatic compounds, and an SF6 adsorbent for adsorbing SF6. The MFI-type zeolite of this embodiment has excellent catalytic activity, as well as excellent durability and handling properties. Therefore, its catalytic activity does not easily deteriorate even in harsh environments, and it is easy to mold and process when used for a predetermined application.

[0063] Next, the method for producing the MFI-type zeolite of this embodiment will be described.

[0064] The method for producing the MFI-type zeolite of this embodiment includes a step of hydrothermally treating a composition (hereinafter also referred to as the "raw material composition") containing a silica source, an alumina source, an alkali source, n-butylamine, and water, and having an SiO2 / Al2O3 ratio of 40 to 200, at 100°C to 180°C and 0.30 MPa or higher, followed by further hydrothermally treating it at 100°C to 160°C while reducing the pressure at a depressurization rate of 0.03 MPa / hour or higher (hereinafter also referred to as the "crystallization step"), and a step of calcination and acid treatment on the crystallized product obtained in the crystallization step (hereinafter also referred to as the "post-treatment step"). The MFI-type zeolite of this embodiment is obtained as a crystallized product by the production method including the crystallization step and the post-treatment step.

[0065] The silica source contained in the raw material composition is at least one of a silicon-containing compound and silicon (Si), and examples include one or more selected from the group consisting of silica sol, fumed silica, colloidal silica, precipitated silica, sodium silicate, potassium silicate, amorphous silica, crystalline aluminosilicate, and amorphous aluminosilicate, with at least one of amorphous silica and amorphous aluminosilicate being preferred, and amorphous aluminosilicate being more preferred.

[0066] The alumina source contained in the raw material composition is at least one of an aluminum-containing compound and aluminum, for example, one or more selected from the group consisting of aluminum hydroxide, aluminum oxide, aluminum sulfate, sodium aluminate, aluminum chloride and amorphous aluminosilicate, preferably one or more selected from the group consisting of aluminum oxide, aluminum sulfate, sodium aluminate and amorphous aluminosilicate, more preferably at least one of aluminum sulfate and amorphous aluminosilicate, and even more preferably amorphous aluminosilicate.

[0067] Furthermore, if other starting materials in the raw material composition besides the alumina source contain aluminum, these may also be used as the alumina source. For example, if the silica source contains aluminum, the silica source can be considered simultaneously as the alumina source. From the viewpoint of improving handling properties, the substances that are the alumina source and the silica source are preferably amorphous aluminosilicate. From the viewpoint of further improving the catalytic activity of the MFI-type zeolite produced, the SiO2 / Al2O3 ratio of the amorphous aluminosilicate is preferably 40 to 150, more preferably 40 to 120, and even more preferably 50 to 120.

[0068] The alkali source is at least one of a compound containing an alkali metal element and an alkali metal. Examples of compounds containing alkali metal elements include one or more selected from the group consisting of alkali metal hydroxides, carbonates, sulfates, chlorides, bromides, silicates, and iodides, preferably one or more selected from the group consisting of hydroxides, chlorides, bromides, and iodides, and more preferably a hydroxide. Examples of alkali metal elements included in the alkali source include one or more selected from the group consisting of sodium, potassium, rubidium, and cesium, preferably at least one of sodium and potassium, and more preferably sodium.

[0069] The raw material composition includes n-butylamine (hereinafter also referred to as "NBA") as an SDA source. By including NBA as an SDA source in the raw material composition, the MFI-type zeolite of this embodiment can be produced which has excellent catalytic activity as well as excellent durability and handling properties. On the other hand, in conventional methods for producing MFI-type zeolites that use only quaternary ammonium cations as SDA, the average primary crystal diameter of the produced MFI-type zeolite becomes smaller, resulting in reduced durability. Furthermore, in conventional methods for producing MFI-type zeolites that use only quaternary ammonium cations as SDA, depending on the raw materials used, the particle size variation of the produced MFI-type zeolite becomes large, resulting in reduced handling properties.

[0070] The raw material composition may contain, in addition to NBA, SDA sources other than NBA that aim for an MFI structure, but from the viewpoint of further improving the durability of the MFI-type zeolite produced, it is preferable to include only NBA as the SDA source. Examples of SDA sources other than NBA that aim for an MFI structure include one or more selected from the group consisting of amines, glycerols, alcohols, and morpholins. Examples of amines that aim for an MFI structure include one or more substances selected from the group consisting of dinormal butylamine, tributylamine, dinormal propylamine, tripropylamine, dipropylenetriamine, dihexamethylenetriamine, triethylenetetramine, diethylenetriamine, ethanolamine, and propanolamine.

[0071] The water contained in the raw material composition may be one or more selected from the group consisting of distilled water, deionized water, and pure water. Furthermore, water derived from other starting materials contained in the raw material composition, such as solvents and aqueous compounds, can also be considered as water contained in the raw material composition.

[0072] The raw material composition may consist only of the silica source, alumina source, alkali source, NBA, and water as described above, or it may further contain other raw materials, but it is preferable that it does not contain fluorine (F) and fluorine-containing compounds (hereinafter also referred to as "fluorine, etc."). Fluorine, etc. is particularly corrosive, and manufacturing methods using it require special manufacturing equipment that exhibits corrosion resistance, which tends to increase manufacturing costs. For this reason, it is preferable that the raw material composition does not contain fluorine.

[0073] The SiO2 / Al2O3 ratio in the raw material composition is between 40 and 200. By having an SiO2 / Al2O3 ratio of 40 to 200 in the raw material composition, the MFI-type zeolite of this embodiment can be produced with excellent catalytic activity, durability, and handling properties. On the other hand, if the SiO2 / Al2O3 ratio in the raw material composition exceeds 200, the acid content of the produced MFI-type zeolite decreases, resulting in reduced catalytic activity. Furthermore, if the SiO2 / Al2O3 ratio in the raw material composition is less than 40, the particle size variation of the produced MFI-type zeolite increases, reducing handling properties. Additionally, the average primary crystal diameter of the produced MFI-type zeolite decreases, and the relative amount of aluminum, which is susceptible to high-temperature steam, increases, leading to reduced durability.

[0074] The raw material composition preferably has the following molar composition in order to facilitate the production of the MFI-type zeolite of this embodiment. In the molar composition described later, the NBA / SiO2 ratio represents the molar ratio of NBA to silica, the M / SiO2 ratio represents the molar ratio of alkali metal to silica, the OH / SiO2 ratio represents the molar ratio of hydroxide ions to silica, and the H2O / SiO2 ratio represents the molar ratio of water to silica. In the M / SiO2 ratio, if the raw material composition contains two or more alkali metals, M may be the sum of those alkali metals. For example, if sodium (Na) and potassium (K) are included as alkali metals, M will be (Na + K). SiO2 / Al2O3 ratio = 40 or higher or 45 or higher, 100 or less, 150 or less, or 200 or less NBA / SiO2 ratio = 0.01 or higher, 0.05 or higher, 0.10 or higher, and 0.30 or less, 0.50 or less, 0.70 or less M / SiO2 ratio = 0.01 or higher, 0.05 or higher, or 0.10 or higher, 0.30 or less, 0.50 or less, or 0.70 or less OH / SiO2 ratio = 0.01 or higher, 0.05 or higher, or 0.10 or higher, 0.30 or less, 0.50 or less, or 0.70 or less H2O / SiO2 ratio = 2 or higher, 5 or higher, 8 or higher, and 100 or less, 50 or less, 15 or less

[0075] Particularly preferred compositions of the raw material include the following molar compositions. SiO2 / Al2O3 ratio =40 or more and 150 or less Preferably 40 to 100 More preferably 45 to 100 NBA / SiO2 ratio = 0.01 or more and 0.30 or less Preferably 0.05 or more and 0.30 or less M / SiO2 ratio = 0.01 or more and 0.30 or less Preferably 0.05 or more and 0.30 or less OH / SiO2 ratio = 0.01 or more and 0.30 or less, Preferably 0.05 or more and 0.30 or less H2O / SiO2 ratio =5 or more and 50 or less, Preferably 8 to 15

[0076] In the crystallization process, the raw material composition is subjected to hydrothermal treatment under predetermined conditions. The hydrothermal treatment of the raw material composition may be carried out in the presence or absence of seed crystals, but from the viewpoint of shortening the hydrothermal treatment time, it is preferable to carry it out in the presence of seed crystals. An example of a method for hydrothermally treating the raw material composition in the presence of seed crystals is to hydrothermally treat a mixture obtained by mixing the raw material composition and seed crystals.

[0077] The amount of seed crystals added to the raw material composition can be appropriately set within the range in which the MFI-type zeolite of this embodiment can be produced. However, the ratio of the total mass of aluminum and silicon in the seed crystals (when converted to Al2O3 and SiO2, respectively) to the total mass of aluminum and silicon in the raw material composition (without seed crystals) (hereinafter also referred to as "seed crystal content") when converted to Al2O3 and SiO2, respectively, can be, for example, 0% by mass or more, greater than 0% by mass or 1% by mass or more, and 20% by mass or less or 10% by mass or less. The above-mentioned combination of upper and lower limits for the seed crystal content is arbitrary, but the seed crystal content can be 0% by mass or more and 20% by mass or less, greater than 0% by mass and 20% by mass or less, or 1% by mass or more and 10% by mass or less.

[0078] The seed crystal added to the raw material composition can be any zeolite having a microstructure (composite building unit (CBU)) in its skeletal structure that is common to MFI-type zeolite, and is not particularly limited, but is preferably an MFI-type zeolite. The MFI-type zeolite used as the seed crystal preferably has an SiO2 / Al2O3 ratio of 20 to 3000, as this makes the MFI-type zeolite of this embodiment easier to manufacture.

[0079] In the crystallization process, the raw material composition is subjected to hydrothermal treatment at 100°C to 180°C and under a pressure of 0.30 MPa or higher, followed by further hydrothermal treatment at 100°C to 160°C while reducing pressure at a rate of 0.03 MPa / hour or higher. In the following explanation, the hydrothermal treatment performed at 100°C to 180°C and under a pressure of 0.30 MPa or higher is referred to as "pressurized hydrothermal treatment," and the hydrothermal treatment performed at 100°C to 160°C while reducing pressure at a rate of 0.03 MPa / hour or higher is also referred to as "reduced-pressure hydrothermal treatment." By performing pressurized and reduced-pressure hydrothermal treatments under these conditions, the average primary crystal diameter and standard deviation of the manufactured MFI-type zeolite tend to be as described above, and the durability and handling properties of the manufactured MFI-type zeolite tend to improve.

[0080] The pressurized hydrothermal treatment is carried out at a temperature of 100°C to 180°C. By performing the pressurized hydrothermal treatment at a temperature of 100°C to 180°C, the MFI-type zeolite of this embodiment can be produced. If the pressurized hydrothermal treatment temperature is below 100°C, the raw material composition does not crystallize easily, and if the pressurized hydrothermal treatment temperature exceeds 180°C, the particle size variation of the produced MFI-type zeolite increases, reducing its handling properties. The pressurized hydrothermal treatment temperature can be 100°C to 180°C, but from the viewpoint of further promoting the crystallization of the raw material composition, it is preferable to have a temperature of 110°C or higher, and more preferably 120°C or higher. Furthermore, although the pressurized hydrothermal treatment temperature can be 100°C to 180°C, from the viewpoint of further suppressing the particle size variation of the produced MFI-type zeolite, it is preferable to have a temperature of 170°C or lower, and more preferably 160°C or lower. While the combination of the upper and lower limits of the processing temperature for the pressurized hydrothermal treatment described above is arbitrary, from the viewpoint of further promoting the crystallization of the raw material composition and further suppressing variations in the particle size of the MFI-type zeolite produced, the processing temperature for the pressurized hydrothermal treatment is preferably 110°C to 180°C, and more preferably 110°C to 160°C.

[0081] The pressurized hydrothermal treatment is performed at a pressure of 0.30 MPa or higher. By performing the pressurized hydrothermal treatment at a pressure of 0.30 MPa or higher, the MFI type zeolite of this embodiment can be manufactured. If the pressurized hydrothermal treatment pressure is less than 0.30 MPa, the crystallinity of the manufactured MFI type zeolite will be low, and the catalytic activity and durability will decrease. The pressurized hydrothermal treatment pressure should be 0.30 MPa or higher, but from the viewpoint of further promoting the crystallization of the raw material composition, it is preferable to have a pressure of 0.35 MPa or higher, and more preferably 0.40 MPa or higher. Furthermore, although the pressurized hydrothermal treatment pressure should be 0.30 MPa or higher, from the viewpoint of making the average primary crystal diameter of the manufactured MFI type zeolite more likely to be the above value, it is preferable to have a pressure of 0.80 MPa or lower, and more preferably 0.60 MPa or lower. The combination of the upper and lower limits of the processing pressure for the pressurized hydrothermal treatment described above is arbitrary, but from the viewpoint of promoting crystal growth of the primary particles of the manufactured MFI-type zeolite and making it easier for the average primary crystal diameter to be the above value, it is preferable that it be between 0.30 MPa and 0.80 MPa, and more preferably between 0.30 MPa and 0.60 MPa. In this embodiment, the processing pressure values ​​in the pressurized hydrothermal treatment and the reduced-pressure hydrothermal treatment refer to absolute pressure values. Absolute pressure is the pressure expressed as the sum of atmospheric pressure and gauge pressure.

[0082] The processing pressure for pressurized hydrothermal treatment can be adjusted by the intrinsic pressure generated by the hydrothermal treatment of the raw material composition, provided that it is 0.30 MPa or higher. Alternatively, it can be adjusted by introducing or drawing in an atmospheric gas, or by compressing or expanding the volume of the sealed container filled with the raw material composition.

[0083] The processing time for pressurized hydrothermal treatment can be appropriately adjusted depending on the amount of raw material composition and the crystallization temperature, but examples include 5 hours or more or 10 hours or more, and 300 hours or less, 200 hours or less, 100 hours or less, or 50 hours or less. Specific examples of pressurized hydrothermal treatment times include 5 hours or more and 300 hours or 10 hours or more and 50 hours or less.

[0084] The pressurized hydrothermal treatment may be carried out with the raw material composition stirred or with the raw material composition left to stand, but from the viewpoint of further promoting the crystallization of the raw material composition, it is preferable to carry it out with stirring. The stirring speed can be appropriately adjusted depending on the scale and structure of the apparatus used for crystallization, but examples include 30 rpm to 500 rpm or 40 rpm to 400 rpm.

[0085] The pressurized hydrothermal treatment can be carried out by any means as long as it can be performed under treatment conditions of 100°C to 180°C and 0.30 MPa or higher. For example, a method can be used in which the raw material composition is filled into a sealed container and heated. The sealed container should be able to seal the raw material composition and have sufficient durability against the pressure generated during the hydrothermal treatment.

[0086] The raw material composition that has undergone pressurized hydrothermal treatment is then subjected to reduced-pressure hydrothermal treatment. By performing reduced-pressure hydrothermal treatment on the pressurized hydrothermal treatment raw material composition, it is possible to produce the MFI type zeolite of this embodiment, which has excellent catalytic activity as well as excellent durability and handling properties. On the other hand, if reduced-pressure hydrothermal treatment is not performed (only pressurized hydrothermal treatment is performed), the particle size variation of the produced MFI type zeolite becomes large, and the handling properties deteriorate. The reason why the MFI-type zeolite of this embodiment, which has excellent catalytic activity as well as superior durability and handling properties, can be produced by performing two treatments, pressurized hydrothermal treatment and reduced-pressure hydrothermal treatment, is not clear. However, it is thought that by pressurized hydrothermal treatment of the raw material composition having the above composition, a reaction proceeds in which MFI-type zeolite with an acid content of 0.50 mmol / g or more and an average primary crystal diameter of 0.1 μm to 5 μm crystallizes. Furthermore, by hydrothermal treatment while reducing the pressure at a depressurization rate of 0.03 MPa / hour or more, the raw material composition tumbles in the sealed container, suppressing aggregation of particles in the produced MFI-type zeolite and reducing variations in particle size. As a result, it is presumed that the MFI-type zeolite of this embodiment, which has excellent catalytic activity as well as superior durability and handling properties, can be produced.

[0087] The reduced-pressure hydrothermal treatment is performed at a temperature between 100°C and 160°C. By performing the reduced-pressure hydrothermal treatment at a temperature between 100°C and 160°C, the MFI-type zeolite of this embodiment can be manufactured. On the other hand, if the treatment temperature of the reduced-pressure hydrothermal treatment is outside the range of 100°C to 160°C, the variation in particle size of the manufactured MFI-type zeolite increases, and the handling properties decrease. The treatment temperature of the reduced-pressure hydrothermal treatment may be between 100°C and 160°C, but from the viewpoint of further suppressing the variation in particle size of the manufactured MFI-type zeolite, it is preferable to be 110°C or higher, and more preferably 120°C or higher. Furthermore, the treatment temperature of the reduced-pressure hydrothermal treatment may be between 100°C and 160°C, but from the viewpoint of further suppressing the variation in particle size of the manufactured MFI-type zeolite, it is preferable to be 150°C or lower, and more preferably 140°C or lower. The combination of the upper and lower limits of the treatment temperature for the aforementioned reduced-pressure hydrothermal treatment is arbitrary, but from the viewpoint of further suppressing variations in the particle size of the MFI-type zeolite produced, the treatment temperature for the reduced-pressure hydrothermal treatment is preferably 110°C to 160°C, more preferably 110°C to 150°C, and even more preferably 110°C to 140°C.

[0088] The reduced-pressure hydrothermal treatment is carried out while reducing the pressure at a rate of 0.03 MPa / hour or higher. By reducing the pressure at a rate of 0.03 MPa / hour or higher during the reduced-pressure hydrothermal treatment, the MFI type zeolite of this embodiment can be manufactured. On the other hand, if the reduction rate during the reduced-pressure hydrothermal treatment is less than 0.03 MPa / hour, the standard deviation of the manufactured MFI type zeolite tends to be larger than the above value, which may reduce its handling properties. The reduction rate in the reduced-pressure hydrothermal treatment should be 0.03 MPa / hour or higher, but from the viewpoint of further suppressing the variation in particle size of the manufactured MFI type zeolite, it is preferable to have a reduction rate of 0.05 MPa / hour or higher. Furthermore, the reduction rate in the reduced-pressure hydrothermal treatment should be 0.03 MPa / hour or higher, but from the viewpoint of making the average primary crystal diameter of the manufactured MFI type zeolite more likely to be the above value, it is preferable to have a reduction rate of 0.20 MPa / hour or lower, and more preferably 0.15 MPa / hour or lower. While the aforementioned combination of upper and lower limits for the depressurization rate is arbitrary, the depressurization rate in the reduced pressure hydrothermal treatment is preferably 0.03 MPa / hour or more and 0.20 MPa / hour or less, more preferably 0.05 MPa / hour or more and 0.20 MPa / hour or less, and even more preferably 0.05 MPa / hour or more and 0.15 MPa / hour or less, as this makes it easier for the standard deviation and average primary crystal diameter of the manufactured MFI-type zeolite to be closer to the above values, and further improves durability and handling.

[0089] The processing pressure in reduced-pressure hydrothermal treatment can be adjusted by allowing the atmospheric gas to be released naturally, by drawing in the atmospheric gas, or by expanding the volume of the sealed container filled with the raw material composition.

[0090] In vacuum hydrothermal treatment, the pressure at which vacuum reduction is initiated (hereinafter also referred to as the "pressure at the start of vacuum reduction") is preferably 0.15 MPa to 0.70 MPa, and more preferably 0.20 MPa to 0.50 MPa, from the viewpoint of further suppressing variations in the particle size of the MFI-type zeolite produced. The pressure at the start of vacuum reduction can be adjusted by heating or cooling the raw material composition (the raw material composition subjected to pressurized hydrothermal treatment) before the vacuum reduction is initiated.

[0091] In vacuum hydrothermal treatment, the pressure difference between the pressure at the start of vacuuming and the pressure at the end of vacuuming (hereinafter also referred to as the "pressure at the end of vacuuming") (the value obtained by subtracting the pressure at the end of vacuuming from the pressure at the start of vacuuming (hereinafter also referred to as the "pressure difference")) is preferably 0.01 MPa or more and 0.40 MPa or less, more preferably 0.02 MPa or more and 0.40 MPa or less, and even more preferably 0.02 MPa or more and 0.30 MPa or less, from the viewpoint of further suppressing variations in the particle size of the MFI type zeolite produced.

[0092] In vacuum hydrothermal treatment, the pressure at which the vacuum is terminated (hereinafter also referred to as the "pressure at the end of vacuum") is not particularly limited, but from the viewpoint of further suppressing variations in the particle size of the MFI-type zeolite produced, it is preferable that it be equal to or greater than the innate pressure.

[0093] The reduced-pressure hydrothermal treatment should be terminated when the treatment pressure is maintained at a state of less than ±5 kPa (0.005 MPa) of the indicated value (hereinafter also referred to as the "stable state") for 0.5 hours or more. For example, the indicated value in the reduced-pressure hydrothermal treatment can be the pressure at the end of the reduced pressure treatment, which is determined from the pressure difference between the pressure at the start of the reduced pressure treatment and the pressure at the end of the reduced pressure treatment. Furthermore, the stable state in the reduced-pressure hydrothermal treatment only needs to be 0.5 hours or longer, and an example is 0.5 hours to 10 hours.

[0094] Vacuum hydrothermal treatment may be started immediately after pressurized hydrothermal treatment is completed, or it may be started after a period of adjustment (hereinafter also referred to as the "condition adjustment period") in which the treatment temperature and treatment pressure are adjusted until the treatment temperature and pressure set for the vacuum hydrothermal treatment are reached. During the condition adjustment period, it is preferable to continue the hydrothermal treatment within a temperature range from the treatment temperature at the end of pressurized hydrothermal treatment to the treatment temperature set for vacuum hydrothermal treatment, and within a pressure range from the treatment pressure at the end of pressurized hydrothermal treatment to the pressure set for the start of vacuum hydrothermal treatment.

[0095] The total processing time for pressurized hydrothermal treatment and reduced-pressure hydrothermal treatment (hereinafter also referred to as "crystallization time") is 5 hours or more or 10 hours or more, and is 350 hours or less, 250 hours or less, 120 hours or less, or 70 hours or less. Specific examples of pressurized hydrothermal treatment processing times include 5 hours or more and 350 hours or less, or 10 hours or more and 70 hours or less.

[0096] In the crystallization process described above, the raw material composition is crystallized to obtain MFI-type zeolite as a crystalline product.

[0097] In the crystallization process, the crystalline product (MFI-type zeolite) obtained by crystallizing the raw material composition may be subjected to at least one of the following treatments: washing and drying.

[0098] The washing process involves washing the crystalline product obtained by crystallizing the raw material composition. While the washing method is arbitrary, one example is contacting the crystalline product with a sufficient amount of pure water. The crystalline product obtained by crystallizing the raw material composition may also be subjected to solid-liquid separation before the washing process, if necessary.

[0099] The drying process is a process to remove moisture physically adsorbed on the crystalline product obtained by crystallizing the raw material composition, or on the crystalline product after washing. The drying method is arbitrary, but examples include drying the crystalline product in the air at a temperature of 50°C to 250°C for 1 to 120 hours, either by standing or by using a spray dryer.

[0100] The method for producing MFI-type zeolite according to this embodiment includes a post-treatment step in addition to the crystallization step described above. The post-treatment step is a process of calcination and acid treatment applied to the crystalline product (MFI-type zeolite) obtained in the crystallization step.

[0101] The calcination process in the post-processing stage is a process of calcining the crystallized material. By performing a calcination process on the crystallized material, the SDA contained in the crystallized material can be removed.

[0102] In the post-processing step, the firing conditions are not particularly limited, and should be adjusted as appropriate so that the SDA content is 1.0% by mass or less. However, the following conditions are preferable as they make it easier to remove SDA. The atmosphere in which the firing is performed is preferably an atmospheric atmosphere. The firing temperature is preferably 400°C or higher, 500°C or higher, or 600°C or higher, and preferably 800°C or lower, 750°C or lower, or 700°C or lower. The combination of the upper and lower limits of the firing temperature mentioned above is arbitrary, but it is preferably 400°C or higher and 800°C or lower, more preferably 500°C or higher and 750°C or lower, and even more preferably 500°C or higher and 700°C or lower. The firing time is preferably 0.5 hours or more, 1 hour or more, or 3 hours or more, and preferably 24 hours or less, 12 hours or less, or 6 hours or less. The combination of the upper and lower limits of the firing time is arbitrary, but it is preferably 0.5 hours or more and 24 hours or less, more preferably 0.5 hours or more and 12 hours or less, and even more preferably 1 hour or more and 6 hours or less.

[0103] Acid treatment in the post-processing stage involves contacting the crystallized material with an acid. By treating the crystallized material with acid, alkali metals contained within the crystallized material can be removed.

[0104] The acid brought into contact with the crystallized material may be either an organic acid or an inorganic acid, but it is preferable to use an inorganic acid because alkali metals are more easily removed, more preferably one or more acids selected from the group consisting of hydrochloric acid, nitric acid, and sulfuric acid, and even more preferably hydrochloric acid. When hydrochloric acid is used as the acid brought into contact with the crystallized material, the concentration of the hydrochloric acid can be adjusted as appropriate so that the alkali metal content is 0.05% by mass or less, and is not particularly limited, but is preferably 5% by mass or more and 20% by mass or less, and more preferably 7% by mass or more and 15% by mass or less.

[0105] In the post-treatment process, the conditions for acid treatment are not particularly limited, but they can be adjusted as appropriate so that the alkali metal content is 0.05% by mass or less. However, the following conditions are preferable as they facilitate the removal of alkali metals. The contact temperature between the crystallized material and the acid is preferably 20°C or higher, 40°C or higher, or 60°C or higher, and preferably 90°C or lower, 80°C or lower, or 70°C or lower. The combination of the upper and lower limits of the contact temperature between the crystallized material and the acid is arbitrary, but preferably 20°C or higher and 90°C or lower, more preferably 20°C or higher and 80°C or lower, and even more preferably 20°C or higher and 70°C or lower. The contact time between the crystallized material and the acid is preferably 0.5 minutes or more, 1 minute or more, or 5 minutes or more, and preferably 30 minutes or less, 20 minutes or less, or 10 minutes or less. The combination of the upper and lower limits for the contact time between the crystallized product and the acid is arbitrary, but it is preferably 0.5 minutes or more and 30 minutes or less, more preferably 0.5 minutes or more and 20 minutes or less, and even more preferably 1 minute or more and 10 minutes or less.

[0106] In the post-processing step, the order of calcination and acid treatment is arbitrary. The crystallized product obtained in the crystallization step may be calcined first, followed by acid treatment on the calcined crystallized product, or the crystallized product obtained in the crystallization step may be acid treated first, followed by calcination on the acid-treated crystallized product. From the viewpoint of making it easier to remove SDA and alkali metals contained in the crystallized product, it is preferable that in the post-processing step, the crystallized product obtained in the crystallization step is calcined first, followed by acid treatment on the calcined crystallized product.

[0107] In the post-processing step, the crystallized material is subjected to calcination and acid treatment to remove SDA and alkali metals contained in the crystallized material, thereby obtaining the MFI-type zeolite of this embodiment. On the other hand, if the post-processing step is not performed, the SDA content of the obtained MFI-type zeolite will exceed 1.0 mass or the alkali metal content will exceed 0.05 mass%, making it impossible to manufacture the MFI-type zeolite of this embodiment. Furthermore, if only calcination is performed in the post-processing step (no acid treatment is performed), the alkali metal content of the obtained MFI-type zeolite will exceed 0.05 mass%, making it impossible to manufacture the MFI-type zeolite of this embodiment. Furthermore, if only acid treatment is performed in the post-processing step (no calcination is performed), the SDA content of the obtained MFI-type zeolite will exceed 1.0 mass, making it impossible to manufacture the MFI-type zeolite of this embodiment.

[0108] The MFI-type zeolite obtained in the post-processing step (the MFI-type zeolite of this embodiment) may be used as is for the intended purpose, or it may be used after undergoing at least one of the washing and drying processes. The washing and drying processes that can be performed on the MFI-type zeolite obtained in the post-processing step are the same as the washing and drying processes that can be performed in the crystallization step described above, so a detailed explanation is omitted. [Examples]

[0109] The present disclosure will be explained below with reference to examples. However, the present disclosure is not limited to these examples.

[0110] (Identification of crystalline phases) An XRD pattern was obtained using a powder X-ray diffractometer (instrument name: Ultima IV, manufactured by Rigaku Corporation) under the following conditions. Acceleration current / voltage: 40mA / 40kV Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Continuous scan Scanning conditions: 10° / min Measurement range: 2θ = 5° to 40° Divergence vertical limiting slit: 10mm Divergence / Induction Slit: 1° Scattering slit: Open Light-receiving slit: Open Detector: Semiconductor detector (D / teX Ultra2) Filter: Not used

[0111] The crystalline phase of the sample was identified by comparing the obtained XRD pattern with a reference pattern.

[0112] (Standard deviation of volume particle size distribution) The volume particle size distribution was determined by measuring the frequency curve and integration curve of the volume particle size distribution using a laser diffraction / scattering particle size distribution analyzer (instrument name: Microtrac MT3300EXII, manufactured by Microtrac-Bell Co., Ltd.). As a pretreatment, the sample was suspended in pure water and dispersed for 2 minutes using an ultrasonic homogenizer set to a frequency of 20 kHz. The measurement conditions were as follows. Measurement range: 0.02~2000μm Particle refractive index: 1.66 Particle permeability: permeation Particle shape: non-spherical Solvent type: Water (pure water) Solvent refractive index: 1.333 Ultrasonic pretreatment: Frequency 20kHz, 2 minutes

[0113] From the obtained cumulative volume particle size distribution, D10, D50, and D90 were obtained. Using the obtained values ​​of D10 and D90, the standard deviation of the volume particle size distribution was calculated from equation (1) above.

[0114] (Average primary crystal diameter and aspect ratio) SEM observations were performed using a standard scanning electron microscope (device name: JSM-IT200, manufactured by JEOL Ltd.) under the following conditions. Acceleration voltage: 6kV Magnification: 10,000±5,000x

[0115] The average primary crystal diameter was determined by first extracting 100 ± 10 primary particles whose contours were observed without interruption in the SEM observation image. Then, the distance between the two parallel lines tangent to the contour of each extracted primary particle was measured, and the average value of these distances was calculated and defined as the average primary crystal diameter. Note that under the aforementioned SEM observation conditions, measurement errors may occur for primary crystal diameters less than 100 nm; therefore, particles with an average primary crystal diameter less than 100 nm were uniformly indicated as less than 100 nm.

[0116] The aspect ratio of the primary particles was determined from equation (2) above. Specifically, 100 ± 10 primary particles were extracted in the same manner as for the average primary crystal diameter, and the distance between the longest parallel lines when the contour was enclosed by two parallel lines tangent to it was measured. The average longest diameter L1 [μm] in equation (2) was obtained by averaging these distances. Similarly, the distance between the shortest parallel lines when the contours of the extracted 100 ± 10 primary particles were enclosed by two parallel lines tangent to them was measured, and the average shortest diameter L2 [μm] in equation (2) was obtained by averaging these distances. Using the obtained average longest diameter L1 [μm] and average shortest diameter L2 [μm], the aspect ratio of the primary particles was determined from equation (2) above.

[0117] (composition analysis) For compositional analysis, a sample solution was prepared by dissolving the sample in a mixed aqueous solution of hydrofluoric acid and nitric acid. The sample solution was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES) using a general ICP instrument (instrument name: OPTIMA5300DV, PerkinElmer). From the obtained Si and Al measurements, the SiO2 / Al2O3 ratio of the sample was determined. Furthermore, using the obtained Si, Al, and Na measurements, the Na content (alkali metal content) of the sample was determined from the above formula (6).

[0118] (BET specific surface area) The BET specific surface area of ​​the sample was determined by measurement in accordance with JIS Z 8830:2013. A general specific surface area measuring device (device name: BELSORP-miniII, manufactured by Microtrac-Bel Co., Ltd.) was used for the measurement. As a pretreatment, the sample was held in a vacuum atmosphere (10 Pa or less) at 350°C for 2 hours. For the pretreated sample, nitrogen was used as the adsorption gas and the BET specific surface area was measured using the single-point method.

[0119] (Measurement of acid content) The acid content of the sample was measured using the ammonia-TPD method with a general catalyst analyzer (instrument name: BELCATII, manufactured by Microtrac-Bel Co., Ltd.). Specifically, first, 0.05 g of zeolite sample was pretreated by standing under a helium gas flow at 500°C for 1 hour, and this was used as the measurement sample. After pretreatment, a mixed gas containing 10 vol% ammonia and 90 vol% helium was passed through the measurement sample at room temperature (25°C) for 1 hour to saturate the sample with ammonia adsorption. The mixed gas was changed to helium gas, and the measurement sample was heated to 100°C while the helium gas flowed through it. After heating, the ammonia remaining in the atmosphere (ammonia not adsorbed on the zeolite) was removed by passing helium gas through it at 100°C for 1 hour.

[0120] After removing residual ammonia, the sample was heated from 100°C to 600°C at a heating rate of 10°C / min under a helium flow rate of 50 mL / min. The amount of released ammonia measured during this heating process was measured using a TCD detector built into the catalyst analyzer. Assuming that the measured amount of released ammonia represents the amount of acid sites present in the zeolite (amount of ammonia adsorbed on the acid sites of the zeolite), the acid content per unit mass of the sample [mmol / g] was determined from the mass [g] of the sample and the amount of acid sites present in the zeolite (measured amount of released ammonia).

[0121] (SDA content) The SDA content was determined by dividing the mass of SDA contained in the sample by the mass of the sample and converting this to a percentage. The mass of the sample used was the dry mass of MFI-type zeolite (sample) dried in an air atmosphere at 110°C for 4 hours. The mass of SDA contained in the sample was the change in mass when the sample was heated from 300°C to 700°C. The change in mass of the sample was measured using a general differential thermogravimetric analyzer (STA 2500 Regulus, NETZSCH) under the following conditions. Atmosphere: air Atmospheric flow rate: 20cc / min Heating rate: 10°C / min Measurement temperature: 20~800℃

[0122] (viscosity measurement) Shear rate 100s -1 The viscosity was measured using a general-purpose viscometer (device name: MCR 92, manufactured by Anton Paar). The sample was mixed with pure water to prepare a slurry (sample slurry) with a solid content concentration of 40% by mass. 2 mL of the sample slurry was dropped onto the stage of the measuring apparatus fitted with a parallel plate measuring jig (PP50), and the shear rate was set to 100 s. -1 The viscosity [mPa·s] was measured. During the measurement, the stage temperature was 20°C, and the gap between the measuring fixture and the stage was 0.2 mm. The solid content concentration of the slurry was determined from the above formula (5). In the above formula (5), the slurry mass [g] was the value obtained by measuring the mass of the slurry, and the zeolite mass [g] was the value obtained by measuring the mass of the zeolite after drying the slurry after measuring the slurry mass and treating it in air at 600°C for 1 hour.

[0123] (Durability Test 1; Water Heat Durability Test) The sample was placed on an alumina boat and set up in a box-type muffle furnace (product name: FUW253PA, manufactured by ADVANTEC). 150°C steam at a flow rate of 15 L / min and room temperature (25°C) air at a flow rate of 15 L / min were introduced, and the sample was exposed to an atmosphere containing 50% by volume of steam and 50% by volume of air at 1050°C for 3 hours to perform a hydrothermal endurance treatment.

[0124] Using the same method as for identifying the crystalline phase described above, XRD patterns were obtained for the sample before and after hydrothermal treatment. The integrated intensity of XRD peaks in the obtained XRD patterns with diffraction angles 2θ in the range of 22° to 25° was determined, and the crystallinity before hydrothermal treatment (I0) and after hydrothermal treatment (I1) were obtained using equation (3) above. Using the obtained crystallinity before hydrothermal treatment (I0) and crystallinity after hydrothermal treatment (I1), the crystallinity retention rate [%] of the zeolite was calculated from equation (3) above.

[0125] The integrated intensity of the XRD peak was determined by calculating the integrated intensity during the analysis of the XRD pattern using analysis software (product name: Integral Analysis for Windows Version 6.2, manufactured by Rigaku Corporation). The analysis conditions for the XRD pattern are shown below. Background removal method: Sonneveld-visser method Peak width threshold: 0.10 Intensity threshold: 1.00 Peak calculation method: Peak top method

[0126] (Durability Test 2; Water Vapor Adsorption Test) The amount of water vapor adsorbed was determined using a general-purpose vapor adsorption measuring device (device name: BELSORP-MAXII, manufactured by Microtrac-Bel Co., Ltd.) by the following method. As a pretreatment, 11 cm 3 A sample tube was filled with 20 mg of MFI-type zeolite and held in a vacuum atmosphere (10 Pa or less) at 350°C for 2 hours to prepare the sample for measurement. The sample tube filled with the sample for measurement was set in a vapor adsorption amount measuring device, and the mass of the sample for measurement was measured, which was taken as W0 (mass of MFI-type zeolite before water vapor adsorption treatment [g]) in the above formula (4).

[0127] The sample tube set in the vapor adsorption amount measuring device is 10 -5After reducing the pressure to below Pa, the temperature and relative humidity were varied from 0% to 90% and the sample was exposed to an atmosphere of 25°C and 90% relative humidity for water vapor adsorption treatment (90% water vapor treatment) until the amount of water vapor adsorbed by the sample reached equilibrium (until the pressure change was maintained within ±0.3% for 300 seconds). After the amount of water vapor adsorbed by the sample reached equilibrium, the amount of water adsorbed by the sample was measured by the constant volume method and this was defined as W1 (amount of water adsorbed on MFI type zeolite by water vapor adsorption treatment [g]) in equation (4) above. Using the measured W1 and W0, the amount of water vapor adsorbed at 25°C and 90% relative humidity (90% water vapor adsorption amount) was determined from equation (4) above.

[0128] Furthermore, the sample tube set in the vapor adsorption amount measuring device is 10 -5 After reducing the pressure to below Pa, the temperature and relative humidity were varied from 0% to 60%. The sample was exposed to an atmosphere of 25°C and 60% relative humidity for water vapor adsorption treatment (60% water vapor treatment) until the amount of water vapor adsorbed by the sample reached equilibrium (until the pressure change was maintained within ±0.3% for 300 seconds). After the amount of water vapor adsorbed by the sample reached equilibrium, the amount of water adsorbed by the sample was measured by the constant volume method and was defined as W1 (amount of water adsorbed on MFI type zeolite by water vapor adsorption treatment [g]) in equation (4) above. Using the measured W1 and W0, the amount of water vapor adsorbed at 25°C and 60% relative humidity (60% water vapor adsorption amount) was determined from equation (4) above.

[0129] (Evaluation of catalytic activity) The catalytic activity of MFI-type zeolite was evaluated using the decomposition reaction of low-density polyethylene (hereinafter also referred to as "LDPE"). First, LDPE powder (product name: UBEC180, manufactured by Ube Maruzen Polyethylene Co., Ltd.) was classified to 13 μm or less to be used as the LDPE raw material. MFI-type zeolite was mixed with 100% by mass of the LDPE raw material to 25% by mass (i.e., LDPE raw material:MFI-type zeolite = 80% by mass:20% by mass) to prepare the measurement sample. The decomposition reaction of LDPE was evaluated by thermogravimetric analysis using a general differential thermogravimetric analyzer (STA 2500 Regulus, manufactured by NETZSCH) after purging with nitrogen at 20 cc / min for 1 hour. The decomposition start temperature was defined as the temperature at which the mass of the measurement sample became 99.5% or less of the mass of the measurement sample at a measurement temperature of 100°C. Furthermore, the decomposition completion temperature was defined as the temperature at which the mass change of the sample for each 1°C interval was 0.1% or less relative to the mass of the sample at 100°C. The measurement conditions were as follows. Atmosphere: Nitrogen Atmospheric flow rate: 20cc / min Heating rate: 5°C / min Measurement temperature: 20~600℃ Mass measurement: every 1°C

[0130] Example 1 NBA, pure water, sodium hydroxide, and amorphous aluminosilicate were mixed to obtain a raw material composition having the following molar composition. SiO2 / Al2O3 ratio =83 Na / SiO2 ratio =0.20 NBA / SiO2 ratio =0.10 H2O / SiO2 ratio =11 OH / SiO2 ratio =0.20

[0131] After mixing seed crystals (MFI-type zeolite, SiO2 / Al2O3 ratio: 2500, manufactured by Tosoh Corporation) with the raw material composition so that the seed crystal content was 1.0% by mass, 3600g of the raw material composition was filled into a 4L sealed container and subjected to hydrothermal treatment (pressurized hydrothermal treatment) at a pressure of 0.59MPa and 150°C for 30 hours while stirring at 350rpm. After the pressurized hydrothermal treatment was completed, the treatment temperature was reduced from 150°C to 130°C while continuing the hydrothermal treatment. When the treatment temperature reached 130°C and the treatment pressure reached 0.40MPa, depressurization was started by releasing the atmospheric gas from the sealed container, and the hydrothermal treatment pressure was reduced to 0.26MPa at a depressurization rate of 0.14MPa / hour while performing hydrothermal treatment (reduced pressure hydrothermal treatment) at 130°C. Hydrothermal treatment (reduced pressure hydrothermal treatment) was continued at 0.26 MPa and 130°C for 1.5 hours after the hydrothermal treatment pressure reached 0.26 MPa, to obtain a crystallized slurry.

[0132] The crystallized slurry was subjected to solid-liquid separation and washed with pure water, then dried in an air atmosphere at 110°C to obtain crystals. The crystals were calcined in an air atmosphere at 600°C for 2 hours, then contacted with 7% by mass hydrochloric acid at 25°C for 5 minutes, washed with pure water, and subjected to solid-liquid separation to obtain the MFI type zeolite of this example.

[0133] The MFI-type zeolite in this embodiment is an MFI-type crystalline aluminosilicate consisting of a single phase with an MFI structure, with an SiO2 / Al2O3 ratio of 66, an average primary crystal diameter of 0.73 μm, an aspect ratio of 1.23, an SDA content of 0.32 mass%, a Na content (alkali metal content) of less than 0.01 mass%, and a BET specific surface area of ​​342 m². 2 The volume particle size distribution was 0.94 μm for D10, 2.9 μm for D50, and 6.7 μm for D90, with a standard deviation of 2.9 μm for volume particle size distribution and an acid content of 0.73 mmol / g.

[0134] Example 2 NBA, pure water, sodium hydroxide, and amorphous aluminosilicate were mixed to obtain a raw material composition having the following molar composition. SiO2 / Al2O3 ratio =84 Na / SiO2 ratio =0.10 NBA / SiO2 ratio =0.10 H2O / SiO2 ratio =11 OH / SiO2 ratio =0.10

[0135] After mixing seed crystals (MFI-type zeolite, SiO2 / Al2O3 ratio: 2500, manufactured by Tosoh Corporation) with the raw material composition so that the seed crystal content was 1.0% by mass, 3600g of the raw material composition was filled into a 4L sealed container and subjected to hydrothermal treatment (pressurized hydrothermal treatment) at a pressure of 0.49MPa and 150°C for 36 hours while stirring at 350rpm. After the pressurized hydrothermal treatment was completed, the treatment temperature was reduced from 150°C to 130°C while continuing the hydrothermal treatment. When the treatment temperature reached 130°C and the treatment pressure reached 0.29MPa, depressurization was started by releasing the atmospheric gas from the sealed container, and the hydrothermal treatment pressure was reduced to 0.26MPa at a depressurization rate of 0.06MPa / hour while performing hydrothermal treatment (reduced pressure hydrothermal treatment) at 130°C. Hydrothermal treatment (reduced pressure hydrothermal treatment) was continued at 0.26 MPa and 130°C for 1.5 hours after the hydrothermal treatment pressure reached 0.26 MPa to obtain a crystallized slurry. The obtained crystallized slurry was separated into solid and liquid components, washed with pure water, and then dried in an air atmosphere at 110°C to obtain crystallized material. The crystallized material had an SDA content of 5.3 mass% and a Na content (alkali metal content) of 0.11 mass%. The obtained crystallized material was subjected to the same treatment as the crystallized material of Example 1 to obtain the MFI type zeolite of this example.

[0136] The MFI-type zeolite in this embodiment is an MFI-type crystalline aluminosilicate consisting of a single phase with an MFI structure, with an SiO2 / Al2O3 ratio of 86, an average primary crystal diameter of 0.95 μm, an aspect ratio of 1.77, an SDA content of 0.31 mass%, a Na content (alkali metal content) of less than 0.01 mass%, and a BET specific surface area of ​​353 m². 2 The particle size distribution was 2.7 μm for D10, 5.9 μm for D50, and 19 μm for D90, with a standard deviation of 8.2 μm for volume particle size distribution and an acid content of 0.63 mmol / g.

[0137] Comparative Example 1 NBA, pure water, sodium hydroxide, and amorphous aluminosilicate were mixed to obtain a raw material composition having the following molar composition. SiO2 / Al2O3 ratio =49 Na / SiO2 ratio =0.10 NBA / SiO2 ratio =0.10 H2O / SiO2 ratio =11 OH / SiO2 ratio =0.10

[0138] Seed crystals (MFI-type zeolite, SiO2 / Al2O3 ratio: 2500, manufactured by Tosoh Corporation) were mixed with the raw material composition so that the seed crystal content was 1.0% by mass. Then, 3600 g of the raw material composition was filled into a 4 L sealed container and hydrothermally treated at a pressure of 0.49 MPa and 150 °C for 24 hours while stirring at 350 rpm to obtain a crystallized slurry. The obtained crystallized slurry was subjected to the same treatment as the crystallized slurry of Example 1 to obtain the MFI-type zeolite of this comparative example.

[0139] The MFI-type zeolite in this comparative example is an MFI-type crystalline aluminosilicate consisting of a single phase with an MFI structure, with an SiO2 / Al2O3 ratio of 52, an average primary crystal diameter of 0.57 μm, an aspect ratio of 1.71, an SDA content of 0.32 mass%, a Na content (alkali metal content) of less than 0.01 mass%, and a BET specific surface area of ​​368 m². 2 The volume particle size distribution was 3.4 μm for D10, 72 μm for D50, and 120 μm for D90, with a standard deviation of 58 μm for volume particle size distribution and an acid content of 0.80 mmol / g.

[0140] Comparative Example 2 The MFI-type zeolite of this comparative example was obtained in the same manner as in Example 2, except that vacuum hydrothermal treatment was not performed. That is, the raw material composition was subjected to pressurized hydrothermal treatment in the same manner as in Example 2, and the crystallized slurry obtained by pressurized hydrothermal treatment was subjected to the same treatment as the crystallized slurry of Example 2 to obtain the MFI-type zeolite of this comparative example.

[0141] The MFI-type zeolite in this comparative example is an MFI-type crystalline aluminosilicate consisting of a single phase with an MFI structure, with an SiO2 / Al2O3 ratio of 86, an average primary crystal diameter of 0.95 μm, an aspect ratio of 1.77, an SDA content of 0.31 mass%, a Na content (alkali metal content) of less than 0.01 mass%, and a BET specific surface area of ​​353 m². 2 The volume particle size distribution was 3.1 μm for D10, 18 μm for D50, and 48 μm for D90, with a standard deviation of 22 μm for volume particle size distribution and an acid content of 0.63 mmol / g.

[0142] Comparative Example 3 NBA, pure water, sodium hydroxide, and amorphous aluminosilicate were mixed to obtain a raw material composition having the following molar composition. SiO2 / Al2O3 ratio =26 Na / SiO2 ratio =0.20 NBA / SiO2 ratio =0.23 H2O / SiO2 ratio =11 OH / SiO2 ratio =0.20

[0143] Seed crystals (MFI-type zeolite, SiO2 / Al2O3 ratio: 2500, manufactured by Tosoh Corporation) were mixed with the raw material composition so that the seed crystal content was 1.0% by mass. Then, 3600g of the raw material composition was filled into a 4L sealed container and subjected to hydrothermal treatment (pressurized hydrothermal treatment) at a pressure of 0.65MPa and 150°C for 36 hours while stirring at 350rpm to crystallize the raw material composition. After the pressurized hydrothermal treatment was completed, the treatment temperature was lowered from 150°C to 130°C while continuing the hydrothermal treatment. When the treatment temperature reached 130°C and the treatment pressure reached 0.41MPa, depressurization was started by releasing the atmospheric gas from the sealed container, and the hydrothermal treatment pressure was reduced to 0.27MPa at a depressurization rate of 0.14MPa / hour while hydrothermal treatment (reduced pressure hydrothermal treatment) was performed at 130°C. Hydrothermal treatment (reduced pressure hydrothermal treatment) was continued at 0.27 MPa and 130°C for 1.5 hours after the hydrothermal treatment pressure reached 0.27 MPa to obtain a crystallized slurry. The obtained crystallized slurry was subjected to the same treatment as that applied to the crystallized slurry of Example 1 to obtain the MFI type zeolite of this comparative example.

[0144] The MFI-type zeolite in this comparative example is an MFI-type crystalline aluminosilicate consisting of a single phase with an MFI structure, with an SiO2 / Al2O3 ratio of 23, an average primary crystal diameter of less than 100 nm, an SDA content of 0.66 mass%, a Na content (alkali metal content) of less than 0.01 mass%, and a BET specific surface area of ​​343 m². 2 The volume particle size distribution was 4.6 μm for D10, 13 μm for D50, and 72 μm for D90, with a standard deviation of 34 μm and an acid content of 1.61 mmol / g.

[0145] Comparative Example 4 NBA, pure water, sodium hydroxide, and amorphous aluminosilicate were mixed to obtain a raw material composition having the following molar composition. SiO2 / Al2O3 ratio =216 Na / SiO2 ratio =0.11 NBA / SiO2 ratio =0.23 H2O / SiO2 ratio =11 OH / SiO2 ratio =0.11

[0146] Seed crystals (MFI-type zeolite, SiO2 / Al2O3 ratio: 2500, manufactured by Tosoh Corporation) were mixed with the raw material composition so that the seed crystal content was 1.0% by mass. Then, 3600g of the raw material composition was filled into a 4L sealed container and subjected to hydrothermal treatment (pressurized hydrothermal treatment) at a pressure of 0.41MPa and 130°C for 36 hours while stirring at 350rpm to crystallize the raw material composition. Immediately after the completion of the pressurized hydrothermal treatment, depressurization was started by releasing the atmospheric gas from the sealed container, and hydrothermal treatment (reduced pressure hydrothermal treatment) was performed at 130°C while reducing the hydrothermal treatment pressure to 0.27MPa at a depressurization rate of 0.14MPa / hour. Hydrothermal treatment (reduced pressure hydrothermal treatment) was continued at 0.27MPa and 130°C for 1.5 hours after the hydrothermal treatment pressure reached 0.27MPa to obtain a crystallized slurry. The obtained crystallized slurry was subjected to the same treatment as that applied to the crystallized slurry of Example 1 to obtain the MFI-type zeolite of this comparative example.

[0147] The MFI-type zeolite in this comparative example is an MFI-type crystalline aluminosilicate consisting of a single phase with an MFI structure, with an SiO2 / Al2O3 ratio of 195, an average primary crystal diameter of 1.16 μm, an aspect ratio of 1.87, an SDA content of 0.41 mass%, a Na content (alkali metal content) of less than 0.01 mass%, and a BET specific surface area of ​​341 m². 2 The particle size distribution was 1.4 μm for D10, 2.7 μm for D50, and 7.1 μm for D90, with a standard deviation of 2.9 μm for volume particle size distribution and an acid content of 0.25 mmol / g.

[0148] Comparative Example 5 A 50% by mass aqueous solution of tetrapropylammonium bromide (TPABr), pure water, sodium hydroxide, and amorphous aluminosilicate were mixed to obtain a raw material composition having the following molar composition. In the following composition, TPA represents the tetrapropylammonium cation. SiO2 / Al2O3 ratio =83 Na / SiO2 ratio =0.20 TPA / SiO2 ratio =0.10 H2O / SiO2 ratio =11 OH / SiO2 ratio =0.20

[0149] Seed crystals (MFI-type zeolite, SiO2 / Al2O3 ratio: 2500, manufactured by Tosoh Corporation) were mixed with the raw material composition so that the seed crystal content was 1.0% by mass. Then, 55 g of the raw material composition was filled into a sealed container with a volume of 0.08 L, and hydrothermally treated at 55 rpm with self-stimulation pressure and 150°C for 30 hours to obtain a crystallized slurry. The obtained crystallized slurry was subjected to the same treatment as the crystallized slurry of Example 1 to obtain the MFI-type zeolite of this comparative example.

[0150] The MFI-type zeolite in this comparative example is an MFI-type crystalline aluminosilicate consisting of a single phase with an MFI structure, with an SiO2 / Al2O3 ratio of 85, an average primary crystal diameter of less than 100 nm, an SDA content of 0.76 mass%, a Na content (alkali metal content) of less than 0.01 mass%, and a BET specific surface area of ​​389 m². 2The particle size distribution was 2.3 μm for D10, 4.9 μm for D50, and 25 μm for D90, with a standard deviation of 11 μm for volume particle size distribution and an acid content of 0.65 mmol / g.

[0151] Comparative Example 6 A 50% by mass aqueous solution of TPABr, pure water, sodium hydroxide, sodium aluminate, and colloidal silica (product name: ST-30, manufactured by Nissan Chemical Corporation) were mixed to obtain a raw material composition having the following molar composition. SiO2 / Al2O3 ratio =100 Na / SiO2 ratio =0.18 TPA / SiO2 ratio =0.10 H2O / SiO2 ratio =15 OH / SiO2 ratio =0.18

[0152] 60 g of the raw material composition was filled into a sealed container with a volume of 0.08 L, and hydrothermally treated at 160°C for 36 hours under self-stimulation pressure while stirring at 55 rpm to obtain a crystallized slurry. The obtained crystallized slurry was subjected to the same treatment as that applied to the crystallized slurry of Example 1 to obtain the MFI type zeolite of this comparative example.

[0153] The MFI-type zeolite in this comparative example is an MFI-type crystalline aluminosilicate consisting of a single phase with an MFI structure, with an SiO2 / Al2O3 ratio of 88, an average primary crystal diameter of less than 100 nm, an SDA content of 0.60 mass%, a Na content (alkali metal content) of less than 0.01 mass%, and a BET specific surface area of ​​386 m². 2 The volume particle size distribution was 0.63 mmol / g, D10 was 0.60 μm, D50 was 1.1 μm, and D90 was 180 μm. The standard deviation of the volume particle size distribution was 90 μm, and the acid content was 0.63 mmol / g.

[0154] Comparative Example 7 NBA, pure water, sodium hydroxide, and amorphous aluminosilicate were mixed to obtain a raw material composition having the following molar composition. SiO2 / Al2O3 ratio =4100 Na / SiO2 ratio =0.11 NBA / SiO2 ratio =0.23 H2O / SiO2 ratio =11 OH / SiO2 ratio =0.11

[0155] Seed crystals (MFI type zeolite, SiO2 / Al2O3 ratio: 2500, manufactured by Tosoh Corporation) were mixed to achieve a seed crystal content of 1.0 mass%. 3600g of this raw material composition was then packed into a 4L sealed container and subjected to hydrothermal treatment (pressurized hydrothermal treatment) at a pressure of 0.41 MPa and 120°C for 24 hours while stirring at 350 rpm to crystallize the raw material composition. Immediately after the completion of the pressurized hydrothermal treatment, depressurization was initiated by releasing the atmospheric gas from the sealed container, and the hydrothermal treatment pressure was reduced to 0.20 MPa at a depressurization rate of 0.21 MPa / hour while hydrothermal treatment (reduced-pressure hydrothermal treatment) was performed at 120°C. Hydrothermal treatment at 0.20 MPa and 120°C (reduced-pressure hydrothermal treatment) was continued for 1.5 hours after the hydrothermal treatment pressure reached 0.20 MPa to obtain a crystallized slurry. The obtained crystallized slurry was subjected to the same treatment as that applied to the crystallized slurry of Example 1 to obtain the MFI-type zeolite of this comparative example.

[0156] The MFI-type zeolite in this comparative example is an MFI-type crystalline aluminosilicate consisting of a single phase with an MFI-type structure, with an SiO2 / Al2O3 ratio of 2520, an average primary crystal diameter of 1.25 μm, an aspect ratio of 2.11, an SDA content of 1.4 mass%, a Na content (alkali metal content) of less than 0.01 mass%, and a BET specific surface area of ​​338 m². 2 The particle size distribution was 1.4 μm for D10, 2.6 μm for D50, and 4.8 μm for D90, with a standard deviation of 1.7 μm for volume particle size distribution and an acid content of 0.06 mmol / g.

[0157] Comparative Example 8 Crystallized material was obtained in the same manner as in Example 2. The obtained crystallized material was not calcined, but was contacted with 7% by mass hydrochloric acid at 25°C for 5 minutes, washed with pure water, and then subjected to solid-liquid separation to obtain the MFI-type zeolite of this comparative example.

[0158] The MFI-type zeolite in this comparative example is an MFI-type crystalline aluminosilicate consisting of a single phase with an MFI-type structure, with an SiO2 / Al2O3 ratio of 86, an average primary crystal diameter of 0.95 μm, an aspect ratio of 1.77, an SDA content of 3.9% by mass, a Na content (alkali metal content) of less than 0.01% by mass, and a BET specific surface area of ​​353 m². 2 The volume particle size distribution was 2.7 μm for D10, 5.9 μm for D50, and 19 μm for D90, with a standard deviation of 8.2 μm and an acid content of 0.68 mmol / g.

[0159] Comparative Example 9 Crystallized material was obtained in the same manner as in Example 2. The obtained crystallized material was dried in an air atmosphere at 110°C to obtain further crystallized material. The crystallized material was calcined in an air atmosphere at 600°C for 2 hours without contact with hydrochloric acid to obtain the MFI type zeolite of this comparative example.

[0160] The MFI-type zeolite in this comparative example is an MFI-type crystalline aluminosilicate consisting of a single phase with an MFI-type structure, with an SiO2 / Al2O3 ratio of 86, an average primary crystal diameter of 0.95 μm, an aspect ratio of 1.77, an SDA content of 0.60 mass%, a Na content (alkali metal content) of 0.07 mass%, and a BET specific surface area of ​​353 m². 2 The particle size distribution was 2.7 μm for D10, 5.9 μm for D50, and 19 μm for D90, with a standard deviation of 8.2 μm for volume particle size distribution and an acid content of 0.63 mmol / g.

[0161] Table 1 below shows the SiO2 / Al2O3 ratio, acid content, standard deviation of volume particle size distribution, and average primary crystal diameter for the MFI-type zeolites of the examples and comparative examples. [Table 1]

[0162] Measurement Example 1 (Durability Tests 1 and 2) Durability tests 1 and 2 described above were performed on the MFI-type zeolites of the examples and comparative examples. The results are shown in Table 2 below. [Table 2]

[0163] Measurement Example 2 (Viscosity Measurement) The MFI-type zeolite (measurement sample) of the examples and comparative examples was mixed with pure water to prepare a 40% by mass solid content slurry (sample slurry), and the following measurements were taken using the method described above at a shear rate of 100 s. -1 The viscosity was measured. The results are shown in Table 3 below. [Table 3]

[0164] Measurement Example 3 (Evaluation of Catalytic Activity) The catalytic activity of the MFI-type zeolites in the examples and comparative examples was evaluated using the method described above. For the catalytic activity evaluation, the measurement results for LDPE only (measurement results when MFI-type zeolite was not used) were used as Reference Example 1. The results are shown in Table 4 below. [Table 4]

[0165] As shown in Table 2, the MFI-type zeolite of the example had a higher crystallinity retention rate compared to Comparative Examples 3, 5, and 6, which had an average primary crystal diameter of less than 0.1 μm, and Comparative Example 9, which had an alkali metal content exceeding 0.05 mass%. Furthermore, as shown in Table 3, the MFI-type zeolite of the example had a higher crystallinity retention rate compared to Comparative Examples 1 to 3 and 6, which had a standard deviation exceeding 15 μm, at a shear rate of 100 s. -1 The viscosity was low. Furthermore, as shown in Table 4, the MFI-type zeolite of the example had lower decomposition start and end temperatures for LDPE compared to Comparative Example 7, which had an acid content of less than 0.50 mmol / g, and Comparative Example 8, which had an SDA content exceeding 1.0% by mass. From these results, it was understood that the MFI-type zeolite of the example has excellent catalytic activity as well as excellent durability and handling properties.

[0166] The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2024-174392, filed on October 3, 2024, are incorporated herein by reference as part of the disclosure of the specification.

Claims

1. An MFI-type zeolite having a molar ratio of silica to alumina of 40 to 150, an average primary crystal diameter of 0.1 μm to 5 μm, a particle size of 30 μm or less at which the cumulative volume from the smallest particles in the volume particle size distribution accounts for 90%, a structure directing agent content of 1.0 mass% or less, an alkali metal content of 0.05 mass% or less, and an acid content of 0.50 mmol / g or more.

2. The MFI-type zeolite according to claim 1, wherein the particle diameter at which the cumulative volume from the small particle side in the volume particle size distribution accounts for 10% is 0.5 μm or more.

3. The MFI-type zeolite according to claim 1 or 2, wherein the crystallinity retention rate is 70% or more when the MFI-type zeolite is hydrothermally treated at 1050°C for 3 hours in an atmosphere containing 50% by volume of water vapor.

4. The MFI-type zeolite according to claim 1 or 2, wherein the amount of water vapor adsorbed at a temperature of 25°C and a relative humidity of 90% is 15% by mass or less.

5. The MFI-type zeolite according to claim 1 or 2, wherein the amount of water vapor adsorbed at a temperature of 25°C and a relative humidity of 60% is 14% by mass or less.

6. BET specific surface area is 300 m ２ / g or more 450m ２ The MFI-type zeolite according to claim 1 or 2, wherein the amount is less than or equal to / g.

7. The MFI-type zeolite according to claim 1 or 2, wherein the aspect ratio of the primary particles is 3.0 or less.

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