JP2011056191A - Method and apparatus for decomposing floating organic compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for decomposing a floating organic compound, which is capable of decomposing the floating organic compound at low cost and with high efficiency. <P>SOLUTION: According to this method for decomposing floating organic compound, in which vacuum ultraviolet light with the center wavelength of 172 nm is irradiated to gas to be treated containing a floating organic compound in the presence of oxygen to decompose the floating organic compound, almost all of the gas to be treated is introduced into the irradiation range of vacuum ultraviolet light, and the floating organic compound is decomposed by active oxygen species generated by irradiation of vacuum ultraviolet light. This apparatus 1 for decomposing floating organic compound includes: a reaction vessel 3 provided with an introduction part 24 for introducing the gas to be treated containing the floating organic compound and a discharge part 41 for discharging the treated gas; and an irradiating means 3 for irradiating vacuum ultraviolet light with the center wavelength of 172 nm to the gas to be treated, wherein the reaction vessel 3 is formed to satisfy the conditions. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique for decomposing a floating organic compound.

In recent years, air pollution due to floating organic compounds such as volatile organic compounds (VOC), mist organic compounds, and particulate suspended solids (PM) has become a major problem.
Volatile organic compounds are a general term for organic chemicals that easily volatilize in the atmosphere at normal temperature and pressure, and are widely used in the industry as cleaning agents, solvents, fuels, and the like. However, when volatile organic compounds are released into the environment, it is known to cause pollution and health damage through the production of photochemical oxidants that cause photochemical smog, contamination of soil, groundwater and drinking water. In addition, it has been clarified that volatile organic compounds are the causative substances of sick house syndrome and sick building syndrome, and the causative substances of particulate suspended matter (PM) generation. As the relationship has gained social attention, emission regulations for volatile organic compounds, including volatile organic compounds, have been tightened, and the 2004 Air Pollution Control Act has led to major emission facilities. The regulations were strengthened.

Under such circumstances, in addition to suppressing the emission of floating organic compounds, a technique for decomposing or removing floating organic compounds released into the atmosphere, particularly volatile organic waste, has attracted attention. As for the decomposition or removal of volatile organic waste, there are a combustion method in which volatile organic waste is burned at a high temperature, a catalytic method in which volatile organic waste is oxidatively decomposed in the presence of a noble metal catalyst such as platinum or palladium. Are known.
However, most of the volatile organic waste discharged in Japan currently exists in the atmosphere at a relatively low concentration of 50 to 100 ppm. Treatment of gas containing volatile organic waste at a low concentration below the natural range by using a combustion method requires a large amount of fuel for auxiliary combustion, and therefore the treatment efficiency is low, and combustion at high temperatures As a result, there is a problem that NOx is by-produced.
On the other hand, the catalytic method has been put into practical use as a three-way catalyst for exhaust gas purification of gasoline engines. However, there are problems such as cost increase due to rising prices of precious metals and catalyst deterioration due to poisoning, etc., and lean combustion There is a major problem that it cannot be applied to the purification of exhaust gas from diesel engines used under conditions.

  As a technique for efficiently decomposing a volatile organic compound, for example, Patent Document 1 discloses a photocatalyst application surface in which a visible light photocatalyst is applied to at least a part of a ceiling and / or a wall surface in a house, and the photocatalyst application. A light source provided in the vicinity of the surface, a reflecting member that reflects light from the light source toward the photocatalyst application surface, and an exhaust port formed at least at one position of the photocatalyst application surface. And a house with an air purifying function is disclosed. However, the technique described in Patent Document 1 is not suitable for the decomposition treatment of a large amount of volatile organic compounds and particulate suspended solids (PM).

In Patent Document 2, in a volatile organic compound processing apparatus that decomposes a volatile organic compound concentrated on an adsorbent by discharge, it is necessary to increase the power capacity in order to decompose the entire amount of the adsorbed volatile organic compound in a short time. In order to solve this problem, the discharge control mechanism applies a voltage to each group of electrode pairs so that the electrode pairs are divided into a plurality of groups, and different adsorbent parts touch the discharge in turn. An applied volatile organic compound processing apparatus is disclosed.
However, since the volatile organic compound processing apparatus described in Patent Document 2 requires an adsorbent and a discharge control mechanism in addition to the electrode for decomposing the volatile organic compound, it is difficult to reduce the size and weight. . Further, nitrogen radicals generated by plasma discharge may react with oxygen to generate NOx and cyanide compounds.

Patent Document 3 discloses an apparatus for decomposing pollutants such as CO and hydrocarbons contained in a fluid using active oxygen species generated by light irradiation of a dielectric barrier discharge excimer lamp. However, in the apparatus, although the active oxygen species generated by light irradiation contribute to the decomposition of the pollutant, the pollutant cannot be sufficiently decomposed only by the active oxygen species, and the decomposition intermediate product remains. In Example 1 of the same document, it is described that it is necessary to combine light irradiation with a noble metal catalyst such as Pt, Pd, and Rh or a photocatalyst such as TiO ₂ . The combined use of a light irradiation decomposition apparatus and an expensive noble metal catalyst is more expensive and impedes practical use than conventional decomposition apparatuses using only catalysts.
In addition, a photocatalyst such as TiO ₂ operates with light in the ultraviolet region (wavelength range of 380 nm or less), but TiO ₂ has a quantum yield of about 1 to 2%, so light in the vacuum ultraviolet region (for example, wavelength 172 nm). ), The detailed study by the present inventors has revealed that there is almost no decomposition effect, and the use of an unnecessary photocatalyst is costly and the device is complicated, and the combined effect cannot be expected. . Therefore, the development of a low-cost and high-decomposition photo-irradiation decomposition apparatus that does not require a precious metal catalyst or photocatalyst is essential for practical use.

Non-Patent Document 1 discloses an apparatus for decomposing a floating organic compound using vacuum ultraviolet light, which is a kind of volatile organic compound such as benzene (C ₆ H ₆ ), nitrogen (N ₂ ), and It is described that benzene is decomposed by introducing a mixed gas composed of oxygen (O ₂ ) into a chamber as a reaction vessel and irradiating the chamber with a vacuum ultraviolet light Xe ₂ excimer lamp having a wavelength of 172 nm. Yes.

Here, the conventional floating organic compound decomposition | disassembly apparatus described in the nonpatent literature 1 is shown in FIG. In the conventional floating organic compound decomposition apparatus 100, a mixed gas composed of N ₂ and O ₂ introduced from one end side of a reaction vessel 101 that is a cylindrical chamber and C ₆ H ₆ that is VOC is a reaction vessel. The center wavelength (peak wavelength) from the Xe ₂ excimer lamp 102 provided on the other end face of 101 is irradiated to light having a wavelength of 172 nm and is emitted from the other end side. O ₂ irradiated with vacuum ultraviolet light generates active oxygen species (triplet oxygen atom, singlet oxygen atom, ozone, etc.), which oxidatively decomposes C ₆ H ₆ which is a volatile organic compound.

However, the floating organic compound decomposition apparatus 100 described in Non-Patent Document 1 is relatively simple and suitable for downsizing, but due to absorption of vacuum ultraviolet light by oxygen contained in the mixed gas, The irradiation range of the vacuum ultraviolet light irradiated from the excimer lamp 102 is limited to a very small area in the reaction vessel 101. Therefore, since the decomposition of the floating organic compound proceeds only in a very small area in the reaction vessel 101, there is a problem that the decomposition efficiency of the floating organic compound is low. Of the active oxygen species, ozone (O ₃ ) may exist outside the irradiation range due to diffusion, but particularly active triplet oxygen atoms are only present in the vacuum ultraviolet light irradiation range and very close to it at normal pressure. Therefore, the decomposition efficiency of the floating organic compound cannot be improved by means such as increasing the flow rate of the gas to be treated introduced into the reaction vessel 101.

JP 2007-242502 A JP 2006-175422 A JP 2007-501349 A

Takashi Kawahara and two others, "Study on the decomposition process of benzene with a 172 nmXe2 excimer lamp", Proceedings of the 51st Radiation Chemistry Conference, October 15, 2008, p (117) -p (118)

  An object of this invention is to provide the decomposition | disassembly method and apparatus of a floating organic compound which can decompose | disassemble a floating organic compound at low cost and high efficiency in view of said subject.

  The present invention provides active oxygen in the case of decomposing a volatile organic compound by irradiating a gas to be treated containing the volatile organic compound as a floating organic compound with vacuum ultraviolet light having a center wavelength of 172 nm in the presence of oxygen. Among the various species, the triplet oxygen atom mainly contributed to the decomposition of aromatic hydrocarbons, and the triplet oxygen atom and ozone mainly contributed to the decomposition of aldehydes. Is based.

  That is, the present invention relates to a method for decomposing a floating organic compound by irradiating a processing gas containing a floating organic compound with vacuum ultraviolet light having a center wavelength of 172 nm in the presence of oxygen. All are introduced into the irradiation range of the vacuum ultraviolet light, and the floating organic compound is decomposed by the active oxygen species generated by the irradiation of the vacuum ultraviolet light. .

In the present invention, the “floating organic compound” means an organic air pollutant such as a volatile organic compound, mist, or particulate suspended matter (PM).
Further, in the present invention, “in the presence of oxygen” means a state in which the gas to be treated contains oxygen, and means both a state in which oxygen is separately added and a state in which oxygen is originally contained as in the atmosphere. . In the present invention, “substantially all of the gas to be treated” means 80% or more, preferably 90% or more, more preferably 95% or more of the gas to be treated. In the present invention, the “irradiation range” refers to a range irradiated with vacuum ultraviolet light having an intensity of 1% or more of the intensity of incident light.

Further, in the present invention, the “gas to be treated” refers to an arbitrary gas containing a floating organic compound, which is a gas to be processed by the floating organic compound decomposition method and decomposition apparatus of the present invention. In the present invention, “active oxygen species” refers to triplet oxygen atoms (O ( ³ P)) and singlet oxygen atoms (O ( ¹ ) generated by the decomposition reaction (1) of O ₂ by irradiation with vacuum ultraviolet light. D)) and ozone formed by the triple reaction (2) of the triplet oxygen atom or a mixture thereof.
O ₂ + hν (172 nm) → O ( ³ P) + O ( ¹ D) (1)
_{^{O (3 P) + O 2}} + M (M = N 2 or _{O 2) → O 3 + M} (2)
O ₂ has a large absorption cross section of 4.6 × 10 ⁻¹⁹ cm ² molecule ^{−1 at} 172 nm, which is a value of 193 nm (3.2 × 10 ⁻²² cm ² molecule ⁻ of ArF excimer laser). ¹ ) about 1400 times. Therefore, extremely high concentration of active oxygen species can be generated in the irradiation region of 172 nm light by the reaction (1) and the subsequent (2).

  According to the configuration of the present invention, most of the gas to be treated is efficiently brought into contact with active oxygen species (especially triplet oxygen atoms and singlet oxygen atoms existing only in the vicinity of the irradiation range of vacuum ultraviolet light and the vicinity thereof). Therefore, the decomposition efficiency of the floating organic compound contained in the gas to be treated can be improved as compared with the conventional method. Further, since nitrogen does not have an absorption band in the wavelength region of 172 nm, nitrogen decomposition does not occur when vacuum ultraviolet light having a center wavelength of 172 nm is used. Therefore, generation of harmful NOx and cyanide compounds due to photoreaction can be suppressed.

As described above, the floating organic compound means an organic air pollutant such as a volatile organic compound, a mist, or a particulate suspended solid (PM). Among these, the present invention is a volatile organic compound. It is suitable for decomposition. In the decomposition method of the present invention, most volatile organic compounds can be decomposed and the type thereof is not limited, but specific examples are methane, ethane, propane, butane, ethylene, propylene, acetylene, Formaldehyde, acetaldehyde, acetone, acrolein, formic acid, acetic acid, butyric acid, methyl ethyl ketone, methanol, ethanol, isopropyl alcohol, butyl alcohol, benzene, toluene, xylene, phenol, styrene, ethyl acetate, butyl acetate, carbon monoxide, 2-methoxyethanol Examples include 2-ethoxyethanol, 2-butoxyethanol and the like.
In the present invention, all of the above-mentioned active oxygen species contribute to the decomposition of the floating organic compound, but the decomposition activity of the floating organic compound of the active oxygen species differs depending on the type of each pollutant gas, and is saturated with aliphatic saturation. In hydrocarbons, singlet oxygen contributes to decomposition, whereas in aliphatic unsaturated hydrocarbons and aldehydes, triplet oxygen and ozone, and in aromatic compounds, triplet oxygen greatly contributes to decomposition.

  In the decomposition method of the present invention, it is particularly preferable that the volatile organic compound is an aromatic hydrocarbon or an aldehyde. Aromatic hydrocarbons have a stable resonance structure and are difficult to decompose as compared to aliphatic hydrocarbons, and many are harmful to humans, such as benzene and toluene. Many aldehydes, such as formaldehyde, cause causative agents for sick house syndrome. Therefore, if aromatic hydrocarbons and aldehydes can be decomposed, it is a powerful and useful method for decomposing floating organic compounds.

In this case, it is preferable that the active oxygen species are mainly triplet oxygen atoms or ozone.
The triplet oxygen atom has high decomposition activity of aromatic hydrocarbons, but can exist only in the irradiation range of vacuum ultraviolet light and in the vicinity thereof. For this reason, in the decomposition method of the present invention, by introducing almost all of the gas to be treated into the irradiation range of vacuum ultraviolet light, the possible range of triplet oxygen atoms can be greatly expanded. Hydrogen decomposition efficiency can be greatly improved. On the other hand, since ozone has a long lifetime, it can exist in a wider range than triplet oxygen atoms by diffusion. Therefore, the decomposition efficiency of floating organic compounds, particularly aldehydes, can be greatly improved.

  The decomposition method of the present invention can be applied over a wide temperature range from room temperature to normal pressure or from a low temperature at which floating organic compounds do not liquefy to about 500 ° C., and the reaction pressure is also used under reduced pressure or pressurized conditions. However, there is no need for equipment such as a vacuum device, and it is possible to decompose floating organic compounds at low cost, and it is easy to reduce the size and weight of the apparatus used to decompose floating organic compounds. From the viewpoint of becoming, it is preferable that the floating organic compound is decomposed under normal temperature and pressure conditions.

The floating organic compound decomposing apparatus of the present invention includes a reaction vessel provided with an introduction part for introducing a gas to be treated containing a floating organic compound and a discharge part for discharging the treated gas, and a vacuum with a center wavelength of 172 nm. In the floating organic compound decomposing apparatus comprising irradiation means for irradiating the gas to be treated with ultraviolet light, the reaction vessel has an incident surface of the vacuum ultraviolet light irradiated from the irradiation means that transmits the vacuum ultraviolet light. It is characterized in that it is formed so that almost all of the gas to be processed contained therein is present within the irradiation range of the vacuum ultraviolet light.
Here, “a member that transmits vacuum ultraviolet light” means that vacuum ultraviolet light having an intensity necessary for decomposing a floating organic compound is introduced into the reaction container when used on the incident surface of the vacuum ultraviolet light in the reaction container. A member having a transmittance necessary for irradiation.

If the reaction vessel is configured as described above in the floating organic compound decomposing apparatus, most of the gas to be processed comes into contact with the active oxygen species, and therefore the decomposition efficiency of the floating organic compound contained in the gas to be processed Can be improved as compared with the conventional apparatus. In addition, by using an irradiation means having a central wavelength of 172 nm in which nitrogen does not have an absorption band, it is possible to suppress the photolysis of nitrogen and the accompanying generation of NOx and cyanide compounds.
In the apparatus of the present invention, a decomposition product (carbon, char) of a floating organic compound may adhere to a transparent window that transmits vacuum ultraviolet light to form an organic film. Even if it is formed, it is readily decomposed by the direct light irradiation and the light cleaning effect of the active oxygen species (self-cleaning function), so that it is possible to avoid damaging the light irradiation into the reaction vessel.

In this case, it is preferable that the reaction vessel is provided adjacent to the reaction vessel so that almost all of the irradiation surface of the irradiation means and the incident surface overlap each other.
Alternatively, the irradiation means may be disposed inside the reaction vessel and have a cylindrical shape that irradiates the vacuum ultraviolet light from a side surface.

  With such a configuration, most of the vacuum ultraviolet light irradiated from the irradiation means can be used for the decomposition of the floating organic compound, so that the energy efficiency in the floating organic compound decomposition apparatus can be improved.

  According to the present invention, since no metal catalyst or photocatalyst is used, the floating organic compound can be decomposed at low cost and with high efficiency, and can be easily reduced in size and weight, and applied to a wide range of applications and fields. A possible floating organic compound decomposition apparatus can be provided.

It is the schematic for demonstrating the floating organic compound decomposition | disassembly apparatus which concerns on embodiment of this invention. It is a figure which shows the processing apparatus of the floating organic compound decomposition | disassembly apparatus shown in FIG. 1, (A) is a bottom view of the state which removed the cover part, (B) is a figure which shows a cover part. 4 is a graph showing the relationship between the irradiation time of vacuum ultraviolet light and the concentrations of reactants and products in Example 1. It is a graph which shows the relationship between the irradiation time of the vacuum ultraviolet light in Example 1 and Comparative Example 1, and the residual rate of a reaction material. It is a graph which shows the relationship between the irradiation time of the vacuum ultraviolet light in Example 2 and Comparative Example 2, and the residual rate of a reaction material. It is a graph which shows the relationship between the irradiation time of the vacuum ultraviolet light in Example 2, and the density | concentration of a reaction material and a product. In Example 2, it is a graph which shows the influence which the flow rate of to-be-processed gas has on the residual rate of a reaction material. In Example 2, it is a graph which shows the influence which the oxygen concentration in to-be-processed gas has on the residual rate of a reaction material. It is a graph which shows the relationship between the irradiation time of the vacuum ultraviolet light in Example 3, and the density | concentration of a reaction material and a product. It is a graph which shows the relationship between the irradiation time of the vacuum ultraviolet light in Example 3 and Comparative Example 3, and the residual rate of a reaction material. It is a graph which shows the relationship between the irradiation time of a vacuum ultraviolet light, and the density | concentration of a reaction material and a product in Example 3 whose oxygen concentration is 20%. It is a graph which shows the relationship between the irradiation time of a vacuum ultraviolet light, and the density | concentration of a reaction material and a product in Example 3 whose oxygen concentration is 10%. It is a graph which shows the relationship between the irradiation time of a vacuum ultraviolet light, and the density | concentration of a reaction material and a product in Example 3 whose oxygen concentration is 5%. It is the schematic for demonstrating the conventional floating organic compound decomposition | disassembly apparatus.

A floating organic compound decomposition apparatus (hereinafter simply referred to as a decomposition apparatus) according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, an apparatus used for a volatile organic compound (VOC) decomposition experiment will be described as an example.
As shown in FIG. 1, the decomposition apparatus 1 includes a supply unit 2 that supplies a mixed gas that is a gas to be processed, a processing device 3 that processes the mixed gas, and an exhaust unit 4 that measures components of the decomposed gas. It has.

The supply unit 2 includes a first tank 21, a second tank 22, a third tank 23, an introduction pipe 24, flow meters 25 a to 25 c, a pressure gauge 26, a first valve 27, and a second valve 28. And.
Nitrogen (N ₂ ) gas is stored in the first tank 21. The second tank 22 stores oxygen (O ₂ ) gas. The third tank 23 stores VOC gas.

  One end of the introduction pipe 24 is connected to each of the first to third tanks 21 to 23, the other end is connected to the processing apparatus 3, and the gas stored in the first to third tanks 21 to 23 is processed into the processing apparatus. 3 is a collecting pipe that functions as an introduction unit that supplies the gas to 3. The flow meters 25a to 25c are arranged in the respective branch pipes of the introduction pipe 24, and measure the flow rates of nitrogen gas, oxygen gas, and VOC gas, respectively. The pressure gauge 26 is disposed in the main pipe 24 and measures the pressure of the mixed gas. The first valve 27 is a needle valve that is disposed in the main pipe of the introduction pipe 24 upstream from the pressure gauge 26 and adjusts the flow rate of the mixed gas. The second valve 28 is a stop valve that is disposed in the main pipe of the introduction pipe 24 located below the processing apparatus 3 and stops or supplies the mixed gas.

  In the decomposition apparatus 1 used for decomposing the volatile organic compound contained in the gas to be processed, the first to third tanks 21, 22, and 23 may be omitted, and a pump for introducing the gas to be processed may be provided. Good. Even in this case, the first and second tanks 21 and 22 may be provided together with a pump for introducing the gas to be processed in order to adjust the nitrogen concentration and the oxygen concentration in the gas to be processed.

  The processing device 3 includes an irradiation unit 31 and a reaction vessel 32. The irradiation unit 31 includes a casing 311, an excimer lamp 312 that is an example of irradiation means, a sealed container 313, and a nitrogen introduction tube 314. The casing 311 is a box-shaped container formed by a support plate 311a that is a bottom plate for mounting the sealed container 313 that supports the excimer lamp 312 and a box portion 311b that opens around the excimer lamp 312 and the sealed container 313. It is. The box 311b is provided with a circular opening for allowing the irradiation light of the excimer lamp 312 to pass therethrough.

  The excimer lamp 312 is formed in an elongated cylindrical shape called a side-on type, and functions as an illuminating means by emitting light on the entire outer peripheral side surface. The excimer lamp 312 is disposed adjacent to the reaction vessel 32. In the excimer lamp 312 used in the decomposition apparatus 1, since Xe gas is sealed in a cylindrical glass tube, vacuum ultraviolet light having a center wavelength of 172 nm is emitted.

The sealed container 313 is a box-shaped container whose bottom surface is opened in accordance with the opening surface of the support plate 311 a of the casing 311. The sealed container 313 is supported in a state where both end portions of the excimer lamp 312 are inserted, and a nitrogen introduction tube 314 for filling the internal space with nitrogen N ₂ is connected to one end side. The hermetic container 313 is provided with the reaction container 32 in the opening, so that the internal space becomes a closed space and airtightness is ensured.
The nitrogen introduction pipe 314 is a pipe for introducing nitrogen gas into the internal space of the sealed container 313. By filling the sealed container 313 with nitrogen (N ₂ ) gas supplied from the nitrogen introduction pipe 314, the irradiation light from the excimer lamp 312 can reach the reaction container 32 without being attenuated.

  As shown in FIGS. 1 and 2, the reaction vessel 32 is a window that is an incident surface that overlaps substantially the entire opening that is the irradiation surface of the excimer lamp 312 by the window portion 321, the container body 322, and the lid portion 323. It has a portion 321 and is provided adjacent to the excimer lamp 312. The window portion 321 is provided with quartz glass, which is a member that transmits vacuum ultraviolet light, in a circular opening, and functions as an incident surface for irradiation light from the excimer lamp 312. The container main body 322 has a cylindrical processing space S in which a decomposition process is performed by supplying a gas to be processed. The lid 323 is a disc-like body in which the introduction tube 24 is connected to a position on one end side of the excimer lamp 312 and an exhaust pipe to be described later is connected to a position on the other end side of the excimer lamp 312. The lid portion 323 is provided with a screw hole in the entire peripheral portion, and is fixed to the container body 322 by a bolt 323a.

  The inner diameter and height of the container main body 322 that forms the processing space S together with the window portion 321 and the lid portion 323 are appropriately adjusted so that almost all of the gas to be processed introduced into the processing space S exists in the irradiation range of the excimer lamp 312. Is done. The inner diameter of the container main body 322 may be approximately equal to the diameter of the opening of the box portion 311b, and the height is such that the intensity of the vacuum ultraviolet light reaching the lid portion 323 side in a state where the gas to be processed is filled. What is necessary is just to set so that it may become a predetermined ratio with respect to the vacuum ultraviolet light which injects from the window part 321 side. The intensity of the vacuum ultraviolet light reaching the lid portion 323 mainly depends on the concentration of oxygen gas that absorbs vacuum ultraviolet light in the gas to be processed. For example, the experimental value or literature value of the oxygen extinction coefficient is Lambert. It can be calculated by applying to the Beer rule. For example, in order for the intensity of the vacuum ultraviolet light reaching the lid 323 side to be about 1% of the intensity of the incident light, the height of the container body 322 is set so that the oxygen concentration in the gas to be processed is 1. % Is 20 to 25 cm, and 20% is 1 to 2 cm.

The exhaust unit 4 includes an exhaust pipe 41, a Fourier transform infrared spectrophotometer (FT-IR) 42 used for component analysis, a quadrupole mass spectrometer 43 used for measuring oxygen concentration, and a pressure gauge. 44, a first exhaust pump 45, a second exhaust pump 46, and a third exhaust pump 47. A booster pump 45a, which is an auxiliary pump, is provided in the front stage of the first exhaust pump 45, and an ozone absorber 45b that traps ozone in the exhaust gas is further provided in the front stage.
The exhaust pipe 41 has one end of the main pipe connected to the lid portion 323, the other end serving as a branch pipe, one connected to the Fourier transform infrared spectrophotometer 42, and the other connected to the quadrupole mass spectrometer 43. This is a pipe functioning as a discharge part for discharging the processed gas. The main pipe of the exhaust pipe 41 is provided with a third valve 48 serving as a stop valve for stopping or flowing the exhaust of the mixed gas at a position below the processing apparatus 3. Further, the branch pipe of the exhaust pipe 41 is a needle valve for adjusting the inflow amount of the mixed gas upstream of the Fourier transform infrared spectrophotometer 42 and the quadrupole mass spectrometer 43. A four valve 49 and a fifth valve 50 are provided.
The pressure gauge 44 measures the pressure of the mixed gas sucked by the first exhaust pump 45 that is a rotary pump. A sixth valve 51 is provided in the pipe between the pressure gauge 44 and the first exhaust pump 45.
The second exhaust pump 46 is a turbo pump, and the third exhaust pump 47 is a rotary pump. The second exhaust pump 46 and the third exhaust pump 47 are operated when the oxygen concentration is measured by the quadrupole mass spectrometer 43, and the rest are used in a stopped state. Sixth to eighth valves 51 to 53, which are needle valves, are provided in the respective pipes to the first to third exhaust pumps 45 to 47.
The fourth valve 49 and the fifth valve 50 that are needle valves are closed, and the eighth valve 54 and the ninth valve 55 that are needle valves are opened, so that the Fourier transform infrared spectrophotometer 42 and the quadrupole mass analysis are performed. It is also possible to exhaust directly without going through the device 43.

  Next, examples and comparative examples performed for confirming the effects of the present invention will be described. First, the apparatus and experimental operation used in Comparative Examples 1, 2, and 3 and Examples 1, 2, 3, and 4 will be described, and then each experimental result will be described. Unless otherwise specified, these comparative examples and examples are all experimental results under normal temperature and pressure.

Comparative Example 1
For comparison with the decomposition performance of the decomposition apparatus 1 according to the embodiment of the present invention, the decomposition performance of the conventional decomposition apparatus 100 shown in FIG. 14 was also examined. In FIG. 14, the same components as those of the decomposition apparatus 1 shown in FIG.
In the conventional decomposition apparatus 100, the reaction vessel 101 is formed in a cylindrical shape having a diameter of about 3.2 cm and a length of 23 cm. An excimer lamp (input power 20 W, light intensity 50 mW / cm ² , irradiation window area 8 cm ² , number of photons 3.44 × 10 ¹⁷ / s) 102 is referred to as a head-on type, and an upper surface formed in a cylindrical shape or It functions as an illuminating means by emitting light from one end surface side that becomes the bottom surface. Since the excimer lamp 102 is arranged on one end surface of the reaction vessel 101, the irradiation light is emitted toward the axial direction of the reaction vessel 101, so that the irradiation area becomes a circular cross-sectional area of the reaction vessel 101.

A mixed gas composed of nitrogen, oxygen and benzene (oxygen concentration 20%, benzene concentration 1000 ppm) is introduced into the reaction vessel 101 of the conventional decomposition apparatus 100 thus configured, and the excimer lamp 102 is turned on. Then, a decomposition experiment was performed by irradiating the reactor 101. The experiment was performed with the second valve 28 and the third valve 48 closed to make the reactor 101 a closed system. The fourth valve 49 and the sixth valve 51 are opened at every elapse of a predetermined time, the first exhaust pump 45 is operated, and the exhaust pipe 41 and the Fourier transform infrared spectrophotometer 42 are once brought into a vacuum state. The sixth valve 51 is closed, the third valve 48 is opened, and a part of the contents of the reaction vessel is introduced into the Fourier transform infrared spectrophotometer 42. The concentration of the reaction product benzene and the reaction product (ozone O ₃ , carbon monoxide CO, carbon dioxide CO ₂ , formic acid HCOOH) was determined in advance using a calibration curve (samples with known concentrations were used, and the concentration and component specific The relationship with the absorbance of the absorption band is plotted).

Example 1
A decomposition experiment was performed using the decomposition apparatus 1 according to the present embodiment. In this embodiment, a container body 322 having a processing space S with a diameter of 100 mm and a thickness of 30 mm is used. As for the excimer lamp 312, the input power 20W, light intensity 10 mW / cm ^2, irradiation window area 78.5 cm ^2, was used for photon number 6.83 × 10 ¹⁷ cells / s. Then, by adjusting the first valve 27 and the second valve 28 of the supply unit 2, a mixed gas having an oxygen O ₂ concentration of 20% and a benzene C ₆ H ₆ concentration of 1000 ppm is supplied to the reaction vessel 32, and the excimer The lamp 312 was turned on to irradiate the processing space S. At this time, in order to set the processing space S as a closed system, the first to third exhaust pumps 45 to 47 were not operated, and the third valve 48 was closed. As in the case of Comparative Example 1, the fourth valve 49 and the sixth valve 51 are opened every predetermined time, the first exhaust pump 45 is operated, and the exhaust pipe 41 and the Fourier transform infrared spectrophotometer 42 are once connected. Apply vacuum. The sixth valve 51 is closed, the third valve 48 is opened, and a part of the contents of the reaction vessel is introduced into the Fourier transform infrared spectrophotometer 42. The concentrations of the reactant benzene and the reaction products (ozone O ₃ , carbon monoxide CO, carbon dioxide CO ₂ , formic acid HCOOH) were determined using a calibration curve prepared in advance.

Comparative Example 2 and Example 2
The apparatus 100 used in Comparative Example 1 and the apparatus 1 used in Example 1 were used, respectively, and a mixed gas (oxygen concentration 5 to 20%, benzene concentration 200 or 1000 ppm) was supplied at a predetermined flow rate (250 to 1000 mL / min). The experiment was carried out in a flow system flowing in the reaction vessels 101 and 3. Irradiation with the excimer lamps 102 and 312 started when 1 minute passed after the flow started, and ended after 15 minutes passed.

Experimental Results (1) Changes with Time of Reactant and Product Concentrations in Example 1 As shown in the graph of FIG. 3, it can be seen that benzene C ₆ H ₆ was decomposed about 1.5 minutes after the start of irradiation. As the concentration of benzene decreases, the concentration of carbon monoxide CO, carbon dioxide CO ₂ and formic acid HCOOH increases. Among these, the concentration of carbon monoxide and formic acid reached a maximum at 1.5 minutes after the start of irradiation, and thereafter the concentration decreased and disappeared completely 3 to 4 minutes after the start of irradiation. It can be seen that the concentration of carbon dioxide increases monotonously with the start of irradiation and reaches a steady state 4 to 5 minutes after the start of irradiation. From these results, carbon monoxide, formic acid, and carbon dioxide are produced as the initial decomposition products of benzene, and it is considered that all two of them are further oxidized and eventually converted to carbon dioxide. .
Also, it can be seen that the ozone O ₃ concentration increases almost linearly with the start of irradiation, and becomes a substantially constant value about 1 minute after the start of irradiation.

  The changes over time in the reactant and product concentrations described above are significantly different from those in the case where ozone is introduced into the reaction vessel without irradiation with vacuum ultraviolet light. Is not considered large. In addition, even when experiments were conducted under conditions that reduced collision relaxation of singlet oxygen atoms due to collisions with nitrogen atoms, there was no significant change in the residual ratio of benzene. It is thought that the contribution of oxygen atoms is not significant. The above results suggest that the triplet oxygen atom is the main active species for benzene decomposition.

(2) Comparison of energy efficiency of decomposition reaction in Example 1 and Comparative Example 1 The relationship between the irradiation time of vacuum ultraviolet light and the residual ratio of reactants in Example 1 and Comparative Example 1 is as shown in FIG. . The test was performed using a mixed gas composed of 20% oxygen O ₂ and 80% nitrogen N ₂ and benzene C ₆ H ₆ having a concentration of 200 ppm. In Example 1, the decomposition rate of benzene was much higher, and benzene was completely decomposed within 2 minutes (90 seconds) after the start of irradiation, whereas in Comparative Example 1, 20 minutes after the start of irradiation. Even after the lapse, about 5% of benzene remained.

Based on these results, the amount of energy E _EO required to decompose the unit amount of benzene was determined using the following formula.
E _EO = (1000 × P × t) / (V × log (C ₀ / C))
In the formula, P is the irradiation intensity [W], t is the elapsed time [h], V is the volume [L] of the reaction vessel, C ₀ is the initial concentration of benzene [ppm], and C is the concentration of benzene at the elapse of time t. [Ppm].
The values of E _EO (unit: W · h / order) obtained for Example 1 and Comparative Example 1 were 2.876 and 25.65, respectively. From these results, it can be seen that the decomposition apparatus 1 according to the embodiment of the present invention has about 8.9 times the energy efficiency of the decomposition apparatus 100 according to the conventional embodiment.

(3) Comparison of decomposition performance in Example 2 and Comparative Example 2 Next, a comparative experiment was performed between the decomposition apparatus 1 and the conventional decomposition apparatus 100. In the comparative experiment, a gas obtained by mixing 20% oxygen O ₂ and 80% nitrogen N ₂ and benzene C ₆ H ₆ having a concentration of 200 ppm was caused to flow into the reaction vessel 3 or the reaction vessel 101 at a flow rate of 1000 mL / min. The flow system was used to measure the residual concentration.
As shown in FIG. 5, after the excimer lamps 312 and 102 began to be turned on, the residual concentration of benzene C ₆ H ₆ immediately decreased in both apparatuses. However, it was about 90% in the conventional decomposition apparatus 100, but about 50% in the decomposition apparatus 1, and the decomposition apparatus 1 showed higher decomposition performance.

(4) Relationship between vacuum ultraviolet light irradiation time and product concentration in Example 2 The results are as shown in FIG. All the products (ozone, carbon monoxide, carbon dioxide and formic acid) became a constant value in about 1 minute after light irradiation, and returned to the state before light irradiation in 2 minutes after the end of irradiation.

(5) Influence of the flow rate of the gas to be treated on the residual rate of the reactant in Example 2 Next, the flow rate of the mixed gas (oxygen O ₂ 20%, nitrogen N ₂ 80%, benzene C ₆ H ₆ 200ppm) The residual concentration was measured at 500 mL / min and 250 mL / min in addition to 1000 mL / min.
As shown in FIG. 7, the mixed gas flow rate was about 50% at 1000 mL / min, but about 75% at 500 mL / min and 100% at 250 mL / min. Thus, it turns out that decomposition | disassembly performance can be improved by slowing down the speed | rate which passes mixed gas to the reaction container 3. FIG. In the case where the flow rate was 250 mL / min, it was confirmed that the ratio of carbon dioxide in the product was increased reflecting the improvement of the decomposition rate. This suggests that the decomposition performance can be improved by increasing the residence time of the gas to be treated in the reaction vessel and securing the irradiation time to some extent.

(6) Effect of oxygen concentration in gas to be treated on residual rate of reactant in Example 2 Next, the oxygen concentration of the mixed gas (flow rate 1000 mL / min, benzene C ₆ H ₆ 200 ppm) was set to 20%, and the remainder In addition to nitrogen N _2, the residual concentration of benzene C ₆ H ₆ was measured at 10% and 5%.
As shown in FIG. 8, the residual concentration of benzene was 50% when the oxygen concentration was 20%, but the residual concentration was improved to 30% to 35% when the oxygen concentration was 5%. Thus, it can be seen that the decomposition performance is high when the oxygen concentration of the gas mixture is low.
In addition to the oxygen concentration, other factors such as the flow rate of the gas to be treated may have an influence on the decomposition efficiency of benzene. For example, the vacuum ultraviolet light due to oxygen in the gas to be treated It is conceivable that the decrease in the vacuum ultraviolet light intensity inside the processing space due to the absorption contributes to the decrease in the decomposition efficiency accompanying the increase in the oxygen concentration.

Example 3
A decomposition experiment using the decomposition apparatus 1 according to the present embodiment was performed on acrolein, which is a representative aldehyde compound, instead of the benzene of Examples 1 and 2. In this embodiment, a container body 322 having a processing space S with a diameter of 100 mm and a thickness of 30 mm is used. As for the excimer lamp 312, the input power 20W, light intensity 10 mW / cm ^2, irradiation window area 78.5 cm ^2, was used for photon number 6.83 × 10 ¹⁷ cells / s. Then, by adjusting the first valve 27 and the second valve 28 of the supply unit 2, a mixed gas having an oxygen O ₂ concentration of 20% and an acrolein concentration of 500 ppm is supplied to the reaction vessel 32, and the excimer lamp 312 is turned on. Then, the treatment space S was irradiated. At this time, in order to set the processing space S as a closed system, the first to third exhaust pumps 45 to 47 were not operated, and the third valve 48 was closed. As in the case of Comparative Example 1, the fourth valve 49 and the sixth valve 51 are opened every predetermined time, the first exhaust pump 45 is operated, and the exhaust pipe 41 and the Fourier transform infrared spectrophotometer 42 are once connected. Apply vacuum. The sixth valve 51 is closed, the third valve 48 is opened, and a part of the contents of the reaction vessel is introduced into the Fourier transform infrared spectrophotometer 42. The concentrations of acrolein as a reactant and reaction products (ozone O ₃ , carbon monoxide CO, carbon dioxide CO ₂ , formaldehyde HCHO, formic acid HCOOH) were determined using a calibration curve prepared in advance.

Example 4
The apparatus 1 used in Example 1 was used, and an experiment was conducted in a flow system in which a mixed gas (oxygen concentration 5 to 20%, acrolein concentration 500 ppm) was flowed to the reaction vessels 101 and 3 at a predetermined flow rate (1000 mL / min). . Irradiation with the excimer lamps 101 and 312 started when 1 minute passed after the flow started and ended after 15 minutes passed.

Comparative Example 3
For comparison with the decomposition performance of the decomposition apparatus 1 according to the embodiment of the present invention for acrolein, the decomposition performance of the conventional decomposition apparatus 100 shown in FIG. 14 was also examined.

Experimental Results (1) Changes in Reactant and Product Concentrations with Time in Example 3 As shown in the graph of FIG. 9, it can be seen that acrolein (C ₂ H ₃ CHO) was decomposed at about 30 seconds from the start of measurement. . As the acrolein concentration decreases, the concentration of carbon dioxide CO ₂ increases. In addition, carbon monoxide CO and formic acid HCOOH decreased after generation, and formic acid completely disappeared 60 seconds after the start of irradiation. It can be seen that the concentration of carbon dioxide increases monotonously with the start of irradiation and gradually increases after 120 seconds from the start of irradiation. From these results, carbon monoxide, formic acid, and carbon dioxide are generated as the initial degradation products of acrolein, and it is considered that all of them are further oxidized and finally converted to carbon dioxide. .
It can also be seen that the ozone O ₃ concentration increases almost linearly with the start of irradiation and reaches a maximum at about 180 seconds after the start of irradiation.

  In order to investigate the contribution of ozone, a decomposition experiment was conducted in which about 6000 ppm of ozone was introduced into the reaction vessel without performing irradiation with vacuum ultraviolet light. As a result, the decomposition rate of acrolein by ozone was close to that under the irradiation of vacuum ultraviolet light in which all the active oxygen species existed, and it was confirmed that ozone was one of the main active species for acrolein decomposition.

(2) Comparison of energy efficiency of decomposition reaction in Example 3 and Comparative Example 3 The relationship between the irradiation time of vacuum ultraviolet light and the residual ratio of the reactants in Example 3 and Comparative Example 3 is as shown in FIG. . Note that a mixed gas composed of 20% oxygen O ₂ and 80% nitrogen N ₂ and acrolein (C ₂ H ₃ CHO) having a concentration of 500 ppm was used. In Example 1, the decomposition rate of acrolein was much higher, and acrolein was completely decomposed within 30 seconds after the start of irradiation, whereas in Comparative Example 3, after the start of irradiation until it was completely decomposed. It took 270 seconds. Therefore, it was confirmed that the decomposition speed of the acrolein was 9 times or more faster in the decomposition apparatus 1 than in the conventional decomposition apparatus 100.

(3) Relationship between irradiation time of vacuum ultraviolet light and product concentration in Example 3 Next, acrolein (C ₂ H ₃ CHO) having a concentration of 130 ppm with oxygen O ₂ of 20% and nitrogen N ₂ of 80%. ) Was flowed into the reaction vessel 3 at a flow rate of 1000 mL / min, and the flow system was used to measure the residual concentration. The results are as shown in FIG. Acrolein (C ₂ H ₃ CHO) is completely decomposed in about 1 to 2 minutes after light irradiation after starting the excimer lamp 312 and all products (ozone, carbon monoxide, carbon dioxide and formic acid) The concentration was almost constant, and returned to the state before the light irradiation 2 minutes after the end of irradiation.

(4) Effect of oxygen concentration in gas to be treated in Example 3 on residual rate of reactant Next, the oxygen concentration of the mixed gas (flow rate 1000 mL / min, acrolein (C ₂ H ₃ CHO) 120 or 110 ppm) is determined. The residual concentration of acrolein (C ₂ H ₃ CHO) at 10% and 5% was measured in addition to 20% and nitrogen N ₂ as the remainder. The results are shown in FIGS. Similar to the experimental results at an oxygen concentration of 20%, acrolein was completely decomposed in about 1 to 2 minutes after the start of irradiation.

Example 5
Decomposition experiments were conducted using the decomposition apparatus 1 in the region of 100-1000 ppm of VOCs such as methane, ethylene, formaldehyde, acetaldehyde, toluene, ortho-xylene, meta-xylene, para-xylene and the like under normal temperature and normal pressure. It was confirmed that it could be decomposed. All of these VOCs are eventually decomposed into CO ₂ and H ₂ O, but compounds shown in Table 1 as intermediates were observed from FT-IR analysis. Table 1 shows the results obtained by performing the decomposition experiment using only ozone and the low pressure experiment result in which the contribution of singlet oxygen is high for the main active oxygen species contributing to the decomposition of each substance. In addition, ◎ is a main active species, ○ is an active species that is slower in decomposition rate than ◎ but contributes to decomposition, and × represents an active species that does not contribute to decomposition.
In the case of methane, only singlet oxygen contributes to decomposition, so the following deactivation reaction (3) of singlet oxygen is suppressed by lowering the pressure to 10 kPa, and the decomposition rate is reduced to about normal pressure after 5 minutes of irradiation. It is possible to increase to 100%, which is twice as much as 50%.
_{^{O (1 D) + N 2}} → O (3 P) + O (3 P) (3)
On the other hand, triplet oxygen and ozone are particularly effective for the decomposition of aliphatic unsaturated hydrocarbons and aldehydes, and triplet oxygen is particularly effective for aromatic compounds. Therefore, in order to increase the decomposition rate, it is necessary to set the oxygen concentration and the total pressure so that the effective species concentration is high depending on the target VOC.

In the present embodiment, as shown in FIG. 1, the excimer lamp 312 that is an irradiation means is disposed adjacent to the reaction vessel 32, but the irradiation means having a cylindrical shape that irradiates vacuum ultraviolet light from the side surface. You may arrange | position inside a cylindrical reaction container. With such a configuration, not only the same effect as the decomposition apparatus 1 shown in FIG. 1 can be obtained, but also the vacuum ultraviolet light from the irradiation means can be directly irradiated to the gas mixture to be processed. A sealed container for filling nitrogen N ₂ between the irradiation means and the reaction container can be omitted. Further, since the reaction container does not necessarily require light transmission, it can be installed not only indoors but also in a vehicle or a ship by forming it with a material having high corrosion resistance, heat resistance, and weather resistance.

DESCRIPTION OF SYMBOLS 1 Floating organic compound decomposition | disassembly apparatus 2 Supply part 21 1st tank 22 2nd tank 23 3rd tank 24 Introductory pipe 25a-25c Flow meter 26 Pressure gauge 27 1st valve 28 2nd valve 3 Processing apparatus 31 Irradiation part 311 Casing 311a Support plate 311b Box portion 312 Excimer lamp 313 Sealed vessel 314 Nitrogen inlet tube 32 Reaction vessel 321 Window portion 322 Container body 323 Lid portion 323a Bolt 4 Exhaust portion 41 Exhaust tube 42 Fourier transform infrared spectrophotometer (FT-IR)
43 quadrupole mass spectrometer 44 pressure gauge 45 first exhaust pump 45a booster pump 45b ozone absorber 46 second exhaust pump 47 third exhaust pump 48-55 3-10 valve S processing space

Claims (9)

In a method for decomposing a floating organic compound by irradiating a gas to be treated containing a floating organic compound with vacuum ultraviolet light having a center wavelength of 172 nm in the presence of oxygen,
A floating organic compound, wherein substantially all of the gas to be treated is introduced into the irradiation range of the vacuum ultraviolet light, and the floating organic compound is decomposed by active oxygen species generated by the irradiation of the vacuum ultraviolet light. Disassembly method.   2. The method for decomposing a floating organic compound according to claim 1, wherein the floating organic compound is a volatile organic compound.   The method for decomposing a floating organic compound according to claim 2, wherein the floating organic compound is an aromatic hydrocarbon.   The method for decomposing a floating organic compound according to any one of claims 1 to 3, wherein the active oxygen species are mainly triplet oxygen atoms.   The method for decomposing a floating organic compound according to claim 2, wherein the floating organic compound is an aldehyde.   6. The method for decomposing a floating organic compound according to claim 5, wherein the active oxygen species are mainly triplet oxygen atoms and ozone.   The method for decomposing a floating organic compound according to any one of claims 1 to 6, wherein the decomposition of the floating organic compound is performed under conditions of normal temperature and pressure. A reaction vessel provided with an introduction part for introducing a gas to be treated containing a floating organic compound and a discharge part for discharging a gas after treatment, and irradiation for irradiating the gas to be treated with vacuum ultraviolet light having a center wavelength of 172 nm A floating organic compound decomposition apparatus comprising:
The reaction vessel is made of a member through which the incident surface of the vacuum ultraviolet light irradiated from the irradiation means transmits the vacuum ultraviolet light, and almost all of the gas to be processed contained therein is the vacuum ultraviolet light. It is formed so that it may exist in the irradiation range of the floating organic compound decomposition | disassembly apparatus characterized by the above-mentioned.   9. The floating organic compound decomposition according to claim 8, wherein the reaction vessel is provided adjacent to the reaction vessel so that substantially all of the irradiation surface of the irradiation means and the incident surface overlap each other. apparatus.

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