JP2010005584A - Adsorbent for lower aldehydes - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adsorbent which is excellent in heat stability, does not emit the odor of a carried chemical, and includes such excellent adsorptivity as to efficiently adsorb and remove lower aldehydes over a long time. <P>SOLUTION: The above problem is solved by impregnating an activated carbon with urea and a salt selected from a carbonate, phosphate or sulfate of alkali metals, and a 1-6C carboxylate and then heating the activated carbon at 45-195°C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an adsorbent that has excellent adsorption performance for lower aldehydes such as formaldehyde and acetaldehyde and does not cause a chemical odor during use.

Lower aldehydes such as formaldehyde and acetaldehyde are harmful gases that emit unique irritating odors. Formaldehyde is said to have a carcinogenicity and an allowable concentration in air as low as 0.3 ppm. In addition, C ₁ -C ₄ aliphatic lower aldehydes including acetaldehyde are designated as specific malodorous substances in Japan, and all of them are substances that have a very low olfactory threshold and cause odor pollution.
Formaldehyde generation sources include formaldehyde manufacturing plants, resin manufacturing plants made from urea, melamine, phenol, etc., processing plants for these resins, and manufacturing plants for building materials and furniture using these resins. Is mentioned. It is also contained in formaldehyde as a disinfectant, incomplete combustion exhaust gas of petroleum, and sidestream smoke of tobacco. Recently, formaldehyde generated from new building materials and furniture has become a problem even indoors.
As a source of acetaldehyde, it is generated at the time of heat treatment of sewage sludge in addition to the manufacturing plant of acetaldehyde and its derivatives, and is also contained in the mainstream smoke of cigarettes.

In recent years, harmful substances and odors have been seen as problems with these lower aldehydes from the viewpoint of improving the working environment and living environment. From this viewpoint, gas, especially lower aldehydes in the air are efficiently removed. There is a strong demand for the development of adsorbents.
Conventionally, as adsorbents for lower aldehydes, activated carbon, activated alumina, silica gel and the like have been used, and among them, activated carbon has been widely used. However, these adsorbents themselves have lower properties such as formaldehyde and acetaldehyde. There are drawbacks in that the adsorption capacity for aldehydes is small and the lifetime is short.
As an improvement measure, a compound that reacts with the lower aldehydes on the adsorbent, for example, an organic compound such as an aliphatic amine or an aromatic amine, or a platinum group compound as a catalyst is used as the adsorbent. The one supported on the substrate has been proposed.

However, adsorbents carrying organic compounds have problems with the stability of the carried organic compounds over time, their own toxicity, odor, and the like. For example, aniline (boiling point 185 ° C.) simply attached at room temperature (Patent Document 1) is suspected of causing carcinogenicity, and is unstable over time against the adsorption of lower aldehydes. Because of this, there was a problem in practical use. Further, after the activated carbon is oxidized, polyethyleneimine (aqueous solution having an ammonia odor) or p-aminoacetanilide (boiling point 267 ° C., toxic chemical) is simply attached at around room temperature (Patent Document 2). Although it has been devised, adsorbents obtained by simply attaching such amines to activated carbon at around room temperature are generally inferior in thermal stability, and depending on the usage conditions, some of the attached amines may be desorbed from the activated carbon. In addition, there are drawbacks in that the odor of amines leaks or the adsorption performance decreases.
The catalyst-supported catalyst is expensive and has a low effect of removing lower aldehydes at room temperature.
Thus, none of the conventional techniques are satisfactory for the removal of lower aldehydes.

Japanese Patent Publication No. 60-54095 Japanese Patent Laid-Open No. 9-168736

  An object of the present invention is to provide an excellent adsorbent for lower aldehydes that is excellent in thermal stability, has no odor or leakage of a supported chemical, and can efficiently adsorb and remove lower aldehydes over a long period of time. Yes.

As a result of intensive studies in view of the above points, the present inventors have impregnated activated carbon with urea and carbonic acid, phosphoric acid sulfuric acid or an alkali metal salt of C _1-6 carboxylic acid, and then heated at a temperature of 45 to 195 ° C. The adsorbent obtained in this way was found to be excellent in thermal stability, free from odor and leakage of the supported chemicals, and efficiently adsorbed and removed lower aldehydes over a long period of time, thereby completing the present invention.

The activated carbon used in the present invention may be any as long as it is activated by a normal method using charcoal, coke, coal, coconut shell, resin, or the like as a raw material. Its shape is crushed, cylindrical, spherical, honeycomb, fiber, etc., its surface area is 100 m ² / g or more, preferably 150~2500m ² / g.

Examples of the alkali metal used in the present invention include lithium, sodium, potassium, rubidium, and cesium, but sodium and calcium are conveniently used.
Examples of the alkali metal salt of carbonic acid include sodium hydrogen carbonate, sodium carbonate, potassium hydrogen carbonate, and potassium carbonate. Examples of the alkali metal salt of phosphoric acid include sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, Potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, etc., as the alkali metal salt of sulfuric acid, for example, sodium hydrogen sulfate, sodium sulfate, potassium hydrogen sulfate, potassium sulfate, etc., also C ₁ -C ₆ Examples of the alkali metal salt of carboxylic acid include sodium acetate, sodium oxalate, sodium citrate, sodium tartrate, sodium succinate, sodium lactate, potassium acetate, potassium oxalate, potassium citrate, potassium tartrate, potassium succinate, potassium lactate. And sodium salts and potassium salts of mono- or polybasic acids The
The amount of urea impregnated in the activated carbon is preferably 0.1 mmol or more, particularly 0.5 to 10.0 mmol, relative to 1 g of activated carbon.

The impregnation amount of 1 g of activated carbon of an alkali metal salt is preferably 0.01 mg atom or more, particularly 0.05 to 8 mg atom as an alkali metal.
When the activated carbon is impregnated with urea and an alkali metal salt, the urea and the alkali metal salt are previously mixed with water, an acid aqueous solution (for example, an aqueous solution of an acid such as sulfuric acid, nitric acid, phosphoric acid, sulfuric acid, C ₁ -C ₆ carboxylic acid) or alcohol. Dissolve in the activated carbon and impregnate activated carbon In the case of a compound that is not very soluble in water, these acids or their aqueous solutions, or alcohols, they may be impregnated in a suspension state.

  After impregnating with urea and an alkali metal salt, heating is performed at 45 to 195 ° C, preferably 50 to 190 ° C, particularly preferably 100 to 150 ° C. This heating can be performed in air, inert gas or combustion exhaust gas. The heating time is about 10 to 500 minutes, preferably about 20 to 240 minutes. A heating temperature of 195 ° C. or higher is not preferable because the impregnating chemical sublimates or decomposes and lowers the lower aldehyde adsorption performance.

The lower aldehydes to be removed in the present invention refer to aldehydes having 6 or less carbon atoms and a boiling point of 100 ° C. or less, such as formaldehyde, acetaldehyde, propionaldehyde, acrolein, and 3-methyl-butyraldehyde. Formaldehyde and acetaldehyde.
The present invention also includes a method for efficiently removing aldehydes by allowing the aldehyde adsorbent obtained as described above to exist in a space or in an apparatus. In the case where the aldehyde adsorbent is present in the space, for example, the aldehyde adsorbent may be formed into a sheet form, included in a building material, or a method that is usually performed. Moreover, when it exists in an apparatus etc., the method etc. which fill a tower, a container, etc., and ventilate the gas containing aldehydes to these are considered.

  The aldehyde adsorbent of the present invention is prepared by impregnating activated carbon with urea and an alkali metal salt, which is an odorless and chemically stable solid chemical at room temperature, and heating at a temperature of 45 to 195 ° C. In the vicinity of room temperature using an aldehyde adsorbent, the impregnating chemical vapor does not leak, and is chemically stable, adsorbing and removing aldehydes is good, and there is no deterioration over time. Very superior to adsorbents.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

8g to 32 mesh bituminous coal-based activated carbon A (BET specific surface area 1150m ² / g) 2g each, urea 167mg / ml aqueous solution, urea 167mg · potassium carbonate 40mg / ml aqueous solution, urea 167mg · potassium dihydrogen phosphate 60mg / ml, urea 167 mg, dipotassium hydrogen phosphate 77 mg / ml, urea 167 mg, potassium triphosphate 94 mg / ml, urea 167 mg, sodium dihydrogen phosphate 51 mg / ml, urea 167 mg, tripotassium citrate-130 mg / ml, urea 167 mg, tricitrate Sodium-110 mg / ml, urea 167 mg / sodium hydrogen sulfate-65 mg mg / ml, urea 167 mg / potassium hydrogen sulfate-70 mg / ml, urea 167 mg / sodium bicarbonate-49 mg / ml were each impregnated uniformly. Regarding the amount of chemical impregnation into activated carbon, the amount of chemical per gram of activated carbon was as shown in the following table. The chemical impregnated activated carbon thus obtained was heated at 110 ° C. for 30 minutes. These were finely pulverized in a mortar, and 100 mg each was weighed into a 3 L tetra bag and filled with air. A predetermined amount of formalin aqueous solution was injected into each tetrabag to adjust the formaldehyde concentration in each tetrabag to 300 ppm. The results of measuring the formaldehyde concentration in each tetrabag after 3 hours are as shown in Table 1.

8-32 mesh coconut shell activated carbon (BET specific surface area 1200 m ² / g) M with urea 60 mg / ml aqueous solution, urea 60 mg / potassium carbonate 14 mg / ml aqueous solution, urea 60 mg / potassium carbonate 28 mg / ml aqueous solution, urea 60 mg / carbonic acid Potassium 56 mg / ml aqueous solution, urea 60 mg / potassium dihydrogen phosphate 14 mg / ml, urea 60 mg / potassium dihydrogen phosphate 10 mg / ml, urea 60 mg / potassium triphosphate 10 mg / ml, urea 60 mg / sodium dihydrogen phosphate 12 mg / ml, 2 ml each of 60 mg of urea and 15 mg of tripotassium citrate were impregnated uniformly. Regarding the amount of chemical impregnation into activated carbon, the amount of chemical per gram of activated carbon was as shown in the following table. The chemical impregnated activated carbon thus obtained was heated at 100 ° C. for 30 minutes. These were finely pulverized in a mortar, and 100 mg each was weighed into a 3 L tetra bag and filled with air. A predetermined amount of formalin aqueous solution was injected into each tetrabag to adjust the formaldehyde concentration in each tetrabag to 300 ppm. The results of measuring the formaldehyde concentration in each tetrabag after 3 hours are shown in Table 2.

  2 g of 8-32 mesh bituminous coal-based activated carbon A was uniformly impregnated with 2 ml each of urea 167 mg / ml aqueous solution and urea-167 mg / potassium dihydrogen phosphate-60 mg / ml. Regarding the amount of chemicals per 1 g of activated carbon, the former was 167 mg of urea, and the latter was 167 mg of urea / 60 mg of potassium dihydrogen phosphate. The chemical impregnated activated carbon thus obtained was heated at 40 ° C., 50 ° C., 100 ° C., 150 ° C., 190 ° C., and 200 ° C. for 60 minutes, respectively. These were finely pulverized in a mortar, and 100 mg each was weighed into a 3 L tetra bag and filled with air. A predetermined amount of formalin aqueous solution was injected into each tetrabag to adjust the formaldehyde concentration in each tetrabag to 300 ppm. The results of measuring the formaldehyde concentration in each tetrabag after 3 hours are shown in Table 3.

  As is clear from Table 3, the adsorbent (control) in which only activated urea was impregnated into activated carbon hardly adsorbed and removed formaldehyde. Further, among adsorbents mixed and impregnated with urea and potassium dihydrogen phosphate, adsorbents having a heating temperature of 40 ° C. or 200 ° C. can adsorb and remove formaldehyde to some extent, but performance is insufficient. On the other hand, among the adsorbents mixed and impregnated with urea and potassium dihydrogen phosphate, the adsorbent having a heating temperature of 50 to 200 ° C. (the present invention) exhibited very excellent adsorption performance for formaldehyde.

  The lower aldehyde adsorbent of the present invention is excellent in thermal stability, has no odor of supported chemicals, and has an excellent adsorbing ability by efficiently removing and removing lower aldehydes over a long period of time. In addition to manufacturing factories and manufacturing factories for resins made from urea, melamine, phenol, etc., processing factories for these resins, manufacturing factories for building materials and furniture using these resins, and a manufacturing plant for acetaldehyde and its derivatives It can be used as an adsorbent for lower aldehydes in heat treatment plants for sewage sludge.

Claims (3)

An adsorbent for lower aldehydes obtained by impregnating activated carbon with urea and an alkali metal salt of carbonic acid, phosphoric acid, sulfuric acid or a C ₁ -C ₆ carboxylic acid and then heating at a temperature of 45 to 195 ° C.   The adsorbent for lower aldehydes according to claim 1, wherein the alkali metal salt is a carbonate.   The adsorbent for lower aldehydes according to claim 1, wherein the alkali metal salt is a salt of phosphoric acid.