JP7337338B2 - Method for producing catalyst for removing VOC and method for removing VOC - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a catalyst for removing VOCs 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.

VOCs are emitted from various processes such as painting (indoors and outdoors), cleaning, lubrication, manufacturing of chemical products, printing, and adhesion. Emissions from sources account for more than 50%.

From this point of view, it is desired to establish a technique for removing VOCs more efficiently in order to further reduce VOC emissions. Various VOC removal methods have been proposed so far. VOC emission countermeasure technologies can be roughly classified into four methods: (1) recovery/regeneration method; (2) sealed method; (3) combustion/decomposition method; and (4) substance substitution method.

The combustion/decomposition method treats VOCs by decomposing them into carbon dioxide, water, and the like. As typified by conventional painting and printing, when multiple VOCs with different substances and component ratios are used, even if the VOCs are recovered and recycled, there is little advantage in reusing them. It can be said that the decomposition method is realistic.

Among the combustion/decomposition methods, the method of decomposing VOCs by combustion has been used since around 1960 in Japan. As combustion methods, for example, a direct combustion method, a catalytic combustion method, and a regenerative combustion method are known. Among them, the catalytic combustion method is a method of oxidatively decomposing VOC at a low temperature of 200 to 350° C. using a catalyst supporting platinum, palladium, or the like. The characteristics of the VOC removal device used in this method are that it can be operated at low temperatures, that it is easy to reduce its size and weight, that it has little risk of explosion, and that it does not generate thermal NOx by-products.

However, with the catalytic combustion method, it is difficult to grasp the degree of deterioration of the catalyst. is being developed. Recently, inexpensive catalysts that do not use expensive noble metals such as platinum have also been proposed (see, for example, Non-Patent Document 1).

Applied Catalysis B: Environmental 104 (2011) 144-150

However, in recent years, in the VOC removal catalyst, in addition to not using expensive precious metals such as platinum, it is desired to have properties that can remove VOCs more efficiently. Manufacture by a simple method was desired. In particular, there has been a strong demand for a VOC removal catalyst that can be produced by a simple method and has excellent VOC removal efficiency even when treated at a low temperature.

The present invention has been made in view of the above, and it is an object of the present invention to provide a VOC removal catalyst that can be produced by a simple method and has excellent VOC removal efficiency even when treated at a low temperature, a method for producing the same, and a VOC removal method. aim.

The inventors of the present invention have made intensive studies to achieve the above objects, and as a result, have found that the above objects can be achieved by, for example, a method using electrodeposition, and have completed the present invention.

Item 1
A method for producing a VOC removal catalyst, comprising the step of subjecting a conductive porous substrate as a cathode to electrodeposition treatment in an aqueous solution containing at least one metal compound.
Item 2
wherein the metal compound is a compound of at least one metal M1 selected from the group consisting of Fe, Co, Ni, Mn, Mo, V, Cu, Zn, W, Ti, Cr, Al, Mg and La. 1. The manufacturing method according to 1.
Item 3
Item 3. The manufacturing method according to Item 1 or 2, wherein the conductive porous substrate is a metal porous substrate or a carbon material porous substrate.
Item 4
A VOC removal catalyst formed by coating a conductive porous substrate with a metal oxide.
Item 4'
A VOC removal catalyst obtained by the production method according to any one of Items 1 to 3.
Item 5
The metal oxide is an oxide of at least one metal M1 selected from the group consisting of Fe, Co, Ce, Ni, Mn, Mo, V, Cu, Zn, W, Ti, Cr, Al, Mg and La. Item 5. The VOC removal catalyst according to item 4, which is a composite oxide.
Item 6
Item 6. The VOC removal catalyst according to Item 4 or 5, wherein the conductive porous substrate is a metal porous substrate or a carbon material porous substrate.
Item 7
Item 4. A method for removing VOCs, comprising a step of removing VOCs using the VOC removal catalyst obtained by the production method according to any one of Items 1 to 3.
Item 8
Item 7. A method for removing VOCs, comprising a step of removing VOCs using the VOC removal catalyst according to any one of Items 4 to 6.

According to the method for producing a VOC removal catalyst of the present invention, a VOC removal catalyst can be produced by a simple method. Excellent removal efficiency.

According to the VOC removal catalyst of the present invention, VOC removal efficiency is excellent even when VOCs are treated at a low temperature.

According to the VOC removal method of the present invention, VOCs can be treated at a low temperature, so this method is suitable for removing VOCs.

FIG. 2 is a schematic diagram showing the manufacturing flow of the VOC removal catalyst obtained in each example. 1 is a schematic diagram showing the flow of an evaluation test method for a VOC removal catalyst obtained in each example. FIG. 1 shows an SEM image of the VOC removal catalyst obtained in Example 1. FIG. 4 shows an SEM image of the VOC removal catalyst obtained in Example 2. FIG. 4 shows an SEM image of the VOC removal catalyst obtained in Example 3. FIG. 4 shows an SEM image of the VOC removal catalyst obtained in Example 4. FIG. 4 shows an SEM image of the VOC removal catalyst obtained in Example 5. FIG. 4 shows an SEM image of the VOC removal catalyst obtained in Example 6. FIG. 4 shows an SEM image of the VOC removal catalyst obtained in Example 7. FIG. The evaluation test results of the VOC removal catalyst obtained in each example are shown, (a) is a graph showing the relationship between temperature and toluene conversion, and (b) is a graph showing the relationship between temperature and carbon dioxide selectivity. is.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail. In this specification, the expressions "contain" and "include" include the concepts of "contain", "include", "substantially consist of" and "consist only of".

1. Method for producing VOC removal catalyst The method for producing the VOC removal catalyst of the present invention comprises a step of subjecting a conductive porous substrate as a cathode to electrodeposition treatment in an aqueous solution containing at least one metal compound. include. Hereinafter, this process is abbreviated as "electrodeposition process".

The production method of the present invention includes an electrodeposition step, so that a VOC removal catalyst can be produced in a simple manner, and by using the obtained VOC removal catalyst, VOCs can be treated at a low temperature. and excellent VOC removal efficiency.

The conductive porous substrate used in the electrodeposition step is a substrate that is conductive and porous, and serves to retain the material having catalytic action for removing VOCs. The conductive porous substrate is formed in a plate-like, linear, rod-like, mesh-like shape, or the like, for example.

The type of the conductive porous substrate is not particularly limited, and a wide range of known substrates can be used as long as the substrate has conductivity and is porous.

The conductive porous substrate is preferably a conductive material having a combustion temperature of 400° C. or higher in air. Among them, the conductive porous substrate is preferably, for example, a metal porous substrate or a carbon material porous substrate. In this case, the VOC removal catalyst can be easily produced, and the obtained VOC removal catalyst is also excellent in VOC removal efficiency. Examples of metal porous substrates include metal foams, and examples of carbon material porous substrates include carbon material foams.

Metal foams include various metal foams such as nickel foams and copper foams. The metal foam may be an alloy foam or a foam containing two or more metals. Examples of carbon material foams include carbon paper foams, carbon fiber foams, activated carbon foams, and the like.

The conductive porous substrate may contain other components as long as the effects of the present invention can be obtained.

A conductive porous substrate can be obtained by a known method, or a commercially available conductive porous substrate can be employed.

In the metal compound used in the electrodeposition step, the type of metal is not particularly limited, and for example, metals used in VOC removal catalysts can be widely applied. Hereinafter, the metal in the metal compound is referred to as "metal M".

As the type of metal M, for example, at least one metal M1 selected from the group consisting of Fe, Co, Ce, Ni, Mn, Mo, V, Cu, Zn, W, Ti, Cr, Al, Mg and La is preferably In this case, the VOC removal catalyst can be easily produced, and the obtained VOC removal catalyst is also excellent in VOC removal efficiency. That is, the metal compound used in the electrodeposition step is at least one selected from the group consisting of Fe, Co, Ce, Ni, Mn, Mo, V, Cu, Zn, W, Ti, Cr, Al, Mg and La. is preferably a compound of the metal M1 of The metal compound used in the electrodeposition step preferably contains at least a Co metal compound.

The type of compound of metal M used in the electrodeposition step is not particularly limited. For example, as the compound of the metal M, a known inorganic acid salt of the metal M, a known organic acid salt of the metal M, a known hydroxide of the metal M, a known halide of the metal M, and the like can be widely used. can. The compound of metal M may be a hydrate.

Examples of the inorganic acid salt of the metal M include one or more selected from the group consisting of nitrates, sulfates, hydrochlorides, carbonates, hydrogen carbonates, phosphates, hydrogen phosphates, etc. of the metal M. .

Examples of the organic acid salt of the metal M include one or more selected from the group consisting of metal M acetate, oxalate, formate, succinate, and the like.

The compound of the metal M used in the electrodeposition step preferably dissolves in water to easily form an aqueous solution. In this case, the VOC removal catalyst can be easily produced. Among them, the compound of the metal M used in the electrodeposition step is preferably a nitrate of the metal M, a sulfate of the metal M, a chloride of the metal M, or the like, and more preferably a nitrate of the metal M. In particular, the compound of the metal M used in the electrodeposition step is preferably a nitrate of the metal M1, a sulfate of the metal M1, a chloride of the metal M1, or the like, and most preferably a nitrate of the metal M1.

The compound of the metal M used in the electrodeposition step may be used singly or in combination of two or more different types. It is preferable to use two or more different compounds of the metal M used in the electrodeposition step in combination so that the resulting VOC removal catalyst tends to be excellent in VOC removal efficiency. When two or more different metal M compounds are used in combination, each metal M compound is preferably the same kind of salt. For example, the compounds of each metal M can all be nitrates.

In the electrodeposition step, when two or more different metal M compounds are used in combination, the proportion of each metal M compound used is not particularly limited. For example, when two kinds of metal M compounds are used in combination, the molar ratio of the metal M of one compound and the metal M of the other compound can be 1:0.1 to 1:20. A ratio of 1 to 1:10 is particularly preferred.

In the electrodeposition step, when two or more different metal M compounds are used in combination, the combination of metals M in each metal M compound is not particularly limited. For example, when two or more different compounds of metals M1 are used in combination in the electrodeposition step, combinations of metals M1 between the compounds include Fe, Co, Ce, Ni, Mn, Mo, V, Cu, Zn, Any combination of two or more of the metals M1 selected from the group consisting of W, Ti, Cr, Al, Mg and La may be selected.

In particular, when two or more different metal M1 compounds are used in combination, the metal M1 of at least one metal M1 compound is preferably cobalt. For example, when two different compounds of metal M are used in combination in the electrodeposition step, and one of the metal compounds is a cobalt compound, the molar ratio of the other metal compound to cobalt is 1: It can be from 0.1 to 1:20, particularly preferably from 1:1 to 1:10. When two different kinds of compounds of metal M are used together, the combination of metals in each compound includes a combination of Co and Ni, a combination of Co and Mn, a combination of Co and Fe, a combination of Co and Cu, and a combination of Co and V. A combination and a combination of Co and Ce can be mentioned. Among them, a combination of Co and Ni, a combination of Co and Mn, and a combination of Co and Ce are particularly preferable from the viewpoint that VOC can be removed at a lower temperature.

The compound of metal M can be obtained by a known production method, or a commercially available compound of metal M can be used.

In the electrodeposition step, an aqueous solution containing at least one compound of said metal M is used. The method for preparing this aqueous solution is not particularly limited, and for example, it can be prepared by mixing at least one compound of the metal M with a solvent. As the solvent, water or a mixture of water and a lower alcohol (eg, an alcohol having 1 to 4 carbon atoms such as methanol and ethanol) can be used, and water is particularly preferred. Various types of water such as distilled water, tap water, industrial water, ion-exchanged water, deionized water, pure water, and electrolyzed water can be used as the water. The solvent may contain pH adjusters, viscosity adjusters, fungicides and the like as long as the effects of the present invention are not impaired.

The concentration of the aqueous solution used in the electrodeposition step is not particularly limited. For example, in the aqueous solution, it is preferable that 1 to 1000 mmol of the metal M (when two or more metals are present, each of the metals M) is dissolved per 100 mL of the solvent. In this case, a structurally stable catalyst can be easily formed. In the aqueous solution, 1 to 500 mmol of the metal M (when two or more metals are present, each of the metals M) is dissolved per 100 mL of the solvent, more preferably 5 to 100 mmol is dissolved. preferable.

The aqueous solution used in the electrodeposition step may contain other additives as long as the effects of the present invention are not impaired. Other additives include, for example, pH adjusters.

In the electrodeposition step, the method of electrodeposition treatment is not particularly limited, and a wide range of known electrodeposition methods can be employed. For example, electrodeposition treatment can be performed by immersing the conductive porous substrate in the aqueous solution.

In the production method of the present invention, in the electrodeposition step, electrodeposition is performed using the conductive porous substrate as a cathode .

Various electrodeposition methods can be employed in the electrodeposition treatment. Electrodeposition methods include constant current method (GM), constant voltage method (PM), cyclic voltammetry method (CV), pulse electrodeposition method and the like. The pulse electrodeposition method is an electrodeposition method that can control the electrodeposition speed of metal ions. A pulse current method (PGM) in which a current is applied at a constant cycle, and a unipolar pulse voltage method (UPED) in which a high end voltage and an open circuit state are repeatedly applied at a constant cycle.

The electrodeposition method is preferably a pulse electrodeposition treatment method, and more preferably a unipolar pulse voltage method (UPED).

When the unipolar pulse voltage method (UPED) is employed as the electrodeposition method in the electrodeposition treatment, the conditions for the unipolar pulse voltage method are not particularly limited. For example, the unipolar pulse voltage method can be performed under the conditions of −0.6 to 1.8 V as applied voltage, 0.5 to 1 second in pulse on/off time, and 100 to 1000 cycles. As a typical example, a unipolar pulse voltage method can be performed under the conditions that the applied voltage is −1 V and the ON/OFF time is 1 s.

The temperature of the aqueous solution during the electrodeposition treatment is not particularly limited, and can be, for example, about 0 to 50°C, preferably 20 to 30°C.

In the electrodeposition process, the electrodeposition process can use cathodes , anodes , reference electrodes, electrolytic devices, power sources, control software, and the like. These types are not particularly limited, and known ones can be used depending on the purpose. For example, as a reference electrode, a silver/silver chloride electrode (Ag/AgCl electrode), a mercury/mercury chloride electrode (Hg/ _HgCl2 electrode), a standard hydrogen electrode, or the like can be used.

A known insoluble electrode, for example, can be used as the anode used in the electrodeposition treatment. As the anode , for example, an electrode made of carbon, platinum group metal, gold, or the like can be used. Platinum group metals include platinum, palladium, ruthenium, rhodium, osmium, and iridium, with platinum being preferred. The platinum group metal contained in the anode may contain one kind of the above-described metal species alone or two or more kinds thereof. Also, the platinum group metal may be contained in the form of an alloy, metal oxide, or the like.

The shape of the anode is not particularly limited, and can be appropriately selected depending on the purpose of use and required performance. Examples of shapes include metal wire, sheet, plate, rod, and mesh. Specifically, a spiral platinum wire, a platinum plate, and the like can be exemplified.

In the electrodeposition treatment, the pH of the aqueous solution is not particularly limited, and is, for example, less than 6, preferably about 2-5, more preferably about 3-4.

The electrodeposition process forms a hydroxide of metal M on the conductive porous substrate. When two or more metal M compounds are used in the electrodeposition process, a double hydroxide of metal M is formed on the conductive porous substrate.

A conductive porous substrate electrodeposited in the electrodeposition step can be subjected to a sintering treatment. As a result, the hydroxide or double hydroxide on the conductive porous substrate is calcined and changed to an oxide. If a double hydroxide is formed on the conductive porous substrate, it can be converted into a composite oxide by firing.

That is, the production method of the present invention can include a step of baking the conductive porous substrate that has been electrodeposited in the electrodeposition step after the electrodeposition step. Hereinafter, this step is abbreviated as a firing step.

In the calcination step, the method of calcination treatment is not particularly limited, and a wide range of known calcination methods can be employed. For example, the temperature of the firing treatment can be 100°C or higher, preferably 150 to 450°C, more preferably 200 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 1, the rate of temperature increase during firing is not particularly limited, either, and can be appropriately set to the extent that a desired oxide is formed.

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.

If necessary, the conductive porous substrate that has been electrodeposited in the electrodeposition step can be dried at 50° C. to 150° C. in the air before the firing treatment.

By the firing treatment, the metal hydroxide or double hydroxide on the conductive porous substrate changes to an oxide or composite oxide, and the conductive porous substrate is a metal oxide or composite oxide. coated with

In the production method of the present invention, by including the electrodeposition step, the synthesis time can be shortened compared to the conventional chemical synthesis method. In the conventional chemical synthesis method, the reaction time was long and the reaction temperature had to be high, and washing was required after the reaction. The reaction time is short, and washing after the reaction is not necessarily required.

In addition, in the production method of the present invention, the post-synthesis granulation step that is required in the conventional chemical synthesis method is not required, so that the overall production time is also shortened compared to the conventional method, and the obtained product can be used as it is as a VOC removal catalyst.

Furthermore, in the production method of the present invention, by including the electrodeposition step, the metal oxide or metal composite oxide can be easily distributed uniformly on the carrier (conductive porous substrate), thereby eliminating the need for conventional chemical VOCs can be efficiently removed with a smaller usage amount than the catalyst obtained by the synthetic method.

2. VOC Removal Catalyst The VOC removal catalyst of the present invention is formed by coating a conductive porous substrate with a metal oxide. Such a VOC removal catalyst can be obtained, for example, by the method for producing a VOC removal catalyst of the present invention described above.

The type of conductive porous substrate is the same as the conductive porous substrate used in the production method of the present invention. Therefore, as the conductive porous substrate, various metal foams such as nickel foams or copper foams; carbon material foams such as carbon paper foams, carbon fiber foams and activated carbon foams; body can be mentioned.

The metal oxide in the conductive porous substrate is the oxide of the metal M described above. The metal oxide can contain two or more kinds of metal M. Metal M is preferably at least one metal M1 selected from the group consisting of Fe, Co, Ce, Ni, Mn, Mo, V, Cu, Zn, W, Ti, Cr, Al, Mg and La. . In particular, the metal M preferably contains Co, and in this case, the VOC removal catalyst is particularly excellent in VOC removal efficiency.

The shape of the metal oxide in the conductive porous substrate is not particularly limited. For example, the metal oxide is formed in any shape such as petal-shaped particles, spherical particles, and porous particles.

By having the above structure, the VOC removal catalyst of the present invention has excellent VOC removal efficiency even when VOCs are treated at a low temperature. More efficiency.

Furthermore, in the VOC removal catalyst of the present invention, the metal oxide or metal composite oxide tends to be uniformly distributed on the carrier (conductive porous substrate). VOCs can be efficiently removed with less usage. In particular, when the VOC removal catalyst is obtained by the production method of the present invention, the metal oxide or metal composite oxide is more easily distributed on the carrier, and the VOC removal efficiency is further enhanced.

3. VOC Removal Method The VOC removal method of the present invention comprises a step of removing VOCs using the VOC removal catalyst obtained by the production method of the present invention. Alternatively, the VOC removal method of the present invention comprises the step of removing VOCs using the VOC removal catalyst of the present invention.

For example, the VOC removal catalyst of the present invention is placed in a container, 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. The type of container is not particularly limited, 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, the VOC removal efficiency is excellent even at low temperatures, so VOCs can be treated at, for example, 350° C. or less.

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)
A VOC removal catalyst was produced according to the production flow shown in FIG. First, Co( _{NO 3} ) 2.6H ₂ O and Ni(NO ₃ ) _{2.6H 2} O were mixed at a molar ratio of Co:Ni=1:1 and the concentration of each metal was 0.1 mol. 100 mL of an aqueous solution was prepared so as to be 1/L (only water was used as the solvent). A nickel foam (1.5 cm×1.5 cm each, manufactured by MTI, Japan), which is a conductive porous substrate, was immersed in this aqueous solution as a cathode , and electrodeposition treatment was performed by a unipolar pulse voltage method. In the unipolar pulse voltage method, the applied voltage was set to -1 V, the pulse ON/OFF time was set to 1 second, and the number of cycles was 500 times. A platinum electrode was used as an anode (counter electrode) and Ag/AgCl ₂ as a reference electrode. This electrodeposition treatment formed a double hydroxide of Co and Ni on the conductive porous substrate. The conductive porous substrate thus electrodeposited is dried in an atmosphere of 100° C. overnight, and then the conductive porous substrate is dried in the air at 350° C. for 2 hours. calcined. As a result, a conductive porous substrate coated with a composite of Co and Ni was obtained as a VOC removal catalyst.

(Example 2)
Same as Example 1 except that Mn(NO ₃ ) _{2.6H 2} O was used instead of Ni(NO ₃ ) _{2.6H 2} O and the molar ratio of Co and Mn was Co:Mn=1:1. A VOC removal catalyst was obtained by the method of

(Example 3)
Same as Example 1 except that Fe(NO _{3 )} 3.9H ₂ O was used instead of Ni(NO ₃ ) _{2.6H 2} O and the molar ratio of Co and Fen was Co:Fe=10:1. A VOC removal catalyst was obtained by the method of

(Example 4)
Same as Example 1 except that Cu(NO ₃ ) _{2.3H 2} O was used instead of Ni(NO ₃ ) _{2.6H 2} O and the molar ratio of Co and Cu was Co:Cu=2:1. A VOC removal catalyst was obtained by the method of

(Example 5)
VOC removal was performed in the same manner as in Example 1 except that NH ₄ VO ₃ was used instead of Ni(NO ₃ ) ₂ 6H ₂ O and the molar ratio of Co and V was Co:V = 10:1. A catalyst was obtained.

(Example 6)
Same as Example 1 except that Ce(NO ₃ ) _{3.6H 2} O was used instead of Ni(NO ₃ ) _{2.6H 2} O and the molar ratio of Co and Ce was Co:Ce=10:1. A VOC removal catalyst was obtained by the method of

(Example 7)
A VOC removal catalyst was obtained in the same manner as in Example 1, except that Ni(NO ₃ ) _{2.6H 2} O was not used.

<Evaluation method>
(SEM measurement)
Observation of SEM (scanning electron microscope) images was performed using "Scanning Electron Microscope SU8010" manufactured by Hitachi High-Technologies Corporation.

(Elemental analysis)
The elemental analysis of the VOC removal catalyst was performed using an "energy dispersive X-ray spectrometer" manufactured by HORIBA.

(VOC removal test)
According to the schematic flow shown in FIG. 2, the VOC removal catalyst obtained in each example was subjected to a toluene removal test. 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 and reacted to remove 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 100 mg of VOC removal catalyst was filled therein so that the toluene concentration in the container was 881 to 964 ppm by volume. Further, the carrier nitrogen gas flow rate into the container was set at 35 mL/min, the toluene introduction nitrogen gas flow rate was set at 5 mL/min, and the oxygen gas flow rate was set at 10 mL/min. Toluene removal properties were evaluated by adjusting the reaction temperature in the vessel to various temperatures ranging from 100 to 350°C. 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.

(Evaluation results)
3-9 show SEM images of the VOC removal catalysts obtained in Examples 1-7, respectively. A partially enlarged image (within a broken line) is inserted in each of the SEM images of FIGS. 3 to 8, and FIG. 9B shows the enlarged image of (a).

From FIGS. 3 to 9, it can be seen that the VOC removal catalysts obtained in Examples 1 to 7 have a uniform porous metal oxide coating on a nickel foam substrate. It has been found that, depending on the composition of the oxide, it can take various shapes (for example, flower petals, spherical particles, porous particles).

Table 1 shows the results of elemental analysis by EDS of the VOC removal catalysts obtained in Examples 1-7.

From Table 1, it was found that the VOC removal catalysts obtained in Examples 1 to 7 had the desired oxide or composite oxide formed on the nickel foam substrate.

FIG. 10 shows the results of VOC removal tests using the VOC removal catalysts obtained in Examples 1-7. FIG. 10(a) is a plot showing the relationship between temperature (X-axis) and toluene removal rate (Y-axis), and FIG. 10(b) is a plot showing the relationship between temperature (X-axis) and carbon dioxide selectivity (Y-axis). It is a plot showing the relationship.

From the results of FIG. 10, it was found that toluene can be removed by using the VOC removal catalysts obtained in Examples 1 to 7 as catalysts for catalytic combustion of toluene, which is a typical VOC substance. In particular, the VOC removal catalyst (Co-Ce/nickel foam) obtained in Example 6 exhibited the highest catalytic performance among the examples, and was found to be able to completely remove about 950 ppm of toluene at 280°C. Even other VOC removal catalysts had the ability to remove about 900 ppm of toluene at a temperature of 350° C. or less.

Table 2 shows the results of VOC removal tests using the VOC removal catalysts obtained in Examples 1-7.

As shown in Table 2, when using any of the VOC removal catalysts, the amount of CO ₂ produced corresponding to the amount of toluene introduced and within the error range was observed. From this result, it was found that all of the toluene was converted to CO ₂ and no CO or the like was produced as a by-product.

Table 3 shows a comparison of the VOC removal test results of the VOC removal catalysts obtained in Examples 1 to 6 and the VOC removal catalyst described in Non-Patent Document 1 above. For example, when the Co—Mn composite oxide disclosed in Non-Patent Document 1 was used as a catalyst, the complete combustion temperature of toluene was 360° C. even when the amount of catalyst was 200 mg. For the example VOC removal catalyst, the complete combustion temperature of toluene was less than 360° C. at a catalyst amount of 100 mg. Therefore, it can be said that the VOC removal catalyst of the present invention can completely burn VOCs at a lower temperature even if the amount used is smaller than that of the conventional catalyst.

Claims (3)

Using a conductive porous substrate as a cathode, performing pulse electrodeposition treatment by a unipolar pulse voltage method in an aqueous solution containing at least two kinds of metal compounds,
The metal compound is a compound containing Co and Ni, a compound containing Co and Mn, or a compound containing Co and Ce . The manufacturing method according to claim 1, wherein the conductive porous substrate is a metal porous substrate or a carbon material porous substrate. A step of removing VOCs using the VOC removal catalyst obtained by the production method according to claim 1 or 2,
The VOC removal catalyst is
Using a conductive porous substrate as a cathode, it is manufactured by a step of performing pulse electrodeposition treatment by a unipolar pulse voltage method in an aqueous solution containing at least two kinds of metal compounds,
The method for removing VOCs, wherein the metal compound is a compound containing Co and Ni, a compound containing Co and Mn, or a compound containing Co and Ce .

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