Beta zeolite and method for producing the same

Abstract

The objective is to provide at least one of the following: a beta-zeolite having excellent catalytic activity and hydrothermal resistance, and a method for producing the same. [Solution] The total alkali metal content is 0.5% by mass or less, the SDA content is 4.0% by mass or less, the molar ratio of silica to alumina is between 20 and 35, and the IR spectrum is 1860±10 cm⁻¹. -1 The height intensity of the peak with the peak top is 3735±10cm. -1 Beta zeolite having a peak top and a peak height-to-intensity ratio of 1.90 or less.

Description

[Technical Field]

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

[0002] Beta-zeolites are used industrially as catalysts in various fields. Among beta-zeolites, those with a low molar ratio of silica to alumina (hereinafter also referred to as the "SiO2 / Al2O3 molar ratio") (for example, zeolites with an SiO2 / Al2O3 molar ratio of 40 or less) exhibit high catalytic activity. For this reason, beta-zeolites with a low SiO2 / Al2O3 molar ratio (hereinafter also referred to as "low-silica beta-zeolites") are used in various catalytic applications, such as catalysts that decompose nitrogen oxides (NOx) using a reducing agent (for example, ammonia (NH3)) (hereinafter also referred to as "nitrogen oxide reduction catalysts") (for example, Patent Document 1).

[0003] Beta-zeolites, used as catalysts such as nitrogen oxide reduction catalysts, are typically synthesized by crystallizing raw materials containing organic structure directing agents (hereinafter also referred to as "SDA") and alkali metals. Beta-zeolites synthesized in this way contain both SDA and alkali metals. The SDA contained in beta-zeolites is mainly present within the pores of the beta-zeolite, while the alkali metals contained in beta-zeolites are mainly present as counterions (hereinafter simply referred to as "counterions") to compensate for the charge of the skeletal structure.

[0004] SDA contained in beta-zeolite can inhibit contact between the beta-zeolite and the reaction substrate, potentially reducing the catalytic activity and adsorption properties of the beta-zeolite. Furthermore, it is known that the crystal structure of beta-zeolite is easily destroyed when exposed to a high-temperature atmosphere containing water vapor while containing alkali metals. For this reason, when using beta-zeolite as a catalyst, it is common practice to remove SDA and alkali metals from the synthesized beta-zeolite to reduce the content of SDA and alkali metals (for example, Patent Document 1).

[0005] To remove SDA and alkali metals from synthesized beta-zeolite, it is common to perform a first calcination treatment to remove SDA, then contact with an ammonium-containing solution to exchange alkali metal ions for ammonium ions, and then perform a second calcination treatment to convert ammonium ions into protons (for example, Patent Document 1).

[0006] Furthermore, catalysts such as nitrogen oxide reduction catalysts are sometimes used to decompose specific components contained in high-temperature gases containing water vapor (for example, nitrogen oxides in exhaust gases emitted from internal combustion engines). For this reason, beta-zeolites intended for use as catalysts require not only high catalytic activity but also high hydrothermal durability. However, zeolites have the property that the more aluminum they contain, the more silanol defects (hereinafter also called "silanol defects") tend to increase in their skeletal structure, and the skeletal structure tends to collapse starting from these silanol defects. For this reason, while low-silica beta-zeolites have excellent catalytic activity, they have the problem of low hydrothermal durability and a tendency for catalytic activity to decrease in high-temperature atmospheres containing water vapor.

[0007] Given this situation, methods to improve the hydrothermal durability of beta-zeolite have been investigated in recent years. For example, Non-Patent Literature 1 describes a process in which beta-zeolite is calcined in a steam-containing atmosphere (hereinafter also referred to as "steam treatment") to condense silanol defects and improve hydrothermal durability.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Non-Patent Documents

[0009]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] As described in Patent Document 1, by removing SDA and alkali metals from the synthesized beta zeolite, beta zeolite suitable for catalyst use can be obtained. However, in the method of Patent Document 1 (a method in which after performing the first calcination treatment for removing SDA, contacting with an ammonium-containing solution to ion-exchange alkali metal ions with ammonium ions, and further performing the second calcination treatment for converting ammonium ions to protons), the beta zeolite obtained has an increase in silanol defects with a decrease in the SiO2 / Al2O3 molar ratio (that is, an increase in aluminum). Therefore, the low-silica beta zeolite obtained by the method of Patent Document 1 has a problem of insufficient hydrothermal durability.

[0011] On the other hand, as in Non-Patent Document 1, if steam treatment is performed on beta zeolite, silanol defects can be reduced and the hydrothermal durability of beta zeolite can be improved. However, in this method, while silanol defects are reduced, aluminum in the framework structure, which is the catalytic active site, desorbs. Therefore, the low-silica beta zeolite obtained by the method of Non-Patent Document 1 has a problem of insufficient catalytic activity.

[0012] This disclosure aims to provide at least one of the following: a beta-zeolite having excellent catalytic activity and hydrothermal durability, and a method for producing the same. [Means for solving the problem]

[0013] The present inventors investigated a series of processes, from crystallization of the raw materials to the removal of SDA and alkali metals, in order to achieve both catalytic activity and hydrothermal durability, which were in a trade-off relationship in conventional methods (methods described in Patent Document 1 and Non-Patent Document 1) for low-silica beta-zeolite. As a result, they found that by removing SDA and alkali metals from low-silica beta-zeolite synthesized by a predetermined method using a predetermined method, silanol defects can be reduced without significantly affecting the aluminum in the skeletal structure, which is the catalytic active site. Furthermore, they found that the low-silica beta-zeolite obtained in this way exhibits excellent catalytic activity and hydrothermal durability, thus completing the present invention.

[0014] In other words, the present invention is as claimed, and the gist of this disclosure is as follows. [1] The total alkali metal content is 0.5% by mass or less, the organic structure directing agent content is 4.0% by mass or less, the molar ratio of silica to alumina is 20 to 35, and the IR spectrum is 1860 ± 10 cm⁻¹. -1 The height intensity of the peak with the peak top is 3735±10cm. -1 Beta zeolite having a peak top and a peak height-to-intensity ratio of 1.90 or less. [2] The beta-zeolite according to [1], wherein the full width at half maximum of the X-ray diffraction peak having a peak top at d = 3.95 ± 0.10 Å in the X-ray diffraction pattern when CuKα rays are used as the source is 2θ = 0.475° or less. [3] The beta-zeolite described in [1] or [2] above, wherein the total acid content is 0.75 mmol / g or more and 1.70 mmol / g or less. [4] The beta-zeolite according to any one of [1] to [3] above, wherein the average crystal diameter is 0.70 μm or less. [5] A method for producing beta-zeolite according to any one of [1] to [4], comprising the steps of: crystallizing a composition comprising a silica source, an alumina source, a potassium source, an organic structure directing agent source, and water, wherein the molar ratio of silica to alumina is 20 to 60 and the molar ratio of fluorine to silica is 0.01 or less to obtain a crystalline product; contacting the crystalline product with an ammonium-containing solution to obtain an acid-treated product; and calcining the acid-treated product at 400°C to 800°C in an atmosphere containing less than 5% by volume of water vapor. [Effects of the Invention]

[0015] This disclosure provides at least one of the following: a beta-zeolite having excellent catalytic activity and hydrothermal durability, and a method for producing the same. [Modes for carrying out the invention]

[0016] The beta-zeolite of this disclosure will be described below with reference to an example of an embodiment. This disclosure includes any combination of each configuration and parameter disclosed herein, as well as any combination of the upper and lower limits of the values ​​disclosed herein.

[0017] The terms used in this embodiment are as follows:

[0018] A "zeolite" is a compound in which the skeletal atoms (hereinafter also referred to as "T atoms") have a regular structure mediated by oxygen (O), and the T atoms consist of at least one of a metal atom and / or a metalloid atom. Examples of metal atoms include one or more selected from the group consisting of aluminum (Al), iron (Fe), and gallium (Ga), with aluminum being preferred. Examples of metalloid atoms include one or more selected from the group consisting of boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te), with silicon being preferred.

[0019] 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 metals and metalloids (hereinafter also referred to as a "nonmetallic atom") in the T atom. An example of a nonmetallic atom is phosphorus (P). Examples of zeolite-like substances include complex phosphorus compounds such as aluminophosphate (AlPO) and silicoaluminophosphate (SAPO). In this embodiment, zeolite is distinguished from zeolite-like substances.

[0020] In zeolites and zeolite-like materials, the "regular structure of T atoms mediated by oxygen (hereinafter also referred to as the "zeolite structure")" refers to the skeletal structure specified by the structural code (hereinafter simply referred to as the "structural code") defined by the Structure Commission of the International Zeolite Association. In this embodiment, the structural code also includes the structural codes of polymorphs (crystalline polymorphs) described on the International Zeolite Association's website, "http: / / www.iza-structure.org / databases / ". For example, the beta structure, which is the skeletal structure of beta zeolite, is a skeletal structure specified by the structural code "Beta," and is a twin-crystal skeletal structure containing polymorphs Beta_A and Beta_B in any proportion. The zeolite structure can be identified by comparing it with the XRD patterns (hereinafter also referred to as the "reference patterns") of each structure described in Collection of simulated XRD powder patterns for zeolites, Fifth revised edition (2007). In this embodiment, the skeletal structure, crystal structure, and crystalline phase are used interchangeably.

[0021] "Aluminosilicate" is a composite oxide having a structure consisting of repeating networks of aluminum (Al) and silicon (Si) mediated by oxygen (O). In this embodiment, aluminosilicate also includes forms in which aluminum (Al) and silicon (Si) have a structure consisting of repeating networks mediated by oxygen (O), and in which a portion of the aluminum (for example, 30% or less of the aluminum as T atoms) is substituted with other metal atoms. Among aluminosilicates, those having crystalline XRD peaks in their powder X-ray diffraction (hereinafter also referred to as "XRD") patterns are called "crystalline aluminosilicates," and those not having crystalline XRD peaks are called "amorphous aluminosilicates." Note that zeolites in which the T atoms consist of aluminum (Al) and silicon (Si) are crystalline aluminosilicates, and those in which a portion of the aluminum (for example, 30% or less of the aluminum as T atoms) is substituted with other metal atoms are also considered crystalline aluminosilicates.

[0022] In this embodiment, the XRD pattern is measured using CuKα radiation as the source, and the following conditions are used as measurement conditions. Acceleration current / voltage: 40mA / 40kV Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Continuous scan Scanning conditions: 40° / min Measurement range: 2θ = 3° to 43° Divergence vertical limiting slit: 10mm Divergence / Induction Slit: 1° Light-receiving slit: open Solar light receiving slit: 5° Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter

[0023] XRD patterns can be measured using a general powder X-ray diffractometer (e.g., Ultima IV, Rigaku Corporation). Crystalline XRD peaks are peaks whose peak top 2θ is identified and detected during XRD pattern analysis using general analysis software (e.g., SmartLab Studio II, Rigaku Corporation). The following conditions can be used for XRD pattern analysis. Fitting conditions: Automatic, background refinement Dispersive pseudo-Voigt function (peak shape) Background removal method: Fitting method Kα2 removal method: Kα1 / Kα2 ratio=0.497 Smoothing method: B-Spline curve Smoothing conditions: Second derivative method, σ cut value = 3, χ threshold = 1.5

[0024] The composition in this embodiment, such as the SiO2 / Al2O3 molar ratio, can be measured by ICP analysis using a general inductively coupled plasma emission spectrometer (for example, OPTIMA7300DV, manufactured by PERKIN ELMER).

[0025] The "average crystal diameter" is the average value of the particle diameter of primary particles. Primary particles are the smallest particles that can be observed independently under scanning electron microscopy (hereinafter also referred to as "SEM") conditions. SEM observation can be performed using a general scanning electron microscope (for example, instrument name: JSM-IT200, manufactured by JEOL Ltd.). Acceleration voltage: 6kV Magnification: 10,000±5,000x

[0026] The average crystal diameter may be calculated by measuring the maximum Feret diameter in the smallest unit of particles (primary particles) observed independently and calculating the arithmetic mean of 50 ± 5 particles. In the present embodiment, the "maximum Feret diameter" is the value obtained by sandwiching the smallest unit of particles (primary particles) observed independently between two parallel lines, where the distance between the parallel lines is maximized. However, secondary aggregates (aggregates) formed by the aggregation of primary particles are not independent particles and are not used in the calculation of the average crystal diameter. In addition, the number of SEM observation images used to determine the average crystal diameter may be any number as long as the number of primary particles can be observed as described above, and one or more SEM observation images may be used.

[0027] The "silanol intensity ratio" is the ratio of the height intensity of the peak having a peak top at 1860 ± 10 cm -1 (1850 cm -1 or more and 1870 cm -1 or less) in the IR spectrum to the height intensity of the peak having a peak top at 3735 ± 10 cm -1 (3725 cm -1 or more and 3745 cm -1 or less) in the IR spectrum. The "silanol intensity ratio" is an index of the amount of silanol defects in beta zeolite, and the smaller the silanol intensity ratio, the smaller the amount of silanol defects. The silanol intensity ratio can be determined from the IR spectrum obtained by Fourier transform infrared spectroscopy (hereinafter also referred to as "FT-IR measurement") using a general Fourier transform infrared spectrometer (hereinafter also referred to as "FT-IR measurement device") (for example, device name: Jasco FT / IR-6100, manufactured by JASCO Corporation). The FT-IR for measuring the IR spectrum is obtained by inserting a sample (beta zeolite) disk-molded (0.01 g / cm 2 ) with a press into a heating unit (for example, device name: Standard optical path type in-situ cell for spectroscopy 2000-1431, manufactured by Makuhari Glass Co., Ltd.), performing pretreatment under vacuum at 450 °C (sample temperature) for 1 hour, and then performing the following conditions [[ID=X]] Measurement method: Heating transmission method Measurement sample: 0.01 g Measurement mode: Continuous scan Measurement temperature: Under vacuum, 200℃ (product temperature) Measurement range: 350~4000cm -1 Resolution: 2.0cm -1 Total number of times: 128 Zero Filling: ON Detector: TGS (Triglycine sulfate)

[0028] To determine the silanol intensity ratio from the obtained IR spectrum, waveform processing can be performed using general analysis software (for example, Spectra Manager Version 2 Version 2.15.11, manufactured by JASCO Corporation). Specifically, the base start is set to 1580 cm⁻¹. -1 , base end 2100cm -1 , and base start at 3000cm -1 , base end 3800cm -1 These ranges are then baseline-corrected to perform baseline processing. From the baseline-processed IR spectrum, 1860 ± 10 cm⁻¹ is obtained. -1 Among the peaks with peak tops within the specified range, identify the peak with the highest peak top height intensity (hereinafter also referred to as "Peak P1"), and determine the peak with the highest peak top height intensity (3735±10cm). -1 Among the peaks with peak tops within the specified range, identify the peak with the highest peak top intensity (hereinafter also referred to as "peak P2"). The silanol intensity ratio can be calculated using the following formula (1) with the peak top intensity of the identified peak P1 (hereinafter also referred to as "height intensity HI1") and the peak top intensity of the identified peak P2 (hereinafter also referred to as "height intensity HI2"). Silanol intensity ratio = (Height and intensity of peak P2 HI2) / (Height and intensity of peak P1 HI1) (1)

[0029] Furthermore, in the IR spectrum measured by a Fourier transform infrared spectrophotometer, the value is 1860 ± 10 cm⁻¹. -1Peak P1, which has its peak top at 3735±10cm, is a peak originating from the skeletal vibration of beta zeolite, and is 3735±10cm. -1 Peak P2, which has a peak top at [location], is a peak derived from silanols contained in the beta-zeolite. In other words, the silanol intensity ratio is an index of the amount of silanol defects contained in the entire beta-zeolite, based on the skeletal vibration of the zeolite, and functions as an indicator of the amount of silanol defects.

[0030] <Beta Zeolite> The beta zeolite of this embodiment will be described below.

[0031] The beta-zeolite of this embodiment has a total alkali metal content of 0.5% by mass or less, an organic structure directing agent (SDA) content of 4.0% by mass or less, an SiO2 / Al2O3 molar ratio of 20 to 35, and a silanol intensity ratio of 1.90 or less. Having these characteristics, the beta-zeolite of this embodiment can exhibit excellent catalytic activity and hydrothermal durability.

[0032] The beta-zeolite of this embodiment has an SiO2 / Al2O3 molar ratio of 20 to 35. This SiO2 / Al2O3 molar ratio allows the beta-zeolite of this embodiment to exhibit excellent catalytic activity and hydrothermal durability. If the SiO2 / Al2O3 molar ratio is less than 20, hydrothermal durability decreases. On the other hand, if the SiO2 / Al2O3 molar ratio exceeds 35, the total acid site amount tends to decrease, as described later, potentially leading to a decrease in catalytic activity (e.g., nitrogen oxide reduction characteristics). While the SiO2 / Al2O3 molar ratio of the beta-zeolite of this embodiment can be between 20 and 35, it is preferable that it be 20 or higher, 21 or higher, or 22 or higher, and also preferable that it be 35 or lower, 32 or lower, or 30 or lower, as this allows for further improvement in catalytic activity and hydrothermal durability. While the combination of the upper and lower limits for the SiO2 / Al2O3 molar ratio described above is arbitrary, the SiO2 / Al2O3 molar ratio of the beta zeolite in this embodiment is more preferably 20 to 32, and more preferably 20 to 30, in that it is expected to further improve catalytic activity and hydrothermal durability.

[0033] The beta-zeolite of this embodiment may contain T atoms other than aluminum (Al) and silicon (Si) as long as the SiO2 / Al2O3 molar ratio is 20 or more and 35 or less. However, it is preferable that it be a crystalline aluminosilicate, and more preferably a crystalline aluminosilicate in which the T atoms consist only of aluminum (Al) and silicon (Si), as this can be expected to further improve catalytic activity.

[0034] The beta-zeolite of this embodiment has a silanol intensity ratio of 1.90 or less. A silanol intensity ratio of 1.90 or less allows the beta-zeolite of this embodiment to exhibit excellent catalytic activity and hydrothermal resistance. On the other hand, if the silanol intensity ratio exceeds 1.90, structural defects increase, reducing the hydrothermal durability of the beta-zeolite. While the silanol intensity ratio of the beta-zeolite of this embodiment should be 1.90 or less, a ratio of 1.85 or less or 1.80 or less is preferable in that further improvement in hydrothermal durability can be expected. The lower limit of the silanol intensity ratio is not particularly limited, but from the viewpoint of having unavoidable structural defects, values ​​greater than 0, 0.30 or more, 0.50 or more, or 0.90 or more are preferable. While the combination of the upper and lower limits of the silanol intensity ratio described above is arbitrary, the silanol intensity ratio of the beta-zeolite in this embodiment is preferably greater than 0 and 1.90 or less, more preferably between 0.30 and 1.85, and even more preferably between 0.5 and 1.80, in that it can be expected to further improve hydrothermal durability.

[0035] The beta-zeolite of this embodiment has a total alkali metal content of 0.5% by mass or less. By having a total alkali metal content of 0.5% by mass or less, the beta-zeolite of this embodiment can suppress the destruction of the crystal structure by alkali metals in a high-temperature atmosphere containing water vapor, and can exhibit excellent hydrothermal heat resistance. On the other hand, if the total alkali metal content exceeds 0.5% by mass, the destruction of the crystal structure by alkali metals in a high-temperature atmosphere containing water vapor is promoted, and the hydrothermal heat resistance decreases.

[0036] The total alkali metal content of the beta-zeolite in this embodiment may be 0.5% by mass or less, but it is preferably 0.30% by mass or less, more preferably 0.28% by mass or less, and even more preferably 0.20% by mass or less, in order to further improve hydrothermal heat resistance. The lower limit of the total alkali metal content is not particularly limited, but examples include 0% by mass or more, greater than 0% by mass, or 0.01% by mass or more, in order to avoid the presence of unavoidable alkali metals. The combination of the upper and lower limits of the total alkali metal content described above is arbitrary, but the total alkali metal content of the beta-zeolite in this embodiment is preferably 0% by mass or more and 0.5% by mass or less, more preferably 0% by mass or more and 0.30% by mass or less, and even more preferably 0.01% by mass or more and 0.20% by mass or less, in order to further improve hydrothermal durability. In this embodiment, a content of 0% by mass of a predetermined component means that the predetermined component is not present.

[0037] The total alkali metal content is the ratio of the alkali metal (M) content (M2O equivalent) to the total content of silicon (Si) (SiO2 equivalent), aluminum (Al) (Al2O3 equivalent), and alkali metal (M) (M2O equivalent) in beta-zeolite, and can be calculated using the following formula (2). Total alkali metal content [mass%] ={M2O / (SiO2+Al2O3+M2O)}×100 (2) In formula (2) above, M2O represents the alkali metal (M) content [g] converted to M2O, SiO2 represents the silicon (Si) content [g] converted to SiO2, and Al2O3 represents the aluminum (Al) content [g] converted to Al2O3.

[0038] Furthermore, if the beta-zeolite contains two or more alkali metals, the M2O in formula (2) above should be calculated by converting each alkali metal (M) to M2O equivalent and using the sum of those values. For example, if the beta-zeolite contains sodium and potassium as alkali metals, the total alkali metal content can be calculated from the following formula (2'). Total alkali metal content [mass%] ={(Na2O+K2O) / (SiO2+Al2O3+Na2O+K2O)}×100 (2') In formula (2') above, SiO2 and Al2O3 are equivalent to SiO2 and Al2O3 in formula (2) above, respectively, Na2O represents the sodium content [g] converted to Na2O, and K2O represents the potassium content [g] converted to K2O.

[0039] The alkali metals that can be contained in the beta-zeolite of this embodiment are not particularly limited, but it is preferable that they contain at least potassium. Furthermore, the alkali metals that can be contained in the beta-zeolite of this embodiment may be just one alkali metal or two or more alkali metals, but it is preferable that it be just one alkali metal, and preferably potassium.

[0040] The beta-zeolite of this embodiment has an SDA content of 4.0% by mass or less. By having an SDA content of 4.0% by mass or less, the beta-zeolite of 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 4.0% by mass, SDA inhibits contact with the reaction substrate, and the catalytic activity decreases.

[0041] The SDA content of the beta-zeolite in this embodiment may be 4.0% by mass or less, but it is preferable that it be 3.0% by mass or less, 2.5% by mass or less, 2.3% by mass or less, 2.0% by mass or less, or 1.5% by mass or less, in order to further improve catalytic activity. The lower limit of the SDA content is not particularly limited, but examples include 0% by mass or more, greater than 0% by mass, or 0.01% by mass or more, in order to not inhibit contact between the beta-zeolite and the reaction substrate. The combination of the upper and lower limits of the SDA content described above is arbitrary, but in this embodiment, the SDA content of the beta-zeolite is preferably 0% by mass or more and 3.0% by mass or less, more preferably 0% by mass or more and 2.5% by mass or less, even more preferably 0% by mass or more and 2.3% by mass or less, particularly preferably 0% by mass or more and 2.0% by mass or less, and most preferably 0% by mass or more and 1.5% by mass or less, in order to further improve catalytic activity.

[0042] The SDA content can be determined by dividing the mass of SDA contained in the beta-zeolite (hereinafter also referred to as "SDA mass") by the mass of the beta-zeolite (hereinafter also referred to as "Beta mass") and converting this to a percentage. For determining the SDA content, the dry mass of the beta-zeolite dried in an air atmosphere at 110°C for 4 hours should be used as the Beta mass. For determining the SDA content, the change in mass when the beta-zeolite is heated from 300°C to 700°C should be used as the SDA mass. The change in mass when the beta-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℃

[0043] In this embodiment, the mass change (mass decrease) of the beta-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 beta-zeolite above 700°C is determined to be a mass change due to the condensation of silanols at the junction surfaces of the polymorphic beta-zeolite. Therefore, in this embodiment, the mass change (mass decrease) of the beta-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.

[0044] The beta-zeolite in this embodiment is not particularly limited, but it is preferable that its average crystal diameter is 0.20 μm or more, 0.22 μm or more, or 0.24 μm. An average crystal diameter of 0.20 μm or more can be expected to further improve hydrothermal heat resistance. Furthermore, although the beta-zeolite in this embodiment is not particularly limited, it is preferable that its average crystal diameter is 1.00 μm or less, 0.80 μm or less, 0.70 μm or less, 0.50 μm or less, or 0.35 μm or less, from the viewpoint that the diffusivity of the reaction substrate in the catalytic reaction can be improved and further improvement in catalytic activity can be expected. In particular, beta-zeolite with an average crystal diameter of 0.70 μm or less is more likely to have its alkali metal content and silanol intensity ratio reduced during the manufacturing process compared to beta-zeolite with an average crystal diameter exceeding 0.70 μm, and therefore, in addition to catalytic activity, further improvement in hydrothermal durability can be expected. The combination of the upper and lower limits for the average crystal diameter mentioned above is arbitrary, but the average crystal diameter of the beta-zeolite in this embodiment is preferably 0.20 μm to 1.00 μm, 0.20 μm to 0.80 μm, 0.20 μm to 0.70 μm, 0.20 μm to 0.50 μm, 0.20 μm to 0.35 μm, or 0.22 μm to 0.35 μm.

[0045] The beta-zeolite of this embodiment is not particularly limited, but it is preferable that the full width at half maximum (FWHM) of the XRD peak with the highest peak height intensity (hereinafter also referred to as the "XRD main peak") among the XRD peaks with a peak top at d = 3.95 ± 0.10 Å in the XRD pattern when CuKα radiation is used as the source is 2θ = 0.475° or less. Having an XRD main peak with a FWHM of 2θ = 0.475° or less allows the beta-zeolite of this embodiment to have higher crystallinity, and even with a low SiO2 / Al2O3 molar ratio of 35 or less, hydrothermal durability is likely to be further improved. The FWHM of the XRD main peak is preferably 0.475° or less, 0.460° or less, 0.450° or less, or 0.420°, in that it is expected to further improve hydrothermal durability. The lower limit of the FWHM of the XRD main peak is not particularly limited, but examples include greater than 0°, 0.150° or more, or 0.200° or more. The combination of the upper and lower limits of the full width at half maximum (FWHM) mentioned above is arbitrary, but the FWHM of the XRD main peak is preferably greater than 0° and 0.475° or less, more preferably between 0.150° and 0.460°, even more preferably between 0.200° and 0.450°, and particularly preferably between 0.200° and 0.420°, in which further improvement in hydrothermal durability can be expected. In this embodiment, FWHM refers to the full width at half maximum.

[0046] The beta-zeolite of this embodiment is not particularly limited, but it is preferable to have at least the XRD peaks shown in Table 1 below. In this embodiment, having the XRD peaks shown in the table means that the peak top is within the range of the lattice plane spacing d (Å) shown in the table, and that the peaks having the relative peak intensities shown in the table can be confirmed in the XRD pattern. [Table 1]

[0047] The beta-zeolite of this embodiment is not particularly limited, but it is more preferable that it has at least the XRD peaks shown in Table 2 below. [Table 2]

[0048] The beta-zeolite of this embodiment may include other XRD peaks attributable to beta-zeolite, in addition to the XRD peaks in Table 2 and Table 3 above. Furthermore, the beta-zeolite of this embodiment may include XRD peaks with a relative intensity of less than 1%, in addition to the peaks in Table 2 and Table 3 above. However, such low-intensity XRD peaks with a relative intensity of less than 1% do not need to be considered for crystal structure identification.

[0049] The beta-zeolite of this embodiment tends to have higher crystallinity and greater hydrothermal resistance by having the XRD peaks shown in Table 2 and Table 3 above. The XRD peaks shown in Table 2 and Table 3 above are easily observed when the beta-zeolite of this embodiment is a crystalline aluminosilicate.

[0050] The beta-zeolite of this embodiment is not particularly limited, but it is preferable that the total acid site content is 0.75 mmol / g or more, 0.80 mmol / g or more, 0.85 mmol / g or more, or 0.90 mmol / g or more. When the total acid site content is 0.75 mmol / g or more, the active sites of the catalyst in the beta-zeolite of this embodiment increase, and catalytic activity is more likely to be further improved. In the beta-zeolite of this embodiment, the upper limit of the total acid site content is preferably 1.70 mmol / g or less, 1.60 mmol / g or less, or 1.50 mmol / g or less, in which further improvement in hydrothermal durability can be expected. The combination of the upper and lower limits of the total acid content described above is arbitrary, but the total acid content of the beta-zeolite in this embodiment is preferably 0.75 mmol / g or more and 1.70 mmol / g or less, more preferably 0.80 mmol / g or more and 1.70 mmol / g or less, even more preferably 0.85 mmol / g or more and 1.70 mmol / g or less, even more preferably 0.90 mmol / g or more and 1.70 mmol / g or less, and most preferably 0.90 mmol / g or more and 1.60 mmol / g or less.

[0051] The total acid site amount is the amount of acid sites present in the zeolite per unit mass. The measurement of the total acid site amount can be determined by the NH3-TPD method using a general temperature-programmed desorption analyzer (for example, device name: BELCATII, manufactured by MicrotracBEL). For the measurement sample used in the NH3-TPD method, zeolite (0.05 g) pretreated at 500 °C for 1 hour can be used in an atmosphere where helium gas flows at 50 ml / min.

[0052] <NH3-TPD Measurement> The measurement of the total acid site amount by the NH3-TPD method may be carried out under the following conditions. For the beta zeolite (measurement sample) after pretreatment, a mixed gas containing 1% by volume of ammonia and 99% by volume of helium gas is passed through the measurement sample at 100 °C to saturate the measurement sample with ammonia. After the mixed gas has been passed through for 30 minutes, the mixed gas is replaced with helium gas, and the residual ammonia in the atmosphere is removed by passing helium gas at 100 °C for 15 minutes. After the removal of the residual ammonia, the temperature is raised from 100 °C to 710 °C at a heating rate of 10 °C / min under a helium flow rate of 30 mL / min. Thereby, the ammonia adsorbed on the beta zeolite (measurement sample) is desorbed from the beta zeolite (measurement sample). The ammonia desorbed from the beta zeolite (measurement sample) is continuously quantified by a gas chromatograph equipped with a thermal conductivity detector (TCD), and thereby an ammonia desorption spectrum (hereinafter also referred to as a "TPD spectrum") can be obtained.

[0053] The obtained TPD spectrum can be analyzed by separating the spectrum showing ammonia released from the beta-zeolite (sample) (hereinafter also referred to as the "ammonia desorption spectrum") using general analysis software (for example, software name: Chem Master, Microtrac for Windows ver1.4.9, manufactured by MicrotracBEL). Specifically, 100°C in the heating process from 100°C to 710°C is used as the base start, and 700°C in the heating process from 100°C to 710°C is used as the base end, and the ammonia desorption section of the TPD spectrum is baseline-processed. Of the baseline-processed TPD spectrum, the spectrum of the ammonia desorption section (i.e., the range from 100°C to 700°C in the heating process) is taken as the ammonia desorption spectrum. The area (integral value) of this ammonia desorption spectrum is calculated and taken as the amount of ammonia released from the beta-zeolite (sample) (hereinafter also referred to as the "ammonia desorption amount"). The total acid content of the beta-zeolite can be determined by dividing the amount of ammonia removed (mmol) by the mass (g) of the beta-zeolite used in the measurement. The mass (g) of the pre-treated beta-zeolite (i.e., the sample used for measurement) should be used as the mass of the beta-zeolite used in the measurement.

[0054] In this embodiment, the beta-zeolite is preferably of the proton type in that further improvement in catalytic activity can be expected. Here, the proton type means that the counterion is a proton (H + This means that the counterions are all protons, but it does not mean that all counterions are protons, but rather that it is permissible for the counterions to contain trace amounts of alkali metal ions in addition to protons. In this embodiment, trace amounts of alkali metal ions refer to an amount of alkali metal ions such that the alkali metal content is 0.5% by mass or less. In other words, the beta zeolite of this embodiment, whose cation type is proton type, includes beta zeolite in which all counterions are protons and beta zeolite in which protons (H) are present as counterions. +This includes zeolites containing alkali metal ions in an amount such that the alkali metal content is 0.5% by mass or less. In this embodiment, as an example, if the total alkali metal content of the zeolite is 0.5% by mass or less, and the pH of the zeolite slurry obtained by dispersing 2g of the zeolite in 18g of pure water at 25°C (i.e., obtained with a solid content concentration of 10% by mass) (hereinafter also referred to as "slurry pH") is less than 7, then it can be determined that the cation type of the zeolite is proton type.

[0055] The beta-zeolite of this embodiment may contain fluorine (F) and phosphorus (P) to an extent that does not affect the effects of the invention, but from the viewpoint of suitability for industrial production, it is preferable that it substantially does not contain fluorine (F) and phosphorus (P), and more preferable that it does not contain fluorine (F) and phosphorus (P). In this embodiment, substantially free of the predetermined components means that the content of the predetermined components is below the detection limit (for example, fluorine content is less than 0.01% by mass, phosphorus content is less than 0.01% by mass, or the total content of fluorine and phosphorus is less than 0.01% by mass).

[0056] The beta-zeolite of this embodiment is not limited to its applications and can be used in applications of conventionally known beta-zeolites, for example, in at least one of the applications of a catalyst and an adsorbent. The adsorbent can function as a hydrocarbon adsorbent, an ion exchange agent, or a separator for specific components from mixed gases. The beta-zeolite of this embodiment can be used as a solid acid catalyst with high hydrothermal resistance. Specific examples of solid acid catalysts include one or more selected from the group consisting of exhaust gas purification catalysts, toluene disproportionation catalysts for catalyzing toluene disproportionation, xylene isomerization catalysts for catalyzing xylene isomerization, MTO (Methanol To Olefins) reaction catalysts, and MTA (Methanol To Aromatics) reaction catalysts, with exhaust gas purification catalysts being preferred. Furthermore, the beta-zeolite of this embodiment can be used as an exhaust gas treatment catalyst for internal combustion engines, and even further as an automobile exhaust gas treatment catalyst. Examples of the above-mentioned exhaust gas include nitrogen oxide-containing gases, and the exhaust gas purification catalyst is preferably a nitrogen oxide reduction catalyst.

[0057] When using the beta-zeolite of this embodiment as an adsorbent or solid acid catalyst, the beta-zeolite of this embodiment may be used as is, or it may be used as an adsorbent or solid acid catalyst after incorporating a predetermined component into the beta-zeolite of this embodiment. In other words, the beta-zeolite of this embodiment may be used as is as an adsorbent or solid acid catalyst, or it may be used as a carrier for incorporating a predetermined component in the adsorbent or solid acid catalyst.

[0058] The solid acid catalyst using the beta-zeolite of this embodiment only needs to contain the beta-zeolite of this embodiment. In other words, the solid acid catalyst using the beta-zeolite of this embodiment may consist only of the beta-zeolite of this embodiment, or it may further contain other components such as a binder or zeolites other than the beta-zeolite of this embodiment in addition to the beta-zeolite of this embodiment.

[0059] In the solid acid catalyst using the beta-zeolite of this embodiment, the beta-zeolite of this embodiment is preferably used as a carrier to contain one or more elements selected from groups 8, 9, 10, and 11 of the periodic table (hereinafter also referred to as "active metal elements"), from the viewpoint of easily obtaining higher catalytic activity. In other words, the solid acid catalyst using the beta-zeolite of this embodiment is preferably made to contain the beta-zeolite of this embodiment containing active metal elements (hereinafter also simply referred to as "active metal-containing beta-zeolite of this embodiment"), from the viewpoint of easily obtaining higher catalytic activity.

[0060] In the activated metal-containing beta-zeolite of this embodiment, the activated metal element is preferably one or more selected from the group consisting of platinum (Pt), palladium (Pd), rhodium (Rh), iron (Fe), copper (Cu), cobalt (Co), manganese (Mn), and indium (In), in that higher catalytic activity can be easily obtained, and at least one of iron and copper is more preferable, with iron being even more preferable.

[0061] In the activated metal-containing beta-zeolite of this embodiment, the state of the activated metal element is not particularly limited, but examples include a compound (e.g., an oxide), a metal, an ion, an alloy, or two or more of these states.

[0062] In the activated metal-containing beta-zeolite of this embodiment, the content of the activated metal element is not particularly limited as long as it is within the range that achieves the effects of this embodiment. From the viewpoint of obtaining higher catalytic activity, the content of the activated metal element is preferably 0.05% by mass or more, more preferably 0.20% by mass or more, and even more preferably 0.30% by mass or more. Furthermore, from the viewpoint of obtaining higher catalytic activity, the upper limit of the content of the activated metal element is preferably 10.0% by mass or less, more preferably 7.0% by mass or less, and even more preferably 5.0% by mass or less. The upper and lower limits of the content of the activated metal element may be any combination of the upper and lower limits mentioned above, but from the viewpoint of obtaining higher catalytic activity, the specific range of the content of the activated metal element is preferably 0.05% by mass or more and 10.0% by mass or less, more preferably 0.20% by mass or more and 7.0% by mass or less, and particularly preferably 0.30% by mass or more and 5.0% by mass or less.

[0063] The content of the active metal element is the ratio of the content of the active metal element (A) to the total content of silicon (Si) in terms of SiO2, aluminum (Al) in terms of Al2O3, and the content of the active metal element (A) in the active metal-containing beta zeolite of this embodiment, and can be calculated from the following formula (3). Content of active metal elements [mass%] = {A / (SiO2+Al2O3+A)} × 100 ... (3) In formula (3) above, SiO2 represents the silicon (Si) content in terms of SiO2 [g], Al2O3 represents the aluminum (Al) content in terms of Al2O3 [g], and A represents the active metal element (A) content [g].

[0064] Furthermore, if the activated metal-containing beta-zeolite of this embodiment contains two or more activated metal elements (A), then the sum of the content of the two or more activated metal elements (A) may be used for A in formula (3) above.

[0065] "Containing an active metal element" means that the beta zeolite contains an active metal element, and as long as the beta zeolite contains an active metal element, it does not matter what state or location the active metal element is in. On the other hand, "supporting an active metal element" means that the beta zeolite contains an active metal element as something other than a T atom. In other words, "supporting an active metal element" means that the active metal element is contained in the beta zeolite in a state in which the active metal element does not exist as a T atom of the beta zeolite. A preferred form of "supporting an active metal element" is a state in which the active metal element does not exist as a T atom of the beta zeolite and is contained in at least one of the surface and pores of the beta zeolite. The active metal-containing beta zeolite of this embodiment is preferably the beta zeolite of this embodiment on which the active metal element is supported (hereinafter also referred to as "active metal-supported beta zeolite").

[0066] When using the solid acid catalyst containing the activated metal-containing beta-zeolite of this embodiment as a nitrogen oxide reduction catalyst, the NOx-containing fluid should be circulated through the solid acid catalyst (nitrogen oxide reduction catalyst) so that the activated metal-containing beta-zeolite comes into contact with the fluid containing at least a reducing agent, oxygen, and nitrogen oxides (hereinafter also referred to as "NOx-containing fluid"). Upon contact between the NOx-containing fluid and the activated metal-containing beta-zeolite, nitrogen oxides are reduced and decomposed. The contact conditions between the NOx-containing fluid and the activated metal-containing beta-zeolite can be those conventionally known contact conditions for nitrogen oxide reduction catalysts, and are not particularly limited. Ammonia (NH3) can be exemplified as a reducing agent contained in the NOx-containing fluid. In addition to the reducing agent, oxygen, and nitrogen oxides, the NOx-containing fluid may also contain other components such as water.

[0067] The beta-zeolite of this embodiment, as described above, can achieve both catalytic activity and hydrothermal durability, which were in a trade-off relationship in conventional methods (methods of Patent Document 1 and Non-Patent Document 1), and can exhibit excellent catalytic activity and excellent hydrothermal durability. Therefore, the beta-zeolite of this embodiment can maintain excellent catalytic activity even when exposed to a high-temperature atmosphere containing water vapor. In this embodiment, hydrothermal durability is evaluated by the catalytic activity at 200°C after hydrothermal durability treatment, and the higher the catalytic activity at 200°C after hydrothermal durability treatment, the higher the hydrothermal durability. For the hydrothermal durability treatment, a treatment in which the zeolite is exposed to an atmosphere containing 10% by volume of water vapor at 700°C for 20 hours may be used. In this embodiment, assuming an ideal gas, the volume fraction of water in the hydrothermal durability treatment atmosphere is considered to be the water vapor concentration of the hydrothermal durability treatment atmosphere.

[0068] <Method for producing beta zeolite> Next, the method for producing beta-zeolite according to this embodiment will be described. The method for producing beta-zeolite according to this embodiment includes the steps of: crystallizing a composition (hereinafter also called the "raw material composition") containing a silica source, an alumina source, a potassium source, an organic structure directing agent source (hereinafter also called the "SDA source"), and water, wherein the SiO2 / Al2O3 molar ratio is 20 or more and 60 or less, and the molar ratio of fluorine to silica (hereinafter also called the "F / SiO2 molar ratio") is 0.01 or less to obtain a crystalline product (hereinafter also called the "crystallization step"); contacting the crystalline product with an ammonium-containing solution to obtain an acid-treated product (hereinafter also called the "metal cation removal step"); and calcining the acid-treated product at 400°C to 800°C in an atmosphere with less than 5% by volume of water vapor (hereinafter also called the "SDA removal step").

[0069] (crystallization process) The method for producing beta-zeolite in this embodiment includes a step of crystallizing a raw material composition containing an SDA source, an alumina source, a silica source, a potassium source, and water, having an SiO2 / Al2O3 molar ratio of 20 to 60 and an F / SiO2 molar ratio of 0.01 or less, to obtain a crystalline product (crystallization step).

[0070] The SiO2 / Al2O3 ratio of the raw material composition is between 20 and 60. If the SiO2 / Al2O3 ratio of the raw material composition exceeds 60, the SiO2 / Al2O3 ratio of the resulting beta-zeolite may exceed 35, or even if beta-zeolite with an SiO2 / Al2O3 ratio of 20 to 35 is obtained, its crystallinity may be low, and its catalytic activity may be easily reduced. On the other hand, if the SiO2 / Al2O3 ratio of the raw material composition is less than 20, the SiO2 / Al2O3 ratio of the resulting beta-zeolite will be less than 20. While the SiO2 / Al2O3 ratio of the raw material composition should be between 20 and 60, it is preferable that it be between 20 and 50, and more preferably between 20 and 40, in order to further improve the catalytic activity and hydrothermal durability of the resulting beta-zeolite.

[0071] The F / SiO2 molar ratio of the raw material composition is 0.01 or less. If the F / SiO2 molar ratio of the raw material composition exceeds 0.01, the particle size of the resulting beta-zeolite will be larger, making it more difficult to remove alkali metals in the metal cation removal process, and the total alkali metal content of the resulting beta-zeolite will exceed 0.5% by mass. While an F / SiO2 molar ratio of 0.01 or less is sufficient, it is preferable, and more preferable, that the raw material composition is substantially free of fluorine, in order to further improve the hydrothermal durability of the resulting beta-zeolite. Note that a raw material composition being fluorine-free means that the F / SiO2 molar ratio is 0.

[0072] The raw material composition includes an SDA source. The SDA source is a substance capable of generating beta-zeolite-oriented SDA in the raw material composition, and can be exemplified as at least one of SDA and a salt of SDA. Examples of beta-zeolite-oriented SDA include tetraethylammonium cation (hereinafter referred to as "TEA"). + Also known as methylpropylpyrrolidinium cation (MPC5 + ), butylmethylpyrrolidinium cation (BMC5 + ), methylpropylpiperidinium cation (MPC6 +One or more organic cations selected from the group of ) are mentioned, and the beta zeolite of this embodiment is easier to manufacture, which is TEA + This is preferable. Examples of salts of SDA include one or more selected from the group of SDA hydroxide, halide, monocarbonate salt and monosulfate salt, and in terms of ease of production of the beta zeolite of this embodiment, it is preferable that it be one or more selected from the group of SDA hydroxide, chloride, bromide and iodide, more preferably one or more selected from the group of SDA hydroxide, bromide and iodide, even more preferably at least one of SDA hydroxide and bromide, and particularly preferably SDA hydroxide.

[0073] The raw material composition includes an alumina source. The alumina source is at least one of alumina (Al2O3) and its precursors, and examples include one or more selected from the group consisting of alumina, aluminum sulfate, aluminum nitrate, sodium aluminate, aluminum chloride, aluminum hydroxide, amorphous aluminosilicate, metallic aluminum, crystalline aluminosilicate, and aluminum alkoxide, with one or more selected from the group consisting of aluminum hydroxide, crystalline aluminosilicate, and amorphous aluminosilicate being preferred, and amorphous aluminosilicate being more preferred. If other starting materials other than the alumina source contained in the raw material composition contain aluminum, these can be considered as an alumina source. For example, if the silica source is a substance containing aluminum such as crystalline aluminosilicate or amorphous aluminosilicate, the silica source can be considered both a silica source and an alumina source.

[0074] The raw material composition includes a silica source. The silica source is at least one of silica (SiO2) or its precursors, and examples include one or more selected from the group consisting of colloidal silica, amorphous silica, sodium silicate, tetraethoxysilane, tetraethyl orthosilicate, precipitated silica, fumed silica, amorphous aluminosilicate, and crystalline aluminosilicate, with at least one of crystalline aluminosilicate and amorphous aluminosilicate being preferred, and amorphous aluminosilicate being more preferred.

[0075] The raw material composition preferably contains amorphous aluminosilicate in at least one of the alumina source and silica source, and more preferably contains amorphous aluminosilicate in both the alumina source and silica source. This tends to result in lower manufacturing costs and is industrially advantageous.

[0076] The raw material composition contains a potassium source. The potassium source may be a potassium-containing salt or compound. Examples of potassium-containing salts or compounds include one or more selected from the group consisting of potassium chloride, potassium fluoride, potassium iodide, potassium bromide, potassium sulfate, potassium hydroxide, and potassium oxide. One or more selected from the group consisting of potassium chloride, potassium bromide, and potassium hydroxide are preferred, and potassium hydroxide is more preferred, as it facilitates the production of the beta-zeolite in this embodiment. Furthermore, if other starting materials other than the alkali source contained in the raw material composition contain potassium, the potassium contained in the other starting materials can also be considered an alkali source.

[0077] The aforementioned raw material composition contains water. The water contained in the raw material composition may be deionized water, pure water, structural water, water as a solvent, etc., or water (H2O) contained in other starting materials.

[0078] The raw material composition may consist only of an SDA source, an alumina source, a silica source, a potassium source, and water, or it may further contain other substances (hereinafter also referred to as "other substances"). It is preferable that the raw material composition substantially does not contain alkali sources other than the potassium source, more preferably does not contain alkali sources other than the potassium source, and is more preferably composed only of an SDA source, an alumina source, a silica source, a potassium source, and water, as this tends to lower the silanol strength ratio of the beta-zeolite produced.

[0079] Other substances that can be included in the raw material composition include, for example, alkali sources other than potassium sources. Examples of alkali sources other than potassium include salts or compounds containing alkali metals other than potassium. Examples of alkali metals other than potassium include one or more selected from the group consisting of lithium, sodium, rubidium, and cesium, with sodium being preferred.

[0080] The raw material composition may contain alkali sources other than potassium as other substances, but the silanol intensity ratio of the beta-zeolite produced tends to decrease more easily. Therefore, it is preferable that the molar ratio of potassium to all alkali metals (M) contained in the raw material composition (hereinafter also referred to as the "K / M molar ratio") be 0.40 or higher, 0.50 or higher, 0.70 or higher, or 0.90 or higher. The upper limit of the K / M molar ratio is arbitrary, but it is preferably 1.00 or lower. The combination of the upper and lower limits of the K / M molar ratio is arbitrary, but since the silanol intensity ratio of the beta-zeolite produced tends to decrease more easily, the K / M molar ratio of the raw material composition is preferably 0.40 or higher and 1.00 or lower, more preferably 0.50 or higher and 1.00 or lower, even more preferably 0.70 or higher and 1.00 or lower, and particularly preferably 0.90 or higher and 1.00 or lower. Note that a K / M molar ratio of 1.00 means that the alkali metal contained in the raw material composition consists only of potassium.

[0081] Preferred compositions of the raw material include the following molar compositions. In the following molar compositions, SDA + The molar ratio of SiO2 represents the molar ratio of SDA to silica, for example, SDA + ga TEA + SDA in the case of + The molar ratio of SiO2 is TEA + This can be considered as the molar ratio of K / SiO2. In the following molar compositions, the K / SiO2 molar ratio represents the molar ratio of potassium to silica. In the following molar compositions, the H2O / SiO2 molar ratio represents the molar ratio of water to silica, and the OH / SiO2 molar ratio represents the molar ratio of hydroxide ions to silica. Furthermore, each compositional ratio in the following molar compositions may be any combination of the upper and lower limits listed below.

[0082] SiO2 / Al2O3 molar ratio: 20 to 60, 20 to 50, or 20 to 40.

[0083] SDA + / SiO2 molar ratio: 0.01 to 1.00, 0.01 to 0.50, 0.01 to 0.20, 0.01 to 0.15, 0.02 to 1.00, 0.02 to 0.50, 0.02 to 0.20, 0.02 to 0.15, 0.05 to 1.00, 0.05 to 0.50, 0.05 to 0.20, 0.05 to 0.15, 0.07 to 1.00, 0.07 to 0.50, 0.07 to 0.20, or 0.07 to 0.15.

[0084] K / SiO2 molar ratio: greater than 0 and less than or equal to 0.60, greater than 0 and less than or equal to 0.50, greater than 0 and less than or equal to 0.30, 0.03 to 0.60, 0.03 to 0.50, 0.03 to 0.30, 0.06 to 0.60, 0.06 to 0.50, or 0.06 to 0.30.

[0085] H2O / SiO2 molar ratio: 3 to 50, 3 to 30, 3 to 20, 3 to 19, 5 to 50, 5 to 30, 5 to 20, 5 to 19, 8 to 50, 8 to 30, 8 to 20, or 8 to 19.

[0086] OH / SiO2 molar ratio: 0.05 to 1.50, 0.05 to 1.00, 0.05 to 0.80, 0.05 to 0.60, 0.05 to 0.45, 0.10 to 1.50, 0.10 to 1.00, 0.10 to 0.80, 0.10 to 0.60, 0.10 to 0.45, 0.15 to 1.50, 0.15 to 1.00, 0.15 to 0.80, 0.15 to 0.60, 0.15 to 0.45.

[0087] F / SiO2 molar ratio: 0 or more and 0.01 or less, greater than 0 and 0.01 or less, 0 or more and 0.005 or less.

[0088] In the crystallization process, the raw material composition is crystallized. The crystallization of the raw material composition may be carried out in the presence of a seed crystal to promote the crystallization of beta-zeolite. Examples of seed crystals include one or more selected from the group consisting of beta-zeolite, MFI-type zeolite, and FER-type zeolite, and also beta-zeolite. The ratio of the total mass of silicon (Si) and aluminum (Al) of the seed crystal converted to SiO2 and Al2O3, respectively, to the total mass of silicon (Si) and aluminum (Al) of the raw material composition (without seed crystals) converted to SiO2 and Al2O3, respectively (hereinafter also referred to as "seed crystal content") can be exemplified as 0 to 10% by mass, 0 to 5% by mass, or 0 to 3% by mass. An example of a method for crystallizing the raw material composition in the presence of a seed crystal is a method of crystallizing a mixture obtained by mixing the raw material composition and the seed crystal. The crystallization of the raw material composition may also be carried out without mixing the seed crystal with the raw material composition, i.e., with a seed crystal content of 0% by mass.

[0089] In the crystallization process, the crystallization of the raw material composition can be carried out by hydrothermal treatment of the raw material composition. Hydrothermal treatment can be performed by placing the raw material composition and seed crystals in a sealed pressure-resistant container and heating it. The following conditions are preferable for the hydrothermal treatment. Processing temperature: 130°C to 200°C, 140°C to 180°C Or between 150°C and 170°C. Processing time: 1 hour or more, 10 hours or more, 10 hours or more, 10 hours or more, or 24 hours or more. And, 7 days or less, 5 days or less, 3 days or less, or 2 days or less Processing state: Closed system, and at least one of the following: stirring state and / or standing state, or stirring state. Processing pressure: Self-generating pressure

[0090] For example, when crystallizing beta-zeolite with a SiO2 / Al2O3 molar ratio of 20 to 35, if the crystallization temperature is between 130 and 200°C, the beta-zeolite can be crystallized in two days or less.

[0091] The crystallized material obtained by the crystallization process may be washed. Washing of the crystallized material can be done by any method after crystallization. The method of washing the crystallized material is not particularly limited, but one method is to wash the crystallized material obtained as a solid phase after the crystallization process with pure water in an amount equal to 1 mass or more of the total amount of raw material composition excluding the seed crystal used for crystallization. For example, if the total amount of raw material composition is 60 g, washing with 60 g or more of pure water is sufficient, regardless of whether seed crystals are added or not. The washed crystallized material may be dried as needed. Drying can be done by any method that can physically remove moisture adsorbed on the crystallized material, for example, by treating the crystallized material in at least one of an oxidizing atmosphere and an inert atmosphere at 100°C to less than 300°C for 4 hours or more. A specific atmosphere for drying the crystallized material can be an air atmosphere.

[0092] The crystallized material obtained by the crystallization process may be subjected to at least one of the following treatments: washing and drying, before the metal cation removal process, but it must not be calcined. If the crystallized material is calcined before the metal cation removal process, the silanol strength ratio will increase, making it impossible to produce the beta-zeolite of this embodiment. In this embodiment, calcination refers to heat treatment at 300°C or higher.

[0093] (Metal cation removal process) The method for producing beta-zeolite in this embodiment includes a step of contacting the crystalline product obtained in the crystallization step with an ammonium-containing solution to obtain an acid-treated product (alkali metal removal step). This yields an acid-treated product from which alkali metal elements contained in the crystalline product have been removed.

[0094] The ammonium-containing solution used in the alkali metal removal process is ammonium (NH4 + A solution containing ammonium, and comprising at least an ammonium source and a solvent. The solvent contained in the ammonium-containing solution is ammonium (NH4 + Any medium capable of containing ammonium is acceptable, and examples include at least one of alcohol and water, with water being preferred. An ammonium-containing solution in which the solvent is water is also called an ammonium-containing aqueous solution.

[0095] Ammonium sources in ammonium-containing solutions include ammonia or ammonium salts. Ammonium salts include ammonium (NH4) + Any salt containing ammonium is acceptable, and examples include inorganic salts of ammonium, and more specifically, one or more selected from the group consisting of ammonium carbonate, ammonium chloride, and ammonium nitrate, and more specifically, ammonium chloride.

[0096] Ammonium concentration (NH4) of ammonium-containing solution +The concentration (NH4) is not particularly limited as long as the total alkali metal content of the beta-zeolite to be manufactured is 0.5% by mass or less, but examples include 1% by mass or more and 30% by mass or less, and preferably 5% by mass or more and 20% by mass or less. + The concentration is the ammonium (NH4) contained in the ammonium source contained in the ammonium-containing solution. + This is the concentration that can be calculated from the amount of ( ).

[0097] The amount of ammonium-containing solution to be brought into contact with the crystallized material is not particularly limited, as long as the total alkali metal content of the beta-zeolite produced is 0.5% by mass or less. However, in order to sufficiently remove alkali metals from the crystallized material, the ratio of the mass of the ammonium-containing solution to the dry mass of the crystallized material (hereinafter also referred to as the "NH4 / beta mass ratio") is preferably 10 or less, 8 or less, or 6 or less. The NH4 / beta mass ratio is preferably greater than 1 and 1.5 or greater, or 2 or greater. The combination of the upper and lower limits of the NH4 / beta mass ratio described above is arbitrary, but in order to sufficiently remove alkali metals from the crystallized material, the NH4 / beta mass ratio is preferably greater than 1 and 10 or less, more preferably 1.5 or greater and 8 or less, and even more preferably 2 or greater and 6 or less. In this embodiment, "dry mass of crystallized material" refers to the mass of the crystallized material after drying in an air atmosphere at 110°C for 4 hours.

[0098] The temperature of the ammonium-containing solution brought into contact with the crystallized material is not particularly limited, but examples include 5°C to 100°C, 10°C to 90°C, or 20°C to 80°C.

[0099] The method of contacting the crystallized material with the ammonium-containing solution is not particularly limited. Examples include a method of flowing the ammonium-containing solution through crystallized material molded into a predetermined shape (flow method) and a method of filling the inside of a reaction vessel containing crystallized material with the ammonium-containing solution (batch method).

[0100] The contact time between the crystalline product and the ammonium-containing solution is not particularly limited and should be set appropriately so that the total alkali metal content of the beta-zeolite being produced is 0.5% by mass or less.

[0101] The acid-treated product obtained in the alkali metal removal process may be subjected to at least one of the following treatments: washing and drying. The washing and drying conditions for the acid-treated product are the same as those for the washing and drying that can be performed in the crystallization process described above, so a detailed explanation is omitted.

[0102] The acid-treated product obtained by the alkali metal removal process preferably has a total alkali metal content of 0.5% by mass or less. By subjecting the acid-treated product with the above-mentioned total alkali metal cation content to the SDA removal process described later, it is easier to produce beta-zeolite with a total alkali metal content of 0.5% by mass or less and a lower silanol intensity ratio. The reason for this is not clear, but it is thought that when the total alkali metal cation content of the acid-treated product is 0.5% by mass or less, the silanol defects that occur in the beta-zeolite can easily condense with the heat of combustion without being inhibited by the alkali metal cations.

[0103] (SDA removal process) The method for producing beta-zeolite according to this embodiment includes a step of calcining the acid-treated product obtained in the alkali metal removal step at 400°C to 800°C in an atmosphere containing less than 5% by volume of water vapor (SDA removal step). This removes the SDA contained in the acid-treated product, yielding the beta-zeolite according to this embodiment. In the SDA removal step, it is not necessary to remove all of the SDA contained in the acid-treated product; it is sufficient to remove at least some of the SDA contained in the acid-treated product, as long as the SDA content of the resulting beta-zeolite is 4.0% by mass or less.

[0104] In the SDA removal process, the atmosphere used to calcine the acid-treated material (hereinafter also referred to as the "calcination atmosphere") contains less than 5% by volume of water vapor. By keeping the water vapor concentration of the calcination atmosphere below 5% by volume, SDA can be removed without significantly affecting the aluminum in the skeletal structure, which is the catalytic active site. On the other hand, if the water vapor concentration of the calcination atmosphere is 5% by volume or more, the aluminum in the skeletal structure, which is the catalytic active site, will detach, as in the steam treatment described in Non-Patent Literature 1, and the catalytic activity of the resulting beta-zeolite will decrease. The water vapor concentration of the calcination atmosphere should be less than 5% by volume, but it is preferable to have a concentration of 3% by volume or less, more preferably 2% by volume or less, and even more preferably less than 1% by volume, in that the aluminum in the skeletal structure is less likely to detach. The lower limit of the water vapor concentration is not particularly limited, but it should be 0% by volume or more. In this embodiment, assuming an ideal gas, the volume fraction of water in the calcination atmosphere is considered to be the water vapor concentration of the calcination atmosphere. In this embodiment, steam treatment refers to a process of firing zeolite in an atmosphere containing 5% or more by volume of water vapor.

[0105] The firing atmosphere can be any atmosphere in which SDA can be removed from the acid-treated material, and can be at least one of an oxidizing atmosphere, an inert atmosphere, and a reducing atmosphere, with an oxidizing atmosphere and, more preferably, an atmospheric atmosphere.

[0106] In the SDA removal process, the calcination of the acid-treated material can be carried out at a temperature of 400°C to 800°C, but it is preferable to use a temperature of 550°C to 750°C, as this is expected to further improve the hydrothermal durability of the resulting beta-zeolite.

[0107] In the SDA removal process, the calcination of the acid-treated material may be carried out at 400°C to 800°C in an atmosphere with less than 5% by volume of water vapor. However, in order to further improve the hydrothermal durability of the resulting beta-zeolite, it is preferable to carry out the calcination in one or more atmospheres selected from the group consisting of an oxidizing atmosphere, an inert atmosphere, and a reducing atmosphere, at 400°C to 800°C in an atmosphere with less than 5% by volume of water vapor, and more preferably at 550°C to 750°C in an atmospheric atmosphere with less than 5% by volume of water vapor.

[0108] In the SDA removal process, the calcination time of the acid-treated material can be adjusted as appropriate so that the SDA content of the beta-zeolite produced is 4.0% by mass or less, and is not particularly limited, but an example is that it is between 1 hour and 5 hours.

[0109] According to the manufacturing method described above, the beta-zeolite of this embodiment, which has excellent catalytic activity and hydrothermal durability, can be produced. Although the reason for this is not clear, in the manufacturing method described above, after subjecting the crystallized product containing SDA to the alkali metal removal step, the acid-treated product from which the alkali metals have been removed is subjected to the SDA removal step. As a result, the aluminum in the crystallized product (beta-zeolite) is protected by SDA, and the ammonium-containing solution for removing alkali metals can come into contact with the crystallized product (beta-zeolite), so it is presumed that the detachment of aluminum from the skeletal structure due to contact with the ammonium-containing solution (hereinafter also referred to as "dealuminization") is less likely to occur. Furthermore, in the manufacturing method described above, since the calcination of the crystallized product is performed in the SDA removal step after the alkali metal removal step, it is presumed that the condensation of silanol defects due to calcination proceeds without being inhibited by alkali metal cations. As a result, it is possible to reduce silanol defects while maintaining excellent catalytic activity, and it is thought that the beta-zeolite of this embodiment, which has excellent catalytic activity and hydrothermal durability, can be produced.

[0110] On the other hand, as in Patent Document 1, if the crystalline material (beta zeolite) is subjected to the SDA removal process before the alkali metal removal process, it is presumed that dealuminulation is more likely to occur due to contact with the ammonium-containing solution in the alkali metal removal process, resulting in a decrease in the catalytic activity of the resulting beta zeolite or the creation of new silanol defects. In addition, as in Patent Document 1, if the crystalline material (beta zeolite) is subjected to the SDA removal process before the alkali metal removal process, it is presumed that the condensation of silanol defects due to calcination is inhibited by alkali metal cations. As a result, in the manufacturing method in which the crystalline material (beta zeolite) is subjected to the SDA removal process before the alkali metal removal process, as in Patent Document 1, the decrease in SiO2 / Al2O3 molar ratio (the increase in aluminum) becomes more pronounced, and it is considered that low-silica beta zeolite that balances catalytic activity and hydrothermal durability cannot be manufactured.

[0111] (Active metal containing process) Next, a method for producing the beta-zeolite of this embodiment containing an activated metal element (activated metal-containing beta-zeolite of this embodiment) will be described. The beta-zeolite of this embodiment is expected to have higher catalytic activity due to the inclusion of an activated metal element. The activated metal-containing beta-zeolite of this embodiment can be produced by a manufacturing method that includes a step of contacting the beta-zeolite of this embodiment with an activated metal source (hereinafter also referred to as the "activated metal-containing step").

[0112] In the activated metal incorporation process, the beta-zeolite of this embodiment is brought into contact with an activated metal source to incorporate an arbitrary activated metal element into the beta-zeolite of this embodiment. In the activated metal incorporation process, the contact between the beta-zeolite and the activated metal source can be carried out in a manner that allows the activated metal element to be incorporated into the beta-zeolite. For example, one or more methods selected from the group consisting of ion exchange, impregnation and loading, evaporation to dryness, precipitation and loading, and physical mixing can be used. In terms of ease of incorporating the activated metal element into the beta-zeolite, it is preferable to use the impregnation and loading method for contact between the beta-zeolite and the activated metal source. An example of the impregnation and loading method is a method in which the beta-zeolite of this embodiment is brought into contact with a solution containing the activated metal source (hereinafter also referred to as the "activated metal solution").

[0113] An activated metal solution contains at least an activated metal source and a solvent. The activated metal source in the activated metal solution is at least one of a salt or compound containing an activated metal element, and examples include one or more selected from the group of nitrates, sulfates, acetates, chlorides, complex salts, oxides and complex oxides containing an activated metal element, and preferably one or more selected from the group of nitrates, sulfates and chlorides containing an activated metal element.

[0114] The solvent contained in the activated metal solution may be any solvent in which at least one of the salts and compounds containing the activated metal element is dissolved. Water is an example, and at least one of pure water and deionized water is preferred.

[0115] The contact conditions between the beta zeolite and the activated metal solution in this embodiment are not particularly limited and can be those used in conventionally known impregnation and support methods.

[0116] By contacting the beta zeolite of this embodiment with an activated metal solution, the activated metal element is incorporated into the beta zeolite of this embodiment, and the activated metal-containing beta zeolite of this embodiment can be produced. The beta zeolite of this embodiment that has been in contact with the activated metal solution may be subjected to at least one of the following treatments: drying and calcination, before becoming the activated metal-containing beta zeolite of this embodiment. The drying and calcination treatments can be performed using any conditions that are used in conventionally known impregnation and loading methods, and are not particularly limited. [Examples]

[0117] The present disclosure will be described below with reference to examples. However, the present disclosure is not limited to these examples.

[0118] (Zeolite structure) The XRD pattern of the sample was measured using a standard powder X-ray diffractometer (instrument name: UltimaIV, manufactured by Rigaku Corporation). The measurement conditions were as follows: Acceleration current / voltage: 40mA / 40kV Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Continuous scan Scanning conditions: 40° / min Measurement range: 2θ = 3° to 43° Divergence vertical limiting slit: 10mm Divergence / Induction Slit: 1° Light-receiving slit: open Solar light receiving slit: 5° Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter

[0119] The obtained XRD patterns were analyzed using general analysis software (SmartLab Studio II, Rigaku Corporation) under the following conditions. Furthermore, the zeolite structure of the sample was identified by comparing the XRD patterns with a reference pattern. Crystalline XRD peaks were defined as peaks where the peak top 2θ was identified and detected in the aforementioned analysis. Fitting conditions: Automatic, background refinement Dispersive pseudo-Voigt function (peak shape) Background removal method: Fitting method Kα2 removal method: Kα1 / Kα2 ratio=0.497 Smoothing method: B-Spline curve Smoothing conditions: Second derivative method, σ cut value = 3, χ threshold = 1.5

[0120] (composition analysis) The composition of the sample was analyzed using a general inductively coupled plasma emission spectrometer (instrument name: OPTIMA7300DV, manufactured by PERKIN ELMER). The sample was dissolved in a mixed solution of hydrofluoric acid and nitric acid to prepare the measurement solution. The composition of the sample was analyzed using the obtained measurement solution. In addition, the sodium content (hereinafter also referred to as "Na2O content") converted to Na2O using the following formula (2'') was determined, and the potassium content (hereinafter also referred to as "K2O content") converted to K2O using the following formula (2'') was determined. In the examples and comparative examples shown below, the sum of the Na2O content and K2O content corresponds to the total alkali metal content obtained from the above formula (2). Na2O content={(Na2O) / (SiO2+Al2O3+Na2O+K2O)}×100 (2'') K2O content={(K2O) / (SiO2+Al2O3+Na2O+K2O)}×100 (2''')

[0121] (Average crystal diameter) SEM images of the sample were obtained using a standard scanning electron microscope (JSM-IT200, manufactured by JEOL Ltd.). The SEM observation was performed under the following conditions. The average crystal diameter was calculated by measuring the maximum Ferret diameter of the smallest independently observed particles and taking the arithmetic mean of 50 ± 5 particles. However, secondary aggregates formed by the aggregation of primary particles were not used in the calculation of the average crystal diameter as they were not considered independent particles. Acceleration voltage: 6kV Magnification: 10,000±5,000x

[0122] (Frequency-Volume-Particle Size Distribution) For frequency, volume, and particle size distribution analysis, silica-alumina was weighed to a weight of 5 g, diluted with pure water to a total volume of 50 g, and a measurement slurry was prepared. The measurement slurry was pretreated using an ultrasonic dispersion device (device name: ultrasonic homogenizer US-150E, manufactured by Nippon Seiki Seisakusho Co., Ltd.) under the following conditions. The measurement slurry after pretreatment was measured using a general laser diffraction / scattering particle size distribution analyzer (device name: Microtrac MT3300EXII, manufactured by Microtrac-Bell Co., Ltd.) under the following conditions. Pretreatment conditions TIP SELECT: 20Φ LEVEL: 5 Processing time: 2 minutes Frequency volume distribution measurement conditions Measurement range: 0.02~2000μm Particle refractive index: 1.66 Particle permeability: permeation Particle shape: non-spherical Solvent refractive index: 1.333

[0123] (Total acid point amount) The total acid content was measured using the NH3-TPD method. The total acid content of the sample was measured using a general temperature-controlled desorption analyzer (instrument name: BELCATII, manufactured by MicrotracBEL). The sample used for measurement was zeolite (0.05 g) pre-treated at 500°C for 1 hour in an atmosphere with helium gas flowing at 50 ml / min.

[0124] <NH3-TPD Measurement> The measurement of the total acid site amount by the NH3-TPD method was carried out under the following conditions. For the measurement sample after pretreatment, a mixed gas containing 1% by volume of ammonia and 99% by volume of helium gas was passed through the measurement sample at 100 °C to saturate the measurement sample with ammonia. After passing the mixed gas for 30 minutes, the mixed gas was replaced with helium gas, and helium gas was passed for 15 minutes at 100 °C to remove residual ammonia in the atmosphere. After removing the residual ammonia, the temperature was raised from 100 °C to 710 °C at a heating rate of 10 °C / min under a helium flow rate of 30 mL / min. Thereby, the ammonia adsorbed on the measurement sample was desorbed from the measurement sample. The ammonia desorbed from the measurement sample was continuously quantified by a gas chromatograph equipped with a thermal conductivity detector (TCD), and thereby an ammonia desorption spectrum (TPD spectrum) was obtained.

[0125] The obtained TPD spectrum was analyzed by separating the spectrum showing ammonia desorbed from zeolite (measurement sample) (ammonia desorption spectrum) using general analysis software (software name: Chem Master, Microtrac for Windows ver1.4.9, manufactured by MicrotracBEL). Specifically, with 100 °C as the base start in the temperature rising process from 100 °C to 710 °C and 700 °C as the base end in the temperature rising process from 100 °C to 710 °C, the ammonia desorption section in the TPD spectrum was subjected to baseline processing. Among the TPD spectra subjected to baseline processing, the spectrum in the ammonia desorption section (that is, the range of 100 °C or higher and 700 °C or lower in the temperature rising process) was taken as the ammonia desorption spectrum. The area (integral value) of the ammonia desorption spectrum was determined and taken as the ammonia desorption amount. The total acid site amount of the measurement sample was obtained by dividing the ammonia desorption amount (mmol) by the mass (g) of the measurement sample used in the measurement.

[0126] (Silanol intensity ratio) The silanol intensity ratio was determined from the IR spectrum obtained by FT-IR using a general FT-IR measuring instrument (instrument name: Jasco FT / IR-6100, manufactured by JASCO Corporation). The FT-IR used to measure the IR spectrum was prepared by forming a disc (0.01 g / cm²) on a heating unit (instrument name: IN-SITU cell for standard optical path spectroscopy 2000-1431, manufactured by Makuhari Chemical Glass Co., Ltd.) using a press machine. 2 The sample was inserted and pretreated under vacuum, at 450°C (sample temperature), for 1 hour, before being carried out under the following conditions. Measurement method: heating transmission method Sample size: 0.01g Temperature measurement: Continuous scan Measurement temperature: 200℃ under vacuum (product temperature) Measurement range: 350~4000cm -1 Resolution: 2.0cm -1 Total number of times: 128 Zero Filling: ON Detector: TGS (Triglycine sulfate)

[0127] The obtained IR spectra were processed using common analysis software (Spectra Manager Version 2, Version 2.15.11, manufactured by JASCO Corporation). Specifically, the base start was set to 1580 cm⁻¹. -1 , base end 2100cm -1 , and base start at 3000cm -1 , base end 3800cm -1 These ranges were then baseline-corrected. Subsequently, from the baseline-processed IR spectrum, 1860 (±10) cm⁻¹ was obtained. -1 Among the peaks with peak tops within the range, identify peak P1, which has the highest peak top height intensity, and also identify the peak with a peak top height of 3735 (±10) cm. -1 Among the peaks with peak tops within the specified range, peak P2, which had the highest peak top intensity, was identified. From the height intensity HI1 of the identified peak P1 and the height intensity HI2 of peak P2, the silanol intensity ratio was calculated using the above formula (1).

[0128] (SDA content) The SDA content was determined by dividing the mass of SDA contained in the sample (SDA mass) by the mass of the sample (Beta mass) and converting this to a percentage. The dry mass of the sample (Beta mass) was obtained by drying the sample in an air atmosphere at 110°C for 4 hours. The mass of SDA contained in the sample (SDA mass) was obtained by measuring 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℃

[0129] (Proton type) A zeolite slurry with a solid content of 10% by mass was obtained by mixing 2g of the sample with 18g of water and shaking for 1 minute. The pH of the zeolite slurry at a temperature of 25°C (slurry pH) was measured using a general pH meter (instrument name: F-72S, manufactured by HORIBA). The cation type of the sample (zeolite) was determined to be proton type when the measured slurry pH was less than 7 and the total alkali metal content was 0.5% by mass or less. Conversely, the cation type of the sample (zeolite) was determined to be alkaline type when the total alkali metal content exceeded 0.5% by mass.

[0130] Example 1 A raw material composition having the following molar composition was obtained by mixing a 35% by mass aqueous solution of tetraethylammonium hydroxide (TEAOH), a 48% by mass aqueous solution of potassium hydroxide, pure water, and amorphous aluminosilicate (SiO2 / Al2O3 molar ratio: 23.0) in a total amount of 60 g. SiO2 / Al2O3 molar ratio: 23.0 TEA + / SiO2 molar ratio: 0.10 K / SiO2 molar ratio: 0.10 K / M molar ratio: 1.00 H2O / SiO2 molar ratio: 11 OH / SiO2 molar ratio: 0.20 F / SiO2 molar ratio: 0

[0131] To the obtained raw material composition, beta-zeolite (HSZ-930NHA, manufactured by Tosoh Corporation, SiO2 / Al2O3 ratio: 28.0) was mixed as a seed crystal so that the seed crystal content was 1.5% by mass. Then, the raw material composition mixed with the seed crystal was filled into an 80 ml sealed container and subjected to hydrothermal treatment at 55 rpm and 150°C for 48 hours under self-sharpening pressure to obtain crystallized material. The obtained crystallized material was subjected to solid-liquid separation, washed with 10 times the mass of the raw material composition (excluding the seed crystal) in pure water, and then dried in an air atmosphere at 110°C for 4 hours to obtain dried crystallized material (hereinafter also referred to as "dried material").

[0132] The resulting dried product had an SiO2 / Al2O3 molar ratio of 21.3, a Na2O content below the detection limit, and a K2O content of 1.15% by mass.

[0133] Next, the dried material was dispersed in pure water so that its content was 20% by mass, and then filtered by suction using a funnel to form a cake. A 20% by mass aqueous solution of ammonium chloride, five times the mass of the dried material, was passed through this cake at 60°C to bring the dried material into contact with the aqueous solution of ammonium chloride and obtain an acid-treated product. The obtained acid-treated product was washed with pure water ten times the mass of the dried material, and then dried in the air at 110°C for 4 hours. The dried acid-treated product was calcined at 700°C for 4 hours in an atmosphere with 0.2% by volume of water vapor to obtain the beta-zeolite of this example.

[0134] The beta-zeolite in question had an SiO2 / Al2O3 molar ratio of 21.3, a Na2O content below the detection limit, a K2O content of 0.13 mass%, an average crystal diameter of 0.31 μm, a full width at half maximum of the XRD main peak of 2θ = 0.398°, a total acid content of 0.97 mmol / g, a silanol intensity ratio of 1.29, an SDA content of 0.95 mass%, and a proton-type cation, and exhibited the XRD peaks shown in Table 3 below. [Table 3]

[0135] Example 2 A raw material composition having the following molar composition was obtained by mixing a 35% by mass TEAOH aqueous solution, a 48% by mass potassium hydroxide aqueous solution, pure water, and amorphous aluminosilicate (SiO2 / Al2O3 molar ratio: 27.0) in a total amount of 60 g. An acid-treated product was obtained by drying in the same manner as in Example 1, except that this raw material composition was used instead of the raw material composition used in Example 1. SiO2 / Al2O3 molar ratio: 27.0 TEA + / SiO2 molar ratio: 0.12 K / SiO2 molar ratio: 0.10 K / M molar ratio: 1.00 H2O / SiO2 molar ratio: 11 OH / SiO2 molar ratio: 0.22 F / SiO2 molar ratio: 0

[0136] In this example, the dried crystalline product had an SiO2 / Al2O3 molar ratio of 25.9, a Na2O content below the detection limit, and a K2O content of 0.54% by mass.

[0137] The resulting acid-treated material (dried acid-treated material) was calcined at 600°C for 4 hours in an atmospheric environment containing 1% by volume of water vapor to obtain the beta-zeolite of this example.

[0138] The beta-zeolite in question had an SiO2 / Al2O3 molar ratio of 26.3, a Na2O content below the detection limit, a K2O content of 0.12 mass%, an average crystal diameter of 0.28 μm, a full width at half maximum of the XRD main peak of 2θ = 0.355°, a total acid content of 1.30 mmol / g, a silanol intensity ratio of 1.74, an SDA content of 1.34 mass%, and a proton-type cation, and exhibited the XRD peaks shown in Table 4 below. [Table 4]

[0139] Comparative Example 1 Beta zeolite was obtained based on a known method for producing beta described by the IZA (Internal Zeolite Association) (http: / / www.iza-online.org / synthesis / ). Specifically, a raw material composition having the following molar composition was obtained by mixing a 48% by mass aqueous sodium hydroxide solution, sodium aluminate, sodium chloride, potassium chloride, a 35% by mass aqueous TEAOH solution, fumed silica, and pure water, with a total amount of 60 g. SiO2 / Al2O3 molar ratio: 50.0 TEA + / SiO2 molar ratio: 0.50 Na / SiO2 molar ratio: 0.079 K / SiO2 molar ratio: 0.040 K / M molar ratio: 0.34 H2O / SiO2 molar ratio: 15 OH / SiO2 molar ratio: 0.56 F / SiO2 molar ratio: 0

[0140] The obtained raw material composition was filled into a sealed container and subjected to hydrothermal treatment at 55 rpm and 135°C for 36 hours to obtain crystals. The obtained crystals were subjected to solid-liquid separation, washed with 10 times the mass of pure water relative to the total amount of the raw material composition, and dried overnight in an air atmosphere at 110°C to obtain dried crystals (dried product).

[0141] The resulting dried product had an SiO2 / Al2O3 molar ratio of 27.6, a Na2O content of 0.18% by mass, and a K2O content of 0.17% by mass.

[0142] The dried material was calcined at 600°C for 4 hours in an atmosphere containing 1% by volume of water vapor to obtain a calcined product.

[0143] The calcined material was dispersed in pure water to a content of 20% by mass, and then filtered by suction using a funnel to form a cake. A 20% by mass aqueous solution of ammonium chloride, five times the mass of the calcined material, was passed through this cake at 60°C, and the dried product was brought into contact with the aqueous solution of ammonium chloride to obtain an acid-treated product. The obtained acid-treated product was washed with 10 times the mass of pure water, dried overnight at 110°C, and then calcined at 550°C for 4 hours in an atmosphere with 1% by volume of water vapor to obtain the beta-zeolite of this comparative example.

[0144] The obtained beta-zeolite was a beta-zeolite with an SiO2 / Al2O3 molar ratio of 31.7, Na2O content below the detection limit, K2O content below the detection limit, average crystal diameter of 0.18 μm, XRD main peak full width at half maximum of 2θ = 0.598°, total acid content of 0.95 mmol / g, silanol intensity ratio of 3.77, SDA content of 3.20 mass%, and a cation type of proton type, and exhibited the XRD peaks shown in Table 5 below. [Table 5]

[0145] Comparative Example 2 The beta-zeolite of this comparative example was obtained based on the method for producing beta-zeolite described in Example 3 of Japanese Patent No. 5082361. Specifically, a 35% by mass aqueous solution of TEAOH, a 48% by mass aqueous solution of potassium hydroxide, pure water, and amorphous aluminosilicate (SiO2 / Al2O3 molar ratio: 28.0) were mixed in a total amount of 60 g to obtain a raw material composition having the following molar composition. SiO2 / Al2O3 molar ratio: 28.0 TEA + / SiO2 molar ratio: 0.30 K / SiO2 molar ratio: 0.10 K / M molar ratio: 1.00 H2O / SiO2 molar ratio: 9.9 OH / SiO2 molar ratio: 0.40 F / SiO2 molar ratio: 0

[0146] To the obtained raw material composition, beta-zeolite (HSZ-930NHA, manufactured by Tosoh Corporation, SiO2 / Al2O3 molar ratio: 28.0) was mixed as a seed crystal so that the seed crystal content was 0.36% by mass. Then, the raw material composition mixed with the seed crystal was filled into an 80 ml sealed container and subjected to hydrothermal treatment at 55 rpm and 150°C for 88 hours to obtain crystallized material. The obtained crystallized material was subjected to solid-liquid separation, washed with 10 times the mass of pure water relative to the total amount of the raw material composition, and dried overnight in an air atmosphere at 110°C to obtain dried crystallized material (dried product).

[0147] The resulting dried product had an SiO2 / Al2O3 molar ratio of 22.7, a Na2O content below the detection limit, and a K2O content of 0.50% by mass.

[0148] The dried material was calcined at 600°C for 4 hours in an atmospheric atmosphere containing 1% by volume of water vapor to obtain a calcined product.

[0149] The calcined material was dispersed in pure water to a content of 20% by mass, and then filtered by suction using a funnel to form a cake. A 20% by mass aqueous solution of ammonium nitrate, five times the mass of the calcined material, was passed through this cake at 25°C, and the dried product was brought into contact with the aqueous solution of ammonium nitrate to obtain an acid-treated product. The obtained acid-treated product was washed with pure water, dried overnight in an air atmosphere at 110°C, and then calcined at 550°C for 4 hours in an air atmosphere with 1% by volume of water vapor to obtain the beta-zeolite of this comparative example.

[0150] The beta-zeolite in question had an SiO2 / Al2O3 molar ratio of 26.7, a Na2O content below the detection limit, a K2O content below the detection limit, an average crystal diameter of 0.49 μm, a full width at half maximum of the XRD main peak of 2θ = 0.501°, a total acid content of 1.21 mmol / g, a silanol intensity ratio of 2.37, an SDA content of 1.41 mass%, and a proton-type cation, and exhibited the XRD peaks shown in Table 6 below. [Table 6]

[0151] Comparative Example 3 The beta-zeolite of this comparative example was obtained based on the method for producing beta-zeolite described in Example 4 of Japanese Patent No. 5082361. Specifically, a 35% by mass aqueous TEAOH solution, a 48% by mass aqueous potassium hydroxide solution, pure water, and amorphous aluminosilicate (SiO2 / Al2O3 molar ratio: 28.0) were mixed in a total amount of 60 g to obtain a raw material composition having the following molar composition. The beta-zeolite of this comparative example was obtained in the same manner as in Comparative Example 2, except that this raw material composition was used instead of the raw material composition used in Comparative Example 2. SiO2 / Al2O3 molar ratio: 28.0 TEA + / SiO2 molar ratio: 0.14 K / SiO2 molar ratio: 0.05 K / M molar ratio: 1.00 H2O / SiO2 molar ratio: 9.9 OH / SiO2 molar ratio: 0.19 F / SiO2 molar ratio: 0

[0152] The beta-zeolite in question had an SiO2 / Al2O3 molar ratio of 31.9, a Na2O content below the detection limit, a K2O content below the detection limit, an average crystal diameter of 0.40 μm, a full width at half maximum of the XRD main peak of 0.478°, a total acid content of 1.02 mmol / g, a silanol intensity ratio of 2.54, an SDA content of 1.52 mass%, and a proton-type cation, and exhibited the XRD peaks shown in Table 7 below. [Table 7]

[0153] Comparative Example 4 A dried acid-treated product was obtained in the same manner as in Example 1. The obtained acid-treated product was calcined (steam-treated) at 700°C for 1 hour in a mixed gas atmosphere consisting of 5% by volume of water vapor and 95% by volume of air to obtain the beta-zeolite of this comparative example.

[0154] The beta-zeolite in question had an SiO2 / Al2O3 molar ratio of 21.3, a Na2O content below the detection limit, a K2O content of 0.13 mass%, an average crystal diameter of 0.28 μm, a full width at half maximum of the XRD main peak of 2θ = 0.427°, a total acid content of 0.70 mmol / g, a silanol intensity ratio of 1.94, an SDA content of 1.90 mass%, and a proton-type cation, and exhibited the XRD pattern shown in Table 8 below. [Table 8]

[0155] Comparative Example 5 Based on the method for producing CHA-type zeolite described in Example 2 of Japanese Patent No. 6977314, the CHA-type zeolite of this comparative example was obtained. Specifically, a raw material composition having the following molar composition was obtained by mixing a 50% by mass aqueous solution of dimethylethylcyclohexylammonium bromide (DMECHABr), a 35% by mass aqueous solution of dimethylethylcyclohexylammonium hydroxide (DMECHAOH), a 48% by mass aqueous solution of potassium hydroxide, a 48% by mass aqueous solution of potassium hydroxide, pure water, and amorphous aluminosilicate (SiO2 / Al2O3 molar ratio: 24.6). SiO2 / Al2O3 molar ratio: 24.6 DMECHABr / SiO2 molar ratio: 0.04 DMECHAOH / SiO2 molar ratio: 0.04 Na / SiO2 molar ratio: 0.04 K / SiO2 molar ratio: 0.08 K / M molar ratio: 0.67 H2O / SiO2 molar ratio: 15.0 OH / SiO2 molar ratio: 0.16

[0156] The obtained raw material composition was filled into an 80 ml sealed container and subjected to hydrothermal treatment at 55 rpm and 150°C for 48 hours to obtain crystals. The obtained crystals were subjected to solid-liquid separation, washed with 10 times the mass of pure water relative to the total amount of the raw material composition, and dried overnight in an air atmosphere at 110°C to obtain dried crystals (dried product).

[0157] The resulting dried product had an SiO2 / Al2O3 molar ratio of 24.0, a Na2O content of 0.23% by mass, and a K2O content of 1.19% by mass.

[0158] The dried material was placed inside a reaction vessel, and a 20% by mass aqueous solution of ammonium chloride, five times the mass of the dried material, was added at 60°C to bring the dried material into contact with the ammonium chloride aqueous solution and obtain an acid-treated product. The obtained acid-treated product was washed with 10 times the mass of the dried material in pure water and dried in air at 110°C for 4 hours. The dried acid-treated product was calcined in an atmosphere with 1% by volume of water vapor at 600°C for 4 hours to obtain the CHA-type zeolite of this comparative example.

[0159] The CHA-type zeolite had an SiO2 / Al2O3 molar ratio of 24.6, a Na2O content of 0.21% by mass, a K2O content of 0.94% by mass, and was an alkali-type CHA-type zeolite. Therefore, even if an alkali metal removal process was performed before the SDA removal process, alkali metal cations could not be efficiently removed from the CHA-type zeolite.

[0160] Comparative Example 6 A crystalline product was obtained based on the method for producing beta-zeolite described in Example 1 of Japanese Patent No. 5082361. Specifically, a raw material composition having the following molar composition was obtained by mixing a 50% by mass aqueous solution of tetraethylammonium fluoride, a 48% by mass aqueous solution of sodium hydroxide, pure water, and amorphous aluminosilicate (SiO2 / Al2O3 molar ratio: 23.0) in a total amount of 60 g. SiO2 / Al2O3 molar ratio: 23.0 TEA + SiO2 molar ratio: 0.67 Na / SiO2 molar ratio: 0.10 K / M molar ratio: 0.00 H2O / SiO2 molar ratio: 12.0 OH / SiO2 molar ratio: 0.10 F / SiO2 molar ratio: 0.67

[0161] To the obtained raw material composition, beta-zeolite (HSZ-940NHA, manufactured by Tosoh Corporation, SiO2 / Al2O3 molar ratio: 40.0) was mixed as a seed crystal so that the seed crystal content was 1.0 mass%. Then, the raw material composition mixed with the seed crystal was filled into an 80 ml sealed container and subjected to hydrothermal treatment at 55 rpm and 155°C for 72 hours to obtain crystallized material. The obtained crystallized material was subjected to solid-liquid separation, washed with 10 times the mass of pure water relative to the total amount of the raw material composition, and dried overnight in an air atmosphere at 110°C to obtain dried crystallized material (dried product).

[0162] The resulting dried product had an SiO2 / Al2O3 molar ratio of 26.0, a Na2O content of 1.80% by mass, and a K2O content below the detection limit.

[0163] Next, the dried material was dispersed in pure water to a content of 20% by mass, and then filtered by suction using a funnel to form a cake. A 20% by mass aqueous solution of ammonium chloride, five times the mass of the dried material, was passed through this cake at 60°C, bringing the dried material into contact with the aqueous solution of ammonium chloride to obtain an acid-treated product. The obtained acid-treated product was washed with pure water ten times the mass of the dried material, and then dried in the air at 110°C for 4 hours. The dried acid-treated product was calcined in an atmosphere with 1% by volume of water vapor at 600°C for 4 hours to obtain the beta-zeolite of this comparative example.

[0164] The beta-zeolite in question had an SiO2 / Al2O3 molar ratio of 28.0, a Na2O content of 0.90 mass%, a K2O content below the detection limit, an average crystal diameter of 0.73 μm, a full width at half maximum of the XRD main peak of 2θ = 0.279°, a total acid content of 0.84 mmol / g, a silanol intensity ratio of 1.78, an SDA content of 1.34 mass%, and an alkaline cation type, and exhibited the XRD peaks shown in Table 9 below. [Table 9]

[0165] Comparative Example 7 The raw material composition was crystallized in the same manner as in Comparative Example 6 to obtain a crystalline product. The beta-zeolite of this comparative example was obtained in the same manner as in Comparative Example 1, except that the crystalline product obtained was used instead of the crystalline product used in Comparative Example 1.

[0166] The beta-zeolite in question had an SiO2 / Al2O3 molar ratio of 36.8, a Na2O content of 0.17 mass%, a K2O content below the detection limit, an average crystal diameter of 0.73 μm, a full width at half maximum of the XRD main peak of 2θ = 0.279°, a total acid content of 0.88 mmol / g, a silanol intensity ratio of 2.00, an SDA content of 1.58 mass%, and a proton-type cation, and exhibited the XRD peaks shown in Table 10 below. [Table 10]

[0167] Comparative Example 8 Beta-zeolite was obtained based on Example 4 of Japanese Patent Publication No. 2012-136409 (JP 2012-136409 A). Specifically, a raw material composition having the following molar composition was obtained by mixing a 35% by mass aqueous solution of TEAOH, a 48% by mass aqueous solution of sodium hydroxide, pure water, and amorphous aluminosilicate (SiO2 / Al2O3 molar ratio: 28.0) in a total amount of 60 g. SiO2 / Al2O3 molar ratio: 28.0 TEA + / SiO2 molar ratio: 0.13 Na / SiO2 molar ratio: 0.10 K / M molar ratio: 0.00 H2O / SiO2 molar ratio: 10.0 OH / SiO2 molar ratio: 0.23

[0168] Furthermore, a tetraethylammonium solution (hereinafter also referred to as "TEA solution") was prepared as a seed crystal. Specifically, precipitated silica, aluminum hydroxide, a 35% by mass TEAOH aqueous solution, and pure water were mixed in a total amount of 60 g to obtain a seed crystal raw material composition having the following molar composition. SiO2 / Al2O3 molar ratio: 50.0 TEA + / SiO2 molar ratio: 0.40 H2O / SiO2 molar ratio: 6.5 OH / SiO2 molar ratio: 0.40

[0169] The obtained seed crystal raw material composition was filled into an 80 ml sealed container and subjected to hydrothermal treatment at 55 rpm and 150°C for 4 hours to obtain a TEA solution. Laser diffraction revealed that the TEA solution was a highly transparent, viscous brown liquid containing solids with a peak at 0.15 μm in the frequency-volume-particle-size distribution curve.

[0170] The TEA solution was mixed with the raw material composition as a seed crystal so that the silica-alumina solid content in the TEA solution was 5.0% by mass relative to the raw material composition. This mixture was then packed into an 80 ml sealed container and subjected to hydrothermal treatment at 55 rpm and 150°C for 50 hours to obtain crystals. The obtained crystals were subjected to solid-liquid separation, washed with 10 times the mass of the raw material composition (including the seed crystal) in pure water, and then dried in an air atmosphere at 110°C for 4 hours to obtain a dried product.

[0171] The resulting dried product had an SiO2 / Al2O3 molar ratio of 25.8, a Na2O content of 0.38% by mass, and a K2O content below the detection limit.

[0172] Next, the dried material was dispersed in pure water so that its content was 20% by mass, and then filtered by suction using a funnel to form a cake. A 10% by mass aqueous solution of ammonium chloride, 10 times the mass of the dried material, was passed through this cake at 60°C to obtain an acid-treated product. The obtained acid-treated product was washed with pure water 10 times the mass of the dried material, and then dried in the air at 110°C for 4 hours to obtain an acid-treated product. This was further calcined in an atmosphere with 1% by volume of water vapor at 600°C for 4 hours to obtain the beta-zeolite of this comparative example.

[0173] The beta-zeolite in question had an SiO2 / Al2O3 molar ratio of 25.9, a Na2O content of 0.03 mass%, a K2O content below the detection limit, an average crystal diameter of 0.09 μm, a full width at half maximum of the XRD main peak of 2θ = 0.504°, a total acid content of 1.16 mmol / g, a silanol intensity ratio of 2.95, an SDA content of 2.08 mass%, and a proton-type cation, and exhibited the XRD peaks shown in Table 11 below. [Table 11]

[0174] Comparative Example 9 The raw material composition was crystallized in the same manner as in Example 1 to obtain crystalline material. The obtained crystalline material was subjected to solid-liquid separation, and a dried product was obtained at 110°C. Based on a known document (Microporous and Mesoporous Materials 48 (2001) 57-64), 1.0 g of the obtained dried product was dispersed in 500 ml of 50 vol% aqueous acetic acid solution in a 1 L round-bottom flask to prepare a zeolite dispersion slurry, which was then acid-treated by stirring at 80°C for 24 hours to obtain an acid-treated product.

[0175] The acid-treated material was separated into solid and liquid from the zeolite dispersion slurry after acid treatment, and washed with 10 times the mass of pure water used for the dried material. The washed acid-treated material was dried in an air atmosphere at 110°C for 4 hours to obtain a dried acid-treated material. The dried acid-treated material was calcined in an air atmosphere with 1% by volume of water vapor at 600°C for 4 hours to obtain the beta-zeolite of this comparative example.

[0176] The beta-zeolite in question had an SiO2 / Al2O3 molar ratio of 22.0, a Na2O content below the detection limit, a K2O content of 0.08 mass%, an average crystal diameter of 0.31 μm, a full width at half maximum of the XRD main peak of 2θ = 0.407°, a total acid content of 1.38 mmol / g, a silanol intensity ratio of 1.95, an SDA content of 1.09 mass%, and a proton-type cation, and exhibited the XRD peaks shown in Table 12 below. [Table 12]

[0177] The evaluation results for the examples and comparative examples are shown in Tables 13a and 13b below. In Tables 13a and 13b, ND indicates a result below the detection limit (less than 0.01% by mass). [Table 13a] [Table 13b]

[0178] These results show that the beta-zeolite obtained by the manufacturing method of this embodiment has a low silanol intensity ratio and a high total acid content.

[0179] Measurement example A 35% by mass aqueous solution of iron(III) nitrate was mixed with each of the beta-zeolites in the examples and comparative examples so that the mass ratio of iron content (hereinafter also referred to as "Fe content") to the total value of silicon (Si) content (converted to SiO2), aluminum (Al) content (converted to Al2O3), and iron (Fe) content was 3.0% by mass. The mixture was dried in an air atmosphere at 110°C for 4 hours. The resulting dried material was calcined in an air atmosphere at 500°C for 4 hours to obtain iron-containing beta-zeolites. Each of the obtained iron-containing beta-zeolites was used as a measurement sample (measurement sample before hydrothermal endurance treatment) in the following tests. The obtained iron-containing beta-zeolites were each iron-supported beta-zeolites with an Fe content of 3.0% by mass. In this measurement example, the Fe content corresponds to the content of the active metal elements mentioned above.

[0180] (Hydrothermal resistant treatment) The measurement sample (measurement sample before hydrothermal endurance treatment) was molded and pulverized to obtain agglomerated particles with an agglomeration diameter of 12 to 20 mesh. 3 mL of the agglomerated particles of the measurement sample was packed into a fixed-bed flow-through reaction tube at atmospheric pressure, and then hydrothermal endurance treatment was performed under the following conditions by passing a mixed gas containing 10% by volume of water vapor and 90% by volume of air through it. After the hydrothermal endurance treatment, the measurement sample was recovered from the fixed-bed flow-through reaction tube at atmospheric pressure, and this was used as the measurement sample after hydrothermal endurance treatment. Flow rate of the mixed gas: 300 mL / min Processing temperature: 700℃ Processing time: 20 hours

[0181] (Nitrogen oxide reduction rate (%)) 1.5 mL of the sample before and after hydrothermal treatment was packed into a fixed-bed flow-through reaction tube at atmospheric pressure. Nitrogen oxide-containing gas was circulated while maintaining the following measurement temperature, and the nitrogen oxide concentrations at the inlet and outlet of the fixed-bed flow-through reaction tube were measured. The flow conditions for the nitrogen oxide-containing gas were as follows. Composition of nitrogen oxide-containing gas: NO 200 ppm NH3200ppm O210% by volume H2O 3% by volume N2 remainder Flow rate of nitrogen oxide-containing gas: 1.5 L / min Space velocity: 60,000 hr -1 Measurement temperatures: 600 °C, 550 °C, 500 °C, 400 °C, 300 °C, 200 °C, 150 °C, stepwise temperature decrease

[0182] The nitrogen oxide reduction rate was determined from the obtained nitrogen oxide concentrations by the following formula (4). Nitrogen oxide reduction rate (%) ={([NOx]in - [NOx]out) / [NOx]in} × 100 ··· (4) In the above formula (4), [NOx]in is the nitrogen oxide concentration [ppm] of the nitrogen oxide-containing gas at the inlet of the atmospheric pressure fixed-bed flow-through reaction tube, and [NOx]out is the nitrogen oxide concentration [ppm] of the nitrogen oxide-containing gas at the outlet of the atmospheric pressure fixed-bed flow-through reaction tube.

[0183] The nitrogen oxide reduction rates of each measurement sample before the hydrothermal durability treatment (hereinafter also referred to as "fresh sample") and each measurement sample after the hydrothermal durability treatment (hereinafter also referred to as "durability sample") are shown in Table 14 below. In Table 14 below, 200 °C and 600 °C indicate the measurement temperatures.

Table 14

[0184] The iron-containing beta-zeolite of the example showed a higher nitrogen oxide reduction rate at 200°C activity after hydrothermal endurance treatment compared with the iron-containing beta-zeolite of the comparative example. From this, it was understood that the iron-containing beta-zeolite of the example has excellent hydrothermal endurance. Furthermore, the iron-containing beta-zeolite of the example showed a higher nitrogen oxide reduction rate at 200°C and 600°C activity before hydrothermal endurance treatment compared with the iron-containing beta-zeolite of Comparative Example 4, which underwent steam treatment. From this, it was understood that the iron-containing beta-zeolite of the example does not undergo accelerated dealuminization like the iron-containing beta-zeolite of Comparative Example 4, which underwent steam treatment, and exhibits excellent catalytic activity like conventional low-silica beta-zeolites. From these results, it was found that the beta-zeolite of this embodiment, with a total alkali metal content of 0.5% by mass or less, an SDA content of 4.0% by mass or less, an SiO2 / Al2O3 ratio of 20 to 35, and a silanol intensity ratio of 1.90 or less, exhibits excellent catalytic activity and excellent hydrothermal endurance.

[0185] Generally, zeolites with a low SiO2 / Al2O3 molar ratio are known to have low hydrothermal durability. Surprisingly, even the beta-zeolite with a low SiO2 / Al2O3 ratio, such as that in Example 1, showed a high nitrogen oxide reduction rate in the 200°C activity after hydrothermal durability treatment. Furthermore, while it is generally believed that the amount of silanol defects tends to increase as the SiO2 / Al2O3 molar ratio of zeolites decreases, surprisingly, Example 2, which had a lower SiO2 / Al2O3 molar ratio than Comparative Example 1, showed a lower silanol intensity ratio than Comparative Example 1 and exhibited a high nitrogen oxide reduction rate in the 200°C activity after hydrothermal durability treatment.

[0186] From the above results, it was understood that the beta-zeolite of this embodiment can be suitably used as a solid acid catalyst, and furthermore, can be suitably used as a nitrogen oxide reduction catalyst.

Claims

[Claim 1] The invention described herein.

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