JP2021126599A - Voc removal catalyst and method for producing the same - Google Patents

Abstract

To provide a precursor for producing a VOC removal catalyst which can be easily produced and can efficiently remove a VOC even at a low temperature and to provide a VOC removal catalyst and a method for producing the same.SOLUTION: There is provided a VOC removal catalyst containing amorphous manganese oxide in which a rare earth element is doped in amorphous manganese oxide. There is provided a VOC removal catalyst in which the rare earth element is at least one selected from the group consisting of La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. There is provided a VOC removal catalyst in which 0.1 to 5 mass% of a rare earth element is contained based on the total mass of the amorphous manganese oxide. There is provided a method for producing a VOC removal catalyst which comprises: a step 1 of mixing a raw material liquid A containing a manganese source and a raw material liquid B containing a rare earth element source to obtain a product; and a step 2 of firing the product obtained in the step 1.SELECTED DRAWING: Figure 4

Description

The present invention relates to a VOC removal catalyst and a method for producing the same.

VOC is an abbreviation for volatile organic compounds, and for example, toluene, xylene, benzene, ethyl acetate, methanol, dichloromethane and the like are known. While such VOCs are widely used in solvents, adhesives, raw materials for chemicals, etc., it has been pointed out that VOCs cause photochemical oxidants or suspended particulate matter (SPM). Its emissions are strictly regulated by the Air Pollution Control Law. Therefore, in order to further reduce VOC emissions, it is desired to establish a technique for removing VOCs more efficiently.

As a technique for removing VOC, a method by catalytic oxidation is known. This method is considered to be the most promising in that VOC removal is performed at relatively low temperatures. Since the transition metal oxide is mainly used in the method by catalytic oxidation, it is advantageous in terms of cost as compared with the noble metal catalyst, and from this viewpoint, studies for improving the catalytic performance of the transition metal oxide have been widely conducted. ing. For example, Non-Patent Document 1 describes _{urea and odor in an aqueous solution containing Cu (NO 3} ) ₂ , Ce (NO ₃ ) ₂ , and M (NO ₃ ) ₂ (M = Y, Eu, Ho, Sm, etc.). A technique has been proposed for synthesizing _{a catalyst CuMCeO x in} which copper and a second lanthanoid species are combined by adding cetyltrimethylammonium bromide. It is said that such a catalyst can remove VOC more efficiently than pure cerium oxide.

Catalysis Science & Technology, 2018, 8 (22). DOI: 10.1039 / C8CY01849A

However, even with the catalyst described in Non-Patent Document 1, there is a problem that the VOC removal performance is still insufficient in a low temperature environment and it takes time to manufacture, so that it is comprehensive considering practical use. It still had problems. From this point of view, it is currently desired to develop a catalyst that can be easily produced and can efficiently remove VOCs even at a low temperature.

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

The present inventors have focused on manganese-based oxide catalysts in order to achieve the above object. Specifically, since manganese oxide is rich in surface oxygen species, it has the potential to have high catalytic activity, and from this point of view, we have conducted extensive research. As a result, they have found that the above object can be achieved by using amorphous manganese oxide doped with a rare earth element, and have completed the present invention.

That is, the present invention includes, for example, the subjects described in the following sections.
Item 1
VOC removal catalyst
Contains amorphous manganese oxide,
A VOC removal catalyst in which the amorphous manganese oxide is doped with a rare earth element.
Item 2
Item 2. VOC removal according to Item 1, wherein the rare earth element is at least one selected from the group consisting of La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. catalyst.
Item 3
Item 2. The VOC removal catalyst according to Item 1 or 2, wherein the rare earth element is contained in an amount of 0.1 to 5% by mass based on the total mass of the amorphous manganese oxide.
Item 4
The method for producing a VOC removal catalyst according to any one of claims 1 to 3.
Step 1 of obtaining a product by mixing a raw material liquid A containing a manganese source and a raw material liquid B containing a rare earth element source.
Step 2 of firing the product obtained in step 1 and
A method for producing a VOC removal catalyst.
Item 5
Item 4. The production method according to Item 4, wherein the firing temperature in the step 2 is 300 to 400 ° C.
Item 6
A method for removing VOCs, comprising a step of decomposing VOCs using the VOC removal catalyst according to any one of Items 1 to 3 or the VOC catalyst obtained by the production method according to Item 4 or 5.

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

It is the schematic which shows an example of the manufacturing method of the VOC removal catalyst of this invention. It is the schematic which shows the flow of the evaluation test method of a VOC removal catalyst. The SEM images of the VOC removal catalysts obtained in Examples 1 to 3 and Comparative Examples 1 and 2 are shown. The XRD spectra of the VOC removal catalysts obtained in Examples 1 to 3 and Comparative Examples 1 and 2 are shown. The results of the VOC removal test using the VOC removal catalysts obtained in Examples and Comparative Examples are shown.

Hereinafter, embodiments of the present invention will be described in detail.

1. 1. VOC Removal Catalyst The VOC removal catalyst of the present invention contains amorphous manganese oxide, and the amorphous manganese oxide is doped with a rare earth element. The VOC removal catalyst of the present invention has a property that VOC can be decomposed by oxidation or the like. In particular, the VOC removal catalyst of the present invention is easy to manufacture and can efficiently remove VOCs even at low temperatures. Hereinafter, specific embodiments of the VOC removal catalyst of the present invention will be described.

The VOC removal catalyst contains manganese oxide. This manganese oxide is a main component of the VOC removal catalyst of the present invention. The manganese oxide is, for example, MnO ₂ .

Manganese oxide contained in the VOC removal catalyst is amorphous, that is, it does not have a crystal structure. Since the VOC removal catalyst contains such amorphous manganese oxide, the VOC removal efficiency becomes excellent even at a low temperature. Although we do not want a limited interpretation, the amorphous structure of manganese oxide increases the surface area of manganese oxide and increases the number of active sites generated from oxygen vacancies, resulting in excellent catalytic performance. It is presumed to have.

Whether or not the manganese oxide contained in the VOC removal catalyst has an amorphous structure can be determined from, for example, the XRD spectrum of the VOC removal catalyst.

In the VOC removal catalyst of the present invention, amorphous manganese oxide is doped with a rare earth element. In other words, the VOC removal catalyst of the present invention is a material containing amorphous manganese oxide and a rare earth element.

The type of rare earth element is not particularly limited, and examples thereof include at least one selected from the group consisting of La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. be able to. All of these rare earth elements can replace a part of tetravalent manganese ions in manganese oxide. However, since these rare earth elements are stable in a trivalent state, in manganese oxide containing these elements, the number of oxide ions is the original ratio in manganese oxide in order to maintain electrical neutrality. It is less than Mn: O = 1: 2. By this action, many oxygen defects are formed and the oxygen storage capacity can be enhanced, which is advantageous for low temperature oxidation of VOC as a result. The above action can be exhibited as long as it is a lanthanoid element whose ionic radius is not significantly different from that of manganese. From this point of view, the rare earth element contained in the VOC removal catalyst of the present invention is preferably at least one selected from the group consisting of Sm and Ho in that the VOC removal efficiency is likely to increase, and in particular, at least Ho is used. It is more preferable to include it.

The rare earth element contained in the VOC removal catalyst may be one kind alone or two or more kinds.

Rare earth elements can be present in VOC removal catalysts, for example, as metal oxides.

In the VOC catalyst of the present invention, the existence state of amorphous manganese oxide and a rare earth element is not particularly limited. For example, the rare earth element may be present in the amorphous manganese oxide, not inside the amorphous manganese oxide, or may be present on the surface together with the inside. Rare earth elements may be uniformly present throughout the amorphous manganese oxide, or may be unevenly distributed. Rare earth elements can also be present in VOC catalysts independently of amorphous manganese oxide.

In the VOC catalyst of the present invention, the shape of amorphous manganese oxide is not particularly limited, and regardless of whether the amorphous manganese oxide contains a rare earth element or not, for example, particle-like, rod-like, needle-like, fibrous, or phosphorus. It can take various shapes such as flakes. Among them, amorphous manganese oxide is preferably in the form of particles, which tends to increase the VOC removal efficiency. When the shape of amorphous manganese oxide is particulate, it may be an aggregate of particles formed by a large number of one particle (primary particles).

In the VOC catalyst of the present invention, the size of amorphous manganese oxide is not particularly limited. For example, when the amorphous manganese oxide is in the form of particles, the size of the amorphous manganese oxide is preferably 1 to 500 nm, more preferably 5 to 300 nm, assuming that the particles are spherical. preferable. The average particle size of the primary particles referred to here is a value obtained by randomly selecting 50 particles by direct observation of amorphous manganese oxide with a scanning electron microscope, measuring the equivalent circle diameters of these particles, and arithmetically averaging them.

In the VOC catalyst of the present invention, the content ratio of amorphous manganese oxide and rare earth elements is not particularly limited. For example, in the VOC catalyst of the present invention, the rare earth element is preferably contained in an amount of 0.1 to 5% by mass based on the total mass of the amorphous manganese oxide. In this case, the VOC removal efficiency of the VOC catalyst is likely to be further increased. The rare earth element is more preferably contained in an amount of 0.2 to 3% by mass, more preferably 0.3 to 2% by mass, based on the total mass of the amorphous manganese oxide. The content of rare earth elements with respect to amorphous manganese oxide can be analyzed by, for example, energy dispersive X-ray analysis (EDX analysis). The content of the rare earth element can be adjusted by adjusting the charging ratio of the Mn source described later used in the production of the VOC catalyst and the rare earth element source.

The specific surface area of the VOC catalyst of the present invention is not particularly limited, but for example, the specific surface area by the BET method is 100 to 400 m ² / g, preferably 200 to 400 m ² / g, and more preferably 250 to 400 m ² / g.

The VOC catalyst of the present invention may contain elements, compounds, additives and the like other than amorphous manganese oxide and rare earth elements as long as the effects of the present invention are not impaired. Further, the VOC catalyst of the present invention may be formed only of amorphous manganese oxide and rare earth elements. In this case, it is permissible to contain unavoidable elements, components and the like that may be contained in the VOC catalyst.

When the VOC catalyst of the present invention contains other elements and components other than amorphous manganese oxide and rare earth elements, the total content thereof is, for example, 5% by mass or less, preferably 3% by mass, based on the total mass of the VOC catalyst. % Or less, more preferably 1% by mass or less, particularly preferably 0.5% by mass or less or 0.5% by mass.

The VOC catalyst of the present invention is easy to manufacture, can efficiently remove VOCs even at low temperatures, and can be suitably used as a catalyst for removing VOCs.

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 the production method including the steps 1 and 2 described later.

2. Method for Producing VOC Removal Catalyst The method for producing the VOC removal catalyst of the present invention is not particularly limited, but a production method including the following steps 1 and 2 is preferable.
Step 1; A step of obtaining a product by mixing a raw material liquid A containing a manganese source and a raw material liquid B containing a rare earth element source.
Step 2; Step 2 of firing the product obtained in the above step 1.

(Step 1)
In step 1, the raw material liquid A containing the manganese source and the raw material liquid B containing the rare earth element source are mixed.

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

The type of the compound containing manganese is not particularly limited, and examples thereof include various inorganic compounds containing manganese. Examples of the inorganic compound containing manganese include nitrates, sulfates, chlorides, hydrochlorides, chlorates, perchlorates, carbonates, bicarbonates, phosphates and hydrogen phosphates of manganese. be able to.

Further, as the compound containing manganese, various organic compounds containing manganese can be mentioned, and examples thereof include an acetate of manganese, a oxalate, an acid salt and a succinate.

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

It is particularly preferable to use an acetate of manganese as the manganese source in that the production of the VOC catalyst is easy.

In the raw material liquid B containing the rare earth element source used in step 1, the rare earth element source is dissolved or dispersed in the solvent. The rare earth element source may be a rare earth element alone or a compound containing a rare earth element.

The type of the compound containing a rare earth element is not particularly limited, and examples thereof include various inorganic compounds containing a rare earth element. Examples of inorganic compounds containing rare earth elements include nitrates, sulfates, oxides, chlorides, hydrochlorides, chlorates, perchlorates, carbonates, bicarbonates, phosphates and phosphates of rare earth elements. Hydrogen salts and the like can be mentioned.

Further, as the compound containing a rare earth element, various organic compounds containing a rare earth element can be mentioned, and examples thereof include an acetate, a oxalate, an acid salt and a succinate of a rare earth element, a cyclodipentadienyl dichloride salt and the like. be able to.

The compound containing a rare earth element may also contain two or more different anions (for example, ammonium sulfate).

The source of the rare earth element is preferably an inorganic compound containing the rare earth element in that the production of the VOC catalyst is easy, and it is particularly preferable to use the nitrate of the rare earth element in that the reactivity is excellent.

Both the raw material liquid A and the raw material liquid B can contain a solvent. The type of solvent is not particularly limited, and for example, water; alcohols having 1 to 4 carbon atoms such as methanol and ethanol; and mixed solvents thereof; and various other solvents capable of dissolving cerium sources, rare earth element sources, and organic ligands. Organic solvent (for example, an amide solvent such as N, N-dimethylformamide, a pyrrolidone solvent such as N-methylpyrrolidone, etc. can be used). The solvent contained in the raw material liquid A and the raw material liquid B is preferably water, the alcohol, or a mixed solvent thereof, and more preferably water, from the viewpoint that the reaction in the step 1 can easily proceed. The solvents contained in the raw material liquid A and the raw material liquid B may be the same or different from each other, and it is more preferable that both of them are water.

In the raw material liquid A, the concentration of the manganese source is not particularly limited. For example, the concentration of manganese in the raw material solution A, 1 × ¹⁰ -4 to 1 m, preferably 1 × ¹⁰ -3 0.5 m, further preferably be a 1 × ¹⁰ -2 ~0.1M.

In the raw material liquid B, the concentration of the rare earth element source is not particularly limited. For example, the concentration of the rare earth element in the raw material liquid B can be 1 × 10 ^{-4 to} 10 M, preferably 1 × 10 ^{-3 to} 1 M, and more preferably 1 × 10 ^{−2 to} 0.5 M.

In step 1, it is preferable to use an oxidizing agent in performing the mixing treatment of the raw material liquid A and the raw material liquid B. As a result, the oxidation reaction of manganese is likely to occur, and the finally obtained manganese oxide is likely to form an amorphous structure.

The type of the oxidizing agent is not particularly limited, and for example, the oxidizing agent used in the redox reaction can be widely used, and examples thereof include potassium permanganate (KMnO ₄ ).

When the oxidizing agent is used in step 1, the oxidizing agent can be prepared independently of the raw material liquid A and the raw material liquid B, or may be contained in either the raw material liquid A or the raw material liquid B. Further, the raw material liquid A and the raw material liquid B can be included in the mixture obtained by the mixed treatment. The oxidant can also be prepared as a solution. In this case, the solvent can be the same as the solvent that can be used for the solutions A and B. The oxidizing agent is preferably contained in the raw material liquid B from the viewpoint that the reaction can easily proceed.

The amount of the oxidizing agent used is not particularly limited, and for example, the amount used can be the same as that of a general oxidation reaction. For example, if the oxidizing agent is prepared as a solution, the concentration of the oxidizing agent in oxidizing agent solution, 1 × ¹⁰ -4 through 10m, preferably 1 × ¹⁰ -3 to 1 m, more preferably 1 × ^{10 -2} ~ It can be 0.5M.

The method of mixing the raw material liquid A and the raw material liquid B is not particularly limited. For example, a method of preparing a raw material liquid A and a raw material liquid B and adding the other solution to one of them at once and mixing them, and a method of dropping the other solution onto one of the raw material liquid A and the raw material liquid B and mixing them can be mentioned. can. In the case of the dropping method, it is preferable to drop and mix the raw material liquid B containing the oxidizing agent into the raw material liquid A, and in this case, the oxidation reaction of manganese easily proceeds. In this case, the dropping speed and the like are not particularly limited and can be appropriately selected. For example, the dropping rate can be in the range of 0.1 to 50 mL / min.

By mixing the raw material liquid A and the raw material liquid B, the reaction between the manganese source and the rare earth element source proceeds, and a reactant can be obtained. Such reactants are produced, for example, as precipitates. By the reaction between the manganese source and the rare earth element source, for example, when the manganese of the manganese source is divalent, it can become tetravalent manganese.

In the mixing treatment of the raw material liquid A and the raw material liquid B, the temperature at the time of mixing is not particularly limited, and can be, for example, 0 to 50 ° C., preferably 10 to 35 ° C. (that is, near room temperature).

After mixing the raw material liquid A and the raw material liquid B, for example, it can be stirred with a commercially available stirrer or the like. The stirring time after mixing is also not particularly limited and can be appropriately selected in consideration of reactivity, for example, 1 hour or more and 30 hours or less.

The mixing process in step 1 can result in, for example, a black precipitate. This precipitate contains manganese oxide and rare earth element ions. The obtained precipitate can be separated by an appropriate method such as filtration, and washed, dried or the like, if necessary. The precipitate obtained by the mixing treatment is calcined in step 2 described later to become a target VOC removal catalyst. Therefore, the precipitate obtained by the mixing treatment is, so to speak, a precursor of the VOC removal catalyst.

(Step 2)
Step 2 is a step for firing the product obtained in step 1. By such a firing treatment, the desired VOC removal catalyst can be obtained.

In step 2, the firing treatment method is not particularly limited, and a known firing method can be widely adopted. For example, the temperature of the firing process can be 100 ° C. or higher. Further, the temperature of the firing treatment is preferably less than 500 ° C. in that manganese oxide in the VOC catalyst obtained by firing tends to be amorphous. The preferred firing temperature is 250 to 480 ° C, the more preferred firing temperature is 290 to 450 ° C, and the more preferred 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 2, the rate of temperature rise during firing is not particularly limited and can be appropriately set.

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

By the firing treatment in step 2, a sintered body of the product is formed, and this can be obtained as a target VOC removal catalyst. In step 2, the product obtained in step 1 is oxidized to obtain amorphous manganese oxide containing (doped) rare earth elements. The VOC removal catalyst obtained by this firing treatment is a compound (composite oxide) in which a part of Mn in manganese oxide is replaced with a rare earth element.

The VOC removal catalyst of the present invention can exist in a state in which rare earth elements are highly dispersed in amorphous manganese oxide by undergoing the firing in step 2. As a result, the VOC removal catalyst of the present invention can remove VOCs at a lower temperature.

According to the production method including the above steps 1 and 2, the VOC catalyst of the present invention can be easily obtained by a simple step, and the obtained VOC catalyst efficiently removes VOCs even at a low temperature. be able to.

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

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

The type of container used for removing VOCs is not particularly limited, and for example, known containers used for catalytic combustion of VOCs can be widely used. The processing temperature of VOCs in the container is not particularly limited, and can be the same as the processing temperature set for removing known VOCs. In particular, in the present invention, by using the above VOC removal catalyst, the VOC removal efficiency is excellent even at a low temperature.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the aspects of these Examples.

(Example 1)
A VOC removal catalyst was synthesized by the procedure shown in the schematic diagram of FIG. In water 250 mL 3.0625G of _Mn (CH 3 _COO) dissolved 2 · 4H ₂ O and to thereby prepare a liquid raw material A. Further, in water 250 mL KMnO ₄ and 0.0735g of Ho _{(NO 3)} of 1.475g 3 · 6H ₂ O and dissolved by to prepare a raw material solution B. While vigorously stirring the raw material liquid A, the raw material liquid B was dropped onto the raw material liquid A at a supply rate of 10 mL / min by a liquid supply pump, whereby a black precipitate was obtained. The obtained black suspension was further stirred at room temperature (25 ° C.) for 6 hours, then separated by centrifugation and washed several times to obtain a black solid as a product (step 1). The product was dried at 60 ° C. for 6 hours and then heated to 350 ° C. in a muffle furnace at a heating rate of 5 ° C./min in an air atmosphere. This temperature was set as the firing temperature, and the product was fired for 3 hours to obtain a VOC removal catalyst (step 2). In this VOC catalyst, the ratio of Ho to manganese oxide was 0.5% by mass. The specific surface area of the VOC catalyst by the BET method was 260 m ² / g. The obtained VOC removal catalyst was designated as "0.5% Ho-MnOx-350".

(Example 2)
In order to proportion of Ho for Mn (manganese oxide equivalent) and 1 wt% in the raw material solution A and the raw material liquid B, is carried out except for changing the Ho _{(NO 3)} the amount of 3 · 6H ₂ O to 0.147g A VOC removal catalyst was obtained in the same manner as in Example 1. In this VOC catalyst, the ratio of Ho to manganese oxide was 1% by mass. The obtained VOC removal catalyst was designated as "1% Ho-MnOx-350".

(Example 3)
In order to 1.5 mass% the proportion of Ho for Mn (manganese oxide basis) in the raw material solution A and the raw material solution B, except for changing the Ho _{(NO 3)} the amount of 3 · 6H ₂ O to 0.2213g Obtained a VOC removal catalyst in the same manner as in Example 1. In this VOC catalyst, the ratio of Ho to manganese oxide was 1.5% by mass. The obtained VOC removal catalyst was designated as "1.5% Ho-MnOx-350".

(Comparative Example 1)
To obtain a VOC removing catalyst by _{Ho (NO 3) 3 · 6H} 2 O except for not using the Example 1 and the same method. The obtained VOC removal catalyst was designated as "MnOx-350".

(Comparative Example 2)
A VOC removal catalyst was obtained in the same manner as in Example 2 except that the firing temperature was changed to 500 ° C. The obtained VOC removal catalyst was described as "1% Ho-MnOx-500".

(Comparative Example 3)
A binary oxide catalyst was prepared by a direct firing method with reference to a non-patent document (Inorganic Chemistry Frontiers.DOI: 10.1039 / c9qi00039a). Specifically, samarium nitrate (III) hexahydrate _{(Sm (NO 3) 3 ·} 6H 2 O), were mixed manganese acetate tetrahydrate and citric acid, at a rate of 2 ° C. / min in air By raising the temperature to 380 ° C. and maintaining this temperature for 3 hours, manganese oxide containing 2% by mass, 3% by mass, 4% by mass and 5% by mass of Sm was obtained. The specific surface area of the obtained VOC catalyst by the BET method was 98 m ² / g.

<Evaluation method>
(VOC removal test)
The toluene removal test of the VOC removal catalyst obtained in each example was carried out according to the schematic flow shown in FIG. In this test, a VOC removal catalyst was filled in a container so as to be sandwiched between quartz wool, and toluene was allowed to flow into the container at a predetermined flow rate for reaction to remove toluene. As shown in FIG. 2, the container is connected to an oxygen cylinder and a nitrogen cylinder so that oxygen and nitrogen can flow into the container. As a condition of the toluene removal test, a glass reactor having an inner diameter of 8 mm was used, the filling amount of the VOC removal catalyst was 50 mg, and the toluene concentration in the container was 1000 volume ppm. The flow rate of nitrogen gas for carriers into the container was 40 cm ³ / min, the flow rate of nitrogen gas for introducing toluene was 40 mL / min, and the flow rate of oxygen gas was 10 cm ³ / min. The reaction temperature in the vessel was adjusted to various temperatures in the range of 130 to 300 ° C., and the toluene removal property was evaluated. In the range of 130 to 200 ° C, sampling is performed 3 times every 10 ° C, in the range of 200 to 250 ° C, sampling is performed 3 times every 5 ° C, and in the range of 260 to 300 ° C, every 10 ° C. Sampling was done 3 times. The VOC concentration was measured using a "GC-2014 gas chromatograph" manufactured by Shimadzu Corporation. Further, the concentration of carbon dioxide discharged from the outlet of the container was measured using an FT-IR gas analyzer "FG-120" manufactured by HORIBA.

FIG. 3 shows SEM images of the VOC removal catalysts obtained in Examples 1 to 3 and Comparative Examples 1 and 2 (FIG. 3 (a) shows the VOC removal catalyst obtained in Example 1, and FIG. 3 (b) shows the implementation. The VOC removal catalyst obtained in Example 2, (c) is the VOC removal catalyst obtained in Example 3, (d) is the VOC removal catalyst obtained in Comparative Example 1, and (e) is the VOC removal catalyst obtained in Comparative Example 2. ).

From FIG. 3, it was found that in the VOC removal catalysts obtained in each example, aggregates of irregularly shaped nano-sized particles were formed. It was found that the VOC removal catalyst obtained in Comparative Example 1 was composed of aggregates of bamboo leaves such as rods / sheets.

FIG. 4 shows the XRD spectra of the VOC removal catalysts obtained in Examples 1 to 3 and Comparative Examples 1 and 2.

From FIG. 4, it was found that the "MnOx-350" obtained in Comparative Example 1 had a crystal structure by referring to the _{known MnO 2-PDF44-0141.} On the other hand, it can be seen that the VOC removal catalysts obtained in Examples 1 to 3 have an amorphous structure. This indicates that the manganese oxide produced in Examples 1 to 3 changed to an amorphous structure by Ho doping. It can be seen that the VOC catalyst obtained in Comparative Example 2 resulted in the formation of a crystal phase in manganese oxide. It is presumed that this is because it was fired at a high temperature (500 ° C.). From the comparison between "MnOx-350" and "1% Ho-MnOx-350", it can be seen that the apparent peak shift indicates that the Ho species was normally inserted into the Mn lattice.

FIG. 5 shows the results of the VOC removal test using the VOC removal catalysts obtained in Examples 1 to 3 and Comparative Examples 1 and 2. Specifically, FIG. 5 is a plot showing the relationship between the temperature (X-axis) and the toluene removal rate (Y-axis).

_{Table 1 shows the 90% decomposition temperature (T 90%} ) and 100% decomposition temperature (T _100% ) of toluene by the VOC removal catalysts obtained in Examples 1 to 3 and Comparative Examples 1 and 2. ing.

From the results of FIG. 5 and Table 1, it was found that the VOC removal catalysts obtained in each example _{had better VOC removal performance than MnO 2} having a crystal structure (Comparative Example 1), and particularly at a low temperature. Even so, it had excellent VOC removal performance (combustion efficiency). In addition, the VOC removal catalyst obtained in Examples showed superior activity to toluene combustion than the binary oxide catalyst of Comparative Example 3 reported using the direct calcination method. This difference is due to the amorphous manganese oxide doped with rare earth elements (amorphous manganese oxide in which some manganese is replaced with rare earth elements) in the VOC catalyst obtained in the examples, whereas the binary of Comparative Example 3 It is presumed that this is due to the fact that manganese oxide is not amorphous in the oxide catalyst.

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 a typical VOC substance.

Claims (6)

VOC removal catalyst
Contains amorphous manganese oxide,
A VOC removal catalyst in which the amorphous manganese oxide is doped with a rare earth element. The VOC according to claim 1, wherein the rare earth element is at least one selected from the group consisting of La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. Removal catalyst. The VOC removal catalyst according to claim 1 or 2, wherein the rare earth element is contained in an amount of 0.1 to 5% by mass based on the total mass of the amorphous manganese oxide. The method for producing a VOC removal catalyst according to any one of claims 1 to 3.
Step 1 of obtaining a product by mixing a raw material liquid A containing a manganese source and a raw material liquid B containing a rare earth element source.
Step 2 of firing the product obtained in step 1 and
A method for producing a VOC removal catalyst. The production method according to claim 4, wherein the firing temperature in the step 2 is 300 to 400 ° C. A VOC removal method comprising a step of decomposing a VOC using the VOC removal catalyst according to any one of claims 1 to 3 or the VOC catalyst obtained by the production method according to claim 4 or 5. ..

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