JP3578259B2 - Decomposition and removal of formaldehyde in air - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for decomposing and removing gaseous formaldehyde generated from building materials, furniture, burning appliances and the like and contaminating indoor air.
[0002]
[Prior art]
As a method of removing formaldehyde in the air, a conventional method of absorbing and absorbing hydrogen peroxide or hypochlorous acid with an alkali aqueous solution (Yasuyuki Misaka, Masaru Uraki, Masaaki Matsushita: Air Conditioning and Sanitary Engineering, Vol. 40, p. 1119) (1966)), a method of removing with a physical adsorbent such as granular activated carbon, zeolite, etc., calcium peroxide (Jiro Takano, Akira Saito, Takashi Yasuoka, Sunmei Shinshin: Pollution and Countermeasures, Vol. 17, p. 1109 (1981)) ), Polyethylene imine (Gesser, HD, Fu, S .: Environ. Sci. Technol., Vol. 24, p. 495 (1990)), ammonium sulfate (Japanese Patent No. 829955), and the like. Cerium oxide (Li, C. et al .: J. Catal., Vol. 125, p. 445 (19) 0)) was added thermal energy (heat catalyst) method of decomposing formaldehyde and the like are known as.
[0003]
[Problems to be solved by the invention]
Of the above methods, the oxidative absorption method using an aqueous solution of hydrogen peroxide or hypochlorous acid is complicated because the chemical liquid is a liquid, the processing apparatus is complicated, and there is also a problem of mist generation. Not suitable. The method of removing with a physical adsorbent such as granular activated carbon and zeolite has a problem that once the adsorbent changes its storage state after the adsorption treatment, formaldehyde once adsorbed is released into the air again according to the relation of adsorption equilibrium. This phenomenon can occur not only in physical adsorption but also in chemical adsorption. A thermal catalyst is effective for decomposing formaldehyde, but has a problem that a heat source (energy source) is required. An object of the present invention is to provide a method for easily removing, decomposing and detoxifying formaldehyde in air, which is easy to handle and does not require a heat source (energy source).
[0004]
[Means for Solving the Problems]
As a result of various searches for a formaldehyde decomposing / removing agent in order to achieve the above object, the present inventors have found a powdery compound which decomposes formaldehyde gas into carbon dioxide at room temperature, and has completed the present invention. That is, in the present invention, the formaldehyde-containing air is (1) a mixture of manganese oxide particles and cerium oxide particles, wherein the cerium oxide particles contain 20 to 50% by weight of a manganese oxide-containing material.
(2) manganese oxide-containing materials of manganese oxide particles and silver oxide particles,
(3) contacting any one or more of the manganese oxide-containing substances of manganese oxide particles, silver oxide particles, and copper oxide particles with formaldehyde while causing the generation of carbon dioxide And a method for decomposing and removing formaldehyde.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
The manganese oxide used in the present invention is preferably a particulate manganese oxide (manganese oxide particles). Manganese oxide-containing material can be used in the decomposition and removal method of the formaldehyde present invention may be a manganese oxide alone, in addition to manganese oxide, cerium, silver, copper or al least one selected It may be a content of metal particles or metal oxide particles.
[0006]
The manganese oxide particles used in the present invention include manganese dioxide, activated manganese dioxide, manganese monoxide, Mn ₃ O ₄ , Mn ₂ O _3, Mn ₂ O ₇ and other particles, and preferably active manganese dioxide particles. , Manganese dioxide particles or trimanganese tetroxide particles, most preferably active manganese dioxide particles. Here, the activated manganese dioxide particles are porous manganese dioxide particles having a large specific surface area represented by the general formula MnOx (where x is 1.8 to 2.0 in many cases). Obtained. The specific surface area of the manganese oxide particles used is 50 square meters / g or more, preferably 70 square meters / g or more, and more preferably 100 to 2,000 square meters / g. It is 0.1 to 10 µm, more preferably 0.1 to 4.0 µm in average particle size. Here, the specific surface area is a value obtained as a nitrogen adsorption specific surface area (BET).
[0007]
Among the metals or metal oxide particles used in addition to the manganese oxide particles, the cerium oxide includes Ce ₂ O ₃ and CeO ₂ , and preferably CeO ₂ . Silver oxide includes Ag ₂ O, AgO, and Ag ₂ O ₃ , and is preferably Ag ₂ O. Copper oxide includes cuprous oxide and cupric oxide. For copper, it has preferably better copper metal than the oxide.
[0008]
It said cerium, silver, copper or al metal or metal oxide selected in order to increase the formaldehyde decomposition and removal performance, particles in the range of 0.1~10μm is preferably used with an average particle size. When two or more kinds of metal or metal oxide particles need to be mixed, they may be uniformly mixed using a mortar, a ball mill or the like.
[0009]
Examples of the manganese oxide-containing material that can be used in the method for decomposing and removing formaldehyde of the present invention include, in addition to a single type of particle or a mixture of a plurality of particles, heat-permeable materials such as polyethylene particles on a gas-permeable base material such as glass fiber. using thermoplastic resin particles as a binder, wherein the manganese oxide or its cerium, silver, be copper or al sheet obtained by heating and fixing the one or more metal particles or metal oxide particles chosen Good. The filter may be formed by attaching and fixing the above-mentioned particles of manganese oxide or the like to the honeycomb-shaped carrier using an inorganic binder or an organic binder. Further, the porous honeycomb-shaped carrier may be impregnated with a metal salt solution (manganese nitrate aqueous solution or the like) as a precursor of the above-described manganese oxide or the like and sintered to form a filter.
[0010]
In the method for decomposing / removing formaldehyde of the present invention, the temperature at which the formaldehyde-containing air is brought into contact with the manganese oxide-containing substance is not particularly limited, but is preferably the temperature of a living environment, that is, 3 to 3 hours. Performed in a temperature range of 40 ° C.
[0011]
Hereinafter, an experimental example will be described.
Experimental example 1
Various metal oxides (silver oxide, palladium oxide, copper oxide, cobalt oxide, zinc oxide, manganese dioxide, iron oxide, tungsten oxide, titanium oxide, cerium dioxide, trimanganese tetroxide, vanadium pentoxide, and lanthanum oxide particles (all (Manufactured by Wako Pure Chemical Industries, Ltd., manganese dioxide having a specific surface area of 61 square meters / g and an average particle diameter of 5 μm) was tested (screened) for formaldehyde gas removal capacity and carbon dioxide generation. 0.5 g of the oxide particles are spread on the bottom of a glass reaction vessel (1.16 L), and 20 μL of formalin solution is dropped along the inner wall of a glass test tube provided in the reaction vessel, and then the reaction vessel is sealed. And allowed to stand at 25 ° C.
[0012]
The concentration of the generated formaldehyde gas was measured after 2 hours and compared with the blank test value. The HCHO removal rate (%) was calculated by the following equation (1).
([HCHO] bt- [HCHO] t) / [HCHO] bt × 100 (1)
Here, [HCHO] t is a sample value of the formaldehyde concentration at time t, and [HCHO] bt is a blank test value. The amount of carbon dioxide generated (ppm) was calculated by the following equation (2).
[CO ₂ ] t- [CO ₂ ] bt (2)
Here, [CO ₂ ] t is a sample value of the carbon dioxide concentration at time t, and [CO ₂ ] bt is a blank test value. In addition, the measurement of the density | concentration used the detection tube (for 91L formaldehyde and 2LL carbon dioxide) made by Gastech. The results are shown in FIG.
[0013]
The formaldehyde removal rate was as high as 70% or more for silver oxide, manganese dioxide and titanium oxide, followed by cerium dioxide, trimanganese tetroxide, cobalt oxide and palladium oxide. On the other hand, manganese dioxide produced the highest amount of carbon dioxide at about 300 ppm, while silver oxide and lanthanum oxide reduced the carbon dioxide concentration. The mechanism by which carbon dioxide is formed from formaldehyde is not clear, but formaldehyde contacts the basic surface of the metal oxide to form formic acid (Cannizzaro reaction), which is fixed as formate and fixed on manganese dioxide. It is estimated that the salt is further decomposed to carbon dioxide.
[0014]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
Manganese dioxide particles (manufactured by Wako Pure Chemical Industries, Ltd., having a specific surface area of 61 square meters / g and an average particle size of 5 μm) were used alone or in the form of a mixed particle system of manganese dioxide particles and cerium dioxide particles. Tested. The mixing ratio of manganese dioxide and cerium dioxide was 4: 1, 1: 1, and 1: 4 by weight. The results are shown in FIG. Cerium dioxide has a lower formaldehyde removal rate and lower carbon dioxide production than manganese dioxide, but when added at a weight ratio of 4: 1 or 1: 1 there is a tendency to increase the carbon dioxide production compared to manganese dioxide alone. Was done.
[0015]
Example 2
A test was conducted in the same manner as in Example 1 except that manganese dioxide was mixed with silver oxide. The mixing ratio of manganese dioxide and silver oxide was 9: 1 and 9.5: 0.5 by weight. The results are shown in FIG. The mixed system of both improved formaldehyde removal rate compared to manganese dioxide alone and also increased the amount of carbon dioxide generated.
[0016]
Example 3
In addition to manganese dioxide alone, a mixed system of manganese dioxide / silver oxide and a system in which copper oxide and metallic copper were further mixed were prepared, and a test was conducted in the same manner as in Example 1. The mixing ratio of manganese dioxide and copper oxide is 2: 3, the mixing ratio of manganese dioxide and metallic copper is 2: 3, the mixing ratio of manganese dioxide, copper oxide and silver oxide is 3.6: 5.4: 1, manganese dioxide And the mixing ratio of metallic copper and silver oxide was 3.6: 5.4: 1. The results are shown in FIG. When copper oxide or metallic copper was mixed with manganese dioxide, the formaldehyde removal rate was reduced, but when metallic copper was mixed, the amount of carbon dioxide generated increased. Similar results were obtained in a mixed system of manganese dioxide and silver oxide. It is believed that the mixed metallic copper has an effect of promoting the generation of carbon dioxide.
[0017]
Example 4
Comparative tests were performed on manganese dioxide and activated manganese dioxide. The test conditions were the same as in Example 1. The particles used were manganese dioxide (manufactured by Wako Pure Chemical Industries, specific surface area: 61 square meters / g, average particle size: 5 μm) and activated manganese dioxide (manufactured by Nippon Heavy Industries, specific surface area: 163 square meters / g). g, average particle size 1.2 μm). In the test, in order to clarify the difference in performance between the two, the used amount of the catalyst particles was changed from 0.05 to 1 g, and the gas concentration in the container was measured 20 hours after the test was started. FIG. 5 shows the results. As is apparent from FIG. 5, active manganese dioxide has a higher formaldehyde removal rate, and the amount of catalyst required to achieve a removal rate of 50% is about half that of reagent-grade manganese dioxide. there were.
[0018]
Example 5
An aluminum honeycomb (AL-C500, manufactured by Shin Nippon Core) having a size of 300 mm x 300 mm x (thickness) of 25 mm and a cell number of 500 cells / square inch was used as a honeycomb structure serving as a formaldehyde removal filter support in which a catalyst was fixed to the honeycomb structure. Prepared in advance. Water is weighed into a container, and 20 parts by weight of activated manganese dioxide (specific surface area: 100 square meters / g, average particle size: 1.3 μm) is added little by little with stirring, and after sufficient stirring, an aqueous dispersion binder (Polyzo) is stirred. -AP-6740 (manufactured by Showa Kobunshi)) was added little by little and mixed. This was filtered through a filter having a mesh size of 300 μm, and the passing solution was used as a coating solution (solid content concentration was about 25% by weight). Next, an aluminum honeycomb prepared in advance is mounted on a drum of a centrifugal coating machine, and the coating liquid is poured into a spray container. The drum rotation speed is 50 rpm, a discharge rate is 10 L / min, and a coating time is 3 minutes. The coating liquid was applied, and then the number of revolutions was increased to 300 rpm to uniformly spread the coating liquid inside the aluminum honeycomb. After heating this in a dryer at 150 ° C. for 30 minutes, it was cut into 25 mm × 25 mm × (thickness) 25 mm to obtain a formaldehyde removal filter for performance test (referred to as A).
[0019]
Separately, the following three examples of formaldehyde removal filters (support: aluminum honeycomb) were produced. Three kinds of catalysts were used. Manganese dioxide (RB-A, manufactured by Mitsui Kinzoku) having a specific surface area of 63 square meters / g and an average particle size of 3.7 μm, manganese dioxide having a specific surface area of 55 square meters / g and an average particle size of 5.0 μm (Reagent grade, manufactured by Wako Pure Chemical Industries), trimanganese tetroxide (Callite 400, manufactured by Carus) having a specific surface area of 330 square meters / g and an average particle diameter of 6.0 μm. The preparation method of the formaldehyde removal filter is the same as above. .
[0020]
These were also cut into 25 mm x 25 mm x (thickness) 25 mm to obtain a performance test filter. The obtained formaldehyde removal filters are designated B, C, and D, respectively. The four types of formaldehyde removal filters A to D were evaluated for their ability to decompose and remove formaldehyde. Each formaldehyde removal filter was inserted and fixed in the center of an acrylic square pipe having an inner size of 25 mm x 25 mm and a length of 500 mm. A gas hose was connected so as to seal both ends of the square pipe and allow formaldehyde gas to flow. Further, a formaldehyde gas generator was connected to one end with a flow meter interposed therebetween. Formaldehyde gas (formaldehyde concentration: 3 ppm) was introduced into the square pipe at a flow rate of 2 L / min from the formaldehyde gas generator, passed through a formaldehyde removal filter, and discharged from the other end. One hour later, the formaldehyde concentration (measured by a formaldehyde gas detector tube (91 L and 91 LL, manufactured by Gastec)) was measured before and after the formaldehyde removal filter, and the formaldehyde removal rate was determined using the following equation. Removal rate (%) = [(inlet side concentration)-(outlet side concentration)] / (inlet side concentration) × 100 The formaldehyde removal rate of the formaldehyde removal filter is 90% for A, which is the highest, and 75% for D. Was. B was 30% and C was 10%.
[0021]
【The invention's effect】
ADVANTAGE OF THE INVENTION By this invention, handling was easy, the heat source (energy source) was not required, and the method of removing and decomposing | disassembling formaldehyde in air effectively under the temperature conditions of a living environment, and detoxifying it could be provided.
[Brief description of the drawings]
FIG. 1 is a bar graph showing formaldehyde removal rates and carbon dioxide generation amounts of various metal oxide particles (Experimental Example 1).
FIG. 2 is a bar graph showing the relationship between the mixing ratio of manganese dioxide particles and cerium dioxide particles and the formaldehyde removal rate and the amount of carbon dioxide generated (Example 1).
FIG. 3 is a bar graph showing the relationship between the mixing ratio of manganese dioxide particles and silver oxide particles and the formaldehyde removal rate and the amount of carbon dioxide generated (Example 2).
FIG. 4 is a bar graph showing the relationship between the mixing ratio of manganese dioxide particles, silver oxide and copper oxide (or metallic copper), the formaldehyde removal rate and the amount of carbon dioxide generated (Example 3).
FIG. 5 is a graph showing a comparison between the formaldehyde removal rate of active manganese dioxide and the formaldehyde removal rate of manganese dioxide (Example 4).

Claims (3)

Formaldehyde-containing air,
(1) a mixture of manganese oxide particles and cerium oxide particles, wherein the cerium oxide particles contain 20 to 50% by weight of a manganese oxide-containing material;
(2) manganese oxide-containing material of manganese oxide particles and silver oxide particles,
(3) contacting any one or more of the manganese oxide-containing materials of manganese oxide particles, silver oxide particles, and copper oxide particles to formaldehyde while producing carbon dioxide; For decomposing and removing formaldehyde. 2. The method for decomposing and removing formaldehyde according to claim 1, wherein at least one of manganese dioxide particles, activated manganese dioxide particles and trimanganese tetroxide particles is used as the manganese oxide particles. 3. The method for decomposing and removing formaldehyde according to claim 1, wherein particles having a specific surface area of 50 square meters / g or more are used as the manganese oxide particles.

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