JP4678864B2 - GAS ADSORBENT, ITS MANUFACTURING METHOD, AND GAS ADSORPTION FILTER - Google Patents

Description

  The present invention relates to an acidic gas adsorbent and an acidic gas adsorption filter used for adsorbing and removing acidic gases such as acetaldehyde.

Adsorbents for removing acidic gases such as acetaldehyde in air not only use the physical adsorption action of adsorbents such as activated carbon, but also improve the adsorption performance by chemically treating the adsorbent surface. It has been performed conventionally.
As a method for improving such adsorption performance, a method of treating the surface of activated carbon with an oxidizing agent such as ozone (see Patent Document 1) and a method of supporting a basic compound such as an amino group-containing compound on a carrier are known. Yes.
Further, when the amino group-containing compound is supported on the carrier, the amino group-containing organosilicon compound is used, and the silanol group is bonded to the hydroxyl group on the carrier surface to firmly attach the amino group-containing organosilicon compound to the carrier surface. A method of improving adsorption performance by chemically reacting a basic amino group and an acidic gas is also known (see Patent Documents 2 to 5). According to this method, the adsorption performance is improved over physical adsorption, but the amount of silanol bonds is limited by the amount of hydroxyl groups on the surface of the carrier, which limits the amount of amino group-containing organosilicon compound that can be attached. There is also a limit to the improvement of adsorption performance.

Japanese Patent Laid-Open No. 11-188258 Japanese Patent No. 3489136 Japanese Patent No. 3430955 Japanese Patent No. 3455000 JP-A-8-257346

  An object of the present invention is to solve the above-mentioned problems of the prior art, and to improve the adsorption performance of a gas adsorbent used for adsorbing and removing acidic gases such as acetaldehyde. Furthermore, another object of the present invention is to provide a method for producing such a gas adsorbent with improved adsorption performance, and a gas adsorption filter.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention, when attaching an amino group-containing organosilicon compound to a support, by treating the support with an alkali in advance, the amount of the amino group-containing organosilicon compound attached Has been found to be able to be increased, leading to the present invention. More specifically, by subjecting the carrier to alkali treatment in advance, the number of hydroxyl groups on the surface of the carrier is increased. The inventor has arrived at the present invention based on the idea that the amount of chemical adsorption of acid gas can be improved.
That is, the present invention relates to the following inventions.
(1) A gas adsorbent obtained by reacting an alkali-treated carrier with an amino group-containing organosilicon compound.
(2) Alkali treatment is a compound comprising the group of alkali metal salts or hydroxides, alkaline earth metal hydroxides or carboxylates, ammonia, aliphatic amines, aromatic amines, and amino group-containing polymer compounds. The gas adsorbent according to the above (1), which is a treatment by any one or more kinds.
(3) The gas adsorbent according to (2) above, wherein the alkali metal salt is any one of potassium carbonate, tripotassium phosphate, potassium silicate, sodium bicarbonate, sodium carbonate, sodium sulfite, and sodium acetate.
(4) The gas adsorbent according to (2) above, wherein the alkali metal hydroxide is any one of potassium hydroxide, sodium hydroxide, and lithium hydroxide.
(5) The gas adsorbent according to (2) above, wherein the alkaline earth metal hydroxide is either calcium hydroxide or barium hydroxide.
(6) The gas adsorbent according to (2) above, wherein the alkaline earth metal carboxylate is calcium acetate.
(7) The gas adsorbent according to (2) above, wherein the aliphatic amine is either methylamine or dimethylamine.
(8) The gas adsorbent according to (2), wherein the aromatic amine is either aniline or aminobenzenesulfonic acid.
(9) The gas adsorbent according to the above (2), wherein the amino group-containing polymer compound is any of polyallylamine, polyallylamine hydrochloride, polyethyleneimine, polyacrylamide, and chitosan.
(10) The gas adsorbent according to any one of (1) to (9), wherein the amino group-containing organosilicon compound is a compound containing one or more amino groups and a hydroxyl group or alkoxy group bonded to silicon.
(11) The gas adsorbent according to the above (10), which is an amino group-containing organosilicon compound in which an amino group and silicon are bonded with a saturated hydrocarbon.
(12) The gas adsorbent according to (10), wherein the silicon-bonded alkoxy group is a methoxy group, an ethoxy group, an isopropoxy group, or a butoxy group.
(13) The amino group-containing organosilicon compound is any one or more of 3-aminopropyltrimethoxysilane, 3-aminopropyltrihydroxysilane, and 3-aminopropyltriethoxysilane, as described in (10) or (11) above Gas adsorbent.
(14) The gas adsorbent according to any one of (1) to (13), wherein the carrier is activated carbon or an inorganic oxide.
(15) The gas adsorbent according to (14), wherein the inorganic oxide is at least one of silica, alumina, titania, zirconia, and molecular sieve.
(16) A method for producing a gas adsorbent, comprising subjecting a carrier to alkali treatment and then drying, and then immersing and drying the alkali-treated carrier in an aqueous solution containing an amino group-containing organosilicon compound.
(17) The method for producing a gas adsorbent according to the above (16), wherein the alkali treatment comprises immersing the carrier in an alkaline solution.
(18) The method for producing a gas adsorbent according to the above (17), wherein the concentration of the alkali solution is 80% by weight or less.
(19) A gas adsorption filter in which the gas adsorbent according to any one of (1) to (15) is supported on a support.
(20) A gas adsorption filter obtained by sandwiching the gas adsorbent according to any one of (1) to (15) above in a nonwoven fabric.
(21) The gas adsorption filter according to the above (19) or (20), wherein the gas adsorption filter is a cabin air filter for automobile interior cleaning.

  According to the present invention as described above, the amount of acid gas adsorbed can be remarkably increased in the gas adsorbent and filter used for adsorbing and removing acid gas such as acetaldehyde.

The present invention will be specifically described below, but the present invention is not limited thereto.
The gas adsorbent and filter of the present invention can be used for cleaning air containing acid gas, particularly indoor air. In particular, the gas adsorbent and the filter of the present invention are effective for use in cleaning the air inside the automobile.

  Examples of acidic substances that pollute air include hydrogen sulfide, sulfurous acid gas, aldehydes, and organic acids. The adsorbent of the present invention is particularly effective for removing aldehydes such as formaldehyde and acetaldehyde, and organic acids such as acetic acid. It is. Formaldehyde is mainly a new building material, acetaldehyde and acetic acid are the main sources of tobacco, especially indoor air pollutants.

The amino group-containing organosilicon compound used in the present invention is preferably a compound containing one or more amino groups and a hydroxyl group or alkoxy group bonded to silicon. The amino group chemically reacts with an acidic substance and has a chemisorption action. The hydroxyl group or alkoxy group bonded to silicon reacts with the hydroxyl group on the surface of the carrier to form a silanol bond.
The amino group-containing organosilicon compound is more preferably one in which an amino group and silicon are bonded with a saturated hydrocarbon, and the alkoxy group bonded to silicon is preferably a methoxy group, an ethoxy group, an isopropoxy group, or a butoxy group.
Preferred amino group-containing organosilicon compounds include 3-aminopropyltrihydroxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, etc., and 3-aminopropyltrimethoxysilane (APTMS) is preferred. Most preferred.

  The carrier that can be used in the present invention is an inorganic oxide such as activated carbon, silica, alumina, titania, zirconia, or molecular sieve. Among them, activated carbon is particularly preferable.

  Examples of the alkali for treating the carrier include potassium carbonate, tripotassium phosphate, potassium silicate, sodium hydrogen carbonate, sodium carbonate, sodium sulfite, sodium acetate and other alkali metal salts, potassium hydroxide, sodium hydroxide, lithium hydroxide. Alkali metal hydroxides such as, alkaline earth metal hydroxides such as calcium hydroxide and barium hydroxide, alkaline earth metal carboxylates such as sodium acetate and calcium acetate, methylamine and dimethylamine Amino group-containing polymer compounds such as aromatic amines such as aliphatic amine, aniline and aminobenzene sulfonic acid, polyallylamine, polyallylamine hydrochloride, polyethyleneimine, polyacrylamide and chitosan are exemplified, but potassium hydroxide (KOH) Is particularly preferred.

The mechanism of the adsorbent of the present invention will be described using 3-aminopropyltrimethoxysilane (APTMS) as the amino group-containing organic compound, KOH as the alkali, and acetaldehyde as the acidic substance to be treated.
FIG. 1 shows a reaction mechanism between an amino group-containing organosilicon compound and acetaldehyde. The acetaldehyde is chemically adsorbed on the adsorbent by the reaction of the amino group of the amino group-containing organosilicon compound with acetaldehyde to form a Schiff base.

  The generation mechanism of the silanol bond by the amino group-containing organosilicon compound and the hydroxyl group on the support surface is shown in FIG. In the prior art, only the surface hydroxyl groups originally possessed by carrier materials such as silica particles contribute to silanol bonding.

The greatest feature of the present invention is to increase the surface hydroxyl groups of the support by subjecting the support to an alkali treatment in advance. A case where activated carbon is a carrier will be described with reference to FIG.
On the activated carbon surface, there are free hydroxyl group, carboxyl group, lactone group, quinone group and the like. A free hydroxyl group and a carboxyl group can form a silanol bond with an amino group-containing organosilicon compound, but a lactone group or a quinone group cannot form a silanol bond.
In the present invention, by subjecting activated carbon to alkali treatment in advance, as shown in FIG. 3, lactone groups and quinone groups are hydrolyzed, and the number of hydroxyl groups capable of forming silanol bonds increases.

The gas adsorbent of the present invention can be produced by immersing the support in an alkaline solution and then drying, and then immersing and drying the alkali-treated support in an aqueous solution containing an amino group-containing organic compound. .
The concentration of the alkaline solution is preferably 80% by weight or less, and more preferably about 5% by weight. As the solvent for the alkaline solution, water or water-alcohols is used. As alcohols used, alcohols that are soluble in water, such as methanol, ethanol, 1-propanol, and 2-propanol, are preferable.
The concentration of the aqueous solution containing the amino group-containing organosilicon compound is not particularly limited, but is preferably about 16% by weight.
When the carrier is immersed in the alkaline solution, it is preferable to add the carrier to the alkaline solution and stir. In addition, it is preferable to stir with an agitator or ultrasonic waves in the immersion treatment with an aqueous solution containing an amino group-containing organosilicon compound.

Hereinafter, the optimum production conditions of the gas adsorbent of the present invention will be described by way of examples.
Evaluation Method of Adsorption Capacity In the following examples, the evaluation of adsorption capacity was performed as follows (see FIG. 4).
A predetermined amount of adsorbent is placed in a 9-liter chamber (sealed container). Air containing acetaldehyde having a predetermined concentration (initial concentration) is introduced into the chamber, and the fan is started so that the adsorbent placement portion can be ventilated to start adsorption. After 30 minutes, the acetaldehyde concentration in the chamber is measured.
Removal rate = (initial concentration−concentration after 30 minutes) / concentration after 30 minutes and / or the integrated adsorption capacity calculated from the total amount of concentration change is used to evaluate the adsorption capacity.

Production method of adsorbent KOH is added to a solution in which isopropyl alcohol (IPA) and water are mixed at a ratio of 3: 2. The KOH concentration is adjusted to 3 to 45% by weight. Activated carbon is added to the KOH solution and stirred. After stirring, it was filtered and dried at 90 ° C. for 24 hours.
Next, an aqueous solution of 0.25 to 64% by weight of 3-aminopropyltrimethoxysilane (APTMS) is prepared, and the activated carbon subjected to the KOH treatment is added. After stirring, it was filtered and dried at 90 ° C. for 24 hours to produce an adsorbent.
Further, an adsorbent was produced in the same manner by changing KOH to K ₂ CO ₃ .

Influence of Alkaline Solution In the above production method, the adsorption ability was evaluated by changing the concentration of the alkali solution. A KOH solution was used as the alkaline solution, and the concentration of the APTMS aqueous solution was fixed at 1 wt% at 0.1 wt%, 1 wt%, and 5 wt%. As a control, an adsorbent treated with only 1% by weight of an aqueous APTMS solution without using an alkali treatment was prepared. FIG. 5 shows the result of repeated evaluation four times by the above-described evaluation method using 0.2 g of the adsorbent.
From the result of FIG. 5, it was found that the adsorption ability is improved by performing the KOH treatment than when the alkali treatment is not performed.

Examination of the effect of production conditions on adsorption capacity (1)
Based on the results in Example 1, optimum production conditions were examined. The evaluation system was as shown in the above-mentioned method of evaluating the adsorption capacity, and 0.1 g of adsorbent was placed on a 1.5 cm diameter cylinder, that is, the adsorbent amount was evaluated at 565 g / m2.
With respect to the influence factors of the KOH concentration, the stirring time at the time of KOH treatment, the APTMS concentration, and the APTMS stirring strength (stirring bar), the production conditions were changed according to the levels shown in Table 1, and the contribution degree of the influence factors was analyzed. As a result, it was found that the APTMS concentration had a large influence on the acetaldehyde adsorption capacity. FIG. 6 illustrates the estimation of the factor effect. From these results, it was estimated that the KOH concentration of 5% by weight and the APTMS concentration of 4% by weight were optimal at the level shown in Table 1.

Examination of influence of production conditions on adsorption capacity (2)
According to Example 2, it was found that the higher the KOH concentration and the APTMS concentration in the production conditions of Example 2, the better the adsorptive capacity. Therefore, in Example 3, the KOH concentration and the APTMS concentration were further increased. The adsorption ability was tested on the concentration side. The evaluation system is the same as in Example 2.
Table 2 shows the levels of the influence factors of the KOH concentration, the stirring time during the KOH treatment, the APTMS concentration, and the APTMS stirring strength (stirring bar). As a result, it was found that the KOH concentration had a large effect on the acetaldehyde adsorption capacity.
FIG. 7 illustrates the estimation of the factor effect. From these results, it was found that a KOH concentration of 5% by weight and an APTMS concentration of 16% by weight are optimal.
In addition, A. of FIG. From the graph of KOH concentration, if the KOH concentration is 80% by weight or less, it can be estimated that there is an effect of alkali treatment.

Evaluation of BET specific surface area and pore volume of KOH-treated activated carbon In this example, we investigated how the specific surface area and pore volume of activated carbon changed by KOH treatment, and examined the optimum treatment conditions for activated carbon. did.
BET specific surface area and pore volume were measured for untreated activated carbon, activated carbon treated with 1 to 25 wt% KOH solution, and activated carbon with APTMS attached thereto. The ratio results based on untreated activated carbon are shown in FIGS.
8 and 9, it was found that the specific surface area and pore volume of both activated carbons were reduced by KOH treatment, but 4% by weight of APTMS was added to the activated carbon that had been treated by 5% by weight of KOH. Results in a slight increase in specific surface area and pore volume (AC + 5 wt% KOH vs. AC + 5 wt% KOH + 4 wt% APTMS).
As a result, when 5% by weight KOH treatment is performed, the erosion action of activated carbon is small, and many sites (OH groups) that bind to APTMS appear due to KOH treatment, which allows APTMS to be attached efficiently. Can be guessed. When the KOH concentration of Examples 2 and 3 was combined with the result that the best acetaldehyde adsorption ability was shown when the KOH concentration was 5% by weight, the specific surface area and the pore volume were large when the 5% by weight concentration KOH treatment was performed. In addition, APTMS can be efficiently attached, which is considered to be related to the excellent acetaldehyde adsorption ability.

  According to the present invention in which the carrier is treated with an alkali in advance, a larger amount of an amino group-containing organic compound can be attached to the carrier, and as a result, the adsorptive capacity is greatly increased. Therefore, a gas such as acetaldehyde could be efficiently adsorbed and removed without increasing the amount of adsorbent.

The chemical reaction (chemisorption) mechanism of an amino group-containing organosilicon compound and acetaldehyde is shown. The silanol bond between the hydroxyl group on the carrier surface and the amino group-containing organosilicon compound is shown. The reaction formula of the main functional group on the activated carbon surface and its KOH treatment is shown. An evaluation system for evaluating adsorption capacity is shown. An acetaldehyde adsorption test result (removal rate) is shown. Factor effect estimation (1) Factor effect estimation (2) The specific surface area of activated carbon is shown. The pore volume of activated carbon is shown.

Claims (8)

An aldehyde adsorbent obtained by reacting activated carbon treated with potassium hydroxide with an amino group-containing organosilicon compound. The aldehyde adsorbent according to claim 1 , wherein the amino group-containing organosilicon compound is at least one of 3-aminopropyltrimethoxysilane, 3-aminopropyltrihydroxysilane, and 3-aminopropyltriethoxysilane. After treating the activated carbon with potassium hydroxide, dried and then the production method of an aldehyde adsorbent characterized by drying and dipping the activated carbon treated with potassium hydroxide in an aqueous solution containing an amino group-containing organic silicon compound . The method according to claim 3 Symbol mounting aldehyde adsorbent characterized by dipping the carrier into an alcohol solution - Potassium hydroxide water. The method for producing an aldehyde adsorbent according to claim 3 or 4, wherein the concentration of potassium hydroxide is 80% by weight or less. A filter for aldehyde adsorption, wherein the aldehyde adsorbent according to claim 1 or 2 is supported on a support. An aldehyde adsorption filter obtained by sandwiching the aldehyde adsorbent according to claim 1 or 2 between nonwoven fabrics. The aldehyde adsorption filter according to claim 6 or 7 , wherein the aldehyde adsorption filter is a cabin air filter for automobile interior cleaning.