CHA-type zeolite and method for producing the same

Abstract

The present invention provides a CHA-type zeolite crystallized from a raw material composition containing an N,N,N-trialkylcyclohexylammonium cation as a structure-directing agent, which has a low SiO2 / Al2O3 ratio and can provide a catalyst exhibiting a practical nitrogen oxide reduction rate, a method for producing the same, and at least one of these, a nitrogen oxide reduction catalyst containing the same. [Solution] The present invention provides a CHA-type zeolite having a molar ratio of silica to alumina of less than 13 and a sodium content of 100 ppm to 2000 ppm. Preferably, such a CHA-type zeolite is obtained by a manufacturing method comprising the steps of: crystallizing a composition containing at least an N,N,N-trialkylcyclohexylammonium cation, an alumina source, a silica source, a sodium source, and water, wherein the molar ratio of silica to alumina is 20 or less and the molar ratio of potassium to sodium is less than 0.05 to obtain a crystalline product; removing the N,N,N-trialkylcyclohexylammonium cation from the crystalline product; and contacting the crystalline product with an ammonium salt-containing solution having an ammonium concentration of 1% by mass or more.

Description

Technical Field

[0001] The present disclosure relates to CHA-type zeolites, and particularly to CHA-type zeolites crystallized from a raw material composition containing an N,N,N-trialkylcyclohexylammonium cation as a structure-directing agent.

Background Art

[0002] CHA-type zeolite is an artificially synthesized zeolite reported in Patent Document 1 and is widely used as a nitrogen oxide reduction catalyst and a petrochemical catalyst.

[0003] In Patent Document 1, CHA-type zeolite is crystallized using an expensive structure-directing agent such as N,N,N-trimethyl-1-adamantanium ammonium cation. On the other hand, a method for producing CHA-type zeolite using an inexpensive N,N,N-trialkylcyclohexylammonium cation as a structure-directing agent has been proposed (for example, Patent Documents 2 and 3). According to Patent Documents 2 and 3, it is disclosed that a CHA-type zeolite having a molar ratio of silica to alumina (hereinafter also referred to as "SiO2 / Al2O3 ratio") exceeding 100 (Patent Document 2) and a CHA-type zeolite having a SiO2 / Al2O3 ratio of 13 or more (Patent Document 3) can be obtained.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in the production method of CHA-type zeolites using N,N,N-trialkylcyclohexylammonium cations as a structure-directing agent, no specific CHA-type zeolites with a low SiO2 / Al2O3 ratio have been reported.

[0006] The present disclosure aims to provide a CHA-type zeolite crystallized from a raw material composition containing an N,N,N-trialkylcyclohexylammonium cation as a structure-directing agent, which has a low SiO2 / Al2O3 ratio and can provide a catalyst exhibiting a practical nitrogen oxide reduction rate, a method for producing the same, and at least one of a nitrogen oxide reduction catalyst containing the same. [Means for solving the problem]

[0007] The present inventors have found that in a method for producing CHA-type zeolite by crystallizing a composition containing N,N,N-trialkylcyclohexylammonium cation as a structure-directing agent (hereinafter also referred to as the "raw material composition"), simply reducing the SiO2 / Al2O3 ratio of the raw material composition and crystallizing it does not yield a CHA-type zeolite capable of providing a catalyst with a practical nitrogen oxide reduction rate. Furthermore, they have found that the above problem can be solved by focusing on the crystallization conditions, the post-crystallization treatment, and the relationship between the crystallization conditions and the post-crystallization treatment.

[0008] In other words, the present invention is as claimed, and the gist of this disclosure is as follows. [1] A CHA-type zeolite having a molar ratio of silica to alumina of less than 13 and a sodium content of 100 ppm to 2000 ppm. [2] The CHA-type zeolite described in [1] above, wherein the molar ratio of potassium to sodium is less than 0.05. [3] The silanol group content per unit mass of CHA-type zeolite is 0.50 × 10 20 CHA-type zeolite as described in [1] or [2] above, wherein the number of particles / g or less. [4] The CHA-type zeolite according to any one of [1] to [3] above, wherein the CHA-type zeolite is a CHA-type zeolite crystallized from a composition containing an N,N,N-trialkylcyclohexylammonium cation. [5] A CHA-type zeolite according to any one of the above [1] to [3], wherein the cation type is either ammonium type or proton type. [6] A CHA-type zeolite according to any one of [1] to [4], containing one or more metallic elements selected from the group consisting of platinum, palladium, rhodium, iron, copper, cobalt, manganese, and indium. [7] The CHA-type zeolite described in [5] above, wherein the metal element is contained in a state supported outside the zeolite framework. [8] A method for producing a CHA-type zeolite according to any one of [1] to [5] above, comprising the steps of: crystallizing a composition comprising a structure-directing agent source containing at least N,N,N-trialkylcyclohexylammonium cation, an alumina source, a silica source, a sodium source, and water, wherein the molar ratio of silica to alumina is 20 or less and the molar ratio of potassium to sodium is less than 0.05 to obtain a crystalline product; removing the N,N,N-trialkylcyclohexylammonium cation from the crystalline product; and contacting the crystalline product with an ammonium salt-containing solution having an ammonium concentration of 1% by mass or more. [9] The method for producing the product according to [8] above, wherein the N,N,N-trialkylcyclohexylammonium cation is at least one of N,N,N-dimethylethylcyclohexylammonium cation and N,N,N-methyldiethylcyclohexylammonium cation.

[10] The method for producing the composition according to [8] or [9] above, wherein the composition comprises at least an amorphous compound containing silicon and aluminum as a silica source and an alumina source, and at least one of sodium hydroxide and a halide as a sodium source.

[11] A method of manufacturing according to any one of [8] to

[10] above, wherein the crystallization temperature is greater than 150°C.

[12] The manufacturing method according to any one of [8] to

[11] above, wherein the composition comprises at least an amorphous aluminosilicate.

[13] A nitrogen oxide reduction catalyst comprising a CHA-type zeolite as described in any one of [1] to [7] above.

[14] A method for reducing nitrogen oxides using the nitrogen oxide reduction catalyst described in

[13] above. [Effects of the Invention]

[0009] This disclosure provides at least one of the following: a CHA-type zeolite crystallized from a raw material composition containing an N,N,N-trialkylcyclohexylammonium cation as a structure-directing agent, having a low SiO2 / Al2O3 ratio, and capable of providing a catalyst exhibiting a practical nitrogen oxide reduction rate; a method for producing the same; and a nitrogen oxide reduction catalyst containing the same. [Brief explanation of the drawing]

[0010] [Figure 1] SEM observation image of CHA-type zeolite from Example 1 (scale in the figure is 30 μm) [Figure 2] SEM observation image of CHA-type zeolite from Example 3 (scale in the figure is 1 μm) [Figure 3] SEM observation image of CHA-type zeolite from Example 4 (scale in the figure is 5 μm) [Modes for carrying out the invention]

[0011] The following describes an example of an embodiment of the CHA-type zeolite described herein.

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

[0013] 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). 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).

[0014] A "zeolite-like substance" is a compound in which the T atom has a regular structure mediated by oxygen, and which contains at least one atom other than metals and metalloids (hereinafter also referred to as a "nonmetallic atom") in the T atom. Phosphorus (P) is an example of a nonmetallic atom, and examples of zeolite-like substances include complex phosphorus compounds such as aluminophosphate (AlPO) and silicoaluminophosphate (SAPO).

[0015] In zeolites and zeolite-like materials, the "regular structure in which T atoms are 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. For example, the CHA structure is a skeletal structure specified by the structural code "CHA". The zeolite structure can be identified by comparing it with the XRD pattern (hereinafter also referred to as the "reference pattern") of each structure described in Collection of simulated XRD powder patterns for zeolites, Fifth revised edition (2007). In this embodiment, the skeletal structure, crystalline structure, and crystalline phase are used interchangeably.

[0016] "Aluminosilicate" is a composite oxide having a structure consisting of repeating networks of aluminum (Al) and silicon (Si) mediated by oxygen (O; skeletal oxygen). In this embodiment, aluminosilicate may also include composite oxides having a structure consisting of repeating networks of aluminum (Al) and silicon (Si) 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."

[0017] 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 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 Dispersed pseudo-Voigt function (peak shape) Background removal method: Fitting method Kα2 removal method: Kα1 / Kα2 ratio = 0.497 Smoothing method: B-Spline curve Smoothing condition: Second derivative method, σ cut-off value = 3, χ threshold value = 1.5

[0018] The composition in this embodiment, such as the molar ratio of silica to alumina, may be measured by ICP analysis using a general inductively coupled plasma optical emission spectrometer (for example, OPTIMA 7300DV, manufactured by PERKIN ELMER).

[0019] <CHA-type zeolite> The CHA-type zeolite of this embodiment is a synthetic zeolite, which is a synthetic zeolite obtained by crystallizing a raw material composition containing a structure directing agent (hereinafter also referred to as "SDA"), and further, a synthetic CHA-type zeolite crystallized from a raw material composition containing N,N,N-trialkylcyclohexylammonium cation (hereinafter also referred to as "TACH" + "). The "synthetic zeolite" in this embodiment is a term in contrast to zeolites produced naturally (natural zeolites).

[0020] The CHA-type zeolite of this embodiment has a molar ratio of silica to alumina (SiO2 / Al2O3 ratio) of less than 13, and may be 12 or less, 11 or less, or 10 or less. Despite such a low SiO2 / Al2O3 ratio, the CHA-type zeolite of this embodiment can be a catalyst and its carrier showing nitrogen oxide reduction characteristics equivalent to those of a CHA-type zeolite having a conventionally high SiO2 / Al2O3 ratio of about 22 - 24. The SiO2 / Al2O3 ratio of the CHA-type zeolite of this embodiment is preferably 6 or more, 8 or more, 9 or more, or 9.5 or more.

[0021] The CHA-type zeolite of this embodiment preferably has a sodium content of 100 ppm to 2000 ppm, more than 100 ppm, 120 ppm or more, or 200 ppm or more, and more preferably 1500 ppm or less, 1300 ppm or less, 1000 ppm or less, 800 ppm or less, or 500 ppm or less. It has been known that sodium present in synthetic CHA-type zeolites reduces properties such as heat resistance and catalytic activity. In contrast, TACH is used as the SDA. + In the crystallization of a raw material composition containing and having a low SiO2 / Al2O3 ratio, it is thought that a portion of the sodium is more easily incorporated into the zeolite structure in a state that contributes to improving the properties of the CHA-type zeolite. + CHA-type zeolite obtained by crystallizing a raw material composition containing and having a low SiO2 / Al2O3 ratio is considered to have sodium that degrades properties mainly removed and sodium that contributes to improving properties remaining, by setting its sodium content within the range of this embodiment. In other words, it is preferable that the CHA-type zeolite of this embodiment contains sodium incorporated during the crystallization process (hereinafter also referred to as "residual Na"). The sodium content in the CHA-type zeolite of this embodiment is preferably the residual Na content. It is considered that the CHA-type zeolite of this embodiment mainly contains sodium that contributes to improving properties, among the residual Na. Furthermore, the CHA-type zeolite of this embodiment does not have to contain sodium supported after the crystallization process, such as ion-exchanged sodium (hereinafter also referred to as "post-supported Na"), but it may contain post-supported Na as long as its effect is not impaired.

[0022] In this embodiment, the sodium content is the mass ratio [mass ppm] of sodium (Na) converted to Na2O relative to the dry mass of the CHA-type zeolite. The dry mass of the CHA-type zeolite is the mass of the CHA-type zeolite after treatment in air at 600°C for 1 hour.

[0023] In this embodiment, the sodium content can be determined by ICP analysis using a general inductively coupled plasma emission spectrometer (instrument name: OPTIMA7300DV, manufactured by PERKIN ELMER). Prior to compositional analysis, the sample should be dissolved in a mixed solution of hydrofluoric acid and nitric acid to prepare the measurement solution.

[0024] In this embodiment, the sodium content is particularly important as the cation type is ammonium type (NH4 type) and proton type (H + It is preferable that the value is in one of the following states, and more preferably in the ammonium state. In this embodiment, the ammonium type CHA zeolite is the CHA zeolite after ion exchange with an ammonium salt (for example, ammonium chloride: particularly ammonium chloride with an ammonium concentration of 1% by mass or more, 5% by mass or more, or 10% by mass or more, and 40% by mass or less, or 30% by mass or less), and the proton type CHA zeolite is, for example, the CHA zeolite after heat treatment of the ammonium type CHA zeolite in air at 400°C to 800°C.

[0025] The CHA-type zeolite of this embodiment may contain potassium if the molar ratio of potassium to sodium (hereinafter also referred to as the "K / Na ratio") is less than 0.05. The K / Na ratio of the CHA-type zeolite of this embodiment is preferably less than 0.05, 0.03 or less, or 0.01 or less. While it is preferable that the CHA-type zeolite of this embodiment is substantially potassium-free (i.e., the K / Na ratio is 0 (zero)), considering measurement errors, the K / Na ratio should be 0 or greater, greater than 0, or 0.005 or greater. Similarly, the CHA-type zeolite of this embodiment is preferably such that the molar ratio of other alkali metals (i.e., one or more selected from the group consisting of lithium, rubidium, and cesium) to sodium (hereinafter also referred to as the "M / Na ratio") is 0 or greater, greater than 0, or 0.005 or greater, and less than 0.05 or 0.01 or less.

[0026] The CHA-type zeolite of the present embodiment preferably does not contain fluorine (F) or phosphorus (P), and the fluorine and phosphorus contents of the CHA-type zeolite are each below the measurement limit (for example, the fluorine content is 1 ppm or less, the phosphorus content is 1 ppm or less, or the fluorine content and the phosphorus content are 1 ppm or less).

[0027] The CHA-type zeolite of the present embodiment is a CHA-type zeolite crystallized from a raw material composition containing a structure-directing agent, and it may be a CHA-type zeolite crystallized from a raw material composition containing TACH + as a structure-directing agent. Therefore, as long as it is a CHA-type zeolite crystallized from a raw material composition containing TACH + as a structure-directing agent, it may contain a structure-directing agent. On the other hand, from the viewpoint of use in applications such as catalysts and adsorbents, the CHA-type zeolite of this example may not contain a structure-directing agent.

[0028] The CHA-type zeolite of the present embodiment preferably has the characteristic of being crystallized from such a raw material composition. As one of such characteristics, for example, the content of silanol groups per unit mass of the CHA-type zeolite (hereinafter, also referred to as "SiOH amount") is 0.50×10 20 [[ID=1十四]]or less or 0.30×10 20 or less per g. The silanol group is formed on silicon (Si) existing at the terminal of the zeolite structure. Existing zeolites have terminals in the zeolite structure. Therefore, it can be exemplified that the SiOH amount of the CHA-type zeolite of the present embodiment is more than 0 per g and 0.10×10 20 or more per g.

[0029] The SiOH amount can be determined by a calibration curve method from the mass of the CHA-type zeolite and the area intensity of the peak (the peak having a peak top at 2.0±0.4 ppm) attributed to the silanol group in the 1 27Al MAS NMR spectrum of the CHA-type zeolite.

[0030] The mass of the CHA-type zeolite used in calculating the SiOH content is the mass after physically adsorbed water has been removed, for example, the mass of the CHA-type zeolite after the pretreatment described later.

[0031] 1 The following conditions can be used to measure H MAS NMR spectra.

[0032] Resonance frequency: 400MHz Pulse width: π / 2 Measurement waiting time: 10 seconds Total number of times: 32 Rotation frequency: 15kHz Shift reference: TMS (tetramethylsilane) 1 H MAS NMR spectra can be measured using a standard NMR instrument (e.g., VNMRS-400, manufactured by Varian).

[0033] NMR spectra can be analyzed by performing waveform separation using a Gaussian function and determining the area intensity of the peak with its peak top at 2.0 ± 0.4 ppm. Waveform separation can be performed using common NMR spectrum analysis software (e.g., GRAMS / AI Ver. 8.0, Thermo Fisher).

[0034] Prior to NMR measurement, the sample is pre-treated. The pre-treatment can be any method that physically removes adsorbed water, and one example is holding the sample at 400°C for 5 ± 2 hours under a vacuum atmosphere.

[0035] Furthermore, prior to measurement, a calibration curve can be prepared using benzene as a standard substance. The calibration curve is prepared from three or more standard samples (e.g., 3 to 5 samples) with different amounts of benzene ranging from 0 mmol to 0.02 mmol (e.g., 0 mmol, 0.01 mmol, and 0.02 mmol). NMR measurements are performed on each standard sample under the above conditions, and the correlation between the amount of protons in each standard sample and the area intensity of the spectrum is plotted to create a calibration curve that converts area intensity to proton amount.

[0036] The amount of SiOH can be determined as the amount of protons [ions / g] relative to the mass of the CHA-type zeolite.

[0037] The CHA-type zeolite in this embodiment is preferably a single phase with a CHA structure, and further preferably has an XRD pattern similar to that of SSZ-13.

[0038] The CHA-type zeolite of this embodiment includes at least one of the following: crystalline particles formed from individual primary particles, and crystalline particles (aggregates) formed by the chemical aggregation of primary particles. The shape of the crystalline particles of this embodiment is arbitrary. Examples of crystalline particles of the CHA-type zeolite of this embodiment include at least one selected from the group consisting of crystalline particles having either a rhombohedron or a cube (a six-sided polyhedron with all sides of equal length), polyhedral crystalline particles that include some faces of primary particles having at least one of the shapes of a rhombohedron or a cube, and amorphous crystalline particles. The crystalline particles of the CHA-type zeolite of this embodiment may also be crystalline particles that do not have some faces of primary particles having at least one of the shapes of a rhombohedron or a cube, and may include, for example, amorphous crystalline particles that are close to spherical, and even substantially spherical crystalline particles. Examples include crystal particle diameters (hereinafter also referred to as "crystal particle size") of 0.1 μm or more or 0.3 μm or more, or 2 μm or less or 1 μm or less. The CHA-type zeolite of this embodiment preferably contains crystal particles of at least 0.1 μm or more or 0.5 μm or more, and 1 μm or less or 0.8 μm or less. Furthermore, the CHA-type zeolite of this embodiment preferably uses crystal particles with a crystal particle diameter of 0.1 μm or more or 0.5 μm or more, and 1 μm or less or 0.8 μm or less as the matrix (premium phase).

[0039] Furthermore, the CHA-type zeolite of this embodiment may be in a state in which crystalline particles are dispersed, or it may be in a state in which two or more crystalline particles are physically aggregated to form agglomerates, or it may contain agglomerates, or it may be composed of agglomerates. The shape of the agglomerates may be irregular, and the diameter of the agglomerates may be 5 μm or more or 10 μm or more, or 100 μm or less or 70 μm or less, as examples.

[0040] Crystal particles are the smallest particles observable in SEM observation at magnifications of 30 to 20,000x, and the crystal particle diameter can be determined by measuring the longest length observed in the SEM observation. Similarly, the aggregated particle diameter can be determined by measuring the longest length of the aggregated particles formed from crystal particles.

[0041] The CHA-type zeolite of this embodiment may contain an active metal element. The active metal element is preferably a transition metal element, and may be one or more elements selected from groups 8, 9, 10, and 11 of the periodic table, one or more selected from the group of platinum (Pt), palladium (Pd), rhodium (Rh), iron (Fe), copper (Cu), cobalt (Co), manganese (Mn), and indium (In), one or more metal elements selected from the group of cobalt (Co), nickel (Ni), iron (Fe), and copper (Cu), at least one of iron and copper, or copper.

[0042] It is preferable that the active metal element is contained in a state other than that of a T atom, for example, supported outside the zeolite framework, such as being supported in at least one of the pores and ion exchange sites.

[0043] The CHA-type zeolite of this embodiment may have an active metal element content of 2.5% by mass or more, 3.0% by mass or more, or 3.5% by mass or more, and 6.5% by mass or less, 6.0% by mass or less, or 5.5% by mass or less.

[0044] The CHA-type zeolite of the present embodiment can be applied to known uses of zeolites, such as catalysts, adsorbents, and carriers thereof, and further can be used as a nitrogen oxide reduction catalyst and its carrier, and still further can be used as a nitrogen oxide reduction catalyst. Further, the nitrogen oxide reduction catalyst can be subjected to a nitrogen oxide reduction method using the same. Furthermore, the CHA-type zeolite of the present embodiment can be used as an exhaust gas purification catalyst, still further as an exhaust gas treatment catalyst for an internal combustion engine, and still further as an automobile exhaust gas treatment catalyst, and can also be used as these carriers. <Method for Producing CHA-Type Zeolite> The method for producing a CHA-type zeolite of the present embodiment includes a step of crystallizing a composition containing at least a structure-directing agent source containing N,N,N-trialkylcyclohexylammonium cation, an alumina source, a silica source, a sodium source, and water, having a molar ratio of silica to alumina of 20 or less and a molar ratio of potassium to sodium of less than 0.05 to obtain a crystallized product, a step of removing N,N,N-trialkylcyclohexylammonium cation from the crystallized product, and a step of contacting the crystallized product with an ammonium salt-containing solution having an ammonium concentration of 1% by mass or more. (Crystallization Step) It is considered that the CHA-type zeolite crystallizes while a part of sodium (Na) is incorporated in a state of improving the characteristics of the CHA-type zeolite by crystallizing a composition (hereinafter also referred to as "raw material composition") containing at least a structure-directing agent source containing N,N,N-trialkylcyclohexylammonium cation, an alumina source, a silica source, a sodium source, and water, having a molar ratio of silica to alumina of 20 or less and a molar ratio of potassium to sodium of less than 0.05 (hereinafter also referred to as "crystallization step").

[0045] The crystalline product obtained in the crystallization process tends to have a lower SiO2 / Al2O3 ratio than the raw material composition. To crystallize the CHA-type zeolite of this embodiment, the molar ratio of silica to alumina in the raw material composition (SiO2 / Al2O3 ratio) is 20 or less, preferably 15 or less, less than 13, 11 or less, or 10 or less. Furthermore, the SiO2 / Al2O3 ratio may be 3 or more, 5 or more, or 8 or more.

[0046] The raw material composition has a molar ratio of potassium to sodium (K / Na ratio) of less than 0.05, preferably 0.03 or less, or 0.01 or less, and preferably a K / Na ratio of 0 (i.e., no potassium). In raw material compositions using N,N,N-trialkylcyclohexylammonium cation as a structure directing agent and with an SiO2 / Al2O3 ratio of around 20, increasing the K / Na ratio makes it easier for CHA-type zeolite to crystallize. In contrast, in raw material compositions using N,N,N-trialkylcyclohexylammonium cation as a structure directing agent and with an SiO2 / Al2O3 ratio of 15 or less, where the SiO2 / Al2O3 ratio is particularly low, a high K / Na ratio tends to generate by-phases with zeolite structures other than the CHA structure, making it difficult to obtain CHA-type zeolite as a single phase. However, by keeping the K / Na ratio within this range, the formation of by-phases, especially ERI-type zeolite, is suppressed, and single-phase CHA-type zeolite can be obtained.

[0047] 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 hydroxide, aluminum chloride, amorphous aluminosilicate, metallic aluminum, crystalline aluminosilicate, and aluminum alkoxide. Furthermore, amorphous aluminum compounds, at least one of aluminum hydroxide and amorphous aluminosilicate, and even more preferably amorphous aluminosilicate are used.

[0048] 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 amorphous aluminosilicate being preferred.

[0049] The raw material composition preferably includes at least an amorphous alumina source and a silica source, and further preferably at least an amorphous aluminosilicate. By not including crystalline aluminosilicate as the alumina source and silica source, the raw material composition tends to have lower manufacturing costs and is industrially advantageous.

[0050] Sodium sources include sodium-containing salts or compounds. These include one or more selected from the group consisting of sodium chloride, iodide, bromide, hydroxide, and oxide, and more specifically, one or more selected from the group consisting of sodium chloride, bromide, and hydroxide, and more specifically, sodium hydroxide. Sodium contained in other starting materials can also be considered a sodium source. The raw material composition preferably contains at least sodium hydroxide.

[0051] The raw material composition may also contain, in a sufficiently small amount relative to sodium, one or more alkali metals other than sodium, i.e., one selected from the group consisting of potassium, rubidium, and cesium, and furthermore, potassium.

[0052] The structure-directing agent source is at least N,N,N-trialkylcyclohexylammonium cation (TACH + ) contains. TACH +It functions as a so-called structure-directing agent (hereinafter also referred to as "SDA") that directs to the CHA structure. The SDA source is a salt containing SDA, and examples include one or more selected from the group of hydroxides, halides, monocarbonate salts and monosulfate salts of SDA, one or more selected from the group of hydroxides, chlorides, bromides and iodides, one or more selected from the group of hydroxides, bromides and iodides, at least one of hydroxides and bromides, or hydroxide.

[0053] TACH included in the SDA source + This is N,N,N-trimethylcyclohexylammonium cation (hereinafter referred to as "TMCH") + It is also called "DMECH." ), N,N,N-dimethylethylcyclohexylammonium cation (hereinafter referred to as "DMECH") + Also called "MDECH + ) and N,N,N-triethylcyclohexylammonium cation (hereinafter referred to as "TECH + It is also called ". ) One or more selected from the group DMECH + and MDECH + At least one of the above, or DMECH + For example, in order to crystallize the CHA-type zeolite having the SiO2 / Al2O3 ratio of this embodiment, the SDA source contains TACH + , TMCH + Other TACH + It is preferable that DMECH + and MDECH + At least one of the above, and furthermore, DMECH + It is preferable that this be the case.

[0054] The SDA contained in the raw material composition is TACH + (TACH + (only), and furthermore, DMECH + , MDECH + and TECH + One or more selected from the group, and furthermore, DMECH + and MDECH +At least one of the above, and furthermore, DMECH + (DMECH + It is sufficient if only (that). On the other hand, the raw material composition is an SDA that is directed toward a CHA structure, and TACH + Other substances (hereinafter also referred to as "Add-SDA") may be included. As Add-SDA, N,N,N-trialkyladamantanammonium cation (hereinafter referred to as "TAad") may be included. + It is also called ), one or more selected from the group consisting of trimethylbenzylammonium cation and tetraethylammonium cation, etc. Specific examples of Add-SDA include TAad + Furthermore, N,N,N-trimethyladamantan ammonium cations are also mentioned. When Add-SDA is included, the raw material composition is TACH + It is preferable that these be included in a smaller proportion.

[0055] Primarily TMCH + Due to the structure-directing effect, CHA-type zeolite is crystallized, and the TMCH of the raw material composition + The molar ratio of Add-SDA to (hereinafter also referred to as the "Add-SDA / SDA ratio") may be 1 or less, less than 1, 0.5 or less, or 0.4 or less. The raw material composition does not need to contain Add-SDA, and the Add-SDA / SDA ratio may be 0 (zero), but it may also contain Add-SDA, and the Add-SDA / SDA ratio may be greater than 0 or 0.05 or greater.

[0056] The water contained in the raw material composition may be deionized water, pure water, structural water, water as a solvent, or water (H2O) contained in other starting materials.

[0057] The raw material composition preferably does not contain fluorine (F) or phosphorus (P), and the fluorine and phosphorus content of the raw material composition is below the detection limit, respectively (for example, fluorine content of 1 ppm or less, phosphorus content of 1 ppm or less, or fluorine and phosphorus content of 1 ppm or less).

[0058] The raw material composition preferably includes at least an amorphous compound containing silicon and aluminum as a silica source and an alumina source, and at least one of sodium hydroxide and a halide as a sodium source. TMCH + In a raw material composition containing SDA, it is believed that the coexistence of the SDA, an amorphous compound containing silicon and aluminum such as amorphous aluminosilicate, and at least one of sodium hydroxide or halide, which are sodium salts, allows for the crystallization of CHA-type zeolite without sodium being unevenly distributed. As a result, compared to the crystallization of raw material compositions containing individual substances as alumina and silica sources, it is believed that the crystallization occurs in a state where sodium, which can degrade the properties of zeolite such as sodium that inhibits gas diffusion, is more easily removed.

[0059] The following molar compositions are considered preferred compositions of the raw material composition. In the following molar compositions, SDA is TACH + And, TACH + DMECH + The SDA / SiO2 ratio in cases such as DMECH + The ratio can be considered as the (K+Cs) / SiO2 ratio, etc. Furthermore, if M is an alkali metal other than sodium, and the raw material composition contains two or more alkali metals other than sodium (for example, potassium and cesium), the M / SiO2 ratio can be considered as the (K+Cs) / SiO2 ratio, etc. In addition, each composition ratio in the molar composition may be any combination of the upper and lower limits described below. SiO2 / Al2O3 ratio = 3 or more, 5 or more, or 8 or more, 20 or younger, 15 or younger, less than 13, 11 or younger, or 10 or younger SDA / SiO2 ratio = 0.01 or higher, 0.02 or higher, 0.05 or higher, or 0.075 or higher, 0.5 or less, 0.3 or less, 0.2 or less, or 0.1 or less Add-SDA / SDA ratio = 0 or greater, greater than 0, or 0.05 or greater, 1 or less, 0.5 or less, or 0.4 or less Na / SiO2 ratio = greater than 0, 0.1 or greater, or 0.2 or greater, 0.60 or less, 0.5 or less, 0.4 or less, or 0.3 or less K / Na ratio = 0 or greater, 0.001 or greater, or 0.005 or greater, Less than 0.05, 0.03 or less, or 0.01 or less M / Na ratio = 0 or greater, 0.001 or greater, or 0.005 or greater, Less than 0.05, 0.03 or less, or 0.01 or less H2O / SiO2 ratio = 3 or more, 5 or more, 10 or more, or 15 or more, 50 or under, 30 or under, 20 or under, or 19 or under

[0060] To promote the crystallization of CHA-type zeolite, seed crystals may be mixed into the raw material composition. The seed crystals may be one or more selected from the group consisting of AEI-type zeolite, AFX-type zeolite, ERI-type zeolite, CHA-type zeolite, LEV-type zeolite, and OFF-type zeolite, and CHA-type zeolite is an example. The seed crystals mixed into the raw material composition may have a ratio (hereinafter also referred to as "seed crystal content") of the total mass of silicon (Si) and aluminum (Al) of the seed crystals converted to SiO2 and Al2O3, respectively, to the total mass of silicon (Si) and aluminum (Al) of the raw material composition converted to SiO2 and Al2O3, respectively, which is greater than 0% by mass, 0.5% by mass or more, or 1% by mass or more, and 10% by mass or less, 5% by mass or less, or 3% by mass or less. The raw material composition may not contain seed crystals, i.e., the seed crystal content may be 0% by mass.

[0061] In the crystallization process, the raw material composition is crystallized. Any method that causes the raw material composition to crystallize is acceptable, and hydrothermal synthesis is a suitable method. The following conditions are examples of conditions for hydrothermal synthesis. Crystallization temperature: 130°C or higher, 140°C or higher, greater than 150°C or greater than 155°C, Below 200℃, below 180℃, or below 170℃ Crystallization time: 1 hour or more, 10 hours or more, or 24 hours or more, 7 days or less, 5 days or less, 3 days or less, or 2 days or less Crystallization state: At least one of the following: stirred state and / or standing state, or stirred state. Crystallization pressure: Autoclavation pressure For example, when crystallizing a CHA-type zeolite with an SiO2 / Al2O3 ratio of less than 10, if the crystallization temperature is above 150°C or above 155°C, and below 180°C or below 170°C, then a single-phase CHA-type zeolite can be crystallized in two days or less.

[0062] (SDA removal process) From crystallized TACH + In the process of removing (hereinafter also referred to as the "SDA removal process"), TACH is performed using any method. + It is sufficient to remove it from the crystalline form (CHA-type zeolite).

[0063] SDA removal is performed from crystalline TACH + Any method capable of removing SDA is acceptable. Examples of SDA removal methods include calcination and acid treatment, with calcination being preferred. Calcination may involve treating CHA-type zeolite in one or more atmospheres selected from the group consisting of an oxidizing atmosphere, an inert atmosphere, and a reducing atmosphere, at a temperature of 300°C or higher, or 400°C or higher, and 600°C or lower, or 500°C or lower. Particularly preferred calcination methods include calcination in air at 300°C to 600°C. The calcination (and acid treatment) time can be exemplified as 1 hour to 5 hours, but may be appropriately changed depending on the amount of crystallized material subjected to the calcination.

[0064] The crystalline material used in the SDA removal process may be any material recovered after the crystallization process by solid-liquid separation or the like, but it may also be material that has been washed and dried.

[0065] The crystallized material can be washed by any method after crystallization by the recovered crystallized material (CHA-type zeolite). One possible method is to wash the crystallized material obtained as a solid phase after the crystallization process with an amount of pure water such that the mass of pure water is 10 times or more the mass of the crystallized material. Drying can be carried out by any method that can physically remove moisture adsorbed onto the CHA-type zeolite. For example, the CHA-type zeolite may be treated in at least one of an oxidizing atmosphere and an inert atmosphere at a temperature of 100°C to 200°C for 2 hours or more.

[0066] (Alkali removal process) TACH + The crystallized product from which the TACH group has been removed (i.e., TACH + CHA-type zeolite (which does not contain sodium) is treated by a process of contacting the crystals with an ammonium salt-containing solution having an ammonium concentration of 1% by mass or more (hereinafter also referred to as the "alkali removal process"). By washing the crystals with such an ammonium salt-containing solution, sodium in a form that degrades the properties of CHA-type zeolite is efficiently removed, and furthermore, the removal of sodium that contributes to improving the properties of CHA-type zeolite is suppressed.

[0067] Ammonium-containing solutions are ammonium (NH4 + It contains a salt of ) and a solvent.

[0068] The solvent can be any medium in which the ammonium salt dissolves, and can be at least one of alcohol and water, and it can be water, that is, the ammonium-containing solution can be an aqueous solution containing ammonium.

[0069] Ammonium salts are 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.

[0070] The ammonium-containing solution has an ammonium concentration (NH4 +The concentration is 1% by mass or more, preferably 2% by mass or more, 5% by mass or more, or 7% by mass or more. By treating the crystallized product (CHA-type zeolite that does not contain SDA) with such a high-concentration ammonium-containing solution, it is thought that trace amounts of alkali metals in the form of compounds such as oxides, and alkali metal ions that can be easily freed, which can degrade the properties of the CHA-type zeolite, are preferentially removed. As a result, it becomes easier to obtain a nitrogen oxide reduction catalyst or a CHA-type zeolite that can serve as a support therefor and has nitrogen oxide reduction properties equivalent to those of a CHA-type zeolite with an SiO2 / Al2O3 ratio of about 22-24. The ammonium concentration in the ammonium-containing solution should be below the saturation concentration, and may be 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less.

[0071] In order to leave an appropriate amount of sodium (residual Na) in the CHA-type zeolite after the alkali removal process, and furthermore to remove sodium which tends to degrade the properties of the CHA-type zeolite, the ratio of the mass of the ammonium-containing solution to the mass of the crystalline product (CHA-type zeolite that does not contain 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.

[0072] Post-crystallization treatments, such as the removal of SDA, tend to reduce the crystallinity of CHA-type zeolite. Therefore, the crystallinity of CHA-type zeolite after alkali removal (hereinafter also referred to as "crystallinity retention rate") relative to CHA-type zeolite (as-synthesized) after the crystallization process is 100% or less, 95% or less, 90% or less, or 86% or less. On the other hand, a crystallinity retention rate of 76.5% or more, 78% or more, or 80% or more is preferable. The crystallization retention rate can be determined from the ratio of the peak heights of the XRD peaks corresponding to the CHA-type zeolite (20-1) planes after the crystallization process and after the alkali removal process (CHA-type zeolite after alkali removal / CHA-type zeolite after crystallization process; %). Alternatively, the peak with its peak top at 2θ = 20.7 ± 0.2° can be considered as the XRD peak corresponding to the CHA-type zeolite (20-1) plane.

[0073] (Metal-containing process) When the CHA-type zeolite in this embodiment is a metal-containing CHA-type zeolite, the manufacturing 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 "metal-containing step"). This yields a metal-containing CHA-type zeolite (or metal-supported CHA-type zeolite).

[0074] In the metal-containing process, an arbitrary active metal element is added to the CHA-type zeolite after alkali removal, preferably an arbitrary transition metal element is supported on the CHA-type zeolite. The metal-containing method can be any method by which the CHA-type zeolite and the active metal source come into contact so that the active metal element is included as an atom other than the T atom of the CHA-type zeolite. For example, one or more methods can be selected from the group consisting of ion exchange, impregnation, evaporation to dryness, precipitation, and physical mixing, with impregnation being preferred. The active metal source is at least one of a salt and / or compound containing an 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, or one or more selected from the group consisting of nitrates, sulfates, and chlorides.

[0075] Preferably, the active metal element is a transition metal element, further selected from the groups 8, 9, 10, and 11 of the periodic table, further selected from the group of platinum (Pt), palladium (Pd), rhodium (Rh), iron (Fe), copper (Cu), cobalt (Co), manganese (Mn), and indium (In), and further selected from the group of iron and copper, or copper.

[0076] The manufacturing method of this embodiment may include, if necessary, a step of calcining the metal-containing CHA-type zeolite. Impurities are removed by calcination. The calcination method is arbitrary, but examples include treatment in one or more atmospheres selected from the group of oxidizing atmosphere, inert atmosphere and reducing atmosphere at 100°C to 600°C, and treatment in air at 400°C to 600°C is preferable. [Examples]

[0077] The embodiments of this model will be described below with reference to examples. However, the embodiments are not limited to these examples.

[0078] (Zeolite structure) XRD measurements of the sample were performed using a 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

[0079] The obtained XRD patterns were analyzed using the analysis software included with the instrument (software name: Smart Lab Studio II, manufactured by Rigaku Corporation) under the following conditions. 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 The zeolite structure was identified by comparing the analyzed XRD pattern with a reference pattern.

[0080] (Crystallization maintenance rate) The crystallinity retention rate is the percentage [%] of the peak height of the XRD peak corresponding to the (20-1) plane of the CHA structure in the CHA-type zeolite after ion exchange, washing, and drying, compared to the crystalline product (CHA-type zeolite) after recovery, washing, and drying from the crystallinity process. The XRD peak corresponding to the (20-1) plane was obtained by the same XRD measurement as the (zeolite structure), and was defined as a peak with a peak top at 2θ = 20.7 ± 0.2°.

[0081] (composition analysis) The composition of the sample was analyzed using a standard 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 then analyzed using the obtained measurement solution.

[0082] (SiOH amount) 1 The silanol group content of CHA-type zeolite was measured by H MAS NMR. Prior to measurement, the sample was pretreated by dehydrating it under a vacuum atmosphere at 400°C for 5 hours. After pretreatment, the sample was cooled to room temperature, collected under a nitrogen atmosphere, and weighed. A general-purpose NMR spectrometer (instrument name: VNMRS-400, manufactured by Varian) was used for measurement. The measurement conditions were as follows: Resonance frequency: 399.8MHz Pulse width: π / 2 Measurement waiting time: 10 seconds Total number of times: 32 Rotation frequency: 15kHz Shift reference: TMS (tetramethylsilane) obtained 1 From the H MAS NMR spectrum, the peak with a peak top at 2.0 ± 0.4 ppm was attributed to the silanol group. This peak was separated using spectral analysis software (GRAMS / AI Ver. 8.0, Thermo Fisher), and then its area intensity was determined. A calibration curve was created using benzene as the standard substance. From the area intensity of the NMR spectrum attributed to the silanol group, the amount of protons originating from the silanol group in the sample was determined using the calibration curve method, and the amount of OOH was determined from this amount of protons and the mass of the weighed sample.

[0083] Example 1 Mixing a 35% by mass DMECHAOH aqueous solution, a 48% by mass sodium hydroxide aqueous solution, water, and amorphous aluminosilicate (SiO2 / Al2O3=8.9) yields the following molar composition A raw material composition having the following properties was obtained. SiO2 / Al2O3 = 8.9 DMECH + / SiO2=0.08 Na / SiO2 = 0.27 H2O / SiO2 = 18 OH / SiO2 = 0.35

[0084] To the obtained raw material composition, CHA-type zeolite was added and mixed in an amount of 2.0% by mass as seed crystals. This mixture was then packed into a sealed container and subjected to hydrothermal treatment at 160°C for 48 hours to obtain a crystalline product consisting of a single phase of CHA-type zeolite. The obtained crystalline product was recovered by solid-liquid separation, washed with a sufficient amount of pure water, dried in the air, and then calcined at 600°C to obtain CHA-type zeolite.

[0085] The calcined CHA-type zeolite consisted of a single phase of CHA-type zeolite, containing sodium as an alkali metal, with a Na / Al ratio of 0.87.

[0086] The CHA-type zeolite and ammonium (NH4 +Ion exchange was performed by mixing with a 20% by mass aqueous solution of ammonium chloride. The amount of ammonium chloride aqueous solution used for ion exchange was 4.5 times the mass of the CHA-type zeolite (NH4 / CHA = 4.5). After ion exchange, the zeolite was washed with pure water and dried to obtain the CHA-type zeolite of this example. The CHA-type zeolite of this example (a CHA-type zeolite with an ammonium cation type) had an SiO2 / Al2O3 ratio of 8.7 and a sodium content of 400 ppm. Potassium was below the detection limit.

[0087] Figure 1 shows an SEM observation of the CHA-type zeolite of this embodiment. The CHA-type zeolite of this embodiment was composed of aggregated particles, which were formed by the aggregation of crystalline particles lacking some faces of primary particles having at least one of the shapes of a rhombohedron or a cube. Furthermore, the crystalline particles had a particle diameter of 0.5 μm to 1 μm, and the aggregated particle diameter of the main aggregated particles was 50 μm to 70 μm.

[0088] Example 2 Crystallization, washing, drying, and calcination were carried out in the same manner as in Example 1, except that a raw material composition having the following molar composition was used, obtained by mixing a 35% by mass DMECHAOH aqueous solution, a 48% by mass sodium hydroxide aqueous solution, water, and amorphous aluminosilicate (SiO2 / Al2O3=10.6). SiO2 / Al2O3 = 10.6 DMECH + / SiO2=0.08 Na / SiO2 = 0.29 H2O / SiO2 = 18 OH / SiO2 = 0.37

[0089] The calcined CHA-type zeolite consisted of a single phase of CHA-type zeolite, containing sodium as an alkali metal, with a Na / Al ratio of 0.79.

[0090] The CHA-type zeolite was subjected to ion exchange, washing, and drying in the same manner as in Example 1 to obtain the CHA-type zeolite of this example. The CHA-type zeolite of this example had an SiO2 / Al2O3 ratio of 9.6, a sodium content of 700 ppm, and an OHCl content of 0.30 × 10⁻⁶. 20 It was pieces / gram.

[0091] Example 3 Crystallization, washing, drying, and calcination were carried out in the same manner as in Example 1, except that a raw material composition having the following molar composition was used, obtained by mixing a 35% by mass DMECHAOH aqueous solution, a 25% by mass TMAdOH aqueous solution, a 48% by mass sodium hydroxide aqueous solution, water, and amorphous aluminosilicate (SiO2 / Al2O3=10.6). SiO2 / Al2O3 = 10.6 DMECH + / SiO2=0.06 TMAd + / SiO2=0.02 Na / SiO2 = 0.29 H2O / SiO2 = 18 OH / SiO2 = 0.37

[0092] The CHA-type zeolite after calcination consisted of a single phase of CHA-type zeolite, containing sodium as an alkali metal, with a Na / Al ratio of 0.82.

[0093] The CHA-type zeolite was subjected to ion exchange, washing, and drying in the same manner as in Example 1 to obtain the CHA-type zeolite of this example. The CHA-type zeolite of this example had an SiO2 / Al2O3 ratio of 9.9 and a sodium content of 140 ppm.

[0094] Figure 2 shows an SEM observation of the CHA-type zeolite of this embodiment. The CHA-type zeolite of this embodiment was composed of aggregated particles, which were formed by the aggregation of crystalline particles lacking some faces of primary particles having at least one of the shapes of a rhombohedron or a cube. Furthermore, the crystalline particles had a particle diameter of 0.5 μm to 1 μm.

[0095] Example 4 Crystallization, washing, drying, and calcination were carried out in the same manner as in Example 1, except that a raw material composition having the following molar composition was used, obtained by mixing a 35% by mass DMECHAOH aqueous solution, a 48% by mass sodium hydroxide aqueous solution, water, and amorphous aluminosilicate (SiO2 / Al2O3=12.8), and the crystallization time was set to 72 hours. SiO2 / Al2O3 = 12.8 DMECH + / SiO2=0.17 Na / SiO2 = 0.35 H2O / SiO2 = 18 OH / SiO2 = 0.52

[0096] The calcined CHA-type zeolite consisted of a single phase of CHA-type zeolite, containing sodium as an alkali metal, with a Na / Al ratio of 0.77.

[0097] The CHA-type zeolite was subjected to ion exchange, washing, and drying in the same manner as in Example 1 to obtain the CHA-type zeolite of this example. The CHA-type zeolite of this example had a sodium content of 300 ppm, an SiO2 / Al2O3 ratio of 9.7, and an SiOH content of 0.27 × 10⁻¹⁶. 20 It was pieces / gram.

[0098] Figure 3 shows an SEM observation of the CHA-type zeolite of this embodiment. The CHA-type zeolite of this embodiment was mainly composed of crystalline particles lacking some faces of primary particles having at least one of the shapes of a rhombohedron or a cube, and the crystalline particles were dispersed. The crystalline particles had a particle diameter of 0.5 μm to 1 μm.

[0099] Example 5 CHA-type zeolite was obtained by crystallization, washing, drying, and calcination in the same manner as in Example 2.

[0100] The CHA-type zeolite and ammonium (NH4 +Ion exchange was performed by mixing with a 10% by mass aqueous solution of ammonium chloride. The amount of ammonium chloride aqueous solution used for ion exchange was 1.3 times the mass of the CHA-type zeolite (NH4 / CHA = 1.3). After ion exchange, the zeolite was washed with pure water and dried to obtain the CHA-type zeolite of this example. The CHA-type zeolite of this example had an SiO2 / Al2O3 ratio of 9.6 and a sodium content of 1270 ppm.

[0101] Comparative Example 1 CHA-type zeolite was obtained by crystallization, washing, drying, and calcination in the same manner as in Example 2.

[0102] Ion exchange was performed by mixing the CHA-type zeolite with an aqueous solution of ammonium chloride with an ammonium concentration of 0.6% by mass. The amount of aqueous solution of ammonium chloride used for ion exchange was 6.6 times the mass of the CHA-type zeolite (NH4 / CHA = 6.6). After ion exchange, the mixture was washed with pure water and dried to obtain the CHA-type zeolite of this comparative example. The CHA-type zeolite of this comparative example had an SiO2 / Al2O3 ratio of 9.8 and a Na content of 11,600 ppm.

[0103] Comparative Example 2 CHA-type zeolite was obtained by crystallization, washing, drying, and calcination in the same manner as in Example 4.

[0104] Ion exchange was performed by mixing the CHA-type zeolite with a 7.1% hydrochloric acid aqueous solution. The amount of 7.1% hydrochloric acid aqueous solution used for ion exchange was 2.5 times the mass of the CHA-type zeolite (NH4 / CHA=0). After ion exchange, the mixture was washed with pure water and dried to obtain the CHA-type zeolite of this comparative example. The CHA-type zeolite of this comparative example had an SiO2 / Al2O3 ratio of 9.9 and a Na content of 100 ppm.

[0105] Comparative Example 3 A raw material composition having the following molar composition was obtained by mixing a 35% by mass DMECHAOH aqueous solution, a 48% by mass sodium hydroxide aqueous solution, a 48% by mass potassium hydroxide aqueous solution, and amorphous aluminosilicate (SiO2 / Al2O3 = 10.6). SiO2 / Al2O3 = 10.6 DMECH + / SiO2=0.08 Na / SiO2 = 0.275 K / Na = 0.055 H2O / SiO2 = 18 OH / SiO2 = 0.37

[0106] Seed crystals were mixed and crystallized in the same manner as in Example 1, except that the obtained raw material composition was used. The resulting crystalline product was a mixture of CHA-type zeolite and ERI-type zeolite, and a single phase of CHA-type zeolite was not obtained.

[0107] The results for the examples and comparative examples are shown in the table below.

[0108] [Table 1]

[0109] In all of the CHA-type zeolites in the examples, the Na / Al ratio was 0.05 or less, and even 0.01 or less, confirming that the Na content was reduced compared to the CHA-type zeolite after calcination. Furthermore, from Comparative Example 1, it can be seen that the CHA-type zeolite subjected to ion exchange with a low-concentration NH4Cl aqueous solution showed a reduction in Na content and a low crystallinity retention rate, indicating that crystallinity was significantly reduced by ion exchange. Furthermore, from Comparative Example 2, it can be seen that while ion exchange with hydrochloric acid, a strong acid, did not reduce crystallinity, the reduction in Na was excessive, meaning that even the Na that could contribute to improving properties was removed.

[0110] Measurement example The CHA-type zeolites obtained in Examples 2, 3, and 5, and Comparative Examples 1 and 2, were each mixed in a mortar for 10 minutes after adding an aqueous copper nitrate solution dropwise. After mixing, they were dried overnight in the air at 110°C, and then calcined in the air at 550°C for 1 hour to obtain metal-containing CHA-type zeolites (copper-supported CHA-type zeolites) with 4.6% by mass of copper supported.

[0111] (Hydrothermal resistant treatment) Copper-supported CHA-type zeolite was molded and crushed to produce aggregated particles with an aggregation diameter of 12 to 20 mesh. 3 mL of the aggregated particles was packed into a fixed-bed flow-through reaction tube at atmospheric pressure (hereinafter also simply referred to as the "reaction tube"), and then subjected to hydrothermal endurance treatment under the following conditions. Processing atmosphere: Air circulation atmosphere with a moisture content of 10% by volume. Air circulation rate: 300 mL / min Processing temperature: 800℃ Processing time: 16 hours

[0112] (Nitrogen oxide reduction rate) 1.5 mL of aggregated particles after hydrothermal treatment were packed into a reaction tube, and nitrogen oxide-containing gas was circulated while maintaining the temperature as described below. The nitrogen oxide concentrations at the inlet and outlet of the reaction tube were then measured. The conditions for circulating the nitrogen oxide-containing gas were as follows.

[0113] 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: 60,000hr -1 Measurement temperature: 150°C or 600°C

[0114] The nitrogen oxide reduction rate (NOx reduction rate) was calculated from the obtained nitrogen oxide concentration using the following formula. Nitrogen oxide reduction rate (%) ={([NOx]in-[NOx]out) / [NOx]in}×100 [NOx]in is the nitrogen oxide concentration of the nitrogen oxide-containing gas at the inlet of the reaction tube, and [NOx]out is the nitrogen oxide concentration of the nitrogen oxide-containing gas at the outlet of the reaction tube.

[0115] [Table 2]

[0116] Example 3 is a copper-supported CHA-type zeolite in which copper is supported on a CHA-type zeolite with a sodium content of 140 ppm, while Comparative Example 2 is a copper-supported CHA-type zeolite in which copper is supported on a CHA-type zeolite with a sodium content of 100 ppm. Despite the difference in sodium content being only 40 ppm, it was confirmed that the nitrogen oxide reduction rate of the copper-supported CHA-type zeolite of Comparative Example 2 was lower than that of the copper-supported CHA-type zeolite of Example 3 at both low temperatures (150°C) and high temperatures (600°C), with the nitrogen oxide reduction rate at low temperatures being approximately 0.5 times lower.

[0117] Furthermore, CHA-type zeolites with an SiO2 / Al2O3 ratio of 10 or less show a significant decrease in nitrogen oxide reduction rate with decreasing SiO2 / Al2O3. However, the copper-supported CHA-type zeolite of Example 2 (SiO2 / Al2O3=9.6) was found to have a higher nitrogen oxide reduction rate at both low temperatures (150°C) and high temperatures (600°C) compared to the copper-supported CHA-type zeolite of Comparative Example 2 (SiO2 / Al2O3=9.9).

[0118] Furthermore, it was confirmed that copper-supported CHA-type zeolite, which is obtained by supporting copper on CHA-type zeolite with a sodium content exceeding 1% by mass, has a higher SiO2 / Al2O3 ratio compared to the copper-supported CHA-type zeolite of Example 2, but its nitrogen oxide reduction rate at both low and high temperatures is lower.

Claims

1. A CHA-type zeolite having a molar ratio of silica to alumina of less than 13 and a sodium content of 100 ppm to 2000 ppm.

2. The CHA-type zeolite according to claim 1, wherein the molar ratio of potassium to sodium is less than 0.

05.

3. The silanol group content per unit mass of CHA-type zeolite is 0.30 × 10⁻⁶. ２０ The CHA-type zeolite according to claim 1 or 2, wherein the number of particles / g or less.

4. A method for producing a CHA-type zeolite according to any one of claims 1 to 3, comprising the steps of: crystallizing a composition comprising a structure-directing agent source containing at least N,N,N-trialkylcyclohexylammonium cation, an alumina source, a silica source, a sodium source, and water, wherein the molar ratio of silica to alumina is 20 or less and the molar ratio of potassium to sodium is less than 0.05 to obtain a crystalline product; removing the N,N,N-trialkylcyclohexylammonium cation from the crystalline product; and contacting the crystalline product with an ammonium salt-containing solution having an ammonium concentration of 1% by mass or more.

5. The manufacturing method according to claim 4, wherein the crystallization temperature is greater than 150°C.

6. The manufacturing method according to claim 4 or 5, wherein the composition comprises at least an amorphous aluminosilicate.

7. The production method according to claim 4 to 6, wherein the N,N,N-trialkylcyclohexylammonium cation is at least one of N,N,N-dimethylethylcyclohexylammonium cation and N,N,N-methyldiethylcyclohexylammonium cation.

8. The manufacturing method according to claim 4 or 5, wherein the composition comprises at least an amorphous compound containing silicon and aluminum as a silica source and an alumina source, and at least one of sodium hydroxide and a halide as a sodium source.

9. A nitrogen oxide reduction catalyst comprising a CHA-type zeolite according to any one of claims 1 to 3.

10. A method for reducing nitrogen oxides using the nitrogen oxide reduction catalyst described in claim 9.

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