JP7501763B2 - Zeolite and its manufacturing method - Google Patents

Description

This disclosure relates to a zeolite with a new structure and a method for producing the same.

Small-pore zeolites, which have pores formed from eight-membered oxygen rings, are used as catalysts for the production of olefins and the selective reduction of nitrogen oxides (SCR). Because the activity and durability of catalytic reactions vary depending on the crystal structure of the zeolite, there is a demand for zeolites with new structures.

One new structure that has been reported is a small-pore zeolite whose crystal structure consists of intergrowths.

For example, Patent Document 1 reports a zeolite consisting of an intergrowth of ERI and LEV structures, and discloses that this intergrowth catalyzes an olefin production reaction.

For example, Patent Document 2 discloses that a zeolite consisting of an intergrowth of an ERI structure and an OFF structure catalyzes the SCR reaction.

Special Publication No. 2018-531869 WO2012/007914

The present disclosure aims to provide at least one of the following: a zeolite consisting of intergrowths with a new structure; a zeolite consisting of intergrowths that contains a metal and has high heat resistance and nitrogen oxide reduction ability when used as a catalyst for the SCR reaction; and a method for producing such a zeolite.

The inventors have investigated zeolites made of intergrowths. They have found that zeolites made of intergrowths with a structure different from conventional structures have high heat resistance and nitrogen oxide reduction ability.

In other words, the gist of the present disclosure is as follows.
[1] A zeolite characterized by having the powder X-ray diffraction peaks shown in the table below.

[2] The zeolite according to the above [1], wherein the crystal structure is an intergrowth of an LEV structure, an ERI structure and an OFF structure.
[3] The zeolite according to the above [1] or [2], having an ERI/OFF ratio of <1.
[4] The zeolite according to any one of [1] to [3] above, wherein the molar ratio of silica to alumina is 5 or more and 50 or less.
[5] The zeolite according to any one of the above [1] to [4], which contains at least one of copper and iron.
[6] A method for producing a zeolite according to any one of the above [1] to [5], comprising a crystallization step of crystallizing a composition containing a tetraethylammonium cation source, an N,N-dimethylpiperidinium cation source, a silica source, an alumina source, a potassium cation source, and water. [7] A method for producing a zeolite according to the above [6], wherein the composition is a composition obtained by mixing a mixture obtained by mixing a tetraethylammonium cation source, a silica source, an alumina source, and water and heating the mixture at 80° C. or higher and lower than 100° C., and mixing the mixture obtained by mixing an N,N-dimethylpiperidinium cation source, a potassium cation source, and water.
[8] A catalyst comprising the zeolite according to any one of [1] to [5] above.
[9] A method for reducing nitrogen oxides, comprising using the zeolite according to any one of [1] to [5] above.

The present disclosure makes it possible to provide at least one of the following: a zeolite consisting of intergrowths with a novel structure; an intergrowth zeolite containing a metal that has high heat resistance and nitrogen oxide reduction ability when used as a catalyst for the SCR reaction; and a method for producing such an intergrowth zeolite.

DIFFaX patterns of an intergrowth having an LEV structure, an OFF structure, and an ERI structure. DIFFaX pattern of an intergrowth having an LEV structure and an OFF structure. DIFFaX pattern of an intergrowth having an LEV structure and an ERI structure. 1 is a graph showing the correlation between the LEV ratio and the peak position. 1 is a scanning electron microscope photograph of Example 1.

The zeolite disclosed herein is described below.

The zeolite of the present disclosure is a zeolite having the powder X-ray diffraction (hereinafter also referred to as "XRD") peaks shown in the table below. Zeolites having such XRD peaks have a crystal structure consisting of intergrowths. By incorporating a metal into this, it is possible to provide a zeolite that has high heat resistance and nitrogen oxide reduction ability when used as a catalyst for the SCR reaction.

In addition to these XRD peaks, the zeolite of the present disclosure may have a peak whose relative intensity is less than 10% of the intensity of the XRD peak at 2θ=23.6±0.2° (hereinafter also referred to as the "reference peak"). Note that in this specification, the 2θ angle is the value when CuKα radiation is used as the radiation source.

Furthermore, the zeolite of the present disclosure may have one or more of the XRD peaks shown in the table below.

The zeolite disclosed herein preferably has a full width at half maximum (hereinafter also referred to as "FWHM") within the range shown in the table below.

The zeolite of this disclosure is a crystalline aluminosilicate. Crystalline aluminosilicate has a crystal structure consisting of a repeating network of aluminum (Al) and silicon (Si) via oxygen (O).

The zeolite disclosed herein is a zeolite consisting of intergrowth, for example, a zeolite consisting of intergrowth having an LEV structure, an ERI structure, and an OFF structure.

In this disclosure, the structure of a zeolite is each structure represented by the IUPAC structure code (hereinafter also simply referred to as "structure code") defined by the Structure Commission of the International Zolite Association, and the LEV structure, ERI structure, and OFF structure are structures that are LEV type, ERI type, and OFF type, respectively, in the structure code.

The LEV structure, ERI structure, and OFF structure are each crystal structures having a three-dimensional periodic structure. On the other hand, an intergrowth is a crystal structure having at least stacking irregularities, and is a crystal structure in which two or more periodic structures having three-dimensional regularity are stacked in a two-dimensional or one-dimensional regular period. For example, an intergrowth having an LEV structure, an ERI structure, and an OFF structure (hereinafter also referred to as a "LEV-ERI-OFF intergrowth", and each structure (LEV structure, ERI structure, OFF structure, etc.) contained in the intergrowth is also referred to as a "LEV-ERI intergrowth", etc.) is a crystal structure having a periodic structure having three-dimensional regularity of either the LEV structure, the ERI structure, or the OFF structure in the a-axis direction and the b-axis direction, and further having a LEV structure, the ERI structure, and the OFF structure stacked in a regular period in the c-axis direction, and is a crystal structure having stacking irregularities of the LEV structure, the ERI structure, and the OFF structure.

Zeolites consisting of intergrowths can be identified by comparing their XRD pattern with the XRD pattern obtained by simulation using DIFFaX (hereinafter also referred to as the "DIFFaX pattern") or by observation with a transmission electron microscope.

The DiFFaX pattern is obtained by calculation using the structure data (cif file) posted on the website of the International Zeolite Society. The TRANSITON parameters of each structure used in the calculation may be as follows. In the case of an intergrowth having an LEV structure, an ERI structure, and an OFF structure,
TRANSITION parameters from LEV type to LEV type...a
TRANSITION parameters from LEV type to ERI type...b
TRANSITION parameters from LEV type to OFF type...c
TRANSITION parameters from ERI type to LEV type...d
TRANSITION parameters from ERI type to ERI type...e
TRANSITION parameter from ERI type to OFF type...f
TRANSITION parameters from OFF type to LEV type...g
TRANSITION parameters from OFF type to ERI type...h
TRANSITION parameters from OFF type to OFF type...i
Then, a=d=g, b=e=h, c=f=i, a+b+c=1, d+e+f=1, and g+h+i=1.

Figure 1 shows the DIFFaX pattern of an intergrowth having an LEV structure, an ERI structure, and an OFF structure, with the volume ratio of the OFF structure and the ERI structure being equal. Figure 2 shows the DIFFaX pattern of an intergrowth having an LEV structure and an OFF structure. Figure 3 shows the DIFFaX pattern of an intergrowth having an LEV structure and an ERI structure. In each figure, notations such as 100:0 indicate the volume ratio of each structure.

As shown in Figures 1 to 3, the XRD pattern of a zeolite consisting of intergrowth is different from the XRD pattern of a mixture in which two or more zeolites consisting of different crystal structures are physically mixed. For example, the XRD pattern of a mixture in which a zeolite having an LEV structure and a zeolite having an ERI structure are physically mixed is an XRD pattern in which the XRD peaks of both structures are simply added together. In contrast, as shown in Figure 3, the XRD pattern of a zeolite consisting of intergrowth having an LEV structure and an ERI structure is not an XRD pattern in which the XRD peaks of both structures are simply added together, but an XRD pattern having XRD peaks derived from the intergrowth. Examples of XRD peaks derived from the intergrowth include XRD peaks in which some of the XRD peaks derived from each structure are broadened, and XRD peaks in which the XRD peaks derived from each structure are peak-shifted. A specific example of an XRD peak derived from an intergrowth containing an LEV structure is an XRD peak corresponding to the (012) plane of the LEV structure, which is shifted to a lower angle and broadened.

The zeolite of the present disclosure has an XRD peak at 2θ=25.2±0.2°. This XRD peak is a peak derived from the LEV structure, and indicates that the zeolite has a periodic structure with the three-dimensional regularity of the LEV structure. This gives the zeolite of the present disclosure high heat resistance. The ratio of the intensity of the peak at 2θ=25.2±0.2° to the intensity of the reference peak is 10 or more and 50 or less, and preferably 20 or more and 40 or less.

The zeolite of the present disclosure preferably has an XRD peak at 2θ=9.7±0.2°. This XRD peak is a peak derived from the ERI structure, and indicates that the zeolite has a periodic structure with the three-dimensional regularity of the ERI structure. This makes the zeolite of the present disclosure more likely to have excellent heat resistance. The ratio of the intensity of the peak at 2θ=9.7±0.2° to the intensity of the reference peak is preferably 10 or more and 50 or less, and more preferably 20 or more and 40 or less.

The volume ratio of the LEV structure to the total of the LEV structure, ERI structure, and OFF structure in the crystal structure of the zeolite disclosed herein (hereinafter also referred to as the "LEV ratio") is preferably 50% or more and 80% or less, and more preferably 60% or more and 80% or less.

The LEV ratio in the zeolite of the present disclosure can be determined by comparing the intensity ratio (A/B) of the XRD peak intensity (A) to the XRD peak intensity (B) of the XRD pattern of the zeolite and the DIFFaX pattern of an intergrowth having an LEV structure, an ERI structure, and an OFF structure.

XRD peak intensity (A):
Intensity of the XRD peak having the strongest peak intensity in the range of 2θ = 20.75 ± 0.7 ° XRD peak intensity (B):
Intensity of the XRD peak having the strongest peak intensity in the range of 2θ=22.25±0.7°. Here, XRD peak intensity (A) corresponds to the maximum value of the XRD peak intensity of the peak group corresponding to the (211) and (015) planes of the LEV structure, the (210) plane of the OFF structure, and the (120) and (210) planes of the ERI structure, and XRD peak intensity (B) corresponds to the maximum value of the XRD peak intensity of the peak group corresponding to the (122) plane of the LEV structure, and the (211) and (121) planes of the ERI structure.

In the zeolite of the present disclosure, the volume ratio of the ERI structure to the OFF structure in the crystal structure (hereinafter also referred to as the "ERI/OFF ratio") is preferably less than 1 (ERI/OFF ratio < 1). When the ERI/OFF ratio is < 1, there is a tendency for the zeolite to exhibit higher heat resistance.

There is no particular lower limit for the ERI/OFF ratio, but it can be, for example, 0 or more (0≦ERI/OFF ratio), and preferably exceeds 0 (0<ERI/OFF ratio).

The ERI/OFF ratio can be derived by comparing 2θ of the XRD peak corresponding to the (012) plane of the LEV structure and the (101) plane of the ERI structure in the DIFFaX pattern (hereinafter also referred to as the "LEV ₍₀₁₂₎ -ERI ₍₁₀₁₎ peak") with 2θ of the LEV ₍₀₁₂₎ -ERI ₍₁₀₁₎ peak of the zeolite of the present disclosure.

That is, the LEV ₍₀₁₂₎ -ERI ₍₁₀₁₎ peak is an XRD peak having a peak top at 2θ=11±0.4°, and in the LEV-ERI-OFF intergrowth, the 2θ changes depending on the ERI/OFF ratio. Therefore, by determining the 2θ values of the LEV (012) -ERI (101) peak in the DIFFaX patterns of the LEV-ERI-OFF intergrowth (volume ratio LEV:ERI:OFF=1:1:1), the LEV-ERI intergrowth (volume ratio LEV:ERI:OFF=1:1:0), and the LEV-OFF intergrowth (volume ratio LEV:ERI:OFF=1:0:1), which correspond to the same LEV ratio as the zeolite of the present disclosure, a linear approximation line showing the change in 2θ of the LEV _{(012) -ERI (101) peak} due to the change in the volume ratio (ERI ratio) of the ERI structure relative to the total of the LEV structure, ERI structure, and OFF structure can be obtained. The ERI/OFF ratio can be derived by comparing the obtained linear approximation line with 2θ of the LEV ₍₀₁₂₎ -ERI ₍₁₀₁₎ peak in the XRD pattern of the zeolite of the present disclosure.

The molar ratio of silica to alumina in the zeolite of the present disclosure ( _hereinafter also referred to as " _SiO2 / _Al2O3 ratio") is preferably 5 or more, more preferably 10 or more. If the _SiO2 / _Al2O3 ratio is 5 or more, the _zeolite has higher heat resistance when used at high temperatures. If the _SiO2 / _Al2O3 ratio is 50 or less, more preferably 20 or less, _the zeolite has a more sufficient amount of acid sites as a catalyst.

A preferable range of the SiO ₂ /Al ₂ O ₃ ratio is 5 or more and 50 or less, and further 10 or more and 20 or less.

The specific surface area of the zeolite of the present disclosure is 300 ^m2 /g or more and 800 ^m2 /g or less, and further ⁴⁰⁰ m2/g or more and 600 ^m2 /g or less. When the specific surface area is in this range, the zeolite of the present disclosure can exhibit more sufficient performance not only as a nitrogen oxide reduction catalyst, but also as various catalysts and even as an adsorbent.

The zeolite of the present disclosure preferably contains a metal, and more preferably is modified with a metal. By containing a metal, the zeolite can exhibit practical nitrogen oxide reduction properties when used as a nitrogen oxide reduction catalyst. The metal contained is preferably at least one of copper and iron, and more preferably copper.

When the zeolite of the present disclosure contains at least one of copper and iron (hereinafter also referred to as "copper, etc."), the mass ratio of copper, etc. to the mass of the zeolite is 0.1 mass% or more and 10 mass% or less, and further 1 mass% or more and 5 mass% or less. In calculating the mass ratio of copper to the mass of the zeolite, the weight of copper is calculated as metallic copper.

Next, we will explain the manufacturing method of the zeolite disclosed herein.

The zeolite of the present disclosure can be obtained by a production method including a crystallization step of crystallizing a composition containing a tetraethylammonium cation (hereinafter also referred to as "TEA ⁺ ") source, an N,N-dimethylpiperidinium cation (hereinafter also referred to as "DMPy ⁺ ") source, a silica source, an alumina source, a potassium cation source, and water (hereinafter also referred to as the "raw material composition").

The TEA ⁺ source may be any salt containing TEA ⁺ . The TEA ⁺ source is preferably at least one selected from the group consisting of tetraethylammonium chloride, tetraethylammonium bromide, and tetraethylammonium hydroxide (hereinafter also referred to as "TEAOH"), and more preferably TEAOH.

The DMPy ⁺ source may be any salt containing DMPy ⁺ . The DMPy ⁺ source is preferably at least one selected from the group consisting of N,N-dimethylpiperidinium chloride (hereinafter also referred to as "DMPyCl"), N,N-dimethylpiperidinium bromide, and N,N-dimethylpiperidinium hydroxide, and is more preferably DMPyCl.

The silica source is a compound containing silicon, and is preferably at least one of the group consisting of silica sol, fumed silica, colloidal silica, precipitated silica, amorphous silicic acid, crystalline aluminosilicate, and amorphous aluminosilicate, more preferably at least one of crystalline aluminosilicate and amorphous aluminosilicate, and even more preferably crystalline aluminosilicate.

The alumina source is a compound containing aluminum, and is preferably at least one selected from the group consisting of aluminum hydroxide, aluminum oxide, aluminum sulfate, aluminum chloride, aluminum nitrate, crystalline aluminosilicate, amorphous aluminosilicate, metallic aluminum, and aluminum alkoxide, more preferably at least one of crystalline aluminosilicate and amorphous aluminosilicate, and even more preferably crystalline aluminosilicate.

The silica source and the alumina source are preferably at least one of a crystalline aluminosilicate and an amorphous aluminosilicate, more preferably a crystalline aluminosilicate, and even more preferably an FAU-type zeolite (crystalline aluminosilicate).

The potassium cation source may be a salt containing a potassium cation. Examples of the potassium cation source include at least one of the group consisting of potassium fluoride, potassium chloride, potassium bromide, potassium iodide, and potassium hydroxide, and potassium hydroxide is preferred.

The raw material composition may contain a salt (hereinafter also referred to as an "alkali source") containing at least one of the group consisting of lithium cations, sodium cations, rubidium cations, and cesium cations.

The alkali source is preferably at least one of the group consisting of fluorides, chlorides, bromides, iodides, and hydroxides containing at least one of the group consisting of lithium cations, sodium cations, rubidium cations, and cesium cations, and more preferably hydroxides. Particularly preferred alkali sources include at least one of the group consisting of fluorides, chlorides, bromides, iodides, and hydroxides containing sodium cations, and further sodium hydroxide.

The water may be, for example, pure water. Each of the raw materials of the raw material composition (except water) may also be used as an aqueous solution.

The raw material composition may be any composition obtained by mixing the respective raw materials by any method, but is preferably a composition obtained by mixing a mixture (hereinafter also referred to as a "precursor mixture") obtained by mixing a TEA ⁺ source, a silica source, an alumina source, and water and heating the mixture at 80° C. or more and less than 100° C., preferably 85° C. or more and less than 95° C., with a DMPy ⁺ source, a potassium cation source, and water.

The precursor mixture and the raw material composition will be specifically described below.
(Precursor Mixture)
The precursor mixture is obtained by heating a mixture containing a TEA ⁺ source, a silica source, an alumina source, and water, and the mixture may optionally contain at least one of the group consisting of a DMPy ⁺ source, a potassium cation source, and an alkali source in addition to the TEA ⁺ source, the silica source, the alumina source, and water.

The precursor mixture can have the following molar composition:

The SiO ₂ /Al ₂ O ₃ ratio is preferably 10 or more, and more preferably 15 or more. On the other hand, the SiO ₂ /Al ₂ O ₃ ratio is preferably 50 or less, and more preferably 30 or less. A preferable SiO ₂ /Al ₂ O ₃ ratio is 10 or more and 30 or less.

The molar ratio of TEA ⁺ to silica (hereinafter also referred to as "TEA ⁺ /SiO ₂ ratio") is preferably 0.1 or more, more preferably 0.2 or more. On the other hand, the TEA ⁺ /SiO ₂ ratio is preferably 1.0 or less, more preferably 0.5 or less.

The molar ratio of hydroxide ions to silica (hereinafter also referred to as "OH/ _SiO2 ratio") is preferably 1.0 or less, more preferably 0.6 or less. On the other hand, when hydroxide ions are contained, the OH/ _SiO2 ratio is preferably 0.2 or more, more preferably 0.4 or more.

Zeolite crystallizes more efficiently if the molar ratio of water (H ₂ O) to silica (hereinafter also referred to as "H ₂ O/SiO ₂ ratio") is 100 or less, and furthermore 50 or less. From the viewpoint of appropriate fluidity, the H ₂ O/SiO ₂ ratio is preferably 3.0 or more, and furthermore 5.0 or more.

The molar ratio of DMPy ⁺ to silica (hereinafter also referred to as “DMPy ⁺ / _SiO2 ratio”) is preferably 0.

The molar ratio of potassium cations to silica (hereinafter also referred to as the "K/ _SiO2 ratio") is preferably 0 or more and 0.02 or less, and more preferably 0 or more and 0.01 or less.

The molar ratio of alkali cations to silica (hereinafter also referred to as the "M/ _SiO2 ratio", and when the alkali cation is a sodium cation or the like, also referred to as the "Na/ _SiO2 ratio", etc.) is preferably 0 or more and 0.02 or less, and more preferably 0 or more and 0.01 or less.

The following are preferred ranges for the molar ratios of the components in the precursor mixture:

10≦SiO ₂ /Al ₂ O ₃ ratio≦30
0.1≦TEA ⁺ /SiO ₂ ratio≦0.5
DMPy ⁺ /SiO ₂ ratio = 0
0≦K/ _SiO2 ratio≦0.02
0≦Na/ _SiO2 ratio≦0.02
0.2≦OH/ _SiO2 ratio≦1
3≦ _H2O / _SiO2 ratio≦50
(Raw material composition)
The raw material composition is preferably a mixture of a precursor mixture, a DMPy ⁺ source, a potassium cation source, and water.

The preferred _SiO2 / _{Al2O3 and} TEA ⁺ / _SiO2 ratios are in the same ranges as the precursor mixture.

The DMPy ⁺ /SiO ₂ ratio is preferably 0.1 or more, and more preferably 0.2 or more. On the other hand, the DMPy ⁺ /SiO ₂ ratio is preferably 1.0 or less, and more preferably 0.6 or less.

The K/ _SiO2 ratio is preferably 0.01 or more, more preferably 0.02 or more, and more preferably _0.2 or less, more preferably 0.1 or less.

The Na/ _SiO2 ratio is preferably 0.05 or more. The Na/ _SiO2 ratio is preferably 0.5 or less, and more preferably 0.3 or less.

The OH/ _SiO2 ratio is preferably 1.0 or less, more preferably 0.6 or less. When the OH/ _SiO2 ratio is 1.0 or less, the yield of zeolite tends to be high. On the other hand, when the raw material composition contains hydroxide ions, the OH/ _SiO2 ratio is preferably 0.2 or more, more preferably 0.4 or more.

Zeolite crystallizes more efficiently when the H ₂ O/SiO ₂ ratio is 100 or less, and furthermore 50 or less. In order to obtain a raw material composition having appropriate fluidity, the H ₂ O/SiO ₂ ratio is preferably 3.0 or more, and furthermore 5.0 or more.

The following are preferred ranges for the molar ratios of the raw material composition:

10≦SiO ₂ /Al ₂ O ₃ ratio≦30
0.1≦TEA ⁺ /SiO ₂ ratio≦0.5
0.1≦DMPy ⁺ / _SiO2 ratio≦1.0
0.01≦K/ _SiO2 ratio≦0.1
0≦Na/ _SiO2 ratio≦0.5
0.2≦OH/ _SiO2 ratio≦1
3≦ _H2O / _SiO2 ratio≦50
In the manufacturing method of the present disclosure, zeolite is obtained through a crystallization step. In the crystallization step, the raw material composition is crystallized by hydrothermal synthesis. As a method of crystallization, for example, the raw material composition is filled in a sealed container and heated.

In the crystallization process, seed crystals may be mixed into the raw material composition. By mixing seed crystals, zeolite nucleation is promoted, allowing crystallization to occur in a shorter time.

From the viewpoint of promoting crystallization, the crystallization temperature may be 100°C or higher. Since the higher the crystallization temperature, the more the crystallization is promoted, the crystallization temperature is preferably 130°C or higher, and more preferably 140°C or higher. On the other hand, if the raw material composition crystallizes, there is no need to increase the crystallization temperature more than necessary. Therefore, the crystallization temperature is preferably 200°C or lower, and more preferably 170°C or lower. Furthermore, crystallization can be carried out with the raw material composition either in a stirred state or in a stationary state.

The crystallization time in the crystallization step is preferably 12 hours or more and less than 100 hours, and more preferably 15 hours or more and less than 80 hours.

When the zeolite of the present disclosure is used as a catalyst or adsorbent, the manufacturing method of the present disclosure may include a washing process, a drying process, a calcination process, an ion exchange process, a metal-containing process, etc.

In the washing step, the zeolite and the liquid phase are separated into solid and liquid, and impurities are removed. A known method can be used for the solid-liquid separation. After the solid-liquid separation, the zeolite obtained as the solid phase can be washed with pure water.

The drying process removes moisture such as water adsorbed by the zeolite. The processing conditions for the drying process are arbitrary, but an example is treating the zeolite in air at 50°C to 150°C, preferably 60°C to 140°C, for 2 hours or more.

In the calcination process, organic matter contained in the zeolite is burned and removed. The processing conditions for the calcination process are arbitrary, but a specific example of the process is to treat the zeolite in air at 500°C to 900°C, preferably 550°C to 850°C.

In the ion exchange process, the zeolite is converted to an arbitrary cation type. For example, metal ions can be ion-exchanged to non-metal cations such as ammonium ions ( _NH4 ⁺ ) or protons (H ⁺ ). A specific example of the ion exchange to ammonium ions is mixing the zeolite with an aqueous ammonium chloride solution and stirring the mixture. A specific example of the ion exchange to protons is calcining the zeolite after ion exchange with ammonia.

In the metal-containing process, the metal is brought into contact with the zeolite to modify the zeolite with the metal, thereby containing the metal. There are no particular limitations on the metal to be contained, but it is preferable that the metal be at least one of copper (Cu) and iron (Fe).

When the zeolite of the present disclosure contains at least one of copper (Cu) and iron (Fe), it is preferable to use a compound containing at least one of copper and iron (hereinafter also referred to as "copper compound, etc."), and it is more preferable to use at least one of the group consisting of inorganic acid salts containing at least one of copper and iron, and further sulfates, nitrates, acetates, and chlorides containing at least one of copper and iron.

The metal-containing step may be any method in which at least one of the ion exchange sites and pores of the zeolite is contained in or modified with a metal. Specific methods include at least one of the group consisting of the ion exchange method, the evaporation to dryness method, and the impregnation method, and the impregnation method and a method of mixing an aqueous solution containing a transition metal compound with the zeolite are preferable.

After the metal-containing step, at least one of the following steps may be included: a cleaning step, a drying step, or an activation step.

Any cleaning method can be used for the cleaning process after the metal-containing process, as long as impurities are removed. For example, the zeolite can be washed with a sufficient amount of pure water.

The drying process after the metal-containing process is sufficient to remove moisture, and can be performed in air at a temperature of 100°C to 200°C, preferably 110°C to 190°C.

The activation step after the metal-containing step removes organic matter. For example, the metal-containing zeolite is treated in air at a temperature above 200°C and below 600°C, and preferably in air at a temperature above 300°C and below 600°C.

The zeolite of the present disclosure can be used as a catalyst, for example, as a catalyst for producing lower olefins from alcohols or ketones, a cracking catalyst, a dewaxing catalyst, an isomerization catalyst, and a catalyst for reducing nitrogen oxides from exhaust gas. It is particularly preferable to use it as a nitrogen oxide reduction catalyst.

The zeolite disclosed herein can be suitably used in methods for reducing nitrogen oxides.

The present disclosure will be explained below with reference to examples. However, the present disclosure is not limited to these examples. Note that "ratio" refers to "molar ratio" unless otherwise specified.

(Identification of crystal structure)
A general X-ray diffraction device (name: Ultima IV, manufactured by Rigaku Corporation) was used to perform XRD measurement of the sample. CuKα radiation (λ = 1.5405 Å) was used as the radiation source, and the measurement range was 2θ from 3° to 43°. The obtained diffraction profile was peak-separated using a pseudovoigt function, and the angle, lattice spacing (hereinafter also referred to as "d"), peak height, and FWHM of each peak were obtained.

The LEV ratio and ERI/OFF ratio were determined by comparing the XRD peaks of the obtained XRD pattern with the DIFFaX pattern. Here, the DIFFaX patterns used for comparison were the simulation patterns shown in Figures 1 to 3, and were created with the volume ratio of each structure relative to the total of the LEV structure, ERI structure, and OFF structure being 0 to 100%.

(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 a general ICP device (device name: _OPTIMA5300DV , manufactured by PerkinElmer). The _SiO2 / _Al2O3 ratio of the sample was calculated from the obtained measured values of Si and Al.

(Measurement of specific surface area)
The specific surface area of the sample was calculated by nitrogen adsorption measurement. A general nitrogen adsorption device (device name: BelsorpMax, manufactured by Microtrack Bell Co., Ltd.) was used for the nitrogen adsorption measurement. The sample was pretreated at 350°C under vacuum for 2 hours, and nitrogen gas was adsorbed at liquid nitrogen temperature. The BET method was used to calculate the value.

Example 1 (Preparation of Zeolite)
A precursor mixture having the following composition was obtained by mixing FAU type aluminosilicate (SiO ₂ /Al ₂ O ₃ ratio=20) and an aqueous TEAOH solution.

_SiO2 / _{Al2O3 ratio} =20
TEA ⁺ /SiO ₂ ratio = 0.4
DMPy ⁺ /SiO ₂ ratio = 0
K/ _SiO2 ratio = 0
Na/ _SiO2 ratio = 0
OH/ _SiO2 ratio = 0.4
_H2O / _SiO2 ratio = 6.5
The obtained precursor mixture was filled into a sealed container, and the container was stirred at 100 rpm while reacting for 12 hours at 90° C. The sealed container was cooled and opened, and pure water, sodium hydroxide, potassium hydroxide, and an aqueous DMPyCl solution were mixed to obtain a raw material composition having the following composition.

_SiO2 / _{Al2O3 ratio} =20
TEA ⁺ /SiO ₂ ratio = 0.4
DMPy ⁺ / _SiO2 ratio=0.2
K/ _SiO2 ratio = 0.05
Na/ _SiO2 ratio = 0.1
OH/ _SiO2 ratio = 0.55
_H2O / _SiO2 ratio=20
The main components of the raw material composition are shown in Table 5.

The obtained raw material composition was filled into a sealed container, and the container was stirred at 100 rpm while reacting at 150°C for 72 hours. After crystallization, the raw material composition was separated into solid and liquid, washed with pure water, and then dried at 110°C.

The resulting dried powder was calcined in air at 550°C for 2 hours to obtain the zeolite of this example. The XRD pattern of the zeolite of this example is shown in Table 6. In this example, the peak intensity was calculated using the peak at 2θ = 23.6° as the reference peak.

The zeolite of this example had a SiO ₂ /Al ₂ O ₃ ratio of 14 and a specific surface area of 526 m ² /g.

The presence of XRD peaks at 2θ = 9.7° and 25.2° suggests that the zeolite of this example has a region in which the ERI structure and LEV structure are continuous. On the other hand, the absence of XRD peaks derived from other ERI structures, such as the XRD peak at 2θ = 24.8°, suggests that the zeolite does not contain a zeolite consisting of a crystal structure consisting of only the ERI structure. In addition, since the XRD pattern differs from that of a zeolite consisting of an intergrowth of only the LEV structure and the ERI structure, the zeolite of this example is a zeolite consisting of an intergrowth having the LEV structure and the ERI structure, as well as other crystal structures.

The presence of the OFF structure can be confirmed from 2θ of the LEV ₍₀₁₂₎ -ERI ₍₁₀₁₎ peak. Therefore, the zeolite of this example is a zeolite consisting of an intergrowth having the LEV structure, the ERI structure, and the OFF structure.

The ratio (A/B) of the strongest peak intensity (A) in the range of 2θ = 20.75 ± 0.7° (peak intensity: 125 (20.8°)) to the strongest peak intensity (B) in the range of 2θ = 22.25 ± 0.7° (peak intensity: 131 (22.4°)) is 0.98, and a comparison with the ratio (A/B) value in the DIFFaX pattern indicates that the LEV ratio is 60-80%.

Furthermore, the 2θ of the LEV ₍₀₁₂₎ -ERI ₍₁₀₁₎ peak is 11.1° and the ERI/OFF ratio is <1.

Based on the above facts, the zeolite of this embodiment is a zeolite consisting of an intergrowth of LEV structure, ERI structure, and OFF structure, and the ERI/OFF ratio is <1.

The SEM photograph of the zeolite of this example is shown in Figure 5.

Comparative Example 1
A precursor mixture was obtained in the same manner as in Example 1, and then the zeolite of this comparative example was obtained in the same manner as in Example 1, except that the raw material composition had the following composition.

_SiO2 / _{Al2O3 ratio} =20
TEA ⁺ /SiO ₂ ratio = 0.4
DMPy ⁺ / _SiO2 ratio=0.2
K/ _SiO2 ratio = 0
Na/ _SiO2 ratio = 0.1
OH/ _SiO2 ratio=0.5
_H2O / _SiO2 ratio=20
The zeolite in this comparative example was a mixture of zeolite with a *BEA structure and zeolite with a LEV structure, and was a different substance from the zeolite in the present disclosure. The main components of the raw material composition are also shown in Table 5.

From Table 5, it can be confirmed that the zeolite disclosed herein can be obtained by including potassium cations.

Comparative Example 2
A precursor mixture was obtained in the same manner as in Example 1, and then the zeolite of this comparative example was obtained in the same manner as in Example 1, except that the raw material composition had the following composition.

_SiO2 / _{Al2O3 ratio} =20
TEA ⁺ /SiO ₂ ratio = 0.4
DMPy ⁺ /SiO ₂ ratio = 0
K/ _SiO2 ratio = 0.05
Na/ _SiO2 ratio = 0.1
OH/ _SiO2 ratio = 0.55
_H2O / _SiO2 ratio=20
The zeolite in this comparative example was a zeolite having a *BEA structure, and was a different substance from the zeolite in the present disclosure. The main components of the raw material composition are also shown in Table 5.

From Table 5, it was confirmed that the zeolite of the present disclosure can be obtained by containing DMPy ⁺ .

Example 2 (Preparation of metal-containing zeolite)
The zeolite of Example 1 was suspended in a 20 wt % aqueous NH ₄ Cl solution, and the cation type was converted to the NH ₄ type by solid-liquid separation and washing with hot water.

1.1 _g of the obtained NH4 type zeolite was weighed out, and an aqueous solution of copper nitrate was added thereto and mixed in a mortar. The aqueous solution of copper nitrate was prepared by dissolving 127 mg of copper nitrate trihydrate in 0.5 g of pure water.

After mixing, the sample was dried overnight at 110°C and then calcined in air at 550°C for 1 hour to modify the copper into zeolite, resulting in a copper-containing intergrowth zeolite containing 3% by mass of copper.

Reference Example 1
According to the description of U.S. Patent No. 4,544,538, a CHA _- type zeolite having a _SiO2 / _Al2O3 ratio of 25 was prepared. The obtained dried powder was calcined in air at 550°C for 2 hours and treated in the same manner as in Example 2 to obtain a copper-containing CHA-type zeolite containing 1.7 mass% copper.

Measurement Example 1
The copper-containing intergrowth zeolite obtained in Example 2 and the copper-containing CHA-type zeolite obtained in Reference Example 1 were used as nitrogen oxide reduction catalysts, and their nitrogen oxide reduction properties were evaluated by the ammonia SCR method described below.

(Sample pretreatment)
The sample was press-molded to form agglomerated particles having an aggregate diameter of 12 to 20 meshes. 1.5 mL of the resulting agglomerated particles was weighed out and filled into a reaction tube.

(Evaluation of nitrogen oxide reduction properties)
A treatment gas containing nitrogen oxides and having the following composition was passed through the reaction tube at a temperature of 200° C., 300° C., 400° C., or 500° C. Measurements were performed with a treatment gas flow rate of 1.5 L/min and a space velocity (SV) of 60,000 h ^-1 .

<Processing gas composition>
NO: 200 ppm
_NH3 : 200 ppm
_O2 : 10% by volume
_H2O : 3% by volume
Remainder: _N2
The nitrogen oxide concentration (ppm) in the treated gas after passing through the catalyst relative to the nitrogen oxide concentration (200 ppm) in the treated gas passed through the reaction tube was determined, and the nitrogen oxide reduction rate was calculated according to the following formula.

Nitrogen oxide reduction rate (%)={1-(nitrogen oxide concentration in treated gas after contact/nitrogen oxide concentration in treated gas before contact)}×100
The results are shown in Table 7.

From Table 7, it was confirmed that the copper-containing zeolite disclosed herein has nitrogen oxide reduction properties equivalent to those of CHA-type zeolites that are used in practical applications as SCR catalysts.

Measurement Example 2
The copper-containing intergrowth zeolite obtained in Example 2 was used as a nitrogen oxide reduction catalyst, and the nitrogen oxide reduction characteristics after hydrothermal durability treatment were evaluated under the same conditions as those of the ammonia SCR method shown in Measurement Example 1. The hydrothermal durability treatment conditions are shown below.

(Hydrothermal durability treatment conditions)
Treatment temperature: 900°C
Treatment time: 1 hour Treatment atmosphere: under water-containing air flow (10% by volume of water, 90% by volume of air)
Heating rate: 20°C/min Heating atmosphere: from room temperature to 200°C under air circulation
After hydrothermal durability treatment in a water-containing air stream above 200°C, the nitrogen oxide reduction rates at 200°C, 300°C, 400°C and 500°C were 48%, 82%, 65% and 48%, respectively.

Claims (8)

A zeolite characterized in that it has the powder X-ray diffraction peaks shown in the table below, has a specific surface area of 300 m ² /g or more and 800 m ² /g or less, and is a crystalline aluminosilicate.
The zeolite according to claim 1, which is an intergrowth of the LEV structure, the ERI structure and the OFF structure. The zeolite according to claim 2, wherein the volume ratio of the LEV structure to the total of the LEV structure, the ERI structure, and the OFF structure is 50% or more and 80% or less. The zeolite according to claim 1 or 2, in which the molar ratio of silica to alumina is 5 or more and 50 or less. The zeolite according to claim 1 or 2, which contains at least one of copper and iron. The zeolite according to claim 1 or 2, which has a powder X-ray diffraction peak at 2θ = 25.2 ± 0.2° when CuKα radiation is used as the radiation source. The zeolite according to claim 6, in which the ratio of the intensity of the powder X-ray diffraction peak at 2θ = 25.2 ± 0.2° to the intensity of the powder X-ray diffraction peak at 2θ = 23.6 ± 0.2° when CuKα radiation is used as a radiation source is 20 or more and 40 or less. A nitrogen oxide reduction catalyst comprising the zeolite according to claim 1 or 2.