JP7185433B2 - Gas separation method - Google Patents

Description

The present invention relates to gas separation methods.

In recent years, the need for separation of methane and carbon dioxide has increased due to the expansion of the need for natural gas and the utilization of biomass as a resource. Furthermore, in order to reduce carbon dioxide emissions, there is an increasing need for separating and recovering carbon dioxide from exhaust gas in power plants and the steel industry, and the development of carbon dioxide separation technology is being actively carried out. There are several methods for separating carbon dioxide, one of which is a method using an adsorbent. In the separation method using an adsorbent, the pressure at the time of desorption is lowered from the pressure at which the gas is adsorbed, and the difference between the adsorption amount at high pressure and the adsorption amount at low pressure is used to separate the gas. A swing type adsorption separation method (PSA: Pressure Swing Adsorption) raises the temperature at the time of desorption from the temperature at the time of gas adsorption, and separates the gas using the difference between the adsorption amount at low temperature and the adsorption amount at high temperature. There is a temperature swing adsorption separation method (TSA: Thermal Swing Adsorption). Furthermore, there is a pressure and temperature swing type adsorption desorption method (PTSA: Pressure and Thermal Swing Adsorption) that combines these methods. When separating and refining a high-pressure gas such as natural gas, PSA adsorbs carbon dioxide at high pressure during adsorption, desorbs the adsorbed carbon dioxide by reducing the pressure, and separates and recovers it, resulting in a highly energy-efficient recovery method. becomes. In the case of gases close to normal pressure, such as biomass and exhaust gas from power plants, the pressure may be increased in advance with a compressor and then adsorbed on an adsorbent, and the pressure may be reduced to desorb carbon dioxide. After being adsorbed by an adsorbent, the pressure may be lowered with a vacuum pump to desorb carbon dioxide. These gas separations can also be performed with TSA. If there is an available heat source such as a power plant or ironworks, it can be used for desorption, so the cost for desorption and regeneration from the adsorbent can be reduced. Exhaust gas and adsorbent are brought into contact at a certain temperature, and if the temperature is raised above that temperature, the adsorbed gas is desorbed and can be separated and recovered. As for the method of increasing the temperature, the container containing the adsorbent may be heated from the outside, or a heater or heat exchanger may be placed inside the container to heat it. You may heat by making it distribute|circulate to a container. A gas heated to a high temperature is excellent in that, when carbon dioxide is separated, high-purity carbon dioxide can be collected by heating and circulating the separated and recovered carbon dioxide. In addition, when water vapor is added to the gas heated to a high temperature, the heating efficiency is high because water has a large heat capacity. It is excellent because it can be separated. Since the adsorbent is heated by adsorption energy during adsorption, the adsorption amount tends to decrease as the adsorption amount increases. Conversely, since the adsorbent is cooled by the heat of vaporization during desorption, the efficiency of desorption decreases as desorption progresses. Therefore, by installing multiple vessels filled with adsorbents and introducing heat exchangers, the energy required for adsorption and desorption can be reduced by exchanging the heat of adsorption and the heat of vaporization between the vessels performing adsorption and the vessels performing desorption. can be achieved. The heat exchanger may connect the container with a material with high thermal conductivity such as metal, or may have a pipe through which a heat medium passes through the interior of the container. A rotor-type heat exchanger may be used in which a rotor is provided with a plurality of adsorbent-filled layers for continuous adsorption and desorption.
Activated carbon is widely used as an adsorbent. However, activated carbon has a low adsorption capacity and insufficient selective adsorption of carbon dioxide. In recent years, FAU-type zeolite, which is a kind of zeolite, and adsorbents obtained by ion-exchanging FAU-type zeolite to Li-type have been used (Patent Document 1). Furthermore, GIS-type zeolite (Patent Document 2) and MWF-type zeolite (Patent Document 3) have recently been disclosed as zeolites having extremely high selective adsorption of carbon dioxide.

Japanese Patent Application Laid-Open No. 2002-191924 WO2018/110559 WO2017/222028A1

Although the Li-exchanged FAU-type zeolite described in Patent Document 1 absorbs a large amount of carbon dioxide, the adsorption selectivity for nitrogen and methane is insufficient, so there is still room for improvement in terms of gas separation efficiency. Further, according to Patent Documents 2 and 3, carbon dioxide can be efficiently adsorbed and separated by appropriately synthesizing GIS-type zeolite and MWF-type zeolite and appropriately controlling the XRD spectrum intensity ratio. It has been shown that the narrower the half-value width of the peak in the XRD spectrum, the better, and the higher the crystallinity, the better. However, the half-value width of the peak of the XRD spectrum is also affected by the crystallite size, and the larger the crystallite size, the narrower the half-value width. As the crystallite size increases, the crystal becomes larger, the surface area decreases, and grain boundaries and crystal defects that allow gas molecules to flow are reduced. When the surface area, grain boundaries, and crystal defects are reduced, the number of sites where substances other than carbon dioxide are adsorbed on the crystal is reduced, so it is thought that the selective adsorption of carbon dioxide is improved. When performing , the adsorption capacity of carbon dioxide is reduced, and the distance required to move in the zeolite lattice during adsorption and desorption increases, which may lead to a decrease in the adsorption rate and desorption rate.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a gas separation method capable of efficiently separating a specific gas.

The present inventors have made intensive studies to solve the above problems, and as a result, in the gas separation method by PSA, TSA or PTSA, the half width of the peak in the XRD spectrum of GIS type zeolite or MWF type zeolite is within a predetermined range. In some cases, we found that the problem can be solved, and furthermore, we found that the problem can be solved in the same way when the half width of the peak in the XRD spectrum is within a predetermined range even with K-exchanged GIS zeolite. I came up with the invention.

That is, the present invention is as follows.
[1]
A method for separating gases by a temperature swing adsorption gas separation method, a pressure swing adsorption gas separation method, or a pressure/temperature swing adsorption desorption method using an adsorbent,
The adsorbent is a GIS-type zeolite in which the half width of the peak near 2θ = 12.4° in the XRD spectrum is 0.05 ° or more and 0.44 ° or less, and the peak near 2θ = 12.7 ° in the XRD spectrum K-exchanged GIS zeolite having a half-value width of 0.08° or more and 0.55° or less, and a half-value width of the peak near 2θ = 11.1° in the XRD spectrum of 0.06° or more and 0.31° or less A gas separation method comprising at least one selected from the group consisting of certain MWF-type zeolites.
[2]
When the adsorbent contains the GIS-type zeolite and the peak heights near 2θ = 12.4 and 21.6 ° in the peak obtained by X-ray diffraction of the GIS-type zeolite are A and B, respectively , 1.37<A/B, the gas separation method according to [1].
[3]
The adsorbent contains the MWF-type zeolite, and the MWF-type zeolite is 0.61 ≤ B / A ≤ when the peak heights near 2θ = 11.1 and 13.8 ° are A and B, respectively. The gas separation method according to [1] or [2], which satisfies 0.83.
[4]
Separating carbon dioxide from a mixed gas containing carbon dioxide and at least one selected from the group consisting of hydrocarbons, methane, nitrogen, carbon monoxide, hydrogen, helium and argon, [1] to [3] Gas separation method according to any one of.

ADVANTAGE OF THE INVENTION According to this invention, the gas separation method which can isolate|separate a specific gas efficiently can be provided.

FIG. 1 is a diagram illustrating a PSA according to one embodiment of the invention. FIG. 2 is a diagram illustrating a TSA according to one embodiment of the invention. FIG. 3 is a diagram illustrating the gas adsorption/separation performance evaluation device of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, the form (henceforth "this embodiment") for implementing this invention is demonstrated in detail. The present invention is not limited to the following description, and various modifications can be made within the scope of the gist thereof.

The gas separation method of the present embodiment uses an adsorbent to separate gases by a temperature swing adsorption gas separation method, a pressure swing adsorption gas separation method, or a pressure/temperature swing adsorption desorption method. , the adsorbent is a GIS-type zeolite in which the half width of the peak at 2θ = 12.4° in the XRD spectrum is 0.05 ° or more and 0.44 ° or less, half of the peak at 2θ = 12.7 ° in the XRD spectrum K-exchanged GIS zeolite with a value width of 0.08° or more and 0.55° or less, and MWF whose half width of the peak at 2θ = 11.1° in the XRD spectrum is 0.06° or more and 0.31° or less At least one selected from the group consisting of type zeolites. Since the gas separation method of this embodiment is configured as described above, it is possible to efficiently separate a specific gas.
The GIS-type zeolite, K-exchanged GIS-type zeolite, and MWF-type zeolite that function as adsorbents in this embodiment will be described in detail below. In this specification, these zeolites may be collectively referred to as "the zeolite of the present embodiment".

<GIS type zeolite>
(XRD peak half width)
Among the X-ray diffraction peaks at 25° C. of the GIS-type zeolite in the present embodiment, the peak near 2θ=12.4° is the (1 0 1) diffraction peak, typically from 12.15° to 12.4°. Observed in the range of 75°. The peak half-value width obtained by X-ray diffraction indicates the crystallinity and crystallite size of the crystal lattice plane where the diffraction occurs, and the narrower the peak, the higher the crystallinity. On the other hand, if the half-value width is narrow, the crystallite size becomes larger, the size of the crystal becomes larger, the adsorption sites of gas molecules such as grain boundaries and crystal defects, and the pores through which gas molecules can easily diffuse are reduced. Since the surface area is reduced, the half width is preferably wide to some extent from the viewpoint of the amount of adsorption sites for gas molecules and the rate of gas adsorption and desorption. Therefore, the range of the peak half width near 2θ = 12.4 of the GIS-type zeolite in the present embodiment is 0.05° or more and 0.44° or less, preferably 0.06° or more and 0.43° or less. and more preferably 0.07° or more and 0.42° or less. According to the structure of GIS-type zeolite, which is suggested by having such a peak half-width, molecules other than CO ₂ such as CH ₄ do not permeate the crystal lattice, the amount of adsorption is reduced, and the amount of CO ₂ is reduced. By eliminating the lack of adsorption sites, the amount of these adsorptions can be maximized, and an appropriate surface area and diffusion path for gas molecules can be secured, so the selective adsorption of CO ₂ can be maximized. presumed by
The half-value width of the peak is determined by a method of adjusting the composition ratio of the mixed gel, the aging time of the mixed gel, the conditions during hydrothermal synthesis (heating temperature and heating time), etc. to the preferable range described later. , can be adjusted to the above range.

(X-ray diffraction peak intensity ratio)
In the GIS-type zeolite of the present embodiment, in the peak obtained by X-ray diffraction, when the peak heights near 2θ = 12.4 ° and 21.6 ° are A and B, respectively, 1.37 < A / B is preferably satisfied. A peak near 2θ = 12.4° is typically observed in the range of 12.15° to 12.75°, and a peak near 2θ = 21.6° is typically observed at 2θ = 20.1°. ° to 24.1°.
Among the X-ray diffraction peaks at 25° C. of the GIS-type zeolite in the present embodiment, the peaks near 2θ=12.4° and 21.6° are the (1 0 1) and (2 1 1) diffraction peaks, respectively. be. The (1 0 1) diffraction peak is diffraction reflecting the periodic structure of the eight-membered oxygen ring of the GIS-type zeolite, and the (2 1 1) diffraction peak is diffraction reflecting a finer structure. When the heights of the diffraction peaks of (1 0 1) and (2 1 1) are A and B, respectively, when A/B is large, a larger periodic structure, that is, a structure containing an 8-membered ring structure is clear. It is shown that. It is known that the cations contained in zeolite can move, and the large periodic structure including the 8-membered ring structure has no defects and is clearly formed, which increases the mobility of cations and allows carbon dioxide to enter the pores. It is thought that the ability to adsorb carbon dioxide develops by moving without hindrance when it invades. From this point of view, A/B is preferably greater than 1.37, more preferably greater than 1.40, and still more preferably 1.50 or more.
The above A/B value and half value width can be measured by the method described in Examples below, and all of them are determined by the composition ratio of the mixed gel, the aging time of the mixed gel, and the conditions during hydrothermal synthesis ( The above range can be adjusted by a method for adjusting the heating temperature, heating time, etc., within a preferable range described later.

(Synthesis method)
The method for producing a GIS-type zeolite in the present embodiment includes, for example, a silica source containing silicon, an aluminum source containing aluminum, an alkali metal source containing at least one selected from alkali metals (M1) and alkaline earth metals (M2). , a phosphorus source containing phosphorus, and a step of preparing a mixed gel containing water. The mixed gel and each component contained therein will be described below.

[Mixed gel]
The mixed gel in the present embodiment is a mixture containing a silica source, an aluminum source, an alkali metal source and water as components, and optionally a phosphorus source and an organic structure directing agent.
The silica source means a component in the mixed gel that serves as a raw material for silicon contained in the zeolite produced from the mixed gel, and the aluminum source means a raw material for aluminum contained in the zeolite produced from the mixed gel. An alkali metal source refers to a component in the mixed gel that serves as a raw material for the alkali metal and/or alkaline earth metal contained in the zeolite produced from the mixed gel, and phosphorus A source refers to a component in the mixed gel that is a source of phosphorus contained in the zeolite produced from the mixed gel.

[Silica source]
The silica source is not particularly limited as long as it is commonly used, but specific examples include sodium silicate, amorphous silica, colloidal silica, wet silica, dry silica, silica gel, and amorphous aluminosilicate. gel, tetraethoxysilane (TEOS), trimethylethoxysilane, and the like. These compounds may be used singly or in combination. Here, the amorphous aluminosilicate gel serves as both a silica source and an aluminum source.
Among these, sodium silicate is preferred because it tends to yield a zeolite with a high degree of crystallinity.

[Aluminum source]
The aluminum source is not particularly limited as long as it is commonly used, but specific examples include sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum acetate, aluminum hydroxide, aluminum oxide, aluminum chloride, and aluminum alkoxide. , metallic aluminum, amorphous aluminosilicate gel, and the like. These compounds may be used singly or in combination.
Among these, sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum acetate, aluminum hydroxide, aluminum chloride, and aluminum alkoxide are preferred because they tend to yield zeolite with a high degree of crystallinity. From the same point of view, sodium aluminate and aluminum hydroxide are more preferred, and sodium aluminate is even more preferred.

[Alkali metal source]
The type of alkali in the alkali metal source is not particularly limited, and any alkali metal and/or any alkaline earth metal compound can be used.
Alkali metal sources include, but are not limited to, alkali metal or alkaline earth metal hydroxides, bicarbonates, carbonates, acetates, sulfates, nitrates, and the like. These compounds may be used alone or in combination.
Li, Na, K, Rb, Cs, Ca, Mg, Sr, Ba and the like can be used as alkali metals and alkaline earth metals used as alkali metal sources. Na and K are preferred, and Na is more preferred, from the viewpoint of facilitating crystal formation of the GIS-type skeleton. Also, the alkali metals and alkaline earth metals used as the alkali metal source may be used singly or in combination.
Specifically, examples of alkali metal sources include, but are not limited to, sodium hydroxide, sodium acetate, sodium sulfate, sodium nitrate, sodium carbonate, sodium hydrogen carbonate, potassium hydroxide, potassium acetate, potassium sulfate, potassium nitrate. , potassium carbonate, potassium hydrogen carbonate, lithium hydroxide, lithium acetate, lithium sulfate, lithium nitrate, lithium carbonate, lithium hydrogen carbonate, rubidium hydroxide, rubidium acetate, rubidium sulfate, rubidium nitrate, rubidium carbonate, rubidium hydrogen carbonate, hydroxide Cesium, cesium acetate, cesium sulfate, cesium nitrate, cesium carbonate, cesium hydrogen carbonate, calcium hydroxide, calcium acetate, calcium sulfate, calcium nitrate, calcium carbonate, calcium hydrogen carbonate, magnesium hydroxide, magnesium acetate, magnesium sulfate, magnesium nitrate , magnesium carbonate, magnesium hydrogen carbonate, strontium hydroxide, strontium acetate, strontium sulfate, strontium nitrate, strontium carbonate, strontium hydrogen carbonate, barium hydroxide, barium acetate, barium sulfate, barium nitrate, barium carbonate, barium hydrogen carbonate, etc. be done.
Among these, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide, calcium hydroxide, magnesium hydroxide, strontium hydroxide and barium hydroxide are preferred, and sodium hydroxide, potassium hydroxide, Lithium hydroxide, rubidium hydroxide and cesium hydroxide are more preferred, and sodium hydroxide is even more preferred.

[Phosphorus source]
The phosphorus source is not particularly limited as long as it is commonly used, but specific examples include phosphoric acid aqueous solution, sodium phosphate, aluminum phosphate, potassium phosphate, lithium phosphate, calcium phosphate, and barium phosphate. etc. These compounds may be used singly or in combination.
Among these, phosphoric acid aqueous solution, sodium phosphate, and aluminum phosphate are preferred because they tend to yield zeolite with a high degree of crystallinity. From the same point of view, an aqueous phosphoric acid solution and sodium phosphate are more preferred, and an aqueous phosphoric acid solution is even more preferred.

[Organic Structure Directing Agent]
The organic structure-directing agent in producing zeolite by hydrothermally synthesizing a mixed gel is a compound that promotes crystallization into a zeolite structure. In crystallization of zeolite, an organic structure-directing agent can be used as necessary.
The organic structure-directing agent may be of any type as long as it can form a desired GIS-type zeolite. Also, the organic structure-directing agents may be used singly or in combination.
Examples of organic structure-directing agents include, but are not limited to, amines, quaternary ammonium salts, alcohols, ethers, amides, alkylureas, alkylthioureas, cyanoalkanes, containing nitrogen as a heteroatom. Alicyclic heterocyclic compounds can be used, preferably alkylamines, more preferably isopropylamine.
Some such salts are associated with an anion. Representatives of such anions include, but are not limited to, halogen ions such as Cl ⁻ , Br ⁻ , I ⁻ , hydroxide ions, acetate ions, sulphate ions, nitrate ions, carbonate ions and carbonate ions. Contains hydrogen ions. Among these, halogen ions and hydroxide ions are preferred, and halogen ions are more preferred, from the viewpoint of facilitating the formation of crystals of the GIS type skeleton.

[Composition ratio of mixed gel]
The ratio of silica source and aluminum source in _the mixed gel is expressed as the molar ratio of the oxides of the respective elements, ie _SiO2 / _Al2O3 .
The ratio of SiO ₂ /Al ₂ O ₃ is not particularly limited as long as it can form zeolite. 0 or less is preferable, 4.2 or more and 68.0 or less is more preferable, 5.0 or more and 60.0 or less is still more preferable, and 5.3 or more and 58.0 or less is even more preferable. It is more preferably 0 or more and 50.0 or less, and even more preferably 6.5 or more and 49.0 or less.
The ratio of the aluminum source and the alkali metal source in the mixed gel is expressed as _{the additive molar ratio of M12O and M2O to Al2O3, that is, (M12O + M2O ) / Al2O3} (where M1 is an alkali metal and M2 represents an alkaline earth metal). From the viewpoint of facilitating crystal formation of the GIS-type skeleton, this (M1 ₂ O+M2O)/Al ₂ O ₃ ratio is preferably 1.3 or more, more preferably 1.4 or more. It is more preferably 1.5 or more, even more preferably 1.6 or more, still more preferably 1.7 or more, and even more preferably 1.8 or more.
(M1 ₂ O+M2O)/Al ₂ O ₃ is preferably 2.0 or more and 80.0 or less, more preferably 2.2 or more and 78.0 or less, from the viewpoint of suppressing the formation of zeolite having a skeleton different from the GIS type skeleton. more preferably 2.5 or more and 70.0 or less, even more preferably 2.7 or more and 68.0 or less, even more preferably 3.0 or more and 60.0 or less, 3.3 It is even more preferable that it is not less than 56.0 and not more than 56.0.
The ratio of the phosphorus source and the aluminum source in _the mixed gel is expressed as the molar ratio of the oxides _of the respective elements, ie _P2O5 / _Al2O3 .
The ratio of P ₂ O ₅ O ₂ /Al ₂ O ₃ is not particularly limited as long as the ratio is such that zeolite can be formed. It is preferably less than 0, more preferably 0.6 or less, even more preferably 0.4 or less, and particularly preferably 0.
When the mixed gel contains _an organic structure directing agent, _the ratio of the aluminum source to the organic structure directing agent in the mixed gel is expressed as the molar ratio of organic structure directing agent to _Al2O3 , i.e., R/ _Al2O3 . (where R represents an organic structure directing agent). It is preferably less than 10.0, more preferably 8.0 or less, from the viewpoint of easier crystal formation of the GIS-type skeleton and/or shorter synthesis time and excellent economic efficiency in producing zeolite. It is preferably 6.0 or less, more preferably 6.0 or less.
_The ratio of aluminum source to water in the mixed gel is expressed as the molar ratio _of water to _Al2O3 , _H2O / _Al2O3 . It is preferably 100 or more, more preferably 200 or more, because the components in the mixed gel tend to be more uniformly dispersed. From the viewpoint of suppressing the formation of zeolite having a skeleton different from the GIS-type skeleton and producing a GIS-type zeolite with high crystallinity, it is more preferably 300 or more.
When the H ₂ O/Al ₂ O ₃ ratio is high, the crystallinity is improved, but the number of nuclei generated for crystal growth is reduced, and the crystallite size tends to increase and the particle size also tends to increase. Furthermore, since the crystals during growth are less likely to come into contact with each other and be integrated, it is possible to grow a highly crystalline GIS with a small number of crystallites and few grain boundaries and crystal defects. High crystallinity clearly forms the 8-membered ring structure of GIS, which is important for improving carbon dioxide selectivity. It is also important to increase the adsorption capacity due to the presence of many carbon dioxide adsorption sites, and to increase the adsorption and desorption rate due to the presence of fast gas diffusion paths such as grain boundaries and defects in crystallites. . Therefore, if the crystallinity is too high, the performance as an adsorbent is lowered, so if the H ₂ O/Al ₂ O ₃ ratio is too high, it is not preferable. Furthermore, the lower the H ₂ O/Al ₂ O ₃ ratio, the shorter the synthesis time and the more economical the production of zeolite. From the above viewpoints, it is preferably less than 1500, more preferably 1400 or less, and even more preferably 1300 or less.
As described above, in the method for producing a GIS-type zeolite in the present embodiment, a silica source containing silicon, an aluminum source containing aluminum, and at least one selected from alkali metals (M1) and alkaline earth metals (M2) are used. a step of preparing a mixed gel containing an alkali metal source, a phosphorus source, and water, wherein the molar ratio of each component in the mixed gel is adjusted to the silicon, aluminum, alkali metal (M1) and alkaline earth metal (M2), when calculating the phosphorus source as an oxide of each element, the molar ratios α, β, γ, δ represented by the following formulas (1), (2), (3) and (4) are 4.0 ≤ α ≤ 70.0, 2.0 ≤ β ≤ 80.0, 0 ≤ γ < 1.0 and 100 ≤ δ ≤ 3000 are preferably satisfied, 4.2 ≤ α ≤ 68.0, 2 .2≤β≤78.0, 0≤γ<1.0 and 100≤δ≤1500 are preferably satisfied. It is particularly preferable that the GIS-type zeolite in this embodiment is obtained by the method for producing a GIS-type zeolite in this embodiment described above.
α=SiO ₂ /Al ₂ O ₃ (1)
β=(M1 ₂ O+M2O)/Al ₂ O ₃ (2)
γ=P ₂ O ₅ /Al ₂ O ₃ (3)
δ=H ₂ O/Al ₂ O ₃ (4)
Furthermore, in the method for producing a GIS-type zeolite according to the present embodiment, when the molar ratios α, β, γ, and δ satisfy the above ranges and the mixed gel further contains an organic structure directing agent R, the following formula (5) The molar ratio ε represented by preferably satisfies ε<10.
ε=R/Al ₂ O ₃ (5)
Although seed crystals do not necessarily exist in the mixed gel, the GIS-type zeolite of the present embodiment can be obtained by adding previously produced GIS-type zeolite as seed crystals to the mixed gel.

[Preparation process of mixed gel]
The process for preparing the mixed gel is not particularly limited. and aging the mixture obtained in the step.
In the mixing step, these components including a silica source, an aluminum source, an alkali metal source, water, and, if necessary, an organic structure-directing agent can be mixed at once or in multiple stages.
The order of mixing in multiple stages is not limited, and may be appropriately selected depending on the conditions used. Mixing in multiple stages may be carried out with or without stirring.
The stirring is not particularly limited as long as it is a generally used stirring method, but specific examples include methods using blade stirring, vibration stirring, rocking stirring, centrifugal stirring, and the like.
The rotation speed for stirring is not particularly limited as long as it is a generally used stirring speed, and is, for example, 1 rpm or more and less than 2000 rpm.
The temperature of the mixing step is not particularly limited as long as it is a temperature that is generally used, but for example, -20°C or higher and lower than 80°C can be mentioned.
The time of the mixing step is not particularly limited, and can be appropriately selected depending on the temperature of the mixing step.
The aging step may be carried out either by standing still or by stirring.
When stirring in the aging step, there is no particular limitation as long as it is a generally used stirring method, but specific examples include methods using blade stirring, vibration stirring, rocking stirring, centrifugal stirring, and the like. .
The rotation speed for stirring is not particularly limited as long as it is a generally used stirring speed, and is, for example, 1 rpm or more and less than 2000 rpm.
The temperature of the aging step is not particularly limited as long as it is a commonly used temperature, and for example, -20°C or higher and lower than 80°C.
The time for the aging process is not particularly limited, and can be appropriately selected depending on the temperature of the aging process.
It is considered that the zeolite is dissolved in the raw material and the zeolite precursor is formed and re-dissolved in the raw material mixing process and the aging process. In order to form a large periodic structure containing an 8-membered ring without causing defects or the like, it is preferable that the formation of the zeolite precursor does not proceed excessively. In addition, when the formation of the zeolite precursor proceeds excessively, the formation of ANA-type zeolite, which has a more stable structure, tends to increase, so it is preferable not to ripen excessively. On the other hand, it is preferable that the raw materials are sufficiently mixed and the raw material gel is uniform. From these points of view, the combined time of the mixing step and the aging step is preferably 1 minute or more and less than 24 hours, more preferably 1 minute or more and less than 23 hours, still more preferably 2 minutes or more and 12 hours or less, and 2 minutes or more and 10 hours or less. , more preferably 3 minutes or more and 2 hours or less, and even more preferably 3 minutes or more and 1.5 hours or less.

[Hydrothermal synthesis step]
The method for producing a GIS-type zeolite in the present embodiment preferably further includes a hydrothermal synthesis step in which the hydrothermal synthesis temperature is 80°C to 145°C, and the hydrothermal synthesis temperature is 80°C to 140°C. more preferred. That is, preferably, the mixed gel obtained in the preparation step is hydrothermally synthesized by holding the mixed gel at a predetermined temperature for a predetermined time while stirring or standing still.
The temperature for hydrothermal synthesis is not particularly limited as long as it is a temperature generally used, but it is preferably 80° C. or higher from the viewpoint of shortening the synthesis time and improving the economic efficiency of zeolite production. From the viewpoint of suppressing the formation of zeolite having a skeleton different from the GIS-type skeleton, the temperature is more preferably 90° C. or higher, and even more preferably 100° C. or higher.
From the viewpoint of suppressing the formation of zeolite having a skeleton different from the GIS-type skeleton, the temperature is more preferably 145° C. or lower, even more preferably 140° C. or lower, and even more preferably 135° C. or lower.
The temperature for hydrothermal synthesis may be constant or may be changed stepwise.
The hydrothermal synthesis time is not particularly limited as long as it is a generally used time, and can be appropriately selected depending on the hydrothermal synthesis temperature.
The hydrothermal synthesis time is preferably 3 hours or longer, more preferably 10 hours or longer, from the viewpoint of formation of the GIS skeleton. From the viewpoint of obtaining highly crystalline GIS-type zeolite, the time is more preferably 24 hours or longer.
The hydrothermal synthesis time is preferably less than 10 days, more preferably 9 days or less, more preferably 8 days, in order to prevent the zeolite particle size from growing too large and to be economical when producing zeolite. More preferably:
In the hydrothermal synthesis step, the container in which the mixed gel is placed is not particularly limited as long as it is a commonly used container. In that case, it is preferable to put it in a pressure vessel and perform hydrothermal synthesis.
The pressure-resistant container is not particularly limited, and various shapes such as a spherical shape, a vertically long shape, and a horizontally long shape can be used.
When stirring the mixed gel in the pressure container, the pressure container is rotated vertically and/or horizontally, preferably vertically.
When rotating the pressure container in the vertical direction, the rotation speed is not particularly limited as long as it is within the range generally used, but is preferably 1 to 50 rpm, more preferably 10 to 40 rpm.
In the hydrothermal synthesis step, in order to preferably stir the mixed gel, there is a method of using a vertically long pressure vessel and rotating it vertically.

[Separation/drying process]
After the hydrothermal synthesis step, the product solid and liquid containing water are separated, but the separation method is not particularly limited as long as it is a general method, and filtration, decantation, spray drying (rotary spray, Nozzle spraying, ultrasonic spraying, etc.), a drying method using a rotary evaporator, a vacuum drying method, a freeze-drying method, a natural drying method, or the like can be used, and the separation can be usually performed by filtration or decantation.
The separated material may be used as it is or washed with water or a predetermined solvent. If desired, the separated material can be dried.
The temperature for drying the separated material is not particularly limited as long as it is a common drying temperature, but it is usually from room temperature to 150°C or less.
The atmosphere for drying is not particularly limited as long as it is a generally used atmosphere, but an air atmosphere, an inert gas such as nitrogen or argon, or an oxygen-added atmosphere is usually used.

[Baking process]
If necessary, calcined GIS type zeolite can be used. The firing temperature is not particularly limited as long as it is a temperature generally used, but when the organic structure directing agent is to be removed, the remaining ratio can be reduced, so it is preferably 300° C. or higher, and 350° C. or higher. is more preferable. A temperature of 400° C. or higher is more preferable from the viewpoint of shortening the calcination time and being excellent in economic efficiency in producing zeolite.
Since the crystallinity of zeolite tends to be maintained, the temperature is preferably less than 550°C, more preferably 530°C or less, and even more preferably 500°C or less.
The calcination time is not particularly limited as long as the organic structure-directing agent is sufficiently removed, and can be appropriately selected depending on the calcination temperature. Therefore, the time is preferably 0.5 hours or longer, more preferably 1 hour or longer, and even more preferably 3 hours or longer.
Since the crystallinity of zeolite tends to be maintained, the time is preferably 20 days or less, more preferably 10 days or less, and even more preferably 7 days or less.
The firing atmosphere is not particularly limited as long as it is a generally used atmosphere, but an air atmosphere, an atmosphere containing an inert gas such as nitrogen or argon, or an oxygen-added atmosphere is usually used.

<K-type GIS-type zeolite>
(X-ray diffraction peak)
A typical GIS-type zeolite has 2θ=12.45° and 33.0° in a spectrum obtained by X-ray diffraction, as described in ICDD (International Center for Diffraction Data) (for example, 00-039-0219). They have respective (1 0 1) and (3 1 2) diffraction peaks near 36°.
On the other hand, the GIS-type zeolite in the present embodiment has a (1 0 1) diffraction peak in the range of 2θ=12.55° to 12.90° in the spectrum obtained by X-ray diffraction. In addition, the GIS-type zeolite in the present embodiment preferably has a (3 1 2) diffraction peak in the range of 33.70° to 34.25° in the spectrum obtained by X-ray diffraction.
The (1 0 1) diffraction peak is diffraction reflecting the periodic structure of the dcc structure around the 8-membered ring structure of the GIS type zeolite. The diffraction peak of (1 0 1) in the GIS-type zeolite in the present embodiment is shifted to the high angle side, and it is considered that the periodic structure is short, and generally the lattice constant is reduced. This is a phenomenon seen in If the periodic structure is shortened, the pore size is also reduced, and it is expected that carbon dioxide will not be able to enter the pores and the amount of adsorption will be reduced. However, the GIS-type zeolite in the present embodiment can increase the amount of carbon dioxide adsorption by adjusting the crystal so that the (1 0 1) diffraction peak is observed in an appropriate range. In addition, the eight-membered ring structure of a general GIS-type zeolite is distorted, has an elliptical shape with a major axis of 4.5 Å and a minor axis of 3.1 Å, and carbon dioxide with an average molecular diameter of 3.3 Å. Molecules cannot easily enter the pores. However, it is thought that by optimally synthesizing and adjusting the crystal, the strain is relaxed and the pores become circular, making it easier for carbon dioxide to enter the pores, increasing the amount of adsorption. The optimum strain relaxation state is a state in which the (1 0 1) periodic structure is slightly shortened, and the X-ray diffraction peak at that time is 2θ=12.55° to 12.90°. From the same viewpoint as above, the 2θ value of the (1 0 1) diffraction peak is preferably 2θ = 12.58° to 12.85°, more preferably 2θ = 12.60° to 12.80. °. Other diffraction peaks are considered to have optimum peak positions in the same way, but the peak shift is remarkable, and from the viewpoint that they can be clearly distinguished without overlapping with other peaks, the diffraction peak other than (1 0 1) , (3 1 2) can also be used to determine whether the structure is optimal. The 2θ value of the diffraction peak of (3 1 2) is 33.70° to 34.25°, preferably 2θ=33.85° to 34.22°, still more preferably 2θ=34. 00° to 34.20°.
In K-exchanged GIS zeolite, as with GIS zeolite, the peak half width obtained by X-ray diffraction indicates the crystallinity and crystallite size of the crystal lattice plane where the diffraction occurs, and the narrower the crystal It is preferred because of its high resilience. On the other hand, if the half-value width is narrow, the crystallite size becomes larger, the size of the crystal becomes larger, the adsorption sites of gas molecules such as grain boundaries and crystal defects, and the pores through which gas molecules can easily diffuse are reduced. Since the surface area is reduced, the half width is preferably wide to some extent from the viewpoint of the amount of adsorption sites for gas molecules and the rate of gas adsorption and desorption. From these viewpoints, the half-value width of the peak in the XRD spectrum of the K-exchanged GIS-type zeolite is 0.08° or more and 0.55° or less, preferably 0 0.09° or more and 0.54° or less, more preferably 0.10° or more and 0.53° or less. The peak near 2θ=12.7° refers to the largest peak existing in the range of 12.55° to 12.90°.
The value of the diffraction angle 2θ and the half-value width of the diffraction peak can be measured by the method described in Examples below, and all of them are the composition ratio of the mixed gel, the aging time of the mixed gel, and the time of hydrothermal synthesis. conditions (heating temperature and heating time), the optimization of cations, etc. can be adjusted to the above range by a method of adjusting to a preferable range described later.

In the present embodiment, from the viewpoint of deforming the 8-membered ring elliptical structure of the K-exchanged GIS zeolite, the content of potassium atoms in the K-exchanged GIS zeolite is preferably 3% by mass or more, more preferably It is 3.3% by mass or more, more preferably 3.6% by mass or more. On the other hand, from the viewpoint of preventing the formation of impurities and the deterioration of the crystallinity of the K-exchanged GIS zeolite, the potassium atom content in the K-exchanged GIS zeolite is preferably 21% by mass or less, more preferably 18% by mass. % by mass or less, more preferably 16% by mass or less.
The content of potassium atoms can be measured by the method described in the examples below, and can be adjusted to the above range by a method for adjusting the composition ratio of the mixed gel to a preferable range described below.

[Cation exchange]
The K-exchanged GIS zeolite in this embodiment can be obtained by subjecting the GIS zeolite in this embodiment to cation exchange with potassium. Cation exchange can be carried out, for example, but not limited to, nitrates such as _KNO3 , or nitrate ions contained in said nitrates, for halide ions, sulfate ions, carbonate ions, bicarbonate ions, acetate ions, phosphate ions or phosphate ions. Salts modified into hydrogen ions and acids such as nitric acid and hydrochloric acid can be used.
The temperature for cation exchange is not particularly limited as long as it is a general cation exchange temperature, but it is usually from room temperature to 100°C or less.
When separating the zeolite after cation exchange, the separation method is not particularly limited as long as it is a general method, filtration, decantation, spray drying method (rotary atomization, nozzle atomization, ultrasonic atomization, etc.), rotary evaporator can be used, such as drying, vacuum drying, freeze-drying, or air-drying, and usually separation can be carried out by filtration or decantation.
The separated material may be used as it is or washed with water or a predetermined solvent. If desired, the separated material can be dried.
The temperature for drying the separated material is not particularly limited as long as it is a common drying temperature, but it is usually from room temperature to 150°C or less.
The atmosphere for drying is not particularly limited as long as it is a generally used atmosphere, but an air atmosphere, an inert gas such as nitrogen or argon, or an oxygen-added atmosphere is usually used.

<MWF-type zeolite>
[X-ray diffraction peak]
The peak half-value width obtained by X-ray diffraction indicates the crystallinity of the crystal lattice plane where the diffraction occurs, and is preferably narrower. Among them, the peak near 2θ = 11.1 ° in particular shows a higher-order structure such as an 8-membered ring structure, and represents the appropriate formation of pores. The narrow half-width is particularly important because it affects the molecular sieve effect due to molecular shielding. On the other hand, if the half-value width is narrow, the crystallite size becomes larger, the size of the crystal becomes larger, the adsorption sites of gas molecules such as grain boundaries and crystal defects, and the pores through which gas molecules can easily diffuse are reduced. Since the surface area is reduced, the half width is preferably wide to some extent from the viewpoint of the amount of adsorption sites for gas molecules and the rate of gas adsorption and desorption. Therefore, the half width of the peak near 2θ = 11.1° in the XRD spectrum of the MWF-type zeolite in the present embodiment is 0.06° or more and 0.31° or less, preferably 0.065° or more and 0.315°. ° or less, more preferably 0.07° or more and 0.30° or less.
The value of the peak half-value width can be adjusted to the above range by a method of adjusting the composition ratio of the mixed gel, the conditions (heating temperature and heating time) during hydrothermal synthesis, etc. to the preferable range described later. .

In the MWF-type zeolite of the present embodiment, in the peak obtained by X-ray diffraction, when the peak heights near 2θ = 11.1 and 13.8 ° are A and B, respectively, 0.61 ≤ B / A ≤ 0.83 is preferred.
Here, the X-ray diffraction pattern is obtained by irradiating the surface of zeolite uniformly fixed on a non-reflective sample plate for powder with X-rays from CuKα as a radiation source, with the scanning axis as θ/2θ.
The peak near 2θ=11.1° refers to the maximum peak existing in the range of 11.1°±0.1°.
The peak near 2θ=13.8° refers to the maximum peak existing in the range of 13.8°±0.2°.

Of the X-ray diffraction peaks at 25° C. of the MWF-type zeolite in the present embodiment, the peaks near 2θ=11.1 and 13.8° are the (4 4 0) and (5 5 0) diffraction peaks, respectively. . That is, these are diffractions by parallel crystal lattice planes, and when the heights of the (4 4 0) and (5 5 0) diffraction peaks are A and B, respectively, the higher the B/A, the finer the diffraction peak. structure is clear. That is, there are few defects in Si--O or Al--O bonds, the uniformity of bond distance and angle is high, and defects such as CH ₄ entering the crystal lattice and defects of CO ₂ adsorption sites are less likely to occur. Therefore, it is considered that the adsorption amount ratio of CO ₂ /CH ₄ can be maximized. From this point of view, B/A is preferably 0.61 or more, more preferably 0.63 or more, further preferably 0.635 or more, and even more preferably 0.64 or more. preferable.
On the other hand, a large value of peak height A indicates that a higher-order structure such as an eight-membered ring structure is clear, that is, fine structures are regularly arranged and pores are appropriately formed. It is thought that By properly forming the pore structure without defects, the molecular sieve effect of MWF-type zeolite works for gas molecules of different sizes, allowing CO ₂ to enter the pores, but making it difficult for CH ₄ to enter the pores. Therefore, it is considered that the adsorption amount ratio of CO ₂ /CH ₄ can be maximized. From this point of view, it is also important that the value of A is large, and B/A is preferably 0.83 or less, more preferably 0.80 or less, and even more preferably 0.79 or less. , 0.78 or less.
That is, in the range of B/A, the fine structure is clear, there are few defects in Si—O or Al—O bonds, defects in gas adsorption sites are unlikely to occur, and the higher-order structure is clear, and pores is formed appropriately, and is in the range of 0.61 to 0.83 from the viewpoint that the molecular sieve effect of MWF-type zeolite works.

In addition, the peak near 2θ = 51.6° is the diffraction peak of (18 18 0). On the other hand, for C/A, C is a high-angle reflection, and the measurement accuracy of the peak itself is high with respect to changes in the crystal lattice _. Although the CH ₄ selectivity is increased, the use of C/A provides higher accuracy, and from the viewpoint of further increasing the CO ₂ /CH ₄ adsorption amount ratio, the C / A is preferably 0.36 or more. 0.37 or more is more preferable, and 0.38 or more is even more preferable.
Regarding the relationship between the peak heights C and A, from the same viewpoint as above, C/A is preferably 0.52 or less, more preferably 0.50 or less, and 0.48 or less. is more preferred.
Here, the peak near 2θ=51.6° refers to the maximum peak existing in the range of 51.6°±0.4°.

In addition, the peak near 2θ=12.7° is the (5 4 1) diffraction peak, which is diffraction having reciprocal lattice vectors in three directions of the crystal axis. Therefore, if this peak height is D, D is sensitive to strain in three directions of the crystal axis. On the other hand, A reflects the number and crystallinity of long-period structures such as an 8-membered ring structure, so D / A represents the distortion of the crystal lattice in three directions for a long-period structure such as an 8-membered ring structure. It can be said that the higher the D/A, the less the distortion in the crystal lattice and the isotropic. The smaller the potential strain in the crystal lattice, the more the pore space is retained. It tends to be easily desorbed, and is suitable for use by desorbing and regenerating the adsorbed molecules when the gas is adsorbed in the pores of the zeolite and separated. D/A is preferably 0.75 or more, more preferably 0.78 or more, and even more preferably 0.80 or more.
Here, the peak near 2θ=12.7° refers to the maximum peak existing in the range of 12.7°±0.2°.

The above B/A and C/A values can be measured by the method described in the examples below, and both are determined by the composition ratio of the mixed gel, the conditions during hydrothermal synthesis (heating temperature and heating time ), etc. can be adjusted to the above range by a method for adjusting to a preferable range described later.

[Gas saturation adsorption amount]
The MWF-type zeolite in this embodiment can also be specified as follows. That is, the saturated adsorption amount of carbon dioxide of the MWF zeolite measured when the MWF zeolite and carbon dioxide are placed in a system at 25 ° C. and 760 mmHg is a (cm ³ /g), and the MWF zeolite and the value obtained by dividing a by b (a/b), where b (cm ³ /g) is the methane saturated adsorption amount of the MWF-type zeolite measured when methane is placed in a system at 25 ° C. and 760 mmHg. is 23 or more.
Moreover, the MWF-type zeolite in this embodiment can also be specified as follows. That is, the carbon dioxide saturated adsorption amount a of the MWF zeolite measured when the MWF zeolite and carbon dioxide are placed in a system at 25 ° C. and 760 mmHg is 10 cm ³ /g or more at 25 ° C. and 760 mmHg, and the MWF The methane saturated adsorption amount b of the MWF-type zeolite measured when the zeolite and methane are placed in a system at 25° C. and 760 mmHg is 3.5 cm ³ /g or less.
The MWF-type zeolite in the present embodiment has high purity and high carbon dioxide (CO ₂ ) adsorption selectivity, as suggested by these characteristics. That is, the MWF-type zeolite in the present embodiment has a high adsorption capacity for carbon dioxide (CO ₂ ), a low adsorption capacity for methane, and a saturated adsorption amount for carbon dioxide (CO ₂ ) and a saturated adsorption amount for methane (CH ₄ ). It can be said that the ratio of . As described above, the MWF-type zeolite in the present embodiment has a high purity and a high carbon dioxide (CO ₂ ) adsorption selectivity, so that the MWF-type zeolite has a large amount of gas components and a small amount of gas components adsorbed by the MWF-type zeolite. can be separated. That is, it can be suitably used for the purpose of separating gases by utilizing this difference in adsorption capacity.
Each of the above saturated adsorption amounts can be measured by the method described in the examples below. Further, the value of a/b can be adjusted to the above range, for example, by producing MWF-type zeolite based on the method for producing MWF-type zeolite described later. More specifically, by optimizing the components and composition of the mixed gel, the hydrothermal synthesis temperature, the firing temperature, etc., which will be described later, the crystals of the MWF-type skeleton are properly formed, the defects in the crystals are reduced, and the MWF It is presumed that the formation of zeolite having a skeleton different from the type skeleton is suppressed, the MWF type skeleton is maintained during calcination, etc. As a result, the value of a/b tends to increase. However, it is not limited to the mechanism of action described above. On the other hand, when the composition of the mixed gel is changed from the preferable range described later, or when a large amount of zeolite having a skeleton different from the MWF type skeleton is formed by raising the reaction temperature to a high temperature, the selectivity tends to decrease. .
Furthermore, each of the above saturated adsorption amounts a and b can also be adjusted within the above range, for example, by producing an MWF-type zeolite based on the method for producing an MWF-type zeolite, which will be described later. More specifically, when a zeolite with a larger pore size than the MWF-type framework and a different framework is formed, both the _CO2 saturated adsorption amount and the _CH4 saturated adsorption amount tend to increase. Moreover, when the pores are clogged, both the CO ₂ saturated adsorption amount and the CH ₄ saturated adsorption amount tend to decrease.

[Synthesis method]
The method for producing an MWF-type zeolite in the present embodiment includes a silica source containing silicon, an aluminum source containing aluminum, an alkali metal source containing at least one selected from alkali metals (M1) and alkaline earth metals (M2), and It includes a step of preparing a mixed gel containing water.
The mixed gel and each component contained therein will be described below.

[Preparation process of mixed gel]
The process for preparing the mixed gel is not particularly limited. and aging the mixture obtained in the step.
In the mixing step, these components including a silica source, an aluminum source, an alkali metal source, water, and, if necessary, an organic structure-directing agent can be mixed at once or in multiple steps.
The order of mixing in multiple stages is not limited, and may be appropriately selected depending on the conditions used. Mixing in multiple stages may be carried out either with stirring or without stirring, but a precursor that forms a gis structure, which is a constituent element of MWF-type zeolite and does not contain an organic structure-directing agent, is produced. From the point of view, it is preferable to use a mixed solution containing an alkali metal source, an aluminum source, and a silica source, and to have a stirring step and an aging step. When the aluminum source and silica source are mixed and aged, the temperature is preferably low from the viewpoint of suppressing excessive condensation reaction between Al and Si and achieving both precursor formation and uniform mixing. Specifically, the temperature in the mixing, stirring and aging steps is preferably 15°C or less. From the viewpoint of preventing excessive condensation reaction and sufficiently uniform mixing, the time for mixing, stirring and aging steps is preferably 10 minutes or more and 24 hours or less, more preferably 20 minutes or more and 12 hours or less, 30 minutes or more, Eight hours or less is most preferred.

From the viewpoint of promoting the formation of the MWF-type zeolite skeleton by forming precursors of the gis structure, which is the internal structure of the MWF-type zeolite, and surrounding them to form precursors of lta and pau structures containing an organic structure-directing agent. , an alkali metal source, an aluminum source, and a silica source are mixed first, and then the organic structure-directing agent is added to the mixed solution containing these sources. The temperature and time of the mixing, stirring, and aging processes of the mixed gel obtained by mixing the organic structure-directing agent with the alkali metal source, aluminum source, and silica source are set to 15°C or less from the viewpoint of preventing excessive condensation reaction and sufficiently uniform mixing. 10 minutes or more and 24 hours or less are preferable, 12° C. or less, 20 minutes or more and 12 hours or less are more preferable, and 10° C. or less and 45 minutes or more and 8 hours or less are most preferable. From the above, it is presumed that the fine structure and the long-period structure are properly formed and high crystallization is achieved, thereby optimizing the B/A and the half-value width and obtaining high CO ₂ selectivity.
The stirring is not particularly limited as long as it is a generally used stirring method, but specific examples include methods using blade stirring, vibration stirring, rocking stirring, centrifugal stirring, and the like.
The rotation speed for stirring is not particularly limited as long as it is a generally used stirring speed, and is, for example, 1 rpm or more and less than 2000 rpm.
The time of the mixing step is not particularly limited, and can be appropriately selected depending on the temperature of the mixing step.
From the standpoint of excellent economic efficiency, the faster the rate of addition of the raw materials in the mixing step, the higher the production efficiency. On the other hand, from the viewpoint of suppressing excessive condensation reaction between Al and Si and achieving both precursor formation and uniform mixing, a slow addition rate is preferable. From these points of view, when preparing a mixed gel of about 100 cc, it is preferably 0.1 cc/min or more and 100 cc/min or less, more preferably 0.2 cc/min or more and 50 cc/min or less, and 0.1 cc/min or more and 100 cc/min or less. Most preferably, it is 5 cc/min or more and 10 cc/min or less.
The aging step may be carried out either by standing still or by stirring.
When stirring in the aging step, there is no particular limitation as long as it is a generally used stirring method, but specific examples include methods using blade stirring, vibration stirring, rocking stirring, centrifugal stirring, and the like. .
The rotation speed for stirring is not particularly limited as long as it is a generally used stirring speed, and is, for example, 1 rpm or more and less than 2000 rpm.

[Mixed gel]
The mixed gel in the present embodiment is a mixture containing a silica source, an aluminum source, an alkali metal source and water as essential components, preferably containing an organic structure directing agent.
The silica source means a component in the mixed gel that serves as a raw material for silicon contained in the zeolite produced from the mixed gel, and the aluminum source means a raw material for aluminum contained in the zeolite produced from the mixed gel. The alkali metal source refers to a component in the mixed gel that serves as a raw material for the alkali metal and/or alkaline earth metal contained in the zeolite produced from the mixed gel.

[Silica source]
The silica source is not particularly limited as long as it is commonly used, but specific examples include amorphous silica, colloidal silica, wet silica, dry silica, silica gel, sodium silicate, and amorphous aluminosilicate. gel, tetraethoxysilane (TEOS), trimethylethoxysilane, and the like. These compounds may be used singly or in combination. Here, the amorphous aluminosilicate gel serves as both a silica source and an aluminum source.
Among these, amorphous silica, colloidal silica, wet silica, dry silica, and silica gel are preferred because they tend to yield zeolite with a high degree of crystallinity. From the same point of view, colloidal silica, wet-process silica, and dry-process silica are more preferable.
Examples of colloidal silica include, but are not limited to, Ludox®, Syton®, Nalco®, Snowtex®.
Examples of wet-process silica include, but are not limited to, Hi-Sil (registered trademark), Ultrasil (registered trademark), Vulcasil (registered trademark), Santocel (registered trademark), Valron-Estersil (registered trademark), Tokusil ( registered trademark), Zeosil (registered trademark), Carplex (registered trademark), Mizukasil (registered trademark), Sylysia (registered trademark), Syloid (registered trademark), Gasil (registered trademark), Silcron (registered trademark), Nipgel (registered trademark ), and Nipsil®.
Examples of dry process silica include HDK (registered trademark), Aerosil (registered trademark), Reolosil (registered trademark), Cab-O-Sil (registered trademark), Fransil (registered trademark), and ArcSilica (registered trademark).

[Aluminum source]
The aluminum source is not particularly limited as long as it is commonly used, but specific examples include sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum acetate, aluminum hydroxide, aluminum oxide, aluminum chloride, and aluminum alkoxide. , metallic aluminum, amorphous aluminosilicate gel, and the like. These compounds may be used singly or in combination.
Among these, sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum acetate, aluminum hydroxide, aluminum chloride, and aluminum alkoxide are preferred because they tend to yield zeolite with a high degree of crystallinity. From the same point of view, sodium aluminate and aluminum hydroxide are more preferred, and sodium aluminate is even more preferred.

[Alkali metal source]
The type of alkali in the alkali metal source is not particularly limited, and any alkali metal and/or any alkaline earth metal compound can be used.
Alkali metal sources include, but are not limited to, alkali metal or alkaline earth metal hydroxides, bicarbonates, carbonates, acetates, sulfates, nitrates, and the like. These compounds may be used alone or in combination.
Li, Na, K, Rb, Cs, Ca, Mg, Sr, Ba and the like can be used as alkali metals and alkaline earth metals used as alkali metal sources. Na and K are preferable, and Na is more preferable, from the viewpoint of facilitating crystal formation of the MWF-type skeleton. Also, the alkali metals and alkaline earth metals used as the alkali metal source may be used singly or in combination.
Specifically, examples of alkali metal sources include, but are not limited to, sodium hydroxide, sodium acetate, sodium sulfate, sodium nitrate, sodium carbonate, sodium hydrogen carbonate, potassium hydroxide, potassium acetate, potassium sulfate, potassium nitrate. , potassium carbonate, potassium hydrogen carbonate, lithium hydroxide, lithium acetate, lithium sulfate, lithium nitrate, lithium carbonate, lithium hydrogen carbonate, rubidium hydroxide, rubidium acetate, rubidium sulfate, rubidium nitrate, rubidium carbonate, rubidium hydrogen carbonate, hydroxide Cesium, cesium acetate, cesium sulfate, cesium nitrate, cesium carbonate, cesium hydrogen carbonate, calcium hydroxide, calcium acetate, calcium sulfate, calcium nitrate, calcium carbonate, calcium hydrogen carbonate, magnesium hydroxide, magnesium acetate, magnesium sulfate, magnesium nitrate , magnesium carbonate, magnesium hydrogen carbonate, strontium hydroxide, strontium acetate, strontium sulfate, strontium nitrate, strontium carbonate, strontium hydrogen carbonate, barium hydroxide, barium acetate, barium sulfate, barium nitrate, barium carbonate, barium hydrogen carbonate, etc. be done.
Among these, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide, calcium hydroxide, magnesium hydroxide, strontium hydroxide and barium hydroxide are preferred, and sodium hydroxide, potassium hydroxide, Lithium hydroxide, rubidium hydroxide and cesium hydroxide are more preferred, and sodium hydroxide is even more preferred.

[Organic Structure Directing Agent]
The organic structure-directing agent in producing zeolite by hydrothermally synthesizing a mixed gel is a compound that promotes crystallization into a zeolite structure. In the crystallization of zeolite, an organic structure-directing agent can be used as necessary. It is preferable to synthesize using a mixed gel containing an organic structure directing agent in terms of easier crystal formation of the MWF-type skeleton and/or shorter synthesis time and excellent economic efficiency in producing zeolite. .
The organic structure-directing agent may be of any type as long as it can form a desired MWF-type zeolite. Further, the organic structure-directing agents may be used singly or in combination.
Examples of organic structure-directing agents include, but are not limited to, amines, quaternary ammonium salts, alcohols, ethers, amides, alkylureas, alkylthioureas, cyanoalkanes, containing nitrogen as a heteroatom. Alicyclic heterocyclic compounds can be used, preferably quaternary ammonium salts, more preferably tetraalkylammonium salts, and even more preferably tetraethylammonium salts.
Such salts are associated with anions. Representatives of such anions include, but are not limited to, halogen ions such as Cl ⁻ , Br ⁻ , I ⁻ , hydroxide ions, acetate ions, sulphate ions, nitrate ions, carbonate ions and carbonate ions. Contains hydrogen ions. Among these, halogen ions and hydroxide ions are preferred, and halogen ions are more preferred, from the viewpoint of facilitating crystal formation of the MWF-type skeleton.
[Composition ratio of mixed gel]
The ratio of the silica source and OH ^- in the mixed gel is represented by the molar ratio of OH ^- to SiO ₂ , that is, OH ^- /SiO ₂ (OH ^- is the alkali metal source and/or the hydroxide contained in the organic structure directing agent). ions). In order to synthesize the MWF-type zeolite in this embodiment, it is desirable to control the conditions for synthesizing the precursor oligomer.
Since the 8-membered ring structure is formed without defects, the molecular sieve effect is exhibited, and the CH ₄ adsorption amount is reduced. The intensity ratio of peak A derived from a higher-order structure such as an 8-membered ring structure is high. It is desirable to form higher-order structures. From these points of view, it is preferable to prevent re-dissolution of the grown zeolite, and in order to suppress dissolution, it is preferable that OH ^- is as small as possible.
On the other hand, if there is a defect or distortion in the fine structure that constitutes the 8-membered ring or skeleton, that is, in the Si—O or Al—O bond, the number of CO ₂ adsorption sites may decrease, and the amount of CO ₂ adsorption may decrease. be. When such a fine structure is formed without defects or distortion, the peaks B and C, which are parallel to the plane belonging to the peak A and originate from finer structures, are relatively high. In order not to cause Si--O or Al--O defects and bond strain, it is preferable to dissolve more of the raw material silica source ^and aluminum source. preferable.
Therefore, the MWF-type zeolite, which has a large amount of CO ₂ adsorption and a small amount of CH ₄ adsorption, is limited to cases where B/A and C/A are within specific ranges. As a result of intensive studies by the inventors, the amount of OH ^- present in the synthesis liquid relative to SiO ₂ is such that if 0.10≦OH ^- /SiO ₂ ≦0.60, Si—O or Al—O It is possible to synthesize an MWF-type zeolite capable of achieving a specific ratio of B/A and C/A without causing defects or bond strain.
Within the above range, OH ⁻ /SiO ₂ is more preferably 0.15 or more, even more preferably 0.18 or more.
Within the above range, OH ^- /SiO ₂ is more preferably less than 0.40, more preferably 0.35 or less.
The ratio of silica source and aluminum source in _the mixed gel is expressed as the molar ratio of the oxides of the respective elements, ie _SiO2 / _Al2O3 .
The ratio of SiO ₂ /Al ₂ O ₃ is not particularly limited as long as the ratio is capable of forming zeolite, but is preferably 5.0 or more because the formation of zeolite having a skeleton different from the MWF type skeleton tends to be suppressed. , 6.0 or more. From the same point of view, it is more preferably 6.8 or more.
SiO ₂ /Al ₂ O ₃ is preferably 12 or less, more preferably 10 or less, since the formation of zeolite having a framework different from the MWF-type framework tends to be suppressed. From the same point of view, it is more preferably 7.8 or less.
The ratio of the aluminum source and the alkali metal source in the mixed gel is expressed as _{the additive molar ratio of M12O and M2O to Al2O3, that is, (M12O + M2O ) / Al2O3} (where M1 is an alkali metal and M2 represents an alkaline earth metal). This (M1 ₂ O+M2O)/Al ₂ O ₃ is preferably 1.3 or more, more preferably 1.5 or more, from the viewpoint of facilitating crystal formation of the MWF-type skeleton. From the same point of view, it is more preferably 1.7 or more.
(M1 ₂ O+M2O)/Al ₂ O ₃ is preferably 3.2 or less, more preferably 2.5 or less, from the viewpoint of suppressing the formation of zeolite having a framework different from the MWF-type framework. From the same point of view, it is more preferably 2.2 or less.
When the mixed gel contains _an organic structure directing agent, _the ratio of the aluminum source to the organic structure directing agent in the mixed gel is expressed as the molar ratio of organic structure directing agent to _Al2O3 , i.e., R/ _Al2O3 . (where R represents an organic structure directing agent). It is preferably 2.0 or more, and more preferably 3.0 or more, in terms of easier crystal formation of the MWF-type skeleton and/or shorter synthesis time and excellent economic efficiency in producing zeolite. preferable. From the viewpoint of suppressing the formation of zeolite having a skeleton different from the MWF-type skeleton, it is more preferably 4.0 or more.
R/Al ₂ O ₃ is preferably 50 or less, more preferably 30 or less, from the viewpoint of shortening the synthesis time and improving the economic efficiency in producing zeolite. From the viewpoint of suppressing the formation of zeolite having a skeleton different from the MWF-type skeleton, it is more preferably 20 or less.
_The ratio of aluminum source to water in the mixed gel is expressed as the molar ratio _of water to _Al2O3 , _H2O / _Al2O3 . It is preferably 100 or more, more preferably 200 or more, because the components in the mixed gel tend to be more uniformly dispersed. From the viewpoint of suppressing the formation of zeolite having a skeleton different from the MWF-type skeleton and producing an MWF-type zeolite with high crystallinity, it is more preferably 300 or more.
When the H ₂ O/Al ₂ O ₃ ratio is high, the crystallinity is improved, but the number of nuclei generated for crystal growth is reduced, and the crystallite size tends to increase and the particle size also tends to increase. Furthermore, since crystals during growth are less likely to come into contact with each other and be integrated, it is possible to grow a highly crystalline MWF with a small number of crystallites and few grain boundaries and crystal defects. High crystallinity clearly forms the eight-membered ring structure of MWF, which is important for improving carbon dioxide selectivity. It is also important to increase the adsorption capacity due to the presence of many carbon dioxide adsorption sites, and to increase the adsorption and desorption rate due to the presence of fast gas diffusion paths such as grain boundaries and defects in crystallites. . Therefore, if the crystallinity is too high, the performance as an adsorbent is lowered, so if the H ₂ O/Al ₂ O ₃ ratio is too high, it is not preferable. Furthermore, the lower the H ₂ O/Al ₂ O ₃ ratio, the shorter the synthesis time and the more economical the production of zeolite. From the above viewpoints, it is preferably less than 500, more preferably 490 or less, and even more preferably 485 or less.
As described above, in the method for producing an MWF-type zeolite in the present embodiment, a silica source containing silicon, an aluminum source containing aluminum, and at least one selected from alkali metals (M1) and alkaline earth metals (M2) are used. and water, wherein the molar ratio of each component in the mixed gel is determined with respect to the silicon, aluminum, alkali metal (M1) and alkaline earth metal (M2) When calculated as an oxide of each element, the molar ratios α, β, γ, δ represented by the following formulas (1), (2), (3) and (4) are 5.0 ≤ α ≤ 12 , 1.3≦β≦3.2, 100≦γ<500 and 0.10≦δ≦0.60. It is particularly preferable that the MWF-type zeolite in the present embodiment is obtained by the method for producing the MWF-type zeolite in the present embodiment described above.
α=SiO ₂ /Al ₂ O ₃ (1)
β=(M1 ₂ O+M2O)/Al ₂ O ₃ (2)
γ=H ₂ O/Al ₂ O ₃ (3)
δ=OH ⁻ /SiO ₂ (4)
Furthermore, in the method for producing MWF-type zeolite in the present embodiment, the molar ratios α, β, γ, and δ satisfy the above ranges, the mixed gel further contains an organic structure directing agent R, and the following formula (5 ) more preferably satisfies 2.0≦ε≦50.
ε=R/Al ₂ O ₃ (5)
Although seed crystals do not necessarily exist in the mixed gel, MWF-type zeolite according to the present embodiment can also be obtained by adding previously produced MWF-type zeolite as seed crystals to the mixed gel.

[Hydrothermal synthesis step]
The method for producing MWF-type zeolite in the present embodiment preferably further includes a hydrothermal synthesis step in which the hydrothermal synthesis temperature is 100°C to 170°C. That is, preferably, the mixed gel obtained in the preparation step is hydrothermally synthesized by holding the mixed gel at a predetermined temperature for a predetermined time while stirring or standing still.
The temperature of the hydrothermal synthesis is not particularly limited as long as it is a commonly used temperature, but it is preferably 100° C. or higher from the viewpoint of shortening the synthesis time and improving the economic efficiency of zeolite production. From the viewpoint of suppressing the formation of zeolite having a skeleton different from the MWF-type skeleton, the temperature is more preferably 110° C. or higher, and even more preferably 115° C. or higher.
The temperature is preferably 170° C. or lower because it tends to suppress the decomposition of the organic structure-directing agent. From the viewpoint of suppressing the formation of zeolite having a skeleton different from the MWF-type skeleton, the temperature is more preferably 155° C. or lower, and even more preferably 145° C. or lower.
The temperature for hydrothermal synthesis may be constant or may be changed stepwise.
The hydrothermal synthesis time is not particularly limited as long as it is a generally used time, and can be appropriately selected depending on the hydrothermal synthesis temperature.
The hydrothermal synthesis time is preferably 3 hours or longer, more preferably 10 hours or longer, in order to form the MWF skeleton. It is more preferably 24 hours or more from the viewpoint of increasing the yield of MWF-type zeolite and being excellent in economic efficiency.
It is preferably 30 days or less, more preferably 20 days or less, because it tends to suppress the decomposition of the organic structure-directing agent. From the viewpoint of suppressing the formation of zeolite having a skeleton different from the MWF-type skeleton, it is more preferably 10 days or less.
In the hydrothermal synthesis step, the container in which the mixed gel is placed is not particularly limited as long as it is a commonly used container. In that case, it is preferable to put it in a pressure vessel and perform hydrothermal synthesis.
The pressure-resistant container is not particularly limited, and various shapes such as a spherical shape, a vertically long shape, and a horizontally long shape can be used.
When stirring the mixed gel in the pressure container, the pressure container is rotated vertically and/or horizontally, preferably vertically.
When rotating the pressure container in the vertical direction, the rotation speed is not particularly limited as long as it is within the range generally used, but is preferably 1 to 50 rpm, more preferably 10 to 40 rpm.
In the hydrothermal synthesis step, in order to preferably stir the mixed gel, there is a method of using a vertically long pressure vessel and rotating it vertically.

[Separation/drying process]
After the hydrothermal synthesis step, the product solid and liquid containing water are separated, but the separation method is not particularly limited as long as it is a general method, and filtration, decantation, spray drying (rotary spray, Nozzle spraying, ultrasonic spraying, etc.), a drying method using a rotary evaporator, a vacuum drying method, a freeze-drying method, a natural drying method, or the like can be used, and the separation can be usually performed by filtration or decantation.
The separated material may be used as it is or washed with water or a predetermined solvent. If desired, the separated material can be dried.
The temperature for drying the separated material is not particularly limited as long as it is a common drying temperature, but it is usually from room temperature to 150°C or less.
The atmosphere for drying is not particularly limited as long as it is a generally used atmosphere, but an air atmosphere, an inert gas such as nitrogen or argon, or an oxygen-added atmosphere is usually used.

[Baking process]
If necessary, the MWF-type zeolite can be calcined and used. The firing temperature is not particularly limited as long as it is a temperature generally used, but when the organic structure-directing agent is desired to be removed, the remaining ratio can be reduced. is more preferable. A temperature of 400° C. or higher is more preferable from the viewpoint of shortening the calcination time and being excellent in economic efficiency in producing zeolite.
Since the crystallinity of zeolite tends to be maintained, the temperature is preferably less than 550°C, more preferably 530°C or less, and even more preferably 500°C or less.
The calcination time is not particularly limited as long as the organic structure-directing agent is sufficiently removed, and can be appropriately selected depending on the calcination temperature. Therefore, the time is preferably 0.5 hours or longer, more preferably 1 hour or longer, and even more preferably 3 hours or longer.
Since the crystallinity of zeolite tends to be maintained, the time is preferably 20 days or less, more preferably 10 days or less, and even more preferably 7 days or less.
The firing atmosphere is not particularly limited as long as it is a generally used atmosphere, but an air atmosphere, an atmosphere containing an inert gas such as nitrogen or argon, or an oxygen-added atmosphere is usually used.

[Cation exchange]
If desired, the MWF-type zeolite can be cation-exchanged to the desired cation form. Cation exchange includes, but is not limited to, _NH4NO3 , _LiNO3 , _NaNO3 , _KNO3 , _RbNO3 , _CsNO3 , Be _{( NO3} ) ₂ , Ca( _NO3 ) ₂ , Mg( _NO3 ) ₂ , Sr(NO ₃ ) ₂ , Ba(NO ₃ ) ₂ and other nitrates, or the nitrate ions contained in the nitrates are halide ions, sulfate ions, carbonate ions, bicarbonate ions, acetate ions, phosphate ions, phosphorus Salts that are oxyhydrogen ions and acids such as nitric acid and hydrochloric acid can be used.
The temperature for cation exchange is not particularly limited as long as it is a general cation exchange temperature, but it is usually from room temperature to 100°C or less.
When separating the zeolite after cation exchange, the separation method is not particularly limited as long as it is a general method, filtration, decantation, spray drying method (rotary atomization, nozzle atomization, ultrasonic atomization, etc.), rotary evaporator can be used, such as drying, vacuum drying, freeze-drying, or air-drying, and usually separation can be carried out by filtration or decantation.
The separated material may be used as it is or washed with water or a predetermined solvent. If desired, the separated material can be dried.
The temperature for drying the separated material is not particularly limited as long as it is a common drying temperature, but it is usually from room temperature to 150°C or less.
The atmosphere for drying is not particularly limited as long as it is a generally used atmosphere, but an air atmosphere, an inert gas such as nitrogen or argon, or an oxygen-added atmosphere is usually used.
Furthermore, ammonium-type zeolite can also be converted into proton-type zeolite by calcining the zeolite.

<Molding method of adsorbent>
Since GIS-type zeolite, K-type GIS-type zeolite, and MWF-type zeolite are obtained in the form of powder, they are preferably molded and used as adsorbents. Molding the zeolite in this embodiment facilitates the work of filling and replacing the adsorbent, and by making it an appropriate shape, the diffusivity of the gas is improved, and carbon dioxide is adsorbed more efficiently. be able to.
The molding method is not particularly limited, but examples include a method of compression molding a powder, a method of mixing with a binder and extrusion molding, and a method of mixing with a binder or a solvent and applying to a support.
In the compression molding method, the zeolite to be molded is placed in a mold of an appropriate size, molded by applying a pressure of about 40 kgN/cm ² , and the crushed product is sieved to a uniform size.
In the case of extrusion molding, a method of pre-mixing with a binder and then extrusion molding may be used. As the binder, silica, alumina, mullite, kaolin, carbon and organic matter can be appropriately mixed and used. In addition, carbon fiber, cellulose, etc. can also be used. Since cellulose has a hydroxyl group, it has good adhesion to zeolite, and since it is fibrous, it can increase the diffusion of gas inside the molded body. The shape of the extruded body is not particularly limited, but may be rod-shaped, bale-shaped, hollow, honeycomb-shaped, or the like. In the case of a rod or bale shape, it is obtained by continuous extrusion with a diameter of about 1 to 5 mm and cutting into lengths of about 2 to 20 mm. In the case of a bale shape, it may be tablet-molded. A hollow or honeycomb shape can also be molded in the same way as a rod shape by changing the shape of the extrusion port.
In the case of coating on a support, zeolite, a binder and a solvent are appropriately mixed, the mixture is applied to the support by a method such as coating, spraying or dip coating, followed by drying to remove the solvent. Silica, alumina, mullite, kaolin, carbon, organic matter, carbon fiber, cellulose and the like can be used as the binder. As the support, a porous material obtained by sintering inorganic material particles such as silica, alumina, or mullite, an organic porous film using polyethylene, PET, or the like, a film or pulp made of carbon fiber, cellulose, or the like is used. Ordinary paper can also be used. When a film-like support is used, it can be packed into a container in the form of a roll or bundled with a spacer. By using the support to form these shapes, the gas diffusibility can be improved, and the gas adsorption efficiency can be improved. Furthermore, when a high thermal conductivity material is used for the support, it is possible to cool the adsorbent before gas adsorption and heat it during gas desorption in a short time. Efficiency can be increased when heat is exchanged.

<Gas adsorption device>
In carrying out the gas separation method of the present embodiment, it is sufficient that a specific gas can be separated by bringing the raw material gas to be separated into contact with the adsorbent, and various known gas adsorption apparatuses can be used. The configuration of the gas adsorption device is also not particularly limited, but the following devices can be exemplified.
FIG. 1 shows an example of a gas adsorption device used for PSA. The raw material gas containing carbon dioxide stored in the raw material tank 6 is subjected to dust removal, dehumidification, desulfurization, and denitrification through the refining means 1, and introduced into either one of the vessels 2a and 2b filled with adsorbent. When the pressure in the container increases to the same pressure as the source gas, the upstream valve is closed and the downstream valve is opened to remove residual gas. After the residual gas is removed, the pump 3 lowers the pressure of the raw material gas to desorb the carbon dioxide adsorbed by the adsorbent. By allowing carbon dioxide to be adsorbed by the adsorbent in a container that has not previously been adsorbed during desorption, the adsorption and desorption steps can be performed simultaneously, so that carbon dioxide can be adsorbed and recovered with high efficiency. Since the desorption step generally requires more time, it is also possible to increase the time efficiency by adding more vessels. A gas containing carbon dioxide obtained by desorption is recovered in the CO ₂ tank 4 . If it is desired to further increase the concentration of carbon dioxide in the recovered gas, the pump 5 may be used to raise the pressure and introduce the gas again into either one of the containers 2a and 2b to adsorb carbon dioxide, or may be mixed with the raw material gas. Adsorption may be performed by Since heat of adsorption is generated during adsorption and cooling occurs due to heat of vaporization during desorption, input energy can be reduced by connecting the container to a heat exchanger and transferring heat.
FIG. 2 shows an example of a gas adsorption device used for TSA. The raw material gas containing carbon dioxide stored in the raw material tank 16 is subjected to dust removal, dehumidification, desulfurization, and denitrification through the refining means 11, and introduced into either one of the vessels 12a and 12b filled with adsorbent. After gas introduction is completed, the upstream valve is closed and the downstream valve is opened to remove residual gas from which carbon dioxide has been removed. Next, the carbon dioxide recovered in the CO ₂ tank 14 is heated by the heater 15 and introduced into the container in which the carbon dioxide is adsorbed, and the adsorbent is heated to desorb and remove the carbon dioxide. The removed carbon dioxide is recovered in the CO ₂ tank 14 . After removing the carbon dioxide, the adsorbent is naturally cooled or cooled by the heat exchanger 13 or the like. By allowing the adsorbent in the other container to adsorb the carbon dioxide of the source gas containing carbon dioxide while cooling, the time efficiency can be improved. Furthermore, heat of adsorption is generated during adsorption, and cooling occurs due to heat of vaporization during desorption.
In addition to the above, the gas adsorption device used for PSA is not particularly limited, and for example, a gas adsorption device in which each configuration of the gas adsorption device illustrated in FIG. 1 and the gas adsorption device illustrated in FIG. 2 are appropriately combined can be used. can.
The operating conditions of the PSA, TSA, or PTSA gas adsorption apparatus are not particularly limited, and various known conditions can be employed to carry out the gas separation method of the present embodiment.

In the gas separation method of the present embodiment, the raw material gas to be separated is not particularly limited, but at least one selected from the group consisting of hydrocarbons, methane, nitrogen, carbon monoxide, hydrogen, helium and argon and carbon dioxide is preferably a mixed gas containing That is, it is preferable to separate carbon dioxide from the mixed gas.

EXAMPLES The present embodiment will be described in more detail below with examples and the like, but these are illustrative and the present embodiment is not limited to the following examples. A person skilled in the art can implement the present embodiment by adding various changes to the examples shown below, and such changes are included in the scope of the present invention as long as the predetermined requirements of the present embodiment are satisfied.

[Crystal structure analysis]
Crystal structure analysis was performed by the following procedure.
(1) The dried materials obtained in each of the examples and comparative examples were used as samples and pulverized in an agate mortar.
(2) The sample of (1) above was uniformly fixed on a non-reflective sample plate for powder, and crystal structure analysis was performed under the following conditions.
X-ray diffractometer (XRD): Rigaku powder X-ray diffractometer "RINT2500 type" (trade name)
X-ray source: Cu tube (40 kV, 200 mA)
Measurement temperature: 25°C
Measurement range: 5 to 60° (0.02°/step)
Measurement speed: 0.2°/min Slit width (scattering, divergence, light reception): 1°, 1°, 0.15 mm
(3) Data analysis is performed on the obtained X-ray diffraction spectrum using XRD data analysis software "PDXL2" (software name, manufactured by Rigaku) with the set value "α cut value" in the analysis software set to 3.00, The 2θ value of the peak and the height of the peak were measured. At this time, the peak height was set to 0 when no peak was detected.

[Gas adsorption separation performance evaluation]
FIG. 3 shows an adsorbent gas adsorption separation performance evaluation apparatus (apparatus compatible with any of PSA, TSA and PTSA methods). The raw material gas tank 25 was filled with raw material gas to be separated. The composition of this source gas was 10% by weight CO ₂ and 90% by weight N ₂ . The flow rate of the raw material gas was adjusted by a mass flow controller 21, and the raw material gas was circulated through a container 22 filled with an adsorbent and placed in a constant temperature bath 26. The container 22 was filled with an adsorbent so that the adsorbent produced in Examples or Comparative Examples, which will be described later, and the raw material gas were in contact with each other. The gas separated and purified by the adsorbent passes through a flowmeter 23 and is subjected to composition analysis by GC-MS (mass spectrometry) 24, and the amount of adsorbed gas is calculated from the difference from the source gas. The adsorbent was kept at 250° C. for 12 hours or more in a constant temperature bath before adsorption to desorb the adsorbed water and gas molecules, and then the adsorption amount was measured. As an evaluation of the adsorption performance, the speed of adsorption is evaluated from the time (breakthrough time) when the CO ₂ concentration of the gas after gas adsorption and separation becomes 1% or less, and until the CO ₂ concentration becomes 1% or more again. The amount of CO ₂ adsorbed by the adsorbent was calculated from the time and flow rate, and the adsorption capacity was evaluated.

[Example 1]
155.48 g of water, 8.78 g of sodium hydroxide (NaOH, manufactured by Wako Pure Chemical Industries, Ltd.), 16.4 g of sodium aluminate (NaAlO ₂ , manufactured by Wako Pure Chemical Industries, Ltd.) and water glass No. 3 (Kishida Chemical) A mixed gel was prepared by mixing 248.3 g of the product) and stirring for 18 minutes. The composition of the mixed gel is α=SiO ₂ /Al ₂ O ₃ =12.0, β=Na ₂ O/Al ₂ O ₃ =4.0, γ=P ₂ O ₅ /Al ₂ O ₃ =0.0. , δ=H ₂ O/Al ₂ O ₃ =150, and ε=R/Al ₂ O ₃ =0.0. The mixed gel is charged into a 1000 mL stainless steel autoclave containing a fluororesin inner cylinder, hydrothermally synthesized at 130 ° C. for 6 days without stirring, the product is filtered and dried at 120 ° C., and powdered zeolite is obtained. rice field.
The XRD of the obtained zeolite was measured, and it was found from the obtained spectrum that GIS type zeolite was produced. The spectrum had a peak at 12.42° with a half-width of 0.42°. Further, when the peak heights near 2θ=12.4 and 21.6° were defined as A and B, respectively, A/B was 1.77.
10 wt % of γ-alumina was mixed with the obtained GIS-type zeolite, and the mixture was molded into tablets of 3 mm in diameter and 2 mm in height. The adsorbent was obtained by heating and sintering the compact at 335° C. for 4 hours.
Put 10 g of the adsorbent in a SUS container of a gas adsorption and separation performance evaluation device, desorb water and adsorbed molecules, and then flow the raw material gas at ₁₀₀ cc / min. was 15 seconds. The amount of CO ₂ adsorbed until the CO ₂ concentration of the treated gas reached 1% by mass or more was 400 cc.

[Example 2]
Same as Example 1 except that 1554.8 g of water was used, δ=H ₂ O/Al ₂ O ₃ =1500, the gel mixing time was stirred for 60 minutes, and the hydrothermal synthesis time was 135° C. for 10 days. to obtain a powdery zeolite.
The XRD of the obtained zeolite was measured, and it was found from the obtained spectrum that GIS type zeolite was produced. The spectrum had a peak at 12.42° with a half-width of 0.07°. Further, when the peak heights near 2θ=12.4 and 21.6° were set to A and B, respectively, A/B was 1.79.
An adsorbent was prepared in the same manner as in Example 1, and gas adsorption and separation performance was evaluated in the same manner as in Example 1. The time taken for the CO ₂ concentration of the treated gas to become 1% by mass or less after circulation was 19%. was seconds. The amount of CO ₂ adsorbed until the CO ₂ concentration of the treated gas reached 1% by mass or more was 380 cc.

[Comparative Example 1]
Same as Example 1 except that water was 98.47 g, δ=H ₂ O/Al ₂ O ₃ =95, the gel mixing time was stirred for 180 minutes, and the hydrothermal synthesis time was 115° C. for 1 day. to obtain a powdery zeolite.
The XRD of the obtained zeolite was measured, and it was found from the obtained spectrum that GIS type zeolite was produced. The spectrum had a peak at 12.42° with a half-width of 0.51°. Further, when the peak heights near 2θ=12.4 and 21.6° were set to A and B, respectively, A/B was 1.55.
An adsorbent was prepared in the same manner as in Example 1, and the gas adsorption and separation performance was evaluated in the same manner as in Example 1. The time taken for the CO _{concentration} of the treated gas to become 1% by mass or less after circulation was 30%. was seconds. The amount of CO ₂ adsorbed until the CO ₂ concentration of the treated gas reached 1% by mass or more was 190 cc.

[Comparative Example 2]
Same as Example 1 except that water was 2073.07 g, δ=H ₂ O/Al ₂ O ₃ =2000, the gel mixing time was stirred for 180 minutes, and the hydrothermal synthesis time was 110° C. for 18 days. to obtain a powdery zeolite.
The XRD of the obtained zeolite was measured, and it was found from the obtained spectrum that GIS type zeolite was produced. The spectrum had a peak at 12.42° with a half-width of 0.04°. Further, when the peak heights near 2θ=12.4 and 21.6° were set to A and B, respectively, A/B was 1.88.
An adsorbent was prepared in the same manner as in Example 1, and gas adsorption and separation performance was evaluated in the same manner as in Example 1. The time taken for the CO _{concentration} of the treated gas to become 1% by mass or less after circulation was 35%. was seconds. The amount of CO ₂ adsorbed until the CO ₂ concentration of the treated gas reached 1% by mass or more was 220 cc.

[Example 3]
194.33 g of water, 0.98 g of sodium hydroxide (NaOH, manufactured by Wako Pure Chemical Industries, Ltd.), 20.50 g of sodium aluminate (NaAlO ₂ , manufactured by Wako Pure Chemical Industries, Ltd.) and water glass No. 3 (Kishida Chemical) A mixed gel was prepared by mixing 310.4 g of the product) and stirring for 25 minutes. The composition of the mixed gel is α=SiO ₂ /Al ₂ O ₃ =12.0, β=Na ₂ O/Al ₂ O ₃ =3.0, γ=P ₂ O ₅ /Al ₂ O ₃ =0.0. , δ=H ₂ O/Al ₂ O ₃ =150, and ε=R/Al ₂ O ₃ =0.0. The mixed gel is charged into a 1000 mL stainless steel autoclave containing a fluororesin inner cylinder, hydrothermally synthesized at 120 ° C. for 3 days without stirring, the product is filtered and dried at 120 ° C., and powdered zeolite is obtained. rice field.
10 g of the obtained zeolite was added to 5000 mL of a 0.05 N potassium nitrate aqueous solution and stirred at 60° C. for 3 hours at 400 rpm. After filtering the product and drying at 120° C., a powdery zeolite with some of the cations exchanged for potassium was obtained.
The XRD of the obtained zeolite was measured, and it was found from the obtained spectrum that K-type GIS-type zeolite was produced. The spectrum had a peak at 12.71° with a half-width of 0.53°.
An adsorbent was prepared in the same manner as in Example 1, and the gas adsorption and separation performance was evaluated in the same manner as in Example 1. The time taken for the CO concentration of the treated gas to become ₁ % by mass or less after circulation was 13%. was seconds. The amount of CO ₂ adsorbed until the CO ₂ concentration of the treated gas reached 1% by mass or more was 420 cc.

[Example 4]
The same method as in Example 3 except that 1554.64 g of water was used, δ=H ₂ O/Al ₂ O ₃ =1200, the gel mixing time was 40 minutes, and the hydrothermal synthesis was performed without stirring at 125° C. for 10 days. to obtain a powdery zeolite.
10 g of the obtained zeolite was treated in the same manner as in Example 3 to obtain powdery zeolite in which a part of the cations were exchanged with potassium.
The XRD of the obtained zeolite was measured, and it was found from the obtained spectrum that K-type GIS-type zeolite was produced. The spectrum had a peak at 12.70° with a half-width of 0.10°.
An adsorbent was prepared in the same manner as in Example 1, and gas adsorption and separation performance was evaluated in the same manner as in Example 1. The time taken for the CO ₂ concentration of the treated gas to become 1% by mass or less after circulation was 18%. was seconds. The amount of CO ₂ adsorbed until the CO ₂ concentration of the treated gas reached 1% by mass or more was 405 cc.

[Comparative Example 3]
The same method as in Example 3 except that 98.46 g of water was used, δ=H ₂ O/Al ₂ O ₃ =95, the gel mixing time was 120 minutes, and the hydrothermal synthesis was performed without stirring at 110° C. for 1 day. to obtain a powdery zeolite.
10 g of the obtained zeolite was treated in the same manner as in Example 3 to obtain powdery zeolite in which a part of the cations were exchanged with potassium.
The XRD of the obtained zeolite was measured, and it was found from the obtained spectrum that K-type GIS-type zeolite was produced. The spectrum had a peak at 12.72° and a half-width of 0.57°.
An adsorbent was prepared in the same manner as in Example 1, and the gas adsorption and separation performance was evaluated in the same manner as in Example 1. It was found that the time required for the CO ₂ concentration of the treated gas to become 1% by mass or less after circulation was 31%. was seconds. The amount of CO ₂ adsorbed until the CO ₂ concentration of the treated gas reached 1% by mass or more was 205 cc.

[Comparative Example 4]
The same method as in Example 3 except that 2331.96 g of water was used, δ=H ₂ O/Al ₂ O ₃ =1800, gel mixing time was 180 minutes, and hydrothermal synthesis was performed without stirring at 110° C. for 18 days. to obtain a powdery zeolite.
10 g of the obtained zeolite was treated in the same manner as in Example 3 to obtain powdery zeolite in which a part of the cations were exchanged with potassium.
The XRD of the obtained zeolite was measured, and it was found from the obtained spectrum that K-type GIS-type zeolite was produced. The spectrum had a peak at 12.71° with a half-width of 0.05°.
An adsorbent was prepared in the same manner as in Example 1, and the gas adsorption and separation performance was evaluated in the same manner as in Example 1. The time taken for the CO _{concentration} of the treated gas to become 1% by mass or less after circulation was 35%. was seconds. The amount of CO ₂ adsorbed until the CO ₂ concentration of the treated gas reached 1% by mass or more was 210 cc.

[Example 5]
85.69 g of water, 2.73 g of sodium hydroxide (NaOH, manufactured by Wako Pure Chemical Industries, Ltd.), and 4.91 g of sodium aluminate (NaAlO ₂ , manufactured by Wako Pure Chemical Industries, Ltd.) are added and dissolved to form an aqueous solution. Obtained. While stirring this aqueous solution at 10° C., 32.01 g of colloidal silica (Ludox AS-40, manufactured by Grace) was added at a rate of 2 cc/min. After stirring this solution at 13° C. for 1 hour, 33.45 g of tetraethylammonium bromide (manufactured by Tokyo Kasei Kogyo Co., Ltd.) as an organic structure directing agent is added and mixed, and the mixed gel is obtained by stirring at 13° C. for 4 hours. prepared. The composition of the mixed gel is α=SiO ₂ /Al ₂ O ₃ =7.1, β=Na ₂ O/Al ₂ O ₃ =2.1, γ=H ₂ O/Al ₂ O ₃ =175, δ= OH ⁻ /SiO ₂ =0.32 and ε=R/Al ₂ O ₃ =5.3. The mixed gel is charged into a 200 mL stainless steel autoclave containing a fluororesin inner cylinder, hydrothermally synthesized at 125 ° C. for 4 days while maintaining a vertical stirring rotation speed of 40 rpm, the product is filtered and dried at 120 ° C., A powdery zeolite was obtained.
The XRD of the obtained zeolite was measured, and it was found from the obtained spectrum that K-type GIS-type zeolite was produced. The spectrum had a peak at 11.11° and a half width of 0.30°. Further, when the peak heights near 2θ=11.1 and 13.8° were set to A and B, respectively, B/A was 0.67.
An adsorbent was prepared in the same manner as in Example 1, and the gas adsorption and separation performance was evaluated in the same manner as in Example 1. The time taken for the CO _{concentration} of the treated gas to become 1% by mass or less after circulation was 16%. was seconds. The amount of CO ₂ adsorbed until the CO ₂ concentration of the treated gas reached 1% by mass or more was 380 cc.

[Example 6]
A powder was prepared in the same manner as in Example 5 except that 626.73 g of water was used, δ=H ₂ O/Al ₂ O ₃ =1280, the gel mixing time was 300 minutes, and the hydrothermal synthesis was 125° C. for 25 days. of zeolite was obtained.
The XRD of the obtained zeolite was measured, and it was found from the obtained spectrum that K-type GIS-type zeolite was produced. The spectrum had a peak at 11.11° and a half-width of 0.07°. Further, when the peak heights near 2θ=11.1 and 13.8° were set to A and B, respectively, B/A was 0.78.
An adsorbent was prepared in the same manner as in Example 1, and the gas adsorption and separation performance was evaluated in the same manner as in Example 1. The time taken for the CO _{concentration} of the treated gas to become 1% by mass or less after circulation was 19%. was seconds. The amount of CO ₂ adsorbed until the CO ₂ concentration of the treated gas reached 1% by mass or more was 385 cc.

[Comparative Example 5]
A powder was prepared in the same manner as in Example 5 except that 44.07 g of water was used, δ=H ₂ O/Al ₂ O ₃ =90, the gel mixing time was 240 minutes, and the hydrothermal synthesis was 135° C. for 1 day. of zeolite was obtained.
The XRD of the obtained zeolite was measured, and it was found from the obtained spectrum that K-type GIS-type zeolite was produced. The spectrum had a peak at 11.12° and a half width of 0.37°. Further, when the peak heights near 2θ=11.1 and 13.8° were set to A and B, respectively, B/A was 0.66.
An adsorbent was prepared in the same manner as in Example 1, and the gas adsorption and separation performance was evaluated in the same manner as in Example 1. The time taken for the CO _{concentration} of the treated gas to become 1% by mass or less after circulation was 38%. was seconds. The amount of CO ₂ adsorbed until the CO ₂ concentration of the treated gas reached 1% by mass or more was 195 cc.

[Comparative Example 6]
A powder was obtained in the same manner as in Example 5 except that 734.45 g of water was used, δ=H ₂ O/Al ₂ O ₃ =1500, the gel mixing time was 240 minutes, and the hydrothermal synthesis was 130° C. for 40 days. of zeolite was obtained.
The XRD of the obtained zeolite was measured, and it was found from the obtained spectrum that K-type GIS-type zeolite was produced. The spectrum had a peak at 11.11° and a half-width of 0.07°. Further, when the peak heights near 2θ=11.1 and 13.8° were defined as A and B, respectively, B/A was 0.80.
An adsorbent was prepared in the same manner as in Example 1, and the gas adsorption and separation performance was evaluated in the same manner as in Example 1. As a result, the time required for the CO concentration of the treated gas to become ₁ % by mass or less after circulation was 37%. was seconds. The amount of CO ₂ adsorbed until the CO ₂ concentration of the treated gas reached 1% by mass or more was 190 cc.

According to the present invention, there is provided a gas separation method by PSA, TSA or PTSA, which uses GIS type zeolite, K-exchanged GIS type zeolite or MWF type zeolite as an adsorbent and has sufficient adsorption capacity. be able to.

1 purification (dust removal, dehumidification, desulfurization, denitrification) means 2a, 2b container filled with adsorbent 3 pump 4 CO ₂ tank 5 pump 6 raw material tank 11 purification (dust removal, dehumidification, desulfurization, denitrification) means 12a, 12b adsorbent Filled vessel 13 Heat exchanger 14 _CO2 tank 15 Heater 16 Raw material tank 21 Mass flow controller 22 Vessel filled with adsorbent 23 Flow meter 24 GC-MS
25 raw material tank 26 constant temperature bath

Claims (2)

A method for separating gases by a temperature swing adsorption gas separation method, a pressure swing adsorption gas separation method, or a pressure/temperature swing adsorption desorption method using an adsorbent,
The adsorbent is
(i) The half width of the peak near 2θ = 12.4° in the XRD spectrum is 0.05° or more and 0.44° or less, and the peak height near 2θ = 12.4 and 21.6° GIS-type zeolite that satisfies 1.77 ≤ A / B ≤ 1.79, where A and B, respectively, and
(ii) K-exchanged GIS-type zeolite in which the half width of the peak near 2θ = 12.7° in the XRD spectrum is 0.08° or more and 0.55° or less
A gas separation method comprising at least one selected from the group consisting of 2. The gas of claim 1 , wherein carbon dioxide is separated from a mixed gas containing carbon dioxide and at least one selected from the group consisting of hydrocarbons, methane, nitrogen, carbon monoxide, hydrogen, helium and argon. Separation method.

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