JP2002028489A - Adsorption and decomposition agent of aldehydes and producing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adsorption and decomposition agent of aldehydes which is excellent in the adsorptivity of aldehydes near the normal temperature and under the presence of water vapor, decomposes the aldehydes once adsorbed without liberating the same by heating processing at a relatively low temperature and enables to recover the adsorptivity. SOLUTION: This adsorption and decomposition agent of aldehydes comprises an inorganic compound which contains at least one kind of element selected from the Period Table group IIa and group IIIa and at least one kind of the transition metal. Further, this method for producing the adsorption and decomposition agent of aldehydes features that a precipitate is prepared by using both of alkali and acid from a mixed solution of metallic salts which includes at least one kind of element select from the Period Table group IIa and group IIIa and at least one kind of the transition metal, is separated from the solution and, further, is subjected to oxidation treatment. In addition, this air cleaning filter and/or air cleaner features that the said adsorption and decomposition agent is mounted thereon.

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, and exhaust gas. It can be used for a processing device.

[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.
Aldehydes adsorbing and decomposing agent comprising an inorganic compound containing at least one element selected from Group 3a and Group 3a.

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.

A preferred embodiment of the aldehyde-adsorbing / decomposing agent of the present invention is a method for adsorbing nitrogen gas on the inorganic compound.
An aldehyde-adsorbing / decomposing agent having a specific surface area of 50 m ² / g or more as measured by the ET method.

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 both an alkali and an acid to form a precipitate, separating the precipitate from the solution, and further performing an oxidation treatment. It is a manufacturing method.

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

Further, a preferred embodiment of the present invention is a production method wherein the acid in the production method is oxalic acid.

Further, a preferred embodiment of the present invention is a production method in which the amount of oxalic acid added in the production method is 0.1 to 1 in terms of a molar ratio with respect to the amount of the raw material metal.

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 considered to be because charges are unbalanced at structural defects and the like which are considered to be sites for adsorption and decomposition of aldehydes, and water molecules having polarities larger 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 complexed, the state of charge imbalance is alleviated, thereby inhibiting water adsorption capacity and promoting adsorption of the gas to be removed. . As the element selected from the 2a group and the 3a group of the periodic table, strontium, barium, scandium, yttrium, lanthanum, and cerium are particularly preferable.

In the present invention, the content of the element selected from Groups 2a and 3a of the periodic table is 0.1 to 10% by weight in terms of oxide based on the total amount of the inorganic compounds. 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 / 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 aqueous alkali solution and an aqueous acid solution are both 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. It can be obtained by oxidation treatment. As the alkali, a carbonate compound is preferable, and examples thereof include sodium carbonate and potassium carbonate. Oxalic acid is preferred as the acid.

The effect of the addition of oxalic acid in the production method of the present invention is mainly to increase the specific surface area. When alkali carbonate and oxalic acid are used in combination as a precipitant, the amount of oxalic acid added is 0.1 to 1, preferably 0.2 to 0.8 in terms of molar ratio with respect to the amount of the raw material metal. Within this range, the specific surface area after the oxidation treatment is improved by about ²⁰ to 100 m ² / g as compared with the case where oxalic acid is not added. If the amount is less than this, the effect is not sufficient, and if it is too large, the specific surface area tends to decrease. The order of adding alkali carbonate and oxalic acid is
Alternatively, either one of them may be alternately used, but it is necessary to adjust the final pH of the solution by adding an alkali carbonate so that the final pH becomes 7.5 or more, preferably 8 or more. The precipitate thus obtained becomes a complex of carbonate and oxalate, and it is presumed that this special composite composition contributes to the improvement of the specific surface area of the adsorptive decomposer.

The oxidation treatment in the production method of the present invention includes:
There are a method of performing liquid phase oxidation using an oxidizing agent and a method of baking in air, and 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 purification filter or an air purifier, and can be used for air purification in homes, offices, living spaces such as 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 aldehydes-adsorbing / decomposing agent of the present invention can adsorb aldehydes mainly by chemical adsorption, decompose them by heating, and regenerate 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 by way of 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 initial adsorption capacity evaluation 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 strontium nitrate 0.1 g were prepared.
6 g was dissolved in 500 ml of distilled water to obtain solution A. Separately, 6 g of oxalic acid dihydrate was dissolved in 200 ml of water to obtain a solution B. At this charge, the molar ratio of oxalic acid to metal element is about 0.5. While stirring the solution A at room temperature, a 20% aqueous sodium carbonate solution was added dropwise until the pH of the metal salt solution became 8.5, and then the solution B was gradually added. Thereafter, a 20% aqueous sodium carbonate solution was further added dropwise until the pH of the metal salt solution reached 9, to obtain a precipitate. In this state, stirring was continued for about 30 minutes to mature the precipitate. Thereafter, the precipitate is separated by suction filtration, and then heated water of about 70 ° C. for about 2 hours.
Washed with liter. After drying at 120 ° C.,
Calcination was performed at 3 ° 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 191 m ² / g.

Comparative Example 1 An inorganic compound was prepared in the same manner as in Example 1 except that 0.6 g of strontium nitrate was not added, and used as a sample of Comparative Example 1. The specific surface area measured by the nitrogen gas adsorption BET method was 185 m ² / g.

Comparative Example 2 An inorganic compound was prepared in exactly the same manner as in Example 1 except that a 20% aqueous sodium hydroxide solution was used instead of the 20% aqueous sodium carbonate solution. The sample of Example 2 was used.
The specific surface area measured by the nitrogen gas adsorption BET method is 27 m ² /
g.

Comparative Example 3 In Example 1, a precipitate was formed by adding only a 20% aqueous solution of sodium carbonate without adding oxalic acid in the step of forming a precipitate. Final p of solution
H. The procedure thereafter was exactly the same as in Example 1 to produce an inorganic compound, which was used as a sample of Comparative Example 3. The specific surface area measured by the nitrogen gas adsorption BET method was 145 m ² / g.

Comparative Example 4 In Example 1, the composition of Solution B was changed to a solution in which 25 g of oxalic acid dihydrate was dissolved in 400 ml of water. At this charge, the molar ratio of oxalic acid to metal element is about 2. Except for this, an inorganic compound was produced in exactly the same manner as in Example 1 and used as a sample of Comparative Example 4.
The specific surface area measured by the nitrogen gas adsorption BET method was 42 m ² /
g.

Comparative Example 5 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 thus obtained copper / cobalt oxide-supported hydrophobic zeolite (supporting amount: 21 parts by weight) was used as a sample of Comparative Example 5. 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 Example 1, it was confirmed that the initial adsorption capacity was large and the adsorption ability was recovered by the regeneration treatment at 120 ° C. Since no desorption of acetaldehyde was observed 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, Comparative Example 1, Comparative Example 2, and Comparative Example 4
Has a very small initial adsorption capacity, and therefore cannot be evaluated for the recovery rate of the adsorption capacity after regeneration. Comparative Example 3
In Example 1, the specific surface area was smaller than that in Example 1, thereby reducing the initial adsorption capacity. Comparing Example 1 with Comparative Example 3, the effect of adding oxalic acid is apparent. In Comparative Example 5, desorption of acetaldehyde was observed in the heat regeneration treatment. It is considered that the adsorbed acetaldehyde was desorbed in the heating process before being decomposed.

[Table 1]

[0038]

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.

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Claims (9)

[Claims] 1. An aldehyde-adsorbing / decomposing agent comprising an inorganic compound containing at least one element selected from Groups 2a and 3a of the periodic table, wherein the content of the element with respect to the total amount of the inorganic compound is oxide. 0.1% by weight or more in conversion
An aldehyde-adsorbing / decomposing agent characterized by being at most 10% by weight. 2. The aldehyde-adsorbing / decomposing agent according to claim 1, wherein the inorganic compound contains at least one transition metal. 3. 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. 4. The aldehyde-adsorbing / decomposing agent according to claim 1, wherein the specific surface area measured by a nitrogen gas adsorption BET method is 50 m ² / g or more. 5. An air purifying filter and / or an air purifier, wherein any one of the aldehyde-adsorbing and decomposing agents according to claim 1 is mounted. 6. A method for producing an aldehyde adsorptive decomposer comprising an inorganic compound, comprising the steps of: converting an alkali and an acid from a mixed solution of a metal salt containing at least one element selected from Groups 2a and 3a of the periodic table. Used together to form a precipitate,
This is separated from a 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. 8. The production method according to claim 6, wherein the acid in the production method is oxalic acid. 9. The amount of oxalic acid added in the production method,
9. The method according to claim 8, wherein the molar ratio is from 0.1 to 1.0 based on the amount of the raw metal.