Method for producing CHA type zeolite

Abstract

To provide a production method capable of obtaining a CHA type zeolite excellent in crystallinity and having a smaller amount of silanol defects in comparison to a conventional CHA type zeolite obtained using an N,N,N- trialkylcyclohexyl ammonium cation as a structure directing agent.SOLUTION: A method for producing CHA type zeolite includes: a crystallizing process of crystallizing a composition including an N,N,N-trialkylcyclohexyl ammonium cation source, an alumina source, a silica source, a sodium source, a rare earth element source, and water where the mole ratio of silica to alumina is 8 or more and 25 or less, to obtain a crystallized material; a calcining process of calcining the crystallized material at a temperature of 400°C or higher and 700°C or lower to obtain a calcined product; and an alkali-removing process of contacting the calcined product with an ammonium salt-containing solution.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing CHA-type zeolites using N,N,N-trialkylcyclohexylammonium cations as structure directing agents. [Background technology]

[0002] Artificially synthesized CHA-type zeolites are used as catalysts such as nitrogen oxide reduction catalysts and petrochemical catalysts. Various methods for producing CHA-type zeolites have been proposed so far, including methods using expensive structure-directing agents such as N,N,N-trimethyl-1-adamantane cations and methods using inexpensive structure-directing agents such as N,N,N-trialkylcyclohexylammonium cations (e.g., Patent Documents 1 and 2).

[0003] In CHA-type zeolites, the fewer silanol defects in the framework that constitutes them, the higher their heat resistance in a steam-containing atmosphere tends to be. However, when zeolites with a high aluminum content are exposed to high-temperature steam, aluminum is removed from the framework (dealuminization), increasing the number of silanol defects and reducing catalytic activity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent No. 2008 / 0045767 [Patent Document 2] US Patent No. 2019 / 0105639 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure aims to provide a manufacturing method for obtaining CHA-type zeolites with excellent crystallinity and fewer silanol defects than conventional CHA-type zeolites obtained using N,N,N-trialkylcyclohexylammonium cations as a structure-directing agent. [Means for solving the problem]

[0006] The present inventors have investigated the crystallization conditions in a method for producing CHA-type zeolite using N,N,N-trialkylcyclohexylammonium cations as a structure-directing agent, and have found that the amount of defects can be reduced by adding specific elements to the composition used for crystallization.

[0007] That is, the present invention is as defined in the claims, and the gist of the present disclosure is as follows. [1] A method for producing CHA-type zeolite, comprising: a crystallization step of crystallizing a composition containing an N,N,N-trialkylcyclohexylammonium cation source, an alumina source, a silica source, a sodium source, a rare earth element source, and water, wherein the molar ratio of silica to alumina is 8 or more and 25 or less, to obtain a crystallized product; a calcination step of calcining the crystallized product at 400°C or more and 700°C or less to obtain a calcined product; and an alkali removal step of contacting the calcined product with an ammonium salt-containing solution. [2] The method for producing CHA-type zeolite according to [1], wherein the composition has at least the following molar composition:

[0008] SiO2 / Al2O3 ratio: 3 or more and 25 or less TACH + / SiO2 ratio: 0.01 or more and 0.5 or less Na / SiO2 ratio: more than 0 and less than 0.60 RE / SiO2 ratio: more than 0 and less than 0.05 H2O / SiO2 ratio: 3 or more and 50 or less OH / SiO2 ratio: 0.10 or more and 1.50 or less However, TACH +represents an N,N,N-trialkylcyclohexylammonium cation, and RE represents a rare earth element. [3] The method for producing a CHA-type zeolite according to [1] or [2], wherein the composition contains one or more selected from the group consisting of an N,N,N-trialkyladamantanammonium cation source, a trimethylbenzylammonium cation source, and a tetraethylammonium cation source. [Effects of the Invention]

[0009] The present disclosure makes it possible to provide a production method for obtaining CHA-type zeolites with a smaller amount of silanol defects than conventional CHA-type zeolites obtained using N,N,N-trialkylcyclohexylammonium cations as a structure-directing agent. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a scanning electron microscope image of the yttrium-containing CHA-type zeolite of Example 1. [Figure 2] FIG. 2 is a scanning electron microscope image of the yttrium-containing CHA-type zeolite of Example 2. [Figure 3] FIG. 2 is a scanning electron microscope image of the yttrium-containing CHA-type zeolite of Example 3. [Figure 4] FIG. 2 is a scanning electron microscope image of the yttrium-containing CHA-type zeolite of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] The method for producing CHA-type zeolite of the present disclosure will be described below with reference to an example embodiment. The present disclosure includes any combination of the configurations and parameters disclosed herein, and also includes any combination of the upper and lower limits of the values ​​disclosed herein.

[0012] The terms used in this embodiment are as follows:

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

[0014] "Zeolite-like substances" are compounds with a regular structure in which T atoms are oxygen-mediated, and the T atoms contain at least one atom other than a metal or semimetal (hereinafter also referred to as a "non-metal atom"). Examples of non-metal atoms include phosphorus (P), and examples of zeolite-like substances include complex phosphorus compounds such as aluminophosphate (AlPO) and silicoaluminophosphate (SAPO).

[0015] The "regular structure in which T atoms are oxygen-mediated (hereinafter also referred to as "zeolite structure")" of zeolites and zeolite-like substances is a skeletal structure identified by the structure code (hereinafter also referred to simply as "structure code") established by the Structure Commission of the International Zeolite Association. For example, the CHA structure is a skeletal structure identified by the structure code "CHA." Zeolite structures can be identified by comparing the XRD patterns of each structure (hereinafter also referred to as "reference patterns") described in "Collection of simulated XRD powder patterns for zeolites, Fifth revised edition (2007)." In this embodiment, the terms "skeletal structure," "crystalline structure," and "crystalline phase" are used interchangeably.

[0016] An "aluminosilicate" is a composite oxide having a structure consisting of a repeating network of aluminum (Al) and silicon (Si) via oxygen (O). In this embodiment, aluminosilicates also include those having a structure consisting of a repeating network of aluminum (Al) and silicon (Si) via oxygen (O), and in which a portion of the aluminum (e.g., 30% or less of the aluminum as T atoms) is substituted with another metal atom. Among aluminosilicates, those that have a crystalline XRD peak in their powder X-ray diffraction (hereinafter also referred to as "XRD") pattern are called "crystalline aluminosilicates," and those that do not have a crystalline XRD peak are called "amorphous aluminosilicates."

[0017] In this embodiment, the XRD pattern is measured using CuKα radiation as a radiation source, and the measurement conditions include the following.

[0018] Acceleration current / voltage: 40mA / 40kV Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Continuous scan Scan condition: 40° / min Measurement range: 2θ=3° to 43° Divergence vertical limit slit: 10mm Divergence / entrance slit: 1° Receiving slit: open Receiving solar slit: 5° Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter The XRD pattern can be measured using a general powder X-ray diffractometer (e.g., Ultima IV, manufactured by Rigaku Corporation). Crystalline XRD peaks are those detected by identifying the 2θ of the peak top in XRD pattern analysis using general analysis software (e.g., SmartLab Studio II, manufactured by Rigaku Corporation), and in particular, XRD peaks with a half-width of 2θ = 1.0° or less.

[0019] The XRD pattern analysis conditions may be as follows:

[0020] Fitting conditions: Automatic, refine background 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-order differential method, σ cut value = 3, χ threshold = 1.5 The composition in this embodiment, such as the molar ratio of silica to alumina (hereinafter also referred to as the "SiO2 / Al2O3 ratio"), can be measured by ICP analysis using a general inductively coupled plasma optical emission spectrometer (e.g., OPTIMA7300DV, manufactured by PERKIN ELMER).

[0021] The "average crystal size" is the average particle size of primary particles, and primary particles are the smallest unit particles that can be observed independently in scanning electron microscope (hereinafter also referred to as "SEM") observation under the following conditions. SEM observation can be performed using a general scanning electron microscope (for example, device name: JSM-IT200, manufactured by JEOL Ltd.).

[0022] Accelerating voltage: 6 kV Magnification: 10,000±5,000x The average crystal size can be determined by measuring the longest diameter of the smallest unit particle that can be observed independently. In the case of rhombohedrons or cubes, the diagonal is measured, and in the case of irregular shapes, the longest diameter is measured, and the arithmetic mean of 50 particles (preferably 50±5 particles) is calculated. However, secondary aggregates formed by aggregation of primary particles are not considered to be independent particles, and are not used in calculating the average crystal size.

[0023] The "silanol intensity ratio" is an indicator of the amount of silanol defects in CHA-type zeolite. The smaller the silanol intensity ratio, the smaller the amount of silanol defects. The measurement of the silanol intensity ratio can be calculated from the IR spectrum obtained by Fourier transform infrared spectrophotometry (FT-IR) performed under the following conditions using a general FT-IR measuring device (for example, device name: Jasco FT / IR-6100, manufactured by JASCO Corporation).

[0024] Measurement sample: 0.01 g Pretreatment: Under vacuum, 450 °C (product temperature), 1 hour Measurement mode: Continuous scan Measurement temperature: Under vacuum, 200 °C (product temperature) Measurement range: 350 - 4000 cm -1 Resolution: 2.0 cm -1 Number of accumulations: 128 times Zero filling: ON Detector: TGS (Triglycine sulfate) The obtained IR spectrum may be subjected to waveform processing using general analysis software (for example, Spectra Mnager Version 2 Version 2.15.11, manufactured by JASCO Corporation). That is, the base start is set to 1580 cm -1 , the base end is set to 2100 cm -1 , and the base start is set to 3000 cm -1 , the base end is set to 3800 cm -1 and, after baseline correction of these ranges, a peak having a peak top in the range of 1860 (±10) cm -1 is defined as P1, and a peak having a peak top in the range of 3735 (±10) cm -1 is defined as P2. The silanol intensity ratio may be determined from the height intensities of P1 and P2 using the following formula. <000021​​​​​The present embodiment is a method for producing CHA-type zeolite, which includes a crystallization step of crystallizing a composition containing an N,N,N-trialkylcyclohexylammonium cation source, an alumina source, a silica source, a sodium source, a rare earth element source, and water, wherein the molar ratio of silica to alumina is 25 or less, to obtain a crystallized product; a calcination step of calcining the crystallized product at 400°C or higher and 700°C or lower to obtain a calcined product; and an alkali removal step of contacting the calcined product with an ammonium salt-containing solution. (crystallization process) The method for producing CHA-type zeolite of this embodiment includes a crystallization step of crystallizing a composition (hereinafter also referred to as the "raw material composition") containing an N,N,N-trialkylcyclohexylammonium cation source, an alumina source, a silica source, a sodium source, a rare earth element source, and water, and having a molar ratio of silica to alumina of 25 or less, to obtain a crystallized product.

[0026] It is believed that by crystallizing a raw material composition containing a rare earth element source in the crystallization process, CHA-type zeolite is crystallized while some or all of the rare earth elements are incorporated in a state that makes it less likely to generate silanol defects in the CHA-type zeolite.

[0027] The SiO2 / Al2O3 ratio of the raw material composition is 25 or less. If the SiO2 / Al2O3 ratio of the raw material composition exceeds 25, the resulting CHA zeolite will have a low acidity and its catalytic activity will be prone to decline. The SiO2 / Al2O3 ratio may be 3 to 25, 3 to 23, 3 to 20, 3 to 15, 5 to 25, 5 to 23, 5 to 20, 5 to 15, 8 to 25, 8 to 23, 8 to 20, or 8 to 15.

[0028] The raw material composition contains N,N,N-trialkylcyclohexylammonium cation (hereinafter referred to as "TACH + This allows for a cheaper method of producing CHA-type zeolite than the method using N,N,N-trimethyl-1-adamantane cation as the main organic structure directing agent (hereinafter also referred to as "SDA"). +Specific TACH included in the source + As the cation, N,N,N-trimethylcyclohexylammonium cation (hereinafter referred to as "TMCH + "), N,N,N-dimethylethylcyclohexylammonium cation (hereinafter referred to as "DMECH + "), N,N,N-methyldiethylcyclohexylammonium cation (hereinafter referred to as "MDECH + ") and N,N,N-triethylcyclohexylammonium cation (hereinafter referred to as "TECH + ") group, and DMECH + and MDECH + At least one of the above is preferred, and DMECH + or MDECH + is more preferred, and DMECH + is more preferred.

[0029] TACH contained in the raw material composition + The source may be two or more, etc. + If there are two or more sources, DMECH + Source, MDECH + Source & Tech + Preferably, two or more selected from the group of DMECH + Source & MDECH + Source is more preferable.

[0030] TACH + Source: TACH + and salts containing, for example, TACH + Examples of the hydroxide include one or more selected from the group consisting of hydroxides, halides, carbonate monoester salts, and sulfate monoester salts; one or more selected from the group consisting of hydroxides, chlorides, bromides, and iodides; one or more selected from the group consisting of hydroxides, bromides, and iodides; at least one of hydroxides and bromides; or hydroxide.

[0031] The raw material composition contains TACH as SDA. +However, in order to further improve the yield of CHA-type zeolite, it is preferable to use TACH as an SDA oriented to the CHA structure, as long as it is within the range that is commensurate with the industrial production cost. + The SDA may contain an SDA other than the above (hereinafter also referred to as "Add-SDA"). As the Add-SDA, N,N,N-trialkyladamantanammonium cation (hereinafter referred to as "TAAd + "). ) source, trimethylbenzylammonium cation source, and tetraethylammonium cation source (Add-SDA cation source), and one or more selected from the group consisting of a cation source. Specific examples of TAAd + The source of Add-SDA is N,N,N-trimethyl-1-adamantanammonium cation. When the raw material composition contains an Add-SDA source, TACH + It is preferred that the content of Add-SDA is less than 100%.

[0032] Mainly TACH + In order to crystallize CHA-type zeolite by the structure-directing effect of + The molar ratio of Add-SDA to TACH (hereinafter referred to as "Add-SDA / TACH") + The Add-SDA / SDA ratio may be 0 or more and 1 or less, more than 0 and less than 1, or 0.05 or more and 0.5 or less. The raw material composition may not contain Add-SDA, and the Add-SDA / SDA ratio may be 0 (zero).

[0033] The alumina source is at least one of alumina (Al2O3) and a precursor thereof, and examples thereof 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. Further, it is preferably one or more selected from the group consisting of amorphous aluminum compounds, aluminum hydroxide, crystalline aluminosilicate, and amorphous aluminosilicate, or even amorphous aluminosilicate.

[0034] The silica source is at least one of silica (SiO2) and a precursor thereof, and examples thereof 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. At least one of crystalline aluminosilicate and amorphous aluminosilicate, and even amorphous aluminosilicate are preferred.

[0035] At least one of the alumina source and the silica source preferably contains an amorphous aluminosilicate, and it is more preferable that both the alumina source and the silica source contain an amorphous aluminosilicate, which tends to reduce production costs and is industrially advantageous.

[0036] The sodium source may be a salt or compound containing sodium. Examples of the salt or compound containing sodium include one or more selected from the group consisting of chloride, iodide, bromide, sulfate, hydroxide, and oxide of sodium, preferably one or more selected from the group consisting of chloride, bromide, and hydroxide of sodium, and more preferably sodium hydroxide. Sodium contained in other starting materials may also be considered as a sodium source. The raw material composition preferably contains at least sodium hydroxide.

[0037] The raw material composition may contain a source of an alkali metal other than sodium. Examples of sources of alkali metal other than sodium include compounds containing alkali metal elements other than sodium. Examples of salts or compounds containing alkali metal elements other than sodium include one or more selected from the group consisting of chlorides, iodides, bromides, sulfates, hydroxides, and oxides of alkali metals other than sodium. Preferred are one or more selected from the group consisting of chlorides, bromides, and hydroxides of alkali metals other than sodium, and more preferred are hydroxides of alkali metals other than sodium. In addition, alkali metals other than sodium contained in other starting materials can also be considered sources of alkali metals other than sodium.

[0038] Examples of alkali metal elements other than sodium include one or more selected from the group consisting of lithium, potassium, rubidium, and cesium. In terms of the tendency to reduce the amount of silanol defects, the alkali metal elements other than sodium are preferably one or more selected from the group consisting of lithium, potassium, and cesium, more preferably at least one of potassium and cesium, and even more preferably potassium.

[0039] The rare earth element source may be a salt or compound containing a rare earth element. Examples of the salt or compound containing a rare earth element include one or more selected from the group consisting of chlorides, iodides, bromides, nitrates, acetates, sulfates, carbonates, hydroxides, and oxides of rare earth elements. One or more selected from the group consisting of chlorides, nitrates, acetates, sulfates, carbonates, and hydroxides of rare earth elements is preferred, with at least one of acetates and nitrates of rare earth elements being more preferred. Rare earth elements contained in other starting materials can also be considered sources of rare earth elements.

[0040] The rare earth element contained in the rare earth element source may be one or more selected from the group consisting of cerium (Ce), yttrium (Y), lanthanum (La), samarium (Sm), scandium (Sc), praseodymium (Pr), and neodymium (Nd). In terms of reducing the amount of silanol defects, the rare earth element is preferably one or more selected from the group consisting of cerium, yttrium, lanthanum, and samarium, more preferably one or more selected from the group consisting of cerium, yttrium, and lanthanum, and even more preferably yttrium.

[0041] The raw material composition preferably contains at least yttrium nitrate.

[0042] The water contained in the raw material composition may be deionized water or pure water, or may be structured water, water as a solvent, or water (H2O) contained in other starting materials.

[0043] The raw material composition preferably does not contain fluorine (F) or phosphorus (P), and the fluorine and phosphorus contents of the raw material composition are each below the detection limit (for example, the fluorine content is 1 ppm by mass or less, the phosphorus content is 1 ppm by mass or less, or the total content of fluorine and phosphorus is 1 ppm by mass or less).

[0044] The preferred composition of the raw material composition is the following molar composition: + DMECH + TACH when etc. + / SiO2 ratio is DMECH + In addition, when M is an alkali metal element other than sodium and the raw material composition contains two or more alkali metal elements other than sodium (for example, potassium and cesium), the M / SiO2 ratio may be considered as a (K+Cs) / SiO2 ratio or the like. When RE is a rare earth element and the raw material composition contains two or more rare earth elements (for example, cerium and yttrium), the RE / SiO2 ratio may be considered as a (Ce+Y) / SiO2 ratio or the like. Furthermore, each composition ratio in the molar composition may be any combination of the upper and lower limits described below.

[0045] SiO2 / Al2O3 ratio: 3 to 25, 3 to 23, 3 to 20, 3 to 15, 5 to 25, 5 to 23, 5 to 20, 5 to 15, 8 to 25, 8 to 23, 8 to 20, or 8 to 15 TACH + / SiO2 ratio: 0.01 or more and 0.5 or less, 0.01 or more and 0.30 or less, 0.01 or more and 0.20 or less, 0.01 or more and 0.10 or less, 0.02 or more and 0.5 or less, 0.02 or more and 0.30 or less, 0.02 or more and 0.20 or less, 0.02 or more and 0.10 or less, 0.05 or more and 0.5 or less, 0.05 or more and 0.30 or less, 0.05 or more and 0.20 or less, 0.05 or more and 0.10 or less, 0.07 or more and 0.5 or less, 0.07 or more and 0.30 or less, 0.07 or more and 0.20 or less, or 0.07 or more and 0.10 or less.

[0046] Add-SDA / TACH+ Ratio: 0 or more and 1 or less, 0 or more and 0.5 or less, 0 or more and 0.4 or less, 0.05 or more and 1 or less, 0.05 or more and 0.5 or less, or 0.05 or more and 0 or less and 1 or less, 0.5 or less, or 0.4 or less Na / SiO2 ratio: More than 0 and up to 0.60, more than 0 and up to 0.50, more than 0 and up 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. More than 0, 0.03 or 0.06 or more, and up to 0.60, 0.5 or less, 0.4 or less, or 0.3 or less M / SiO2 ratio: 0 or more and 0.60 or less, 0 or more and 0.50 or less, 0 or more and 0.30 or less, 0.03 or more and 0.60 or less, 0.03 or more and 0.50 or less, 0.03 or more and 0.30 or less, 0.06 or more and 0.60 or less, 0.06 or more and 0.50 or less, or 0.06 or more and 0.30 or less.

[0047] RE / SiO2 ratio: greater than 0 and less than 0.05, greater than 0 and less than 0.03, greater than 0 and less than 0.015, 0.001 or more and less than 0.05, 0.001 or more and less than 0.03, 0.001 or more and less than 0.015, 0.005 or more and less than 0.05, 0.005 or more and less than 0.03, or 0.005 or more and less than 0.015.

[0048] H2O / SiO2 ratio: 3 or more and 50 or less, 3 or more and 30 or less, 3 or more and 20 or less, 3 or more and 19 or less, 5 or more and 50 or less, 5 or more and 30 or less, 5 or more and 20 or less, 5 or more and 19 or less, 10 or more and 50 or less, 10 or more and 30 or less, 10 or more and 20 or less, or 10 or more and 19 or less.

[0049] OH / SiO2 ratio :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, 0.12 to 1.50, 0.12 to 1.00, 0.12 0.80 or more, 0.12 or more and 0.60 or less, 0.12 or more and 0.45 or less, 0.15 or more and 1.50 or less, 0.15 or more and 1.00, 0.15 or more and 0.80, 0.15 or more and 0.60 or less, 0.15 or more and 0.45 or less.

[0050] The raw material composition may contain seed crystals to promote the crystallization of CHA zeolite. Examples of seed crystals include one or more selected from the group consisting of AEI zeolite, AFX zeolite, ERI zeolite, CHA zeolite, LEV zeolite, and OFF zeolite, and further include CHA zeolite. When the raw material composition contains seed crystals, the ratio of the total mass of silicon (Si) and aluminum (Al) of the seed crystals, converted into SiO and AlO, respectively, to the total mass of silicon (Si) and aluminum (Al) of the raw material composition (excluding seed crystals), converted into SiO and AlO, respectively (hereinafter also referred to as "seed crystal content") may be 0 to 10% by mass, 0 to 5% by mass, or 0 to 3% by mass. The raw material composition may not contain seed crystals, i.e., the seed crystal content may be 0% by mass.

[0051] In the crystallization step, the raw material composition is crystallized to obtain a crystallized product (CHA-type zeolite). The crystallization method may be any method that crystallizes the raw material composition, and may be hydrothermal synthesis. Examples of conditions for hydrothermal synthesis include the following:

[0052] Crystallization temperature: 130 to 200°C, 140 to 180°C, or 150 to 170°C.

[0053] Crystallization time: 1 hour or more, 10 hours or more, 10 hours or more and 1 hour 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 Crystallization state: at least one of a stirring state and a static state, or a stirring state Crystallization pressure: Autogenous pressure For example, when crystallizing CHA-type zeolite with an SiO2 / Al2O3 ratio of 25 or less, if the crystallization temperature is 130 to 200°C, single-phase CHA-type zeolite can be crystallized in 2 days or less.

[0054] Prior to the calcination step, the crystallized material may be washed and dried.

[0055] The crystallized product may be washed by any method after crystallization. For example, the crystallized product obtained as a solid phase after the crystallization step may be washed with pure water in an amount such that the mass of the pure water is at least 1 times the total mass of the raw material composition excluding the seed crystals used for crystallization. For example, if the total mass of the raw material composition is 60 g, washing with at least 60 g of pure water may be performed regardless of whether seed crystals are added. Drying may be performed by any method capable of removing moisture physically adsorbed on the crystallized product. For example, drying may be performed by treating the crystallized product in at least one of an oxidizing atmosphere and an inert atmosphere at 100°C to 200°C for at least 2 hours. (Firing process) The method for producing CHA-type zeolite of this embodiment includes a calcination step of calcining the crystallized product obtained in the crystallization step at a temperature of 400° C. or higher and 700° C. or lower. As a result, the TACH contained in the crystallized product (CHA-type zeolite) is reduced. + A fired product can be obtained from which the above-mentioned oxidizing agents have been removed.

[0056] The firing atmosphere is TACH + The atmosphere may be any atmosphere capable of removing the carbon monoxide, and may be at least one of an oxidizing atmosphere, an inert atmosphere, and a reducing atmosphere, and is preferably an oxidizing atmosphere, or more preferably an air atmosphere.

[0057] SDA removal is performed by removing TACH from the crystallized material (CHA-type zeolite). + Any method capable of removing SDA may be used. SDA removal methods include at least one of calcination and acid treatment, with calcination being preferred. Calcination may involve treating the crystallized material 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 700°C. A particularly preferred calcination method is calcination in an air atmosphere at 550°C to 650°C. The calcination (and acid treatment) time can be, for example, from 1 hour to 5 hours, but may be adjusted appropriately depending on the amount of crystallized material to be subjected to the calcination. (Alkali removal process) The method for producing CHA-type zeolite of this embodiment includes an alkali removal step in which the calcined product obtained in the calcination step is brought into contact with an ammonium salt-containing solution, thereby removing alkali metal elements such as sodium contained in the calcined product.

[0058] The ammonium-containing solution contains ammonium (NH4 + ) and a solvent.

[0059] The solvent may be any medium in which the ammonium salt dissolves, and may be at least one of alcohol and water, and may be water, that is, the ammonium-containing solution may be an aqueous ammonium-containing solution.

[0060] Ammonium salts are ammonium (NH4 + ) may be used, and examples thereof include inorganic salts of ammonium, and further, one or more selected from the group consisting of ammonium carbonate, ammonium chloride and ammonium nitrate, and further, ammonium chloride.

[0061] The ammonium-containing solution is + The concentration is preferably 1% by mass or more and 30% by mass or less, and more preferably 5% by mass or more and 20% by mass or less.

[0062] In order to sufficiently remove alkali metals from the fired product after the firing step, the ratio of the mass of the ammonium-containing solution to the mass of the crystallized product (CHA-type zeolite not containing SDA) (hereinafter also referred to as "NH4 / CHA") is preferably 10 or less, 8 or less, or 6 or less. NH4 / CHA may be greater than 1, 1.5 or more, or 2 or more. (Active metal containing process) When the CHA type zeolite of this embodiment is an active metal-containing CHA type zeolite, the production method of this embodiment may include a step of contacting the CHA type zeolite with an active metal source (hereinafter also referred to as the "active metal-containing step"). This results in an active metal-containing CHA type zeolite (or an active metal-supported CHA type zeolite).

[0063] In the active metal-containing step, any active metal element is incorporated into the CHA-type zeolite obtained in the alkali removal step, and preferably, any transition metal element is supported on the CHA-type zeolite. The incorporation of the active metal may be achieved by any method in which the CHA-type zeolite and the active metal source are brought into contact such that the active metal element is included other than the T atoms of the CHA-type zeolite. Examples include one or more selected from the group consisting of an ion exchange method, an impregnation method, an evaporation to dryness method, a precipitation method, and a physical mixing method, and the impregnation method is preferred. As the impregnation method, a method of bringing the CHA-type zeolite obtained in the alkali removal step into contact with a solution containing the active metal source can be mentioned.

[0064] The active metal source is at least one of salts and compounds containing the active metal element, and may be one or more selected from the group consisting of nitrates, sulfates, acetates, chlorides, complex salts, oxides, and composite oxides containing the active metal element, or one or more selected from the group consisting of nitrates, sulfates, and chlorides.

[0065] The active metal element includes a transition metal element, and more preferably, one or more selected from the group consisting of Group 8, Group 9, Group 10, and Group 11 of the periodic table. 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) are preferred, at least one of iron and copper is more preferred, and copper is even more preferred.

[0066] The solvent of the solution containing the active metal source may be any solvent in which at least one of the salts and compounds containing the active metal element is dissolved, and water, and more preferably, at least one of pure water and ion-exchanged water is preferred.

[0067] <CHA-type zeolite> The zeolite obtained by the CHA-type zeolite manufacturing method of this embodiment includes CHA-type zeolite containing rare earth elements (hereinafter also referred to as "rare-earth-containing CHA-type zeolite"). Below, the rare-earth-containing CHA-type zeolite manufactured by the CHA-type zeolite manufacturing method of this embodiment (hereinafter also referred to as "rare-earth-containing CHA-type zeolite of this embodiment") will be described.

[0068] The rare earth-containing CHA-type zeolite of this embodiment preferably has an SiO2 / Al2O3 ratio of 3 or more and 25 or less. With an SiO2 / Al2O3 ratio in this range, the carrier can be expected to exhibit high nitrogen oxide reduction properties and durability. The SiO2 / Al2O3 ratio of the rare earth-containing CHA-type zeolite of this embodiment is more preferably 5 or more and 25 or less, and more preferably 8 or more and 25 or less.

[0069] The rare earth-containing CHA-type zeolite of this embodiment contains a rare earth element. When the CHA-type zeolite contains a rare earth element, the amount of silanol defects is reduced, and when an activated metal is contained, the nitrogen oxide reduction rate after hydrothermal durability treatment tends to be high. The rare earth element can be one or more selected from the group consisting of cerium, yttrium, lanthanum, samarium, scandium, praseodymium, and neodymium. The rare earth element is preferably one or more selected from the group consisting of cerium, yttrium, lanthanum, and samarium, more preferably one or more selected from the group consisting of cerium, yttrium, and lanthanum, and even more preferably yttrium.

[0070] In the rare earth-containing CHA-type zeolite of this embodiment, the rare earth element (RE) content (hereinafter also referred to as "rare earth element content") is preferably 0.01% by mass or more and 5.0% by mass or less relative to the silicon (Si) content in SiO2 equivalent, the aluminum (Al) content in Al2O3 equivalent, the sodium (Na) content in Na2O equivalent, the alkali metals other than sodium (M) content in MO equivalent, and the total content of rare earth elements (RE) (hereinafter also referred to as "metal content"). With the rare earth element content in this range, high durability can be expected. The rare earth element content of the rare earth-containing CHA-type zeolite of this embodiment is more preferably 0.01% by mass or more and 4.5% by mass or less, more preferably 0.03% by mass or more and 3.5% by mass or less, more preferably 0.05% by mass or more and 3.0% by mass or less, and preferably 0.05% by mass or more and 2.5% by mass or less.

[0071] In the rare earth-containing CHA-type zeolite of this embodiment, the sodium content calculated as Na2O (hereinafter also referred to as "Na2O content") relative to the metal content is preferably 0 mass% or more and 0.20 mass% or less, more preferably more than 0 mass% and 0.10 mass% or less, and even more preferably more than 0 mass% and 0.06 mass% or less.

[0072] In the rare earth-containing CHA-type zeolite of this embodiment, the content of alkali metals other than sodium converted to MO relative to the metal content (hereinafter also referred to as "MO content") is preferably 0% by mass or more and 0.20% by mass or less, more preferably more than 0% by mass and 0.10% by mass or less, and even more preferably more than 0% by mass and 0.06% by mass or less.

[0073] For example, the composition of a rare earth-containing CHA-type zeolite containing Na and K as alkali metal elements and Y as a rare earth element may be determined as follows.

[0074] Rare earth content (yttrium content) [mass%] ={Y[g] / (SiO2+Al2O3+Na2O+K2O+Y[g])}×100 Na2O content [mass%] ={Na2O[g] / (SiO2+Al2O3+Na2O+K2O+Y[g])}×100 K2O content (M2O content) [mass%] ={K2O[g] / (SiO2+Al2O3+Na2O+K2O+Y[g])}×100 The rare earth-containing CHA-type zeolite of this embodiment preferably has a silanol intensity ratio of 2.0 or less. With the silanol intensity ratio at the above value, high heat resistance in a steam-containing atmosphere can be expected. The silanol intensity ratio of the rare earth-containing CHA-type zeolite of this embodiment is preferably 0 or more and 2.0 or less, more preferably more than 0 and 1.8 or less, even more preferably 0.2 or more and 1.5 or less, and even more preferably 0.3 or more and 1.2 or less.

[0075] The rare earth-containing CHA-type zeolite of this embodiment preferably has an average crystal size of 0.1 μm or more and 1.0 μm or less. With an average crystal size in this range, excellent coating properties on honeycombs can be expected. Furthermore, rare earth-containing CHA-type zeolites having this average crystal size can be expected to serve as carriers that exhibit high SCR performance. The average crystal size of the rare earth-containing CHA-type zeolite of this embodiment is more preferably 0.15 μm or more and 0.95 μm or less, and more preferably 0.20 μm or more and 0.80 μm or less.

[0076] It is preferable that the rare earth-containing CHA-type zeolite of this embodiment contains a rare earth element in the zeolite structure, and more preferably, when the radiation source is CuKα radiation (λ=1.5405 Å), the half-width (hereinafter simply referred to as "half-width") of the XRD peak having a peak top at 2θ=20.80±0.15° in its XRD pattern is 0.225° or more and 0.400° or less.

[0077] The rare earth-containing CHA-type zeolite of this embodiment is produced by crystallizing a raw material composition containing a rare earth element source, and therefore the CHA-type zeolite crystallizes while incorporating rare earth elements, which is thought to result in the rare earth elements being incorporated into the zeolite structure. Furthermore, compared to CHA-type zeolites that do not contain rare earth elements in their zeolite structure, the incorporation of rare earth elements causes distortion of the zeolite structure, which tends to result in a larger half-width. Therefore, the half-width of the rare earth-containing CHA-type zeolite of this embodiment is preferably 0.225° or more and 0.375° or less, and more preferably 0.230° or more and 0.350° or less. [Example]

[0078] The present disclosure will be described below with reference to examples, but the present disclosure is not limited thereto. (zeolite structure) The sample was subjected to XRD measurement using a powder X-ray diffractometer (device name: Ultima IV, manufactured by Rigaku Corporation) under the following measurement conditions.

[0079] Acceleration current / voltage: 40mA / 40kV Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Continuous scan Scan condition: 40° / min Measurement range: 2θ=3° to 43° Divergence vertical limit slit: 10mm Divergence / entrance slit: 1° Receiving slit: open Receiving solar slit: 5° Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter The XRD pattern was measured using a standard powder X-ray diffractometer (Ultima IV, manufactured by Rigaku Corporation). The crystalline XRD peaks were detected by identifying the 2θ of the peak top in the XRD pattern analysis using standard analysis software (SmartLab Studio II, manufactured by Rigaku Corporation). The XRD pattern was analyzed under the following conditions.

[0080] Fitting conditions: Automatic, refine background 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-order differential method, σ cut value = 3, χ threshold = 1.5 (composition analysis) The composition of the sample was analyzed using a general inductively coupled plasma optical 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 a measurement solution. The composition of the sample was analyzed using the obtained measurement solution. (average crystal size) SEM images of the samples were obtained using a standard scanning electron microscope (JSM-IT200, manufactured by JEOL). The average crystal size was calculated by measuring the diagonal of the smallest particle that could be observed independently, if the particle was rhombohedral or cubic, or the longest diameter if the particle was irregular, and then calculating the arithmetic mean of 50 ± 5 particles. However, secondary aggregates formed by aggregation of primary particles were not used in calculating the average crystal size, as they were not considered to be independent particles. (Silanol intensity ratio) The silanol intensity ratio was measured using a general FT-IR measurement device (device name: Jasco FT / IR-6100, manufactured by Jasco Engineering) under the following conditions and calculated from the IR spectrum obtained by Fourier transform infrared spectrophotometric measurement (FT-IR).

[0081] Measurement sample: 0.01g Pretreatment: Under vacuum, 450℃ (product temperature), 1 hour Measurement mode: Continuous scan Measurement temperature: 200℃ under vacuum (product temperature) Measurement range: 350~4000cm -1 Resolution: 2.0cm -1 Accumulation count: 128 times Zero filling: ON Detector: TGS (Triglycine sulfate) The obtained IR spectrum was subjected to waveform processing using a general analysis software (Spectra Manager Version 2 Version 2.15.11, manufactured by JASCO Corporation). -1 , base end 2100cm -1 , and base start at 3000 cm -1 , base end 3800cm -1 After baseline correction of these ranges, 1860 (± 10) cm -1 The peak with a peak top in the range of 3735 (±10) cm is P1. -1 The peak having a peak top in this range was designated as P2. The silanol intensity ratio was calculated from the height intensities of P1 and P2 using the above formula (1).

[0082] Example 1 A 50 mass% aqueous solution of dimethylethylcyclohexylammonium bromide (DMECHABr), a 25 mass% aqueous solution of N,N,N-trimethyl-1-adamantanammonium hydroxide (TMAdOH), a 48 mass% aqueous solution of sodium hydroxide, a 48 mass% aqueous solution of potassium hydroxide, yttrium (III) nitrate hexahydrate, pure water, and amorphous aluminosilicate (SiO2 / Al2O3 ratio: 14.0) were mixed together to a total amount of 60 g to obtain a raw material composition having the following molar composition.

[0083] SiO2 / Al2O3 ratio: 14.0 DMECH + / SiO2 ratio: 0.07 TMAda+ / SiO2 ratio: 0.01 Add-SDA + / TACH + Ratio: 0.14 Na / SiO2 ratio: 0.14 K / SiO2 ratio: 0.06 Y / SiO2 ratio: 0.0104 H2O / SiO2 ratio: 15 OH / SiO2 ratio: 0.21 The obtained raw material composition and CHA-type zeolite (SSZ-13, SiO / Al O : 25) as seed crystals were mixed so that the amount was 1.0 mass% relative to the total amount of Si (calculated as SiO ) and Al (calculated as Al O ) in the raw material composition, and then this was filled into an 80 ml sealed container and hydrothermally treated at 160 ° C for 48 hours under a rotation of 55 rpm to obtain a crystallized product. The obtained crystallized product was recovered by solid-liquid separation, washed with pure water in an amount 1 mass times the total amount of the raw material composition, and then dried in an air atmosphere at 110 ° C for 4 hours. The dried crystallized product was calcined in an air atmosphere at 600 ° C for 4 hours to obtain a calcined product.

[0084] The obtained fired product had an SiO2 / Al2O3 ratio of 14.4, a Na2O content of 1.61 mass%, a K2O content (M2O content) of 2.94 mass%, and an yttrium content (rare earth element content) of 1.30 mass%, and was a CHA-type zeolite containing yttrium (hereinafter also referred to as "yttrium-containing CHA-type zeolite") consisting of a single phase of the CHA structure.

[0085] Ion exchange was performed by mixing 10 g of the yttrium-containing CHA-type zeolite with an ammonium chloride aqueous solution with an ammonium chloride concentration of 20% by mass. The amount of ammonium chloride aqueous solution used for ion exchange was 3.5 times the mass of the yttrium-containing CHA-type zeolite. The yttrium-containing CHA-type zeolite after ion exchange was washed with pure water in an amount 10 times the mass of the yttrium-containing CHA-type zeolite and dried overnight at 110°C in an air atmosphere to obtain the yttrium-containing CHA-type zeolite of this example. The yttrium-containing CHA-type zeolite of this example (cation type is ammonium type) had a SiO / AlO ratio of 14.4, a NaO content of less than 0.01% by mass (below the detection limit), a KO content (MO content) of 0.02% by mass, an yttrium content (rare earth element content) of 0.93% by mass, and a silanol intensity ratio of 0.49.

[0086] An SEM image of the yttrium-containing CHA-type zeolite of this example is shown in Figure 1. The yttrium-containing CHA-type zeolite of this example was composed of aggregated particles formed by aggregation of cubic primary particles. The average crystal size of the yttrium-containing CHA-type zeolite of this example was 0.49 μm.

[0087] Example 2 A raw material composition having the following molar composition was obtained by mixing a 50 mass% DMECHABr aqueous solution, a 35 mass% DMECHAOH aqueous solution, a 48 mass% sodium hydroxide aqueous solution, a 48% potassium hydroxide aqueous solution, yttrium (III) nitrate hexahydrate, pure water, and amorphous aluminosilicate (SiO2 / Al2O3 ratio: 20.0).

[0088] SiO2 / Al2O3 ratio: 20.0 DMECH + / SiO2 ratio: 0.08 (Add-SDA + / TACH + ratio:0.00) Na / SiO2 ratio: 0.08 K / SiO2 ratio: 0.08 Y / SiO2 ratio: 0.0101 H2O / SiO2 ratio: 18 OH / SiO2 ratio: 0.18 The obtained raw material composition and CHA-type zeolite (SSZ-13, SiO / AlO:25) as seed crystals were used in an amount of 1.0 mass% relative to the total amount of Si converted into SiO and Al converted into AlO in the raw material composition, and were crystallized, washed, dried, and fired in the same manner as in Example 1. The fired product obtained was an yttrium-containing CHA-type zeolite with a SiO / AlO ratio of 20.7, a NaO content of 0.33 mass%, a KO content (MO content) of 1.78 mass%, and a yttrium content (rare earth element content) of 1.27 mass%.

[0089] The yttrium-containing CHA zeolite was subjected to ion exchange, washing, and drying to obtain the CHA zeolite of this example in the same manner as in Example 1. The CHA zeolite of this example had a SiO / AlO ratio of 20.8, a NaO content below the lower detection limit (less than 0.01% by mass), a KO content (MO content) of 0.02% by mass, an yttrium content (rare earth element content) of 1.11% by mass, and a silanol intensity ratio of 0.38.

[0090] An SEM image of the yttrium-containing CHA-type zeolite of this example is shown in Figure 2. The yttrium-containing CHA-type zeolite of this example was composed of aggregated particles formed by aggregation of cubic primary particles. The average crystal size of the yttrium-containing CHA-type zeolite of this example was 0.76 μm.

[0091] Example 3 A raw material composition having the following molar composition was obtained by mixing a 35 mass % DMECHAOH aqueous solution, a 48 mass % sodium hydroxide aqueous solution, yttrium (III) nitrate hexahydrate, pure water, and amorphous aluminosilicate (SiO2 / Al2O3 ratio: 10.6).

[0092] SiO2 / Al2O3 ratio: 10.6 DMECH + / SiO2 ratio: 0.08 Add-SDA + / TACH + Ratio:0.00 Na / SiO2 ratio: 0.27 K / SiO2 ratio: 0.00 Y / SiO2 ratio: 0.0103 H2O / SiO2 ratio: 18 OH / SiO2 ratio: 0.35 The obtained raw material composition and CHA-type zeolite (SSZ-13, SiO2 / Al2O3 ratio: 25) as seed crystals were crystallized, washed, dried, and fired in the same manner as in Example 1, except that 2.0 mass% of seed crystals were used relative to the total amount of Si converted into SiO2 and Al converted into Al2O3 in the raw material composition, and the crystallization temperature was 165° C. The obtained fired product was an yttrium-containing CHA-type zeolite with a SiO2 / Al2O3 ratio of 10.4, a Na2O content of 5.99 mass%, and an yttrium content (rare earth element content) of 1.28 mass%.

[0093] The yttrium-containing CHA-type zeolite was subjected to ion exchange, washing, and drying to obtain the yttrium-containing CHA-type zeolite of this example in the same manner as in Example 1. The CHA-type zeolite of this example had a SiO / AlO ratio of 10.4, a NaO content of 0.04 mass%, a KO content (MO content) below the lower detection limit (less than 0.01 mass%), an yttrium content (rare earth element content) of 1.17 mass%, and a silanol intensity ratio of 0.75.

[0094] An SEM image of the yttrium-containing CHA-type zeolite of this example is shown in Figure 3. The yttrium-containing CHA-type zeolite of this example was composed of aggregated particles formed by aggregation of cubic primary particles. The average crystal size of the yttrium-containing CHA-type zeolite of this example was 0.28 μm.

[0095] Comparative Example 1 CHA-type zeolite was obtained based on the typical SSZ-13 manufacturing method described in IZA (Internal Zeolite Association) (http: / / www.iza-online.org / synthesis / default.htm), except that the SiO2 / Al2O3 ratio was set to 15.0. That is, a 48 mass% sodium hydroxide aqueous solution, a 25 mass% TMAdaOH aqueous solution, pure water, aluminum hydroxide, and fumed silica were mixed to obtain a raw material composition having the following molar composition in a total amount of 60 g.

[0096] SiO2 / Al2O3 ratio: 15.0 DMECH + / SiO2 ratio: 0.00 TMAda + / SiO2 ratio: 0.20 Na / SiO2 ratio: 0.10 K / SiO2 ratio: 0.00 H2O / SiO2 ratio: 44 OH / SiO2 ratio: 0.30 The obtained raw material composition was mixed without adding seed crystals, and then packed into a sealed container. The mixture was then subjected to hydrothermal treatment at 160°C for 96 hours at a rotation speed of 55 rpm to crystallize the mixture. A calcined product was obtained in the same manner as in Example 1. The calcined product was CHA-type zeolite with a SiO / AlO ratio of 16.3 and a NaO content of 1.97% by mass. The calcined product was subjected to ion exchange, washing, and drying in the same manner as in Example 1 to obtain CHA-type zeolite. The obtained CHA-type zeolite had a SiO / AlO ratio of 17.1, an NaO content below the lower limit of detection (less than 0.01% by mass), and a KO content (MO content) below the lower limit of detection (less than 0.01% by mass).

[0097] 10 g of the CHA-type zeolite was contacted with an aqueous solution prepared by dissolving 0.591 g of yttrium (III) nitrate hexahydrate in 5 g of pure water so that the yttrium content was 1.35% by mass, and the yttrium was incorporated by impregnation, followed by drying in an air atmosphere at 110°C. The CHA-type zeolite was then calcined in an air atmosphere at 550°C for 2 hours to obtain the yttrium-containing CHA-type zeolite of this comparative example. The CHA-type zeolite of this comparative example had an SiO2 / Al2O3 ratio of 17.1 and a Na2O content below the lower detection limit (less than 0.01% by mass). 、 The K2O content (M2O content) was below the detection limit (less than 0.01 mass%), the yttrium content (rare earth element content) was 1.23 mass%, and the silanol intensity ratio was 2.27.

[0098] The SEM image of the CHA-type zeolite of this comparative example is shown in Figure 4. The yttrium-containing CHA-type zeolite of this comparative example was composed of aggregated particles formed by aggregation of cubic primary particles. The average crystal size of the yttrium-containing CHA-type zeolite of this comparative example was 0.42 μm.

[0099] The silanol intensity ratio and crystal size of the CHA-type zeolites of the examples and comparative examples are shown in the table below.

[0100] [Table 1]

[0101] The yttrium-containing CHA-type zeolite of Comparative Example 1, in which yttrium was added to CHA-type zeolite obtained by a general production method, had a higher silanol intensity ratio than the Examples. Furthermore, from Examples 2 and 3, it was found that the yttrium-containing CHA-type zeolite obtained by the production method of this embodiment, which has an SiO2 / Al2O3 ratio of 3 or more and 25 or less, has a silanol intensity ratio of 2.0 or less.

[0102] Measurement example The CHA-type zeolites of Examples 1, 2, 3, and Comparative Example 1 were mixed with an aqueous solution of copper (II) nitrate so that the Cu content (hereinafter also referred to as "Cu content") was 2.5 mass% relative to the total value of the silicon (Si) content converted into SiO2, the aluminum (Al) content converted into Al2O3, and the Cu content.The mixture was then dried at 110°C in an air atmosphere and then calcined at 550°C in an air atmosphere for 2 hours to obtain CHA-type zeolites containing copper and yttrium (rare earth element), which were used as measurement samples. (Hydrothermal durability treatment) The measurement sample was molded and pulverized to produce agglomerated particles with an agglomeration diameter of 12 to 20 mesh. 3 mL of the agglomerated particles of the measurement sample was filled into an atmospheric pressure fixed-bed flow-type reactor, and then air containing 10% by volume of moisture was passed through, and the mixture was subjected to hydrothermal durability treatment under the following conditions:

[0103] Air flow rate: 300mL / min Processing temperature: 800℃ Processing time: 16 hours (nitrogen oxide reduction rate (%)) The samples before and after the hydrothermal durability treatment were molded and crushed to form agglomerated particles with an agglomeration diameter of 12 to 20 mesh. 1.5 mL of the agglomerated particle sample was filled into an atmospheric pressure fixed-bed flow reactor, and a nitrogen oxide-containing gas was passed through the reactor while maintaining the temperature at the following measurement temperature. The nitrogen oxide concentrations at the inlet and outlet of the atmospheric pressure fixed-bed flow reactor were measured. The flow conditions for the nitrogen oxide-containing gas were as follows:

[0104] Composition of nitrogen oxide-containing gas: NO 200ppm NH3 200 ppm O2 10% by volume H2O 3% by volume N2 remainder Flow rate of nitrogen oxide-containing gas: 1.5L / min Space velocity: 60,000hr -1 Measurement temperature: 600℃, 550℃, 500℃, 400℃, 300℃, 200℃, 150℃, step temperature decrease The nitrogen oxide reduction rate was calculated from the obtained nitrogen oxide concentration using the following formula.

[0105] Nitrogen oxide reduction rate (%) ={([NOx]in-[NOx]out) / [NOx]in}×100 [NOx]in is the nitrogen oxide content of the nitrogen oxide-containing gas at the inlet of the atmospheric pressure fixed-bed flow reactor. [NOx]out is the concentration of nitrogen oxide-containing gas at the outlet of the atmospheric pressure fixed-bed flow reactor. Nitrogen oxide concentration.

[0106] The nitrogen oxide reduction rates of each measurement sample before hydrothermal durability treatment (hereinafter also referred to as "fresh sample") and each measurement sample after hydrothermal durability treatment (hereinafter also referred to as "durable sample") are shown in the table below.

[0107] [Table 2]

[0108] [Table 3]

[0109] The yttrium-containing CHA-type zeolite of the examples showed high NOx conversion rates after durability testing, especially at 600°C activity. This indicates that yttrium-containing CHA-type zeolites with an SiO2 / Al2O3 ratio of 3 to 25 and a silanol intensity ratio of 2.0 or less exhibit excellent hydrothermal stability. CHA-type zeolites with low SiO2 / Al2O3 ratios tend to experience a decrease in low-temperature activity after durability testing in a steam-containing atmosphere, while CHA-type zeolites with high SiO2 / Al2O3 ratios tend to experience a decrease in high-temperature activity. However, from the results of the examples and comparative examples of the durability test samples, it was surprising to find that even samples with high SiO2 / Al2O3 ratios, such as those in Example 2, showed high NOx conversion rates in the high-temperature range, and even samples with low SiO2 / Al2O3 ratios, such as those in Example 3, did not show any decrease in NOx conversion rates in the low-temperature range. This indicates that yttrium-containing CHA-type zeolites with an SiO2 / Al2O3 ratio of 3 or more and 25 or less and a silanol strength ratio of 2.0 or less exhibit excellent hydrothermal stability.

Claims

1. The method for producing CHA-type zeolite includes a crystallization step of crystallizing a composition containing an N,N,N-trialkylcyclohexylammonium cation source, an alumina source, a silica source, a sodium source, a rare earth element source, and water, wherein the molar ratio of silica to alumina is 8 or more and 25 or less, to obtain a crystallized product; a calcination step of calcining the crystallized product at 400°C or more and 700°C or less to obtain a calcined product; and an alkali removal step of contacting the calcined product with an ammonium salt-containing solution.

2. The method for producing CHA-type zeolite according to claim 1, wherein the composition has at least the following molar composition: SiO ２ / Al ２ O ３ Ratio: 3 or more but less than 25 TACH ＋ / SiO ２ Ratio: 0.01 or more, 0.5 or less Na / SiO ２ Ratio: 0 over 0.60 or less RE / SiO ２ Ratio: 0 over 0.05 or less H ２ O / SiO ２ Ratio: 3 or more but less than 50 OH / SiO ２ Ratio: 0.10 or more and 1.50 or less However, TACH ＋ represents an N,N,N-trialkylcyclohexylammonium cation, and RE represents a rare earth element.

3. The method for producing CHA-type zeolite according to claim 1 or 2, wherein the composition contains one or more selected from the group consisting of an N,N,N-trialkyladamantanammonium cation source, a trimethylbenzylammonium cation source, and a tetraethylammonium cation source.

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