Zeolite and production method therefor

Abstract

The purpose of the present invention is to provide at least one of: a zeolite which has excellent hydrothermal durability and which, even after having undergone a hydrothermal durability treatment, exhibits excellent SCR catalytic activity; a method for producing the zeolite; and a selective reduction catalyst including the zeolite.　This zeolite has an intergrowth structure comprising a CHA structure and a GME structure, gives an X-ray powder diffraction pattern which at least has the peaks shown in the table, contains calcium and copper, and gives an XPS spectrum in which the proportion of the area for the spectral range of 930.0-933.0 eV to the area for the spectral range of 930.0-940.0 eV is less than 34%.　

Description

Zeolite and its manufacturing method

[0001] The present disclosure relates to calcium and copper containing zeolites.

[0002] Zeolites are used in a wide range of applications, such as catalysts, adsorbents, ion exchangers, etc. In particular, zeolites having pores formed by eight-membered oxygen rings and a framework structure of six-membered oxygen double rings have attracted attention as selective catalytic reduction catalysts (hereinafter also referred to as "SCR catalysts") for removing nitrogen oxides contained in automobile exhaust gases.

[0003] Patent Document 1 discloses a copper-containing GME / CHA intergrowth zeolite as a zeolite having pores formed from eight-membered oxygen rings and containing double six-membered rings in its framework structure.

[0004] Special table 2019-524606 publication

[0005] The copper-containing GME / CHA intergrowth zeolite disclosed in Patent Document 1 has a problem in that its activity for reducing nitrogen oxides (hereinafter also referred to as "SCR catalytic activity") decreases when it is exposed to a high-temperature, moist atmosphere due to its low hydrothermal durability. Hereinafter, the treatment of exposing the zeolite to a high-temperature, moist atmosphere is also referred to as hydrothermal durability treatment.

[0006] An object of the present disclosure is to provide at least one of a zeolite that has excellent hydrothermal durability and exhibits excellent SCR catalytic activity even after hydrothermal durability treatment, a method for producing the same, and a selective reduction catalyst containing the same.

[0007] The present inventors have investigated zeolites with nitrogen oxide reduction properties that are practical for use as SCR catalysts, and have found that when copper and calcium coexist in a specific state in a zeolite with a specific crystal structure (intergrowth structure), the zeolite exhibits excellent SCR catalytic activity even after hydrothermal durability treatment.

[0008] That is, the present invention is as defined in the claims, and the gist of the present disclosure is as follows: [1] A zeolite having an intergrowth structure including a CHA structure and a GME structure, having at least the peaks in the table below in a powder X-ray diffraction pattern, containing calcium and copper, and having an XPS spectrum in which the ratio of the spectral area in the range of 930.0 eV to 933.0 eV to the spectral area in the range of 930.0 eV to 940.0 eV is less than 34%. [2] The zeolite according to [1] above, wherein in a powder X-ray diffraction pattern, the ratio of the half-width of the peak at lattice spacing d = 4.29 ± 0.08 Å to the half-width of the peak at lattice spacing d = 4.97 ± 0.08 Å is 2.0 or more and 7.0 or less. [3] The zeolite according to [1] or [2] above, wherein the molar ratio of calcium to aluminum is 0.3 or less. [4] The zeolite according to any one of [1] to [3] above, wherein the molar ratio of calcium to aluminum is 0.01 or more and 0.3 or less. [5] The zeolite according to any one of [1] to [4] above, wherein the molar ratio of copper to aluminum is 0.05 or more and 0.4 or less. [6] The zeolite according to any one of [1] to [5] above, wherein the molar ratio of silica to alumina is 5.0 or more and 15 or less. [7] The zeolite according to any one of [1] to [6], wherein the ratio of the spectral area in the range of 930.0 eV to 933.0 eV in an XPS spectrum to the spectral area in the range of 930.0 eV to 940.0 eV is 10% or more and less than 34%. [8] A method for producing the zeolite according to any one of [1] to [7], comprising a copper-incorporating step of incorporating copper into a calcium-containing zeolite. [9] A method for producing the zeolite according to [8], further comprising a crystallization step of crystallizing a composition containing an alumina source, a silica source, an alkali source, a calcium source, and water in the presence of seed crystals to obtain the calcium-containing zeolite.

[10] A method for producing the zeolite according to [8], further comprising a crystallization step of crystallizing a composition containing an alumina source, a silica source, an alkali source, and water in the presence of seed crystals to obtain a raw zeolite, and a calcium-incorporating step of incorporating calcium into the raw zeolite to obtain the calcium-containing zeolite.

[11] A catalyst for selective reduction of nitrogen oxides, comprising the zeolite according to any one of [1] to [7].

[0009] According to the present invention, it is possible to provide at least one of a zeolite that is excellent in hydrothermal durability and exhibits excellent SCR catalytic activity even after hydrothermal durability treatment, a method for producing the same, and a selective reduction catalyst containing the same.

[0010] The zeolite of the present disclosure will be described below by showing an example of an embodiment. The terms used in this embodiment are as follows.

[0011] "Zeolite" is 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 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).

[0012] A "zeolite-like substance" is a compound having a regular structure in which T atoms are oxygen-mediated, and which contains at least an atom other than a metal or a metalloid atom (hereinafter also referred to as a "non-metal atom"). An example of a non-metal atom is phosphorus (P), and examples of zeolite-like substances containing phosphorus as a non-metal atom include complex phosphorus compounds such as aluminophosphate (AlPO) and silicoaluminophosphate (SAPO). For convenience, in this embodiment, "zeolite-like substances" are distinguished from "zeolites" in which the T atoms are composed of at least one of metal atoms and metalloid atoms.

[0013] 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 replaced with another metal atom. Among aluminosilicates, those having a crystalline XRD peak in their powder X-ray diffraction (hereinafter also referred to as "XRD") pattern are "crystalline aluminosilicates," and those not having a crystalline XRD peak are "amorphous aluminosilicates." Note that zeolites in which the T atoms are substantially composed of aluminum (Al) and silicon (Si) fall under the category of "crystalline aluminosilicates." Here, the expression "T atoms substantially consisting of aluminum (Al) and silicon (Si)" does not only mean that the T atoms consist only of aluminum (Al) and silicon (Si), but also means that the T atoms may contain T atoms other than aluminum (Al) and silicon (Si) as long as the effects of the present invention are achieved.

[0014] In this embodiment, the XRD pattern is measured using CuKα radiation as the radiation source, and the measurement conditions include the following: Acceleration current / voltage: 40 mA / 40 kV Radiation source: CuKα radiation (λ=1.5405 Å) Measurement mode: Continuous scan Scan condition: 40° / min Measurement range: 2θ=3° to 43° Divergence vertical limiting slit: 10 mm Divergence / entrance slit: 1° Receiving slit: open Receiving solar slit: 5° Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter

[0015] XRD patterns can be measured using a general powder X-ray diffractometer (e.g., Ultima IV, manufactured by Rigaku Corporation). Crystalline XRD peaks are peaks that are detected by identifying the 2θ of the peak top in an XRD pattern analysis using general analysis software (e.g., SmartLab Studio II, manufactured by Rigaku Corporation). The analysis conditions for the XRD pattern include the following: 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 conditions: second-order differential method, σ cut value = 3, χ threshold = 1.5

[0016] The "regular structure (hereinafter also referred to as "skeletal structure")" of zeolites and zeolite-like substances is a skeletal structure identified by the skeletal structure code (hereinafter also simply referred to as "skeletal code") established by the Structure Commission of the International Zeolite Association. For example, a "CHA structure" is a skeletal structure that corresponds to a CHA type in the skeletal code, and a "GME structure" is a skeletal structure that corresponds to a GME type in the skeletal code. The skeletal structure of zeolites and zeolite-like substances can also be expressed by dividing it into structural units (repeating units), and such structural units are generally called composite building units (CBUs). A composite building unit is a unit formed by connecting several (e.g., several to several tens) TOx units (e.g., TO4 units) consisting of a T atom and oxygen (O) bonded to it.

[0017] An "intergrowth structure including a CHA structure and a GME structure" is a skeletal structure that includes at least a composite building unit of a CHA structure (hereinafter also referred to as a "CHA unit") and a composite building unit of a GME structure (hereinafter also referred to as a "GME unit") as composite building units that constitute the skeletal structure of a zeolite (one zeolite), and is distinguished from a mixed zeolite obtained by mixing a zeolite of a CHA structure and a zeolite of a GME structure. In the "intergrowth structure including a CHA structure and a GME structure," the arrangement order of the CHA units and the GME units is not particularly limited, and they may be arranged regularly or irregularly. The "intergrowth structure including a CHA structure and a GME structure" may include, in addition to the CHA units and the GME units, units of other skeletal codes different from the CHA structure or the GME structure (hereinafter also referred to as "other units").

[0018] An "intergrowth structure including a CHA structure and a GME structure" exhibits a characteristic XRD pattern, and can therefore be identified from the XRD pattern. The XRD patterns of zeolites having an "intergrowth structure including a CHA structure and a GME structure" have similar characteristics, but exhibit different XRD patterns depending on the ratio of CHA units to GME units (hereinafter also referred to as "intergrowth ratio"). Some zeolites (with a predetermined intergrowth ratio) among those having an "intergrowth structure including a CHA structure and a GME structure" exhibit XRD patterns including at least each peak in Table 2 below. Therefore, zeolites showing XRD patterns including each peak in Table 2 below can be determined to have an "intergrowth structure including a CHA structure and a GME structure."

[0019] A zeolite having an "intergrowth structure containing a CHA structure and a GME structure" may contain, in addition to the peaks in Table 2 above, peaks attributable to an intergrowth structure containing a CHA structure and a GME structure (hereinafter also referred to as "other CHA / GME peaks") other than the peaks in Table 2 above. Examples of other CHA / GME peaks include peaks that appear in the DIFFaX pattern described below.

[0020] The "intergrowth structure containing a CHA structure and a GME structure" may be identified by obtaining powder X-ray diffraction patterns (hereinafter also referred to as "DIFFaX patterns") of a plurality of intergrowth structures having different ratios of CHA structure and GME structure from a simulation using DIFFaX (M.M.J. Treacy et al., Proceedings of the Royal Chemical Society, London, A (1991), Vol. 433, pp. 499-520), and comparing the obtained DIFFaX patterns with the XRD pattern of the zeolite.

[0021] Next, the zeolite of this embodiment will be described.

[0022] The zeolite of this embodiment has an intergrowth structure including a CHA structure and a GME structure, and has at least the peaks shown in Table 3 below in its XRD pattern. The zeolite of this embodiment also contains calcium and copper, and in its XPS spectrum, the spectral area ratio in the range of 930.0 eV to 933.0 eV to the spectral area in the range of 930.0 eV to 940.0 eV (hereinafter also referred to as "XPS area ratio") is less than 34%. Table 3 below is the same as Table 2 above.

[0023] The zeolite of this embodiment has an intergrowth structure including a CHA structure and a GME structure, and the skeletal structure (intergrowth structure) includes at least a CHA unit and a GME unit. The zeolite of this embodiment has an intergrowth structure including a CHA structure and a GME structure, which allows it to exhibit excellent SCR catalytic activity. The skeletal structure (intergrowth structure) of the zeolite of this embodiment may include other units in addition to the CHA unit and the GME unit, but from the viewpoint of further improving the SCR catalytic activity, it is preferably composed of two types of units, the CHA unit and the GME unit.

[0024] The zeolite of this embodiment has at least the peaks in Table 3 above in its XRD pattern. The zeolite of this embodiment can exhibit excellent SCR catalytic activity because it has the peaks in Table 3 above. In this embodiment, having a peak in the table means that the XRD pattern contains a peak that has a peak top within the range of the lattice spacing d (Å) shown in the table and whose maximum intensity is within the range of the relative intensity shown in the table.

[0025] The zeolite of this embodiment may have an XRD pattern that includes at least the peaks in Table 3 above. However, from the viewpoint of further improving the SCR catalytic activity, the ratio of the half-width of the peak at lattice spacing d = 4.29 ± 0.08 Å to the half-width of the peak at lattice spacing d = 4.97 ± 0.08 Å in Table 3 is preferably 2.0 or more and 7.0 or less, and more preferably 3.0 or more and 5.0 or less. The half-width of each peak can be determined by analyzing the XRD pattern using general analysis software (e.g., SmartLab Studio II, manufactured by Rigaku Corporation). Note that the half-width in this specification means the full width at half maximum.

[0026] Furthermore, the zeolite of the present embodiment may have an XRD pattern that includes at least the peaks in Table 3 above. However, from the viewpoint of further improving the SCR catalytic activity, it is preferable that each peak in Table 3 above be within the range of the half-width shown in Table 4 below.

[0027] The zeolite of this embodiment contains calcium. By containing calcium, the zeolite of this embodiment can exhibit excellent hydrothermal durability. In the zeolite of this embodiment, the molar ratio of calcium to aluminum (hereinafter also referred to as the "Ca / Al ratio") is not particularly limited, but from the viewpoint of further improving hydrothermal durability, it is preferably 0.01 or more, more preferably 0.015 or more, and even more preferably 0.02 or more. Furthermore, from the viewpoint of further improving hydrothermal durability, the Ca / Al ratio in the zeolite of this embodiment is preferably 0.3 or less, more preferably 0.25 or less, and even more preferably 0.15 or less. The upper and lower limits of the Ca / Al ratio may be any combination of the above-mentioned upper and lower limits, but are preferably 0.01 or more and 0.3 or less, more preferably 0.015 or more and 0.25 or less, and even more preferably 0.02 or more and 0.15 or less.

[0028] The zeolite of this embodiment contains copper. In the zeolite of this embodiment, the molar ratio of copper to aluminum (hereinafter also referred to as the "Cu / Al ratio") is not particularly limited, but from the viewpoint of further improving hydrothermal durability, it is preferably 0.05 or more, more preferably 0.10 or more, and even more preferably 0.12 or more. In addition, from the viewpoint of further improving hydrothermal durability, the Cu / Al ratio in the zeolite of this embodiment is preferably 0.4 or less, more preferably 0.35 or less, and even more preferably 0.30 or less. The upper and lower limits of the Cu / Al ratio may be any combination of the above-mentioned upper and lower limits, but from the viewpoint of further improving hydrothermal durability, it is preferably 0.05 or more and 0.4 or less, more preferably 0.10 or more and 0.35 or less, even more preferably 0.10 or more and 0.30 or less, and particularly preferably 0.12 or more and 0.30 or less.

[0029] The zeolite of this embodiment may contain calcium and copper, and the form in which they are contained is not particularly limited. However, from the viewpoint of further improving hydrothermal durability, it is preferable that at least one of calcium and copper is supported on the zeolite. In this embodiment, "containing a specific element" means that the specific element is contained in the zeolite, and the specific element may be contained in any state and at any site. On the other hand, "supporting a specific element" means that the specific element is contained as a component other than the T atom of the zeolite. Examples of the form in which the specific element is supported include a form in which the specific element is supported on at least one of the outer surface of the zeolite (the surface of the zeolite excluding the inner surfaces of the pores) and the inner surfaces of the pores.

[0030] The state of calcium and copper contained in the zeolite of this embodiment is not particularly limited as long as the XPS area ratio described below is less than 34%, and examples thereof include a compound (e.g., oxide), a metal, an ion, an alloy, or two or more of these. Note that the states of calcium and copper may be the same or different.

[0031] The zeolite of this embodiment may contain, in addition to calcium and copper, other substances such as alkali metals, alkaline earth metals, and transition metals.

[0032] In the XPS spectrum of the zeolite of this embodiment, the ratio of the spectral area in the range of 930.0 eV to 933.0 eV to the spectral area in the range of 930.0 eV to 940.0 eV (XPS area ratio) is less than 34%. From the viewpoint of further improving hydrothermal durability, the XPS area ratio of the zeolite of this embodiment is preferably 10% to less than 34%, more preferably 15% to 33%, and even more preferably 25% to 33%. The XPS area ratio is a value obtained by dividing the spectral area in the range of 930.0 eV to 933.0 eV by the spectral area in the range of 930.0 eV to 940.0 eV, expressed as a percentage.

[0033] X-ray photoelectron spectroscopy (XPS) is a method for analyzing the chemical state of metals contained in a sample. In an XPS spectrum obtained by analyzing a zeolite containing calcium and copper using XPS, peaks representing zero-valent, monovalent, and divalent copper appear at 930.0 eV to 940.0 eV, and a peak representing zero-valent copper appears at 930.0 eV to 933.0 eV. Therefore, the above-mentioned XPS area ratio functions as an index representing the ratio of zero-valent copper to total copper (zero-valent, monovalent, and divalent copper) in the zeolite containing calcium and copper.

[0034] In this embodiment, the XPS spectrum can be measured using a general X-ray photoelectron spectrometer (for example, PHI5000VersaProbeII, manufactured by ULVAC-PHI), and the measurement conditions can be exemplified as follows: X-ray source: Monochrome Al-Kα ray X-ray beam diameter: 100 μmφ Energy resolution: Wide scan spectrum 117.40 eV High resolution spectrum 46.95 eV (Cu2p ３／２ ) Charge correction: Al2p main peak (74.4 eV) No sputtering treatment

[0035] The peak area of ​​an XPS spectrum can be calculated from the sum of the areas of trapezoids between data points. More specifically, the measured XPS spectrum is divided by multiple virtual lines spaced at intervals of 0.10 eV, and the area of ​​each of the divided XPS spectra is calculated assuming that it is a trapezoid (a right-angled trapezoid enclosed by two adjacent virtual lines, a line connecting the intersection of the two virtual lines with the XPS spectrum curve, and the horizontal axis). The areas of the individual trapezoids are then added together to calculate the peak area of ​​the XPS spectrum.

[0036] In the zeolite of this embodiment, the molar ratio of silica to alumina (hereinafter referred to as "SiO ２ / Al ２ O ３The SiO ratio is not particularly limited, but is preferably 5.0 or more, more preferably 5.5 or more, and even more preferably 6.0 or more, from the viewpoint of further improving the SCR catalytic activity over a range from a low temperature (for example, 150°C) to a high temperature (for example, 600°C). ２ / Al ２ O ３ From the viewpoint of further improving the SCR catalytic activity over a range from a low temperature (e.g., 150°C) to a high temperature (e.g., 600°C), the ratio is preferably 15 or less, more preferably 10 or less, and even more preferably 9.5 or less. ２ / Al ２ O ３ The upper and lower limit values ​​of the ratio may be any combination of the above-mentioned upper and lower limit values, but from the viewpoint of further improving the SCR catalytic activity over a range from a low temperature (e.g., 150°C) to a high temperature (e.g., 600°C), the ratio is preferably 5.0 or more and 15 or less, more preferably 5.5 or more and 10 or less, and even more preferably 6.0 or more and 9.5 or less.

[0037] In the zeolite of this embodiment, the T atoms constituting the framework structure are not particularly limited as long as they are composed of at least one of metal atoms and metalloid atoms, but from the viewpoint of further improving hydrothermal durability, they are preferably composed of aluminum (Al) and silicon (Si). In other words, the zeolite of this embodiment is preferably a crystalline aluminosilicate having an intergrowth structure including a CHA structure and a GME structure.

[0038] The zeolite of the present embodiment described above can be used as a selective catalytic reduction catalyst (SCR catalyst) for reducing and removing nitrogen oxides. The method for removing nitrogen oxides using the zeolite of the present embodiment includes a contacting step (hereinafter simply referred to as the "contacting step") of bringing a fluid containing nitrogen oxides and a reducing agent (hereinafter also referred to as a "nitrogen oxide-containing fluid") into contact with the zeolite of the present embodiment. In the contacting step, the nitrogen oxide-containing fluid comes into contact with the zeolite of the present embodiment, whereby the nitrogen oxides are reduced and removed.

[0039] Examples of nitrogen oxides contained in the nitrogen oxide-containing fluid include nitric oxide, nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide, and dinitrogen monoxide, and two or more of these may be used.

[0040] The reducing agent contained in the nitrogen oxide-containing fluid may include ammonia, urea, alcohol, ketone, carbon monoxide, and hydrogen, and two or more of these may be used.

[0041] The nitrogen oxide-containing fluid may be composed only of nitrogen oxide and a reducing agent, but may also contain, in addition to these components, one or more other components such as carbon dioxide, nitrogen, oxygen, sulfur oxide, water, etc. Specific examples of fluids that can be used as the nitrogen oxide-containing fluid include exhaust gases from diesel automobiles, gasoline automobiles, boilers, gas turbines, etc.

[0042] The nitrogen oxide-containing fluid may be one or more selected from the group consisting of a liquid, a gas, and a mixed fluid of a liquid and a gas. From the viewpoint of further improving the reduction rate of nitrogen oxides, however, a gas is preferred.

[0043] The zeolite of this embodiment, which is to be brought into contact with the nitrogen oxide-containing fluid, may be molded into a predetermined shape. Examples of methods for molding the zeolite of this embodiment include rolling granulation molding, press molding, extrusion molding, injection molding, slip casting, and sheet molding. Examples of the shape of the molded zeolite include spherical, approximately spherical, ellipsoidal, disk-like, cylindrical, polyhedral, irregular, and petal-like. The zeolite of this embodiment may be molded together with a binder to form a molded body containing the binder and the zeolite. Examples of the binder include one or more selected from the group consisting of silica, alumina other than γ-alumina, kaolin, attapulgite, montmorillonite, bentonite, and sepiolite.

[0044] The reduction reaction of nitrogen oxides in the contact step proceeds by contacting the nitrogen oxide-containing fluid with the zeolite of the present embodiment, and therefore the contact conditions for contacting the nitrogen oxide-containing fluid with the zeolite of the present embodiment are not particularly limited. Preferred contact conditions include the following:

[0045] In order to further improve the reduction rate of nitrogen oxides, the contact temperature between the zeolite of this embodiment and the nitrogen oxide-containing fluid is preferably 100°C or higher and 700°C or lower, and more preferably 150°C or higher and 600°C or lower.

[0046] The space velocity (SV) of the nitrogen oxide-containing fluid brought into contact with the zeolite of this embodiment is set to 500 hr from the viewpoint of further improving the reduction rate of nitrogen oxides. －１ More than 500,000 hours －１ It is preferable that the time is 2000 hours or less. －１ More than 300,000 hours －１ The SV of the nitrogen oxide-containing fluid is a parameter that represents the amount of nitrogen oxide-containing fluid supplied per unit volume of zeolite per hour ([L (zeolite)] / [L (nitrogen oxide-containing fluid) / h] (=[hr －１ ])).

[0047] The nitrogen oxide concentration in the nitrogen oxide-containing fluid to be brought into contact with the zeolite of this embodiment is preferably 3 ppm or more and 600 ppm or less, and more preferably 100 ppm or more and 550 ppm or less, taking into consideration the concentration of nitrogen oxides contained in exhaust gases from automobiles, etc. In this specification, ppm means ppm by volume.

[0048] From the viewpoint of further improving the reduction rate of nitrogen oxides, the volume of the reducing agent in the nitrogen oxide-containing fluid to be brought into contact with the zeolite of this embodiment is preferably 100 parts by volume or more and 200 parts by volume or less, and more preferably 100 parts by volume or more and 150 parts by volume or less, per 100 parts by volume of nitrogen oxides in the nitrogen oxide-containing fluid.

[0049] The contact time between the zeolite of this embodiment and the nitrogen oxide-containing fluid can be appropriately set depending on the amount of nitrogen oxides to be reduced. The zeolite of this embodiment has excellent hydrothermal durability, so it can maintain its SCR catalytic activity even when exposed to a high-temperature nitrogen oxide-containing fluid containing water for a long period of time.

[0050] Next, a method for producing the zeolite of this embodiment will be described.

[0051] The method for producing a zeolite according to the present embodiment includes a copper-containing step of adding copper to a zeolite containing calcium (hereinafter referred to as a "calcium-containing zeolite"). As will be shown in a comparative example described later, if calcium is added to a zeolite containing copper (hereinafter also referred to as a "copper-containing zeolite"), the XPS area ratio of the resulting zeolite is likely to be 34% or more, making it difficult to produce the zeolite according to the present embodiment.

[0052] In the copper-incorporating step, the method for incorporating copper into the calcium-containing zeolite is not particularly limited, and for example, a treatment of bringing a copper source into contact with the calcium-containing zeolite (hereinafter simply referred to as "copper contact treatment") can be used. Note that, examples of the method for incorporating copper by copper contact treatment include an ion exchange method, an impregnation method, an evaporation-to-dryness method, a precipitation method, and a physical mixing method, and it is preferable to use the ion exchange method or the impregnation method.

[0053] The copper source to be brought into contact with the calcium-containing zeolite is a substance containing copper, and examples thereof include copper nitrate, copper sulfate, copper acetate, copper chloride, copper complex salts, copper oxide, copper-containing composite oxides, or two or more of these. Since this makes it easier for copper to be contained in the calcium-containing zeolite, the copper source to be brought into contact with the calcium-containing zeolite is preferably one or more selected from the group consisting of copper nitrate, copper sulfate, and copper oxide.

[0054] The contact between the copper source and the calcium-containing zeolite is preferably carried out by contacting the calcium-containing zeolite with a solution containing the copper source (hereinafter also referred to as a "copper solution"), since this makes it easier for copper to be contained in the calcium-containing zeolite. Examples of the solvent contained in the copper solution include at least one of water and an alcohol, and water is preferred.

[0055] The copper concentration in the copper solution is not particularly limited and may be appropriately adjusted in consideration of the Cu / Al ratio, etc., so that the zeolite of the present embodiment can be produced. From the viewpoint of making it easier to produce the zeolite of the present embodiment, the copper concentration in the copper solution is preferably a concentration such that the Cu / Al ratio of the calcium-containing zeolite (the zeolite of the present embodiment) that has been subjected to the copper contact treatment is 0.10 or more and 0.30 or less.

[0056] The contact conditions between the copper source and the calcium-containing zeolite are not particularly limited, and may be appropriately adjusted taking into consideration the Cu / Al ratio and the like so that the zeolite of this embodiment can be produced. From the viewpoint of facilitating the production of the zeolite of this embodiment, the contact conditions between the copper source and the calcium-containing zeolite are preferably such that the Cu / Al ratio of the calcium-containing zeolite (the zeolite of this embodiment) that has been subjected to the copper contact treatment is 0.10 or more and 0.30 or less. For example, the contact time between the calcium-containing zeolite and the copper source may be 10 minutes or more and 24 hours or less. For example, the contact temperature between the calcium-containing zeolite and the copper source may be 20° C. or more and 110° C. or less. For example, the contact pressure between the calcium-containing zeolite and the copper source may be 0.0 MPa or more and 1.0 MPa or less (gauge pressure).

[0057] The calcium-containing zeolite is brought into contact with a copper source through the copper contact treatment, thereby incorporating copper into the calcium-containing zeolite. The calcium-containing zeolite containing copper may be used as the zeolite of the present embodiment as is, or may be used as the zeolite of the present embodiment after being subjected to one or more treatments selected from the group consisting of a washing treatment, a drying treatment, a calcination treatment, and an ion exchange treatment. The order of these treatments can be set as appropriate.

[0058] The washing treatment is a treatment for washing the zeolite, and the washing treatment may be carried out by washing the zeolite with pure water, for example.

[0059] The drying treatment is a treatment for removing moisture adsorbed to the zeolite. The drying conditions are arbitrary as long as they can remove moisture from the zeolite. An example of the drying conditions is drying the zeolite in the atmosphere at a temperature of 50°C or higher and 150°C or lower for 2 hours or longer and 12 hours or shorter. The drying treatment may be carried out in a stationary state or in a stirred state. The drying treatment may also be carried out using, for example, a spray dryer.

[0060] The calcination treatment is a treatment in which the zeolite is calcined to fix the metal element (copper or calcium) to the zeolite. The calcination conditions are arbitrary as long as the metal element (copper or calcium) can be fixed to the zeolite. One example of the calcination conditions is to calcinate the zeolite in the atmosphere at a temperature of 400°C or higher and 800°C or lower for 1 hour to 5 hours. The calcination treatment may be performed with the zeolite left to stand, or may be performed with the zeolite stirred using a kiln or the like.

[0061] The ion exchange treatment is a treatment for changing the cation type of zeolite to an arbitrary cation type. For the ion exchange treatment, a conventionally known method can be used. For example, the cation type of zeolite can be changed to ammonium (NH ４ ＋ When the cation type of zeolite is converted to the proton type (H ＋When forming a ammonium (NH ４ ＋ The zeolite of the hydroxyl group-containing zeolite type may be calcined at a temperature of 400° C. to 700° C. for 1 hour to 5 hours.

[0062] The calcium-containing zeolite (calcium-containing zeolite containing copper) used in the copper-containing step (copper contact treatment) is not particularly limited as long as it can contain copper to obtain the zeolite of this embodiment, but is preferably a calcium-containing zeolite produced by at least one of the first production method (hereinafter also referred to as "production method (1)") and the second production method (hereinafter also referred to as "production method (2)") described below. Note that the calcium-containing zeolite used in the copper-containing step (copper contact treatment) may be a mixture of the calcium-containing zeolite produced by the production method (1) and the calcium-containing zeolite produced by the production method (2).

[0063] First, the production method (1) for producing calcium-containing zeolite will be described. The production method (1) is a method in which a zeolite is synthesized from a raw material composition, and then calcium is incorporated into the zeolite.

[0064] The production method (1) includes a crystallization step (hereinafter also referred to as "crystallization step (1)") in which a raw material composition containing at least an alumina source, a silica source, an alkali source, and water is crystallized in the presence of seed crystals, and a calcium-incorporating step (hereinafter also referred to as "calcium-incorporating step (1)") in which calcium is incorporated into the raw material zeolite obtained in the crystallization step (1). A calcium-containing zeolite can be obtained by the production method (1) including these steps.

[0065] In the crystallization step (1), the alumina source contained in the raw material composition is alumina (Al ２ O ３) and at least one of its precursors, for example, at least one 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, and is preferably an amorphous aluminum compound, more preferably at least one of aluminum hydroxide and amorphous aluminosilicate, and even more preferably amorphous aluminosilicate. Note that substances containing aluminum (Al) and silicon (Si), such as amorphous aluminosilicate, can be used not only as an alumina source but also as a silica source, which will be described later.

[0066] In the crystallization step (1), the silica source contained in the raw material composition is silica (SiO ２ ) or 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. An amorphous silicon compound is preferred, and an amorphous aluminosilicate is more preferred.

[0067] When the alumina source and silica source contained in the raw material composition do not contain crystalline aluminosilicate, the production cost tends to be lower, which is industrially advantageous.

[0068] In the crystallization step (1), the alkali source contained in the raw material composition is an alkali metal or a compound containing an alkali metal element, and examples thereof include one or more selected from the group consisting of alkali metal hydroxides, carbonates, sulfates, chlorides, bromides, and iodides. One or more selected from the group consisting of alkali metal hydroxides, chlorides, bromides, and iodides are preferred, and alkali metal hydroxides are more preferred. The alkali metal (alkali metal element) contained in the alkali source includes one or more selected from the group consisting of sodium, potassium, rubidium, and cesium, and at least one of sodium and potassium is more preferred. A particularly preferred alkali source is at least one of sodium hydroxide and potassium hydroxide.

[0069] In the crystallization step (1), the water contained in the raw material composition may be deionized water or pure water. When the raw material other than water contained in the raw material composition contains water such as hydrate, structural water, or solvent, these waters are treated as the water (H ２ O).

[0070] In the crystallization step (1), the raw material composition does not contain calcium. A production method in which calcium is contained in the raw material composition corresponds to production method (2) described below. In addition, in the crystallization step (1), the raw material composition preferably does not contain an organic structure-directing agent, because the raw material zeolite obtained by crystallization is likely to have an intergrowth structure containing a CHA structure and a GME structure. In addition, in the crystallization step (1), the raw material composition preferably does not contain fluorine (F) or phosphorus (P), because this makes it easier to apply production equipment made of general-purpose materials.

[0071] In this specification, "not containing a specified substance" means that the content determined by general composition analysis such as ICP measurement is 100 ppm by mass or less, preferably 10 ppm by mass or less, and more preferably below the measurement limit.

[0072] In the crystallization step (1), SiO ２ / Al ２ O ３The ratio is preferably 24 or less, more preferably 22 or less, and even more preferably 20 or less. ２ / Al ２ O ３ The ratio is preferably 8 or more, more preferably 10 or more, and even more preferably 13 or more. ２ / Al ２ O ３ The upper and lower limit values ​​of the ratio may be any combination of the above upper and lower limit values, but are preferably 8 or more and 24 or less, more preferably 10 or more and 22 or less, and even more preferably 13 or more and 20 or less. ２ / Al ２ O ３ The ratio is the SiO ２ / Al ２ O ３ The ratio tends to be lower than the SiO ratio of the raw material composition. ２ / Al ２ O ３ By setting the ratio to 24 or less, the SiO ２ / Al ２ O ３ This makes it easier to obtain a calcium-containing zeolite having a ratio of 0.1 to 0.2, and makes it easier to obtain a zeolite having better SCR catalytic activity over a range from a low temperature (for example, 150°C) to a high temperature (for example, 600°C).

[0073] In the crystallization step (1), the molar ratio of alkali metal to silica in the raw material composition (hereinafter referred to as "M / SiO ２ In the crystallization step (1), the M / SiO ratio of the raw material composition is preferably 0.30 or more, more preferably 0.35 or more, and even more preferably 0.40 or more. ２ The ratio is preferably 0.70 or less, more preferably 0.65 or less, and even more preferably 0.60 or less. ２The upper and lower limit values ​​of the ratio may be any combination of the above upper and lower limit values, but are preferably 0.30 or more and 0.70 or less, more preferably 0.35 or more and 0.65 or less, and even more preferably 0.40 or more and 0.60 or less. ２ When the ratio is within the above-mentioned range, the peaks in Table 3 are more likely to be included in the XRD pattern of the raw material zeolite obtained by crystallization, making it easier to produce the zeolite of this embodiment.

[0074] In the crystallization step (1), the molar ratio of water to silica in the raw material composition (hereinafter referred to as "H ２ O / SiO ２ The ratio (also referred to as "ratio") is preferably 3 or more, more preferably 5 or more, and even more preferably 8 or more. ２ O / SiO ２ The ratio is preferably 50 or less, more preferably 30 or less, and even more preferably 25 or less. ２ O / SiO ２ The upper and lower limit values ​​of the ratio may be any combination of the above upper and lower limit values, but are preferably 3 or more and 50 or less, more preferably 5 or more and 30 or less, and even more preferably 8 or more and 25 or less. ２ O / SiO ２ When the ratio is within the above-mentioned range, the peaks in Table 3 are more likely to be included in the XRD pattern of the raw material zeolite obtained by crystallization, making it easier to produce the zeolite of this embodiment.

[0075] In the crystallization step (1), the molar ratio of hydroxide ions to silica in the raw material composition (hereinafter referred to as "OH / SiO ２ In the crystallization step (1), the OH / SiO ratio of the raw material composition is preferably 0.30 or more, more preferably 0.35 or more, and even more preferably 0.40 or more. ２The OH / SiO ratio of the raw material composition is preferably 0.70 or less, more preferably 0.65 or less, and even more preferably 0.60 or less. ２ The upper and lower limit values ​​of the ratio may be any combination of the above upper and lower limit values, but are preferably 0.30 or more and 0.70 or less, more preferably 0.35 or more and 0.65 or less, and even more preferably 0.40 or more and 0.60 or less. ２ When the ratio is within the above-mentioned range, the peaks in Table 3 are more likely to be included in the XRD pattern of the raw material zeolite obtained by crystallization, making it easier to produce the zeolite of this embodiment.

[0076] The raw material composition in the crystallization step (1) preferably has any combination of the following molar compositions. In the following molar compositions, M is the molar amount of alkali metals. When the raw material composition contains only one alkali metal, it indicates the molar amount of that alkali metal. When the raw material composition contains two or more alkali metals, it indicates the total molar amount of the two or more alkali metals. For example, when the raw material composition contains sodium and potassium as alkali metals, M / SiO ２ The ratio is (Na+K) / SiO ２ The ratio is SiO ２ / Al ２ O ３ Ratio M / SiO = 8 or more, 10 or more, or 13 or more, and 24 or less, 22 or less, or 20 or less ２ Ratio = 0.30 or more, or 0.35 or more, 0.40 or more and 0.70 or less, 0.65 or less, or 0.60 or less H ２ O / SiO ２ OH / SiO ratio = 3 or more, 5 or more, or 8 or more and 50 or less, 30 or less, or 25 or less ２ Ratio = 0.30 or more, 0.35 or more, or 0.40 or more, and 0.70 or less, 0.65 or less, or 0.60 or less

[0077] In the crystallization step (1), the raw material composition is crystallized in the presence of seed crystals. Examples of the method for crystallizing the raw material composition in the presence of seed crystals include a method of adding seed crystals to the raw material composition and crystallizing the raw material composition to which the seed crystals have been added.

[0078] The seed crystal is preferably one or more selected from the group consisting of CHA zeolite, AFX zeolite, GME zeolite, LEV zeolite, and OFF zeolite, and more preferably CHA zeolite, because the peaks in Table 3 are more likely to be included in the XRD pattern of the raw material zeolite obtained by crystallization.

[0079] The silicon (Si) and aluminum (Al) in the raw material composition (not including the seed crystals) were converted to SiO ２ and Al ２ O ３ The silicon (Si) and aluminum (Al) of the seed crystals are converted into SiO ２ and Al ２ O ３ The proportion of the total mass converted into kJ / kcal (hereinafter also referred to as "seed crystal content") is preferably more than 0 mass%, more preferably 0.5 mass% or more, and even more preferably 1 mass% or more. The seed crystal content is preferably 10 mass% or less, more preferably 5 mass% or less, and even more preferably 3 mass% or less. The upper and lower limit values ​​of the seed crystal content may be any combination of the above-mentioned upper and lower limit values, but is preferably more than 0 mass% and 10 mass% or less, more preferably 0.5 mass% or more and 5 mass% or less, and even more preferably 1 mass% or more and 3 mass% or less. When the seed crystal content is within the above-mentioned range, the peaks shown in Table 3 are more likely to be included in the XRD pattern of the raw material zeolite obtained by crystallization, making it easier to produce the zeolite of this embodiment.

[0080] The crystallization method of the raw material composition may be any method that crystallizes the raw material composition, and for example, a hydrothermal synthesis method in which the raw material composition is hydrothermally treated can be used. Examples of conditions for the hydrothermal treatment include the following: Crystallization temperature: 120°C or higher, 130°C or higher, or 135°C or higher, and 200°C or lower, 180°C or lower, or 160°C or lower Crystallization time: 1 hour or higher, 5 hours or higher, or 10 hours or higher, and 7 days or lower, 5 days or lower, 3 days or lower, or 2 days or lower Crystallization state: at least one of a stirring state and a static state, or a stirring state Crystallization pressure: autogenous pressure

[0081] The raw zeolite obtained in the crystallization step (1) described above is used in the calcium-containing step described below. The raw zeolite obtained in the crystallization step (1) may be used in the calcium-containing step (1) as is, or may be further subjected to one or more treatments selected from the group consisting of a washing treatment, a drying treatment, and an ion exchange treatment before being used in the calcium-containing step (1). When the raw zeolite obtained in the crystallization step (1) is subjected to an ion exchange treatment, the ion exchange treatment is carried out to change the cation type of the raw zeolite to a proton (H ＋ ) type or ammonium (NH ４ ＋ It is preferable that the cation type of the raw material zeolite is a proton (H ＋ ) type or ammonium (NH ４ ＋ ) type, calcium is more easily incorporated in the calcium-incorporating step described below compared to other cation types.

[0082] The cleaning treatment, drying treatment, and ion exchange treatment have been described above (because they are the same as the cleaning treatment, drying treatment, and ion exchange treatment that can be performed on calcium-containing zeolite containing copper), and therefore detailed explanations thereof will be omitted.

[0083] In the calcium-incorporating step (1), calcium is incorporated into the raw zeolite obtained in the crystallization step (1). In the calcium-incorporating step (1), the method for incorporating calcium into the raw zeolite obtained in the crystallization step (1) is not particularly limited, and for example, a treatment in which a calcium source is brought into contact with the raw zeolite (hereinafter simply referred to as a "calcium contact treatment") can be used. Examples of methods for incorporating calcium through calcium contact treatment include ion exchange, impregnation, evaporation to dryness, precipitation, and physical mixing. However, the ion exchange or impregnation method is preferably used.

[0084] The calcium source to be brought into contact with the raw zeolite is a substance containing calcium, and examples thereof include salts and compounds containing calcium. In order to make it easier for calcium to be contained in the raw zeolite, the calcium source to be brought into contact with the raw zeolite is preferably one or more selected from the group consisting of calcium chloride, calcium iodide, calcium bromide, calcium hydroxide, calcium oxide, and calcium nitrate, more preferably one or more selected from the group consisting of calcium chloride, calcium bromide, and calcium nitrate, and even more preferably calcium nitrate.

[0085] The contact between the calcium source and the raw zeolite is preferably carried out by contacting the raw zeolite with a solution containing the calcium source (hereinafter also referred to as a "calcium solution"), since this allows calcium to be more easily incorporated into the raw zeolite. Examples of the solvent contained in the calcium solution include at least one of water and an alcohol, and water is preferred.

[0086] The calcium concentration in the calcium solution is not particularly limited and may be appropriately adjusted in consideration of the Ca / Al ratio so that the zeolite of the present embodiment can be produced. From the viewpoint of facilitating the production of the zeolite of the present embodiment, the calcium concentration in the calcium solution is preferably such that the Ca / Al ratio of the calcium-containing zeolite obtained by the calcium contact treatment is 0.01 or more and 0.3 or less.

[0087] The contact conditions between the calcium source and the raw zeolite are not particularly limited, and may be appropriately adjusted taking into account the Ca / Al ratio and the like so that the zeolite of this embodiment can be produced. From the viewpoint of facilitating the production of the zeolite of this embodiment, the contact conditions between the calcium source and the raw zeolite are preferably such that the Ca / Al ratio of the calcium-containing zeolite obtained by the calcium contact treatment is 0.01 or more and 0.3 or less. For example, the contact time between the raw zeolite and the calcium source may be 10 minutes or more and 24 hours or less. Furthermore, for example, the contact temperature between the raw zeolite and the calcium source may be 20°C or more and 110°C or less. Furthermore, for example, the contact pressure between the raw zeolite and the calcium source may be 0.0 MPa or more and 1.0 MPa or less (gauge pressure).

[0088] In the calcium-containing step (1), calcium is contained in the raw material zeolite, whereby a calcium-containing zeolite (calcium-containing zeolite obtained by the production method (1)) can be produced. The calcium-containing zeolite obtained by the production method (1) may be used in the copper-containing step as is, or may be used in the copper-containing step after being subjected to one or more treatments selected from the group consisting of a washing treatment, a drying treatment, a calcination treatment, and an ion exchange treatment. When the calcium-containing zeolite obtained by the production method (1) is subjected to an ion exchange treatment, the ion exchange treatment is carried out to change the cation type of the calcium-containing zeolite to a proton (H ＋ ) type or ammonium (NH ４ ＋ It is preferable that the cation type of the calcium-containing zeolite is a proton (H ＋ ) type or ammonium (NH ４ ＋ ) type, copper is more likely to be contained in the copper-containing step compared to other cation types.

[0089] The cleaning treatment, drying treatment, calcination treatment, and ion exchange treatment have been described above (because they are the same as the cleaning treatment, drying treatment, calcination treatment, and ion exchange treatment that can be performed on calcium-containing zeolite containing copper), and therefore detailed explanations thereof will be omitted.

[0090] Next, a description will be given of Production Method (2) for producing calcium-containing zeolite. Production Method (2) is a method for synthesizing calcium-containing zeolite from a raw material composition. Compared to Production Method (1), Production Method (2) can suppress the generation of by-products and can produce calcium-containing zeolite in a higher yield.

[0091] The production method (2) includes a crystallization step (hereinafter also referred to as "crystallization step (2)") in which a raw material composition containing at least an alumina source, a silica source, an alkali source, a calcium source, and water is crystallized in the presence of seed crystals. The crystallization step (2) is the same as the crystallization step (1) except for the raw material composition to be crystallized, and therefore a detailed description thereof will be omitted, excluding the raw material composition to be crystallized.

[0092] In the crystallization step (2), the alumina source, silica source, alkali source, and water contained in the raw material composition can be the same as the alumina source, silica source, alkali source, and water contained in the raw material composition of the crystallization step (1), respectively.

[0093] In the crystallization step (2), the calcium source contained in the raw material composition can be the calcium source used in the calcium-containing step (1) (calcium contact treatment).

[0094] In the crystallization step (2), the raw material composition preferably does not contain an organic structure-directing agent, because the calcium-containing zeolite obtained by crystallization is likely to have an intergrowth structure containing a CHA structure and a GME structure. Furthermore, in the crystallization step (2), the raw material composition preferably does not contain fluorine (F) or phosphorus (P), because this makes it easier to apply production equipment made of general-purpose materials.

[0095] In the crystallization step (2), SiO ２ / Al ２ O ３The ratio is preferably 24 or less, more preferably 22 or less, and even more preferably 20 or less. ２ / Al ２ O ３ The ratio is preferably 8 or more, more preferably 10 or more, and even more preferably 13 or more. ２ / Al ２ O ３ The upper and lower limit values ​​of the ratio may be any combination of the above upper and lower limit values, but are preferably 8 or more and 24 or less, more preferably 10 or more and 22 or less, and even more preferably 13 or more and 20 or less. ２ / Al ２ O ３ The ratio is the SiO ２ / Al ２ O ３ The ratio tends to be lower than the SiO ratio of the raw material composition. ２ / Al ２ O ３ By setting the ratio to 24 or less, the SiO ２ / Al ２ O ３ This makes it easier to obtain a calcium-containing zeolite having a ratio of 0.1 to 0.2, and makes it easier to obtain a zeolite having better SCR catalytic activity over a range from a low temperature (for example, 150°C) to a high temperature (for example, 600°C).

[0096] In the crystallization step (2), M / SiO ２ The ratio is preferably 0.30 or more, more preferably 0.35 or more, and even more preferably 0.40 or more. ２ The ratio is preferably 0.70 or less, more preferably 0.65 or less, and even more preferably 0.60 or less. ２The upper and lower limit values ​​of the ratio may be any combination of the above upper and lower limit values, but are preferably 0.30 or more and 0.70 or less, more preferably 0.35 or more and 0.65 or less, and even more preferably 0.40 or more and 0.60 or less. ２ When the ratio is within the above-mentioned range, the peaks in Table 3 are more likely to be included in the XRD pattern of the calcium-containing zeolite obtained by crystallization, making it easier to produce the zeolite of this embodiment.

[0097] In the crystallization step (2), H of the raw material composition ２ O / SiO ２ The ratio is preferably 3 or more, more preferably 5 or more, and even more preferably 8 or more. ２ O / SiO ２ The ratio is preferably 50 or less, more preferably 30 or less, and even more preferably 25 or less. ２ O / SiO ２ The upper and lower limit values ​​of the ratio may be any combination of the above upper and lower limit values, but are preferably 3 or more and 50 or less, more preferably 5 or more and 30 or less, and even more preferably 8 or more and 25 or less. ２ O / SiO ２ When the ratio is within the above-mentioned range, the peaks in Table 3 are more likely to be included in the XRD pattern of the calcium-containing zeolite obtained by crystallization, making it easier to produce the zeolite of this embodiment.

[0098] In the crystallization step (2), the molar ratio of calcium to silica in the raw material composition (hereinafter referred to as "Ca / SiO ２ In the crystallization step (2), the Ca / SiO ratio of the raw material composition is preferably 0.001 or more, and more preferably 0.003 or more. ２ The ratio is preferably 0.030 or less, and more preferably 0.020 or less. ２The upper and lower limit values ​​of the ratio may be any combination of the above upper and lower limit values, but are preferably 0.001 or more and 0.030 or less, more preferably 0.001 or more and 0.020 or less, and even more preferably 0.003 or more and 0.020 or less. ２ When the ratio is within the above-mentioned range, the peaks in Table 3 are more likely to be included in the XRD pattern of the calcium-containing zeolite obtained by crystallization, making it easier to produce the zeolite of this embodiment.

[0099] In the crystallization step (2), the OH / SiO ２ The OH / SiO ratio of the raw material composition in the crystallization step (2) is preferably 0.30 or more, more preferably 0.35 or more, and even more preferably 0.40 or more. ２ The OH / SiO ratio of the raw material composition is preferably 0.70 or less, more preferably 0.65 or less, and even more preferably 0.60 or less. ２ The upper and lower limit values ​​of the ratio may be any combination of the above upper and lower limit values, but are preferably 0.30 or more and 0.70 or less, more preferably 0.35 or more and 0.65 or less, and even more preferably 0.40 or more and 0.60 or less. ２ When the ratio is within the above-mentioned range, the peaks in Table 3 are more likely to be included in the XRD pattern of the calcium-containing zeolite obtained by crystallization, making it easier to produce the zeolite of this embodiment.

[0100] The raw material composition in the crystallization step (2) is preferably a combination of any of the following molar compositions: SiO ２ / Al ２ O ３ Ratio M / SiO = 8 or more, 10 or more, or 13 or more, and 24 or less, 22 or less, or 20 or less ２ Ratio = 0.30 or more, or 0.35 or more, 0.40 or more and 0.70 or less, 0.65 or less, or 0.60 or less H ２ O / SiO２ Ca / SiO ratio = 3 or more, 5 or more, or 8 or more and 50 or less, 30 or less, or 25 or less ２ OH / SiO ratio = 0.001 or more or 0.003 or more and 0.030 or less or 0.020 or less ２ Ratio = 0.30 or more, 0.35 or more, or 0.40 or more, and 0.70 or less, 0.65 or less, or 0.60 or less

[0101] In the crystallization step (2), the above-mentioned raw material composition is crystallized in the presence of seed crystals to produce a calcium-containing zeolite (calcium-containing zeolite obtained by the production method (2)). The calcium-containing zeolite obtained by the production method (2) may be used in the copper-containing step as is, or may be used in the copper-containing step after being subjected to one or more treatments selected from the group consisting of a washing treatment, a drying treatment, a calcination treatment, and an ion exchange treatment. When the calcium-containing zeolite obtained by the production method (2) is subjected to an ion exchange treatment, the ion exchange treatment is carried out to change the cation type of the zeolite to a proton (H ＋ ) type or ammonium (NH ４ ＋ It is preferable that the cation type of the calcium-containing zeolite is a proton (H ＋ ) type or ammonium (NH ４ ＋ ) type, copper is more easily contained in the copper-containing step compared to other cation types.

[0102] The cleaning treatment, drying treatment, calcination treatment, and ion exchange treatment have been described above (these are the same as the cleaning treatment, drying treatment, calcination treatment, and ion exchange treatment that can be performed on calcium-containing zeolite containing copper), so detailed explanations will be omitted.

[0103] The calcium-containing zeolite obtained by the production method (1) or (2) can be used as the calcium-containing zeolite for incorporating copper in the copper-containing step (copper contact treatment) described above. By incorporating copper into the calcium-containing zeolite in the copper-containing step (copper contact treatment), the zeolite of the present embodiment can be produced.

[0104] From the viewpoint of making it easier to produce the zeolite of the present embodiment, the calcium-containing zeolite obtained by the production method (1) or the production method (2) is preferably a calcium-containing zeolite having an intergrowth structure including a CHA structure and a GME structure, and more preferably a calcium-containing zeolite having an intergrowth structure including a CHA structure and a GME structure and having at least the peaks in Table 3 above in its powder X-ray diffraction pattern.

[0105] SiO of calcium-containing zeolite obtained by production method (1) or production method (2) ２ / Al ２ O ３ The ratio is preferably 5.0 or more and 15 or less, more preferably 5.5 or more and 10 or less, and even more preferably 6.0 or more and 9.5 or less, because this makes it easier to obtain a zeolite having better SCR catalytic activity over a range from a low temperature (e.g., 150°C) region to a high temperature (e.g., 600°C) region.

[0106] Furthermore, from the viewpoint of making it easier to produce the zeolite of the present embodiment, the Ca / Al ratio of the calcium-containing zeolite obtained by Production Method (1) or Production Method (2) is preferably 0.01 or more and 0.3 or less, more preferably 0.015 or more and 0.25 or less, and even more preferably 0.02 or more and 0.15 or less.

[0107] The zeolite of the present embodiment described above has excellent hydrothermal durability and exhibits excellent SCR catalytic activity even after hydrothermal durability treatment. The reason why the zeolite of the present embodiment has excellent hydrothermal durability is not clear, but it is presumed that the coexistence of copper with calcium reduces the amount of zero-valent copper to a predetermined ratio or less, making it difficult for copper to be inactivated even after hydrothermal durability treatment, and as a result, the zeolite exhibits excellent SCR catalytic activity even after hydrothermal durability treatment.

[0108] The hydrothermal durability treatment is a treatment in which zeolite is exposed to a high-temperature atmosphere containing moisture, and a specific example is a treatment in which zeolite is exposed to an atmosphere containing moisture of 5% to 15% by volume and having a temperature of 600°C to 700°C. The time for the hydrothermal durability treatment is not particularly limited, but may be, for example, 1 hour to 150 hours. In the hydrothermal durability treatment, the atmospheric gas to which the zeolite is exposed may be any gas containing moisture, and exhaust gas, air, or the like may be used.

[0109] The SCR catalytic activity of the zeolite of this embodiment (SCR catalytic activity after hydrothermal durability treatment) is excellent over a range from low temperatures (for example, 150° C.) to high temperatures (for example, 600° C.) In particular, as shown in the examples described later, the zeolite of this embodiment has better SCR catalytic activity (SCR catalytic activity after hydrothermal durability treatment) at temperatures of 200° C. or less and even better SCR catalytic activity (SCR catalytic activity after hydrothermal durability treatment) at temperatures of 150° C. or more and 200° C. or less, compared to zeolites having the same configuration as the zeolite of this embodiment except that they do not contain calcium and zeolites having the same configuration as the zeolite of this embodiment except that they have an XPS area ratio of 34% or more, as shown in the examples described later.

[0110] The present embodiment will be described below with reference to examples, but the present embodiment is not limited to these examples.

[0111] (Identification of Crystal Structure) XRD measurement of the sample was performed using a powder X-ray diffractometer (device name: Ultima IV, manufactured by Rigaku Corporation). The measurement conditions were as follows: Acceleration current / voltage: 40 mA / 40 kV Radiation source: CuKα radiation (λ=1.5405 Å) Measurement mode: Continuous scan Scan condition: 40° / min Measurement range: 2θ=3° to 43° Divergence vertical limiting slit: 10 mm Divergence / entrance slit: 1° Receiving slit: open Receiving solar slit: 5° Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter

[0112] The obtained XRD pattern was analyzed using the analysis software provided with the instrument (software name: Smart Lab Studio II, manufactured by Rigaku Corporation) under the following conditions. Fitting conditions: Automatic, background refinement, distributed pseudo-Voigt function (peak shape) Background removal method: Fitting method Kα2 removal method: Kα1 / Kα2 ratio = 0.497 Smoothing method: Smoothing by B-Spline Smoothing conditions: Second-order differential method, σ cut value = 3, χ threshold = 1.5

[0113] (Composition Analysis) A typical inductively coupled plasma optical emission spectrometer (device name: OPTIMA 7300DV, manufactured by PERKIN ELMER) was used to perform composition analysis of the sample. The sample was dissolved in a mixed solution of hydrofluoric acid and nitric acid to prepare a measurement solution. The obtained measurement solution was used to determine the composition of the sample (SiO ２ / Al ２ O ３ The following parameters were analyzed: Ca / Al ratio, Ca / Al ratio, Cu / Al ratio.

[0114] (Analysis of the Chemical State of Copper) A common X-ray photoelectron spectrometer (device name: PHI5000VersaProbeII, manufactured by ULVAC-PHI) was used to analyze the chemical state of copper contained in the sample. The measurement conditions were as follows: X-ray source: Monochrome Al-Kα ray X-ray beam diameter: 100 μmφ Energy resolution: Wide scan spectrum 117.40 eV High resolution spectrum 46.95 eV (Cu2p ３／２ ) Charge correction: Al2p main peak (74.4 eV) No sputtering treatment

[0115] The peak area of ​​the XPS spectrum was calculated by dividing the measured XPS spectrum by a plurality of virtual lines spaced at intervals of 0.10 eV, calculating the area of ​​each trapezoid (a right-angled trapezoid enclosed by two adjacent virtual lines, a line connecting the intersection of the two virtual lines with the XPS spectrum curve, and the horizontal axis), and then adding up the areas of the individual trapezoids.

[0116] Example 1 A 50% by mass aqueous solution of sodium hydroxide, a 50% by mass aqueous solution of calcium nitrate, and an amorphous aluminosilicate (SiO ２ / Al ２ O ３ The raw material composition having the following molar composition was obtained by mixing SiO ２ / Al ２ O ３ Ratio = 15 Na / SiO ２ Ratio = 0.48 Ca / SiO ２ Ratio = 0.008H ２ O / SiO ２ Ratio = 12 OH / SiO ２ Ratio =0.48

[0117] Seed crystals (CHA-type zeolite; SiO ２ / Al ２ O ３ The seed crystals (ratio = 24) were mixed with the raw material composition, and then the mixture was filled into an 80 mL sealed container. After the mixture of seed crystals and raw material composition was filled, the container was subjected to hydrothermal treatment at 140°C for 20 hours under autogenous pressure while being rotary stirred at 55 rpm. The solid product obtained by the hydrothermal treatment was subjected to solid-liquid separation and washed with deionized water. The washed solid product was contacted with 100 ml of a 20% by mass aqueous ammonium chloride solution and dried overnight at 110°C in an air atmosphere to recover a crystallized product.

[0118] The crystallized product is SiO ２ / Al ２ O ３The crystallized product was found to be a calcium-containing zeolite having a Ca / Al ratio of 7.0 and a Ca / Al ratio of 0.02. Among the peaks contained in the XRD pattern of the crystallized product, peaks having a relative intensity of 10% or more relative to the peak at lattice spacing d = 4.99 are shown in Table 5 below. From the XRD pattern, it was confirmed that the obtained crystallized product was a calcium-containing zeolite (calcium-containing crystalline aluminosilicate) having an intergrowth structure including a CHA structure and a GME structure.

[0119]

[0120] (Copper Content) A copper nitrate solution was added dropwise to the obtained calcium-containing zeolite so that the copper content was 4 mass %, and the mixture was mixed in a mortar for 10 minutes. The zeolite was dried overnight at 110°C in an air atmosphere and then calcined at 550°C in an air atmosphere for 1 hour to obtain a zeolite containing calcium and copper (hereinafter also referred to as "Ca-Cu zeolite").

[0121] The Ca-Cu zeolite of this example is SiO ２ / Al ２ O ３ The Ca / Al ratio was 7.0, the Ca / Al ratio was 0.02, and the Cu / Al ratio was 0.18. Among the peaks contained in the XRD pattern of the Ca—Cu zeolite of this example, peaks having a relative intensity of 10% or more relative to the peak at lattice spacing d = 4.95 are shown in Table 6 below. From the XRD pattern, it was confirmed that the Ca—Cu zeolite of this example is a Ca—Cu zeolite (crystalline aluminosilicate containing calcium and copper) having an intergrowth structure including a CHA structure and a GME structure.

[0122] The Ca-Cu zeolite of this example had a binding energy peak position (eV) in the range of 930.0 eV to 940.0 eV in its XPS spectrum, and the XPS area ratio was 31%.

[0123] Example 2 A raw material composition having the following molar composition was obtained by changing the amounts of the raw materials added in Example 1. A crystallized product was obtained in the same manner as in Example 1, except that the obtained raw material composition was used. SiO ２ / Al２ O ３ Ratio = 15 Na / SiO ２ Ratio = 0.48 Ca / SiO ２ Ratio = 0.012H ２ O / SiO ２ Ratio = 12 OH / SiO ２ Ratio = 0.48

[0124] The crystallized product is SiO ２ / Al ２ O ３ The crystallized product was found to be a calcium-containing zeolite having a Ca / Al ratio of 7.7 and a Ca / Al ratio of 0.05. The XRD pattern of the crystallized product confirmed that the crystallized product was a calcium-containing zeolite (calcium-containing crystalline aluminosilicate) having an intergrowth structure including a CHA structure and a GME structure.

[0125] The obtained crystallized product was made to contain copper in the same manner as in Example 1, to obtain the Ca-Cu zeolite of this example. ２ / Al ２ O ３ The Ca / Al ratio was 7.7, the Ca / Al ratio was 0.05, and the Cu / Al ratio was 0.19. Among the peaks contained in the XRD pattern of the Ca—Cu zeolite of this example, XRD peaks having a relative intensity of 10% or more relative to the peak at lattice spacing d = 4.95 are shown in Table 7 below. From the XRD pattern, it was confirmed that the Ca—Cu zeolite of this example is a Ca—Cu zeolite (crystalline aluminosilicate containing calcium and copper) having an intergrowth structure including a CHA structure and a GME structure.

[0126] The Ca-Cu zeolite of this example had a binding energy peak position (eV) in the range of 930.0 eV to 940.0 eV in its XPS spectrum, and the XPS area ratio was 28%.

[0127] Example 3: The amounts of the raw materials added in Example 1 were changed to obtain a raw material composition having the following molar composition. A crystallized product was obtained in the same manner as in Example 1, except that the obtained raw material composition was used. SiO ２ / Al ２ O ３ Ratio = 15 Na / SiO ２ Ratio = 0.50 Ca / SiO ２ Ratio = 0.012H ２ O / SiO ２ =10OH / SiO ２ ratio =0.50

[0128] The crystallized product is SiO ２ / Al ２ O ３ The crystallized product was found to be a calcium-containing zeolite having a Ca / Al ratio of 7.4 and a Ca / Al ratio of 0.05. The XRD pattern of the crystallized product confirmed that the crystallized product was a calcium-containing zeolite (calcium-containing crystalline aluminosilicate) having an intergrowth structure including a CHA structure and a GME structure.

[0129] The obtained crystallized product was made to contain copper in the same manner as in Example 1, to obtain the Ca-Cu zeolite of this example. ２ / Al ２ O ３ The Ca / Al ratio was 7.4, the Ca / Al ratio was 0.05, and the Cu / Al ratio was 0.18. Among the peaks contained in the XRD pattern of the Ca—Cu zeolite of this example, peaks having a relative intensity of 10% or more to the peak at lattice spacing d = 4.96 are shown in Table 8 below. From the XRD pattern, it was confirmed that the Ca—Cu zeolite of this example is a Ca—Cu zeolite (crystalline aluminosilicate containing calcium and copper) having an intergrowth structure including a CHA structure and a GME structure.

[0130] The Ca-Cu zeolite of this example had a binding energy peak position (eV) in the range of 930.0 eV to 940.0 eV in its XPS spectrum, and the XPS area ratio was 31%.

[0131] Example 4 A raw material composition having the following molar composition was obtained by changing the amounts of the raw materials added in Example 1. A crystallized product was obtained in the same manner as in Example 1, except that the obtained raw material composition was used. SiO ２ / Al ２ O ３ =15 Na / SiO ２ Ratio = 0.48 Ca / SiO ２ Ratio = 0.017H ２ O / SiO ２ =12OH / SiO ２ Ratio = 0.48

[0132] The crystallized product is SiO ２ / Al ２ O ３ The crystallized product was found to be a calcium-containing zeolite having a Ca / Al ratio of 9.0 and a Ca / Al ratio of 0.10. The XRD pattern of the crystallized product confirmed that the crystallized product was a calcium-containing zeolite (calcium-containing crystalline aluminosilicate) having an intergrowth structure including a CHA structure and a GME structure.

[0133] The obtained crystallized product was made to contain copper in the same manner as in Example 1, to obtain the Ca-Cu zeolite of this example. ２ / Al ２ O ３ The Ca / Al ratio was 9.0, the Ca / Al ratio was 0.10, and the Cu / Al ratio was 0.20. Among the peaks contained in the XRD pattern of the Ca—Cu zeolite of this example, peaks having a relative intensity of 10% or more to the peak at lattice spacing d = 4.96 are shown in Table 9 below. From the XRD pattern, it was confirmed that the Ca—Cu zeolite of this example is a Ca—Cu zeolite (crystalline aluminosilicate containing calcium and copper) having an intergrowth structure including a CHA structure and a GME structure.

[0134] The Ca-Cu zeolite of this example had a binding energy peak position (eV) in the range of 930.0 eV to 940.0 eV in its XPS spectrum, and the XPS area ratio was 31%.

[0135] Example 5 In Example 1, a raw material composition having the following molar composition was obtained without using a calcium source and by changing the amounts of raw materials added. A crystallized product was obtained in the same manner as in Example 1, except that the obtained raw material composition was used. SiO ２ / Al ２ O ３ Ratio = 17 Na / SiO ２ Ratio = 0.50 Ca / SiO ２ Ratio = 0H ２ O / SiO ２ =12OH / SiO ２ ratio =0.50

[0136] The crystallized product is SiO ２ / Al ２ O ３ The zeolite had a Ca / Al ratio of 6.5 and a Ca / Al ratio of 0. Among the peaks contained in the XRD pattern of the crystallized product, XRD peaks having a relative intensity of 10% or more relative to the peak at lattice spacing d = 4.97 are shown in Table 10 below. From the XRD pattern, it was confirmed that the obtained crystallized product was a zeolite (crystalline aluminosilicate) having an intergrowth structure including a CHA structure and a GME structure.

[0137] (Calcium and Copper Content) A 50% by mass aqueous solution of calcium nitrate was added dropwise to the zeolite so that the calcium content was 0.75% by mass, and the mixture was impregnated and mixed in a mortar for 10 minutes. After the 10-minute impregnation and mixing, the zeolite was dried overnight at 110°C in an air atmosphere. After drying, a 50% by mass aqueous solution of copper nitrate was added dropwise to the zeolite so that the copper content was 4% by mass, and the mixture was impregnated and mixed in a mortar for 10 minutes. After the 10-minute impregnation and mixing, the zeolite was dried overnight at 110°C in an air atmosphere. The dried zeolite was calcined for 1 hour at 550°C in an air atmosphere to obtain the Ca-Cu zeolite of this example.

[0138] The Ca-Cu zeolite of this example is SiO ２ / Al ２ O ３ The Ca / Al ratio was 6.5, the Ca / Al ratio was 0.05, and the Cu / Al ratio was 0.18. Among the peaks contained in the XRD pattern of the Ca—Cu zeolite of this example, XRD peaks having a relative intensity of 10% or more relative to the peak at lattice spacing d = 4.95 are shown in Table 11 below. From the XRD pattern, it was confirmed that the Ca—Cu zeolite of this example is a Ca—Cu zeolite (crystalline aluminosilicate containing calcium and copper) having an intergrowth structure including a CHA structure and a GME structure.

[0139] The Ca-Cu zeolite of this example had a binding energy peak position (eV) in the range of 930.0 eV to 940.0 eV in its XPS spectrum, and the XPS area ratio was 25%.

[0140] Comparative Example 1 In Example 1, a raw material composition having the following molar composition was obtained without using a calcium source and by changing the amounts of raw materials added. A crystallized product was obtained in the same manner as in Example 1, except that the obtained raw material composition was used. SiO ２ / Al ２ O ３ =15 Na / SiO ２ Ratio = 0.50 Ca / SiO ２ Ratio = 0H ２ O / SiO ２ =10OH / SiO ２ ratio =0.50

[0141] The crystallized product is SiO ２ / Al ２ O ３The zeolite had a Ca / Al ratio of 7.3 and a Ca / Al ratio of 0. Among the peaks contained in the XRD pattern of the crystallized product, XRD peaks having a relative intensity of 10% or more relative to the peak at lattice spacing d = 4.99 are shown in Table 12 below. From the XRD pattern, it was confirmed that the obtained crystallized product was a zeolite (crystalline aluminosilicate) having an intergrowth structure including a CHA structure and a GME structure.

[0142] The obtained zeolite was made to contain copper in the same manner as in Example 1, to obtain the copper-containing zeolite of this comparative example. ２ / Al ２ O ３ The Ca / Al ratio was 7.3, the Ca / Al ratio was 0, and the Cu / Al ratio was 0.19. Among the peaks contained in the XRD pattern of the copper-containing zeolite of this comparative example, peaks having a relative intensity of 10% or more relative to the peak at lattice spacing d = 4.96 are shown in Table 13 below. From the XRD pattern, it was confirmed that the copper-containing zeolite of this comparative example is a copper-containing zeolite (copper-containing crystalline aluminosilicate) having an intergrowth structure including a CHA structure and a GME structure.

[0143] Since the copper-containing zeolite of this comparative example did not contain calcium, the XPS area ratio, which is an index for zeolites containing calcium and copper, could not be determined.

[0144] Comparative Example 2 A crystallized product was obtained in the same manner as in Example 5. The crystallized product was SiO ２ / Al ２ O ３ The zeolite had a Ca / Al ratio of 6.5 and a Ca / Al ratio of 0. Among the peaks contained in the XRD pattern of the crystallized product, peaks with a relative intensity of 10% or more relative to the peak at lattice spacing d = 4.96 were as shown in Table 10 above. From the XRD pattern, it was confirmed that the obtained crystallized product was a zeolite (crystalline aluminosilicate) having an intergrowth structure including a CHA structure and a GME structure.

[0145] (Copper and calcium content) A 50% by mass aqueous solution of copper nitrate was added dropwise to the zeolite so that the copper content was 4% by mass, and the mixture was impregnated and mixed in a mortar for 10 minutes. After the 10-minute impregnation and mixing, the zeolite was dried overnight at 110°C in an air atmosphere. After drying, a predetermined amount of a 50% by mass aqueous solution of calcium nitrate was added dropwise to the zeolite so that the calcium content was 0.75% by mass, and the mixture was impregnated and mixed in a mortar for 10 minutes. After the 10-minute impregnation and mixing, the zeolite was dried overnight at 110°C in an air atmosphere. The dried zeolite was calcined for 1 hour at 550°C in an air atmosphere to obtain the Ca-Cu zeolite of this comparative example.

[0146] The Ca-Cu zeolite of this comparative example is SiO ２ / Al ２ O ３ The Ca / Al ratio was 6.5, the Ca / Al ratio was 0.05, and the Cu / Al ratio was 0.18. Among the peaks contained in the XRD pattern of the Ca—Cu zeolite of this comparative example, peaks having a relative intensity of 10% or more to the peak at lattice spacing d = 4.96 are shown in Table 14 below. From the XRD pattern, it was confirmed that the Ca—Cu zeolite of this comparative example was a Ca—Cu zeolite (aluminosilicate containing calcium and copper) having an intergrowth structure including a CHA structure and a GME structure.

[0147] The Ca-Cu zeolite of this comparative example had a binding energy peak position (eV) in the range of 930.0 eV to 940.0 eV in its XPS spectrum, and the XPS area ratio was 34%.

[0148] Comparative Example 3 A crystallized product was obtained in the same manner as in Example 2. A 50% by mass aqueous solution of copper nitrate was added dropwise to the obtained crystallized product so that the copper content was 7% by mass, and the product was impregnated and mixed in a mortar for 10 minutes. After the 10-minute impregnation and mixing, the zeolite was dried overnight in an air atmosphere at 110°C. The dried zeolite was calcined in an air atmosphere at 550°C for 1 hour to obtain a Ca-Cu zeolite of this comparative example.

[0149] The Ca-Cu zeolite of this comparative example is SiO ２ / Al ２ O ３The Ca / Al ratio was 7.7, the Ca / Al ratio was 0.05, and the Cu / Al ratio was 0.34. Among the peaks contained in the XRD pattern of the Ca—Cu zeolite of this example, XRD peaks having a relative intensity of 10% or more relative to the peak at lattice spacing d = 4.95 are shown in Table 15 below. From the XRD pattern, it was confirmed that the Ca—Cu zeolite of this comparative example was a Ca—Cu zeolite (crystalline aluminosilicate containing calcium and copper) having an intergrowth structure including a CHA structure and a GME structure.

[0150] The Ca-Cu zeolite of this comparative example had a binding energy peak position (eV) in the range of 930.0 eV to 940.0 eV in its XPS spectrum, and the XPS area ratio was 45%.

[0151] (Hydrothermal Durability Treatment) The zeolites of each Example and Comparative Example were subjected to hydrothermal durability treatment. The hydrothermal durability treatment was carried out by the following method.

[0152] The zeolite of each example and comparative example was molded and pulverized to form agglomerated particles with an agglomeration diameter of 12 to 20 mesh. 3 mL of the resulting agglomerated particles was filled into an atmospheric pressure fixed-bed flow reactor, and then air containing 10% by volume of moisture was passed through and subjected to hydrothermal durability treatment under the following conditions: air flow rate: 300 mL / min, treatment temperature: 650°C, treatment time: 100 hours

[0153] (Method for measuring nitrogen oxide reduction rate (%)) The nitrogen oxide reduction rate (%) was determined for the zeolites of each example and each comparative example that had been subjected to hydrothermal durability treatment. The nitrogen oxide reduction rate was determined by the following method.

[0154] The zeolites of each Example and Comparative Example that had been subjected to hydrothermal durability treatment were molded and crushed to form agglomerated particles having an agglomerate diameter of 12 to 20 mesh. 1.5 mL of the agglomerated particles were packed 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 to determine the nitrogen oxide reduction rate.

[0155] The flow conditions of the nitrogen oxide-containing gas are as follows. The space velocity below is the flow rate of the nitrogen oxide-containing gas per volume of the zeolite-formed catalyst. Composition of the nitrogen oxide-containing gas: NO 200 ppm by volume NH ３ 200 ppm by volume O ２ 10% by volume (volume) H ２ O 3 volume (volume) % N ２ Remainder: Flow rate of nitrogen oxide-containing gas: 1.5 L / min Space velocity: 60,000 hr －１ Measurement temperature: 600°C or 150°C Gauge pressure: 0.01 MPa

[0156] The nitrogen oxide reduction rate was calculated from the following formula (1): Nitrogen oxide reduction rate (%) = {([NOx] in - [NOx] out) / [NOx] in} × 100 (1) In the above formula (1), [NOx] in is the nitrogen oxide concentration (ppm) of the nitrogen oxide-containing gas at the inlet of the atmospheric pressure fixed-bed flow-type reactor tube, and [NOx] out is the nitrogen oxide concentration (ppm) of the nitrogen oxide-containing gas at the outlet of the atmospheric pressure fixed-bed flow-type reactor tube.

[0157] Table 16 below shows the nitrogen oxide reduction rates at 150°C for the zeolites of each Example and Comparative Example that were subjected to hydrothermal durability treatment (hereinafter also referred to as "100-hour durability-treated samples").

[0158] From the above results, it was found that the Ca-Cu zeolites of the Examples had higher nitrogen oxide reduction rates at 150° C. after hydrothermal durability treatment than any of the zeolites of the Comparative Examples.

[0159] The nitrogen oxide reduction rates at 600°C of the 100-hour durability test samples are shown in Table 17 below.

[0160] From the above results, the Ca-Cu zeolites of Examples 1 to 3 had a higher nitrogen oxide reduction rate at 600°C after hydrothermal durability treatment than any of the zeolites of the comparative examples. These results show that the Ca-Cu zeolites of Examples 1 to 3 had a high nitrogen oxide reduction rate not only at 150°C but also at 600°C, even after hydrothermal durability treatment, and exhibited excellent SCR catalytic activity over a wide temperature range.

[0161] From the above results, it was understood that the Ca-Cu zeolites of Examples 1 to 5 have excellent hydrothermal durability and, compared to the zeolites of Comparative Examples 1 to 3, exhibit excellent SCR catalytic activity even after hydrothermal durability treatment.

[0162] The entire contents of the specification, claims and abstract of Japanese Patent Application No. 2024-49001, filed on March 26, 2024, are hereby incorporated by reference as the disclosure of the specification of the present disclosure.

Claims

1. A zeolite having an intergrowth structure including a CHA structure and a GME structure, having at least the peaks shown in the table below in a powder X-ray diffraction pattern, containing calcium and copper, and having an XPS spectrum in which the ratio of the spectral area in the range of 930.0 eV to 933.0 eV to the spectral area in the range of 930.0 eV to 940.0 eV is less than 34%.

2. The zeolite according to claim 1, wherein in the powder X-ray diffraction pattern, the ratio of the half-width of the peak at lattice spacing d = 4.29 ± 0.08 Å to the half-width of the peak at lattice spacing d = 4.97 ± 0.08 Å is 2.0 or more and 7.0 or less.

3. The zeolite according to claim 1 or 2, wherein the molar ratio of calcium to aluminum is 0.3 or less.

4. The zeolite according to any one of claims 1 to 3, wherein the molar ratio of calcium to aluminum is 0.01 or more and 0.3 or less.

5. The zeolite according to any one of claims 1 to 4, wherein the molar ratio of copper to aluminum is 0.05 or more and 0.4 or less.

6. The zeolite according to any one of claims 1 to 5, wherein the molar ratio of silica to alumina is 5.0 or more and 15 or less.

7. A zeolite according to any one of claims 1 to 6, wherein the ratio of the spectral area in the range of 930.0 eV to 933.0 eV in an XPS spectrum to the spectral area in the range of 930.0 eV to 940.0 eV in an XPS spectrum is 10% or more and less than 34%.

8. A method for producing the zeolite according to any one of claims 1 to 7, comprising a copper-containing step of incorporating copper into the calcium-containing zeolite.

9. A method for producing a zeolite according to claim 8, further comprising a crystallization step of crystallizing a composition containing an alumina source, a silica source, an alkali source, a calcium source, and water in the presence of seed crystals to obtain the calcium-containing zeolite.

10. The method for producing a zeolite according to claim 8, further comprising: a crystallization step of crystallizing a composition containing an alumina source, a silica source, an alkali source, and water in the presence of seed crystals to obtain a raw zeolite; and a calcium-incorporating step of incorporating calcium into the raw zeolite to obtain the calcium-containing zeolite.

11. A catalyst for selective reduction of nitrogen oxides, comprising the zeolite according to any one of claims 1 to 7.

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