JPH0975670A - Treatment of organic pollutant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To purify an org. pollutant present in the atomosphere, residence environment and work environment at the normal temp. in an energy saving manner. SOLUTION: A substance having at least one kind of a property among org. pollutant adsorbing, org. pollutant decomposing and oxidizing and microwave absorbing properties is used or substances having those properties are combined to be used. Two treatment systems equipped with three kinds of propertires are prepared and the adsorptive removal of the org. pollutant, microwave irradiation and heating decompositional oxidation by the systems are alternately repeated to purify the org. pollutant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating organic pollutants existing in the atmosphere, living environment or working environment.

[0002]

2. Description of the Related Art It has been a long time since the need for environmental pollution control measures has been exaggerated in response to the development of industry, but in recent years there has been an increasing demand for a more comfortable environment, and it has become difficult to respond to pollution situations. There is a growing need for excellent air purification in the atmosphere and in the living and working environment, or local air purification in these spaces.

Main sources of environmental pollutants include factory exhaust gas as a fixed source, exhaust gas from various combustion devices, and exhaust gas from an automobile as a mobile source, and the like. Although it has little impact on environmental pollution, exhaust gases from all kinds of daily activities are involved as pollution sources, and these gases include nitrogen oxides, sulfur oxides, carbon dioxide, or unburned hydrocarbons and hydrocarbons. In addition, organic pollutants such as compounds containing heteroatoms such as nitrogen, oxygen, sulfur, halogen, etc. are contained, and purification measures are taken for each gas according to the situation.

Since hydrocarbons and organic pollutants containing heteroatoms in hydrocarbons are combustible carbon and hydrogen-based compounds, they are basically purified by a combustion reaction, specifically, A method of burning and removing by exposing the atmosphere containing an organic pollutant to a high temperature, a method of catalytically burning and removing at a low temperature in the presence of a catalyst, and the like are performed.

By applying the catalyst technology, environmental purification can be performed in an energy-saving manner, but in order to fully exert the catalytic performance, it must be brought into contact with a pollutant gas at a temperature at which the catalyst acts, for example, at room temperature. Alternatively, in order to remove pollutants existing at a temperature close to it (3), the pollutant-containing gas is preheated or the catalyst itself is heated by some means and brought into contact with the pollutants while maintaining that state. It has the drawback of having to rely on the method.

As a method in such a case, for example, in automobile exhaust gas treatment immediately after start-up, until the temperature of the treatment system or the exhaust gas temperature rises to a sufficient degree to cause a catalytic reaction, the removal target A method has been proposed in which a gas is adsorbed and removed in advance by contacting it with an adsorbent, and then, after the temperature of the catalyst rises to a working temperature, a pollutant gas is desorbed and removed catalytically. In Japanese Patent No. 9411623, removal of hydrocarbons by adsorbing them onto zeolite until the exhaust gas treatment catalyst reaches the working temperature is also disclosed.
In 198136, a method of treating exhaust gas by combining a zeolite for adsorbing hydrocarbons and a three-way catalyst is disclosed.

In catalytically removing pollutant gas, it is preferable to purify the pollutant before it diffuses into the atmosphere. However, in many cases, the pollutant gas diffuses into the atmosphere at room temperature. In some situations, it is necessary to heat the catalyst or pollutant gas, and there is also proposed a method of making the catalyst a self-heating type in order to quickly heat the catalyst to the working temperature. In this case, the catalyst component is supported on the electric resistor. The method of heating the catalyst by applying electricity is usually used.

On the other hand, as a recently disclosed technique, a heating method using microwave irradiation has been used, which basically achieves the heating purpose by combining a microwave absorbent and a catalyst. For example, in JP-A-5-68894 and JP-A-6-248936, a substance having a microwave absorptivity is placed on the upstream side of the catalyst layer and heated by microwave irradiation. A method of heating a pollutant gas by bringing the pollutant gas into contact with a substance is disclosed in JP-A-4-83514 and JP-A-5-54154.
Japanese Patent Publication No. 168950 discloses a method of heating a catalyst by microwave irradiation by mixing a microwave absorbing substance with a catalyst (4), and mainly discharging from an internal combustion engine such as an automobile. Applied to the treatment of gas.

[0009]

In the method of purifying pollutants, the treatment technique using a combination of an adsorbent and a catalyst is effective as an automobile exhaust gas treatment method at the time of starting. In this case, the catalyst and the exhaust gas are discharged immediately after the engine is started. It is common practice to adsorb and remove pollutants only during a low temperature period when the gas is in a low temperature state and the catalyst does not work sufficiently, and after the catalyst reaches a heating state, purify the exhaust gas by a catalytic reaction. Cannot be applied when organic pollutants are present at room temperature due to diffusion in the air, living environment, working environment, etc.

In the purification by combustion reaction of hydrocarbons as organic pollutants and compounds having heteroatoms such as nitrogen, oxygen, sulfur and halogen in hydrocarbons, pollutants are present in the atmosphere or in the living environment, working environment, etc. When it is present in a low concentration, it is often present at room temperature, and when it is removed by low temperature catalytic combustion in the presence of a catalyst, the amount of heat energy consumed is significantly higher than the amount of pollutants purified. Since the amount is large, it cannot be an effective method for purifying organic pollutants, and a purification method that is more energy-saving and that can be used easily is desired.

[0011]

[Means for Solving the Problems] When a low-concentration pollutant is present in the air at room temperature, the method of removing the pollutant by combining an adsorbent and a catalyst is excellent as a treatment technology suitable for the pollution situation. Since the adsorbent serves as a means for concentrating low-concentration pollutants, the volume of the pollutant-containing gas can be significantly reduced in the purification of the adsorbent. The energy of can be greatly reduced.

(5) The inventors of the present invention are investigating a technique for purifying organic pollutants existing at room temperature with a combination of an adsorbent and a catalyst, and as a substance having a high surface area and an oxidizing activity, various complex metal oxides are used. We have selected various materials and studied adsorption and removal of organic pollutants existing in the atmosphere at room temperature, but we have found that iron oxide / manganese oxide as a porous iron-based composite oxide or copper-based composite oxide It was confirmed that the composite metal oxide containing copper oxide / manganese oxide, or nickel oxide, nickel oxide has the ability to occlude a large amount of organic pollutants at room temperature.

Further, the composite metal oxide in the state of occluding the organic pollutant is heated by irradiating it with a microwave instead of heating by an ordinary electric heater, and the temperature of the treatment substance system is controlled by a thermocouple. -Type or optical fiber-type thermometer, and the measurement result is fed to the controller.
By controlling the electric power for microwave generation, the microwave pulse interval, and the pulse width by controlling the temperature, the processing system temperature is kept constant to prevent unnecessary heating, and When air was circulated at a temperature sufficiently lower than the heat-resistant temperature, the desorption and decomposition oxidation reaction of the occluded organic pollutant easily proceeded, and the organic pollutant was heated under heating by an ordinary electric heater. It was confirmed that the purification reaction occurred at a considerably low temperature as compared with the decomposition and oxidation under the air flow.

At least one of the dielectric constant and the magnetic permeability of the microwave has an imaginary part, and the microwave is absorbed by a substance that absorbs microwaves and is converted into heat energy. It has the advantage of being able to heat a substance in a short time because of its energy density, but it is unclear why the irradiation causes decomposition and oxidation of organic pollutants at a lower temperature than heating by electric heater. , The elucidation of its action must be left to future research, but when a metal oxide is irradiated with microwaves, the oxide tends to change to a reduced state, which means that the organic pollution by microwave irradiation is caused. Decomposition and oxidation of substances may be one of the factors that can easily occur compared to electric heater heating. (6)

Examples of adsorbents that can be used in the present invention include iron oxide / manganese oxide as a porous iron-based mixed metal oxide, and copper oxide as a porous copper-based mixed metal oxide.
Manganese oxide, nickel oxide, various porous composite metal oxides containing nickel oxide, and porous silicates, porous aluminates, porous carbon materials can be mentioned.
Among these, porous silicates and porous aluminates are compounds having silicon oxide and / or aluminum oxide as a main component and having a high surface area and a high pore volume, and the compounds are silica, alumina and silica. -Alumina, zeolite, layered silicate, hydrotalcite, MCM-41, aluminophosphate type molecular sieve, etc. can be mentioned, and activated carbon can be mentioned as a porous carbon material.

As a catalyst for decomposing and oxidizing organic pollutants, iron oxide / manganese oxide as a porous iron-based mixed metal oxide, copper oxide / manganese oxide, nickel oxide, and oxidized as a porous copper-based mixed metal oxide are used. Various porous composite metal oxides containing nickel can be mentioned, and a catalyst in which at least one metal selected from platinum, palladium and rhodium is supported on a heat resistant carrier can also be used.

In order to desorb the adsorbed organic pollutants from the adsorbent and to oxidatively decompose them with a catalyst, these treatment systems must be heated. In the present invention, heating is performed by microwave irradiation. In order to achieve the heating, irradiation is performed in the presence of a microwave absorbing substance, and as the absorbing substance, iron oxide / manganese oxide as a porous iron-based mixed metal oxide, Copper oxide / manganese oxide as porous copper-based mixed metal oxide,
Nickel oxide, various porous composite metal oxides containing nickel oxide can be mentioned, and other substances include at least one of dielectric constant or magnetic permeability having an imaginary part, and a microwave absorbing metal oxide or composite metal. Examples thereof include oxides and metal carbides.

The organic pollutant treatment system according to the present invention is provided with three types of properties, namely, organic pollutant adsorption, organic pollutant content (7) deoxidizing property, and microwave absorbing property. In the case of, for example, a porous iron-based mixed metal oxide, this substance has three kinds of properties as the constitutional requirements of the present invention, so it can be used alone, but the substance to be used is In the case where only one or two of these three types of properties are possessed, the treatment system is provided with the three types of properties by using in combination with a substance having the lacking properties, and the purpose is Can be achieved.

The organic pollutants which can be purified by this treatment system are hydrocarbons which are discharged unburned in the combustion process, and one kind of hydrocarbons, of which hydrogen and carbon are constituent elements. In addition, it is a compound group containing a hetero atom such as nitrogen, oxygen, sulfur, and halogen, and the compound is classified from the structural viewpoint to an aliphatic system, an alicyclic system, and an aromatic system,
Compounds belonging to either structure can be purified by the present treatment system.

Since the microwave used as an energy supply source for heating has a high energy density, the treatment system can be heated in a short time. However, depending on the case, the treatment system may need more than necessary. Microwave irradiation must be used in conjunction with the controller system because it may be heated and impair the performance of the adsorbent and decomposition and oxidation catalyst. Optical fiber
Energy supplied to the processing system by controlling the electric power for microwave generation, the microwave pulse width, and the pulse interval by measuring with a thermometer and feeding back the result to the controller. Control quantity
And the material is operated at any desired temperature.

In actual use, as an organic pollutant treatment system, a treatment system constituted so as to have three kinds of properties: organic pollutant adsorption, organic pollutant decomposition and oxidation, and microwave absorption. Preparation of two series, adsorption of organic pollutants at room temperature (A operation), desorption and decomposition oxidation of adsorbed organic pollutants by microwave irradiation and heating while circulating air (B operation) The organic pollutant is treated by repeating the operation of (8) which is a combination of 1). The operation method is as follows:
The other system performs the B operation, and the A operation and the B operation are systematized so as to be alternately performed without overlapping the respective systems, thereby treating the target organic pollutant.

[0022]

INDUSTRIAL APPLICABILITY The present invention uses an organic pollutant treatment system having three kinds of properties: organic pollutant adsorbability, organic pollutant decomposition and oxidation, and microwave absorbability. -It is a method of purifying organic pollutants by using desorption and decomposition oxidation under irradiation as one cycle, and removes organic pollutants by adsorption at room temperature.
Since it is desorbed and decomposed and oxidized after being concentrated, it is possible to significantly reduce energy consumption, and it is possible to purify a large amount of pollutant gas with a small device, in the atmosphere, living environment, working environment, etc. It is effective in removing locally existing organic pollutants.

[0023]

EXAMPLES Next, the contents of the present invention will be specifically described by way of examples, and the performance evaluation described therein was carried out as follows. (Performance Evaluation Apparatus) The organic pollutant treatment substance-based pollutant removal performance measurement apparatus used in this example is a fixed bed atmospheric pressure type reaction apparatus, and its conceptual diagram is as shown in FIG. Then, the treatment substance system filled in the quartz reaction tube is installed in the microwave waveguide or cavity, and the treatment substance system is irradiated by the microwave generated from the magnetron oscillator. Directly heating and measuring its temperature with a thermocouple type or optical fiber type thermometer, and feeding back the measurement result to the controller, the power supplied to the magnetron oscillator or the generated microwave. It is a device that can control the pulse interval and pulse width of the chamber and control the temperature of the treated substance system. Te, organic pollutant decomposition treatment substances system, oxidation performance is evaluated. (9)

(Performance Evaluation Method) The organic pollutant-containing air is circulated from the reaction tube inlet at room temperature to the organic pollutant treatment substance system in the quartz reaction tube installed in the microwave waveguide or cavity. Adsorbs and removes organic pollutants in the air, stops the flow of pollutant-containing air when the organic pollutants are detected in the outlet gas, and ends the adsorption and removal of organic pollutants. It is heated by microwave irradiation under flow, and the treatment substance system is maintained at a constant temperature and stored by controlling the power supplied to the magnetron oscillator and the generated microwave pulse interval and pulse width. Desorbs, decomposes and oxidizes organic pollutants,
By measuring the change over time in the concentration of pollutants at the outlet of the reaction tube, the decomposition and oxidation performance of the organic pollutants of the treated substance system is measured. The measurement conditions and performance display method are as follows.

Performance measurement conditions (adsorption of organic pollutants) Reaction tube Quartz tube (inner diameter 10 mm) Catalyst material particle size 8 to 14 mesh Catalyst material usage 14 cc Adsorbent and / or microwave absorbent usage 14 cc SV 5000 ( (1 / Hr.) (Relative to catalyst substance) Reaction gas composition Organic pollutant 1000ppm Air (3% water content) Balance temperature Normal temperature Adsorption performance indication time (min) until organic pollutant is detected in outlet gas

Performance measurement conditions (decomposition and oxidation of adsorbed organic pollutants) Method After adsorption of organic pollutants, air (3% water content (10)) is circulated and heated at microwaves to maintain a constant temperature. Gas air temperature 150 ° C SV 5000 (1 / Hr.) Decomposition / oxidation performance display method Adsorbed organic pollutants Degradation / oxidation performance After starting the measurement, the concentration of organic pollutants (ppm) detected at the outlet of the reaction tube is displayed as a function of time.

Example 1 8 to 14 mesh granules 14 cc obtained by crushing an iron oxide / manganese oxide composite metal oxide molded product was filled in a quartz reaction tube and then placed in a microwave waveguide. Then, from the reaction tube inlet side, n-pentane 1000 p
Air containing pm is normal temperature, SV5000 (1 / H
r. ) Was passed through the catalyst layer to adsorb and remove n-pentane, and the flow of n-pentane-containing air was terminated when a leak of n-pentane was observed in the outlet gas.

After the adsorption of n-pentane, the microwave generated from the magnetron oscillator while circulating air.
The decomposition and oxidation performance of n-pentane by the iron oxide / manganese oxide composite metal oxide was measured by irradiating and heating the iron oxide / manganese oxide catalyst in the n-pentane occluded state and maintaining it at a constant temperature. , The results obtained are
1

Example-2 A copper oxide / manganese oxide was prepared in the same manner as in Example-1 except that copper oxide / manganese oxide was used instead of the iron oxide / manganese oxide mixed metal oxide. N-Petane adsorption / removal at room temperature and n-pentane decomposition and oxidation performance under microwave irradiation and heating were measured while circulating air. The obtained results are shown in Table (11) -1. Met.

Example 3 An inorganic binder was added to an equal mixture of zeolite and silicon carbide powder, the molded body was crushed, and then the crushed product was sieved to obtain a 8-14 mesh sized product. (Preparation of granules A) in 14 cc was prepared, and the platinum-alumina compact was further treated in the same manner to prepare 14 cc of 8 to 14 mesh sized particles (designated as granules B).

Granule A and granule B were placed in a quartz reaction tube.
Is placed so that it is located on the upstream side of the gas flow, and then it is installed in the microwave waveguide, and then air containing 1000 ppm of n-pentane is introduced from the reaction tube inlet side at room temperature and S
A flow rate of V5000 (1 / Hr.) Was passed through the treatment system to adsorb and remove n-pentane. At the time when a leak of n-pentane was observed in the outlet gas, the flow of n-pentane-containing air was changed. finished.

After the end of the n-pentane adsorption, the microwave generated from the magnetron oscillator while circulating the air.
Directly irradiates and heats a processing system consisting of zeolite / silicon carbide and platinum / alumina in an n-pentane occlusion state,
The decomposition and oxidation performance of n-pentane was measured by maintaining it at a constant temperature, and the obtained results are shown in Table 1.

Comparative Example-1 In Example-1, as a means for heating the iron oxide / manganese oxide catalyst under air flow, a normal electric heater was used instead of microwave irradiation. In the same manner as in Example 1, removal of n-pentane by adsorption at room temperature and n by heating with an electric heater while circulating air.
-Pentane decomposition and oxidation performance was measured, and the obtained results are as shown in Table-1.

(12) Example-4 After adding an inorganic binder to an equal mixture of zeolite and silicon carbide powder, the molded body is crushed, and then the crushed product is sieved to obtain 8 to 14 mesh. By preparing 14 cc of a sized product (designated as granule A), and further treating a palladium / alumina compact in the same manner,
14 cc of a 14-mesh sized product (referred to as granule B) was prepared.

Granules A and B were placed in a quartz reaction tube
Is placed so that it is located on the upstream side of the gas flow, then it is installed in the microwave waveguide, and then air containing 1000 ppm of acetaldehyde is supplied from the inlet side of the reaction tube at room temperature and SV5000 (1 / Hr.). The acetaldehyde was adsorbed and removed at a certain amount in the treatment system, and the circulation of the acetaldehyde-containing air was terminated at the time when a leak of acetaldehyde was found in the outlet gas.

After the adsorption of acetaldehyde, while circulating the air, the microwave generated from the magnetron oscillating unit was directly irradiated to the acetaldehyde-occluded zeolite / silicon carbide and palladium / alumina treatment system, and heated. The decomposition and oxidation performance of n-pentane was measured by maintaining it at a constant temperature, and the obtained results are shown in Table 1.

Example-5 In the same manner as in Example-4, except that diethylamine, methyl mercaptan, or chloroform was used instead of acetaldehyde as the organic pollutant in Example-4, zeolite / silicon carbide was used. And adsorption removal of diethylamine, methyl mercaptan, or chloroform by a treatment system consisting of palladium and alumina,
Also, the decomposition and oxidation performance of these pollutants under microwave irradiation and heating was measured while circulating air, and the obtained results are shown in Table 1.

(13) Comparative Example-2 In the diethylamine adsorption-removal and decomposition / oxidation performance tests in Example-5, except that the heating by microwave irradiation was replaced by the usual electric heater heating. Except for diethylamine adsorption and decomposition and oxidation performance by a treatment system comprising zeolite / silicon carbide and palladium / alumina were measured in exactly the same manner as in Example-5. The obtained results are shown in Table-1.

Comparative Example-3 A treatment comprising zeolite / silicon carbide was carried out in exactly the same manner as in Example-5 except that the palladium / alumina catalyst was not used in the diethylamine adsorption removal / decomposition / oxidation performance test in Example-5. The adsorption and removal of diethylamine by the system and the decomposition and oxidation performance were measured, and the obtained results are shown in Table 1. (14)

[0040]

[Table 1] Table-1 Results of measuring organic pollutant removal performance (Explanation of symbols) A: Microwave irradiation heating B: Electric heater heating Performance 1; Adsorption performance of organic pollutant treatment system, time (minutes) until the start of organic pollutant performance Performance 2; Organic Shows the decomposition performance of the stored organic pollutants in the pollutant treatment system, and shows the concentration of organic pollutants in the reaction tube outlet gas over time (ppm) (15)

[0041]

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a performance measuring device under the irradiation of a microwave according to an embodiment of the present invention while controlling the temperature of a catalyst substance.

[Explanation of symbols]

1 Controller 6 Reactant Gas Outlet 2 Magnetron Oscillator 7 Temperature Detection Means 3 Catalyst Material 8 Thermocouple or Optical Fiber Thermometer 4 Waveguide or Cavity 5 Reactant Gas Inlet ┌───┐│ │┌─── ───────────
─────┤ 7 ││
5 └─┬─┘ 6│ ┌──
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│ │ │ │ 8 │ ┌──
┴──┐ │ │ │ │
│ │ ├────┤ ├┼
────┼─────┼─┐│ │ │
│ │ │ │ │ │
1 │ │ │ │ ┌─┬─┴──
┬─┐│ │ │ │ │ 2
│ └ ┤ │ 3 │ ├ ┘ │ 4 │ │
│ │ └─┴────┴─┘ │
└─────┘ │ ├─────
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│ └───────┘Figure-1

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[Procedure amendment]

[Submission date] December 27, 1995

[Procedure 3]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B01J 37/34 B01J 23/84 311A

Claims (4)

(1) [Claims] 1. A substance having at least one of the properties of adsorbing organic pollutants, degrading organic pollutants, and absorbing microwaves, or a combination of these substances, and having these three properties. A method for treating an organic pollutant in which the organic pollutant present in the atmosphere is occluded by contacting the organic pollutant present in the atmosphere at room temperature, and then the treatment system is heated by microwave irradiation under air circulation. 2. An organic pollutant-adsorptive substance is porous, and the substance is a complex metal oxide containing iron oxide / manganese oxide, a complex metal oxide containing copper oxide / manganese oxide, nickel oxide, and a complex metal containing nickel oxide. At least one of the oxides
Or at least one of porous silicates, porous aluminates and porous carbon agents, and the porous silicates and porous aluminums are silicon oxides and / or Compounds mainly composed of aluminum oxide, which are silica, alumina, silica-alumina, zeolite, layered silicate, hydrotalcite,
MCM-41, aluminophosphate type molecular
The method for treating an organic pollutant according to claim 1, which is at least one kind of sheave. 3. An organic pollutant decomposable substance is porous, and the substance is a composite metal oxide containing iron oxide / manganese oxide, a copper oxide manganese oxide composite metal oxide, nickel oxide, and nickel oxide. At least one of the
The method for treating organic pollutants according to claim 1, which is a catalyst in which at least one of platinum, palladium, and rhodium is supported on a heat-resistant carrier. 4. The microwave absorbing material is iron oxide.
At least one of a complex metal oxide of manganese oxide, a complex metal oxide of copper oxide / manganese oxide, nickel oxide, and a complex metal oxide containing nickel oxide, or at least one of a dielectric constant and a magnetic permeability has an imaginary part. The method for treating an organic pollutant according to claim 1, wherein the method is at least one of a metal oxide having a microwave absorption property, a composite metal oxide, and a metal carbide. (2)