JP2023003146A - Voc removal catalyst, method for producing the same and voc removal method - Google Patents

Abstract

To provide a VOC removal catalyst that can be easily produced, has high VOC removal efficiency, and can efficiently remove VOC even at low temperatures, a method for producing the same, and a VOC removal method.SOLUTION: A VOC removal catalyst according to the present invention contains MnOx (x is any number of 1 or more and 2 or less) with a BET specific surface area of 10-200 m2/g. A production method according to the present invention includes: a step 1 of mixing a source liquid A containing a manganese source with a source liquid C containing a reductant to give a reaction liquid; a step 2 of irradiating the reaction liquid formed in the step 1 with microwaves to give a suspension; and a step 3 of firing a solid content separated from the suspension formed in the step 2.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a VOC removal catalyst, a method for producing the same, and a method for removing VOCs.

VOC is an abbreviation for Volatile Organic Compounds, and known examples include toluene, xylene, benzene, ethyl acetate, methanol, and dichloromethane. While such VOCs are widely used in solvents, adhesives, chemical raw materials, etc., it is pointed out that VOCs cause photochemical oxidants or suspended particulate matter (SPM). The Pollution Control Law strictly regulates its emissions. Therefore, in order to further reduce the amount of VOC emissions, it is desired to establish a technique for removing VOCs more efficiently.

A method using catalytic oxidation is known as a technique for removing VOCs. This method is believed to be the most promising in that VOC removal occurs at relatively low temperatures. Since transition metal oxides are mainly used in catalytic oxidation methods, they are more cost-effective than noble metal catalysts. From this point of view, studies have been extensively conducted to improve the catalytic performance of transition metal oxides. ing. For example, Patent Literature 1 discloses a technique for efficiently removing VOCs using a material containing manganese (IV) oxide.

JP 2019-147131 A

However, conventional VOC removal catalysts still do not have sufficient VOC removal performance in low-temperature environments, and there is also the problem that it takes time to manufacture. It had. From this point of view, it is currently desired to develop a catalyst that can be easily produced and that can efficiently remove VOCs even at low temperatures.

The present invention has been made in view of the above, and is a VOC removal catalyst that is easy to manufacture, has excellent VOC removal efficiency, and can efficiently remove VOCs even at low temperatures, a method for producing the same, and a VOC removal catalyst. The object is to provide a removal method.

As a result of intensive studies aimed at achieving the above object, the present inventors have found that the above object can be achieved by using a specific manganese oxide as an essential component of a VOC removal catalyst, and have completed the present invention. .

That is, the present invention includes, for example, the subject matter described in the following sections.
Item 1
A VOC removal catalyst,
A VOC removal catalyst containing MnO _x (x is a number of 1 or more and 2 or less) having a BET specific surface area of 10 to 200 m ² /g.
Item 2
Item 2. The VOC removal catalyst according to Item 1, wherein _1≤D≤10 , where D (nm) is the pore diameter at the maximum peak in the log differential pore volume distribution curve of MnOx.
Item 3
In the cumulative pore volume distribution curve of the MnO _x , when the cumulative pore volume at the pore diameter D (nm) is V (cm ³ /g), 0.05 ≤ V ≤ 0.5. Item 3. The VOC removal catalyst according to item 2.
Item 4
4. The VOC removal catalyst according to any one of Items 1 to 3, wherein the MnO _x is particulate.
Item 5
Step 1 of obtaining a reaction liquid by mixing a raw material liquid A containing a manganese source and a raw material liquid C containing a reducing agent;
Step 2 of obtaining a suspension by irradiating the reaction solution obtained in Step 1 with microwaves;
A method for producing a VOC removal catalyst, comprising step 3 of calcining the solid content separated from the suspension obtained in step 2.
Item 6
Item 6. The method for producing a VOC removal catalyst according to Item 5, wherein the reducing agent is a carboxylic acid compound and/or vitamin C.
Item 7
Item 7. The method for producing a VOC removal catalyst according to Item 6, wherein the carboxylic acid compound is at least one selected from the group consisting of citric acid, formic acid, and acetic acid.
Item 8
A VOC comprising a step of decomposing VOC using the VOC removal catalyst according to any one of Items 1 to 4 or the VOC catalyst obtained by the production method according to any one of Items 5 to 7. removal method.

The VOC removal catalyst of the present invention is easy to manufacture, has excellent VOC removal efficiency, and can efficiently remove VOCs even at low temperatures.

1 is a schematic diagram showing a flow of an evaluation test method for a VOC removal catalyst; FIG. SEM images of catalysts obtained in Examples 1 to 4 and Comparative Example 1 are shown. 1 shows XRD spectra of catalysts obtained in Examples 1 to 4 and Comparative Example 1. FIG. (a) shows the specific surface area measurement results of the catalysts obtained in Examples 1 to 4 and Comparative Example 1 by the gas adsorption method (BET method), and (b) shows the pore distribution curve (Log differential pore volume distribution). indicates 4 shows the results of VOC removal tests using the catalysts obtained in Examples and Comparative Examples.

1. VOC Removal Catalyst The VOC removal catalyst of the present invention contains MnO _x (x is a number of 1 or more and 2 or less) having a BET specific surface area of 10 to 200 m ² /g. The BET specific surface area referred to in the present invention means a value calculated by the BET method based on the adsorption amount at a relative pressure of 0.1 or less from the nitrogen adsorption isotherm at the boiling point temperature of liquid nitrogen.

In the VOC removal catalyst of the present invention, the oxide of manganese, that is, the MnO _x (x is a number of 1 or more and 2 or less) has a specific surface area within the above range, so that an abundant defect structure is formed in MnO _x . As a result, VOC removal efficiency is excellent and VOC can be removed efficiently even at low temperatures. That is, by using the VOC removal catalyst of the present invention, even if VOCs are decomposed in a lower temperature range than conventional ones, VOCs can be removed with high efficiency. Also, the VOC removal catalyst of the present invention can be easily produced.

In MnO _x , x is not particularly limited as long as it is a number of 1 or more and 2 or less. Also, x may be 1 or 2. Specifically, MnO _x is exemplified by MnO, Mn ₃ O ₄ , Mn ₂ O ₃ and MnO ₂ . The MnO _x contained in the VOC removal catalyst of the present invention may contain only one of these, or may contain two or more.

When the BET specific surface area of MnO _x is less than 10 _m ² /g, the defect structure becomes insufficient and the aggregation of MnO _x becomes strong, resulting in a decrease in VOC removal efficiency. If it exceeds 200 m ² /g, the defect structure becomes too many, and the VOC removal efficiency at low temperature decreases. The BET specific surface area of MnO _x is preferably 20 m ² /g or more, more preferably 30 m ² /g or more, still more preferably 40 m ² /g or more, and 50 m ² /g or more. is particularly preferred. Also, the BET specific surface area of MnO _x is preferably 195 m ² /g or less, more preferably 190 m ² /g or less, even more preferably 185 m ² /g or less.

The method for adjusting the BET specific surface area of MnO _x to the desired range is not particularly limited, and for _example , a wide range of known methods can be employed. It is easy to adjust the BET specific surface area of _MnOx to a desired range.

In one aspect of the present invention, it is preferable that 1≦D≦10, where D (nm) is the pore diameter at the maximum peak in the log differential pore volume distribution curve of MnO _x . In this case, the VOC removal catalyst of the present invention can efficiently remove VOCs even at a lower temperature, and tends to be excellent in VOC removal efficiency.

The pore diameter D (nm) is more preferably 2 or more, still more preferably 2.5 or more, and particularly preferably 3 or more. The pore diameter D (nm) is more preferably 9 or less, even more preferably 8 or less, and particularly preferably 7 or less.

A method for adjusting the pore diameter D (nm) of MnO _x to a desired range is not particularly limited. Among others, in the method of obtaining MnO 2 _x by steps 1 to 3 described later, the pore diameter D (nm) of MnO 2 _x can be easily adjusted within a desired range.

The log differential pore volume distribution curve of _MnOx can be derived by nitrogen molecular adsorption method. Specifically, the measurement sample is vacuum-degassed at 300° C. for 12 hours and then adsorbed with nitrogen molecules at −198° C., whereby the Log differential pore volume distribution curve of MnO _x can be derived. The curve can be derived by Nova4200 equipment (Quantachrome Inc., USA).

Further, in the present invention, in the cumulative pore volume distribution curve of MnO _x , when the cumulative pore volume at the pore diameter D (nm) is V (cm ³ /g), 0.05 ≤ V ≤ 0 .5 is preferred. In this case, the VOC removal catalyst of the present invention can efficiently remove VOCs even at a lower temperature, and tends to be excellent in VOC removal efficiency. The integrated pore volume distribution curve of MnO _x can be derived by the BJH method based on the log differential pore volume distribution curve.

The cumulative pore volume V (cm ³ /g) is more preferably 0.07 or more, and even more preferably 0.1 or more. Further, the value of the accumulated pore volume V (cm ³ /g) is more preferably 0.4 or less, further preferably 0.35 or less, and particularly preferably 0.3 or less. .

The method for adjusting the cumulative pore volume V (cm ³ /g ₎ of _{MnO x} to a desired range is not particularly limited. It is easy to adjust the pore volume V (cm ³ /g) within a desired range.

The shape of MnO _x contained in the VOC removal catalyst of the present invention is not particularly limited, and can be, for example, particulate. When the shape of MnO _x is particulate, it may be spherical or non-spherical such as irregular.

When the shape of MnO 2 _x is particulate, the average particle diameter is not particularly limited, and can be, for example, 1 to 1000 nm, preferably 10 to 500 nm. The average particle size of MnO _x referred to here is the arithmetic mean value obtained by measuring the equivalent circle diameters of 50 particles selected at random by direct observation of the electrode with a scanning electron microscope.

MnO _x may be crystalline or amorphous. MnO _x preferably has a low degree of crystallinity, so that MnO _x has many oxygen vacancies, so VOCs can be efficiently removed even at low temperatures.

The VOC removal catalyst of the present invention can also contain components other than _MnOx (eg, other elements, compounds, additives, etc.) as long as the effects of the present invention are not impaired. The VOC catalyst of the present invention may be formed of _MnOx only, and in this case, it is allowed to contain unavoidable elements, components, etc. that may be contained in the VOC catalyst. The VOC catalyst of the present invention preferably contains 60% by mass or more of _MnOx , more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

The VOC removal catalyst of the present invention is, for example, in the form of powder, and can be in various forms such as granules and lumps.

In the VOC removal catalyst of the present invention, the manganese (Mn) element content is, for example, preferably at least 40% by mass, more preferably at least 45% by mass. In addition, in the VOC removal catalyst of the present invention, the manganese (Mn) element content is, for example, preferably 70% by mass or less, more preferably 65% by mass or less, and 60% by mass or less. is particularly preferred.

In the VOC removal catalyst of the present invention, the oxygen element content is, for example, preferably 35% by mass or more, more preferably 40% by mass or more. In addition, in the VOC removal catalyst of the present invention, the oxygen element content is, for example, preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. .

In the VOC removal catalyst of the present invention, the content of elements other than manganese and oxygen is, for example, 10% by mass or less, preferably 8% by mass or less, more preferably 6% by mass or less.

The method for producing the VOC removal catalyst of the present invention is not particularly limited, and for example, it can be produced by various known methods. Specifically, the VOC removal catalyst of the present invention can be produced by a production method comprising Steps 1, 2 and 3, which will be described later.

2. Method for Producing VOC Removal Catalyst The method for producing the VOC removal catalyst of the present invention comprises steps 1, 2 and 3 below.
Step 1: A step of obtaining a reaction liquid by mixing a raw material liquid A containing a manganese source and a raw material liquid C containing a reducing agent.
Step 2: A step of irradiating the reaction solution obtained in Step 1 with microwaves to obtain a suspension.
Step 3: A step of firing the solid content separated from the suspension obtained in Step 2 above.

(Step 1)
In step 1, a reaction liquid is obtained by mixing a raw material liquid A containing a manganese source and a raw material liquid C containing a reducing agent.

The raw material liquid A containing the manganese source used in step 1 has the manganese source dissolved or dispersed in a solvent. The manganese source may be manganese alone or a manganese-containing compound, preferably a manganese-containing compound.

The type of manganese-containing compound is not particularly limited, and examples thereof include various inorganic compounds containing manganese. Inorganic compounds containing manganese include, for example, permanganates, manganese nitrates, sulfates, chlorides, hydrochlorides, chlorates, perchlorates, carbonates, hydrogencarbonates, phosphates and phosphoric acids. Hydrogen salts and the like can be mentioned, and among them, the inorganic compound containing manganese is preferably permanganate. Potassium permanganate (KMnO ₄ , K ₂ MnO ₄ etc.) can be mentioned as a specific permanganate.

Other compounds containing manganese include various organic compounds containing manganese, such as manganese acetate, oxalate, formate and succinate.

The manganese-containing compound can also contain two or more different anions (for example, ammonium manganese sulfate, etc.).

It is particularly preferred to use potassium permanganate (KMnO ₄ ) as the manganese source in that it tends to facilitate the production of the VOC catalyst.

In the raw material liquid C containing the reducing agent used in step 1, the reducing agent is dissolved or dispersed in the solvent.

The type of reducing agent is not particularly limited, and for example, a wide range of known reducing agents can be used. Specifically, a carboxylic acid compound and/or vitamin C can be mentioned as a reducing agent. Examples of carboxylic acid compounds include various compounds having a reducing action, and examples include at least one selected from the group consisting of citric acid, formic acid, and acetic acid. The reducing agent is preferably citric acid because it has excellent VOC removal efficiency at low temperatures and is easy to exhibit the etching action on the catalyst surface.

One type of reducing agent can be used alone, or two or more types can be used in combination.

Both the raw material liquid A and the raw material liquid C can contain a solvent. The type of solvent is not particularly limited, and examples include water; alcohols having 1 to 4 carbon atoms such as methanol and ethanol; and mixed solvents thereof; amide solvents such as N,N-dimethylformamide; Pyrrolidone-based solvents and the like can be used. The solvent contained in the raw material liquid A and the raw material liquid C is preferably water and the alcohol, or a mixed solvent thereof, more preferably water, in that the reaction in step 1 proceeds easily. The solvents contained in the raw material liquid A and the raw material liquid C may be the same as each other, or may be partially or wholly different, and both are more preferably water.

The concentration of the manganese source in the raw material liquid A is not particularly limited. For example, the concentration of manganese in the raw material liquid A can be 1×10 ⁻⁴ to 2M, preferably 1×10 ⁻³ to 1M, more preferably 1×10 ⁻² to 0.1M.

In the raw material liquid C, the concentration of the reducing agent is not particularly limited. For example, the concentration of the reducing agent in the raw material liquid C can be 1×10 ⁻⁴ to 10M, preferably 1×10 ⁻³ to 8M, more preferably 1×10 ⁻² to 5M.

In step 1, the amount of raw material liquid C used is not particularly limited. For example, the amount of the raw material liquid C can be adjusted so that the molar ratio of the reducing agent to manganese in the raw material liquid C (reducing agent:manganese) is 1:0.1 to 1:5.

In step 1, the method of mixing the raw material liquid A and the raw material liquid C is not particularly limited. As an example, the mixing process can be performed by adding the raw material liquid A to the raw material liquid C being stirred. In this case, the raw material liquid A can be added to the raw material liquid C. The rate at which raw material liquid A is added to raw material liquid C is not particularly limited.

In the mixing process of the raw material liquid A and the raw material liquid C, the temperature during mixing is not particularly limited, and can be, for example, 5 to 40° C., preferably around room temperature (eg, 15 to 30° C.). The time for the mixing treatment is also not particularly limited, and can be appropriately set according to the temperature at the time of mixing.

By mixing the raw material liquid A and the raw material liquid C, the manganese source and the reducing agent react to obtain a reaction liquid. Such a reaction liquid is, for example, a solution or a dispersion liquid (preferably a dispersion liquid) having a blackish brown color or a dark brown color.

(Step 2)
Step 2 is a step for irradiating the reaction solution obtained in Step 1 with microwaves. The device used for microwave irradiation is not particularly limited, and a wide range of known microwave irradiation devices can be used.

Microwave irradiation conditions are also not particularly limited. For example, the set power in the microwave irradiation device is preferably 500 to 1500 W in that the obtained MnOx tends to have the desired specific surface area, the pore diameter D and the cumulative pore volume V. is 600-100W, and can be 700W. Microwaves can be irradiated with power of 1 to 100% of each power. The microwave irradiation time T can be appropriately set according to the power, etc., and T is set to 1 to 120 minutes in that the specific surface area, the pore diameter D, and the accumulated pore volume V are likely to be obtained. be able to. The temperature of the reaction solution during microwave irradiation can be appropriately set according to the boiling point of the reaction solution, and is, for example, 100° C. when the solvent of the reaction solution is water.

Further, in order to facilitate temperature control of the reaction solution during microwave irradiation, it is preferable to perform microwave irradiation at regular intervals. Specifically, a cycle of irradiating microwaves over a period of X (seconds) until reaching the set power and then reducing the power to 0 W over a period of X (seconds) is repeated. This cycle can be repeated until the total time T reaches the microwave irradiation. In this specification, X may be referred to as the number of cycles. The cycle number X is preferably 1 to 10 seconds, preferably 2 to 8 seconds.

When irradiating the reaction solution with microwaves, the container for containing the reaction solution is not particularly limited, but commercially available transparent glass containers, beakers, flasks, and the like can be used, for example. Irradiation with microwaves can be performed, for example, in an air atmosphere with the reaction solution sealed.

Microwave irradiation in step 2 yields a suspension. The obtained suspension can be subjected to solid-liquid separation by appropriate separation means or purification means. The solid content obtained by solid-liquid separation can be dried if necessary.

(Step 3)
Step 3 is a step for firing the solid content separated from the suspension obtained in Step 2. By such a calcination treatment, the desired VOC removal catalyst containing magnesium oxide is obtained.

In step 3, the method of firing treatment is not particularly limited, and a wide range of known firing methods can be employed. For example, the temperature of the baking treatment can be 200° C. or higher. In addition, the temperature of the calcination treatment is preferably 600° C. or less because the crystallinity of manganese oxide in the VOC catalyst obtained by calcination tends to be low. A preferable firing temperature is 250 to 480°C, a more preferable firing temperature is 290 to 450°C, and a further preferable firing temperature is 300 to 400°C.

The firing time may be appropriately selected depending on the firing temperature, and may be, for example, 1.5 to 5 hours. In step 3, the rate of temperature increase during firing is not particularly limited, and can be set as appropriate. For example, it is 1 to 10° C./min.

The calcination treatment may be performed either in air or in an inert gas atmosphere. Preferably, the calcination treatment is performed in the air. For the firing treatment, for example, a known heating device such as a commercially available heating furnace can be used.

By the calcination treatment in step 3, for example, the remaining reducing agent and the like are removed, and the desired VOC removal catalyst can be obtained. The resulting VOC removal catalyst contains the aforementioned MnO _x .

According to the production method comprising the above steps 1 to 3, the VOC removal catalyst of the present invention can be easily obtained through simple steps, and the obtained VOC removal catalyst efficiently removes VOCs even at low temperatures. can be removed.

3. VOC Removal Method The VOC removal method of the present invention comprises a step of burning VOCs using the VOC removal catalyst described above or the VOC catalyst obtained by the production method including steps 1, 2 and 3 above.

For example, a VOC removal catalyst is placed in a container, a VOC such as toluene is introduced into the container, and treated at a predetermined temperature to burn the VOC. Thereby, VOC can be removed. If desired, one or both of nitrogen and oxygen can be flowed into the vessel and the VOC can be burned in the presence of one or both of nitrogen and oxygen.

There are no particular restrictions on the type of container used for removing VOCs, and for example, a wide range of known containers used for catalytic combustion of VOCs can be used. The treatment temperature of VOCs in the vessel is not particularly limited, and may be similar to the treatment temperature set for known VOC removal. In particular, in the present invention, by using the above VOC removal catalyst, VOCs can be removed even at low temperatures.
Excellent removal efficiency.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the embodiments of these examples.

(Example 1)
While stirring the 0.1 M citric acid aqueous solution (raw material solution C), the 0.2 mM KMnO ₄ aqueous solution (raw material solution A) was added dropwise to the raw material solution C at a supply rate of 10 mL/min (step 1). A suspension was obtained by irradiating a brown-black reaction liquid obtained by the dropwise addition with microwaves for 10 minutes in an air atmosphere (step 2). In the microwave irradiation in step 2, a "μReactor Ex type" manufactured by Kokusoku Keisoku Kogyo Co., Ltd. was used as the microwave device, and the power was 100% and the cycle was 3 seconds. The suspension obtained in step 2 was centrifuged to recover the solid content, and the obtained solid content was washed with deionized water three times and then dried at 60° C. for 12 hours. Next, the dried solid content was heated to 350° C. at a heating rate of 5° C./min in an air atmosphere in a muffle furnace, and was held at this temperature for 4 hours to perform a calcination treatment (step 3). Through this step 3, MnO _x (where x was 1 or more and 2 or less) was obtained. The obtained manganese oxide was described as "Mn-MW-10min".

(Example 2)
In the process, manganese oxide was obtained in the same manner as in Example 1, except that the microwave irradiation was changed to 30 minutes. The obtained manganese oxide was described as "Mn-MW-30min".

(Example 3)
In the process, manganese oxide was obtained in the same manner as in Example 1, except that the microwave irradiation was changed to 60 minutes. The obtained manganese oxide was described as "Mn-MW-60min".

(Example 4)
In the process, manganese oxide was obtained in the same manner as in Example 1, except that the microwave irradiation was changed to 120 minutes. The obtained manganese oxide was described as "Mn-MW-120min".

(Comparative example 1)
While stirring the 0.1 M citric acid aqueous solution (raw material solution C), the 0.2 mM KMnO ₄ aqueous solution (raw material solution A) was added dropwise to the raw material solution C at a supply rate of 10 mL/min (step 1). The brown-black reaction liquid obtained by the dropwise addition was heat-treated at 100° C. for 120 minutes to obtain a suspension. The resulting suspension was centrifuged to recover the solid content, and the obtained solid content was washed with deionized water three times and then dried at 60° C. for 12 hours. Next, the dried solid content was heated to 350° C. at a heating rate of 5° C./min in an air atmosphere in a muffle furnace, and was held at this temperature for 3 hours for firing treatment. The manganese oxide obtained by this firing treatment was described as "Mn-aging 100°C".

<Evaluation method>
(VOC removal test)
According to the schematic flow shown in FIG. 1, the VOC removal catalyst obtained in each example was subjected to a toluene removal test. In this test, the VOC removal catalyst was filled in a container so as to be sandwiched between quartz wools, and toluene was allowed to flow into the container at a predetermined flow rate for reaction, thereby removing toluene. As shown in FIG. 2, the container is connected to oxygen and nitrogen cylinders to allow oxygen and nitrogen to flow into the container. As the conditions for the toluene removal test, a glass reactor with an inner diameter of 8 mm was used, and the VOC removal catalyst was charged in an amount of 50 mg, and the toluene concentration in the container was adjusted to 1000 ppm by volume. Further, the carrier nitrogen gas flow rate into the container was 35 cm ³ /min, the toluene introduction nitrogen gas flow rate was 5 cm ³ /min, and the oxygen gas flow rate was 10 cm ³ /min. The reaction temperature in the vessel was adjusted to various temperatures ranging from 130 to 300° C. to evaluate the toluene removal properties. In the range of 130 to 200°C, sampling is performed three times every 10°C, in the range of 200 to 250°C, sampling is performed three times in every 5°C, and in the range of 260 to 300°C, sampling is performed three times in every 10°C. Did. The VOC concentration was measured using a Shimadzu Corporation GC-2014 gas chromatograph. Also, the concentration of carbon dioxide discharged from the container outlet was measured using an FT-IR gas analyzer "FG-120" manufactured by HORIBA.

2 shows SEM images of the catalysts obtained in Examples 1-4 and Comparative Example 1. FIG. From the comparison of the shapes of the catalysts obtained in Examples 1 to 4 and Comparative Example 1, the catalysts obtained in Examples 1 to 4 obtained by irradiating microwaves have a smaller particle size and a spherical shape than Comparative Example 1. It became clear that nanoparticles were formed.

Table 1 shows the results of elemental analysis of the catalysts obtained in Examples 1 to 4 and Comparative Example 1 by EDS analysis.

FIG. 3 shows the XRD spectra of the catalysts obtained in Examples 1-4 and Comparative Example 1. In the XRD spectra, the peak intensity (particularly the (211) plane peak at 36-40°) was found to increase with increasing irradiation time up to 60 minutes of microwave irradiation. The main peak of the (211) plane indicates the onset of peak splitting, and no peak shift was observed between samples, confirming that there was no change in the onset of lattice dislocations. In addition, in the XRD spectrum, by microwave treatment, K ₂ Mn ₄ O ₉ and K ₂ Mn ₂ O ₃ peaks (indicated by diamonds and hearts in FIG. 3, respectively) appeared, and new phases appeared after microwave treatment. It was also suggested that it was produced

FIG. 4(a) shows the specific surface area measurement results of the catalysts obtained in Examples 1 to 4 and Comparative Example 1 by the gas adsorption method (BET method), and FIG. pore volume distribution).

Table 2 summarizes the results of FIGS. 4(a) and (b), and specifically shows the BET specific surface area, pore diameter D, and cumulative pore volume V at the pore diameter D of each catalyst. there is

FIG. 5 shows the results of a VOC removal test using the catalysts obtained in Examples 1-4 and Comparative Example 1. FIG. Specifically, FIG. 5 is a plot showing the relationship between temperature (X-axis) and toluene removal rate (Y-axis). In the graph of FIG. 5, the values of the 50% decomposition temperature (T _50% ), 90% decomposition temperature (T _90% ), and 100% decomposition temperature (T _100% ) of toluene for each catalyst are inserted. there is

5 and Table 3 show that the VOC removal catalysts obtained in each example have VOC removal performance superior to that of Comparative Example 1.

From the above, it was found that the VOC removal catalyst obtained in each example can be suitably used as a catalyst for catalytic combustion of toluene, which is one of typical VOC substances.

Claims (8)

A VOC removal catalyst,
A VOC removal catalyst containing MnO _x (x is a number of 1 or more and 2 or less) having a BET specific surface area of 10 to 200 m ² /g. 2. The VOC removal catalyst according to claim 1, wherein _1≤D≤10 , where D (nm) is the pore diameter at the maximum peak in the log differential pore volume distribution curve of MnOx. In the cumulative pore volume distribution curve of the MnO _x , when the cumulative pore volume at the pore diameter D (nm) is V (cm ³ /g), 0.05 ≤ V ≤ 0.5. The VOC removal catalyst according to claim 2. The VOC removal catalyst according to any one of claims 1 to 3, wherein said MnO _x is particulate. Step 1 of obtaining a reaction liquid by mixing a raw material liquid A containing a manganese source and a raw material liquid C containing a reducing agent;
Step 2 of obtaining a suspension by irradiating the reaction solution obtained in Step 1 with microwaves;
A method for producing a VOC removal catalyst, comprising step 3 of calcining the solid content separated from the suspension obtained in step 2. 6. The method for producing a VOC removal catalyst according to claim 5, wherein said reducing agent is a carboxylic acid compound and/or vitamin C. 7. The method for producing a VOC removal catalyst according to claim 6, wherein said carboxylic acid compound is at least one selected from the group consisting of citric acid, formic acid and acetic acid. A step of decomposing VOCs using the VOC removal catalyst according to any one of claims 1 to 4 or the VOC catalyst obtained by the production method according to any one of claims 5 to 7. , VOC removal methods.

Images