JP2007175612A - Decomposition and removal apparatus and decomposition and removal method using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a decomposition and removal apparatus and a decomposition and removal method using the same capable of attaining a higher decomposition rate of a VOC (volatile organic compound) in the presence of steam as well as in a dry gas condition and further capable of reducing its operating cost compared with an apparatus and a method wherein a noble metal supported catalyst is used. <P>SOLUTION: The decomposition and removal apparatus disposed in a flow path of exhaust gas for decomposing and removing a volatile organic compound (VOC) contained in the exhaust gas is characterized by comprising a substrate body (a substrate 27 for example), a heating means (a heater 21A for example) for heating the substrate body directly or indirectly, and a catalyst layer 25A comprising CeO<SB>2</SB>(ceric oxide) disposed on the surface of the substrate body. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a decomposition / removal apparatus that decomposes and removes volatile organic compounds (VOC) contained in exhaust gas using ceria (CeO ₂ ) as a catalyst, and a decomposition / removal method using the decomposition / removal apparatus. Decomposition and removal apparatus for decomposing and removing volatile organic compounds such as aliphatic hydrocarbons such as hexane, aromatic hydrocarbons such as benzene and toluene, and polycyclic aromatic hydrocarbons such as naphthalene contained in exhaust gas, and the apparatus for decomposing and removing the same The present invention relates to a method for disassembling and removing.

Volatile organic compounds (VOC) are aliphatic hydrocarbons such as hexane, aromatic hydrocarbons such as benzene, and polycyclic aromatic hydrocarbons (PAH) such as naphthalene. : Polycyclic Aromatic Hydrocarbons). Aromatic hydrocarbons, particularly benzene and toluene, which are typical components of VOCs, are used in a wide range of applications such as organic solvents and paints, many of which have the potential to cause air pollution. Among them, benzene is known as a carcinogen, and environmental standards are set as shown in Table 1. VOC components are not only carcinogenic and harmful in their own right, but when released into the atmosphere, they synthesize photochemical oxidants such as ozone, and lead to photochemical air pollution along with nitrogen oxides (NO _X ). Causative substance. These secondary photochemical oxidants and suspended particulate matter (SPM) have an environmental standard because they affect the human body (see Table 1). In short, the VOCs mentioned here are harmful pollutants that are likely to affect the environment and the human body, like nitrogen oxides (NO _X ) and sulfur oxides (SO _X ) that are already regulated as air pollutants. One. For this reason, in recent years, VOC emissions into the atmosphere have been regarded as a problem, and not only various combustion exhaust gas such as diesel engine exhaust gas, but also the amount of VOC generated in fixed sources such as various factories and waste treatment in the future. Processing techniques for suppression may be required.

VOC processing technology has been developed with the strengthening of laws and regulations, mainly in Europe and the United States, and there has been a history of the introduction of various devices. On the other hand, in Japan, odor countermeasures are the main, and it has been introduced as an exhaust gas deodorizer, and as a result, VOC has been treated. Such VOC exhaust gas treatment technologies are broadly divided into combustion oxidation methods (direct combustion, catalytic combustion), adsorption methods, and activated sludge methods (biological treatment methods). Which method is used depends on the exhaust gas treatment amount, VOC concentration, etc. Is done. Recently, new treatment methods such as plasma decomposition have been developed. Among various treatment technologies, there are various problems. However, decomposition by photocatalytic action such as titanium oxide (TiO ₂ ) and catalytic combustion (catalytic oxidation) by a noble metal-supported catalyst, etc., finally result in carbon dioxide (CO ₂ ) and water. Since VOC is decomposed to (H ₂ O), it is mentioned as an effective processing means.

Here, the processing technique of VOC by the latter noble metal-supported catalyst, 1) the reaction temperature is low, can be saved fuel costs, 2) thermal NO _X is hardly generated, 3) system can simple downsizing (The installation space is small). Specific examples of such a VOC treatment technique using a noble metal-supported catalyst include a metal oxide support on which a noble metal such as platinum (Pt) or palladium (Pd) is supported as an active component, and a combination of several types of metal oxides. There are those using complex oxides (see, for example, Patent Document 1 and Patent Document 2).

  And as a decomposition removal apparatus using these catalysts, what is shown in FIG. 28 is proposed (refer patent document 3). The decomposition / removal device 500 is configured to send dust to the catalyst tower 502 after removing the exhaust gas containing the organic compound discharged from the furnace with the bag filter 501. At that time, the decomposition / removal apparatus 500 raises the temperature of the exhaust gas by the reheater 503 provided at the bottom of the catalyst tower 502 and then sends it to the catalyst layer 504 located downstream of the reheater 503 to be contained in the exhaust gas. Decomposition and removal of organic compounds. The decomposition / removal apparatus 500 releases the exhaust gas from which the organic compound has been decomposed and removed using the induction fan 505 from the chimney 506 to the atmosphere. That is, the decomposition / removal apparatus 500 increases the temperature of the exhaust gas immediately before sending the exhaust gas to the catalyst layer 504, thereby promoting the reaction between the catalyst layer 504 and the organic compound to decompose and remove the organic compound contained in the exhaust gas. The exhaust gas is released into the atmosphere.

  However, the noble metal-supported catalyst as described above has a problem that the cost is high because a noble metal such as Pt is supported on a high surface area support such as alumina. This is a serious problem when VOC treatment is performed on a huge amount of VOC-containing exhaust gas discharged from various factories, combustion exhaust gas from a diesel engine, or the like. Therefore, a low-cost catalyst that can replace the current noble metal-supported catalyst while ensuring sufficient resolution of VOC is desired.

In addition, the VOC treatment technique using the noble metal-supported catalyst as described above has the following problems. In other words, when a noble metal-supported catalyst is used, a very high decomposition rate is achieved under dry gas conditions that do not contain water vapor, but the decomposition rate is greatly reduced under conditions where water vapor is mixed. There's a problem. For example, when PdPt / Al ₂ O ₃ is used as a noble metal supported catalyst, dry gas conditions (CO ₂ : 15%, O ₂ : 5%, N ₂ : balance gas, space velocity SV (supply gas amount / catalyst filling amount) ): 12000h ⁻¹ , temperature: 150 ° C.), the decomposition rate was 98.2%, including water vapor (CO ₂ : 15%, O ₂ : 5%, H ₂ O: 9%, N ₂ : Balance gas), it drops to 25% (see Table 4). However, since the exhaust gas discharged from various factories contains about 2-3% of water vapor and the combustion exhaust gas contains about 8% of water vapor, the noble metal supported catalyst cannot be used as it is as a VOC decomposition catalyst. For this reason, it has been necessary to use or mix another catalyst component under conditions where water vapor can be mixed into the VOC, such as exhaust from a factory.

  Furthermore, the reheater used in the cracking and removing apparatus shown in FIG. 28 has the same size as that of the catalyst tower, and there is a problem that the equipment area and the installation area are large and high construction costs are required. In addition, such a decomposition / removal apparatus has a problem that it cannot be installed in an existing exhaust gas flow path because the installation area and the installation area become large.

JP 2001-38207 A JP-A-11-57470 JP 2001-58119 A

  Therefore, the present invention can exhibit a high VOC decomposition rate not only in dry gas conditions but also in the presence of water vapor without using a large-scale facility for heating the exhaust gas itself. An object of the present invention is to provide a VOC decomposing / removing apparatus and a decomposing / removing method using the same, which can realize lower costs than those used.

  A first aspect of the present invention that solves the above problems is a decomposition and removal apparatus that is provided in a flow path of exhaust gas and decomposes and removes a volatile organic compound contained in the exhaust gas. The decomposition and removal apparatus comprises heating means for directly or indirectly heating the catalyst and a catalyst layer made of ceria provided on the surface of the substrate.

  In such a first aspect, the VOC can be decomposed by the catalyst layer heated by the heating means simply by introducing the exhaust gas at normal temperature without heating, and not only under dry gas conditions but also in the presence of water vapor. It is possible to provide a VOC decomposition / removal apparatus that can exhibit a high VOC decomposition rate and that can achieve lower costs than those using a noble metal-supported catalyst.

  According to a second aspect of the present invention, there is provided the electric heater according to the decomposition / removal apparatus according to the first aspect, wherein the heating unit heats the base body or a heating medium provided in contact with the base body. It exists in the decomposition removal apparatus characterized by being.

  In the second aspect, the volatile organic compound in the exhaust gas can be decomposed only by energizing the heating device from a normal power source, and the decomposition / removal device can be downsized.

  According to a third aspect of the present invention, in the decomposition / removal apparatus according to the first or second aspect, the base is a plate-like member, and the catalyst layer is provided on both surfaces thereof. In the removal device.

  In the third aspect, the decomposition / removal device can be easily manufactured, and the cost of the decomposition / removal device can be further reduced.

  According to a fourth aspect of the present invention, in the decomposition / removal apparatus according to any one of the first to third aspects, the base is a honeycomb-shaped member including a plurality of gas processing flow paths communicating in the longitudinal direction. The decomposition / removal apparatus is characterized in that the catalyst layer is provided on an inner peripheral surface of the gas processing flow path.

  In the fourth aspect, the physical strength of the decomposition / removal apparatus can be improved, and the resolution of the decomposition / removal apparatus can be improved.

  According to a fifth aspect of the present invention, in the decomposition / removal apparatus according to the fourth aspect, a heating chamber provided in the longitudinal direction is provided at a boundary portion where a plurality of the gas processing flow paths are in contact with each other. In the decomposition and removal apparatus, the heating means is provided in the room.

  In the fifth aspect, the heating means of the decomposition / removal device can be more easily manufactured.

  According to a sixth aspect of the present invention, in the decomposition and removal apparatus according to any one of the first to fifth aspects, the heating means heats the catalyst layer to a predetermined temperature of 200 to 300 ° C. In the disassembly and removal device.

  In the sixth aspect, VOC (volatile organic compound) can be efficiently decomposed at a low temperature of 200 to 300 ° C.

  According to a seventh aspect of the present invention, the decomposition / removal device according to any one of the first to sixth aspects is provided in the middle of an exhaust passage for discharging environmental air to the outside. In the decomposition and removal method, the catalyst layer is heated to a predetermined temperature.

  In the seventh aspect, the VOC in the exhaust gas can be decomposed simply by providing a decomposition / removal device in the exhaust passage and heating the catalyst layer to a relatively low temperature of 200 to 300 ° C., and only under dry gas conditions. In addition, VOC can be decomposed at a high decomposition rate even in the presence of water vapor.

According to the cracking and removing apparatus according to the present invention, VOC can be decomposed at a decomposition rate equivalent to that using a noble metal-supported catalyst while using a catalyst (ceria: CeO ₂ ) that is lower in cost than the noble metal-supported catalyst. In addition, it is possible to provide a decomposition / removal apparatus that is reduced in cost while ensuring a predetermined decomposition / removability.

In addition, when ceria (CeO ₂ ) is used as a catalyst, it exhibits a high decomposition rate even in the presence of water vapor, so that when the water vapor is mixed in like a noble metal-supported catalyst, the decomposition rate is rapidly reduced. There is nothing. Accordingly, there is an advantage that it is not necessary to use or mix another catalyst component in the catalyst layer under conditions where water vapor can be mixed into the VOC such as exhaust from a factory.

In addition, according to the present invention, since ceria (CeO ₂ ) is used as a single catalyst without using a support as in the noble metal-supported catalyst, there is an effect that the catalyst is easily manufactured and handled. There is an advantage that a catalyst layer can be provided on a substrate without using a carrier.

  Furthermore, since the decomposition / removal apparatus of the present invention can be reduced in size, there is an advantage that the decomposition / removal apparatus can be modularized and easily installed in an existing exhaust gas flow path.

  Hereinafter, the best mode for carrying out the present invention will be described. The description of the present embodiment is an exemplification, and the present invention is not limited to the following description.

(Embodiment 1)
FIG. 1 is a schematic view showing an exhaust duct 100 in which a decomposition / removal device according to Embodiment 1 of the present invention is installed, and FIG. 2 is a schematic cross-sectional view of the decomposition / removal device 1 on the plane AA ′ shown in FIG. FIG. 3 is a schematic cross-sectional view of the disassembly / removal device 1 along the BB ′ plane shown in FIG. As shown in FIG. 1, the decomposition / removal device 1 according to the present embodiment is installed in an exhaust duct 100 of various factories, and the exhaust gas containing VOC is not released to the outside unless it passes through the decomposition / removal device 1. It is like that. Here, VOC refers to substances such as aliphatic hydrocarbons such as hexane, aromatic hydrocarbons such as benzene and toluene, and polycyclic aromatic hydrocarbons such as naphthalene, but is not limited thereto. . Among them, benzene, toluene and the like are volatile organic compounds used for a wide range of applications such as organic solvents and paints.

  Further, the decomposition / removal apparatus 1 according to the present embodiment has an electric heater (not shown) built therein, and a power source 50 is connected to the electric heater, and the catalyst layer constituting the decomposition / removal apparatus 1 is 200 to 200 as will be described later. It can be heated to 300 ° C.

  As shown in FIGS. 2 and 3, the decomposition / removal device 1 includes a cylindrical outer wall 10 and a plurality of plate-like members 20 attached in layers at predetermined intervals inside the outer wall 10. A plurality of gas processing flow paths 22 communicating in the longitudinal direction are formed. By configuring the cracking and removing apparatus 1 in this way, the contact area between a catalyst layer, which will be described later, and the exhaust gas passing through the cracking and removing apparatus 1 can be increased, and as a result, the resolution of the VOC can be improved. .

Next, the plate-like member 20 will be described. FIG. 4 is a schematic sectional view of the plate member 20. As shown in FIG. 4, the plate-like member 20 includes a heater 21 that is a base and a catalyst layer 25 containing CeO ₂ provided on both surfaces of the heater 21. Each heater 21 is connected to the power source 50 described above, and the heater 21 is heated by the power supplied from the power source 50 so that the temperature of the catalyst layer 25 can be maintained at 200 to 300 ° C. Yes.

By configuring the decomposition / removal device 1 in this way, VOC can be decomposed at a decomposition rate equivalent to that when a noble metal-supported catalyst is used while using a catalyst (CeO ₂ ) that is lower in cost than the noble metal-supported catalyst. Therefore, it is possible to provide the decomposition / removal device 1 which is reduced in cost while ensuring a predetermined decomposition / removability.

In addition, when ceria (CeO ₂ ) is used as a catalyst, it exhibits a high decomposition rate even in the presence of water vapor, so that when the water vapor is mixed in like a noble metal-supported catalyst, the decomposition rate is rapidly reduced. There is nothing. Therefore, there is an advantage that it is not necessary to use or mix another catalyst component in the catalyst layer 25 under conditions where water vapor can be mixed into the VOC such as exhaust from a factory.

In addition, according to the present invention, since the oxide (CeO ₂ ) is used as a single catalyst without using a support as in the noble metal-supported catalyst, there is an effect that the catalyst is easily manufactured and handled. Furthermore, there is an advantage that the catalyst layer 25 can be provided on the substrate (heater 21) without using a carrier.

  Furthermore, since the decomposition / removal device 1 of the present invention can be reduced in size, there is an advantage that the decomposition / removal device 1 can be modularized and easily installed in an existing exhaust gas passage.

  Next, the exhaust duct 100 in which the decomposition / removal apparatus 1 according to the present embodiment is installed and each component constituting the decomposition / removal apparatus 1 will be described. The exhaust duct 100 in which the decomposition / removal device 1 is installed is not particularly limited as long as it is an exhaust passage that discharges ambient air to the outside, that is, an exhaust passage that is used when exhaust gas containing VOC is discharged. It may be an exhaust duct installed in a factory.

  The outer wall 10 which comprises the decomposition | disassembly removal apparatus 1 will not be specifically limited if it has the heat resistance with respect to the heat | fever of 200-300 degreeC.

  The plate-like member 20 is not particularly limited as long as it has a heater 21 and a catalyst layer 25 described below. For example, the surface shape of the plate-like member 20 is not particularly limited, but a cross-sectional uneven shape, a cross-sectional corrugated shape, a cross-sectional chevron shape, etc. as shown in FIG. 5 are preferable. By adopting such a surface shape, the surface area of the catalyst layer 25 constituting the plate member 20 can be increased, and as a result, the resolution of the VOC can be improved.

  The heater 21 is not particularly limited as long as the temperature of the catalyst layer 25 can be maintained at 200 to 300 ° C.

The catalyst layer 25 is not particularly limited as long as CeO ₂ can act as a catalyst. Examples of the catalyst layer 25 include a layer in which an adhesive, a pressure-sensitive adhesive, or a sealing material is applied on the surface of the heater 21 and CeO ₂ powder is spread on the surface. Here, the adhesive, the pressure-sensitive adhesive, and the sealing material are not particularly limited as long as they have resistance to the catalytic action of CeO ₂ and have heat resistance to heat of 200 to 300 ° C., for example, a rigidizer (Tokyo Co., Ltd.). Materials) and the like.

Next, operation | movement of the decomposition | disassembly removal apparatus 1 which concerns on this embodiment is demonstrated. First, exhaust gas containing VOC is introduced into the exhaust duct 100. The introduced exhaust gas passes through the inside of the decomposition / removal device 1 installed in the exhaust duct 100. At that time, the exhaust gas comes into contact with the catalyst layer 25 provided on the surface of the plate-like member 20 and is heated to 200 to 300 ° C., and is decomposed by the catalytic action of CeO _{2 in} the catalyst layer 25, Will be removed. And the exhaust gas from which VOC was removed is discharged | emitted outside.

(Embodiment 2)
In the first embodiment, as shown in FIG. 2, the disassembly and removal apparatus includes a cylindrical outer wall 10 and a plurality of plate-like members 20 attached in layers inside the outer wall 10 with a predetermined interval therebetween. A plurality of gas processing flow paths 22 communicating in the direction are formed, but as shown in FIG. 6, a cylindrical outer wall 10 and a cross-sectional grid-shaped inner wall obtained by dividing the flow path inside the plurality of gas processing flow paths 22 A plurality of gas processing flow paths 22A that include the member 20A and communicate in the longitudinal direction may be formed. This is a so-called honeycomb-shaped decomposition / removal device, and the catalyst layer 25A may be provided on the surface of the inner wall member 20A. The cross-sectional shape of the gas processing flow path 22A formed by the inner wall member 20A is not particularly limited, such as a triangle, a rectangle, or a polygon.

As shown in FIG. 7, the inner wall member 20A includes a heater 21A having a lattice-like cross section as a base, and a catalyst layer 25A containing CeO ₂ provided on the inner peripheral surface of the heater 21A. . As in the first embodiment, each heater 21A is connected to a power source (not shown), and the heater 21A is heated by the power supplied from the power source to maintain the temperature of the catalyst layer 25A at 200 to 300 ° C. It can be done. FIG. 7 is a schematic enlarged cross-sectional view in which a portion X shown in FIG. 6 is enlarged.

  By configuring the decomposition / removal device 1A in this way, the physical strength of the decomposition / removal device 1A can be improved, and the contact area between the catalyst layer 25A and the exhaust gas passing through the decomposition / removal device 1A is increased. As a result, the resolution of VOC can be further improved.

  The heater 21A and the catalyst layer 25A constituting the inner wall member 20A are not particularly limited as long as they are the same as the heater 21 and the catalyst layer 25 according to the first embodiment. Since other components are the same as those of the disassembly / removal apparatus of the first embodiment, the same reference numerals are given and description thereof is omitted.

Moreover, in this embodiment, although the inner wall member was comprised as mentioned above, you may comprise as shown in FIG. As shown in FIG. 8, a catalyst layer 25B containing CeO ₂ is provided on the inner peripheral surface of a honeycomb-shaped substrate 27 that is a substrate constituting the inner wall member 20B. A cylindrical heating chamber 29 is provided in the boundary portion 28 of the base material 27 where a plurality of gas processing flow paths 22A are in contact with each other in the longitudinal direction, and a columnar heater 21B is provided in the heating chamber 29. Each is inserted. Each heater 21B is connected to a power source (not shown), and indirectly heats the base material 27 by heating the heater 21B with electric power supplied from the power source, thereby maintaining the temperature of the catalyst layer 25B at 200 to 300 ° C. Be able to.

  By configuring the inner wall member 20B in this way, the inner wall member 20B can be manufactured easily and at low cost. In addition, since the heater 21B can be easily replaced in the inner wall member 20B, even if the heater 21B in the inner wall member 20B fails, the inner wall member 20B can be used as it is by replacing the heater 21B. There is an effect that can be done.

  Although the base material 27 which comprises such an inner wall member 20B will not be specifically limited if it has the heat resistance of 200-300 degreeC, it cannot be overemphasized that a thing with high heat conductivity is preferable.

  The catalyst layer 25B is not particularly limited as long as it is the same as the catalyst layer 25 of the first embodiment.

  Furthermore, the heater 21B can be inserted into the heating chamber 29 and does not leak to the inner wall member when energized, and maintains the temperature of the catalyst layer 25B at 200 to 300 ° C. If it can do, it will not specifically limit. Since other components are the same as those of the disassembly / removal apparatus of the first embodiment, the same reference numerals are given and description thereof is omitted.

(Other embodiments)
In Embodiments 1 and 2, the catalyst layer is provided only on the surfaces of the plate-like member and the inner wall member, but the catalyst layer may be provided on the inner surface of the outer wall. In this case, it is necessary to provide a heater, a heating means for heating the outer wall itself, or the like between the outer wall and the catalyst layer, and keep the temperature of the catalyst layer at 200 to 300 ° C.

  By doing so, the contact area between the catalyst layer and the exhaust gas passing through the decomposition and removal apparatus can be further increased, and as a result, the resolution of VOC can be further improved.

[Example 1]
First, a VOC decomposition catalyst applicable to combustion exhaust gas and the like was screened from the viewpoint of finding a catalyst having excellent low-temperature activity and low cost. Hereinafter, the contents of this experiment will be described in detail as Example 1 with reference to the drawings. As described below, ceria (CeO ₂ ) is the most suitable catalyst from this viewpoint.

1. VOC decomposition catalysts As VOC decomposition catalysts, various studies have been carried out using TiO ₂ and their complex oxides in photolysis, and catalysts supporting precious metals such as Pt with Al ₂ O ₃ as a support mainly in catalytic oxidation methods. Yes. On the other hand, the present inventor made TiO ₂ , iron oxide (Fe ₂ O ₃ ) and TiO ₂ (Kanto Chemical Co., Anatase), copper oxide (CuO; Kanto Chemical Co., Ltd.) produced by an ultrafine particle production / composite device. ), Al ₂ O ₃ (Sumitomo Chemical Co., Ltd., TA-1301), zirconia (ZrO ₂ ; first rare element chemical industry, RC-100), ceria (CeO ₂ ; first rare element chemical industry, HS), Nine kinds of oxide catalysts, ZrO ₂ CeO ₂ (1st rare element chemical industry, ACZ-58) and TiO ₂ ZrO ₂ (1st rare element chemical industry), are selected to actually decompose benzene. It was. In addition, PdPt-supported catalysts (PdPt / Al ₂ O ₃ ) and PdPt / Al ₂ O ₃ , which have been studied for low-temperature oxidation of methane at the Central Research Institute of Electric Power, the applicant of the present invention, are used as promoters. Catalysts added with ZrO ₂ , CeO _2, etc. (PdPt / ZrO ₂ , PdPt / CeO ₂ , PdPt / ZrO ₂ CeO _2, etc.), Pd supported catalysts (Pd / Al ₂ O ₃ ), Pt supported catalysts (Pt / Al 6 kinds of noble metal supported catalysts such as ₂ O ₃ ) were tried as potential VOC decomposition catalysts. Table 2 shows the specifications of each noble metal supported catalyst. The various catalysts were sized to 9 to 16 mesh after press molding (for example, the openings were 2 mm (8.6 mesh) and 1 mm (16 mesh)), and were used for physical property analysis and reaction test of the catalyst.

2. Physical Property Analysis Specific surface area, which is an important factor in comparing and evaluating the catalyst performance, and the amount of CO adsorbed on the metal component as the active component on the surface of the noble metal-supported catalyst were measured. The specific surface area was measured using an automatic specific surface area measuring device (Micromeritics, GEMINI 2360) based on the BET method. The amount of chemical adsorption by CO was measured using a fully automatic catalytic gas adsorption amount measuring device (Okura Riken, MODEL R6015). This device utilizes the property that the active component on the surface of the catalyst or the like chemically adsorbs the active gas such as CO and H _2. The active gas is introduced into the catalyst in a pulse shape and the total adsorption amount is measured. . Note that this device complies with the measurement method of the Catalysis Society of Japan. As a pretreatment, the temperature was raised from room temperature to 400 ° C. at 10 ° C./min as a pretreatment, hydrogen reduced at 400 ° C. for 15 minutes, then degassed for 15 minutes, and then cooled at 10 ° C./min. Held at 0C. Next, while measuring the CO concentration at the sample outlet with a thermal conductivity type detector (TCD), 49.7% CO was supplied to the sample in a pulsed manner in a helium stream, and CO adsorption up to the saturation point was achieved. The amount was measured.

3. VOC Decomposition Reaction Test FIG. 11 shows an experimental apparatus used for the VOC decomposition reaction test. Quartz reaction tube 202 was filled with 2 ml of catalyst 1 and the front and back of catalyst 201 were fixed with quartz wool (not shown). The reaction tube 202 filled with the catalyst 201 was installed in the tubular electric furnace 203, and after raising the temperature to a predetermined temperature, the reaction test was started under the experimental conditions shown in Table 3. Benzene (special reagent grade:> 99.5%, manufactured by Kanto Chemical Co., Inc.) was injected into the glass diffusion tube 204, and then maintained at a constant temperature, and a diluted gas was generated by flowing nitrogen at a constant flow rate. Further, the water vapor was introduced by bubbling water at a constant temperature in the water vapor generation unit 205. The gas flow path containing benzene and water vapor was kept at 120 ° C. or higher by a ribbon heater (the portion heated by the ribbon heater is indicated by hatching in the drawing). The VOC concentration in the exhaust gas from various fixed sources is about several ppm to several hundred ppm in chemical factories, etc., and several ppm to about 20 ppm in waste treatment. Controlled. The benzene concentration was measured using a gas detector tube (manufactured by Gastec). The remaining gas that was not sampled was exhausted after passing through a water trap 206 and activated carbon 207.

4). Experimental Results 4-1 Benzene Decomposition Reaction Test Results with Various Catalysts FIG. 12 shows the benzene decomposition reaction test results of main oxide catalysts and noble metal-supported catalysts. Assuming combustion exhaust gas composition as experimental conditions, first, a reaction test was performed at CO ₂ : 15%, O ₂ : 5%, a gas flow rate of 400 ml / min (space velocity SV: 12000 h ⁻¹ ), and a reaction temperature of 150 ° C. Such as _{TiO 2, Al 2 O 3,} CeO 2, ZrO 2 CeO 2, 9 types of showing the resolution in the oxide catalyst of _{CeO 2,} ZrO 2 _CeO 2 alone, the other seven oxide catalyst It did not show resolution. CeO ₂ showed a decomposition rate of 45% as an initial activity, but then decreased to 20% or less and was stabilized as it was. ZrO ₂ CeO ₂ showed a decomposition rate equivalent to CeO ₂ until 30 minutes after the start of the reaction, but did not show decomposition performance after 60 minutes. On the other hand, six types of Pd / Al ₂ O ₃ , Pt / Al ₂ O ₃ , PdPt / Al ₂ O ₃ , PdPt / ZrO ₂ , PdPt / CeO ₂ and PdPt / ZrO ₂ CeO ₂ A high decomposition rate was exhibited, and a decomposition rate of 98% or more was obtained.

In addition, with respect to 30 minutes after the start of the reaction, the oxide catalysts CeO ₂ and ZrO ₂ CeO ₂ only had a decomposition rate of about 10 to 15% under the dry gas conditions, respectively, whereas the noble metal supported catalyst Six of them showed a decomposition rate of 98% or more under dry gas conditions (see (i) in Table 4).

For CeO ₂ that showed resolution in the oxide catalyst, Pd / CeO ₂ carrying Pd (Pd carrying amount: 1 wt%) was prepared by an impregnation method, and a reaction test was attempted. As shown in FIG. 12, the decomposition rate greatly increased from 15% to 55% by loading Pd, but it was about half of Pd / Al ₂ O ₃ and PdPt / Al ₂ O ₃ . Table 5 shows initial physical properties of CeO ₂ and ZrO ₂ CeO ₂ , which showed resolution among the seven kinds of noble metal-supported catalysts and oxide catalysts. CeO ₂ has about 150 meters ² / g and high specific surface area, after Pd on was also nearly twice about 112m ² / g of other noble metal supported catalysts. However, the CO adsorption amount was less than half of PdPt / Al ₂ O ₃ and Pd / Al ₂ O ₃ , and it was assumed that this difference appeared in the resolution.

The combustion exhaust gas contains water vapor together with VOC. Therefore, the test was conducted at CO ₂ containing 15% of CO ₂ : 15%, O ₂ : 5%, a gas flow rate of 400 ml / min (SV: 12000 h ⁻¹ ), and a reaction temperature of 150 ° C. As the catalyst, seven kinds of noble metal-supported catalysts such as PdPt / Al ₂ O ₃ and PdPt / ZrO ₂ CeO ₂ which showed high decomposition rate under dry gas conditions, and CeO ₂ and ZrO ₂ CeO which showed resolution among oxide catalysts. ₂ was selected.

FIG. 13 shows the experimental results of various catalysts. In Pd / Al ₂ O ₃ , PdPt / Al ₂ O ₃ , PdPt / ZrO _2, etc., the decomposition rate was greatly reduced by the presence of water vapor, and Pd / Al ₂ O ₃ was particularly reduced to 20% or less. Four types of PdPt-supported catalysts obtained by adding Pt to Pd / Al ₂ O ₃ showed a higher decomposition rate than Pd / Al ₂ O ₃ , and the effect of combining active components was revealed. In comparison with the carrier component differences, _Al 2 _{O 3} alone is PdPt / _Al 2 _{O 3} is most decomposition rate is low, then the order of _{PdPt / ZrO 2, PdPt / CeO} 2, PdPt / ZrO 2 CeO 2 became. On the other hand, Pt / Al ₂ O ₃ maintained a decomposition rate of 70% or more, and it became clear that the influence of water vapor was less than that of Pd / Al ₂ O ₃ and PdPt-supported catalysts. On the other hand, with regard to CeO ₂ , it was found that the decomposition rate was rather improved by the presence of water vapor (see (i) and (ii) in Table 4).

4-2 Effect of space velocity (SV) Exhaust gas from chemical factories, petrochemical plants, and various combustion processes contains water vapor along with VOC components, and water vapor is one of the causes of catalyst deterioration, shortening catalyst life. To do. Therefore, the catalyst performance is improved by improving the catalyst such as addition of a promoter. Besides the gas composition such as water vapor, the residence time of the catalyst and the reaction temperature are important factors that determine the catalyst performance. Therefore, in this example, first, the change in the decomposition rate was examined by lowering the SV. The experimental conditions were a reaction temperature of 300 ° C. and SV = 6000 h ⁻¹ under the same conditions as the water vapor introduction test in FIG. Three types of catalysts, Pt / Al ₂ O ₃ , PdPt / ZrO ₂ CeO ₂ , and PdPt / CeO ₂ were selected.

As shown in the reaction test results in FIGS. 9 and 14, an increase in the decomposition rate was confirmed by lowering SV in each catalyst. The decomposition rates of PdPt / ZrO ₂ CeO ₂ and PdPt / CeO ₂ increased to about 65%, but were below the decomposition rate of Pt / Al ₂ O ₃ at SV = 12000 h ⁻¹ . On the other hand, it has been found that Pt / Al ₂ O ₃ can obtain a decomposition rate almost equal to that of the dry gas condition.

4-3 Effect of reaction temperature By lowering SV, Pt / Al ₂ O ₃ showed the same decomposition performance as that under dry gas conditions, but PdPt / ZrO ₂ CeO ₂ and PdPt / CeO ₂ The decomposition rate of Al ₂ O ₃ was less than or equal to SV = 12000 h ⁻¹ . Then, the change when reaction temperature was raised about PdPt / ZrO ₂ CeO ₂ was examined.

FIG. 15 shows the result of increasing the reaction temperature with the same gas composition and SV = 6000 h ⁻¹ as in the water vapor introduction test. It was confirmed that the decomposition rate greatly increased as the reaction temperature increased, and that a decomposition rate equivalent to Pt / Al ₂ O ₃ was obtained at 180 ° C. Therefore, the catalyst was further narrowed down to Pt / Al ₂ O ₃ and PdPt / ZrO ₂ CeO _2, and the change when the reaction temperature was increased in the steam introduction test at SV = 12000 h ⁻¹ was examined. As shown in FIG. 15, it was revealed that a decomposition rate equivalent to dry gas conditions can be obtained at 180 ° C. for Pt / Al ₂ O _{3 and} 200 ° C. for PdPt / ZrO ₂ CeO ₂ . Regarding CeO ₂ , it became clear that a decomposition rate of 98% or more equivalent to Pt / Al ₂ O ₃ and PdPt / ZrO ₂ CeO ₂ was obtained at SV = 6000 h ⁻¹ and 300 ° C. (FIG. 10). reference).

From the above results, in the case of ZrO ₂ CeO ₂ and CeO ₂ which are the same oxide catalysts, a certain increase in the decomposition rate was recognized by increasing the reaction temperature. The change in rate was not recognized, and it was far from the target decomposition rate. However, with regard to CeO ₂ , since the decomposition rate was 98% or more by reducing the SV to 6000 h ⁻¹ and setting the reaction temperature to 300 ° C., CeO ₂ is a low-cost VOC that can replace the noble metal supported catalyst. It proved to be promising as a decomposition catalyst (see FIG. 10, Table 4 (v)).

From these results, Pt / Al ₂ O ₃ and PdPt / ZrO ₂ CeO ₂ can be applied as a decomposition catalyst for VOC by setting SV to 6000 h ⁻¹ or a reaction temperature of 180 ° C. or higher even in a gas composition containing water vapor. I found it possible.

4-4 Reaction characteristics of CeO ₂ It was confirmed that the influence of water vapor was large in various catalysts. However, although CeO ₂ has a low decomposition rate as shown in FIG. 16, there is almost no influence of water vapor. In addition, although a noble metal-supported catalyst such as Pt has high catalytic performance, on the other hand, since it is expensive, a cheaper oxide catalyst such as CeO ₂ is desirable from the viewpoint of cost. Therefore, in order to improve the decomposition rate with CeO ₂ , the reaction test was attempted with SV reduced to 6000 h ⁻¹ . In the noble metal supported catalyst, the effect of SV was confirmed, but in CeO ₂ , the decomposition rate was only slightly higher at the initial stage of the reaction, and both SV = 12000h ⁻¹ and 6000h ⁻¹ were 20% or less, and the effect of SV was It was not confirmed. Therefore, as with the noble metal-supported catalyst, an attempt was made to increase the reaction temperature. As shown in FIG. 17, there was no significant change in the decomposition rate up to the reaction temperature of 220 ° C., but the temperature gradually increased from 250 ° C. to 300 ° C. It became clear that the decomposition rate was equivalent to Pt / Al ₂ O ₃ and PdPt / ZrO ₂ CeO ₂ . However, since the reaction gas was measured with a gas detector tube (manufactured by Gastec) having a low detection capability, there was a concern that an accurate reaction gas amount at a reaction temperature of 250 ° C. or higher could not be measured. Therefore, in Example 2, as a result of detecting the reaction gas by gas chromatography, as will be described in detail later, a decomposition rate of 95% is obtained at a reaction temperature of 400 ° C., SV = 5600 h ⁻¹ , and a water vapor concentration of about 9%. In the vicinity of ° C., the decomposition rate was about 30%.

As described above, as a result of screening with an oxide catalyst and a noble metal-supported catalyst as a VOC decomposition catalyst in the simulated combustion exhaust gas, the following results were obtained.

(1) CO ₂ : 15%, O ₂ : 5%, gas flow rate 400 ml / min (space velocity SV: 12000 h ⁻¹ ), benzene decomposition reaction test at a reaction temperature of 150 ° C., Pd / Al ₂ O ₃ , Pt It was revealed that noble metal supported catalysts such as / Al ₂ O ₃ and PdPt / ZrO ₂ CeO ₂ exhibit high catalytic performance.

(2) In reaction tests with various catalysts, it was found that the decomposition rate was greatly reduced by the presence of water vapor. However, the decrease in SV (12000 h ⁻¹ → 6000 h ⁻¹ ), Pt / Al ₂ O ₃ , PdPt / ZrO ₂ CeO ₂ at a reaction temperature of 180 ° C. or higher can provide catalytic performance equivalent to that under dry gas conditions. I found it.

(3) Among various catalysts, CeO ₂ is hardly affected by water vapor, and in the presence of water vapor, SV = 6000 h ⁻¹ , and reaction temperature of 300 ° C., Pt / Al ₂ O ₃ , PdPt / ZrO It has been found that the catalyst performance is equivalent to ₂ CeO ₂ and is promising as a VOC decomposition catalyst that is cheaper than an expensive noble metal catalyst. However, as described above, the reaction gas was detected by the gas chromatograph in Example 2, and as a result, the reaction temperature was 400 ° C., SV = 5600 h ⁻¹ , and the water vapor concentration was about 9%. Then, the decomposition rate was about 30%.

[Example 2]
Next, experiments were conducted on ceria (CeO ₂ ) that can be used as a catalyst for decomposing VOC contained in factory exhaust gas and the like, and suitable reaction conditions at that time. In the experiment, the effects of SV, reaction temperature, and water vapor concentration in the VOC decomposition reaction were examined when VOC was benzene or toluene.

1. Benzene or Toluene Decomposition Test For the benzene or toluene decomposition reaction test, the same experimental apparatus as in FIG. 11 was used. A quartz reaction tube 202 was filled with 2 to 2.7 ml of ceria (CeO ₂ ; first rare element chemical industry, HS) as a catalyst 201, and the front and back of the catalyst 201 were fixed with quartz wool (not shown). The reaction tube 202 filled with the catalyst 201 was installed in the tubular electric furnace 203, and after raising the temperature to a predetermined temperature, the reaction test was started. Benzene (special reagent grade:> 99.5%, manufactured by Kanto Chemical Co., Inc.) or toluene (special reagent grade:> 99.5%, manufactured by Kanto Chemical Co., Ltd.) is injected into the glass diffusion tube 204 and then kept at a constant temperature, Diluted gas was generated by flowing a constant flow rate. Further, the water vapor was introduced by bubbling water at a constant temperature in the water vapor generation unit 205. The flow path of the gas containing benzene and water vapor or toluene and water vapor was kept at 130 ° C. or higher by a ribbon heater (the portion heated by the ribbon heater is indicated by hatching in the drawing). Assuming the combustion exhaust gas composition, the reaction conditions are such that the total gas flow rate of 15% CO ₂ , 5% O ₂ and N ₂ balance gas is 250 to 400 ml / min (space velocity SV: 5600 to 12000 h ⁻¹ ), and the reaction temperature. The reaction test was conducted at 150 ° C. The VOC concentration in the exhaust gas from various fixed sources varies from several ppm to several hundred ppm at chemical factories and several ppm to 20 ppm in waste treatment, but this time, the range that can be stably supplied from the VOC generator Benzene (about 30-40 ppm) or toluene (80, 220-230 ppm) was introduced. The reaction gas is not the gas detector tube (made by Gastec) used in Example 1, but a gas chromatograph (Shimadzu: C-R14A CHROMATAPAC, detector: FID) for the purpose of increasing measurement accuracy. And measured.

2. Product analysis after toluene decomposition reaction After the decomposition reaction of toluene, the reaction gas was detected by gas chromatography. As a result, toluene and a very small amount of benzene were detected, but other components were not confirmed. Then, the gas after reaction was qualitatively analyzed by GC-MS (Yokogawa Analytical System Co., Ltd .: 5973A-N series GC / MSD system), and the gas composition after toluene decomposition reaction was examined.

3. Experimental results 3-1. Effect of reaction temperature and SV under dry gas condition of benzene FIG. 18 shows the result of detailed examination of the effect of reaction temperature and SV under the dry gas condition of benzene. In 0.99 ° C., SV is from 30 to 33% at 6000h ^-1 or less, although the 6900H ^-1 or higher showed 20% or less and a low decomposition performance, raising the reaction temperature to 180 ° C., decomposition ratio of each SV is It was greatly improved and a decomposition rate of 95% or more was obtained when SV was 6000 h ⁻¹ or less. When the temperature was further increased, the decomposition rate gradually decreased, but showed a tendency to increase again from 300 ° C. When the SV was 8000h ^-1 or less, the decomposition rate was 95% or more at 350 ° C and 99% or more at 400 ° C. Obtained. Moreover, 99% or more was exhibited at 400 ° C. even at 12000 h ⁻¹ . Since no difference in decomposition rate due to the SV value was observed at 400 ° C., it seems that the reaction value of 400 ° C. or higher is not affected by the SV value. Therefore, when the exhaust gas containing VOC discharged from a factory or the like is at a low temperature, it is preferable to raise the temperature using waste heat using a heat exchanger or the like. From these results, it was found that it is preferable to set SV to 5600 h ⁻¹ in order to obtain the target performance at a lower temperature. Therefore, in the following, experiments were performed with SV set to 5600 h ⁻¹ .

  In each SV, it was confirmed that the decomposition rate decreased from 200 ° C. or higher and the temperature dependency increased again at 300 ° C. or higher. In this reaction test, the decomposition rate is calculated from the difference in benzene concentration at the catalyst inlet and outlet. This phenomenon is that from the start of the reaction to 200 ° C, benzene is gradually adsorbed on the catalyst surface and a decomposition reaction occurs and the decomposition rate increases, but when it exceeds 200 ° C, benzene not adsorbed on the catalyst surface passes as it is. Therefore, at 200 ° C. or higher, the outlet concentration increases and the decomposition rate decreases. Furthermore, it was speculated that the decomposition rate increased again due to the activity of the catalyst surface increasing at 300 ° C. or higher.

3-2. Effect of water vapor concentration on benzene decomposition reaction The effect of water vapor was examined for SV of 5600 h ⁻¹ . The water vapor concentration assumed in the exhaust gas ranges from about 8% of the combustion gas level to 2 to 3% which is the exhaust gas level in various factory facilities other than the combustion process. Therefore, the water vapor concentration was controlled so that the exhaust gas level in various factories was about 2% to about 10% above the combustion exhaust gas level. FIG. 19 shows the results of the water vapor introduction test. Compared to FIG. 18, a decrease in the decomposition rate was confirmed due to the presence of water vapor, but at a water vapor concentration of 2.07%, 6.05%, and 7.34%, the decomposition rate increased from 300 ° C. or higher. It was confirmed that a decomposition rate of 95% or more was obtained at 400 ° C. It was also confirmed that the decomposition rate increased from 300 ° C. or higher even at a water vapor concentration of 8.84% and 10.83%, and a decomposition rate of 90% or higher was obtained at 400 ° C.

From the above results, although the decomposition rate decreases somewhat due to the mixing of water vapor, when the water vapor concentration is 11% or less, the decomposition rate is improved from 300 ° C. or higher, and sufficient decomposition performance can be obtained by increasing to 400 ° C. It was confirmed to show. That is, if the reaction temperature is 300 ° C. or higher with respect to the water vapor concentration (2 to 3%) contained in the exhaust gas from the factory or the like, as well as the water vapor concentration (8%) at the combustion exhaust gas level, CeO ₂ It was confirmed that the present invention is sufficiently applicable to the benzene decomposition reaction.

3-3. Effect of reaction temperature on decomposition reaction of toluene From the results of benzene decomposition reaction tests, it was confirmed that the decomposition rate was 90% or higher at 400 ° C. or higher under the same conditions. The same decomposition was applied to VOC components other than benzene. Performance is desired. Therefore, the decomposition performance of toluene, which is used for various applications among the VOC components and has a high emission ratio among the VOC emission amounts, was examined. In various factories that generate toluene, especially in printing and painting facilities, the need for VOC countermeasures is increasing, and its emission concentration varies from tens of ppm to several hundred ppm depending on the source, depending on the type of industry. First, decomposition performance at 100 ppm or less was examined. The reaction conditions were a toluene concentration of 80 ppm, a reaction gas of 15% CO ₂ , 5% O ₂ and N ₂ balance gas with a total gas flow rate of 250 ml / min (SV: 5600 h ⁻¹ ) and a reaction temperature of 150 ° C. to 300 ° C. The reaction test was conducted.

  A symbol Δ in FIG. 20 shows a toluene reaction test result under dry gas conditions. Although the decomposition rate was about 35% at 150 ° C, the decomposition rate suddenly increased when the temperature was raised to 180 ° C. A decomposition performance of 99% or higher was obtained at 200 ° C, and a higher decomposition rate was obtained at a lower temperature than benzene. It became clear that

Next, the effect of water vapor was examined. The result of the toluene reaction test in the presence of water vapor is indicated by symbol ◯ in FIG. The water vapor concentration is controlled to 3% or less, which is the water vapor level in exhaust gas from various factory facilities that are the source of toluene, and is a total gas of 15% CO ₂ , 5% O ₂ and N ₂ balance gas including water vapor. The test was conducted at a flow rate of 250 ml / min (SV: 5600 h ⁻¹ ) and at a reaction temperature of 150 to 300 ° C. At 150 ° C, the decomposition rate is as low as about 8%. However, as with dry gas conditions, the decomposition rate increases greatly at 180 ° C, with 95% or more at 180 ° C, 97% or more at 200 ° C, and about 300% at 300 ° C. It was revealed that 99% decomposition performance was obtained. Therefore, when the water vapor concentration was 3% or less and the toluene concentration was 80 ppm or less, it was confirmed that CeO ₂ was sufficiently applicable to the toluene decomposition reaction if the reaction temperature was 180 ° C. or higher. If the reaction temperature is 400 ° C. or higher, both benzene and toluene can be decomposed by 99% or more.

  As described above, toluene is used for many purposes, and the VOC concentration in the exhaust gas varies from several tens ppm to 100 ppm or more depending on the generation source. Therefore, in order to examine the influence of the inlet concentration, a reaction test with increasing toluene concentration was conducted. The toluene concentration was controlled at a concentration range in which toluene could be stably supplied from the VOC generation part of the present reactor, and was about 220 ppm. FIG. 21 shows the reaction test results. Similar to the result of 80 ppm, the decomposition rate rapidly increased from 180 ° C., showed a decomposition performance of 98% or more at 200 ° C., and it was confirmed that there was no influence of the inlet concentration.

Next, the influence of the SV and water vapor concentration when the inlet concentration was high (220 to 230 ppm) was examined. FIG. 22 shows the results of a reaction test in which the SV is 5600 to 10,000 h ^{−1 at} a water vapor concentration of 3% or less. The decomposition performance under each condition increased as the reaction temperature increased, and a decomposition rate of 90% or more was obtained at 180 ° C., and a decomposition rate of 95% or more was obtained at 300 ° C.

Next, FIG. 23 shows the reaction test results when the water vapor concentration at 5600 h ⁻¹ is about 2% to 10%. Increasing the reaction temperature from 150 ° C. to 180 ° C. increases the decomposition rate, and the decomposition performance slightly decreases as the water vapor concentration increases. However, when the water vapor concentration is 7% or less, the decomposition rate is 90% or higher. When the concentration was 10%, it was revealed that the decomposition rate was about 80%.

Therefore, when the water vapor concentration is 10% or less, it was confirmed that CeO ₂ can be sufficiently applied to the toluene decomposition reaction if the reaction temperature is 180 ° C. or higher.

3-4. Product Analysis after Toluene Decomposition Reaction FIG. 24 shows the results of qualitative analysis of the gas after the toluene decomposition reaction by GC-MS. From this result, only the unreacted toluene was detected as the VOC component, and it was confirmed that no other VOC component was produced. The reason why benzene was not detected is considered to be due to adhesion to the collected pack or the change with time. Therefore, it was confirmed that generation of new VOCs other than toluene and benzene does not occur due to the decomposition reaction of toluene.

As described above, as a result of examining the effects of SV, temperature, and water vapor concentration in the VOC decomposition reaction when CeO ₂ is used as the VOC decomposition catalyst in the case where VOC is benzene and toluene, the following knowledge was obtained.

(1) Benzene decomposition reaction test Under a dry gas condition, a decomposition performance of 99% or more is obtained at 400 ° C, and it is clear that SV = 5600h ^-1 shows a high decomposition rate of 97% or more even at a lower temperature. became. As a result of the steam introduction test at SV = 5600 h ⁻¹ , 90% at 400 ° C. at a steam concentration of about 11% and 97% or more at about 2% were obtained. Performance was confirmed.

(2) Toluene decomposition reaction test The dry gas shows a decomposition performance of 98% or higher at 180 ° C or higher, and the water vapor introduction test (water vapor concentration of 3%, SV: 5600h ^-1 ) has a decomposition performance of 95% or higher at 180 ° C or higher. Indicated. It was also confirmed that there was no effect on the decomposition performance even when the inlet concentration (80 ppm, 220 ppm) was changed. Further, when SV is 10000 h ⁻¹ or less (water vapor concentration 3% or less), the decomposition temperature shows 90% or more at a reaction temperature of 180 ° C., and when the water vapor concentration is 10% or less (SV: 5600 h ⁻¹ ), the reaction temperature. It was revealed that the decomposition performance was 80% or more at 180 ° C. Therefore, it was confirmed that CeO ₂ is sufficiently applicable as a VOC decomposition catalyst.

  Further, as a result of GC-MS analysis of the reaction product gas, only unreacted toluene was detected, and it was confirmed that no other VOC component was produced. That is, it was confirmed that the generation of new VOCs other than toluene and benzene does not occur due to the decomposition reaction of toluene.

The above results were obtained under the condition that the concentration of water vapor in the gas was 11% or less in the case of benzene and 10% or less in the case of toluene. The conditions to which the present invention is applicable are not limited to these examples, and CeO ₂ can be sufficiently applied as a VOC decomposition catalyst even in a range where the water vapor concentration is different or in dry gas.

In addition, in the present specification, “conditions in which water vapor is present in the gas” refers to, for example, when water vapor is originally contained in the exhaust gas as in the case of fossil fuel combustion exhaust gas, and water vapor is artificially introduced. This is also included. Therefore, CeO ₂ can be sufficiently applied as a VOC decomposition catalyst even to a gas in which water vapor is artificially injected into the dry gas, for example, in the case of VOC treatment with a conventional noble metal supported catalyst. It is.

[Example 3]
As described above, since CeO ₂ is sufficiently applicable as a VOC decomposition catalyst, a VOC decomposition / removal apparatus using CeO ₂ was prepared and its resolution was measured.

1. Creation of decomposition / removal device After applying rigidizer (manufactured by Tokyo Materials Co., Ltd.) as a sealing material on heat-resistant glass 310 having a length of 152 mm, a width of 22 mm, and a thickness of 1 mm, a powder of CeO ₂ was sprayed thereon. Then, heat treatment was performed at 300 ° C. for 2 hours in an air atmosphere to obtain a test piece in which a catalyst layer 320 having a thickness of about 0.5 mm as shown in FIG. 25 was provided on one surface.

  Two test pieces were prepared, and a test apparatus 300 as shown in FIG. 26 was prepared. Specifically, a plate-like heater 330 is attached to the other surface of each test piece, and two test pieces are arranged in a rectangular tube 350 so that the surface on which the catalyst layer 320 is provided faces each other. A test apparatus 300 was created.

2. Toluene decomposition / removal test In the test apparatus 300 described above, while each test piece was heated by the heater 330, an exhaust gas composed of the components shown in Table 6 was flowed at a flow rate of 250 ml / min, and the decomposition rate of the exhaust gas by this test apparatus was tested. Measured at each piece temperature.

The obtained result is shown in FIG. Here, AV is a numerical value (m / h) calculated by [gas flow rate (m ³ / h)] / [catalyst area (m ² )]. As shown in FIG. 27, it was found that when the temperature of the test piece was 200 ° C. or higher, the decomposition rate was 80% or higher, and particularly at about 300% at 300 ° C. That is, in this test apparatus, when the temperature of the test piece was 200-300 degreeC, it turned out that toluene can fully be decomposed | disassembled.

FIG. 3 is a schematic diagram illustrating an exhaust duct according to the first embodiment. It is a schematic sectional drawing of the decomposition | disassembly removal apparatus in the A-A 'surface shown in FIG. It is a schematic sectional drawing of the decomposition | disassembly removal apparatus in the B-B 'surface shown in FIG. 3 is a schematic cross-sectional view of a plate-like member according to Embodiment 1. FIG. 3 is a schematic cross-sectional view showing an example of a plate-like member according to Embodiment 1. FIG. It is a schematic sectional drawing of the decomposition | disassembly removal apparatus which concerns on Embodiment 2. FIG. It is the schematic expanded sectional view which expanded the part X shown in FIG. 6 is a schematic enlarged cross-sectional view showing an example of an inner wall member according to Embodiment 2. FIG. It is a graph which shows the result (effect of SV) of the benzene decomposition reaction test in Example 1. 2 is a graph showing the results of benzene decomposition reaction test in Example 1 (effect of reaction temperature). 1 is a configuration diagram of a VOC decomposition reaction test apparatus in Example 1. FIG. 2 is a graph showing the results of a benzene decomposition reaction test in Example 1. 4 is a graph showing the results of a water vapor introduction test in Example 1. It is a graph which shows the result (effect of SV) of the benzene decomposition reaction test in Example 1. 2 is a graph showing the results of benzene decomposition reaction test in Example 1 (effect of reaction temperature). ₂ is a graph showing the influence of water vapor on CeO ₂ in Example 1. FIG. ₂ is a graph showing the influence of reaction with CeO ₂ in Example 1. FIG. It is a graph which shows the result (effect of SV with dry gas) of the benzene decomposition reaction test in Example 2. It is a graph which shows the result (effect of water vapor) of the benzene decomposition reaction test in Example 2. It is a graph which shows the result (effect of water vapor | steam) of the toluene decomposition reaction test in Example 2. It is a graph which shows the result (effect of inlet_port | entrance concentration) of the toluene decomposition reaction test in Example 2. It is a graph which shows the result (effect of SV) of the toluene decomposition reaction test in Example 2. It is a graph which shows the result (effect of water vapor | steam) of the toluene decomposition reaction test in Example 2. It is a figure which shows the result of having analyzed the gas after the decomposition reaction of toluene in Example 2 by GC-MS. 6 is a schematic cross-sectional view of a test piece in Example 3. FIG. It is a schematic sectional drawing of the decomposition | disassembly removal apparatus in Example 3. FIG. 6 is a graph showing the relationship between the decomposition rate and temperature in Example 3. It is the schematic of the conventional decomposition | disassembly removal apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1A decomposition | disassembly removal apparatus 10 Outer wall 20 Plate-shaped member 20A, 20B Inner wall member 21, 21A, 21B Heater 22, 22A Gas treatment flow path 25, 25A, 25B Catalyst layer 27 Base material 28 Boundary part 29 Heating chamber 50 Power supply 100 Exhaust Duct 201 Catalyst 202 Reaction tube 203 Tubular electric furnace 204 Glass diffusion tube 205 Water vapor generation unit 206 Water trap 207 Activated carbon 300 Test apparatus 310 Heat resistant glass 320 Catalyst layer 330 Heater 350 Tube

Claims (7)

A decomposition / removal device provided in a flow path of exhaust gas for decomposing and removing a volatile organic compound contained in the exhaust gas, a base, heating means for directly or indirectly heating the base, and the base And a catalyst layer made of ceria provided on the surface of the catalyst. 2. The decomposition / removal apparatus according to claim 1, wherein the heating means is an electric heater that heats the substrate by heating the substrate or a heating medium provided in contact with the substrate. 3. The decomposition / removal apparatus according to claim 1, wherein the base is a plate-like member, and the catalyst layers are provided on both surfaces thereof. 4. The decomposition / removal apparatus according to any one of claims 1 to 3, wherein the base is a honeycomb-shaped member including a plurality of gas processing channels communicating in a longitudinal direction, and an inner peripheral surface of the gas processing channel. The decomposition / removal apparatus is characterized in that the catalyst layer is provided on the surface. The decomposition / removal apparatus according to claim 4, wherein a heating chamber provided in the longitudinal direction is provided at a boundary portion where a plurality of the gas processing flow paths are in contact, and the heating means is provided in the heating chamber. A disassembly and removal apparatus characterized by the above. 6. The decomposition and removal apparatus according to claim 1, wherein the heating unit heats the catalyst layer to a predetermined temperature of 200 to 300 ° C. 6. The decomposition and removal apparatus according to any one of claims 1 to 6 is provided in the middle of an exhaust passage for discharging environmental air to the outside, and the catalyst layer is heated to a predetermined temperature of 200 to 300 ° C by the heating means. A decomposition and removal method characterized by the above.

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