JP2005262109A - Method for oxidizing or decomposing organic matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for enabling oxidizing or decomposing organic matter in the shortest time so that an expensive apparatus is made as low as possible. <P>SOLUTION: Organic matter is introduced into heated photocatalyst particles and oxidized or decomposed by oxygen and the photocatalyst particles activated by heating and furthermore oxidized or decomposed by an oxidation catalyst at the succeeding step. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for oxidizing or decomposing organic matter.

  Recently, the treatment of organic substances such as plastics has become a major social problem. This is mainly because plastic does not decompose as it is, it cannot be solved by landfill, and the landfill site is disappearing.

  Such processing of plastics and the like has conventionally been an incineration method. Incineration is burning at high temperature in a furnace to produce carbon dioxide and other oxides.

However, in the combustion method, there is a risk that toxic gas is generated unless complete combustion is performed. Therefore, the fuel is inevitably burned at a high temperature. Therefore, since unnecessary fuel is also incinerated, the surrounding environment is heated and carbon dioxide is unnecessarily generated.
Furthermore, it is difficult to completely suppress the generation of dioxins.

Thus, the inventors have devised a method for oxidizing and decomposing plastics at a relatively low temperature using a photocatalyst and have filed a patent application.
In this method, plastic fragments are mixed with heated photocatalyst powder, which is an excellent method for easily decomposing plastics at low temperatures.
JP 2002-363337 A

However, in this method, an electromagnetic wave irradiation device such as ultraviolet rays is indispensable, and the device (lamp) is vulnerable to heat, and it has been necessary to use expensive quartz glass or put it in a light-transmitting cooling pipe. .
Therefore, a patent application has also been filed for a method in which the photocatalyst is activated only by heat to decompose the organic matter. This method does not require an expensive ultraviolet lamp and is excellent in that respect. However, it is difficult to oxidize completely with heat alone.

  Therefore, a method is provided that can oxidize or decompose organic matter in as short a time as possible and oxidize or decompose the remaining unoxide almost completely.

  In view of the current situation as described above, the present inventor has completed the method for oxidizing or decomposing the organic matter of the present invention as a result of intensive research. The organic substance is oxidized or decomposed by the photocatalyst and oxygen activated by heating, and further oxidized or decomposed by an oxidation catalyst as a subsequent step.

  The first feature of the present inventor is that the photocatalyst is activated only by heat without being irradiated with electromagnetic waves. That is, if activated by heating and an oxidation source is present, the organic matter is oxidized or decomposed. Conventionally, the advantage of a photocatalyst that can be oxidized and decomposed at a low temperature is expressed over a high-temperature oxidation catalyst.

  Here, the organic substances include not only solids such as plastics and liquids such as fats and oils but also toxic substances such as PCBs. The organic matter is not limited to low molecules and polymers. Further, a gas may be used. For example, malodorous gases from factories and poultry farms, or cracked gases from organic matter decomposing devices may be used. In short, any organic material may be used.

In the case of a solid, it is naturally preferable to crush and pulverize from the viewpoint of decomposition efficiency. It is preferable to decompose the solid with mixing and stirring with the photocatalyst particles.
In the case of a liquid, it is preferable to spray from the top of the photocatalyst particles heated and filled, but it may be sprayed into a reactor in which the photocatalyst is suspended.
In the case of gas, it is only necessary to pass between heated photocatalyst particles.

As the photocatalyst, anatase type crystals of titanium oxide are generally well known, but other photocatalysts may be used. In short, it undergoes a photo-oxidation reaction upon receiving electromagnetic waves (such as ultraviolet rays and visible light).
The smaller the particle, the better the efficiency of the photocatalyst. Therefore, usually several nm to several μm are suitable, but the special size is not limited. In addition, since the fine powder soars and goes out of the system along with gas, the following various types are preferable in order to eliminate it as much as possible.
(1) Granulated fine powder with binder (adhesive).
(2) Sintered and granulated fine powder.
(3) A fine powder or granulated material supported on a carrier.
(4) Crushed or crushed granulated material.

  A material obtained by granulating fine powder with a binder (adhesive) can be used with various adhesives, but it is preferable to use a material such as titanium alkoxide. This is because the catalytic effect is exhibited as a whole.

  Sintered and granulated fine powder is difficult to powder because of its high strength. Therefore, handling is easy.

Any carrier may be used for carrying. For example, particles such as silica sand may be used, and fibers may be used. The size is not particularly limited, but is 10 mm or less, preferably several μm to 6 mm, and more preferably about 10 μm to 1 mm.
As a method of fixing to the carrier, adhesion may be made with a fluorine-based resin or a silicon-based resin that is not easily decomposed. Moreover, it is thought that the catalyst efficiency improves as a whole when titanium alkoxide is used as an adhesive. The same applies when crushing.
The size of this adhesive granulation type is also free but is preferably about 10 μm to 10 mm.

Further, both a water-based resin (water-soluble resin or emulsion-type resin) and cement (all those cured by a hydraulic reaction) may have a photocatalyst fixed to a carrier.
In the fixing method, first, an aqueous resin is applied to the carrier, and then the cement and the photocatalyst are fixed. First, the cement or photocatalyst is fixed by the initial adhesive strength of the water-based resin. And if a cement hardens | cures, even if an aqueous resin is decomposed | disassembled by the oxidizing power by a photocatalyst, it will be hold | maintained by the cement.
The amount to be attached is arbitrary and does not depend on the method of attachment, but it is usually about 1% to 10% of the weight of the carrier due to the difference in size with the carrier.

  Photocatalyst particles can be filled in a reactor, in a mesh-like container and installed in the reactor, supported by a filter, or suspended in the reactor. Good.

  The filter here simply means that the passage is a large number of small holes. Therefore, any material such as particles, cloth, non-woven fabric, sponge, porous material, etc. may be used. This filter carries a photocatalyst. As a supporting method, a fluorine-based resin or a silicon-based resin which is not easily decomposed may be used, or may be fixed with an inorganic adhesive. Further, it may be fixed with both the aqueous resin and cement. The shape can be freely selected, for example, a block or plate made of a net filled with photocatalyst-supporting particles, or a frame in which photocatalyst particles are fixed to the cloth or nonwoven fabric described above.

  The heating temperature is determined by the type of organic matter to be decomposed and the shape and size of the photocatalyst. Usually, it is 50-600 degreeC, However, 100-450 degreeC, Especially 150-350 degreeC is suitable. This is due to the balance between decomposition efficiency, heating costs and other factors.

  Any heating method may be used as long as the photocatalyst particle layer can be heated. Electric heaters, gas burners, etc. It is preferable to control the temperature by providing a temperature control device.

  There is no problem as long as oxygen (air) is sufficient to oxidize organic matter in the container filled with the photocatalyst. However, if it seems to be insufficient, it is introduced separately from the air introduction pipe. If oxygen is included, it does not have to be air.

  Oxidation is a reaction in which ammonia becomes nitric oxide, and decomposition here means that a polymer becomes a low molecule. One or both of these occur and the organic matter changes. The changed products are mostly carbon dioxide and water, but naturally nitrogen and sulfur oxides are also generated if the raw material contains nitrogen and sulfur.

  Even the organic matter oxidized or decomposed by the heated photocatalyst is not completely oxidized or decomposed. There is a possibility that unreacted substances and intermediate products may leave the photocatalyst layer as they are. For this reason, in this invention, it is oxidized or decomposed | disassembled by an oxidation catalyst as a post process.

An oxidation catalyst generally causes oxidation and decomposition reactions at a lower temperature and in a shorter time than when no catalyst is used. 200-400 ° C is sufficient. Various types of such oxidation catalysts are conventionally known and commercially available.
For example, there are metal catalysts such as platinum, palladium, cobalt, manganese and various alloy catalysts. In general, these powders are fixed to various types of carriers. Examples of the shape of the carrier include a honeycomb type, a pellet type, and a metal foam type, and any of them can be used in the present invention.

  In particular, a honeycomb-shaped platinum catalyst was suitable. A type that is used in an exhaust or the like for oxidation of automobile exhaust gas is preferable. The size may be determined by the amount of organic matter processed by the apparatus and other conditions.

  This oxidation catalyst has a great effect on the oxidation of unburned substances such as carbon monoxide and hydrocarbons, and is almost immediately oxidized if there is a certain temperature with oxygen. Carbon monoxide is converted to carbon dioxide, hydrogen is converted to water, and hydrocarbon is converted to carbon dioxide and water.

  As described above, the present invention combines the oxidation and decomposition by the photocatalyst with the oxidation and decomposition by the oxidation catalyst. Therefore, the photocatalyst mainly cuts the carbon-carbon bond to reduce the molecule, and the oxidation catalyst mainly binds to oxygen. Seems to be happening.

The oxidation and decomposition by the photocatalyst and the oxidation and decomposition by the oxidation catalyst may be performed in the same reactor. In other words, this is a system in which an oxidation catalyst is provided downstream of the photocatalytic reaction portion. Moreover, you may make it react with another reactor. It is easier to manage the temperature and the amount of oxygen (air, etc.) by using another reactor.
Oxygen (air or the like) may be introduced before the oxidation catalyst reaction.

  The oxidation or decomposition method of the present invention can be carried out either continuously or batchwise. Further, when a tar-like material or carbon adheres to the surface of the used photocatalyst, it may be discarded or regenerated, but is not directly related to the present invention.

Moreover, you may provide another process process between the above-mentioned two essential processes (oxidative decomposition by a photocatalyst, and oxidative decomposition by an oxidation catalyst). For example, a layer filled or fixed with a photocatalyst is provided, another catalyst layer is provided, or a simple filter is provided.
These are for decomposing or catching (adsorbing) at this portion when decomposed solids (tar or the like) are discharged from the oxidative decomposition step by the photocatalyst, or when the photocatalyst itself is discharged. Of course, since there is an oxidation catalyst process downstream, there is no need for complete decomposition or the like. These may be easily exchanged or may be regenerated at a high temperature.

  This treatment step may be carried out in a single container or apparatus or in another reactor. Further, a bypass line may be provided so as not to pass therethrough when unnecessary. The temperature and other conditions may remain in the upstream reactor, but may be changed only here.

The method of the present invention has the following great advantages.
(1) The photocatalyst can efficiently oxidize or decompose, and unoxidized and undecomposed products are oxidized and decomposed at the downstream oxidation catalyst portion. Thus, almost no unoxide remains.
(2) Since both the photocatalyst and the oxidation catalyst are used, the reactions that occur efficiently are combined, which is very efficient. Complete oxidation is difficult with photocatalyst alone, and it is difficult to break carbon-carbon bonds with oxidation catalyst alone.
(3) It can be carried out with a very simple device and can easily decompose plastics and other organic substances.

  Hereinafter, the present invention will be described in more detail based on preferred examples.

  FIG. 1 is a schematic cross-sectional view showing an example of an apparatus 1 for carrying out the organic substance oxidation or decomposition method of the present invention. Photocatalyst particles 3 are packed in the reactor 2. The particle 3 is obtained by granulating fine powder into a size of 0.5 mm. A cooling coil 4 is installed in the photocatalyst layer. In this, air or water passes through the inside, and the catalyst layer is cooled. This is for cooling when the temperature rises excessively due to the oxidation reaction. In order to improve the contact efficiency, a stirring device 5 is provided and rotated.

  A burner 6 is provided below. This is also temperature controllable. The reactor 2 is provided with an organic substance introduction port 7, an air introduction port 8, and a discharge port 9. These may be opened continuously or intermittently.

  An oxidation catalyst layer 10 is provided in the upper part of the reactor 2. In this example, it is a honeycomb-shaped platinum catalyst. In this example, it is a single stage, but it may be a multistage type. Since almost only gas passes, the eyes may be fine.

  First, an organic substance (here, a crushed piece of plastic) is introduced from the organic substance introduction port 7. At the same time, air is introduced. The catalyst and the organic substance are mixed and stirred by the stirring device 5 in the catalyst layer. Since the catalyst is heated and activated (400 ° C. in this example), it reacts with oxygen and the plastic is decomposed into a low molecular gas. Examples of the gas include carbon dioxide, carbon monoxide, hydrocarbons, and the like, which are in contact with the oxidation catalyst layer 10 as they are. Therefore, non-oxides such as carbon monoxide are oxidized. After the discharge port 9, it may be open to the atmosphere or another processing step.

100 kg of granulated particles (size of about 1 to 5 mm) of photocatalyst (titanium oxide) were put into the above apparatus, and 10 kg of crushed polyethylene (size of about 1 to 10 mm) was put therein and heated to 400 ° C. The mixture was decomposed with good stirring and decomposed and gasified and passed through a platinum catalyst layer.
In front of the platinum layer, about 0.1% of carbon monoxide was contained, but it was several ppm downstream of the platinum layer.

It is a schematic sectional drawing which shows an example of the apparatus which enforces this invention method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic substance decomposition apparatus 2 Reactor 3 Photocatalyst particle 4 Cooling coil 5 Stirrer 6 Burner 7 Organic substance inlet 8 Air inlet 9 Outlet 10 Oxidation catalyst layer

Claims (4)

  An organic substance is introduced into heated photocatalyst particles, the organic substance is oxidized or decomposed by the photocatalyst and oxygen activated by heating, and further oxidized or decomposed by an oxidation catalyst as a subsequent step. The method for oxidizing or decomposing organic matter.   The method for oxidizing or decomposing organic substances according to claim 1, wherein the heating temperature is 50C to 600C.   2. The method for oxidizing or decomposing organic matter according to claim 1, wherein the photocatalyst particles are obtained by granulating photocatalyst fine particles with an adhesive. The method for oxidizing or decomposing an organic substance according to claim 1, wherein the oxidation catalyst is a honeycomb-shaped catalyst having platinum supported thereon.

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