Iron-containing FER type zeolite and production method of the same

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 Art

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

[0003] For example, in Patent Documents 1 to 3, it has been reported that iron can be contained in the FER-type zeolite by mixing the FER-type zeolite with an aqueous solution containing an iron salt such as iron nitrate and then performing post-treatment. Further, in Patent Document 4, it has been reported that an iron-containing FER-type zeolite can be directly obtained by crystallizing a raw material containing iron.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

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

[0007] The present disclosure aims to provide at least one of an FER-type zeolite in which the generation of N2O in nitrogen oxide reduction is less than that of conventional iron-containing FER-type zeolites and which is industrially applicable, a method for producing the same, and a nitrogen oxide reduction catalyst containing the same.

Means for Solving the Problems

[0008] In the present disclosure, improvement of the nitrogen oxide reduction characteristics of an FER-type zeolite containing iron was investigated. As a result, it was found that by controlling the raw materials and conditions for crystallization, an FER-type zeolite containing iron can be directly crystallized without using an expensive organic structure-directing agent such as hexamethylimine. Furthermore, it was found that such an FER-type zeolite containing iron has a different state of iron existence and a higher iron dispersion state compared with a conventional FER-type zeolite containing iron, and that the generation of N2O in nitrogen oxide reduction in a low temperature range can be further suppressed compared with a conventional FER-type zeolite containing iron.

[0009] That is, the present invention is as described in the claims, and the gist of the present disclosure is as follows. [1] An FER-type zeolite containing iron and having an area ratio of the peak of the spectrum at a wavelength of 300 nm or more and 600 nm or less to the peak of the spectrum at a wavelength of 190 nm or more and 600 nm or less in the UV-VIS spectrum of 20% or less. [2] The FER-type zeolite according to [1] above, wherein the area ratio of the peak of the spectrum at a wavelength of more than 400 nm and 600 nm or less to the peak of the spectrum at a wavelength of 190 nm or more and 600 nm or less in the UV-VIS spectrum is 20% or less. [3] The FER-type zeolite according to [1] or [2] above, wherein the area ratio of the peak of the spectrum at a wavelength of 190 nm or more and less than 300 nm to the peak of the spectrum at a wavelength of 190 nm or more and 600 nm or less in the UV-VIS spectrum is 80% or more. [4] The FER-type zeolite according to any one of [1] to [3] above, wherein the iron content is 5% by 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 the FER-type zeolite according to any one of [1] to [6] above, comprising a step of crystallizing a composition containing a silica-alumina source, an iron source, an alkali source, water, and a seed crystal, and having a molar ratio of iron to silicon in terms of SiO2 of less than 0.1. [8] The production method according to [7] above, wherein the alkali source contains at least a sodium source or a potassium source.

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

[10] The production method according to any one of [7] to [9] above, wherein the seed crystal is 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 production method according to any one of [7] to

[10] above, wherein the content of the seed crystal in the raw material composition exceeds 0% by mass and is 10% by mass or less.

[12] The production method according to at least any one of [7] to

[11] above, which does not contain an organic structure-directing agent source.

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

[11] above, which contains 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 containing the FER-type zeolite according to any one of [1] to [6] above.

[15] A method for reducing nitrogen oxides, which includes a step of bringing a nitrogen oxide reduction catalyst containing the FER-type zeolite according to any one of [1] to [6] above into contact with a nitrogen oxide-containing gas.

Advantages of the Invention

[0011] According to the present disclosure, it is possible to provide at least any one of a FER-type zeolite in which the generation of N2O in nitrogen oxide reduction is less than that of a conventional iron-containing FER-type zeolite, and which is industrially applicable, a production method thereof, and a nitrogen oxide reduction catalyst containing the same.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0013] Hereinafter, an example of an embodiment of the present disclosure will be shown and described.

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

[0015] "Zeolite-like substance" is a compound in which T atoms have a regular structure via oxygen, and the compound contains at least an atom other than a metal and a metalloid (hereinafter also referred to as "non-metal atom") in the T atoms. Phosphorus (P) can be exemplified as the non-metal atom. As zeolite-like substances, composite phosphorus compounds containing phosphorus (P) as T atoms, such as aluminophosphate (AlPO) and silicoaluminophosphate (SAPO), can be exemplified. For the sake of clarity, in this embodiment, zeolites do not contain zeolite-like substances.

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

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

[0018] "Aluminosilicate" is a composite oxide having a structure composed of a repeating network of aluminum (Al) and silicon (Si) via oxygen (O). Among aluminosilicates, those having crystalline XRD peaks in their powder X - ray diffraction (hereinafter also referred to as "XRD") patterns are "crystalline aluminosilicates", and those having no crystalline XRD peaks are "amorphous aluminosilicates".

[0019] The XRD pattern in this embodiment is the XRD pattern obtained from XRD measurement under the following conditions. Accelerating current · voltage: 40 mA · 40 kV X - ray source: CuKα ray (λ = 1.5405 Å) Measurement mode: Step scan Scan condition: 40° / min Measurement time: 3 s Measurement range: 2θ = 3° to 43° Divergence vertical limiting slit: 10 mm Diverging / incident slit: 1° Light-receiving slit: open Light-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., UltimaIV Protectus, manufactured by Rigaku Corporation). Also, the crystalline XRD peak is a peak in which the 2θ at the peak top is specified and detected in the analysis of the XRD pattern using general analysis software, and in particular, it is an XRD peak with a full width at half maximum of 2θ = 0.50° or less. [FER-type zeolite containing iron] This embodiment is a FER-type zeolite that contains iron and has an area ratio of the peak of the spectrum with a wavelength of 300 nm or more and 600 nm or less to the peak of the spectrum with a wavelength of 190 nm or more and 600 nm or less in the UV-VIS spectrum of 20% or less.

[0021] This embodiment is a FER-type zeolite containing iron (hereinafter, also referred to as "iron-containing FER-type zeolite"), a zeolite having a crystal structure composed only of the FER structure, and further a FER-type crystalline aluminosilicate. By containing iron (Fe), it exhibits nitrogen oxide reduction characteristics. Furthermore, it can reduce nitrogen oxides while suppressing the generation of N2O compared to a FER-type zeolite containing copper.

[0022] It can be mentioned that the peak top of the XRD peak of the (200) plane in the XRD pattern of the iron-containing FER-type zeolite of this embodiment is 2θ = 9.5 ± 0.2°.

[0023] The iron-containing FER-type zeolite of the present embodiment has an area ratio of the peak of the spectrum with a wavelength of 300 nm or more and 600 nm or less to the peak with a wavelength of 190 nm or more and 600 nm or less in the UV-VIS spectrum (hereinafter, also referred to as "300 nm-600 nm spectrum intensity ratio") of 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 with a wavelength of 190 nm or more and 600 nm or less, and the iron with a higher degree of dispersion state can be confirmed as a peak with a lower wavelength. In the iron-containing FER-type zeolite of the present embodiment, iron is isolated iron (Fe 3+ ), iron clusters (Fe x O y ), and is included as one or more iron species selected from the group of iron oxide (Fe2O3) particles. In the present embodiment, a peak with a wavelength of 190 nm or more and less than 300 nm corresponds to a peak of isolated iron (Fe 3+ ), a peak with a wavelength of 300 nm or more and 400 nm or less corresponds to a peak of iron clusters (Fe x O y ), and a peak with a wavelength of more than 400 nm and 600 nm or less corresponds to a peak of iron oxide (Fe2O3) particles. When the 300 nm-600 nm spectrum intensity ratio exceeds 20%, even when isolated iron is included, the ratio of iron oxide and iron clusters in the iron contained in the FER-type zeolite increases, and only nitrogen oxide reduction characteristics comparable to those of conventional iron-containing FER-type zeolites can be obtained. The iron-containing FER-type zeolite of the present embodiment has an area ratio of the peak with a wavelength of 190 nm or more and less than 300 nm to the peak with a wavelength of 190 nm or more and 600 nm or less in the UV-VIS spectrum (hereinafter, also referred to as "190 nm-300 nm spectrum intensity ratio") of 70% or more, 80% or more, or 90% or more, and preferably 100% or less, less than 100%, or 99% or less, and may be 70% or more and 100% or less, 80% or more and less than 100%, or 90% or more and 99% or less. The iron-containing FER-type zeolite of this embodiment has an area ratio of the peak at a wavelength of 300 nm or more and 400 nm or less to the peak at 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 spectrum intensity ratio") of 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 thereof include 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. The iron-containing FER-type zeolite of this embodiment has an area ratio of the peak at a wavelength of more than 400 nm and 600 nm or less to the peak at a wavelength of 190 nm or more and 600 nm or less in the UV-VIS spectrum (hereinafter, also referred to as the "400 nm - 600 nm spectrum intensity ratio") of 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 thereof include 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. These spectrum intensity ratios [%] correspond to the abundance ratios [%] of the iron species in the iron-containing FER-type zeolite. Specifically, the 190 nm - 300 nm spectrum intensity ratio is for isolated iron (Fe 3+ ), the 300 nm - 400 nm spectrum intensity ratio is for iron clusters (Fe x O y ), and the 400 nm - 600 nm spectrum 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 an FER-type zeolite that contains iron and in which the abundance ratios of iron clusters and iron oxide particles are 20% or less, or the iron-containing FER-type zeolite of this embodiment can be regarded as an FER-type zeolite that contains iron and in which the abundance ratio of isolated iron is 80% or more. Furthermore, the total abundance ratio of isolated iron, iron clusters, and iron oxide particles in the iron-containing FER-type zeolite of this embodiment is 100%, The proportion of isolated iron is preferably 70% or more, 80% or more, or 90% or more, and is preferably 100% or less, less than 100%, or 99% or less, and is 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 preferably 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 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 moreover, The proportion of iron oxide particles is preferably 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 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 regarded as an FER-type zeolite containing iron.

[0024] The UV-VIS spectrum in this embodiment may be measured under the following conditions using a general ultraviolet-visible spectroscopic measurement device (for example, ultraviolet-visible spectrophotometer V-770, manufactured by JASCO Corporation). Integrating sphere unit: ISN-923 (manufactured by JASCO Corporation) Measurement mode: Diffuse reflection method Wavelength: 190 - 700 nm Temperature: Room Slit width: 5 nm 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 with respect to the reflectance of barium sulfate at a wavelength of 700 nm (hereinafter also referred to as "γ∞" or "relative reflectance") becomes 1, and then the corrected UV-VIS spectrum may be subjected to Kubelka-Munk (KM) transformation using the KM function (f(γ∞)) of the following formula. f(γ∞) = (1 - γ∞) 2 / 2γ∞

[0026] After the KM conversion, the UV-VIS spectrum is fitted and the waveform is separated using general analysis software (e.g., Fityk 0.9.8) and the Gaussian fitting function. Then, the peak areas are obtained for wavelengths above 190 nm and less than 300 nm, wavelengths from 300 nm to 400 nm, and wavelengths above 400 nm and less than 600 nm, respectively. Also, the sum of these can be taken as the peak area for wavelengths from 190 nm to 600 nm. The area ratio can be obtained from the ratio of the peak area of each wavelength range to the peak area for wavelengths from 190 nm to 600 nm that is obtained. Note that since the peak of the isolated iron ion may shift, after the waveform separation, the peak areas are obtained for wavelengths above 190 nm and less than 300 nm, wavelengths from 300 nm to 400 nm, and wavelengths above 400 nm and less than 600 nm, respectively. Also, the sum of these can be taken as the peak area for wavelengths from 190 nm to 600 nm. In this case, the area ratio of the peak with wavelengths above 190 nm and less than 300 nm to the peak area for wavelengths from 190 nm to 600 nm corresponds to the 190 nm - 300 nm spectrum intensity ratio, the area ratio of the peak with wavelengths from 300 nm to 400 nm to the peak area for wavelengths from 190 nm to 600 nm corresponds to the 300 nm - 400 nm spectrum intensity ratio, and the area ratio of the peak with wavelengths above 400 nm and less than 600 nm to the peak area for wavelengths from 190 nm to 600 nm corresponds to the 400 nm - 600 nm spectrum intensity ratio, respectively. In this case, the iron-containing FER-type zeolite of this embodiment is an FER-type zeolite that contains iron and has an area ratio of the peak of the spectrum with wavelengths from 300 nm to 600 nm to the peak with wavelengths from 190 nm to 600 nm in the UV-VIS spectrum of 20% or less. The area ratio of the peak of the spectrum with wavelengths from 300 nm to 600 nm to the peak with wavelengths from 190 nm to 600 nm only needs to satisfy the value of the above-mentioned 190 nm - 300 nm spectrum intensity ratio.

[0027] In order to easily exhibit practical nitrogen oxide reduction characteristics, the iron content is 0.1% by mass or more, 0.5% by mass or more, or 1.0% by mass or more, and may be 5.0% by mass or less or 3.5% by mass or less. It is preferably 0.1% by mass or more and 5.0% by mass or less, or 1.0% by mass to 5.0% by mass, or 1.0% by mass or more and 3.5% by mass or less.

[0028] The "iron content" in the present embodiment is the mass ratio [mass%] of iron (Fe) to the mass of iron-containing FER-type zeolite. Further, 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 being treated at 100 °C for 2 hours in an air atmosphere.

[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 also referred to as "isolated Fe 3+ content") is preferably 1.0% by mass or more, 1.2% by mass or more, or 1.5% by mass or more. Isolated Fe 3+ content is preferably large, but in that case, the isolated Fe 3+ content becomes the same as the upper limit value of the iron content, and for example, may be 5.0% by mass or less or 3.5% by mass or less. Preferred isolated Fe 3+ content includes 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+ content can be determined by the following formula. Isolated Fe 3+ content [mass%] = Iron content [mass%] × Proportion of isolated iron present [%] = Iron content [mass%] × 190 nm - 300 nm spectrum intensity ratio [%]

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

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

[0032] The molar ratio of silica to alumina (hereinafter also referred to as "SiO2 / Al2O3 ratio") of the iron-containing FER-type zeolite of the present embodiment may be a value that makes it difficult for crystal collapse to occur when exposed to a high-temperature and high-humidity atmosphere, and it may be 5 or more, 10 or more, or 15 or more, and may be 50 or less, 30 or less, or 20 or less, and it is preferable that it is 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 the present embodiment preferably does not substantially contain fluorine (F), and further preferably has a fluorine content of 0 mass ppm. Considering measurement errors, the fluorine content of the iron-containing FER-type zeolite of the present embodiment may be below the measurement limit, for example, 0 mass ppm or more and 100 mass ppm or less, further preferably 0 mass ppm or more and 50 mass ppm or less, and still further preferably 0 mass ppm or more and 5 mass ppm or less.

[0034] The shape of the iron-containing FER-type zeolite of the present embodiment may be any shape according to the application, and examples thereof include at least either the shape of a powder or a molded body. In the case of a powder, it may be used as a catalyst member obtained by applying or washcoating the powder onto a substrate such as a honeycomb. In the case of a molded body, it may be any initial shape according to the application, and it may be one or more selected from the group consisting of spherical, substantially spherical, elliptical, disk-shaped, columnar, polyhedral, irregular, and petal-shaped.

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

[0036] The iron-containing FER-type zeolite of the present embodiment is suitable for use as at least either a nitrogen oxide reduction catalyst or its carrier, and further as a nitrogen oxide reduction catalyst, and still further as a nitrogen oxide reduction catalyst by selective catalytic reduction.

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

[0038] The nitrogen oxide-containing gas may be any gas containing nitrogen oxides (NOx), and is preferably a gas containing at least nitrous oxide (N2O), and is a gas containing one or more selected from the group consisting of nitric oxide, nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide and nitrous oxide, and more preferably a gas containing one or more selected from the group consisting of nitric oxide, nitrogen dioxide and nitrous oxide. 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 nitrogen oxide-containing gases include exhaust gases discharged from internal combustion engines, and more specifically, exhaust 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 as long as the iron-containing FER-type zeolite of the present embodiment comes into contact with the nitrogen oxide-containing gas, and the following conditions are mentioned as the contact conditions. Space velocity: 500 to 500,000 h-1 -1 , preferably 2000 to 300,000 h-1 -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. Examples of the reducing agent include one or more selected from the group consisting of ammonia, urea, organic amines, hydrocarbons, alcohols, ketones, carbon monoxide and hydrogen, and more specifically, at least one of ammonia, hydrocarbons, urea and organic amines, and more specifically, at least one of ammonia and hydrocarbons, and more specifically, ammonia. [Method for producing iron-containing FER-type zeolite] As a preferred method for producing the iron-containing FER-type zeolite of the present embodiment, there is provided a method for producing a FER-type zeolite having a step of crystallizing a composition containing a silica-alumina source, an iron source, an alkali source and water, and in which the molar ratio of iron to silicon in terms of SiO2 is less than 0.1.

[0041] As a method for producing an iron-containing FER-type zeolite, conventionally, the FER-type zeolite.

[0042] The production method of the present embodiment has a step of crystallizing a composition (hereinafter, also referred to as "raw material composition") containing a silica-alumina source, an iron source, an alkali source, and water, and having a molar ratio of iron to silicon in terms of SiO2 of less than 0.1 (hereinafter, also referred to as "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. Specific examples of the silica-alumina source include amorphous aluminosilicate. In the present embodiment, it is considered that crystallization proceeds in a state where the dispersion of iron is promoted as compared with the case where an aluminum source and a silicon source are each contained.

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

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

[0046] Since the FER-type zeolite is likely 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, still more preferably contains a sodium source and a potassium source, and even more preferably is a sodium source and a potassium source.

[0047] Water may be regarded as the water in the raw material composition, including pure water, ion-exchanged water, as well as water contained in other starting materials such as structural water, hydrated water, and solvents.

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

[0049] Since the obtained FER-type zeolite becomes expensive, the raw material composition preferably does not contain an organic structure-directing agent (hereinafter also referred to as "SDA"), and particularly preferably 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 an SDA capable of directing the FER-type zeolite and its compound, and any amine compound capable of directing the FER-type zeolite is acceptable. In order to make the production method of the present embodiment easy to apply industrially, the SDA source is preferably an inexpensive amine compound, for example, one or more selected from the group consisting of amines other than hexamethyleneimine, and further one or more selected from the group consisting of pyridine, pyrrolidine, cyclohexylamine, and butylamine, and still further one or more selected from the group consisting of pyridine, pyrrolidine, and butylamine.

[0050] The molar ratio of iron to silicon in terms of SiO2 to aluminum in terms of Al2O3 in the raw material composition (hereinafter also referred to as "SiO2 / Al2O3") is 5 or more, 10 or more, or 15 or more, and may be 50 or less, 30 or less, 25 or less, or 18 or less, and preferably is 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 in terms of SiO2 in the raw material composition (hereinafter also referred to as "Fe / SiO2") is less than 0.1, preferably 0.05 or less, or 0.03 or less. When Fe / SiO2 exceeds 0.1, iron aggregates and is incorporated into the FER-type zeolite in a less active state. 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, preferably 0.38 or less, or 0.30 or less, and is preferably 0.05 or more, 0.20 or more, or 0.25 or more. Preferred M / SiO2 values include 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 in terms of SiO2 in the raw material composition (hereinafter also referred to as "K / SiO2") is less than 0.40, preferably 0.30 or less, or 0.15 or less, and may be 0 or more, more than 0, or 0.1 or more, and is preferably more than 0 and 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 iron-containing FER-type zeolite in a more dispersed state of iron is more likely to crystallize, the molar ratio of water (H2O) to silicon in terms of SiO2 in the raw material composition (hereinafter also referred to as "H2O / SiO2") may be 50 or less, preferably 40 or less, or 25 or less. H2O / SiO2 may be 5 or more, 10 or more, or 13 or more, and is preferably 5 or more and 40 or less, 10 or more and 40 or less, or 13 or more and 25 or less.

[0055] Preferred compositions of the raw material composition include the following molar compositions. In the following molar compositions, M is an alkali metal. For example, when the alkali metals are sodium and potassium, 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 = more than 0, 0.001 or more, 0.01 or more, or 0.02 or more, 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] Even more preferred compositions of the raw material composition include the following molar compositions. SiO2 / Al2O3 = 5 or more and 50 or less Fe / SiO2 = more than 0 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 or more and 50 or less Particularly preferred compositions of the raw material composition include the following molar compositions. SiO2 / Al2O3 = 10 or more and 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 or more and 25 or less

[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] Since crystallization proceeds more uniformly, it is preferable to perform crystallization while the raw material composition is being stirred. Stirring may be performed directly on the raw material composition, or the container containing the raw material composition may be stirred.

[0063] The crystallized product (iron-containing FER-type zeolite) of crystallization may be recovered by any method, and examples include solid-liquid separation, washing, and drying, and then recovering it.

[0064] Solid-liquid separation may be any method that can separate the raw material composition after crystallization into a solid component (crystallized product) and a liquid phase. Examples include one or more selected from the group consisting of filtration, decantation, and centrifugation.

[0065] Washing may be any method that can remove impurities contained in the recovered crystallized product. For example, pure water washing may be used.

[0066] Drying may be any method that can remove the moisture physically adsorbed on the crystallized product. Examples include at least either static drying or spray drying, and drying may be performed in an air atmosphere at 100°C or higher and 120°C or lower.

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

[0068] The firing time may be appropriately set according to the crystallized product to be fired and the firing method. For example, it may be 1 hour or more and 10 hours or less, 2 hours or more and 8 hours or less, or 3 hours or more and 5 hours or less.

[0069] The production method of the present embodiment may have a step of ion-exchanging an iron-containing FER-type zeolite (hereinafter, also referred to as the "ion-exchange step") in order to reduce the alkali metal content of the iron-containing FER-type zeolite. The ion exchange may be any method as long as the alkali metal content is reduced. For example, the iron-containing FER-type zeolite may be mixed with an aqueous ammonium chloride solution for ion exchange.

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

[0071] In addition to, or instead of, the ion-exchange step, the production method of the present embodiment may have a step of mixing an iron-containing FER-type zeolite and a metal compound (hereinafter, also referred to as the "metal-supporting step"). Thereby, any metal element according to the purpose can be supported on the iron-containing FER-type zeolite.

[0072] The mixing method may be any method as long as the metal compound can be supported on the iron-containing FER-type zeolite, and examples thereof include one or more selected from the group consisting of an ion-exchange method, an impregnation-support method, an evaporation-to-dryness method, a precipitation-support method, and a physical mixing method.

Examples

[0073] Hereinafter, the present disclosure will be described with reference to examples. However, the present disclosure is not limited thereto. Hereinafter, the evaluation method will be described. (Identification of crystals) Using a powder X-ray diffractometer (device name: UltimaIV, manufactured by Rigaku Corporation), XRD measurement of the sample was performed. The measurement conditions are as follows. X-ray source: CuKα ray (λ = 1.5405 Å) Measurement mode: Step scan Scan condition: 40° / min Measurement time: 3 seconds Measurement range: 2θ = 5° to 43°

[0074] (Composition analysis) The sample was dissolved in a mixed aqueous solution of hydrofluoric acid and nitric acid to prepare a sample solution. 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 dispersibility) The UV-Vis spectrum of the sample was measured using an ultraviolet-visible spectrophotometer (device name: ultraviolet-visible spectrophotometer V-770, manufactured by JASCO Corporation). The measurement conditions are as follows. Integrating sphere unit: ISN-923 (manufactured by JASCO Corporation) Measurement mode: diffuse reflection method Wavelength: 190 - 700 nm Temperature: room temperature Slit width: 5 nm Background: barium sulfate From the obtained UV-Vis spectrum, the spectral intensity ratios [%] of 300 nm - 600 nm, the spectral intensity ratio (proportion of isolated iron (Fe 3+ )) [%] of 190 nm - 300 nm, the spectral intensity ratio (proportion of cluster iron (Fe x O y )) [%] of 300 nm - 400 nm, and the spectral intensity ratio (proportion of iron oxide particles (Fe2O3)) [%] of 400 nm - 600 nm were determined. Also, from the proportion of isolated iron and the iron content determined by the above composition analysis, the content of isolated Fe 3+ was determined by the following formula. Content of isolated Fe 3+ [Mass%] = Iron content [mass%] × Proportion of isolated iron (Fe 3+ )) [%] = Iron content [mass%] × Spectral intensity ratio [%] of 190 nm - 300 nm

[0075] Example 1 A 48 mass% sodium hydroxide aqueous solution, a 48 mass% potassium hydroxide aqueous solution, 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 FER-type zeolite (SiO2 / Al2O3 = 18.0) was mixed with the obtained raw material composition so that the seed crystal content was 2.0 mass%. The mixed raw material composition was filled into a sealed container with a volume of 80 mL, and while rotating this at 55 rpm, it was hydrothermally treated at 180 °C for 40 hours to obtain a crystallized product. The obtained crystallized product was subjected to solid-liquid separation, washed with pure water, and then dried at 110 °C in the air and recovered. The crystallized product was a zeolite composed of a single phase of FER-type zeolite, and SiO2 / Al2O3 was 18.0.

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

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

[0079] Example 2 An 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 composed of a single phase of FER-type zeolite, with SiO2 / Al2O3 being 18.2, the alkali metal content being less than 0.1% by mass, and the Fe content being 2.0% by mass. Also, 2θ at the peak top of the XRD peak of the (200) plane was 9.3.

[0081] Example 3 An 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 is a zeolite composed of a single phase of FER-type zeolite, with SiO2 / Al2O3 being 18.4, the alkali metal content being less than 0.1% by mass, and the Fe content being 3.0% by mass. Also, the 190nm - 300nm spectrum intensity ratio (the proportion of isolated iron) was 99.7%, the 300nm - 400nm spectrum intensity ratio (the proportion of cluster iron) was 0.3%, the 400nm - 600nm spectrum intensity ratio (the proportion of iron oxide particles) was 0%, the 300nm - 600nm spectrum intensity ratio was 0.3%, and the content of isolated Fe 3+ content was 3.0% by mass. Also, 2θ at 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 set 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 is a zeolite composed of a single phase of FER-type zeolite, and SiO2 / Al2O3 was 18.7.

[0085] The obtained crystallized product was calcined in the air at 600°C for 2 hours. The calcined solid was exchanged with a 20% by mass aqueous ammonium chloride solution (weight of aqueous ammonium chloride solution: weight of zeolite = 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 uniformly mixed sample was dried in the air at 110°C for 5 hours 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-type zeolite of this comparative example is a zeolite composed of a single phase of FER-type zeolite, with SiO2 / Al2O3 being 18.7, the alkali metal content being less than 0.1% by mass, and the Fe content being 3.0% by mass. Also, the 190nm - 300nm spectrum intensity ratio (proportion of isolated iron) was 29.6%, the 300nm - 400nm spectrum intensity ratio (proportion of cluster iron) was 23.2%, the 400nm - 600nm spectrum intensity ratio (proportion of iron oxide particles) was 47.2%, and the 300nm - 600nm spectrum intensity ratio was 70.4%. The content of isolated Fe 3+ was 0.9% by mass.

[0087] The iron-containing FER-type zeolite of this comparative example has an iron content comparable to that of the iron-containing FER-type zeolite of Example 3, but the proportion of isolated iron is low, and the content of isolated Fe is lower than that of the iron-containing FER-type zeolite of Example 1. 3+ It was confirmed that the content was low.

[0088]

Table 1

[0089] It was confirmed by this example that an iron-containing FER-type zeolite containing iron in a dispersed state, that is, an iron-containing FER-type zeolite with a low 300nm - 600nm spectrum intensity ratio, can be obtained without the need for an expensive SDA.

[0090] Measurement Example <Hydrothermal Durability Treatment> The iron-containing FRR-type zeolites obtained in the examples and comparative examples were each molded and pulverized to form agglomerated particles with an agglomeration diameter of 12 - 20 mesh. After filling 3 mL of the obtained agglomerated particles into an atmospheric pressure fixed bed flow-through reaction tube, a hydrothermal durability treatment was carried out by flowing air containing 20% by volume of water under the following conditions. Flow rate of air: 300 mL / min Treatment temperature: 700 °C Treatment time: 20 hours

[0091] <Nitrogen oxide reduction treatment> 1.5 mL of the aggregated particle sample was filled into an atmospheric pressure fixed-bed flow-through reaction tube, held at the following measurement temperatures, and a nitrogen oxide-containing gas was passed through. The nitrogen oxide concentrations at the inlet and outlet of the atmospheric pressure fixed-bed flow-through reaction tube were measured. The flow conditions of the nitrogen oxide-containing gas are as follows.

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

[0093] The nitrogen oxide reduction rate was determined from the obtained nitrogen oxide concentrations using the following formula. Nitrogen oxide reduction rate (%) ={([NOx]in - [NOx]out) / [NOx]in}×100 [NOx]in is the nitrogen oxide concentration of the nitrogen oxide-containing gas at the inlet of the atmospheric pressure fixed-bed flow-through reaction tube, and [NOx]out is the nitrogen oxide concentration of the nitrogen oxide-containing gas at the outlet of the atmospheric pressure fixed-bed flow-through reaction tube.

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

[0095] The evaluation results of the N2O production amount of the iron-containing FER-type zeolite before the hydrothermal durability treatment in the nitrogen oxide reduction treatment at 150 °C to 300 °C are shown in Table 2 below, and the evaluation results of the N2O production amount of the iron-containing FER-type zeolite after the hydrothermal durability treatment in the nitrogen oxide reduction treatment at 150 °C to 300 °C are shown in Table 3.

[0096]

Table 2

[0097] It was confirmed that 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, the production of N2O was suppressed in the iron-containing FER-type zeolite of the example. In particular, both the iron-containing FER-type zeolite of Example 3 and the iron-containing FER-type zeolite of Comparative Example 1 have an iron content of 3% by mass. However, compared with the iron-containing FER-type zeolite of Comparative Example 1 obtained by the post-impregnation method, it was confirmed that in the iron-containing FER-type zeolite of Example 3, the production of N2O was significantly suppressed 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.

[0098]

Table 3

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

[0100] Next, Table 4 shows the evaluation results of the amount of N2O produced in the iron-containing FER-type zeolite before the hydrothermal durability treatment in the nitrogen oxide reduction treatment in the high temperature range, and Table 5 shows the evaluation results of the amount of N2O produced in the iron-containing FER-type zeolite after the hydrothermal durability treatment in the nitrogen oxide reduction treatment in the high temperature range.

[0101]

Table 4

[0102] In the nitrogen oxide reduction treatment in the high temperature range of 500°C or higher, it was confirmed that in the iron-containing FER-type zeolite of Example 1, substantially no N2O was produced, although not only the iron as the active ingredient but also the iron clusters serving as active species in the high temperature range were few.

[0103]

Table 5

[0104] Compared with the iron-containing zeolite of Comparative Example 1, it was confirmed that the iron-containing FER-type zeolite of Example 3 suppressed the generation of N2O in the nitrogen oxide reduction treatment in the high-temperature range of 500 °C or higher even after the 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 the iron-containing FER-type zeolite of the Example showed stable nitrogen oxide reduction characteristics in a wide temperature range of nitrogen oxide reduction treatment from low temperature to high temperature with respect to the iron-containing FER-type zeolite of Comparative Example 1.

[0108] Also, in the nitrogen oxide reduction treatment at 550 °C, the nitrogen oxide reduction rate after the hydrothermal durability treatment was 75% for the iron-containing FER-type zeolite of Comparative Example 1, while for Examples 1 to 3, they were 77%, 73% and 81%, respectively. From this, although the iron-containing FER-type zeolite of the present Example substantially does not contain an iron cluster which is an active species in the high-temperature range, it was confirmed that it shows a nitrogen oxide reduction rate after the hydrothermal durability treatment in the nitrogen oxide reduction treatment in the high-temperature range equal to or higher than that of the conventional iron-containing FER-type zeolite containing this.

Claims

1. A FER-type zeolite containing iron, silicon, and aluminum, having an iron content of 1.0 mass% or more and 5 mass% or less, a molar ratio of silica to alumina of 5 or more and 50 or less, and an 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 of 5% or less.

2. 2. The FER type zeolite according to claim 1, wherein the content of isolated iron in the iron content is 1.0 mass% or more and 5.0 mass% 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. 3. The FER type zeolite according to claim 1 or 2, wherein the area ratio of a peak having a wavelength of 300 nm or more and 400 nm or less to a peak having a wavelength of 190 nm or more and 600 nm or less in a UV-VIS spectrum is 0% or more and 5.0% or less.

5. The FER type zeolite according to 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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