JP5092681B2 - Ozone decomposition removal catalyst and ozonolysis removal method using the same - Google Patents

Description

  The present invention relates to an ozonolysis removal catalyst, and more particularly to an ozonolysis removal catalyst made of crystalline iron oxide. The present invention also relates to an ozonolysis removal method using the ozonolysis removal catalyst.

  In recent years, the maximum hourly value of photochemical oxidant concentration tends to increase year by year. Especially in urban areas such as Tokyo and Nagoya, the photochemical oxidant concentration satisfies the environmental standard value (one hour value is 0.06 ppm or less). Not.

  The photochemical oxidant is a pollutant having a strong oxidizing power mainly composed of ozone produced by a reaction between nitrogen oxides and hydrocarbons discharged from a factory or automobile under the irradiation of ultraviolet rays of the sun. Ozone not only causes oxidative degradation of substances but also has an adverse effect on the human body, and various ozone decomposition methods such as a thermal decomposition method, an activated carbon method, and a catalyst method have been proposed.

Examples of the ozone decomposition catalyst used in the catalyst method include MnO ₂ , Co ₃ O ₄ , NiO, Fe ₂ O ₃ , Ag ₂ O, Cr ₂ O ₃ , CeO ₂ , V ₂ O ₅ , CuO, and MoO _3. Among these, MnO ₂ is known to exhibit the highest activity (Applied Catalysis B, Environmental, 11 (1997), 129-166 (Non-patent Document 1)). Moreover, it is known that α-MnO _{2 in the} form of cryptomelane is preferable as a catalyst in a reaction for generating oxygen from ozone (Japanese Patent Publication No. 2003-527951 (Patent Document 1)).
Special table 2003-527951 gazette Applied Catalysis B, Environmental, 11 (1997), 129-166.

The present invention has been made in view of the above-described problems of the prior art, and is a new ozonolysis removal capable of efficiently decomposing ozone in place of a conventional catalyst for ozonolysis removal such as MnO ₂ . An object is to provide a catalyst.

  As a result of intensive studies to achieve the above object, the inventors of the present invention are excellent in the ability to decompose and remove ozone, which is made of crystalline iron oxide and has a pore having a central pore diameter of 1 to 20 nm. As a result, the present invention has been completed.

That is, the ozone decomposing catalyst for removing of the present invention has spherical particles of _γ-Fe 2 _{O 3} crystalline is aggregated, the mean pore diameter have a pore of 1 to 20 nm, BET ratio The surface area is 50 m ² / g or more .

The pores are preferably secondary pores .

  The ozonolysis and removal method of the present invention is characterized in that the ozone is decomposed and removed by bringing a gas containing ozone into contact with the ozonolysis and removal catalyst of the present invention.

  The reason why the catalyst for decomposing and removing ozonolysis of the present invention exhibits excellent ozone decomposing and removing performance is not necessarily clear, but the present inventors speculate as follows. That is, since the catalyst for ozonolysis removal of the present invention has a porous structure having pores with a central pore diameter of 1 to 20 nm, ozone molecules are quickly diffused into the pores without being limited to the pore structure, Further, it is assumed that ozone molecules diffused inside the pores are decomposed by the catalytic action of crystalline iron oxide. As a result, it is speculated that the ozone decomposition performance of the catalyst is enhanced because the ozone decomposition reaction occurs not only at the active sites on the outer surface of the catalyst but also at the active sites inside the pores.

According to the present invention, in place of the ozone decomposing catalyst for removing such conventional MnO _2, it is possible to provide a safe and efficient ozone decomposing removing catalyst capable of decomposing ozone to people or the environment .

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

  First, the ozonolysis removal catalyst of the present invention will be described. The catalyst for removing ozonolysis of the present invention is made of crystalline iron oxide and has pores having a central pore diameter of 1 to 20 nm. Since the iron oxide forming this ozonolysis removal catalyst is crystalline, the ozonolysis removal catalyst is excellent in ozonolysis performance and occlusion in a low temperature range from room temperature to about 100 ° C. The crystallinity of iron oxide can be confirmed by X-ray diffraction.

  The central pore diameter of the catalyst for removing ozonolysis of the present invention is 1 to 20 nm. When the central pore diameter is in the above range, ozone molecules diffuse in the pores, and the ozone decomposition reaction proceeds even at active sites inside the pores, thereby improving the ozone decomposition performance. On the other hand, when the central pore diameter is less than the above lower limit, ozone molecules are not diffused at a sufficient rate inside the pores, and high ozonolysis performance is not exhibited. On the other hand, when the above upper limit is exceeded, the specific surface area decreases, the catalytic activity decreases, and high ozonolysis performance is not exhibited. From such a viewpoint, the diameter of the central pore is preferably 2 to 10 nm, and more preferably 4 to 10 nm.

  The central pore diameter is a value (d (Vp) / d (Rp)) obtained by differentiating the pore volume (Vp) by the pore radius (Rp) and plotted against the pore radius (Rp). This is a value obtained by doubling the pore radius at the maximum peak of the curve (pore diameter distribution curve). The pore size distribution curve can be obtained by the method described below. That is, the catalyst for ozonolysis removal is cooled to liquid nitrogen temperature (−196 ° C.), nitrogen gas is introduced, the adsorption amount is determined by a constant volume method or a gravimetric method, and then the pressure of the introduced nitrogen gas is gradually increased. Increase and plot the amount of nitrogen gas adsorbed against each equilibrium pressure to obtain an adsorption isotherm. Using this adsorption isotherm, a pore size distribution curve can be obtained by a calculation method such as Cranston-Inklay method, Pollimore-Heal method, or BJH method.

Moreover, there is no restriction | limiting in particular about the specific surface area of the catalyst for ozonolysis removal of this invention, However, It is preferable that it is 50 m < ² > / g or more. The specific surface area can be calculated as a BET specific surface area from the adsorption isotherm using the BET isotherm adsorption equation.

  The pores of the catalyst for removing ozonolysis of the present invention are preferably secondary pores. The secondary pores can be formed, for example, by agglomerating the spherical particles of crystalline iron oxide. When the pores are secondary pores, the pore diameter, specific surface area, and pore volume can be increased, the diffusion resistance when ozone molecules diffuse in the pores is very small, It quickly diffuses into the pores. As a result, more ozone decomposition reaction occurs inside the pores, and the ozone decomposition performance is improved.

  The structure of the catalyst for removing ozonolysis of the present invention is not particularly limited, but it is preferable that the spherical particles of crystalline iron oxide are aggregated. If the ozonolysis removal catalyst is formed by agglomeration of spherical particles of crystalline iron oxide, the pore structure becomes a three-dimensional pore structure, so that more pores are formed and the specific surface area is increased. The catalytic activity is increased and the ozonolysis performance is improved. From this point of view, the pores of the ozonolysis removal catalyst are more preferably formed not only on the surface of the catalyst but also on the inside.

  The catalyst for removing ozonolysis of the present invention has one or more peaks at a diffraction angle corresponding to a d value of 1 nm or more in an X-ray diffraction pattern in a low angle region of 2θ = 10 ° or less. Is preferred. The X-ray diffraction peak means that there is a periodic structure having a d value corresponding to the peak angle in the sample. Therefore, having one or more peaks at a diffraction angle corresponding to a d value of 1 nm or more means that the pores are arranged at intervals of 1 nm or more.

  Specific examples of the structure in which the pores are regularly arranged include those in which the pores are connected to each other to form a three-dimensional channel having a 3D-Cubic Im3m structure. Here, “3D-Cubic Im3m” is determined based on the space group notation and represents the symmetry of the pore structure. Such a three-dimensional channel having a 3D-Cubic Im3m structure can be confirmed by measuring an X-ray diffraction pattern by an X-ray diffraction analysis method, and (110) and (200) in the region of 2θ = 0.5 to 3 °. ), (211), (310), and (222), if five diffraction peaks indexed, such five diffraction peaks have a d-space ratio of √2: √4: √6: √10. : It shows that it is {square root} 12, and it is confirmed that it is a 3D-Cubic Im3m structure.

  The shape of the catalyst for removing ozonolysis of the present invention is not particularly limited, but the powder, granule, support film, self-supporting film, transparent film, alignment film, spherical shape, fibrous shape, burning on the substrate, micrometer-size clear form Examples of such particles are as follows. Moreover, you may shape | mold and use it in various shapes as needed. The means for molding is not particularly limited, but extrusion molding, tableting molding, rolling granulation, compression molding, CIP and the like are preferable. The shape can be determined according to the location and method of use, and examples thereof include a pellet shape, a columnar shape, a crushed shape, a spherical shape, a honeycomb shape, an uneven shape, and a corrugated shape.

  Next, the manufacturing method of the catalyst for ozonolysis removal of this invention is demonstrated. First, a block copolymer type surfactant as a template and at least one iron salt selected from the group consisting of iron nitrate, iron sulfate, iron halide and organic iron are added to a non-aqueous solvent, A body precursor is generated (first step).

  The non-aqueous solvent used in the present invention is not particularly limited as long as it can dissolve the surfactant and the iron salt, but it is necessary to be a polar solvent in order to form micelles. . Further, the water content of the non-aqueous solvent is preferably 5% by mass or less in order to cause the reaction to proceed very slowly in the process of hydrolyzing the iron salt and forming the pore structure, and preferably 1% by weight or less. It is more preferable that it is 0.5 wt% or less.

  Specific examples of such a non-aqueous solvent include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, and propylene glycol, and ketones such as acetone and methyl ethyl ketone. Such non-aqueous solvents can be used alone or in combination of two or more. In addition, when using in combination of 2 or more types of nonaqueous solvents, it is preferable that all the nonaqueous solvents satisfy | fill the said conditions. Moreover, when mixing and using 2 or more types of nonaqueous solvents, the mixing ratio can be suitably set according to the kind of nonaqueous solvent, the said surfactant, and the said iron salt.

  Among the non-aqueous solvents, ethanol, propanol, ethylene glycol, and mixed solvents thereof are preferable from the viewpoints of easy handling, safety, and cost, and 1-propanol, and 1- A mixed solvent of propanol and ethylene glycol is particularly preferable. Moreover, among the mixed solvent of 1-propanol and ethylene glycol, those containing 300 parts by mass or less of ethylene glycol are preferable with respect to 100 parts by mass of 1-propanol, and those containing 100 parts by mass or less of ethylene glycol are more preferable. preferable. When the mixed solvent containing 1-propanol or ethylene glycol in the above range is used as the nonaqueous solvent, the pore structure can be formed at a moderate rate, and ozonolysis having a good pore structure. A catalyst for removal can be obtained.

  The iron compound used in the present invention includes iron nitrate, iron sulfate, iron halide (eg, iron bromide, iron fluoride, iron chloride) and organic iron (eg, iron acetate, iron oxalate, iron alkoxide (iron ethoxide). Iron isopropoxide, iron butoxide, etc.)))) is selected according to the type of iron oxide that constitutes the desired catalyst for removing ozonolysis, and iron nitrate is particularly preferred from the viewpoint that the anion tends to be thermally decomposed during firing. preferable.

  On the other hand, as the block copolymer type surfactant used as a template in the present invention, ethylene oxide / propylene oxide / ethylene oxide (EO-PO-EO) triblock copolymer and ethylene oxide / butylene oxide (EO-BO) diester are used. Examples include block copolymers. These block copolymers may be used alone or in combination of two.

As the EO-PO-EO triblock copolymer, the following formula (1):
HO (CH ₂ CH ₂ O) _a (CH ₂ CH (CH ₃ ) O) _b (CH ₂ CH ₂ O) _c H (1)
[In Formula (1), a represents 20-150, b represents 20-100, c represents the integer of 20-150, respectively. ]
An EO-PO-EO triblock copolymer represented by the following formula (2) is preferred as the EO-BO diblock copolymer:
_{HO (CH 2 CH 2 O)} x (CH 2 CHCH (CH 3) O) y H (2)
[In Formula (2), x represents an integer of 30 to 60, and y represents an integer of 50 to 150, respectively. ]
An EO-BO diblock copolymer represented by:

  In the method for producing a catalyst for removing ozonolysis of the present invention, the non-aqueous solvent coexists with the iron salt as a starting material and the surfactant as a template to produce a porous precursor. In general, a method is generally used in which a gel of an organic / inorganic composite is first formed, and then the organic / inorganic composite is aged to obtain a porous precursor.

  That is, first, the surfactant as a template is dissolved in the non-aqueous solvent to form micelles. The iron salt is added to the surfactant solution and stirred. The temperature of the surfactant solution at this time is preferably 10 to 80 ° C, more preferably 20 to 40 ° C, and particularly preferably about room temperature. As a result, an organic / inorganic composite gel is formed by the iron salt gathering around the surfactant.

  Further, the surfactant solution containing the gel of the organic / inorganic composite is stirred, and the organic / inorganic composite is aged by promoting hydrolysis of the organic / inorganic composite to obtain a porous precursor. The temperature in such an aging process is preferably 15 ° C to 200 ° C, more preferably 30 ° C to 80 ° C. If this temperature is less than the above lower limit, hydrolysis tends not to be promoted sufficiently. On the other hand, if it exceeds the above upper limit, a reaction vessel having excellent pressure resistance is required and the cost tends to increase. The time in the aging process is preferably 1 minute to 14 days, more preferably 1 hour to 10 days, and particularly preferably 3 days to 7 days. If this time is less than the above lower limit, hydrolysis tends not to be promoted sufficiently. On the other hand, if the upper limit is exceeded, the hydrolysis reaches saturation, meaningless time is spent. Further, the pH of the solution in the aging process is preferably 1 to 14, and more preferably 3 to 8. If this pH is less than the above lower limit, the dissolution of iron in a solvent tends to progress and the yield of the target catalyst for ozonolysis removal tends to be poor. On the other hand, if the upper limit is exceeded, the proportion of iron hydroxide produced and precipitated is high. The yield of the target catalyst for removing ozonolysis tends to be poor.

  In the first step of the method for producing a catalyst for ozonolysis removal of the present invention, the ratio (molar ratio) of the iron salt, the non-aqueous solvent and the surfactant is such that the number of moles of the surfactant is 1. In this case, it is preferable that the iron salt: nonaqueous solvent: surfactant = 50 to 150: 1000 to 2500: 1 (molar ratio). When the ratio of the iron salt is less than the lower limit, the amount of the surfactant with respect to the iron salt is excessively increased, the unreacted surfactant tends to increase and the uniformity of the pores tends to decrease, When the upper limit is exceeded, the amount of the surfactant with respect to the iron salt becomes excessively small, and the pore formation tends to be incomplete. When the ratio of the non-aqueous solvent is less than the lower limit, the amount of the surfactant introduced into the iron salt is saturated, the amount of the unreacted surfactant remaining in the non-aqueous solvent is increased, and the pores are reduced. On the other hand, when the upper limit is exceeded, the surfactant is not sufficiently introduced into the iron salt and the formation of pores tends to be incomplete.

  Furthermore, in the first step of the method for producing the catalyst for removing ozonolysis of the present invention, another metal salt may be added in order to accelerate the aging of the organic / inorganic composite. As such other metal salts, metal salts of group 1 elements (alkali metal salts) and metal salts of group 2 elements (alkaline earth metal salts) in the long-period periodic table proposed by IUPAC are suitable. Among them, alkali metal halides (for example, potassium chloride) are particularly preferable. The amount of such other metal salts added is preferably about 0.1 to 20.0 equivalents, more preferably about 0.5 to 2.0 equivalents with respect to the iron salt. .

  Next, in the method for producing a catalyst for ozonolysis removal of the present invention, the surfactant is removed from the porous body precursor obtained in the first step to obtain a porous body (catalyst for ozonolysis removal). (Second step).

  As a method for removing the surfactant, for example, (i) the surfactant is removed by immersing the porous precursor in a solvent having high solubility in the surfactant (for example, methanol, ethanol, acetone, water). And (ii) a method of removing the surfactant by firing the porous precursor in air or an inert gas at 200 to 700 ° C. for 4 to 6 hours. By such a second step, a catalyst for removing ozonolysis is obtained which is made of crystalline iron oxide and has pores having a central pore diameter of 1 to 20 nm.

  In the production of the catalyst for removing ozonolysis of the present invention, the main components of the decomposition products generated when the surfactant is removed by calcination are water and carbon dioxide, and other cationic or anionic interfaces. The effect on the environment is small compared to the decomposition products generated when the activator is removed by baking. Thus, the catalyst for removing ozonolysis of the present invention has an advantage that the discharge of environmentally hazardous substances is sufficiently prevented even in the production stage.

  Next, the ozonolysis and removal method of the present invention will be described. The ozonolysis and removal method of the present invention is characterized in that ozone is decomposed and removed by bringing a gas containing ozone into contact with the ozonolysis and removal catalyst of the present invention. Examples of the gas include air containing ozone. The operating conditions for contacting the catalyst for removing ozone with the gas containing ozone can be set as appropriate. For example, the contact temperature is preferably room temperature to 200 ° C. from the viewpoint of efficiently decomposing and removing ozone.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example. The F-127 block copolymer and the P-123 block copolymer used as organic templates in the examples and comparative examples are both block copolymer type surfactants manufactured by Aldrich, and each has the following chemical formula:
(F-127)
HO (CH ₂ CH ₂ O) ₁₀₆ (CH ₂ CH (CH ₃ ) O) ₇₀ (CH ₂ CH ₂ O) ₁₀₆ H
(P-123)
HO (CH ₂ CH ₂ O) ₂₀ (CH ₂ CH (CH ₃ ) O) ₇₀ (CH ₂ CH ₂ O) ₂₀ H
It is represented by

Example 1
<Preparation of catalyst for removing ozonolysis>
1 g of F-127 block copolymer was added to 10 g of propanol and stirred to dissolve. Fe (NO ₃ ) ₂ 9H ₂ O (0.1 mol) was added to the resulting solution, and the mixture was vigorously stirred for 2 hours. The obtained sol was aged at 40 ° C. for 5 days, then heated to 120 ° C. at a heating rate of 1 ° C. per minute, and held at 120 ° C. for 4 hours. Thereafter, the organic template, that is, the F-127 block copolymer is extracted with ethanol, and further heated at 300 ° C. to remove the remaining F-127 block copolymer, thereby removing the ozone decomposition catalyst comprising iron oxide. Got.

  This catalyst was dispersed in a copper sample cell, gold was deposited, and observed with a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation. Model number “S-3600N”). As shown in FIG. Is an aggregate of spherical particles of iron oxide, and it was confirmed that secondary pores were formed. Further, it was confirmed by X-ray diffraction pattern that the iron oxide was crystalline.

The nitrogen adsorption isotherm of this catalyst was measured using a gas adsorption pore distribution measuring device (manufactured by Nippon Bell Co., Ltd., model number “BELSORP18”). The result is shown in FIG. As shown in FIG. 2, the catalyst has mesopores because the nitrogen adsorption / desorption curve is type IV and a hysteresis loop was observed in the relative pressure range of 0.5 to 0.9. Was confirmed. The specific surface area determined by the nitrogen adsorption BET method was 124 m ² / g.

  Moreover, the pore distribution curve was calculated | required by BJH (Barrett-Joyner-Halenda) method from the adsorption isotherm shown in FIG. The result is shown in FIG. In FIG. 3, Rp represents the pore radius, and Vp represents the pore volume. The mesopores had a central pore diameter of 16 nm.

The X-ray diffraction pattern of the catalyst was measured using an X-ray diffractometer (manufactured by Rigaku Corporation, model number “RINT2100”), scanning range of 0.5 to 5 °, scanning speed of 1 ° per minute, scanning step of 0.01 °. The measurement was performed under the conditions of divergence and scattering slit 1/6 deg and light receiving slit 0.15 mm. The result is shown in FIG. From this result, it was confirmed that the obtained catalyst was γ-type Fe ₂ O ₃ . Arrows in Figure 4 shows the peak due to _γ-Fe 2 _{O 3.} And Scherrer's formula:
D = 0.9λ / βcos θ
(Wherein D represents the particle diameter, λ represents the wavelength of the X-ray used (1.54060 mm), β represents the diffraction line width of the sample (0.853 ° × π / 180 °), and θ represents (Indicates diffraction angle (35.70 °))
The average primary particle size determined by 1 was 11.5 nm.

<Evaluation of ozonolysis removal performance>
Next, the ozonolysis removal performance of the catalyst for ozonolysis removal consisting of crystalline iron oxide obtained as described above was evaluated. First, the catalyst for ozonolysis removal was formed into pellets having a particle diameter of 0.5 to 1 mm. 0.5 g of this pellet-shaped catalyst was packed in the catalyst bed 1 of the ozonolysis removal performance evaluation apparatus shown in FIG. A mixed gas containing ozone (800 ppm), oxygen (10%), propylene (500 ppmC), and nitrogen is applied to the catalyst bed 1 at a temperature rising rate of 10 ° C. per minute from room temperature to 400 ° C. per minute. The concentration of ozone, carbon monoxide, and carbon dioxide in the mixed gas that was supplied at a flow rate of 5 liters and passed through the catalyst bed 1 was measured. The ozone concentration is measured using a detector tube (manufactured by Komyo Chemical Co., Ltd., model “182SA ozone” or “182SB ozone”), and the concentrations of carbon monoxide and carbon dioxide are non-dispersive infrared absorption type (NDIR). ) Measurement was performed using a gas concentration measuring device (manufactured by Shimadzu Corporation, model number “CGT-7000”).

  FIG. 6 shows the concentrations of ozone, carbon monoxide and carbon dioxide in the mixed gas after passing through the catalyst bed at each supply temperature of the mixed gas.

(Comparative Example 1)
As the catalyst, the catalyst for removing ozone from the crystalline iron oxide obtained in Example 1 was used. The concentrations of carbon monoxide and carbon dioxide in the mixed gas that passed through the catalyst bed 1 in the same manner as in Example 1 except that a mixed gas containing oxygen (10%), propylene (500 ppmC), and nitrogen was used as the mixed gas. Was measured. FIG. 7 shows the concentrations of carbon monoxide and carbon dioxide in the mixed gas after passing through the catalyst bed at each supply temperature of the mixed gas.

(Comparative Example 2)
A reaction tube (no catalyst) was prepared in the same manner as in Example 1 except that the catalyst was not charged and a mixed gas containing ozone (600 ppm), oxygen (10%), propylene (500 ppmC) and nitrogen was supplied as a mixed gas. The concentrations of ozone, carbon monoxide and carbon dioxide in the mixed gas that passed through were measured. FIG. 8 shows the concentrations of ozone, carbon monoxide and carbon dioxide in the mixed gas after passing through the reaction tube at each supply temperature of the mixed gas.

  As is apparent from the results shown in FIG. 6, when the supply temperature of the mixed gas is in the range of room temperature to 150 ° C., it consists of a mixed gas containing ozone and crystalline iron oxide, and the central pore diameter is in the range of 1 to 20 nm. It was confirmed that ozone in the mixed gas was reduced when contacting with a catalyst having certain pores, and carbon monoxide and carbon dioxide were produced.

  On the other hand, as is apparent from the results shown in FIG. 7, when the supply temperature of the mixed gas is in the range of room temperature to 150 ° C., when the supplied mixed gas does not contain ozone, the mixed gas contains oxygen. No carbon monoxide or carbon dioxide was produced even when the catalyst was contacted with a catalyst composed of crystalline iron oxide and having a pore having a central pore diameter in the range of 1 to 20 nm. Further, as is apparent from the results shown in FIG. 8, when the supply temperature of the mixed gas is in the range of room temperature to 150 ° C., when the mixed gas containing ozone is not brought into contact with the catalyst, ozone and propylene are mixed during mixing. Because it reacts even at room temperature, ozone in the mixed gas is reduced and carbon monoxide and carbon dioxide are produced, but the decrease in ozone and the amount of carbon monoxide and carbon dioxide produced are in contact with the mixed gas and the catalyst. In comparison with the case (Example 1).

  Therefore, it was confirmed that ozone can be decomposed and removed by contacting the catalyst of the present invention, which is made of crystalline iron oxide and has a pore having a central pore diameter in the range of 1 to 20 nm, with a gas containing ozone. It was.

(Example 2)
As the catalyst, the catalyst for removing ozone from the crystalline iron oxide obtained in Example 1 was used. Example except that 0.5 g of a pellet-shaped catalyst was packed in the catalyst bed 1 and a mixed gas containing ozone (600 ppm), oxygen (10%) and nitrogen was supplied to the catalyst bed 1 at a constant temperature of 27 ° C. In the same manner as in Example 1, the ozone concentration in the mixed gas that passed through the catalyst bed 1 was measured. The ozone concentration in the steady state was defined as the ozone concentration at the catalyst bed outlet.

On the other hand, the three-way cock 3 is switched, and the mixed gas (ozone: 600 ppm, oxygen: 10%, the rest is nitrogen) is supplied to the bypass 2 at a temperature of 27 ° C. and a flow rate of 5 liters per minute. Was measured. From the ozone concentration C _{cat at the} catalyst bed outlet and the ozone concentration C _{byp at the} bypass outlet, the following formula:
Ozone decomposition removal rate (%) = (C _byp -C _cat ) / C _byp × 100
Was used to calculate the ozonolysis removal rate. The result is shown in FIG.

(Comparative Example 3)
The ozone concentration at the catalyst bed outlet was measured in the same manner as in Example 2 except that MnO ₂ (manufactured by Chuo Electric Industry Co., Ltd., trade name “CMD-200”) was used as the catalyst, and the ozone decomposition removal rate was calculated. . The result is shown in FIG.

(Comparative Example 4)
The nitrogen adsorption isotherm of γ-Fe ₂ O ₃ (manufactured by Kojundo Chemical Laboratory Co., Ltd.) was measured in the same manner as in Example 1. The result is shown in FIG. As shown in FIG. 2, since the adsorption / desorption curve of nitrogen is type III, it was confirmed that this γ-Fe ₂ O ₃ has no mesopores.

The ozone concentration at the catalyst bed outlet was measured in the same manner as in Example 2 except that this γ-Fe ₂ O ₃ was used as a catalyst, and the ozone decomposition removal rate was calculated. The result is shown in FIG.

(Comparative Example 5)
The nitrogen adsorption isotherm of α-Fe ₂ O ₃ (manufactured by Kojundo Chemical Laboratory Co., Ltd.) was measured in the same manner as in Example 1. The result is shown in FIG. As shown in FIG. 2, since the adsorption / desorption curve of nitrogen is type III, it was confirmed that no mesopores exist in this α-Fe ₂ O ₃ .

Except that this α-Fe ₂ O ₃ was used as a catalyst, the ozone concentration at the catalyst bed outlet was measured in the same manner as in Example 2, and the ozonolysis removal rate was calculated. The result is shown in FIG.

(Comparative Example 6)
The nitrogen adsorption isotherm of Fe ₃ O ₄ (manufactured by Kojundo Chemical Laboratory Co., Ltd.) was measured in the same manner as in Example 1. The result is shown in FIG. As shown in FIG. 2, since the adsorption / desorption curve of nitrogen is type III, it was confirmed that no mesopores exist in this Fe ₃ O ₄ .

Except for using this Fe ₃ O ₄ as a catalyst, the ozone concentration at the catalyst bed outlet was measured in the same manner as in Example 2 to calculate the ozone decomposition removal rate. The result is shown in FIG.

(Comparative Example 7)
The nitrogen adsorption isotherm of FeO (II) (manufactured by Kojundo Chemical Laboratory Co., Ltd.) was measured in the same manner as in Example 1. The result is shown in FIG. As shown in FIG. 2, since the adsorption / desorption curve of nitrogen is type III, it was confirmed that no mesopores exist in this FeO (II).

  Except for using this FeO (II) as a catalyst, the ozone concentration at the catalyst bed outlet was measured in the same manner as in Example 2 to calculate the ozone decomposition removal rate. The result is shown in FIG.

(Comparative Example 8)
According to the method described in Applied Catalysis B, Environmental, 11 (1997), 129-166, γ-Al ₂ O ₃ was impregnated with iron nitrate, and Fe ₂ O ₃ supported γ-Al ₂ O ₃ catalyst (Fe ₂ O ₃ (Supported amount: 10% by mass) was prepared.

The ozone concentration at the outlet of the catalyst bed was measured in the same manner as in Example 2 except that this Fe ₂ O ₃ supported γ-Al ₂ O ₃ catalyst was used as a catalyst, and the ozone decomposition removal rate was calculated. The result is shown in FIG.

  As is apparent from the results shown in FIG. 9, the catalyst for removing ozonolysis (Example 2) made of crystalline iron oxide and having pores with a central pore diameter in the range of 1 to 20 nm is obtained by ozonolysis removal. The rate was as high as 84%, and the ozonolysis removal performance was excellent. On the other hand, conventional ozonolysis removal catalysts (Comparative Examples 3 to 8) have an ozonolysis removal rate of 67% (Comparative Example 5) or less, and ozonolysis removal compared to the ozonolysis removal catalyst of the present invention. The performance was inferior.

  As described above, according to the present invention, the catalyst for removing ozonolysis of the present invention having a pore made of crystalline iron oxide and having a central pore diameter in a specific range, and a gas containing ozone. By contacting, ozone can be efficiently decomposed and removed.

  Therefore, the ozonolysis / removal catalyst of the present invention is excellent in ozonolysis / removal performance, and thus is useful as a catalyst for decomposing / removing ozone contained in photochemical oxidants.

2 is a scanning electron micrograph of an ozonolysis removal catalyst comprising iron oxide obtained in Example 1. FIG. It is a graph which shows the nitrogen adsorption isotherm of the catalyst for ozone decomposition removal which consists of iron oxide obtained in Example 1, and the catalyst for ozone decomposition removal used in Comparative Examples 4-7. 2 is a graph showing a pore distribution curve of an ozonolysis removal catalyst comprising iron oxide obtained in Example 1. FIG. 2 is a graph showing an X-ray diffraction pattern of a catalyst for removing ozonolysis composed of iron oxide obtained in Example 1. It is a schematic diagram which shows the ozonolysis removal performance evaluation apparatus used by the Example and the comparative example. It is a graph which shows the relationship between the supply temperature of the mixed gas containing ozone, and the density | concentration of each component in the mixed gas after a catalyst bed passage. It is a graph which shows the relationship between the supply temperature of the mixed gas which does not contain ozone, and the density | concentration of each component in the mixed gas after a catalyst bed passage. It is a graph which shows the relationship between the supply temperature of the mixed gas containing ozone, and the density | concentration of each component in the mixed gas after reaction tube passage. It is a graph which shows the ozonolysis removal rate of the catalyst for various ozonolysis removal used in Example 2 and Comparative Examples 3-8.

Explanation of symbols

  1 ... catalyst bed, 2 ... bypass, 3 ... three-way cock.

Claims (3)

Wherein the spherical particles of _γ-Fe 2 _{O 3} crystalline is made of aggregated, the mean pore diameter have a pore of 1 to 20 nm, BET specific surface area of ^{50 m} 2 / g or more Ozone decomposition removal catalyst.   The catalyst for removing ozone decomposition according to claim 1, wherein the pores are secondary pores. A method for decomposing and removing ozone, comprising contacting a gas containing ozone with the catalyst for decomposing and removing ozone according to claim 1 or 2 .