WO2025018113A1 - Method for manufacturing gas adsorption base material, gas adsorption method, and gas adsorption base material - Google Patents

Abstract

Provided are: a method for manufacturing a gas adsorption base material capable of stably exhibiting adsorption performance with respect to volatile organic compounds and amines, more specifically, exhibiting constant adsorption performance; a gas adsorption method; and a gas adsorption base material. The method for manufacturing a gas adsorption base material includes a step of bringing a base material containing inorganic fibers, a zeolite, a pH adjuster, and a solvent into contact with each other. The pH is from 2 to 3 in the contact step. The base material is a molded body of the inorganic fibers and, in the contact step, the molded body may be brought into contact with slurry containing the zeolite, the pH adjuster, and the solvent.

Description

Manufacturing method of gas adsorption substrate, gas adsorption method and gas adsorption substrate

The present invention relates to a method for producing a gas adsorption substrate, a gas adsorption method, and a gas adsorption substrate.

Inorganic fibers are used to manufacture filter substrates because they have high heat resistance, high insulation, and non-flammability. Typically, inorganic fibers are formed into a sheet-like inorganic fiber sheet, which is processed by corrugating or other processes to form a honeycomb molded body, which is then fired to obtain the filter substrate. A technology has been proposed to manufacture honeycomb filters that are used for dehumidification, decomposition or removal of volatile organic compounds (VOCs), etc. by loading an adsorbent or catalyst onto the filter substrate (see, for example, Patent Publication No. 2925127).

Patent No. 2925127

Zeolite is widely used as an adsorbent supported on a substrate. However, it has recently been discovered that the adsorption performance of VOCs and amines, especially alcohol and ammonia, varies depending on the gas adsorption substrate on which zeolite is supported.

The present invention aims to provide a method for producing a gas adsorption substrate that can stably exhibit the adsorption performance of volatile organic compounds and amines, i.e., can exhibit a constant adsorption performance, a gas adsorption method, and a gas adsorption substrate.

The inventors conducted extensive research to solve the above problems and discovered that the above object could be achieved by adopting the following configuration, which led to the completion of the present invention.

In one embodiment, the present invention comprises:
A method for producing a gas adsorption substrate, comprising the steps of:
The method includes a step of contacting a substrate containing inorganic fibers with zeolite, a pH adjuster, and a solvent,
The present invention relates to a method for producing a gas adsorbing substrate, wherein the pH in the contact step is 2 or more and 3 or less.

According to the manufacturing method of the gas adsorption substrate, it is possible to efficiently manufacture a gas adsorption substrate capable of reducing the variation in the adsorption performance of VOCs and amines (hereinafter, both are also referred to as "VOCs, etc.") and stably exhibiting the adsorption performance. Although the reason for this is unclear, it is speculated as follows. As a result of examining the factors that destabilize the adsorption performance, the inventors came up with the idea that the cations that constitute the zeolite may have an effect. When the cation of the zeolite is a proton (hydrogen ion), VOCs such as alcohol and amines are adsorbed relatively firmly to the zeolite by hydrogen bonding. In contrast, the inventors closely examined a gas adsorption substrate with destabilized adsorption performance and found that the cations were exchanged from protons to sodium ions. The sodium ions are thought to be generated from the substrate, inorganic adhesive, adsorbent, etc. It is speculated that such cation exchange occurs during the manufacturing process of the gas adsorption substrate, and as a result of the hydrogen bonding ability of the zeolite with VOCs, etc. being reduced, the adsorption performance of the gas adsorption substrate becomes unstable. In the method for producing the gas adsorption substrate, the pH in the contact step (support step) between the substrate and zeolite is set to a low pH range of 2 to 3 to increase the hydrogen ion concentration in the contact environment, suppressing the exchange of protons in the zeolite for sodium ions, and producing a gas adsorption substrate supported by zeolite with a relatively large amount of protons. As a result, the resulting gas adsorption substrate can stably exhibit the adsorption performance of VOCs, etc.

In one embodiment, the substrate is a molded body of the inorganic fiber,
In the contacting step, the formed body may be contacted with a slurry containing the zeolite, the pH adjuster, and the solvent.

In one embodiment, the contact may be by immersion or application.

In one embodiment, the manufacturing method may further include a step of forming the mixture obtained in the contacting step to obtain a molded body.

In one embodiment, the pH adjuster is preferably an inorganic acid. In particular, the pH adjuster is preferably nitric acid. By using the above-mentioned component as a pH adjuster, a predetermined hydrogen ion concentration can be efficiently obtained in the contact environment, and damage to the firing furnace and surrounding components during firing of the base material can be reduced.

In one embodiment, the zeolite is preferably a proton-type zeolite. In addition to suppressing salt exchange from protons to sodium ions by adjusting the pH, the use of a proton-type zeolite in which the cation is a proton as the slurry raw material can achieve a higher level of proton retention in the zeolite.

In one embodiment, it is preferable to use a binder in the contact step. This allows the zeolite to be more firmly supported on the substrate, stabilizing the adsorption performance of the gas adsorption substrate.

In one embodiment, the binder is preferably colloidal silica in terms of heat resistance, adhesion, and sodium ion reduction.

In one embodiment, the sodium ion concentration in the contact step is preferably 4000 ppm or less. By reducing the sodium ion concentration outside the zeolite, salt exchange in the zeolite can be suppressed and the proton abundance rate can be increased, which in turn allows the gas adsorption substrate to stably exhibit its adsorption performance.

In one embodiment, the content of Na ₂ O in the zeolite after the contact step is preferably 0.10 mass% or less, which can reduce the amount of sodium ions in the zeolite, in other words, can maintain the amount of protons, thereby stabilizing the adsorption performance of the gas adsorption substrate at a high level.

In one embodiment, in terms of the gas adsorption and desorption performance of the gas adsorption substrate, it is preferable that the formed body is a honeycomb structure.

In one embodiment, the gas adsorption substrate is suitable for adsorbing alcohol or amines.

In one embodiment, the present invention comprises:
adsorbing an object to be adsorbed by the gas adsorption substrate manufactured by the method for manufacturing a gas adsorption substrate.

In this gas adsorption method, the exchange of protons in the zeolite with sodium ions is suppressed, and the substance to be adsorbed is adsorbed using a gas adsorption substrate that supports zeolite with a relatively large amount of protons, allowing for efficient gas adsorption.

In one embodiment, the substance to be adsorbed is preferably an alcohol or an amine.

In one embodiment, the present invention comprises:
The present invention comprises a substrate containing inorganic fibers and zeolite supported on the substrate,
The present invention relates to a gas adsorbing substrate having an alcohol adsorption amount of 20.0 mg/g or more according to the following alcohol adsorption test.
(Alcohol adsorption test)
Alcohol is adsorbed on the gas adsorption base material packed in a glass column under the following conditions: alcohol concentration: 100 ppm; carrier gas: air; temperature: 25° C.; humidity: 65% RH; air volume: 0.0045 m ³ /min, and the alcohol concentration at the inlet (inlet concentration) and the alcohol concentration at the outlet (outlet concentration) of the column are measured. The adsorption test is carried out until the outlet concentration reaches the inlet concentration (100 ppm). In a chart plotting the alcohol concentration (mg/m ³ ) against the elapsed time t (min), the adsorption amount (mg) of the part surrounded by the inlet concentration and the outlet concentration in the section from the start of the adsorption test (0 min) to the outlet concentration reaching the inlet concentration (100 ppm) is integrated to obtain the alcohol adsorption amount (mg).

This gas adsorption substrate exhibits excellent alcohol adsorption performance over time, making it suitable as an adsorption substrate for gas adsorption systems.

In one embodiment, the alcohol is preferably ethanol.

In one embodiment, the present invention comprises:
The present invention comprises a substrate containing inorganic fibers and zeolite supported on the substrate,
The gas adsorption substrate has an amine adsorption amount of 2.0 mg/g or more according to the following amine adsorption test.
(Amine Adsorption Test)
Amine is adsorbed on the gas adsorption base material packed in a glass column under the following conditions: amine concentration: 100 ppm; carrier gas: air; temperature: 25° C.; humidity: 50% RH; air volume: 0.0045 m ³ /min, and the amine concentration at the inlet (inlet concentration) and the amine concentration at the outlet (outlet concentration) of the column are measured. The adsorption test is carried out until the outlet concentration reaches the inlet concentration (100 ppm). In a chart plotting the amine concentration (mg/m ³ ) against the elapsed time t (min), the adsorption amount (mg) of the part surrounded by the inlet concentration and the outlet concentration in the section from the start of the adsorption test (0 min) to the time when the outlet concentration reaches the inlet concentration (100 ppm) is integrated to obtain the amine adsorption amount (mg).

This gas adsorption substrate exhibits excellent amine adsorption performance over time, making it suitable as an adsorption substrate for gas adsorption systems.

In one embodiment, the amine is preferably ammonia.

FIG. 1 is a perspective view showing a gas adsorbing substrate according to one embodiment of the present invention. 2 is an enlarged view of a portion A of an opening surface of the gas adsorbing substrate of FIG. 1. FIG. 4 is an explanatory diagram showing a method for calculating the amount of ethanol adsorption. 1 is a graph showing the amount of ethanol adsorbed per amount of supported zeolite in Examples and Comparative Examples. 1 is a graph showing the Na ₂ O content in zeolites of Examples and Comparative Examples. FIG. 4 is an explanatory diagram showing a method for calculating an ammonia adsorption amount. 1 is a graph showing the amount of ammonia adsorbed per amount of supported zeolite in Examples and Comparative Examples.

The manufacturing method of a gas adsorption substrate, the gas adsorption method, and the gas adsorption substrate according to one embodiment of the present invention will be described below with reference to the drawings. First, the obtained gas adsorption substrate will be described, and then each step of the manufacturing method and each step of the gas adsorption method will be described. The present invention is not limited to these embodiments. In some or all of the figures, parts that are not necessary for the explanation are omitted, and some parts are illustrated enlarged or reduced to facilitate the explanation. Terms indicating positional relationships such as up and down that are mentioned with reference to the drawings are used simply to facilitate the explanation, and are in no way intended to limit the configuration of the present invention.

<Gas adsorption substrate>
Fig. 1 is a perspective view showing a gas adsorbing substrate according to one embodiment of the present invention, Fig. 2 is an enlarged view of a portion A of an opening surface of the gas adsorbing substrate shown in Fig. 1.

As shown in FIG. 1, the gas adsorption substrate 1 is a honeycomb rotor that includes a substrate 8 containing inorganic fibers formed into the shape of the gas adsorption substrate 1, and zeolite as an adsorbent supported on the substrate 8. Generally, the honeycomb rotor is installed in a gas adsorption system (not shown). The gas adsorption system has a space partitioned into an adsorption zone that adsorbs substances to be adsorbed, such as VOCs, and a regeneration zone that desorbs the substances to be adsorbed, and adsorption and regeneration are repeated as the honeycomb rotor rotates in the gas adsorption system.

The gas adsorption substrate 1 has an internal ventilation cavity 4 formed parallel to the rotor shaft 3 for ventilating the air to be treated, regeneration air, and purged air. The gas adsorption substrate 1 has opening surfaces 2a, 2b at both ends. The opening surfaces 2a, 2b are the inlets and outlets for the air to be treated, regeneration air, and purged air. The rotor shaft 3 is attached to the center of the gas adsorption substrate 1, and is the rotation axis for rotating the gas adsorption substrate 1 in the rotation direction 7.

As shown in FIG. 2, the ventilation cavity 4 is formed by alternately stacking flat portions 5 and corrugated portions 6. The gas adsorption substrate 1 has a structure in which inorganic fiber sheets forming the flat portions 5 and inorganic fiber sheets forming the corrugated portions 6 are stacked in multiple layers in the radial direction and circumferentially from the rotor shaft 3.

The pitch p of the corrugated portion 6 shown in FIG. 2 is preferably 2.0 to 3.5 mm, more preferably 2.4 to 3.1 mm. The peak height t is preferably 0.8 to 2.0 mm, more preferably 1.3 to 1.7 mm. The pitch p refers to the distance between the peaks of adjacent waves of the corrugated portion 6, and the peak height t refers to the height of one wave of the corrugated portion 6. The thickness (axial length) s of the gas adsorption substrate 1 is preferably 200 to 500 mm, more preferably 300 to 450 mm. By having the pitch p, peak height t, and thickness s of the gas adsorption substrate 1 within the above ranges, the VOC adsorption performance can be improved.

The gas adsorption substrate 1 can be efficiently manufactured by the following manufacturing method. The gas adsorption substrate 1 obtained by this manufacturing method is suitable as a substrate for adsorbing alcohols and amines, since the exchange of protons in the zeolite with sodium ions is suppressed and zeolite with a relatively large amount of protons is supported. Examples of alcohols include lower alcohols with 1 to 5 carbon atoms, such as methanol, ethanol, and n-propanol. Examples of amines include ammonia, as well as primary amines to tertiary amines, such as monomethylamine, dimethylamine, trimethylamine, and triethylamine.

According to the gas adsorbing substrate of this embodiment, the alcohol adsorption amount in the alcohol adsorption test described below is 20.0 mg/g or more.
(Alcohol adsorption test)
Alcohol is adsorbed on the gas adsorption base material packed in a glass column under the following conditions: alcohol concentration: 100 ppm; carrier gas: air; temperature: 25° C.; humidity: 65% RH; air volume: 0.0045 m ³ /min, and the alcohol concentration at the inlet (inlet concentration) and the alcohol concentration at the outlet (outlet concentration) of the column are measured. The adsorption test is carried out until the outlet concentration reaches the inlet concentration (100 ppm). In a chart plotting the alcohol concentration (mg/m ³ ) against the elapsed time t (min), the adsorption amount (mg) of the part surrounded by the inlet concentration and the outlet concentration in the section from the start of the adsorption test (0 min) to the outlet concentration reaching the inlet concentration (100 ppm) is integrated to obtain the alcohol adsorption amount (mg).

This gas adsorption substrate exhibits excellent alcohol adsorption performance over time, making it suitable as an adsorption substrate for gas adsorption systems. Details of the alcohol adsorption test are described in the Examples.

The lower limit of the alcohol adsorption amount is preferably 20.5 mg/g, and more preferably 21.0 mg/g. The higher the upper limit of the alcohol adsorption amount, the better, but it may be 30.0 mg/g or 28.0 mg/g.

The alcohol can be any of the above-mentioned components that can be suitably adsorbed, but ethanol is preferred.

According to the gas adsorption substrate of this embodiment, the amine adsorption amount in the amine adsorption test described below is 2.0 mg/g or more.
(Amine Adsorption Test)
Amine is adsorbed on the gas adsorption base material packed in a glass column under the following conditions: amine concentration: 100 ppm; carrier gas: air; temperature: 25° C.; humidity: 50% RH; air volume: 0.0045 m ³ /min, and the amine concentration at the inlet (inlet concentration) and the amine concentration at the outlet (outlet concentration) of the column are measured. The adsorption test is carried out until the outlet concentration reaches the inlet concentration (100 ppm). In a chart plotting the amine concentration (mg/m ³ ) against the elapsed time t (min), the adsorption amount (mg) of the part surrounded by the inlet concentration and the outlet concentration in the section from the start of the adsorption test (0 min) to the time when the outlet concentration reaches the inlet concentration (100 ppm) is integrated to obtain the amine adsorption amount (mg).

This gas adsorption substrate exhibits excellent amine adsorption performance over time, making it suitable as an adsorption substrate for gas adsorption systems. Details of the amine adsorption test are described in the Examples.

The lower limit of the amine adsorption amount is preferably 2.1 mg/g, and more preferably 2.2 mg/g. The upper limit of the alcohol adsorption amount is preferably as high as possible, but may be 3.0 mg/g or 2.8 mg/g.

The amine can be any of the above-mentioned components, but ammonia is preferred.

<<Method for manufacturing gas adsorption substrate>>
The method for producing a gas adsorption substrate according to this embodiment includes a step of contacting a substrate containing inorganic fibers with zeolite, a pH adjuster, and a solvent. The substrate may be a molded body of inorganic fibers, or may be inorganic fibers themselves. The order and operation of the contact step and the molding step differ depending on the type of substrate. Each step will be described below for each type of substrate.

First Embodiment
In this embodiment, the substrate is an inorganic fiber molded body. In the contact step, the molded body is contacted with a slurry containing zeolite, a pH adjuster, and a solvent (hereinafter, also referred to as a "supporting slurry"). The contact is by immersion. That is, according to this embodiment, after forming an inorganic fiber molded body in the molding step, the molded body is immersed in the supporting slurry in the contact step to support zeolite on the substrate. After the contact step, a gas adsorption substrate can be manufactured by going through a drying step and a firing step.

(Molding process)
In the molding step, the inorganic fibers are molded to obtain a molded body. The molding step may be a single-stage or multi-stage process. The molding step also includes a process in which a plurality of molded bodies are combined to form a desired molded body. The molded body is preferably a honeycomb structure.

The honeycomb-structured substrate as shown in FIG. 1 is typically manufactured by laminating a porous flat inorganic fiber sheet and a corrugated inorganic fiber sheet obtained by corrugating the flat inorganic fiber sheet, bonding the peaks of the corrugated inorganic fiber sheet with an inorganic adhesive. At this time, the roughly semi-cylindrical cavity formed between the flat inorganic fiber sheet and the corrugated inorganic fiber sheet becomes an air passage, so the two are laminated so that the cavity is formed in a direction parallel to the rotor shaft 3.

Inorganic fiber sheets can be formed by known methods, for example, by wet-laid sheet material slurry containing inorganic fibers to produce a nonwoven fabric. The sheet material slurry generally contains water as a medium.

The inorganic fibers are not particularly limited, and examples thereof include glass fibers such as E glass fiber, NCR glass fiber, ARG fiber, ECG fiber, S glass fiber, and A glass fiber, as well as chopped strands thereof, ceramic fibers, alumina fibers, mullite fibers, silica fibers, rock wool fibers, and inorganic fibers such as carbon fibers.

Biosoluble inorganic fibers may be used as the inorganic fibers. Biosoluble inorganic fibers are fibers that do not fall under the category of "WHO respirable fibers" or fibers that satisfy any one of the following four conditions (1) to (4) according to the NotaQ "Biosoluble Fiber Judgment Criteria" of EU Directive 97/69/EC. Biosoluble inorganic fibers include biosoluble ceramics, biosoluble rock wool, and the like. "WHO respirable fibers" are fibrous substances defined by the World Health Organization (WHO) that are inhaled into the body by breathing and reach the lungs, and have a length of more than 5 μm, a diameter of less than 3 μm, and an aspect ratio of more than 3.
The four conditions are as follows:
(1) In short-term inhalation exposure animal experiments, the half-life of fibers longer than 20 μm was less than 10 days.
(2) In short-term intratracheal instillation animal experiments, the half-life of fibers longer than 20 μm was less than 40 days.
(3) No significant carcinogenicity has been shown in animal experiments involving intraperitoneal administration.
(4) In long-term inhalation exposure animal experiments, there have been no pathological findings or tumor formation associated with carcinogenicity (however, the composition contains more than 18 mass% alkali and alkaline earth oxides (Na ₂ O, K ₂ O, CaO, MgO, BaO)).

There are no particular restrictions on the fiber length of the inorganic fibers, but the length-weighted average fiber length of the inorganic fibers is preferably 1 to 20 mm, more preferably 2 to 10 mm, and particularly preferably 3 to 8 mm. There are no particular restrictions on the fiber diameter of the inorganic fibers, but the average value is preferably 3 to 20 μm, more preferably 4 to 18 μm, and particularly preferably 5 to 16 μm. By setting the fiber length and fiber diameter of the inorganic fibers within the above ranges, the strength and handleability of the inorganic fiber sheet can be improved. Inorganic fibers with different fiber lengths and fiber diameters may be used in combination.

The sheet raw material slurry may contain components other than inorganic fibers. Examples of other components include synthetic fibers, natural fibers, organic or inorganic binders, auxiliaries, additives, fillers, etc.

Wet papermaking can be carried out by preparing a sheet raw material slurry containing the above-mentioned components and water (medium), and then making paper from this sheet raw material slurry using a known papermaking machine. Examples of papermaking machines include cylinder papermaking machines, inclined papermaking machines, Fourdrinier papermaking machines, and short wire papermaking machines, and multi-layer papermaking can be carried out using the same or different types of papermaking machines in combination. There are no particular restrictions on the method of dehydration and drying after papermaking, and known dryers such as Yankee dryers, cylinder dryers, air dryers, and infrared dryers can be used. There are no particular restrictions on the drying temperature, and it is usually around 100°C to 180°C.

The thickness of the inorganic fiber sheet is not particularly limited, but is preferably 50 to 300 μm, more preferably 100 to 250 μm, and particularly preferably 100 to 200 μm. A thickness within the above range is preferable because it provides good corrugation properties. Furthermore, the thickness of the inorganic fiber sheet used for the flat inorganic fiber sheet may be the same as or different from that used for the corrugated inorganic fiber sheet.

Corrugated inorganic fiber sheets are obtained by corrugating a flat inorganic fiber sheet to give the sheet a corrugated cross section. One method of corrugating is, for example, passing a flat inorganic fiber sheet through a corrugated roll.

The honeycomb structure may have any shape, but may be, for example, a laminated structure in which flat inorganic fiber sheets and corrugated inorganic fiber sheets are alternately laminated in the thickness direction, or a rotor structure obtained by winding a composite sheet in which flat inorganic fiber sheets and the peaks on one side of a corrugated inorganic fiber sheet are bonded. The rotor structure may be formed by combining fan-shaped members obtained by dividing the honeycomb rotor into a fan shape in the radial direction. The fan-shaped members are obtained by alternately stacking flat inorganic fiber sheets and corrugated inorganic fiber sheets from the rotor shaft 3 toward the outer periphery, with the sheets on the outer periphery being slightly longer.

The adhesion between the flat inorganic fiber sheet and the corrugated inorganic fiber sheet during stacking or rolling is achieved, for example, by applying an adhesive to the peaks of the corrugated inorganic fiber sheet and stacking or rolling this and the flat inorganic fiber sheet. The adhesion between the sector-shaped members can be achieved by applying an adhesive to the surfaces of the sector-shaped members that correspond to the radius portions in a plan view and combining a plurality of sector-shaped members. Examples of adhesives include inorganic adhesives such as silica sol, alumina sol, silica-alumina sol, titania sol, and cement; and organic adhesives such as acrylic resin adhesives and vinyl acetate adhesives. Of these, inorganic adhesives are preferred because they do not contain organic components and have excellent heat resistance.

Depending on the size of the gas adsorption substrate 1, the contact step described below may be carried out on the fan-shaped member, and the gas adsorption substrate 1 may be manufactured by combining multiple fan-shaped members carrying zeolite.

If necessary, a drying step may be carried out to dry the molded body. There are no particular limitations on the drying method, and it may be natural drying or drying by heating. Heat drying may be carried out by applying hot air at 40 to 250°C, by placing the molded body in a dryer set to the above temperature range, or by a combination of both.

(Contacting step)
In the contact step, the molded body obtained in the molding step is contacted with a supporting slurry containing zeolite, a pH adjuster, and a solvent. Specifically, a supporting slurry containing predetermined components is prepared, and the molded body is immersed in the supporting slurry to perform the contact step.

As the zeolite, zeolites known as adsorbents can be suitably used. Specific examples include Y-type zeolite, USY-type zeolite, A-type zeolite, X-type zeolite, mordenite-type zeolite, ZSM-5-type zeolite, beta-type zeolite, ferrierite-type zeolite, L-type zeolite, etc. Zeolites can be used alone or in combination of multiple types.

The zeolite is preferably a proton-type zeolite having protons as cations. Since not all of the protons in the proton-type zeolite are salt-exchanged, the use of proton-type zeolite as the slurry raw material allows the proton retention effect in the zeolite to be exerted at a higher level.

The concentration of zeolite in the support slurry can be set appropriately taking into consideration the efficiency of the zeolite contacting (supporting) the substrate and the efficiency of the slurry impregnating the molded body. The zeolite concentration is preferably 10 to 50 mass%, more preferably 15 to 45 mass%, even more preferably 20 to 40 mass%, and particularly preferably 25 to 35 mass%.

The pH adjuster is not particularly limited as long as it can adjust the pH in the contact step to a predetermined range, and examples of the pH adjuster include inorganic acids, organic acids, and combinations thereof. Examples of inorganic acids include nitric acid, hydrochloric acid, and sulfuric acid. Examples of organic acids include sulfonic acids such as methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid. Among these, inorganic acids are preferred, and nitric acid is particularly preferred. The pH adjuster may be added directly or in the form of a diluted solution in an amount that will give the desired pH.

Water or various organic solvents can be used as the solvent, but water is preferred from the standpoints of safety, low environmental impact, and solubility/dispersibility.

It is preferable to have a binder present in the contact step. This allows the zeolite to be more firmly supported on the substrate, and promotes stabilization of the adsorption performance of the gas adsorption substrate. Examples of binders include inorganic binders, organic binders, and combinations thereof. Examples of inorganic binders include colloidal silica, water glass, calcium silicate, silica sol, alumina sol, titania sol, silica-alumina sol, and alkoxysilane. Examples of organic binders include thermoplastic resins such as polyethylene resin, vinyl chloride resin, (meth)acrylic acid ester resin, styrene-acrylic acid ester copolymer, vinyl acetate resin, vinyl acetate-(meth)acrylic acid ester copolymer, ethylene-vinyl acetate copolymer, polyester resin, polyvinyl alcohol (PVA), and ethylene-vinyl alcohol copolymer; rubber emulsions such as styrene-butadiene rubber (SBR) and nitrile rubber (NBR); and thermosetting resins such as phenolic resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, polyurethane resin, and thermosetting polyimide resin. Among these, inorganic binders are preferred, with colloidal silica being especially preferred.

The binder concentration in the support slurry is preferably 10 to 50 mass%, more preferably 15 to 45 mass%, and even more preferably 20 to 35 mass%.

Other components such as dispersants, liquid retaining agents, viscosity adjusters, and fillers may be added to the support slurry as necessary.

The above components are added to water as a solvent to reach a specified concentration, and the support slurry can be prepared by stirring and mixing.

The sodium ion concentration in the contact step is preferably 4000 ppm or less, more preferably 3500 ppm or less, even more preferably 3000 ppm or less, and particularly preferably 2500 ppm or less. By reducing the sodium ion concentration outside the zeolite, salt exchange in the zeolite can be suppressed and the proton abundance rate can be increased, which in turn allows the gas adsorption substrate to stably exhibit its adsorption performance.

The molded body is immersed in the prepared support slurry to bring the molded body into contact with the support slurry. The immersion time is not particularly limited and may be set appropriately taking into consideration the efficiency of supporting zeolite on the substrate. The immersion time is preferably 1 to 60 minutes, more preferably 3 to 30 minutes, and even more preferably 5 to 20 minutes.

The temperature of the contact step (the temperature of the slurry in this embodiment) is not particularly limited and can be set appropriately within the range of 15 to 40°C.

Next, it is preferable to carry out a drying step to dry the molded body. Although there are no particular limitations on the drying method, drying by heating is preferable. Heat drying can be carried out by applying hot air at 40 to 250°C, by placing the molded body in a dryer set to the above temperature range, or by combining both.

The Na ₂ O content in the zeolite after the contact step is preferably 0.10 mass % or less, preferably 0.03 mass % or less, and more preferably 0.01 mass % or less.

After the drying process, a firing process is carried out to fire the molded body, thereby producing the gas adsorption substrate according to this embodiment. The firing temperature is preferably 300 to 800°C, and the firing time is preferably 0.5 to 12 hours.

The zeolite content in the gas adsorption substrate 1 is preferably 20 to 200 g/L in terms of gas adsorption performance, breathability, etc.

Second Embodiment
In this embodiment, the substrate is an inorganic fiber molded body. In the contact step, the molded body is contacted with a supporting slurry containing zeolite, a pH adjuster, and a solvent. The contact is by application. That is, according to this embodiment, after forming an inorganic fiber molded body in the molding step, the supporting slurry is applied to the molded body in the contact step to support zeolite on the substrate. The following mainly describes the differences from the first embodiment.

(Molding process)
The formed body obtained in the forming step may be a sheet structure or a honeycomb structure. Considering the ease of application and the impregnation efficiency of the supporting slurry, the formed body preferably has a sheet structure. When the formed body is an inorganic fiber sheet having a sheet structure, it is preferable to provide a lamination step in which flat and corrugated inorganic fiber sheets are laminated to form a honeycomb structure after the contact step described below.

(Contacting step)
Examples of the method for applying the slurry to the molded body include spray coating, curtain coating, impregnation coating, bar coating, roll coating, blade coating, etc. The amount of coating may be adjusted so that the content of zeolite in the final gas adsorption substrate is the desired amount. The number of coatings is not particularly limited, and may be one or more than two coatings.

Then, a drying step and a firing step are performed to produce a gas adsorption substrate. If the molded body has a sheet structure, it is preferable to provide a lamination step between the drying step and the firing step.

Third Embodiment
In this embodiment, the substrate is the inorganic fiber itself. In the contact step, the inorganic fiber as the substrate is contacted with a supporting slurry containing zeolite, a pH adjuster, and a solvent to obtain a mixture. In addition, a step of forming the mixture obtained in the contact step to obtain a molded body is performed. That is, according to this embodiment, zeolite is supported on the inorganic fiber in the contact step, and a molded body of the inorganic fiber supporting the zeolite is formed in the subsequent molding step. Below, the differences from the first embodiment will be mainly described.

(Contacting step)
A predetermined amount of inorganic fibers is added to the support slurry, and the mixture is obtained by stirring and mixing. The mixing time is not particularly limited, and may be about 0.1 to 10 minutes. The content of inorganic fibers in the mixture is preferably 6 to 45 mass%, more preferably 8 to 35 mass%, and even more preferably 10 to 25 mass%. The content of zeolite in the mixture may be the same as or different from the content of zeolite in the support slurry in the first embodiment.

(Molding process)
Instead of the sheet raw material slurry of the first embodiment, the mixture obtained above is wet-laid into a nonwoven fabric to produce a molded body (inorganic fiber sheet) having a sheet structure. Thereafter, a drying process may be provided as necessary. Furthermore, it is preferable to provide a lamination process in which flat and corrugated inorganic fiber sheets are laminated to form a honeycomb structure.

Then, a firing process is carried out on the honeycomb structure to produce a gas adsorption substrate.

Gas adsorption method
The gas adsorption method according to the present embodiment includes the steps of:
The method includes a step of adsorbing an object to be adsorbed by the gas adsorbing substrate manufactured by the method for manufacturing a gas adsorbing substrate.

In this gas adsorption method, the exchange of protons in the zeolite with sodium ions is suppressed, and the substance to be adsorbed is adsorbed using a gas adsorption substrate that supports zeolite with a relatively large amount of protons, so efficient gas adsorption can be achieved over time.

The substance to be adsorbed is preferably an alcohol or an amine. Suitable examples of alcohol and amine include the aforementioned components.

Carrier gases used in the adsorption process include air, as well as inert gases such as nitrogen gas and argon gas.

The temperature, humidity, flow rate, etc. during the adsorption process can be set appropriately taking into consideration the material to be adsorbed, adsorption efficiency, etc.

After the adsorption step, a desorption step may be provided for desorbing the substance to be adsorbed in order to regenerate the gas adsorption substrate. In the desorption step, the gas adsorption substrate may be heated, a desorption gas (air, etc.) may be circulated, or heating of the gas adsorption substrate and circulating the desorption gas may be combined. The adsorption step and desorption step may be repeated.

The present invention will be described in detail below using examples, but the present invention is not limited to the following examples as long as it does not deviate from the gist of the invention.

<Example>
A carrier made of a silica-alumina fiber sheet (thickness 0.2 mm) having a corrugated honeycomb structure with a pitch of 3.3 mm and a peak height of 1.6 mm was cut into a cylindrical shape with a diameter of 200 mm and a thickness of 20 mm to obtain a substrate.

Separately, 16.2 parts by weight of ZSM-5 zeolite (proton type), 16.2 parts by weight of ZSM-5 zeolite (sodium ion type), 35.5 parts by weight of colloidal silica, and 32.1 parts by weight of water were mixed, and nitric acid was added to adjust the pH to 2.5 to obtain a support slurry.

The substrate was immersed in the support slurry, dried, and then fired to obtain the gas adsorption substrate.

Comparative Example
A gas adsorbing base material was obtained in the same manner as in Example, except that nitric acid was not added in preparing the supporting slurry.

<Evaluation: Ethanol adsorption test>
An ethanol adsorption test was carried out using the gas adsorption substrates of the Examples and Comparative Examples according to the following procedure.

<Ethanol adsorption test>
Ethanol was adsorbed onto the gas adsorption substrate packed in a glass column under the following conditions: ethanol concentration: 100 ppm; carrier gas: air; temperature: 25°C; humidity: 65% RH; air volume: 0.0045 ^m3 /min, and an adsorption test was performed by measuring the ethanol concentration at the inlet (inlet concentration) and the ethanol concentration at the outlet (outlet concentration) of the column. The adsorption test was performed until the adsorption capacity of the zeolite was saturated. Specifically, the adsorption test was performed until the outlet concentration reached the inlet concentration (100 ppm).

The amount of ethanol adsorption was calculated by the following procedure. FIG. 3 is an explanatory diagram showing a method for calculating the amount of ethanol adsorption. First, ethanol gas was passed through the gas adsorption substrate under the above conditions, and the inlet and outlet concentrations were measured over time using a hydrocarbon meter (Shimadzu Corporation, "VMS-1000F"). Next, the measured concentration (ppm) was converted to mg/m ³ units. As a result, a chart was obtained in which the ethanol concentration (mg/m ³ ) was plotted against the elapsed time t (min) as shown in FIG. 3. In this chart, minute sections were set every 0.05 min, and the area surrounded by the inlet concentration and the outlet concentration in this minute section was assumed to be a trapezoid (lightly filled trapezoid in FIG. 3), and the area (adsorption amount (mg) per unit volume (m ³ )) in the minute section was calculated. The product of the area and the air volume (m ³ /min) was calculated, and this was taken as the adsorption amount (mg) in the minute section. Finally, the amount of ethanol adsorbed (mg) was calculated by integrating the amount of adsorption (mg) in the small section from the start of the adsorption test (0 min) until the outlet concentration reached the inlet concentration (100 ppm).

Thereafter, the amount of ethanol adsorbed per amount of supported zeolite was calculated by the following calculation formula. The results are shown in Figure 4. Figure 4 is a graph showing the amount of ethanol adsorbed per amount of supported zeolite in the examples and comparative examples.
<Calculation formula>
Amount of supported zeolite: A (g)
Ethanol adsorption amount: B (mg)
Ethanol adsorption amount per amount of supported zeolite: C=B/A (mg/g)

As a result, the adsorption capacity was 21.3 mg/g in the Example, whereas it was 16.2 mg/g in the Comparative Example, and the gas adsorption substrate of the Example showed excellent adsorption performance. This is presumably due to the fact that in the Example, the pH of the support slurry was adjusted to 2.5, so that the cations of the sodium ion type zeolite were exchanged with protons and supported on the gas adsorption substrate in the form of proton type zeolite, whereas in the Comparative Example, the cations of the sodium ion type zeolite were not sufficiently exchanged with protons, and the zeolite was supported in the form of sodium ions.

<Evaluation: Cation exchange evaluation test>
For each of the supporting slurries prepared in the examples and comparative examples, the Na ₂ O content in the zeolite after stirring for 1 hour after preparation was measured. Specifically, the prepared supporting slurry was stirred for 1 hour, and then filtered to collect the zeolite. The filtered zeolite was thoroughly washed with ion-exchanged water and dried to obtain a measurement sample. X-ray fluorescence analysis (XRF) was performed on the measurement sample to determine the Na ₂ O content (mass%). The results are shown in FIG. 5. FIG. 5 is a graph showing the Na ₂ O content in the zeolite of the examples and comparative examples.

Although the supporting slurry of the Example used the same amount of sodium ion type zeolite as the proton type zeolite, the Na ₂ O content was extremely low (0.10 mass% or less). This is presumed to be due to the cations of the sodium ion type zeolite introduced being exchanged with protons. On the other hand, the supporting slurry of the Comparative Example had a high Na ₂ O content, which is presumed to be due to the cations of the sodium ion type zeolite not being sufficiently exchanged with protons.

<Evaluation: Ammonia adsorption test>
An ammonia adsorption test was carried out using the gas adsorption substrates of the Examples and Comparative Examples according to the following procedure.

<Ammonia adsorption test>
Ammonia was adsorbed on the gas adsorption base material packed in a glass column under the following conditions: ammonia concentration: 100 ppm; carrier gas: air; temperature: 25°C; humidity: 50% RH; air volume: 0.0045 ^m3 /min, and an adsorption test was performed by measuring the ammonia concentration at the inlet (inlet concentration) and the ammonia concentration at the outlet (outlet concentration). The adsorption test was performed until the adsorption capacity of the zeolite was saturated. Specifically, the adsorption test was performed until the outlet concentration reached the inlet concentration (100 ppm).

The ammonia adsorption amount was calculated by the following procedure. FIG. 6 is an explanatory diagram showing a method for calculating the ammonia adsorption amount. First, ammonia gas was passed through the gas adsorption substrate under the above conditions, and the inlet concentration and outlet concentration were measured over time using a detector tube (manufactured by Gastec Corporation, ammonia detector tubes "3La", "3L" and "3S"). Next, the measured concentration (ppm) was converted to mg/m ³ units. As a result, a chart was obtained in which the ammonia concentration (mg/m ³ ) was plotted against the elapsed time t (min) as shown in FIG. 6. In this chart, a minute section was set every 1 min, and the part surrounded by the inlet concentration and the outlet concentration in this minute section was assumed to be a trapezoid (the lightly filled trapezoid part in FIG. 6), and the area in the minute section (the adsorption amount (mg) per unit volume (m ³ )) was obtained. The product of the area and the air volume (m ³ /min) was obtained, and this was taken as the adsorption amount (mg) in the minute section. Finally, the amount of ammonia adsorbed (mg) was calculated by integrating the amount of adsorption (mg) in the small section from the start of the adsorption test (0 min) until the outlet concentration reached the inlet concentration (100 ppm).

Thereafter, the amount of ammonia adsorbed per amount of supported zeolite was calculated by the following calculation formula. The results are shown in Figure 7. Figure 7 is a graph showing the amount of ammonia adsorbed per amount of supported zeolite in the examples and comparative examples.
<Calculation formula>
Amount of supported zeolite: A (g)
Ammonia adsorption amount: B (mg)
Ammonia adsorption amount per amount of supported zeolite: C=B/A (mg/g)

As a result, the adsorption capacity was 2.36 mg/g in the Example, whereas it was 1.19 mg/g in the Comparative Example, showing that the gas adsorption substrate of the Example had excellent adsorption performance. The reason for this is the same as that considered in the ethanol adsorption test. That is, in the Example, the pH of the support slurry was adjusted to 2.5, so that the cations of the sodium ion type zeolite were exchanged with protons and supported on the gas adsorption substrate in the form of proton type zeolite, whereas in the Comparative Example, the cations of the sodium ion type zeolite were not sufficiently exchanged with protons, and were supported in the form of sodium ion type.

Reference Signs List 1 Gas adsorption substrate 2a, 2b Opening surface 3 Rotor shaft 4 Ventilation cavity 5 Flat portion 6 Corrugated portion 7 Rotation direction 8 Substrate p Pitch t Ridge height s Thickness

Claims (19)

A method for producing a gas adsorption substrate, comprising the steps of:
The method includes a step of contacting a substrate containing inorganic fibers with a zeolite, a pH adjuster, and a solvent,
The method for producing a gas adsorption substrate, wherein the pH in the contacting step is 2 or more and 3 or less. the substrate is a molded body of the inorganic fibers,
2. The method for producing a gas adsorbing substrate according to claim 1, wherein in the contacting step, the formed body is contacted with a slurry containing the zeolite, the pH adjuster, and the solvent. The method for producing a gas adsorption substrate according to claim 2, wherein the contact is by immersion or coating. The method for producing a gas adsorption substrate according to claim 1 further comprises a step of forming the mixture obtained in the contact step to obtain a molded body. The method for producing a gas adsorption substrate according to any one of claims 1 to 4, wherein the pH adjuster is an inorganic acid. The method for producing a gas adsorption substrate according to claim 5, wherein the pH adjuster is nitric acid. The method for producing a gas adsorption substrate according to any one of claims 1 to 4, wherein the zeolite is a proton type zeolite. The method for producing a gas adsorption substrate according to any one of claims 1 to 4, in which a binder is allowed to coexist in the contact step. The method for producing a gas adsorption substrate according to claim 8, wherein the binder is colloidal silica. The method for producing a gas adsorption substrate according to any one of claims 1 to 4, wherein the sodium ion concentration in the contact step is 4000 ppm or less. 5. The method for producing a gas adsorption substrate according to claim 1, wherein the Na ₂ O content in the zeolite after the contact step is 0.10 mass % or less. The method for manufacturing a gas adsorption substrate according to any one of claims 2 to 4, wherein the formed body is a honeycomb structure. The method for producing a gas adsorption substrate according to any one of claims 1 to 4, wherein the gas adsorption substrate is for adsorbing alcohol or amine. A gas adsorption method comprising: adsorbing an object to be adsorbed by a gas adsorption substrate manufactured by the method for manufacturing a gas adsorption substrate according to claim 1. The gas adsorption method according to claim 14, wherein the substance to be adsorbed is an alcohol or an amine. The present invention comprises a substrate containing inorganic fibers and zeolite supported on the substrate,
A gas adsorption substrate having an alcohol adsorption amount of 20.0 mg/g or more according to the following alcohol adsorption test.
(Alcohol adsorption test)
Alcohol is adsorbed on the gas adsorption base material packed in a glass column under the following conditions: alcohol concentration: 100 ppm; carrier gas: air; temperature: 25° C.; humidity: 65% RH; air volume: 0.0045 m ³ /min, and the alcohol concentration at the inlet (inlet concentration) and the alcohol concentration at the outlet (outlet concentration) of the column are measured. The adsorption test is carried out until the outlet concentration reaches the inlet concentration (100 ppm). In a chart plotting the alcohol concentration (mg/m ³ ) against the elapsed time t (min), the adsorption amount (mg) of the part surrounded by the inlet concentration and the outlet concentration in the section from the start of the adsorption test (0 min) to the outlet concentration reaching the inlet concentration (100 ppm) is integrated to obtain the alcohol adsorption amount (mg). The gas adsorption substrate according to claim 16, wherein the alcohol is ethanol. The present invention comprises a substrate containing inorganic fibers and zeolite supported on the substrate,
A gas adsorption substrate having an amine adsorption amount of 2.0 mg/g or more according to the amine adsorption test described below.
(Amine Adsorption Test)
Amine is adsorbed on the gas adsorption base material packed in a glass column under the following conditions: amine concentration: 100 ppm; carrier gas: air; temperature: 25° C.; humidity: 50% RH; air volume: 0.0045 m ³ /min, and the amine concentration at the inlet (inlet concentration) and the amine concentration at the outlet (outlet concentration) of the column are measured. The adsorption test is carried out until the outlet concentration reaches the inlet concentration (100 ppm). In a chart plotting the amine concentration (mg/m ³ ) against the elapsed time t (min), the adsorption amount (mg) of the part surrounded by the inlet concentration and the outlet concentration in the section from the start of the adsorption test (0 min) to the time when the outlet concentration reaches the inlet concentration (100 ppm) is integrated to obtain the amine adsorption amount (mg). The gas adsorption substrate according to claim 18, wherein the amine is ammonia.

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