Iron-containing FER-type zeolite and its manufacturing method

Abstract

To provide an FER type zeolite which generates less N2O in nitrogen oxide reduction than conventional iron-containing FER type zeolites and is industrially applicable or a production method for the same, or a nitrogen oxide reduction catalyst comprising the same.SOLUTION: An FER type zeolite contains iron and has an area ratio of the peak in the spectrum having a wavelength of 300 nm to 600 nm to the peak having a wavelength of 190 nm to 600 nm in a UV-VIS spectrum, where the area ratio is 20% or less.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an iron-containing FER-type zeolite and a method for producing the same. [Background technology]

[0002] FER-type zeolites containing iron as a transition metal element have been investigated as transition metal-containing zeolites that can be used as nitrogen oxide reduction catalysts in which the by-production of N2O is suppressed (for example, Patent Documents 1 to 4).

[0003] For example, Patent Documents 1 to 3 report that iron can be incorporated into FER zeolite by post-treatment by mixing FER zeolite with an aqueous solution containing an iron salt such as iron nitrate. Patent Document 4 reports that iron-containing FER zeolite can be directly obtained by crystallizing a raw material containing iron. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-510437 A [Patent Document 2] JP 2017-512630 A [Patent Document 3] JP 2007-537858 A [Patent Document 4] China Patent Publication No. 114345402 [Non-patent literature]

[0005] [Non-Patent Document 1] Catalysis Communications,2017,89,133-147 [Non-Patent Document 2] Journal of Catalysis,2009,261, 27-34 Summary of the Invention [Problem to be solved by the invention]

[0006] Compared with the FER zeolites containing iron by post-treatment disclosed in Patent Documents 1 to 3, the directly crystallized iron-containing FER zeolite disclosed in Patent Document 4 has high nitrogen oxide reduction properties. However, the crystallization in Patent Document 4 requires expensive hexamethylimine as an essential raw material, and the obtained FER zeolite is also expensive, making it difficult to apply industrially.

[0007] An object of the present disclosure is to provide at least one of a FER-type zeolite that produces less NO in nitrogen oxide reduction as compared with conventional iron-containing FER-type zeolites and that is industrially applicable, a method for producing the same, and a nitrogen oxide reduction catalyst containing the same. [Means for solving the problem]

[0008] In the present disclosure, the improvement of the nitrogen oxide reduction properties of iron-containing FER-type zeolite was studied. As a result, it was found that iron-containing FER-type zeolite can be directly crystallized without requiring an expensive organic structure-directing agent such as hexamethylimine by controlling the raw materials and conditions for crystallization. Furthermore, it was found that such iron-containing FER-type zeolite has a different state of iron existence and a high dispersion state of iron compared to conventional iron-containing FER-type zeolites, and further suppresses the generation of NO in nitrogen oxide reduction at low temperatures compared to conventional iron-containing FER-type zeolites.

[0009] That is, the present invention is as described in the claims, and the gist of the present disclosure is as follows. [1] FER-type zeolite that contains iron and has a UV-VIS spectrum peak area ratio of 300 nm to 600 nm to 190 nm to 600 nm of 20% or less. [2] The FER type zeolite according to the above [1], in which the area ratio of the peak in the UV-VIS spectrum having a wavelength of more than 400 nm and not more than 600 nm to the peak having a wavelength of 190 nm or more and not more than 600 nm is 20% or less. [3] The FER type zeolite according to [1] or [2] above, in which the area ratio of the peak in the UV-VIS spectrum having a wavelength of 190 nm or more and less than 300 nm to the peak having a wavelength of 190 nm or more and 600 nm or less is 80% or more. [4] The FER type zeolite according to any one of [1] to [3] above, having an iron content of 5 mass% or less. [5] The FER type zeolite according to any one of [1] to [4] above, wherein the molar ratio of silica to alumina is 5 or more and 50 or less. [6] The FER type zeolite according to any one of [1] to [5] above, containing one or more elements selected from the group consisting of copper (Cu), manganese (Mn), zirconium (Zr), yttrium (Y), cerium (Ce), lanthanum (La), and calcium (Ca). [7] A method for producing an FER type zeolite according to any one of the above [1] to [6], comprising a step of crystallizing a composition containing a silica-alumina source, an iron source, an alkali source, water, and seed crystals, and having a molar ratio of iron to silicon calculated as SiO2 of less than 0.1. [8] The method according to [7] above, wherein the alkali source comprises at least a sodium source or a potassium source.

[0010] [9] The method for producing an FER type zeolite according to the above [7] or [8], wherein the composition has the following molar composition: In the following molar composition, M is an alkali metal. SiO2 / Al2O3=5 to 50 Fe / SiO2=0 or more and less than 0.1 M / SiO2=0.05 or more and less than 0.40 K / M =0 or more and 0.9 or less H2O / SiO2=5 to 50

[10] The method according to any one of [7] to [9] above, wherein the seed crystals are one or more selected from the group consisting of CHA zeolite, AEI zeolite, MOR zeolite, FER zeolite and AFX zeolite.

[11] The method according to any one of [7] to

[10] above, wherein the content of seed crystals in the raw material composition is greater than 0% by mass and not more than 10% by mass.

[12] A method for producing the present invention according to at least one of [7] to

[11] above, which does not include a source of an organic structure directing agent.

[13] The method according to at least one of [7] to

[11] above, further comprising one or more organic structure directing agent sources selected from the group consisting of pyridine, pyrrolidine, cyclohexylamine and butylamine.

[14] A nitrogen oxide reduction catalyst comprising the FER type zeolite according to any one of [1] to [6] above.

[15] A method for reducing nitrogen oxides, comprising a step of contacting a nitrogen oxide-containing gas with a nitrogen oxide reduction catalyst containing the FER zeolite described in any one of [1] to [6] above. Effect of the Invention

[0011] According to the present disclosure, it is possible to provide at least one of a FER-type zeolite that produces less NO in nitrogen oxide reduction as compared with conventional iron-containing FER-type zeolites and that is industrially applicable, a method for producing the same, and a nitrogen oxide reduction catalyst containing the same. [Brief description of the drawings]

[0012] [Figure 1] UV-VIS spectrum of the iron-containing FER-type zeolite of Example 1 [Diagram 2] UV-VIS spectrum of the iron-containing FER-type zeolite of Example 1 (after waveform separation) [Diagram 3] UV-VIS spectrum of iron-containing FER-type zeolite of Example 3 [Figure 4]UV-VIS spectrum of iron-containing FER-type zeolite of Example 3 (after waveform separation) [Diagram 5] UV-VIS spectrum of iron-containing FER-type zeolite of Comparative Example 1 [Figure 6] UV-VIS spectrum of iron-containing FER-type zeolite of Comparative Example 1 (after waveform separation) DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the present disclosure will be described with reference to an example of an embodiment.

[0014] "Zeolite" is a compound in which the skeleton atoms (hereinafter also referred to as "T atoms") have a regular structure with oxygen (O) interposed therebetween, and the T atoms are at least one of metal atoms and / or metalloid atoms. The metal atoms include at least one selected from the group consisting of aluminum (Al), titanium (Ti), iron (Fe), zinc (Zn), gallium (Ga) and tin (Sn), with at least one of aluminum and iron being preferred, and aluminum being more preferred. The metalloid atoms include at least one selected from the group consisting of boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb) and tellurium (Te), with silicon being preferred.

[0015] A "zeolite-like substance" is a compound having a regular structure in which T atoms are oxygen-mediated, and the T atoms contain at least an atom other than a metal or a metalloid (hereinafter also referred to as a "nonmetal atom"). An example of a nonmetal atom is phosphorus (P). An example of a zeolite-like substance is a complex phosphorus compound containing phosphorus (P) as a T atom, such as aluminophosphate (AlPO) or silicoaluminophosphate (SAPO). For clarity, in this embodiment, zeolite does not include zeolite-like substances.

[0016] The "regular structure (hereinafter also referred to as "zeolite structure")" of zeolite or zeolite-like substances is a skeletal structure specified by a structure code (hereinafter also simply referred to as "structure code") defined by the Structure Commission of the International Zeolite Association. For example, the FER structure is a skeletal structure specified by the structure code "FER". The zeolite structure can be identified by comparing with the XRD pattern (hereinafter also referred to as "reference pattern") described in the CHA of Zeolite Framework Types on the IZA Structure Commission's homepage http: / / www.iza-struture.org / databases / . In this embodiment, the zeolite structure, skeletal structure, crystal structure, and crystal phase are each used synonymously.

[0017] In the present embodiment, the term "-type zeolite" such as "FER type zeolite" means a zeolite having a zeolite structure of the corresponding structure code.

[0018] An "aluminosilicate" is a composite oxide having a structure consisting of a repeating network of aluminum (Al) and silicon (Si) via oxygen (O). Among aluminosilicates, those that have a crystalline XRD peak in their powder X-ray diffraction (hereinafter also referred to as "XRD") pattern are called "crystalline aluminosilicates", and those that do not have a crystalline XRD peak are called "amorphous aluminosilicates".

[0019] The XRD pattern in this embodiment is an XRD pattern obtained by XRD measurement under the following conditions. Acceleration current / voltage: 40mA / 40kV Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Step scan Scan condition: 40° / min Measurement time: 3 seconds Measurement range: 2θ=3° to 43° Divergence vertical limit slit: 10mm Divergence / entrance slit: 1° Receiving slit: open Receiving solar slit: 5° Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter

[0020] The XRD pattern can be measured using a general powder X-ray diffractometer (e.g., Ultima IV Protectus, manufactured by Rigaku Corporation). A crystalline XRD peak is a peak whose peak top 2θ is specified and detected in an XRD pattern analysis using general analysis software, and in particular, an XRD peak whose half-width is 2θ=0.50° or less. [FER-type zeolite containing iron] The present embodiment is an FER type zeolite that contains iron and has a UV-VIS spectrum peak area ratio of 300 nm or more and 600 nm or less to 190 nm or more and 600 nm or less.

[0021] This embodiment is a FER-type zeolite containing iron (hereinafter also referred to as "iron-containing FER-type zeolite"), which is a zeolite having a crystal structure consisting of only the FER structure, and further, a FER-type crystalline aluminosilicate. By containing iron (Fe), it exhibits nitrogen oxide reduction properties. Furthermore, compared to FER-type zeolite containing copper, it can reduce nitrogen oxides while suppressing the generation of NO.

[0022] In the XRD pattern of the iron-containing FER type zeolite of this embodiment, the peak top of the XRD peak of the (200) plane is 2θ=9.5±0.2°.

[0023] In the iron-containing FER type zeolite of this embodiment, the area ratio of the peak of the spectrum having a wavelength of 300 nm or more and 600 nm or less to the peak having a wavelength of 190 nm or more and 600 nm or less in the UV-VIS spectrum (hereinafter also referred to as the "300 nm-600 nm spectrum intensity ratio") is 20% or less. In the UV-VIS spectrum of the iron-containing FER type zeolite, the presence of iron can be confirmed by the presence of a peak having a wavelength of 190 nm or more and 600 nm or less, and the more highly dispersed the iron is, the lower the wavelength of the peak can be confirmed. In the iron-containing FER type zeolite of this embodiment, iron is isolated iron (Fe 3+ ), iron cluster (Fe x O y In this embodiment, the peaks at wavelengths of 190 nm or more and less than 300 nm are isolated iron (Fe 3+ ), and the peaks at wavelengths between 300 and 400 nm correspond to iron clusters (Fe x O y ), and the peak with a wavelength of more than 400 nm and not exceeding 600 nm can be regarded as a peak corresponding to iron oxide (Fe2O3) particles. When the 300 nm-600 nm spectral intensity ratio exceeds 20%, the proportion of iron oxide and iron clusters in the iron contained in the FER zeolite becomes large even in the case where isolated iron is contained, and the nitrogen oxide reduction properties are only at the same level as those of conventional iron-containing FER zeolites. In the iron-containing FER type zeolite of this embodiment, the area ratio of the peak having a wavelength of 190 nm or more and less than 300 nm to the peak having a wavelength of 190 nm or more and less than 600 nm in the UV-VIS spectrum (hereinafter also referred to as the "190 nm-300 nm spectral intensity ratio") is 70% or more, 80% or more, or 90% or more, and is preferably 100% or less, less than 100%, or 99% or less, and examples of such ratios include 70% or more and 100% or less, 80% or more and less than 100%, or 90% or more and 99% or less. In the iron-containing FER type zeolite of this embodiment, the area ratio of the peak having a wavelength of 300 nm or more and 400 nm or less to the peak having a wavelength of 190 nm or more and 600 nm or less in the UV-VIS spectrum (hereinafter also referred to as the "300 nm-400 nm spectral intensity ratio") is 20% or less, 5.0% or less, 3.0% or less, or 1.0% or less, and preferably 0% or more, more than 0%, or 0.1% or more, and examples of such ratio include 0% or more and 20% or less, 0% or more and 5.0% or less, 0% or more and 3.0% or less, more than 0% and 3.0% or less, or 0.1% or more and 1.0% or less. In the iron-containing FER type zeolite of this embodiment, the area ratio of the peak having a wavelength of more than 400 nm and less than 600 nm to the peak having a wavelength of 190 nm or more and less than 600 nm in the UV-VIS spectrum (hereinafter also referred to as the "400 nm-600 nm spectral intensity ratio") is 20% or less, 5.0% or less, 3.0% or less, or 1.0% or less, and is preferably 0% or more, more than 0%, or 0.1% or more, and examples of this include 0% or more and less than 20%, 0% or more and less than 5.0%, 0% or more and less than 3.0%, more than 0% and less than 3.0%, or 0.1% or more and less than 1.0%. These spectral intensity ratios [%] correspond to the abundance ratios [%] of iron species in iron-containing FER-type zeolite. The 190-300 nm spectral intensity ratio corresponds to the abundance ratios [%] of isolated iron (Fe 3+ ), and the 300nm-400nm spectrum intensity ratio is iron cluster (Fe x O y ), and the 400nm-600nm spectral intensity ratio corresponds to the abundance ratio [%] of iron oxide particles (Fe2O3). Therefore, the iron-containing FER type zeolite of this embodiment can also be regarded as a FER type zeolite that contains iron and has a presence ratio of iron clusters and iron oxide particles of 20% or less, or the iron-containing FER type zeolite of this embodiment can also be regarded as a FER type zeolite that contains iron and has a presence ratio of isolated iron particles of 80% or more. Furthermore, in the iron-containing FER-type zeolite of this embodiment, the total presence ratio of isolated iron, iron clusters, and iron oxide particles is 100%, The proportion of isolated iron is preferably 70% or more, 80% or more, or 90% or more, and 100% or less, less than 100%, or 99% or less, and more preferably 70% or more and 100% or less, 80% or more and less than 100%, or 90% or more and 99% or less, The proportion of iron clusters is 20% or less, 5.0% or less, 3.0% or less, or 1.0% or less, and is preferably 0% or more, more than 0%, or 0.1% or more, and is preferably 0% or more and 20% or less, 0% or more and 5.0% or less, 0% or more and 3.0% or less, more than 0% and 3.0% or less, or 0.1% or more and 1.0% or less, and The proportion of iron oxide particles is 20% or less, 5.0% or less, 3.0% or less, or 1.0% or less, and is preferably 0% or more, more than 0%, or 0.1% or more, and is preferably 0% or more and 20% or less, 0% or more and 5.0% or less, 0% or more and 3.0% or less, more than 0% and 3.0% or less, or 0.1% or more and 1.0% or less. It can also be considered as an iron-containing FER-type zeolite.

[0024] The UV-VIS spectrum in this embodiment may be measured using a general ultraviolet-visible spectrophotometer (for example, an ultraviolet-visible spectrophotometer V-770 manufactured by JASCO Corporation) under the following conditions. Integrating sphere unit: ISN-923 (manufactured by JASCO Corporation) Measurement mode: Diffuse reflection method Wavelength: 190~700nm Temperature: room Slit width: 5nm Background: Barium sulfate

[0025] The obtained UV-VIS spectrum is corrected so that the reflectance of the iron-containing FER-type zeolite of this embodiment relative to the reflectance of barium sulfate at a wavelength of 700 nm (hereinafter also referred to as "γ∞" or "relative reflectance") is 1, and then the corrected UV-VIS spectrum is subjected to KM (Kubelka-Munk) transformation using the KM function (f(γ∞)) below. f(γ∞) = (1-γ∞) 2 / 2γ∞

[0026] The UV-VIS spectrum after KM conversion is fitted and separated using general analysis software (e.g., Fityk 0.9.8) and Gaussian as the fitting function, and then the peak areas are obtained for wavelengths of 190 nm or more and less than 300 nm, 300 nm or more and less than 400 nm, and 400 nm or more and less than 600 nm, and the sum of these is taken as the peak area for wavelengths of 190 nm or more and less than 600 nm. The area ratio can be calculated from the ratio of the peak area for each wavelength range to the obtained peak area for wavelengths of 190 nm or more and less than 600 nm.

[0027] In order to make it easier to exhibit practical nitrogen oxide reduction properties, the iron content can be 0.1 mass% or more, 0.5 mass% or more, or 1.0 mass% or more, and 5.0 mass% or less, or 3.5 mass% or less, and is preferably 0.1 mass% or more and 5.0 mass% or less, or 1.0 mass% or more and 5.0 mass% or less, or 1.0 mass% or more and 3.5 mass% or less.

[0028] In the present embodiment, the "iron content" is the mass ratio [mass %] of iron (Fe) to the mass of the iron-containing FER type zeolite. The mass of the iron-containing FER type zeolite is the total mass of aluminum in terms of Al2O3, silicon in terms of SiO2, and iron (Fe) contained in the iron-containing FER type zeolite. The mass of the iron-containing FER type zeolite may be determined by mass measurement after treatment in an air atmosphere at 100°C for 2 hours.

[0029] The iron-containing FER-type zeolite of the present embodiment preferably contains a large amount of isolated iron, and the content of isolated iron in the iron content (hereinafter, “isolated Fe 3+ The content of isolated Fe is preferably 1.0 mass% or more, 1.2 mass% or more, or 1.5 mass% or more. 3+ A high content is preferable, but in that case, isolated Fe 3+ The content is the same as the upper limit of the iron content, and is, for example, 5.0 mass% or less or 3.5 mass% or less. 3+The content may be 1.0% by mass or more and 5.0% by mass or less, 1.2% by mass or more and 3.5% by mass or less, or 1.5% by mass or more and 3.5% by mass or less. isolated Fe 3+ The content can be calculated by the following formula. isolated Fe 3+ Content [mass%] = Iron content [mass%] × isolated iron content [%] = Iron content [mass%] × 190nm-300nm spectrum intensity ratio [%] Similarly, the content of iron clusters in the iron content (hereinafter also referred to as the "cluster content") and the content of iron oxide particles in the iron content (hereinafter also referred to as the "iron oxide content") can be calculated by the following formulas, respectively. Cluster content [mass%] = Iron content [mass%] × isolated iron content [%] = Iron content [mass%] × 300nm-400nm spectrum intensity ratio [%] Iron oxide content [mass%] = Iron content [mass%] × isolated iron content [%] = Iron content [mass%] × 400nm-600nm spectrum intensity ratio [%]

[0030] In the iron-containing FER type zeolite of this embodiment, iron may be contained in a state where it functions as an active metal, and may be present on the surface, in pores, and at ion exchange sites of the FER type zeolite, and is preferably present at least in the pores. Note that, in the iron-containing FER type zeolite of this embodiment, iron does not have to be substituted into the framework structure.

[0031] The iron-containing FER type zeolite of this embodiment may contain iron as an active metal, but may also contain an active metal other than iron, such as one or more elements selected from the group consisting of copper (Cu), manganese (Mn), zirconium (Zr), yttrium (Y), cerium (Ce), lanthanum (La), and calcium (Ca), and further at least one of copper and manganese, or even copper.

[0032] The molar ratio of silica to alumina in the iron-containing FER type zeolite of this embodiment (hereinafter also referred to as the "SiO2 / Al2O3 ratio") may be any value that makes it difficult for crystal collapse to occur when exposed to a high-temperature, high-humidity atmosphere, and may be 5 or more, 10 or more, or 15 or more, and 50 or less, 30 or less, or 20 or less, and is preferably 5 or more and 50 or less, 10 or more and 30 or less, or 15 or more and 20 or less.

[0033] The iron-containing FER type zeolite of this embodiment does not substantially contain fluorine (F), and further preferably has a fluorine content of 0 ppm by mass. In consideration of measurement errors, the fluorine content of the iron-containing FER type zeolite of this embodiment may be equal to or lower than the measurement limit, and is preferably, for example, from 0 ppm by mass to 100 ppm by mass, further preferably from 0 ppm by mass to 50 ppm by mass, and further preferably from 0 ppm by mass to 5 ppm by mass.

[0034] The shape of the iron-containing FER type zeolite of this embodiment may be any shape depending on the application, and may be, for example, at least one of a powder and a molded body. In the case of a powder, the powder may be applied or wash-coated to a substrate such as a honeycomb to form a catalyst member. In the case of a molded body, the initial shape may be any shape depending on the application, and may be one or more selected from the group consisting of a sphere, an approximately sphere, an ellipse, a disk, a cylinder, a polyhedron, an irregular shape, and a petal shape.

[0035] The iron-containing FER type zeolite of the present embodiment can be used in known applications of zeolites, and can be used, for example, as one or more selected from the group consisting of catalysts, adsorbents, and carriers thereof, and can further be used as at least one of a catalyst and a catalyst carrier.

[0036] The iron-containing FER-type zeolite of this embodiment is suitable for use as at least one of a nitrogen oxide reduction catalyst and a support thereof, and further as a nitrogen oxide reduction catalyst, and further as a nitrogen oxide reduction catalyst by selective catalytic reduction.

[0037] For example, when the iron-containing FER type zeolite of this embodiment is used as a nitrogen oxide reduction catalyst, it may be used as a method for reducing nitrogen oxides, which includes a step of contacting the iron-containing FER type zeolite of this embodiment with a nitrogen oxide-containing gas (hereinafter also referred to as a "contact step").

[0038] The nitrogen oxide-containing gas may be any gas containing nitrogen oxides (NOx), and is preferably a gas containing at least dinitrogen monoxide (NO), and more preferably a gas containing one or more selected from the group consisting of nitric oxide, nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide, and dinitrogen monoxide, and even more preferably a gas containing one or more selected from the group consisting of nitric oxide, nitrogen dioxide, and dinitrogen monoxide. The nitrogen oxide-containing gas may contain components other than nitrogen oxides, and may contain one or more selected from the group consisting of hydrocarbons, carbon monoxide, carbon dioxide, hydrogen, nitrogen, oxygen, sulfur oxides, and water. Specific examples of nitrogen oxide-containing gases include waste gases discharged from internal combustion engines, and waste gases discharged from one or more selected from the group consisting of automobiles, ships, boilers, and gas turbines.

[0039] In the contact step, any conditions may be used so long as the iron-containing FER type zeolite of this embodiment comes into contact with the nitrogen oxide-containing gas, and examples of the contact conditions include the following conditions. Space velocity: 500,000~500,000 hours -1 , preferably 2,000 to 300,000 hours -1 Contact temperature: 120°C or higher and 600°C or lower, preferably 150°C or higher and 550°C or lower

[0040] The contact in the contact step is preferably carried out in the presence of a reducing agent, which may be one or more selected from the group consisting of ammonia, urea, organic amines, hydrocarbons, alcohols, ketones, carbon monoxide, and hydrogen, and may further include at least one of ammonia, hydrocarbons, urea, and organic amines, or may further include at least one of ammonia and hydrocarbons, or may further include ammonia. [Method of manufacturing iron-containing FER type zeolite] A preferred method for producing the iron-containing FER type zeolite of this embodiment includes a method for producing a FER type zeolite, the method including a step of crystallizing a composition that contains a silica-alumina source, an iron source, an alkali source, and water, and in which the molar ratio of iron to silicon calculated as SiO2 is less than 0.1.

[0041] Conventionally, there have been methods for producing iron-containing FER-type zeolite.

[0042] The manufacturing method of this embodiment includes a step of crystallizing a composition (hereinafter also referred to as a "raw material composition") that contains a silica-alumina source, an iron source, an alkali source, and water, and has a molar ratio of iron to silicon calculated as SiO2 of less than 0.1 (hereinafter also referred to as a "crystallization step").

[0043] The silica-alumina source is a compound containing aluminum (Al) and silicon (Si), and is preferably an amorphous compound containing aluminum and silicon. A specific silica-alumina source is an amorphous aluminosilicate. In this embodiment, it is considered that crystallization proceeds in a state where the dispersion of iron is promoted, compared with the case where an aluminum source and a silicon source are contained separately.

[0044] The iron source is a compound containing iron, and may be any iron compound that is uniformly dispersed in the raw material composition. Specific examples of the iron compound include at least one selected from the group consisting of iron nitrate, iron sulfate, iron oxide, iron chloride, and iron oxyhydroxide, at least one selected from the group consisting of iron hydroxide, iron sulfate, and iron nitrate, at least one selected from the group consisting of iron sulfate and iron nitrate, and at least one selected from the group consisting of iron sulfate.

[0045] The alkali source is a compound containing an alkali metal element, and examples thereof include compounds containing one or more selected from the group consisting of sodium, potassium, rubidium, and cesium, compounds containing one or more selected from the group consisting of sodium, potassium, and cesium, compounds containing at least one of sodium and potassium, and compounds containing sodium. Examples of the alkali source (hereinafter, when the alkali metal is sodium, etc., each is also referred to as a "sodium source" or the like) include one or more selected from the group consisting of hydroxides, fluorides, bromides, iodides, sulfates, nitrates, and carbonates, one or more selected from the group consisting of hydroxides, bromides, and iodides, or hydroxides, which contain the above-mentioned alkali metal elements.

[0046] Since the FER type zeolite becomes easy to crystallize without using an expensive organic structure-directing agent, the alkali source preferably contains at least a sodium source or a potassium source, more preferably contains at least a potassium source, even more preferably contains a sodium source and a potassium source, and even more preferably is a sodium source and a potassium source.

[0047] The water in the raw material composition may include not only pure water and ion-exchanged water, but also structural water, hydration water, and water contained in other starting materials such as solvents.

[0048] In addition, when the starting material such as an iron source contains an alkali metal element, the starting material may be regarded as an alkali source. Similarly, when the iron source contains aluminum, the iron source is also regarded as an alumina source.

[0049] Since the resulting FER zeolite is expensive, it is preferable that the raw material composition does not contain an organic structure directing agent (hereinafter also referred to as "SDA") source, and it is particularly preferable that the raw material composition does not contain hexamethyleneimine. On the other hand, in order to promote crystallization, the raw material composition may contain an SDA source. The organic structure directing agent source is at least one of SDA and its compounds capable of directing FER zeolite, and may be an amine compound capable of directing FER zeolite. In order to make the production method of this embodiment easy to apply industrially, it is preferable that the SDA source is an inexpensive amine compound, for example, amines other than hexamethyleneimine, further one or more selected from the group of pyridine, pyrrolidine, cyclohexylamine, and butylamine, and further one or more selected from the group of pyridine, pyrrolidine, and butylamine.

[0050] The molar ratio of iron to aluminum calculated as Al2O3 and silicon calculated as SiO2 in the raw material composition (hereinafter also referred to as "SiO2 / Al2O3") can be 5 or more, 10 or more, or 15 or more, and can be 50 or less, 30 or less, 25 or less, or 18 or less, and is preferably 5 or more and 50 or less, 10 or more and 30 or less, or 15 or more and 25 or less.

[0051] The molar ratio of iron to silicon calculated as SiO2 in the raw material composition (hereinafter also referred to as "Fe / SiO2") is less than 0.1, and preferably 0.05 or less or 0.03 or less. If Fe / SiO2 exceeds 0.1, iron will be incorporated into the FER zeolite in a low activity state, such as by agglomeration. The lower limit of Fe / SiO2 in the raw material composition may be more than 0, 0.001 or more, or 0.01 or more, for example, more than 0 and less than 0.1, more than 0 and 0.5 or less, 0.001 or more and 0.5 or less, 0.01 or more and 0.05 or less, or 0.01 or more and 0.03 or less.

[0052] The total molar ratio of alkali metal elements to silicon in terms of SiO2 in the raw material composition (hereinafter also referred to as "M / SiO2") is less than 0.40, 0.38 or less, or 0.30 or less, and preferably 0.05 or more, 0.20 or more, or 0.25 or more. Preferable M / SiO2 is 0.05 or more and less than 0.40, 0.20 or more and 0.38 or less, or 0.25 or more and 0.30 or less.

[0053] The total molar ratio of potassium to silicon calculated as SiO in the raw material composition (hereinafter also referred to as "K / SiO") can be less than 0.40, not more than 0.30, or not more than 0.15, and can be 0 or more, more than 0, or 0.1 or more, and is preferably more than 0 but less than 0.40, 0.1 or more and 0.30 or less, or 0.1 or more and 0.15 or less.

[0054] Since the iron-containing FER-type zeolite in which iron is more dispersed is more likely to crystallize, the molar ratio of water (H2O) to silicon calculated as SiO2 in the raw material composition (hereinafter also referred to as "H2O / SiO2") may be 50 or less, and preferably 40 or less or 25 or less. H2O / SiO2 may be 5 or more, 10 or more, or 13 or more, and preferably 5 or more and 40 or less, 10 or more and 40 or less, or 13 or more and 25 or less.

[0055] The following molar compositions are preferred compositions of the raw material composition: In the following molar compositions, M is an alkali metal, and when the alkali metals are sodium and potassium, for example, M can be regarded as (Na+K).

[0056] SiO2 / Al2O3=5 or more, 10 or more, or 15 or more, 50 or less, 30 or less, 25 or less, or 18 or less, Fe / SiO2=0 or more, 0.001 or more, 0.01 or more, or 0.02 or less above, Less than 0.1, 0.05 or less, or 0.03 or less M / SiO2=0.05 or more, 0.20 or more, or 0.25 or more, Less than 0.40, 0.38 or less, or 0.30 or less, K / M = 0 or more, more than 0, 0.10 or more, or 0.30 or more, 0.9 or less, 0.7 or less, or 0.5 or less, H2O / SiO2=5 or more, 10 or more, or 13 or more, 50 or less, 40 or less, or 25 or less

[0057] More preferred compositions of the raw material composition include the following molar compositions. SiO2 / Al2O3=5 to 50 Fe / SiO2=0 or more and less than 0.1 M / SiO2=0.05 or more and less than 0.40 K / M =0 or more and 0.9 or less H2O / SiO2=5 to 50 Particularly preferred compositions of the raw material composition include the following molar compositions. SiO2 / Al2O3=10 or more, 30 or less Fe / SiO2=0.01 or more and 0.05 or less M / SiO2=0.20 or more and 0.38 or less K / M =0.10 or more and 0.7 or less H2O / SiO2=5 to 25

[0058] In order to facilitate application of manufacturing equipment made of general-purpose materials, the raw material composition preferably does not contain fluorine (F) and phosphorus (P), and the fluorine content is preferably 100 mass ppm or less, and more preferably below the detection limit (10 mass ppm or less).Similarly, the phosphorus content is preferably 100 mass ppm or less, and more preferably below the detection limit (0.01 mass ppm or less).

[0059] In order to promote the crystallization of the raw material composition, the raw material composition may contain seed crystals. The seed crystals may be any zeolite that promotes the crystallization of FER type zeolite, and are preferably one or more selected from the group consisting of CHA type zeolite, AEI type zeolite, MOR type zeolite, FER type zeolite, and AFX type zeolite, and more preferably FER type zeolite.

[0060] In the crystallization step, the raw material composition is crystallized. As a result, iron-containing FER type zeolite can be obtained as a crystallized product. The crystallization may be performed by hydrothermal treatment under conditions that allow the iron-containing FER type zeolite to crystallize. Preferable crystallization conditions include the following conditions. Pressure: Natural pressure Crystallization temperature: 100°C or higher, 160°C or higher, or 175°C or higher, and 200℃ or less or 190℃ or less

[0061] The crystallization time may be any time that allows the iron-containing FER type zeolite to be sufficiently crystallized, and may be appropriately set depending on the amount of the raw material composition to be subjected to the crystallization and the crystallization method. Examples of the crystallization time include 4 hours or more, 8 hours or more, 24 hours or more, or 48 hours or more, and 150 hours or less, 100 hours or less, or 80 hours or less. In order to produce the iron-containing FER type zeolite with practical productivity, the crystallization time is preferably 4 hours or more and 150 hours or less, 8 hours or more and 100 hours or less, or 24 hours or more and 48 hours or less.

[0062] In order to allow the crystallization to proceed more uniformly, it is preferable to carry out the crystallization while the raw material composition is being stirred. The stirring may be performed by directly stirring the raw material composition, or by stirring a container containing the raw material composition.

[0063] The crystallized product (iron-containing FER-type zeolite) may be recovered by any method, for example, by solid-liquid separation, washing, drying, and then recovering the product.

[0064] The solid-liquid separation may be any method capable of separating the raw material composition after crystallization into a solid content (crystallized material) and a liquid phase, and examples thereof include one or more methods selected from the group consisting of filtration, decantation, and centrifugation.

[0065] The washing may be carried out by any method capable of removing impurities contained in the recovered crystallized material, for example, washing with pure water.

[0066] The drying may be performed by any method capable of removing moisture physically adsorbed on the crystallized product, for example, at least one of static drying and spray drying, in the air at 100° C. or higher and 120° C. or lower.

[0067] In order to remove SDA contained in the iron-containing FER-type zeolite (crystallized product after crystallization), the manufacturing method of this embodiment may include a step of removing an organic structure-directing agent from the crystallized product (hereinafter, also referred to as an "SDA removal step"). In the SDA removal step, any SDA removal method may be used, and examples thereof include one or more selected from the group consisting of liquid phase treatment with an acidic aqueous solution, exchange treatment with a resin, pyrolysis treatment, and calcination treatment. From the viewpoint of manufacturing efficiency, the SDA removal step is preferably at least one of pyrolysis treatment and calcination treatment, and calcination treatment is more preferable. Examples of preferable calcination conditions include the following conditions. Firing atmosphere: Air Firing temperature: 400°C or higher or 560°C or higher, and 700℃ or less or 650℃ or less

[0068] The calcination time may be appropriately set depending on the crystallized material to be calcined and the calcination method, and may be, for example, from 1 hour to 10 hours, from 2 hours to 8 hours, or from 3 hours to 5 hours.

[0069] The production method of this embodiment may include a step of ion-exchanging the iron-containing FER type zeolite in order to reduce the content of alkali metals in the iron-containing FER type zeolite (hereinafter, also referred to as an "ion-exchanging step"). The ion-exchanging may be a method that reduces the content of alkali metals, and an example of the ion-exchanging method is mixing the iron-containing FER type zeolite with an aqueous ammonium chloride solution.

[0070] If necessary, the iron-containing FER-type zeolite after ion exchange may be calcined.

[0071] The production method of this embodiment may include a step of mixing the iron-containing FER type zeolite with a metal compound (hereinafter, also referred to as a "metal supporting step") in addition to or instead of the ion exchange step. This allows any metal element depending on the purpose to be supported on the iron-containing FER type zeolite.

[0072] The mixing method may be any method that can support the metal compound on the iron-containing FER type zeolite, and may be one or more methods selected from the group consisting of ion exchange method, impregnation support method, evaporation to dryness method, precipitation support method, and physical mixing method. EXAMPLES

[0073] The present disclosure will be described below with reference to examples. However, the present disclosure is not limited to the following. Evaluation methods are shown below. (Crystal Identification) The samples were subjected to XRD measurement using a powder X-ray diffractometer (Ultima IV, manufactured by Rigaku Corporation) under the following measurement conditions: Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Step scan Scan condition: 40° / min Measurement time: 3 seconds Measurement range: 2θ=5° to 43°

[0074] (composition analysis) A sample solution was prepared by dissolving the sample in a mixed aqueous solution of hydrofluoric acid and nitric acid. The sample solution was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES) using an ICP device (device name: OPTIMA5300DV, manufactured by PerkinElmer). (Measurement of iron dispersion) The UV-Vis spectrum of the sample was measured using an ultraviolet-visible spectrophotometer (apparatus name: ultraviolet-visible spectrophotometer V-770, manufactured by JASCO Corporation). The measurement conditions were as follows: Integrating sphere unit: ISN-923 (manufactured by JASCO Corporation) Measurement mode: Diffuse reflection method Wavelength: 190~700nm Temperature: room temperature Slit width: 5nm Background: Barium sulfate The obtained UV-Vis spectrum was fitted and separated using a general analysis software (software name: Fityk 0.9.8) with a Gaussian fitting function, and the peak areas of the wavelengths 190 nm to 300 nm, 300 nm to 400 nm, and 400 nm to 600 nm were calculated. The 300 nm-600 nm spectrum intensity ratio [%] and the 190 nm-300 nm spectrum intensity ratio (isolated iron (Fe 3+ ) abundance ratio [%], 300nm-400nm spectrum intensity ratio (cluster iron (Fe x O y The proportion of iron oxide particles (Fe2O3) present [%] and the 400nm-600nm spectral intensity ratio (proportion of iron oxide particles (Fe2O3) present [%]) were calculated. In addition, the content of each iron species was calculated from the proportion of isolated iron and the iron content calculated by the composition analysis described above using the following formula. isolated Fe 3+ Content [mass%] = Iron content [mass%] × isolated iron (Fe 3+ ) Presence ratio [%] = Iron content [mass%] × 190nm-300nm spectrum intensity ratio [%] Cluster content [mass%] = Iron content [mass%] × isolated iron content [%] = Iron content [mass%] × 300nm-400nm spectrum intensity ratio [%] Iron oxide content [mass%] = Iron content [mass%] × isolated iron content [%] = Iron content [mass%] × 400nm-600nm spectrum intensity ratio [%]

[0075] Example 1 A 48% by mass aqueous solution of sodium hydroxide, a 48% by mass aqueous solution of potassium hydroxide, iron (III) nitrate nonahydrate, pure water and amorphous aluminosilicate (SiO2 / Al2O3=17.9) were mixed to obtain a raw material composition having the following molar composition.

[0076] SiO2 / Al2O3=17.9 Fe / SiO2=0.016 (Na+K) / SiO2=0.280 (Na / SiO2=0.163, K / SiO2=0.117) K / (Na+K) = 0.418 H2O / SiO2=16 The obtained raw material composition was mixed with FER type zeolite (SiO2 / Al2O3=18.0) so that the seed crystal content was 2.0 mass%. The mixed raw material composition was filled into an 80 mL sealed container, which was rotated at 55 rpm and hydrothermally treated at 180°C for 40 hours to obtain a crystallized product. The obtained crystallized product was separated into solid and liquid, washed with pure water, and then dried at 110°C in the air and collected. The crystallized product was a zeolite consisting of a single phase of FER type zeolite, and had a SiO2 / Al2O3 of 18.0.

[0077] The obtained crystallized product was calcined in air at 600° C. for 2 hours, and then ion-exchanged with a 20% by mass aqueous solution of ammonium chloride at 60° C. The crystallized product after ion exchange was washed with a sufficient amount of pure water and dried in air at 110° C. to obtain the iron-containing FER-type zeolite of this example.

[0078] The iron-containing FER-type zeolite of this example was a zeolite consisting of a single phase of FER-type zeolite, with a SiO2 / Al2O3 of 18.0, an alkali metal content of less than 0.1 mass%, and an Fe content of 1.4 mass%. In addition, the 190-300 nm spectrum intensity ratio (proportion of isolated iron) was 99.8%, the 300-400 nm spectrum intensity ratio (proportion of cluster iron) was 0.2%, the 400-600 nm spectrum intensity ratio (proportion of iron oxide particles) was 0%, and the 300-600 nm spectrum intensity ratio was 0.2%, indicating that isolated Fe 3+The content was 1.4 mass %. In addition, the 2θ of the peak top of the XRD peak of the (200) plane was 9.3.

[0079] Example 2 The iron-containing FER-type zeolite of this example was obtained in the same manner as in Example 1, except that the raw material composition had the following molar composition. SiO2 / Al2O3=17.9 Fe / SiO2=0.024 (Na+K) / SiO2=0.305 Na / SiO2=0.177, K / SiO2=0.128) K / (Na+K) = 0.420 H2O / SiO2=16

[0080] The iron-containing FER type zeolite of this example was a zeolite consisting of a single phase of FER type zeolite, with SiO2 / Al2O3 of 18.2, an alkali metal content of less than 0.1 mass%, and an Fe content of 2.0 mass%. In addition, the 2θ of the peak top of the XRD peak of the (200) plane was 9.3.

[0081] Example 3 The iron-containing FER-type zeolite of this example was obtained in the same manner as in Example 1, except that the raw material composition had the following molar composition. SiO2 / Al2O3=17.9 Fe / SiO2=0.037 (Na+K) / SiO2=0.350 (Na / SiO2=0.203, K / SiO2=0.147) K / (Na+K) = 0.420 H2O / SiO2=16

[0082] The iron-containing FER-type zeolite of this example was a zeolite consisting of a single phase of FER-type zeolite, with a SiO2 / Al2O3 of 18.4, an alkali metal content of less than 0.1 mass%, and an Fe content of 3.0 mass%. In addition, the 190-300 nm spectrum intensity ratio (proportion of isolated iron) was 99.7%, the 300-400 nm spectrum intensity ratio (proportion of cluster iron) was 0.3%, the 400-600 nm spectrum intensity ratio (proportion of iron oxide particles) was 0%, and the 300-600 nm spectrum intensity ratio was 0.3%, indicating that isolated Fe 3+ The content was 3.0 mass %. In addition, the 2θ of the peak top of the XRD peak of the (200) plane was 9.3.

[0083] Comparative Example 1 Crystallization, solid-liquid separation, washing and drying were carried out in the same manner as in Example 1, except that the raw material composition was changed to the following composition, to obtain a crystallized product. SiO2 / Al2O3=19.0 (Fe / SiO2=0) (Na+K) / SiO2=0.19 (Na / SiO2=0.114, K / SiO2=0.076) K / (Na+K) = 0.400 H2O / SiO2=16

[0084] The obtained crystallized product was a zeolite consisting of a single phase of FER type zeolite, and the SiO2 / Al2O3 was 18.7.

[0085] The obtained crystallized material was calcined at 600°C for 2 hours in air. The calcined solid was exchanged with 20% by mass of ammonium chloride aqueous solution (ammonium chloride aqueous solution weight:zeolite weight=1.0) at 60°C, then washed with a large amount of water and dried at 110°C. The alkali metal content in the dried sample was less than 0.1% by mass. Next, 7.0 g of the dried sample, 1.6 g of iron (III) nitrate nonahydrate, and 2.4 g of pure water were mixed in a mortar. Finally, the homogeneously mixed sample was dried at 110°C for 5 hours in air, and then calcined at 500°C for 2 hours to obtain the iron-containing FER-type zeolite of this comparative example.

[0086] The iron-containing FER zeolite of this comparative example was a zeolite consisting of a single phase of FER zeolite, with a SiO2 / Al2O3 of 18.7, an alkali metal content of less than 0.1 mass%, and an Fe content of 3.0 mass%. The 190-300 nm spectrum intensity ratio (proportion of isolated iron) was 29.6%, the 300-400 nm spectrum intensity ratio (proportion of cluster iron) was 23.2%, the 400-600 nm spectrum intensity ratio (proportion of iron oxide particles) was 47.2%, and the 300-600 nm spectrum intensity ratio was 70.4%, indicating that isolated Fe 3+ The content was 0.9 mass %.

[0087] The iron-containing FER-type zeolite of this comparative example has a lower proportion of isolated iron despite having the same iron content as the iron-containing FER-type zeolite of Example 3, and has a higher proportion of isolated Fe than the iron-containing FER-type zeolite of Example 1. 3+ The content was confirmed to be low.

[0088] [Table 1]

[0089] This example confirmed that iron-containing FER-type zeolite containing dispersed iron, that is, iron-containing FER-type zeolite having a low 300 nm-600 nm spectral intensity ratio, can be obtained without the need for expensive SDA.

[0090] Measurement example <Hydrothermal durability treatment> The iron-containing FRR-type zeolite obtained in each of the examples and comparative examples was molded and pulverized to form agglomerated particles having an agglomeration diameter of 12 to 20 mesh. 3 mL of the obtained agglomerated particles was packed into an atmospheric pressure fixed-bed flow-type reactor, and then air containing 20% ​​by volume of moisture was passed through the reactor under the following conditions to perform hydrothermal durability treatment. Air flow rate: 300mL / min Processing temperature: 700℃ Processing time: 20 hours

[0091] <Nitrogen oxide reduction treatment> 1.5 mL of the aggregated particulate sample was packed into an atmospheric pressure fixed bed flow type reactor, and nitrogen oxide-containing gas was passed through the reactor while maintaining the temperature at the following measurement temperature, and the nitrogen oxide concentrations at the inlet and outlet of the atmospheric pressure fixed bed flow type reactor were measured. The flow conditions for the nitrogen oxide-containing gas were as follows:

[0092] Composition of nitrogen oxide-containing gas: NO 200 ppm by volume NH3 200 ppm by volume O2 10% by volume H2O 3% by volume N2 remainder Flow rate of nitrogen oxide-containing gas: 1.5L / min Space velocity: 60,000hr -1 Measurement temperature: 150℃, 200℃, 300℃, 500℃, 5 50℃ or 600℃

[0093] The nitrogen oxide reduction rate was calculated from the obtained nitrogen oxide concentration according to 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 atmospheric pressure fixed-bed flow reactor, and [NOx]out is the nitrogen oxide concentration of the nitrogen oxide-containing gas at the outlet of the atmospheric pressure fixed-bed flow reactor.

[0094] In addition, the amount of N2O contained in the nitrogen oxide-containing gas at the outlet of the atmospheric pressure fixed-bed flow-type reactor was measured and regarded as the amount of N2O produced.

[0095] Table 2 shows the evaluation results of the amount of NO generated from the iron-containing FER-type zeolite before hydrothermal durability treatment in the nitrogen oxide reduction treatment at 150°C to 300°C, and Table 3 shows the evaluation results of the amount of NO generated from the iron-containing FER-type zeolite after hydrothermal durability treatment in the nitrogen oxide reduction treatment at 150°C to 300°C.

[0096] [Table 2]

[0097] It was confirmed that the iron-containing FER type zeolite of the examples suppresses the generation of N2O in the nitrogen oxide reduction treatment in the low temperature range of 150°C to 200°C and the medium temperature range of 300°C. In particular, the iron-containing FER type zeolite of Example 3 and the iron-containing FER type zeolite of Comparative Example 1 both have an iron content of 3 mass%. However, it was confirmed that the iron-containing FER type zeolite of Example 3 significantly suppresses the generation of N2O in the nitrogen oxide reduction treatment in the low temperature range of 150°C to 200°C and the medium temperature range of 300°C, compared with the iron-containing FER type zeolite of Comparative Example 1 obtained by the post-supporting method.

[0098] [Table 3]

[0099] It was confirmed that, compared with the iron-containing zeolite of Comparative Example 1, the iron-containing FER-type zeolite of the Example suppressed the generation of N2O in the nitrogen oxide reduction treatment at a low temperature range of 150°C to 300°C, even after the hydrothermal durability treatment.

[0100] Next, the evaluation results of the amount of NO generated from the iron-containing FER-type zeolite before hydrothermal durability treatment in the high-temperature nitrogen oxide reduction treatment are shown in Table 4, and the evaluation results of the amount of NO generated from the iron-containing FER-type zeolite after hydrothermal durability treatment in the high-temperature nitrogen oxide reduction treatment are shown in Table 5.

[0101] [Table 4]

[0102] In nitrogen oxide reduction treatment at high temperatures of 500°C or higher, it was confirmed that the iron-containing FER-type zeolite of Example 1 produced virtually no NO, despite the fact that it contained not only iron, which is an active component, but also a small amount of iron clusters, which are considered to be active species at high temperatures.

[0103] [Table 5]

[0104] It was confirmed that, compared with the iron-containing zeolite of Comparative Example 1, the iron-containing FER-type zeolite of Example 3 suppressed the generation of N2O in nitrogen oxide reduction treatment at high temperatures of 500°C or higher, even after hydrothermal durability treatment.

[0105] Next, the ratio of the nitrogen oxide reduction rate (%) after the hydrothermal durability treatment to the nitrogen oxide reduction rate (%) before the hydrothermal durability treatment (maintenance rate of the nitrogen oxide reduction rate) is shown.

[0106] [Table 6]

[0107] It was confirmed that, compared to the iron-containing FER-type zeolite of Comparative Example 1, the iron-containing FER-type zeolite of the Example exhibited stable nitrogen oxide reduction properties over a wide temperature range of the nitrogen oxide reduction treatment from low to high temperatures.

[0108] Furthermore, the nitrogen oxide reduction ratio after hydrothermal durability treatment in a nitrogen oxide reduction treatment at 550° C. was 75% for the iron-containing FER-type zeolite of Comparative Example 1, whereas it was 77%, 73% and 81%, respectively, for Examples 1 to 3. From this, it was confirmed that, although the iron-containing FER-type zeolite of this example does not substantially contain iron clusters, which are considered to be active species in a high temperature range, it exhibits a nitrogen oxide reduction ratio after hydrothermal durability treatment in a nitrogen oxide reduction treatment in a high temperature range that is equal to or higher than that of conventional iron-containing FER-type zeolites that contain iron clusters.

Claims

1. A FER-type zeolite containing iron, silicon, and aluminum, having an iron content of 0.5% by mass or more and 5% by mass or less, a molar ratio of silica to alumina of 5 to 50, and an area ratio of a peak in a spectrum having a wavelength of 300 nm or more and 600 nm or less to a peak in a wavelength of 190 nm or more and 600 nm or less in a UV-VIS spectrum of 20% or less.

2. The FER type zeolite according to claim 1, wherein the area ratio of a peak having a wavelength of more than 400 nm and not more than 600 nm to a peak having a wavelength of 190 nm or more and not more than 600 nm in a UV-VIS spectrum is 5% or less.

3. 3. The FER type zeolite according to claim 1 or 2, wherein the area ratio of the peak in the spectrum having a wavelength of 190 nm or more and less than 300 nm to the peak in the wavelength of 190 nm or more and 600 nm or less in the UV-VIS spectrum is 80% or more.

4. A FER type zeolite as described in claim 1 or 2, in which the area ratio of the peak with a wavelength of 300 nm or more and 400 nm or less to the peak with a wavelength of 190 nm or more and 600 nm or less in the UV-VIS spectrum is 0% or more and 5.0% or less.

5. The FER type zeolite described in claim 1 or 2, wherein the FER type zeolite is a FER type crystalline aluminosilicate.

6. The FER type zeolite according to claim 1 or 2, containing one or more elements selected from the group consisting of copper (Cu), manganese (Mn), zirconium (Zr), yttrium (Y), cerium (Ce), lanthanum (La), and calcium (Ca).

7. A silica-alumina source, an iron source, an alkali source, water, and a seed crystal are contained, and SiO ２ 2. A method for producing a FER type zeolite according to claim 1, comprising a step of crystallizing a composition having a molar ratio of iron to silicon converted to less than 0.

1.

8. The method according to claim 7, wherein the alkali source comprises at least a sodium source or a potassium source.

9. The method for producing FER type zeolite according to claim 7 or 8, wherein the composition has the following molar composition: In the following molar composition, M is an alkali metal. SiO ２ / Al ２ O ３ =5 or more but less than 50 Fe / SiO ２ = More than 0 and less than 0.1 M / SiO ２ = 0.05 or more and less than 0.40 K / M = 0 or more and 0.9 or less H ２ O / SiO ２ =5 or more but less than 50

10. The method according to claim 7 or 8, wherein the seed crystals are one or more selected from the group consisting of CHA type zeolite, AEI type zeolite, MOR type zeolite, FER type zeolite and AFX type zeolite.

11. The method according to claim 7 or 8, wherein the content of seed crystals in the composition is greater than 0% by mass and is not more than 10% by mass.

12. 9. The process of claim 7 or 8, which does not include a source of organic structure directing agent.

13. 9. The process according to claim 7 or 8, further comprising one or more organic structure directing agent sources selected from the group consisting of pyridine, pyrrolidine, cyclohexylamine and butylamine.

14. A nitrogen oxide reduction catalyst comprising the FER type zeolite according to claim 1 or 2.

15. 3. A method for reducing nitrogen oxides, comprising a step of contacting a nitrogen oxide-containing gas with a nitrogen oxide reduction catalyst comprising the FER zeolite according to claim 1 or 2.

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