JPH0956799A - Self-regenerative adsorbent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the adsorption of even a very small quantity of bad-smell component in the living space and make the adsorbing performance recoverable by heating, by making a specified quantity of the oxide of iron or others supported on the mixture of zeolite or other inorganic porous substances, and thus, constituting an adsorbent. SOLUTION: The mixture of one kind or two or more kinds selected from the group comprising silica gel, zeolite, alumina and silica alumina which are inorganic porous substances are made to be the support body. Then, metal oxide containing one metal or plural metals selected from the group comprising iron, chromium, nickel, cobalt, manganese, zinc, copper, magnesium and calcium are supported by the support body in 0.1 to 20 weight%. Thus, the self- regenerative adsorbent is formed. As the support for the metal oxide, zeolite which is higher than 5 in mole ratio of silica to alumina, is preferable, and that higher than 10 is more preferable.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an adsorbent having a self-regenerating function. More specifically, if the adsorbent adsorbs a malodor generated inside the refrigerator or in the garbage treatment equipment, heating will decompose and remove the malodorous substance adsorbed by the interaction between the adsorbent and the specific metal oxide. It is a self-regenerating type adsorbent that has the excellent property of recovering its adsorptivity.

[0002]

2. Description of the Related Art Recently, as the living environment changes, interest in removing a small amount of odorous gases such as ammonia, mercaptans, amines, aldehydes, hydrogen sulfide, and lower carboxylic acids present in living spaces is increasing. A deodorant is required to remove these malodorous gases and maintain a comfortable living environment, and various malodorous gas adsorbents are also used in home life.

For example, as a method for removing various odors generated inside a refrigerator and odors generated when using a garbage processor, the following are practical methods.

First, there is a method of removing by utilizing an adsorbent such as activated carbon, and in principle utilizing a physical adsorption action. Activated carbon is a unique substance that exhibits extremely excellent adsorbability as a nonpolar adsorbent, and exhibits high adsorbability for almost all gaseous substances. However, it is difficult to sufficiently remove ammonia and lower aliphatic aldehydes in the above-mentioned malodor with only ordinary activated carbon. Also, when the saturated adsorption is reached, the life of the adsorbent is expired, so it is necessary to replace it periodically.

As an adsorbent other than activated carbon, silica gel,
There are various types such as activated alumina, zeolite, activated clay and synthetic resin, but their adsorption capacity is less than that of activated carbon. Further, since the surface is usually hydrophilic, moisture is preferentially adsorbed from the malodorous gas containing moisture, so that the malodorous gas may not be sufficiently removed.

When ozone is used, it is necessary to devise the device so that harmful ozone does not leak out of the system, and it is also necessary to install an ozone generating tube, which increases the cost of the device. Further, since the volume of the device is large and very bulky, there is a drawback that the space cannot be effectively used.

On the other hand, there is known a method of completely regenerating the adsorbent by oxidatively decomposing the adsorbed malodorous substance at a high temperature with an adsorbent carrying a noble metal catalyst. Platinum and palladium are known as noble metals used in this case.
Platinum and palladium are particularly suitable because of their high ability to oxidize and decompose other substances at relatively low temperatures, but they have the problem of being extremely expensive. The following are examples of using this method. First,
2-213080 discloses a heating device using a catalyst coating layer made of a platinum compound and activated alumina. Since this application is a household electric appliance such as an electric stove or an electric kotatsu that is constantly heated, the performance of the adsorbent is often not fully exhibited. This is because the physical adsorption action of solids generally decreases as the temperature rises.

Further, Japanese Patent Laid-Open No. 2-275277 discloses an example of a deodorizing device of a storage in which a heater for defrosting is coated with a deodorizing agent containing a platinum catalyst, and Japanese Utility Model Laid-Open No. 4683/1992 discloses an odor adsorbent and an oxidizing agent. An example of a refrigerator with a deodorizer coated with a deodorizing material mixed with an accelerator is disclosed. However, in these publications, there is no description of a specific removal test using a malodorous gas, and the details of the malodorous removal action are unknown.

In the case of the high temperature oxidative decomposition method, it is necessary to use a flame-retardant inorganic compound as an adsorbent, but as described above, the adsorption capacity of an inorganic adsorbent is generally smaller than that of activated carbon and the like. The malodorous gas cannot be sufficiently removed only by the system adsorbent.

[0010]

DISCLOSURE OF THE INVENTION The present invention is intended to remove a small amount of malodorous components existing in daily living space, and has a sufficient adsorption action for these malodorous components and also adsorbed malodorous components. It is intended to provide a self-regenerating type adsorbent having a function of recovering the adsorptivity by heating the adsorbent with a heater or the like.

[0011]

Means for Solving the Problems The present inventors have conducted various researches for metals or metal oxides having a high oxidative decomposition ability for malodorous components, and as a result, iron, chromium, nickel, cobalt, manganese, zinc, copper, magnesium It has been found that metal oxides containing one or more metals selected from the group consisting of and calcium are suitable for this purpose. Further, silica gel supporting the above metal oxide, zeolite,
It has been found that a porous material selected from the group consisting of alumina and silica-alumina has excellent ability to oxidize and decompose malodorous components. Furthermore, the present invention has been reached as a result of examining the composition of the deodorant and the heating medium.

That is, according to the present invention, iron, chromium, nickel, cobalt, manganese, and zinc are added to one or a mixture of two or more selected from the group consisting of silica gel, zeolite, alumina, and silica-alumina, which are inorganic porous materials.
0.1% metal oxide containing one or more metals selected from the group consisting of copper, magnesium and calcium.
It is a self-regenerating type adsorbent loaded with up to 20% by weight, and an adsorbent obtained by applying these compositions to an electric heating medium. Here, the metal oxide carrier is preferably a zeolite having a silica / alumina molar ratio (hereinafter referred to as silica / alumina ratio) of 5 or more, more preferably 10 or more.

Here, the supported amount of the metal oxide is shown in terms of pure metal content. The self-regenerating type adsorbent refers to an adsorbent having a function of oxidizing and decomposing a malodorous component and recovering its adsorptivity by heating the adsorbent after adsorbing the malodorous substance.

Hereinafter, the present invention will be described in detail.

As the inorganic porous material used as the carrier for the metal oxide in the adsorbent of the present invention, one or a mixture of two or more selected from the group consisting of silica gel, zeolite, alumina and silica-alumina is used. It

The silica gel used in the present invention is an adsorbent produced by coagulating a silicic acid colloidal solution. The main component is silicon dioxide, which has a pore structure, and has a specific surface area of 90 to 500 m ² / g. It usually has a pore volume of 0.1 ml / g or more and has high adsorptivity. The pore volume, particle size and shape are not particularly limited and can be used.

The zeolite used in the present invention is an aluminosilicate, which is a substance having a three-dimensional skeleton and a pore structure formed in the voids. It has a large specific surface area of 100 m ² / g or more and high adsorptivity based on it. The composition and structure are not particularly limited, and both natural products and synthetic products can be used. The pore volume, particle size and shape can be used without any particular limitation, but the specific surface area is 100 m ² / g or more and the particle size is 50
A mesh size or less (particle size of about 0.3 mm or more) is preferable.

Zeolites, as mentioned above, consist mainly of alkali or alkaline earth metal aluminosilicates,
The methane type SiO ₂ tetrahedron and the AlO ₄ tetrahedron form a three-dimensional skeleton structure with large regular cavities in which one carbon atom is shared by each other.

Due to the cyclic structure of oxygen forming the skeleton of the zeolite, the zeolite has a constant pore size in the range of 3 to 10Å, and has the adsorptivity and molecular sieving property based on this pore structure. Zeolites that have been synthesized to have a uniform pore size with a constant composition and have the property of selectively adsorbing only molecules of a constant size are called "molecular sieves" and have various pore sizes. "Molecular sieve" is commercially available and can be used as a carrier for the adsorbent of the present invention.

Alumina used in the present invention is mainly composed of alumina oxide, has a porous structure, and usually exhibits a high adsorptivity at a pore volume of 0.3 ml / g or more. Pore volume, particle size, and shape are not particularly limited and can be used.

The chemical composition of silica-alumina is SiO ₂
And consists Al ₂ O _3, exhibits high adsorptivity has a porous structure obtained by combining silica gel and alumina gel. Usually, it is often used as a catalyst for petroleum refining, but it can also be used as the carrier of the present invention.

Each of the substances used as the above-mentioned carrier has a porous structure and a large specific surface area and exhibits a high adsorptivity. Particularly, the specific surface area is 100 m ² / g or more, more preferably 1
Carrier is from 00 to 1,500 m ² / g are preferred. Similar to activated carbon, these carriers can be used in any of powder, crushed, columnar, spherical, fibrous and honeycomb shapes.

Further, the above-mentioned carriers silica gel, zeolite, alumina, and silica-alumina may be used alone, or two or more kinds may be mixed and used.

As the adsorbent of the present invention, a high silica zeolite having a silica / alumina ratio of zeolite of 5 or more, preferably 6 or more is preferable, and a silica / alumina ratio of 10 or more.
The above-mentioned so-called hydrophobic zeolite is more preferable.

[0025] Zeolites with aqueous alkali metal or alkaline earth metal salts of crystalline alumino-silicate, the composition of _{^{Me 2 / n O · Al 2}} O 3 · xSiO 2 · yH 2 O ( wherein Me;
Na, K, Ca, etc., n; Me valence, x, y; integer), and the molar ratio of SiO ₂ to Al ₂ O ₃ , that is, x corresponds to the silica / alumina ratio. This composition is a porous material having a three-dimensional skeleton and a pore structure formed in the gaps,
It has a specific surface area of 0 m ² / g or more and high adsorptivity based on it. Includes those with a fairly wide range of compositions, pore sizes, and pore volumes, including natural and synthetic products. The structure and properties of zeolites are determined by the silica / alumina ratio.

The silica / alumina ratios of the main zeolites are shown below. Fluorite: 2, Duck fluor; 2, Soda fluor; 1, Thomson fluor; 1, Eddington fluor; 1.5
, Sodalite; 1, cancrinite; 1, gmelinite; 2, chabazite; 2, erionite; 3, offretite; 3.5, zeolite L; 3, quinite, 2.5;
Brewster Fluorite; 3, Mordenite; 5, Ferrierite; 5, Biquitite; 2, Faujasite; 2.3
, Zeolite A 1; The zeolite having a silica / alumina ratio of 4 or more in the present invention refers to mordenite, ferrierite and the like.

In the present invention, a zeolite having a silica / alumina ratio of 5 or less may be used as a raw material, and the aluminum in the skeleton may be removed or replaced with silicon to use a silica / alumina ratio of 5 or more. Examples of the method of increasing the silica / alumina ratio include a method of eluting aluminum in the skeleton of zeolite by boiling zeolite with mineral acid, a method of desorbing aluminum in the skeleton by hydrothermal treatment of zeolite, or The method of desorbing aluminum in the skeleton by gradually adding EDTA (ethylenediaminetetraacetic acid) to zeolite using a Soxhlet extraction tube or the like can be mentioned. As described above, the so-called hydrophobic zeolite having a silica / alumina ratio of 10 or more is most suitable as the carrier for the metal oxide of the present invention.

As described above, the hydrophobic zeolite is obtained by subjecting a normal zeolite to a special chemical treatment to impart hydrophobicity to the surface to increase the amount of malodorous substances adsorbed, and the aluminosilicate composition of the zeolite. It is a high-silica zeolite with a high content of silica.

For example, ZSM series such as zeolite ZSM-5, silicalite, or ultra-stable Y-type zeolite (US-Y) obtained by dealumination of existing Y-type zeolite by steam treatment or the like is included. The silica / alumina ratio should be at least 10 or higher, preferably 200
It should be above. Specifically, the silica / alumina ratio is 200 to 500 and the pore size is 6.2 as described in JP-A-64-85113.
Silicalite of A or higher, or dealuminated Y-type zeolite such as hydrophobic zeolite or Cosmetics
& Toiletries Vol. 109 (1994) P.77-82 US
Hydrophobic molecular sheep type deodorants "Absentu" and "Sumerlite" manufactured by UOP are suitable.

In the present invention, the specific metal oxide must be supported on the specific inorganic porous material in an amount of 0.1 to 10%. To carry a metal oxide on the above-mentioned inorganic porous body, for example, an aqueous solution is prepared using a water-soluble metal salt, and a predetermined amount thereof is contained in the porous body, and then pyrolyzed at a high temperature. The metal oxide can be supported on the porous body. Next, specifically describing the attachment method, an aqueous solution in which a predetermined amount of metal salt is dissolved is put into a granular, honeycomb-shaped or fibrous porous body and stirred, and the metal salt is sufficiently adsorbed and then drained. ,
Dry at 200 ° C. Alternatively, it can also be obtained by sprinkling an aqueous solution of a predetermined concentration on activated carbon to absorb it and subjecting it to dry heat treatment. The supported amount of the metal oxide needs to be 0.1 to 10%, but the supported amount is more preferably 0.5 to 5% within this range.

When the supported amount of the metal oxide is 0.1% or less, the catalytic activity is insufficient, and when the supported amount is 10% or more, the catalytic activity is not improved despite the large amount of the impregnated metal, and the adsorption performance of the activated carbon itself is impaired. To be done. Considering these points, the amount of impregnation is
It should be 10% or less. The amount of the metal oxide supported is adjusted by changing the ratio between the concentration of the metal oxide in the aqueous solution and the amount of the porous body.

As the metal salt, inorganic acid salts such as hydrochlorides, nitrates, lead sulfates and carbonates, organic acid salts such as acetates, oxalates and formates, or hydroxides can be used. Mixtures of salts can also be used. As the salt counterion acid, an aqueous solution containing an acid such as hydrochloric acid, nitric acid, acetic acid or formic acid can be used.

The metal oxide to be supported must contain one or more selected from the group of oxides consisting of iron, chromium, nickel, cobalt, manganese, zinc, copper, magnesium and calcium. Further, the loading amount of these metal oxides must be 0.1 to 20% by weight.

Heat treatment is required to convert the metal salt attached to the porous body into a metal oxide, but the treatment temperature is preferably 200 ° C. or lower, preferably 150 ° C. or lower in order to enhance the catalytic performance. . Further, in order to increase the adhesive strength of the catalyst, heat treatment may be performed at 300 ° C. or higher, if necessary. The self-regenerating type adsorbent of the present invention does not need to completely convert the supported metal salt into a metal oxide, and retains the function as an oxidation catalyst even when it contains an amorphous metal oxide.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION To prepare the adsorbent of the present invention,
It is prepared by slurrying the above-mentioned inorganic porous material supporting the metal oxide according to a conventional method and forming a coat layer on the surface of an electric heating medium such as a heater device. The slurry can be prepared by adding a dispersant, a surfactant, a thickener, a binder and the like to zeolite or the like carrying these metal compounds. In the present invention, a metal oxide is supported on a plate-shaped or honeycomb-shaped inorganic porous material and is used either by being constantly heated or by being heated at the time of regeneration.

The method of heating the adsorbent is not particularly limited. For example, the adsorbent may be blown with warm air of 200 ° C. or higher, or the adsorbent may be electrically heated. In the present invention, when the adsorbent is applied to the electric heating medium, heat is transferred to the electric heating medium rapidly and efficiently, and aluminum, stainless steel, heat-resistant glass, cordierite or the like is suitable for the surface of the electric heating medium. Considering the decomposition temperature of malodorous components in the presence of a catalyst, the heating temperature is 200 ° C or higher, preferably
It is preferably 250 ° C or higher.

The surface of the electric heating medium of the heater device is preferably aluminum, stainless steel, heat-resistant glass such as quartz glass or crystallized glass, or ceramics such as cordierite. The heating portion of the heater device is a heater made of stainless steel, aluminum, etc., and the PTC heater whose internal resistance changes with temperature and whose temperature rises only up to about 200 ° C to 400 ° C is preferable. In addition, a heater device in which a quartz glass tube, a crystallized glass tube, or a ceramics tube such as a cordierite tube in which a metal wire such as a nichrome wire or a kanthal wire is coiled can be incorporated can be used.

For these heaters, for example, a defrosting heater for a refrigerator or a heating heater for a garbage disposal may be used. As a method for applying the adsorbent to the heater device, a usual method such as a spray method, a roller method, or a dipping method can be used.
In some cases, an undercoating coating may be applied between the heater device material and the adsorbent slurry in consideration of the adhesiveness. After applying the slurry to the electric heating medium, it is possible to form a robust adsorbent layer on the surface by firing at a predetermined temperature.

The adsorbent of the present invention exhibits a high adsorbability for a small amount of malodorous components such as ammonia, mercaptans, amines, aldehydes, hydrogen sulfide and lower carboxylic acids even in an atmosphere containing water. In addition, the adsorbent is applied to the electrothermal medium, and by heating the adsorbent that has adsorbed the malodorous gas at regular intervals, strong oxidative decomposition due to the synergistic action of the catalytic action of the metal oxide and the adsorptivity of the porous substance. It has a self-regeneration function that removes malodorous substances by the action and restores the adsorption of malodorous gas. This is the greatest feature of the adsorbent of the present invention. Further, the adsorbent of the present invention is significantly cheaper than a self-regenerating type adsorbent using a platinum and / or palladium compound.

The deodorizing mechanism of the deodorant of the present invention is considered as follows in the case of electric appliances such as refrigerators. Malodorous gas is sufficiently adsorbed in the operating temperature range of electrical appliances below normal temperature by an inorganic porous material, such as zeolite, which retains a high adsorption capacity for malodorous components even in an atmosphere containing water, and automatically When the heater device is energized, the temperature of the adsorbent that has adsorbed the malodorous gas rises, and the malodorous odor is produced by the synergistic action of the catalytic action of the metal oxide and the adsorptive property of the porous substance that is the carrier of these metal compounds. It is considered that the components are oxidized and decomposed and changed into odorless substances such as carbon dioxide and water.

In order to completely oxidatively decompose these malodorous substances without using a catalyst, a high temperature of 600 ° C. to a few thousand hundreds of ° C. is usually required. However, the adsorbent of the present invention has a metal oxide catalyst as described above. Due to such effects, malodorous substances can be completely oxidatively decomposed in a relatively low temperature range of about 200 ° C to 400 ° C.

Further, by completely oxidizing and decomposing the adsorbed malodorous component, the adsorption capacity can be almost completely restored to the state before use. Therefore, the life of the adsorbent is semi-permanent and it is not necessary to replace it. Further, the adsorbent of the present invention may be used in a place where it is constantly heated to a high temperature, but it is possible to adsorb a malodorous substance at room temperature or lower and to decompose it at a high temperature by periodically energizing a heater. Suitable usage is especially suitable.

[0043]

The present invention will be described more specifically with reference to the following examples.

(Examples 1 to 10) Iron was used as the metal oxide.
Oxides of chromium, nickel, cobalt, manganese, zinc, copper, magnesium and calcium were used, and mordenite having a silica / alumina ratio of 5 was crushed to a size of 350 mesh (opening 44 μm) or less and used as a carrier. The metal oxide was supported on the carrier as follows. 100 ml of an aqueous solution of metal nitrate containing 1 g of metal was mixed with 50 g of mordenite, stirred well, left for 3 hours and then baked at 130 ° C for 4 hours to prepare metal oxide-supporting mordenite (supporting 2% as metal). .

25 parts of mordenite carrying the above metal oxide was added to an aqueous solution prepared by adding 1.5 parts of Laponite XLG manufactured by Laport Co., Ltd. to 100 g of water as a dispersant, and stirred well, and further 4 parts of sodium m-xylene sulfonate. And 5 parts of propylene glycol were added and mixed to prepare a slurry.

A silica-based binder was applied to the outer surface of a Pyrex glass tube having a diameter of 10 cm, and the above slurry was applied thereto by a roller method. An adsorbent sample was prepared by drying and heating the tube at 430 ° C. while gradually raising the temperature. The amount of adsorbent applied was 1.0 g / line.

The adsorbent sample obtained and a PTC heater capable of keeping the temperature during heating constant were set in a 30-liter acrylic box, 100 ppm of methyl mercaptan was introduced, and elapsed time and removal rate were measured by gas chromatography. It was measured using a graph. After 120 minutes, the surface temperature of the adsorbent
The adsorbent was regenerated by energizing the sheeter at 400 ° C and holding it for 10 minutes.

Further, methyl mercaptan was introduced into the box to adjust the concentration to 100 ppm. After the elapsed time and the methyl mercaptan removal rate were measured in the same manner as above, heating and regeneration were performed again. This operation was repeated 10 times, and the relationship between the elapsed time at the 10th time and the removal rate is shown in Table 1. Similarly, for trimethylamine, the initial concentration of trimethylamine in the box is 100 p
Tested as pm. Table 1 also shows the results.

[0049]

[Table 1]

In all cases, good adsorption performance was shown, but the adsorbent supporting manganese oxide was superior in the methyl mercaptan removal test, and the adsorbent supporting copper oxide was superior in the trimethylamine removal test. showed that. In addition, the adsorbent supporting 1% of manganese and 1% of copper as the metal components showed good removal performance for both methyl mercaptan and trimethylamine, and showed an excellent effect.

(Examples 11 to 22) Using zeolites having various silica / alumina ratios, adsorption and regeneration tests of malodorous gas were conducted in the same manner as described above. The results are shown in Table 2.

[0052]

[Table 2]

It is recognized that the higher the silica / alumina ratio of the zeolite, the higher the malodorous gas adsorbing property and the regenerating function. When the silica / alumina ratio of 200 absent is used as the carrier, the most excellent malodorous gas adsorption is obtained. It was confirmed that it has a regenerating function by heat and heat.

(Examples 23 to 26) Adsorbents were prepared in the same manner as in Examples 1 to 10 by using silica gel and activated alumina as a carrier for metal oxides, and a malodorous gas adsorption and regeneration test was conducted. Table 3 shows the results.

[0055]

[Table 3]

It is shown that the use of any of the carriers has a good malodorous gas adsorption and regeneration function.

[0057]

EFFECT OF THE INVENTION The malodor adsorbent of the present invention has a property that it can be repeatedly used by recovering its adsorptivity by heating, and trace amounts of ammonia, mercaptans, amines, aldehydes, hydrogen sulfide and low-grade substances generated in household electric appliances and the like. Excellent in removing malodorous gas such as carboxylic acid. In particular, when applied to a defrosting heater of a refrigerator or a heating heater of a garbage disposal, it absorbs malodorous components generated at low temperature and decomposes the malodorous components adsorbed by regular heating to almost It can be used semipermanently because the adsorptivity can be completely regenerated.

Claims (4)

[Claims] 1. One or a mixture of two or more selected from the group consisting of silica gel, zeolite, alumina and silica-alumina, selected from the group consisting of iron, chromium, nickel, cobalt, manganese, zinc, copper, magnesium and calcium. Self-regenerating type adsorbent which carries 0.1 to 20% by weight of a metal oxide containing one or more of the above-mentioned metals. 2. One or a mixture of two or more selected from the group consisting of silica gel, zeolite, alumina and silica-alumina, selected from the group consisting of iron, chromium, nickel, cobalt, manganese, zinc, copper, magnesium and calcium. A self-regenerating adsorbent obtained by applying a composition in which 0.1 to 20% by weight of a metal oxide containing one or more of the above-mentioned metals is applied to an electric heating medium. 3. The self-regenerating type adsorbent according to claim 1, wherein the silica / alumina molar ratio of the zeolite is 5 or more. 4. The silica / alumina molar ratio of the zeolite is
The self-regenerating type adsorbent according to claim 1 or 2, which is 10 or more.