JP2631067B2 - How to remove trace acetaldehyde from air - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing a trace amount of acetaldehyde contained in air.

[0002]

2. Description of the Related Art Many kinds of trace components are contained in the air, and their kinds and amounts vary greatly depending on the environment. It is also desirable to thoroughly remove these. For this reason, in recent years, for those generated in enclosed spaces such as office buildings and houses, in combination with ventilation, the harmful gas removal function attached to air conditioning equipment such as air purifiers and air conditioners has been improved, and cleanliness has been improved. Efforts are being made to secure a living environment.

A typical harmful gas generated in a normal living environment is cigarette smoke. It is considered that it should be removed by the trace components contained in it,
Ammonia, acetic acid and acetaldehyde, all of which cause unpleasant pungent odors and are also harmful to health. Of these, removal means using activated carbon or zeolite for ammonia and acetic acid have been almost established, but for acetaldehyde, a truly effective and easy-to-implement removal method has not yet been found. Acetaldehyde has been found not only to be emitted from tobacco but also found in the air of kitchens and other kitchens.

[0004] Representative methods for removing acetaldehyde in the air, which have conventionally been proposed, include a method using an adsorbent such as activated carbon, silica gel and zeolite, and a method of burning at a high temperature using a noble metal such as platinum or palladium as a catalyst. And the like. However, the method using an adsorbent is
Since there is no adsorbent with excellent ability to adsorb acetaldehyde, it is often necessary to replace or regenerate the adsorbent,
Moreover, there is a problem of how to dispose of the harmful gas desorbed in the regeneration cycle. On the other hand, the catalytic combustion method is effective for air containing high concentrations of acetaldehyde of several hundred ppm or more, but is not suitable for treating air containing trace amounts of acetaldehyde of about 1 ppm, such as indoor air filled with cigarette smoke. Not very effective, implemented only in industrial fields. In addition, there is a problem that the processing cost is increased because an expensive noble metal catalyst is required.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a means for effectively and inexpensively removing a trace amount of acetaldehyde contained in air.

[0006]

The method for removing acetaldehyde from air according to the present invention comprises contacting acetaldehyde-containing air to be treated with manganese dioxide, adsorbing acetaldehyde in the air to manganese dioxide, and adsorbing acetaldehyde. The method is characterized in that manganese dioxide is heated to catalytically oxidize the adsorbed acetaldehyde.

According to the present invention, the manganese dioxide having a large specific surface area adsorbs acetaldehyde in the air well, and when the manganese dioxide having adsorbed acetaldehyde is heated, the adsorbed acetaldehyde is not desorbed as it is but air. It is based on the present inventors' first finding that they are oxidatively decomposed by oxygen therein. The reaction in which acetaldehyde adsorbed on manganese dioxide is oxidatively decomposed as described above is as follows.
Since the reaction proceeds rapidly at a temperature not so high as about 0 ° C., it is supposed that the reaction involves manganese dioxide as a catalyst.

The catalytic activity of manganese dioxide is better for manganese dioxide having a larger specific surface area. Therefore, in the present invention , manganese dioxide has a specific surface area of 20 m ² / g.
Use the above. Particularly preferred manganese dioxide is
The specific surface area is 50 m ² / g or more (however, the specific surface area is a value measured by the BET method). An example of manganese dioxide having a large specific surface area, adsorbing acetaldehyde well, and having excellent catalytic activity is a commercially available ozonolysis catalyst. Further, a manganese dioxide catalyst described in JP-B-55-8456 can be used in the present invention.

[0009] The process of bringing the air to be treated into contact with manganese dioxide can be carried out by any method following a normal gas phase catalytic reaction or gas adsorption treatment. The simplest method is to fill granular manganese dioxide or manganese dioxide fixed on the surface of a granular carrier into a suitable tube or vessel equipped with a heating device, and flow the air to be treated through the manganese dioxide packed bed. It is. A method of using manganese dioxide supported on a catalyst carrier having a honeycomb structure,
Processing with low pressure loss is possible and preferable.

[0010] The treatment of acetaldehyde-containing air according to the present invention is carried out by repeating an acetaldehyde adsorption cycle performed at normal temperature and a regeneration cycle in which manganese dioxide having adsorbed acetaldehyde is heated to oxidatively decompose the adsorbed acetaldehyde. Do. In the adsorption cycle, as the amount of acetaldehyde adsorbed on the surface of manganese dioxide increases, the concentration of acetaldehyde at the outlet increases, so the supply of air to be treated is stopped at an appropriate stage, the manganese dioxide is heated, and the process proceeds to the regeneration cycle. .

In the regeneration cycle in which manganese dioxide is heated, the temperature of manganese dioxide is set to about 100 to 30.
It is desirable to keep it at 0 ° C. If the temperature is lower than 100 ° C., there is a problem that the acetaldehyde decomposability is poor and the regeneration is not sufficiently performed. On the other hand, heating to a high temperature exceeding 300 ° C. does not shorten the regeneration time much, but only increases the regeneration cost.

In the regeneration cycle, acetaldehyde reacts with oxygen in the air by the catalysis of manganese dioxide to change into carbon dioxide gas and water vapor, leaving the surface of manganese dioxide. Part of the liberated cracked gas comes out of the manganese dioxide packed bed during the regeneration cycle, but the rest is pushed out by the air to be treated when entering the next adsorption cycle. Air containing carbon dioxide gas and water vapor generated by the decomposition of acetaldehyde can be normally released directly into the environment. The method for removing acetaldehyde according to the present invention can be easily carried out in a house, an office building or the like on a large or small scale by attaching a manganese dioxide contact device to an air purifier or an air conditioner.

[0013]

EXAMPLES Using a manganese dioxide catalyst for ozone decomposition (commercially available product; specific surface area 230 m ² / g) as manganese dioxide, an acetaldehyde removal test was conducted under the following conditions. Apparatus: Pipe-type flow measuring instrument Air to be treated: Room temperature air containing 5 ppm of acetaldehyde Adsorption cycle: Air to be treated flows at a space velocity of 10,000 / hr for 60 minutes. Regeneration cycle: supply of air to be treated is stopped, and manganese dioxide is heated to 150 ° C. for 10 minutes.

Under the above conditions, the adsorption cycle and the regeneration cycle were alternately repeated, and the treatment was continued for a total of 20 cycles (23 hours). In the adsorption cycle, the acetaldehyde concentration was measured at the outlet of the device, and the acetaldehyde removal rate (%) was calculated by the following equation. Acetaldehyde removal rate (%) = (inlet concentration-outlet concentration) x 100 / inlet concentration

In the first adsorption cycle, the acetaldehyde removal rate was 90% after 30 minutes from the start and 50% after 60 minutes. When manganese dioxide was heated at 150 ° C. for 10 minutes in the regeneration cycle and regenerated, the same performance as the above initial performance was exhibited in the next adsorption cycle. The recovery of the initial performance by the regeneration was not changed even after the adsorption / regeneration was repeated for 20 cycles.

[0016]

According to the present invention, acetaldehyde in the air can be reliably removed using a manganese dioxide catalyst which is much cheaper than a noble metal catalyst. The method of the present invention utilizes the acetaldehyde adsorption capacity of manganese dioxide to perform an adsorption treatment at ordinary temperature, and heats manganese dioxide only during the regeneration cycle to oxidatively decompose acetaldehyde. Compared to a method of heating and using as a catalyst to sequentially decompose acetaldehyde in air, not only the catalytic activity is prolonged, but also the thermal economy is advantageous, and the temperature rise of the treated air is small. Compared with the method using only an adsorbent, the method of the present invention does not desorb acetaldehyde in the regeneration cycle, but only releases detoxified decomposed gas. The feature is that no countermeasures are required.

Claims (1)

(57) [Claims] 1. A ratio table of air containing acetaldehyde.
Acetaldehyde in the air is adsorbed on the manganese dioxide by contacting the manganese dioxide with an area of 20 m ² / g or more, and the manganese dioxide on which the acetaldehyde is adsorbed is heated to catalytically oxidize the adsorbed acetaldehyde. Of removing trace amounts of acetaldehyde.