JP2002079080A - Aldehydes adsorbing and decomposing agent and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aldehydes adsorbing and desorbing agent which is excellent in aldehyde adsorbing activity at room temperature in the presence of water vapor, decomposes the adsorbed aldehydes without desorption by heating at a relatively low temperature, to enable to recover the adsorption activity. SOLUTION: The agent comprises at least one element selected from the groups IIa and IIIa in the periodic table and an inorganic compound containing at least one transition metal. In a method for producing the agent, a precipitate is prepared from a metal salt mixed solution containing at least one element selected from the groups IIa and IIIa in the periodic table and at least one transition metal by using an alkali, separated from the solution, and subjected to oxidation treatment. The agent is mounted on an air cleaning filter and/or an air cleaner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to homes, offices,
This is related to an adsorbent decomposer for removing aldehydes in the gaseous phase generated in living spaces such as vehicle interiors and various factories, etc., and includes air purification filters, air purifiers, air conditioners, garbage disposal machines, It can be used for a processing device and the like.

[0002]

2. Description of the Related Art In recent years, odorous and harmful gases have often become a problem due to the tightness of living spaces and the increasing tendency toward amenities, and in particular, there is a need for removing aldehydes such as formaldehyde, acetaldehyde, acrolein, and nonenal. large.

[0003] In order to remove these aldehydes, usually,
Activated carbons impregnated with amine compounds are often used, but these have problems in terms of their life, and amines are easily deactivated on activated carbons due to thermal and temporal chemical changes, and are satisfactory for a long time. It is difficult to develop a power removal performance.

On the other hand, recently, deodorizing catalysts capable of decomposing aldehydes even at relatively low temperatures are attracting attention, and many catalysts composed of noble metals, base metals and oxides thereof have been proposed. For example, JP-A-6-7678 discloses A
g, MnO ₂ , NiO, CuO, Fe ₂ O ₃ , Co ₃ O ₄ and at least one component selected from the group consisting of Li ₂ O, K ₂ O, and N
a ₂ O, and at least one oxide selected from CaO, zeolite deodorizing catalyst was supported in the form of a mixed oxide or compound, also JP-A-7-155611, carrying a silver compound, Disclosed are catalysts for removing malodorous substances composed of alumina, all of which disclose that acetaldehyde is adsorbed or decomposed and removed at around normal temperature. However, the metal oxides and metal compounds that constitute the above-mentioned catalysts are hydrophilic in nature, and in the presence of water vapor as in ordinary living space, water is selectively adsorbed over aldehydes, so that the removal ability rapidly decreases. However, there is a problem that a sufficient removing effect cannot be exerted over a long period of time.

For the purpose of suppressing such a decrease in removal ability due to water vapor, a deodorant and an adsorbent in which a catalyst component is supported on a hydrophobic zeolite have been proposed. JP-A-8-243383 discloses that a silica / alumina ratio of 1 is used.
A hydrophobic deodorant in which manganese dioxide and a copper compound are supported as a catalyst component on a hydrophobic zeolite of at least 00 has been disclosed, which adsorbs acetaldehyde at room temperature and in the presence of water vapor, and then recovers the adsorption performance by heating at 150 ° C or higher. It is stated that it will be. However, since the above-mentioned mechanism of adsorbing the malodorous gas of the hydrophobic zeolite is physical adsorption, there is a problem that the malodorous component is desorbed before being decomposed during heating for the regeneration treatment.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has an excellent aldehyde adsorbing ability near room temperature and in the presence of water vapor.
Further, it is an object of the present invention to provide an adsorbent decomposer capable of restoring adsorption ability by decomposing aldehydes once adsorbed by heat treatment at a relatively low temperature without desorbing, and a method for producing the same.

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, first, an inorganic compound comprising at least one metal selected from the group consisting of transition metals, especially manganese, cobalt, nickel and copper. It has been found that, preferably, oxides exhibit chemisorption ability to aldehydes, and decomposition activity is observed even at relatively low temperatures. However, this inorganic compound has a problem that the adsorptivity is rapidly reduced in the presence of water vapor in the presence of water vapor as compared with a completely dry atmosphere. Therefore, as a result of various investigations to solve this, as a result of further complexing the inorganic compound with at least one metal selected from Groups 2a and 3a of the periodic table, the water vapor is reduced without lowering the decomposition activity. It has been found that the adsorption ability in the presence can be improved, and the present invention has been achieved.

[0008]

SUMMARY OF THE INVENTION The present invention provides a periodic table 2a.
Including at least one element selected from the group consisting of group 3a and group 3a
Measured by nitrogen gas adsorption BET method composed of inorganic compounds
50m specific surface area ^Two/ G or more of aldehydes
It is a decomposition agent.

In a preferred embodiment of the aldehyde-adsorbing and decomposing agent of the present invention, the content of at least one element selected from Groups 2a and 3a of the periodic table with respect to the total amount of the inorganic compound is 0.1% in terms of oxide. Aldehydes adsorbing and decomposing agent in an amount of 10 to 10% by weight.

A preferred embodiment of the aldehyde-adsorbing / decomposing agent of the present invention is an aldehyde-adsorbing / decomposing agent in which the inorganic compound contains at least one transition metal.

In a preferred embodiment of the aldehydes-adsorbing / decomposing agent of the present invention, the inorganic compound contains at least one element selected from manganese, cobalt, nickel and copper.

A preferred embodiment of the present invention is an air purifying filter and / or an air purifier characterized in that any one of the aldehyde-adsorbing and decomposing agents is mounted.

The present invention also relates to a method for producing an aldehyde-adsorbing / decomposing agent comprising an inorganic compound, comprising the steps of:
From a mixed solution of a metal salt containing at least one element selected from Group 3a and Group 3a, using an alkali to form a precipitate, separating the precipitate from the solution, and further performing an oxidation treatment. is there.

Further, a preferred embodiment of the present invention is a production method in which the alkali in the production method is a carbonate compound.

Hereinafter, the present invention will be described in detail. The present invention is an aldehyde-adsorbing / decomposing agent comprising an inorganic compound containing at least one element selected from Groups 2a and 3a of the periodic table. When the inorganic compound is an oxide of a transition metal or a composite oxide as described later, the adsorbability of aldehydes is rapidly reduced in the presence of water vapor as compared with a completely dry atmosphere. This is presumably because the charge is unbalanced at a structural defect or the like which is considered to be an adsorption / decomposition site for aldehydes, and water molecules having a larger polarity than aldehydes are selectively adsorbed. The periodic table 2a
It is presumed that when a metal selected from Group 3a and Group 3a is further compounded, the state of charge imbalance is alleviated, thereby inhibiting the water adsorption capacity and promoting the adsorption of the gas to be removed. . As the element selected from Group 2a and Group 3a of the periodic table, strontium, barium, scandium, yttrium, lanthanum, and cerium are particularly preferable.

The content of the element selected from Groups 2a and 3a of the periodic table in the present invention is 0.1 to 10% by weight in terms of oxide based on the total amount of the inorganic compound. If the content is less than this, the effect of inhibiting water adsorption capacity is not sufficient,
Conversely, if the content is higher than this, the gas adsorption capacity and decomposition activity decrease, which is not preferable.

The inorganic compound constituting the aldehyde-adsorbing and decomposing agent of the present invention is a transition metal oxide, more preferably a composite oxide of two or more transition metals. Transition metals include chromium, manganese, iron, cobalt, nickel,
Copper, zinc and the like, but preferably manganese,
Cobalt, nickel and copper. If necessary, a platinum group metal such as ruthenium, rhodium, palladium, silver, platinum, or gold may be compounded or supported on the platinum group metal.

The inorganic compound of the present invention can be obtained by a precipitation method. That is, an alkaline aqueous solution is added to a mixed solution of a compound of at least one element selected from Groups 2a and 3a of the periodic table and a salt of at least one transition metal to obtain a precipitate, which is then oxidized. Can be obtained. As the alkali, a carbonate compound is preferable, and examples thereof include sodium carbonate and potassium carbonate. It is preferable to add an aqueous alkaline solution until the pH of the solution becomes 7.5 or more, preferably 8 or more. The oxidation treatment includes a method of performing liquid phase oxidation using an oxidizing agent and a method of baking in the air. Examples of the oxidizing agent include potassium permanganate and ammonium persulfate. The preferred range of the firing temperature is 200 to 400 ° C. Most of the inorganic compounds obtained by such a production method exist as oxides.

The aldehyde-adsorbing / decomposing agent of the present invention has a specific surface area of 50 m ² / g measured by a nitrogen gas adsorption BET method.
Above, preferably at least 100 m ² / g, the adsorption resolution becomes a satisfactory level. It is considered that structural defects and the like of metal oxides and composite oxides function as sites for adsorption and decomposition of aldehydes, and the larger the number thereof, the larger the adsorption capacity and decomposition activity and the larger the specific surface area. The specific surface area measured by the nitrogen gas adsorption BET method can be determined by the following method. That is, the adsorption isotherm of nitrogen gas at liquid nitrogen temperature was measured, and from this data B
The monolayer adsorption amount of nitrogen is determined by the ET equation. Since the occupied area per nitrogen molecule is known, the specific surface area can be calculated from this. Specifically, after the adsorption isotherm was measured using an ASAP2010 device manufactured by Shimadzu Corporation, the adsorption equilibrium pressure / saturated vapor pressure was 0.05 to 0.
It was calculated using the adsorption amount data in the range of 20.

The aldehyde-adsorbing / decomposing agent of the present invention is mounted on an air purifying filter or an air purifier, and can be used for air purifying applications in living spaces such as homes, offices, car interiors, and various factories. In this case, the powdery, crushed adsorptive decomposer may be used as it is, but an appropriate binder is added to form a pellet, a doublet, or a honeycomb, a sheet, a corrugated plate, or the like. It can also be used by supporting it on a carrier such as a net. As a carrier,
In addition to ceramics, metal foils, glass fiber sheets, nonwoven fabrics of polymer fibers, nets, urethane sheets, etc., materials capable of self-heating by energization can also be used.

The aldehyde-adsorbing / decomposing agent of the present invention is capable of adsorbing aldehydes mainly by chemical adsorption, decomposing them by heating, and regenerating the adsorbing ability. In the case of chemisorption, since a kind of chemical bond is formed between the aldehyde and the adsorbent, the aldehyde once adsorbed upon heating as in physical adsorption is not easily desorbed. The use temperature of the adsorptive decomposer of the present invention is not particularly limited. In addition to the method of repeating adsorption and heating and regeneration at a temperature close to normal temperature, continuous use while heating is also possible. However, when heated at a temperature higher than the sintering temperature at the time of production, the characteristics of the adsorptive decomposer change. The heating method is not particularly limited. In addition to heating using hot air, electric heat, infrared rays, electromagnetic waves, or the like, heating may be performed by supporting a carrier capable of generating heat.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Evaluation of initial adsorption capacity of acetaldehyde)
A 0.25 cc sample of the adsorptive decomposer was packed in a glass column having an inner diameter of 10 mmφ with both sides sandwiched by glass wool. 25 ° C containing 10 ppm of acetaldehyde,
60 RH% air was continuously circulated at 400 ml / min. The ambient temperature of the sample was also set to 25 ° C. The gas on the inlet / outlet side of the sample is sampled at regular intervals, and the FID
The acetaldehyde concentration was measured by a gas chromatograph with a gas chromatograph, and the removal ratio was calculated from the ratio. This removal rate is 5%
Distribution and concentration measurement were continued until the concentration became below. The amount of acetaldehyde adsorbed (mg) was determined by integrating the curve of the removal rate with respect to the amount of acetaldehyde supplied (calculated from the concentration, flow rate, and temperature), and this was divided by the weight of the sample.
The adsorption capacity (mg / g) was calculated.

(Evaluation of Recovery Rate of Adsorption Capacity) The sample after the evaluation of the initial adsorption capacity was subjected to a regeneration treatment by heating. Specifically, the sample after adsorption contains 400 ml / mi of 60 RH% clean air containing no acetaldehyde or the like.
The sample was heated while continuously flowing at n and kept at 120 ° C. for 1 hour. Thereafter, for the sample after the regeneration treatment, the adsorption capacity of acetaldehyde was evaluated by the same method as described above, and the adsorption capacity recovery rate was calculated from the ratio of the adsorption capacity after the regeneration treatment to the initial adsorption capacity.

(Determination of Acetaldehyde Desorption) Whether or not the adsorbed acetaldehyde was desorbed during the above regeneration treatment was examined as follows. The entire amount of the regeneration gas after passing through the sample was passed through a gas absorption bottle containing an acetaldehyde collecting solution (a phosphoric acid solution of 2,4-dinitrophenylhydrazine) and concentrated. After completion of the regeneration treatment for 1 hour, the collected solution was transferred to a separatory funnel, a certain amount of chloroform was added thereto, and the mixture was vigorously shaken. After standing, the chloroform layer was taken out and analyzed by gas chromatography. When acetaldehyde was contained in the regeneration gas after passing through the sample, a peak of acetaldehyde-2,4-dinitrophenylhydrazone was observed, and it was judged that acetaldehyde had been eliminated.

(Measurement method of specific surface area) Nitrogen gas adsorption BE
The measurement of the specific surface area by the T method is performed using ASAP2 manufactured by Shimadzu Corporation.
010 apparatus. Sample weight is 0.2-0.8g
And dried under reduced pressure at 120 ° C. for 3 hours as a pretreatment before measurement. The measured nitrogen pressure is P / P0 = 0.05-0.2
Nine points were given in the range of 0.

(Example 1) 6 g of copper sulfate pentahydrate, 22 g of cobalt sulfate heptahydrate and 0.6 g of cerium nitrate hexahydrate were dissolved in 500 ml of distilled water to prepare a metal salt solution. While stirring the mixture at room temperature, a 20% aqueous sodium carbonate solution was added dropwise until the pH of the metal salt solution reached 9, to obtain a coprecipitate. This was separated by suction filtration and then washed with about 2 liters of warm water at about 70 ° C. This one
After drying at 20 ° C., it was baked at 280 ° C. for 3 hours. The obtained inorganic compound was pulverized to obtain a sample of Example 1. The specific surface area measured by the nitrogen gas adsorption BET method was 145 m ² / g.

(Example 2) 6 g of copper sulfate pentahydrate, 11 g of nickel sulfate hexahydrate, 11 g of cobalt sulfate heptahydrate,
0.5 g of lanthanum nitrate hexahydrate was dissolved in 500 ml of distilled water to obtain a metal salt solution. While stirring this at room temperature,
A 20% aqueous solution of sodium carbonate was added to the pH of the metal salt solution.
To 9 to obtain a coprecipitate. After stirring was continued for about 1 hour, the coprecipitate was separated by suction filtration, and then washed with about 2 liters of about 70 ° C. warm water. This is 12
After drying at 0 ° C., it was baked at 280 ° C. for 3 hours. The obtained inorganic compound was pulverized to obtain a sample of Example 2. The specific surface area measured by the nitrogen gas adsorption BET method was 196 m ² / g.

Example 3 30 g of manganese sulfate pentahydrate
And 0.6 g of strontium nitrate were dissolved in 500 ml of distilled water to obtain a metal salt solution. While stirring this at room temperature,
A 20% aqueous solution of sodium carbonate was added to the pH of the metal salt solution.
To 9 to obtain a coprecipitate. This was separated by suction filtration and then washed with about 2 liters of warm water at about 70 ° C. This was dried at 120 ° C. and fired at 280 ° C. for 3 hours. The obtained inorganic compound was pulverized to obtain a sample of Example 3. The specific surface area measured by the nitrogen gas adsorption BET method was 220 m ² / g.

Comparative Example 1 An inorganic compound was prepared in exactly the same manner as in Example 1 except that 0.6 g of cerium nitrate hexahydrate was not added. And The specific surface area measured by the nitrogen gas adsorption BET method was 143 m ² / g.

Comparative Example 2 6 g of copper sulfate pentahydrate, 22 g of cobalt sulfate heptahydrate and 0.6 g of cerium nitrate hexahydrate were dissolved in 500 ml of distilled water to prepare a metal salt solution. While stirring the mixture at room temperature, a 20% aqueous sodium hydroxide solution was added dropwise until the pH of the metal salt solution reached 9, to obtain a coprecipitate. This is separated by suction filtration,
Next, washing was performed with about 2 liters of hot water at about 70 ° C. This was dried at 120 ° C. and fired at 280 ° C. for 3 hours. The obtained inorganic compound was ground to obtain a sample of Comparative Example 2. The specific surface area measured by the nitrogen gas adsorption BET method was 17 m ² / g.

Comparative Example 3 2.4 g of copper nitrate pentahydrate and 9 g of cobalt nitrate heptahydrate were dissolved in 30 ml of distilled water to prepare a metal salt solution. This was impregnated with 6 g of hydrophobic zeolite (silica / alumina ratio = 400), dried at 120 ° C., and calcined at 280 ° C. The copper / cobalt oxide-supported hydrophobic zeolite (supporting amount: 21 parts by weight) thus obtained was used as a sample of Comparative Example 3. The specific surface area measured by the nitrogen gas adsorption BET method was 180 m ² / g.

With respect to these samples, the initial adsorption capacity of acetaldehyde, the recovery rate of the adsorption capacity after the regeneration treatment, and the presence or absence of acetaldehyde desorption were evaluated by the methods described above. In all of Examples 1 to 3, the initial adsorption capacity was large, and
It was confirmed that the adsorption ability was recovered by the regeneration treatment at ° C. In these examples, since no acetaldehyde was desorbed during the regeneration treatment, it can be determined that the recovery of the adsorption ability was due to the decomposition of acetaldehyde.
On the other hand, in Comparative Examples 1 and 2, the initial adsorption capacity was considerably small, and therefore, the recovery rate of the adsorption capacity after regeneration could not be evaluated. In Comparative Example 3, desorption of acetaldehyde was observed in the heat regeneration treatment. It is considered that the adsorbed acetaldehyde was desorbed during the heating process before being decomposed.

[0034]

[Table 1]

[0035]

As described above, the aldehyde-adsorbing / decomposing agent of the present invention has excellent aldehyde-adsorbing ability at a low temperature in the presence of steam. In addition, by performing the heat treatment at a relatively low temperature after the adsorption, the aldehydes once adsorbed are decomposed without being desorbed, and the adsorbability can be recovered. Therefore, excellent removal ability can be maintained for a long period of time even in an environment where steam is present as in a normal living space and high-temperature treatment is difficult.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B01D 53/38 B01J 20/30 53/81 23/34 A 53/86 23/76 A B01J 20/28 37 / 03 Z 20/30 37/16 23/34 F24F 7/00 A 23/76 B01D 53/34 ZAB 37/03 116B 37/16 53/36 H F24F 7/00 F term (reference) 4C080 AA05 BB02 CC02 HH05 JJ01 KK08 MM02 QQ03 QQ17 4D002 AA32. FA22 FA37 GA01 4G069 AA03 BC08A BC12B BC29A BC31A BC31B BC38A BC42B BC43B BC62A BC62B BC67A BC67B BC68A BC68B CA04 CA10 CA17 DA06 EA01Y EC02X EC03X EC03Y EC04X EC05X FB08 FB39 FC03

Claims (7)

[Claims] 1. A specific surface area of an inorganic compound containing at least one element selected from Groups 2a and 3a of the periodic table, as measured by a nitrogen gas adsorption BET method, is 50 m ² /
g or more. 2. The aldehyde-adsorbing / decomposing agent according to claim 1, wherein the content of the element relative to the total amount of the inorganic compound is from 0.1% by weight to 10% by weight in terms of oxide. 3. The aldehyde-adsorbing / decomposing agent according to claim 1, wherein the inorganic compound contains at least one transition metal. 4. The aldehyde-adsorbing and decomposing agent according to claim 1, wherein the inorganic compound contains at least one element selected from manganese, cobalt, nickel, and copper. 5. An air purifying filter and / or an air purifier equipped with the aldehyde-adsorbing / decomposing agent according to any one of claims 1 to 4. 6. A method for producing an aldehyde adsorptive / decomposer comprising an inorganic compound, comprising using an alkali from a metal salt mixed solution containing at least one element selected from Groups 2a and 3a of the periodic table. The method for producing an aldehyde-adsorbing and decomposing agent according to any one of claims 1 to 5, wherein a precipitate is formed, separated from the solution, and further subjected to an oxidation treatment. 7. The production method according to claim 6, wherein the alkali in the production method is a carbonate compound.