KR102283644B1 - Zeolite based bimetallic catalyst for ozone-catalytic oxidation of volatile organic compounds and oxidation method of volatile organic compounds using the same - Google Patents

Abstract

The present invention relates to a zeolite-based bimetal catalyst for ozone-catalytic oxidation of volatile organic compounds (VOCs) and a method for oxidizing VOCs using the same. Specifically, the present invention relates to a novel catalyst which develops an optimal bimetal catalyst for ozone-catalytic oxidation of VOCs, and supports the same on zeolite, and a method for removing VOCs through oxidation by using the same.

Description

Zeolite based bimetallic catalyst for ozone-catalytic oxidation of volatile organic compounds and oxidation method of volatile organic compounds using the same

The present invention relates to a zeolite-based bimetal catalyst for ozone-catalyzed oxidation of VOCs and a method for oxidizing VOCs using the same. Specifically, it relates to a novel catalyst supporting the development of an optimal bimetallic catalyst for ozone-catalyzed oxidation of VOCs on zeolite, and a method for removing VOCs through oxidation using the same.

Volatile Organic Compounds (hereinafter 'VOCs') volatilize easily at normal pressure and room temperature due to high vapor pressure. VOCs act as precursors of photochemical oxides, increasing ozone and generating photochemical smog. VOCs also contribute to the destruction of the ozone layer and are substances directly involved in global warming (refer to Non-Patent Document 1).

Certain components of VOCs cause irritating and unpleasant odors. As a substance that irritates the skin including the eyes, nose and throat, induces a headache, causes an allergic reaction, and even cancer, it has a direct or indirect effect on the human body (see Non-Patent Document 2).

VOCs are generated on a large scale in printing facilities, painting facilities, petroleum refining and petrochemical manufacturing facilities, and in addition, they are emitted from industries such as automobiles, gas stations, laundries, and publishing facilities (see Non-Patent Document 3). Unlike other facilities, printing facilities are often located in residential or commercial areas. In order to reduce the damage to VOCs, it is necessary to treat them in the area where the VOCs are emitted into the atmosphere.

VOCs treatment techniques include direct combustion (see Non-Patent Document 4), an adsorption method (see Non-Patent Document 5), a plasma-catalyzed method (see Non-Patent Document 6), a catalytic oxidation method (see Non-Patent Document 7), and an ozone-catalyzed oxidation method (see Non-Patent Document 7). There are various techniques such as non-patent document 8), biodegradation (refer to non-patent document 9), and photocatalytic oxidation (refer to non-patent document 10). Among them, ozone-catalyzed oxidation is _{a technology that converts VOCs into CO 2} and H ₂ O using ozone and a catalyst, and has recently been spotlighted as a technology capable of oxidizing VOCs at low temperatures (see Non-Patent Document 11). It is known that ozone-catalyzed oxidation requires about twice the temperature required for complete oxidation than catalytic oxidation (refer to Non-Patent Document 12). In addition, ozone used for ozone-catalyzed oxidation is a strong oxidizing agent, and ozone is decomposed by a catalyst to form active oxygen species, which is effective in oxidizing VOCs (see Non-Patent Document 13).

However, in ozone-catalyzed oxidation, it is important to select and apply an appropriate catalyst. As factors affecting ozone-catalyzed oxidation, the catalyst support and dispersion of the supported active metal are important. As the catalyst support, γ-Al ₂ O ₃ having a large surface area (see Non-Patent Document 14), zeolite (see Non-Patent Document 15) and activated carbon (see Non-Patent Document 16) are mainly used. Precious metals and transition metals are mainly used as active metals. It has been reported that noble metals such as Pt, Pd, and Ag and transition metals of Co, Mn, Fe, and Cu are effective in ozone catalysis (see Non-Patent Documents 17 and 18). In particular, among transition metals, Mn is one of the most efficient catalysts in ozone-catalyzed oxidation. It has been reported that Mn has a good ability to decompose ozone and contributes to oxidation of VOCs even at low temperatures by forming reactive oxygen species (see Non-Patent Document 19). Ozone to remove VOCs such as formaldehyde, benzene, toluene, and cyclohexane Many studies using a catalytic oxidation method are in progress (refer to Non-Patent Documents 20 to 23).

The ozone-catalyzed oxidation reaction at room temperature has a problem in that catalyst deactivation proceeds rapidly due to the formation of intermediates (formic acid, carboxylates, etc.), and incomplete oxides are discharged as they are (see Non-Patent Document 24). In addition, there is also a problem that the selectivity of non-toxic products (CO, CO ₂ ) is low (see Non-Patent Document 25). In order to solve this problem, it is important to develop an efficient catalyst by selecting an appropriate support and active metal.

It has been reported that zeolite as a support has good adsorption capacity for VOCs, and can oxidize and remove VOCs by interacting with ozone (see Non-Patent Document 26). Studies on the oxidation of toluene using Ag/ZSM-5 and Mn/13x in ozone-catalyzed oxidation have been conducted and reported to be effective in toluene oxidation (refer to Non-Patent Documents 27 and 28). In addition, the type of active metal as well as the support is an important factor in ozone-catalyzed oxidation. A method using a catalyst supporting both a noble metal catalyst and a transition metal is attracting attention. It has been reported that the bimetal catalyst has a synergistic effect on the activity of removing VOCs (see Non-Patent Document 29). In Non-Patent Document 30, the _{benzene oxidation reaction was carried out at a low temperature using a catalyst of Mn-Ce/r-Al 2} O ₃ , and in Non-Patent Document 31, the toluene oxidation reaction was evaluated using a Cu-Mn/MCM-41 catalyst. (see Non-Patent Documents 30 and 31). In addition, it has been reported that the reaction at room temperature is effective in oxidizing benzene using an Ag-Mn/ZSM-5 catalyst (see Non-Patent Document 27).

However, depending on the type of VOCs, the catalyst activity is different, and the oxidation capacity of the VOCs is different depending on the type of support. Since their effects are unpredictable, it is necessary to continue to improve catalysts suitable for target VOCs, and it is urgent to develop individual catalysts with excellent properties for the development of catalysts combining them in the future. Although many studies have been conducted to remove VOCs using bimetal, in particular, studies on toluene ozone-catalyzed oxidation using a bimetal catalyst at room temperature are still insignificant.

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In order to solve the above problems, the present invention intends to select a bimetal catalyst capable of removing VOCs even at room temperature. In particular, an object of the present invention is to develop a combination of a bimetallic catalyst and a suitable zeolite support for obtaining a high toluene removal rate and carbon selectivity.

In the present invention, in order to solve the above problems, the catalyst was selected by checking the physical and chemical properties of the bimetal catalyst. In addition, in order to obtain high toluene removal rate and carbon selectivity, toluene ozone catalytic oxidation reaction using various types of zeolites was performed to develop a combination with a suitable support.

The present invention provides an M1-M2 bimetal catalyst for room temperature ozone-catalyzed oxidation of volatile organic compounds. Here, M1 is one selected from the group consisting of Ru, Fe, Cu, and Ag, and M2 is Mn.

The M1-M2 bimetal catalyst is supported on zeolite, and the zeolite is ZSM-5 (SiO ₂ /Al ₂ O ₃ ) (23), ZSM-5 (SiO ₂ /Al ₂ O ₃ ) (80), ZSM- 5(SiO ₂ /Al ₂ O ₃ ) (280), Y(SiO ₂ /Al ₂ O ₃ ) (5.1), Y(SiO ₂ /Al ₂ O ₃ ) (80) is at least one selected from the group consisting of .

A preferred example of the M1-M2 bimetallic catalyst is Ru-Mn, and a preferred example of the zeolite is ZSM-5 (SiO ₂ /Al ₂ O ₃ ) (80).

The volatile organic compound is at least one selected from the group consisting of trimethylbenzene, nonane, methyl ethyl ketone, isopropyl alcohol, formaldehyde, benzene, toluene, and cyclohexane. Specifically, the volatile organic compound is toluene.

The present invention provides a method for ozone-catalyzed oxidation of volatile organic compounds at room temperature using the bimetal catalyst. At this time, ozone may be separately supplied, and the room temperature is 10 degrees Celsius to 35 degrees Celsius.

The present invention also provides an apparatus for ozone-catalyzed oxidation of volatile organic compounds at room temperature using the bimetal catalyst, wherein a line for separately supplying ozone may be added.

The present invention can also provide the above problem solving means by overlapping or combining.

In the present invention, in order to solve the above problems, the catalyst was selected by checking the physical and chemical properties of the bimetal catalyst. In addition, in order to obtain high toluene removal rate and carbon selectivity, toluene ozone catalytic oxidation reaction using various types of zeolites was performed to develop a combination with a suitable support.

In the present invention, in order to select a bimetal capable of removing VOCs even at room temperature, a bimetal catalyst was studied through physical and chemical properties. First, in order to select an optimal bimetal, a study was conducted by supporting the metal on _{ZSM-5 (SiO 2} /Al ₂ O _{3 =280).} The single metal catalyst Mn/ZSM-5 and the bimetal catalyst Ru-Mn/ZSM-5, Fe-Mn/ZSM-5, Cu-Mn/ZSM-5, and Ag-Mn/ZSM-5 were compared. Among the catalysts, Ru-Mn/ZSM-5(280) had the highest reducing ability ^{, and through the molar ratio of Mn 3+} /(Mn ³⁺ +Mn ⁴⁺ ) and Ovacancy/Olattice, it oxidized and ozone toluene at room temperature. Since it exhibits higher activity than other catalysts in decomposing the metal, it was selected as the optimal bimetal.

In order to select a zeolite support suitable for the toluene ozone catalytic oxidation reaction, the selected bimetal was supported on a zeolite having a different Si/Al ratio. Ru-Mn/ZSM-5 (SiO ₂ /Al ₂ O ₃ =23, 80, 280) and Ru-Mn/Y (SiO2/Al2O3 =5.1, 80) were compared. The greater the specific surface area and pore volume of the catalyst, the higher the efficiency in oxidizing toluene, and the zeolite catalyst with a Si/Al ratio of 80 had the highest efficiency. In the case of long-term test, Ru-Mn/ZSM-5 (SiO ₂ /Al ₂ O ₃ =80) showed the highest toluene removal rate of 41% and ozone removal rate of 43% after 420 minutes of reaction, and the carbon balance (45 %) and CO ₂ selectivity (34%). However, the generation of intermediate by-products occurred and the generated intermediate by-products were deposited on the catalyst surface, causing deactivation of the catalyst. As a result, it has low toluene removal efficiency and low carbon balance and CO ₂ selectivity.

1 is a schematic diagram of a sample preparation and catalyst loading process according to an embodiment of the present invention.
2 is a schematic diagram of an ozone-catalyzed oxidation reaction apparatus according to an embodiment of the present invention.
3 is an XRD pattern of ZSM-5, a single metal catalyst, Mn/ZSM-5, and a bimetal catalyst, M(M = Fe, Cu, Ru, Ag)-Mn/ZSM-5 according to the present invention.
4 is a spectra of Mn 2p of a single metal catalyst and a bimetal catalyst according to the present invention.
5 is a spectra of O 1s of a single metal catalyst and a bimetal catalyst according to the present invention.
_{6 shows H 2} -TPR results of a single metal catalyst and a bimetal according to the present invention.
7 and 8 respectively show the toluene removal rate and ozone removal rate and the amount of _{CO x generated according to the concentration of ozone according to the present invention.}
9 shows the toluene removal rate and ozone removal rate after 2 hours of room temperature reaction according to the present invention.
Figure 10 shows the amount of _{CO x} production after 2 hours of room temperature reaction according to the present invention.
11 shows a GC/MS chromatogram according to the present invention.
12 shows the toluene removal rate and ozone removal rate after 2 hours of room temperature reaction of each catalyst according to the present invention.
13 shows the amount of _{CO x} production after 2 hours of room temperature reaction according to the present invention.
_{FIG. 14 shows toluene and ozone removal rates and CO and CO 2} production amounts according to time of the room temperature ozone-catalyzed oxidation reaction using Ru-Mn/ZSM-5 (SiO ₂ /Al ₂ O ₃ =80) according to the present invention.
_{15 shows the toluene and ozone removal rates and the amount of CO and CO 2} production according to time of the room temperature ozone-catalyzed oxidation reaction using Ru-Mn/Y (SiO ₂ /Al ₂ O ₃ =80) according to the present invention.
_{16 shows the carbon balance (%) and CO 2} selectivity (%) according to time of the room temperature ozone-catalyzed oxidation reaction using Ru-Mn/Y (80) and Ru-Mn/ZSM-5 (80).

Hereinafter, embodiments in which those of ordinary skill in the art to which the present invention pertains can easily practice the present invention will be described in detail with reference to the accompanying drawings. However, in the detailed description of the principle of operation of the preferred embodiment of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In addition, the same reference numerals are used throughout the drawings for parts having similar functions and functions. Throughout the specification, when it is said that a part is connected to another part, it includes not only a case in which it is directly connected, but also a case in which it is indirectly connected with another element interposed therebetween. In addition, the inclusion of a certain component does not exclude other components unless otherwise stated, but means that other components may be further included.

Hereinafter, the present invention will be described in more detail.

<Sample preparation and catalyst loading>

As supports, zeolite catalysts ZSM-5 (SiO ₂ /Al ₂ O ₃ = 23, 80, 280, Zeolyst, USA) and Y (SiO ₂ /Al ₂ O ₃ =5.1, 80, Zeolyst, USA) were used. A single metal catalyst Mn/Zeolite and a bimetal catalyst M(M=Cu, Fe, Ag, Ru)-Mn/Zeolite catalyst were prepared by supporting a metal on a support using the incipient wetness impregnation method. The prepared process is shown in FIG. 1 . Manganese acetate tetrahydrate ((CH ₃ COO) ₂ Mn·4H ₂ 0, Sigma-Aldrich, USA) was used as a precursor to support Mn, and the loading amount was fixed at 5 wt%. After supporting manganese, Silver acetate (CH ₃ COOAg, Sigma-Aldrich, USA), Copper(II) nitrate trihydrate (CuN ₂ O ₆ 3H ₂ O, Sigma-Aldrich, USA), Ruthenium(III) chloride hydrate (Cl ₃ Ru·xH ₂ O), Sigma-Aldrich, USA), and Iron(II) nitrate nonhydrate (FeN ₂ O ₉ 9H ₂ O, Sigma-Aldrich, USA) were each used as metal precursors, and the amount of bimetal supported was It was fixed at 1 wt%. Each of the precursors was dissolved in distilled water and then impregnated into the support. After drying the impregnated catalyst for 12 hours, it was calcined at 350° C. for 2 hours. After calcination, the catalyst was used after being molded into pellets having a size of 1.0 to 1.7 mm.

<Characteristic analysis method>

BET (Brunaure-Emmett-Teller)

In order to confirm the characteristics of the specific surface area and pore volume of the catalyst, it was pre-treated at 300°C for 12 hours and then measured using an analysis device, Belsrop mini II (BEL JAPAN, INC., Japan). _{After measuring the amount of adsorbed nitrogen gas by adsorbing N 2} on the surface of the powder, the specific surface area was calculated by the BET equation. The calculation formula is shown below.

Here, each variable is as follows.

P/P ₀ : Relative Pressure

V : Weight of gas adsorbed at a P/P ₀

V _m : Weight of adsorbate constituting a monolayer of θ

C : BET C constant, related with h eat of adsorption

(50-250 on most of solid surfaces)

XRD (X-ray diffraction)

In order to confirm the structural characteristics of the catalyst, it was measured using an analysis device, Ultima III (Rigaku, JAPAN). It was measured using Cu Kα X-ray, and the scan range was 0 to 80°, and the step size was 0.02°.

XPS (X-ray photoelectron spectra)

In order to measure the chemical bonding state of the catalyst surface, the type of element present on the surface, and the chemical state, it was measured using a measuring instrument, MultiLab2000 (VG, UK). The short wavelength Al Kα X-rays (1486.6 eV) and 40 eV were characterized by using ^{vacuum (5.2 × 10 -9 Torr).} After the C1s peak was corrected to 285 eV, a binding energy value was obtained.

H ₂ -TPR (Temperature-Programmed Reduction)

In order to confirm the reduction temperature of the catalyst, it was measured using an analysis device, BEL-CAT (BEL JAPAN, INC., Japan). After pre-treatment with N ₂ at 300° C. for 1 hour _{, heating at 10° C./min using a He/H 2} mixed gas (30 ml/min), the reduction temperature was confirmed by measuring the consumption of _{H 2 .}

<Ozone Catalytic Oxidation Experiment Method and Apparatus>

A toluene cylinder with a nitrogen balance of 200 ppm was used, and the inflow flow rate was adjusted to the concentration of toluene through a Mass Flow Controller (K.M.B. Tech Co., South Korea). After oxygen was generated by supplying oxygen to an ozone generator (Ozonetech, South Korea), the inflow flow rate was adjusted to the ozone concentration through a Mass Flow Controller (K.M.B. Tech Co., South Korea). The initial concentration of toluene was 100 ppm, and the flow rate of toluene was maintained at 1 L/min. The ozone concentration was 1000 ppm, and the ozone flow rate was maintained at 1 L/min. The total flow rate was maintained at 2L/min, and the mixture was mixed in a mixing chamber, and then a catalytic reaction experiment was performed. The catalyst layer was made of 1/2 inch SUS material. 1.5 g of catalyst (1.0 to 1.7 mm) in the form of pellets was charged to the catalyst bed. All ozone-catalyzed reaction experiments were conducted at room temperature. A schematic diagram of the reaction apparatus is shown in FIG. 2 .

After passing the mixed gas through the catalyst layer, _{the concentrations of gas products and toluene, CO, and CO 2} were measured by Fourier transform infrared spectroscopy (FT-IR) combined with a gas cell (Nicolet 10M Gas cell, Thermo Fisher Scientific.) The ozone concentration was checked with an ozone analyzer (Ozonetech, South Korea) operated by UV absorption.

GC (7280A, Agilent, USA)/MS (5977E, Agilent, USA) attached with a tandem μ-reactor (PY-2020iD, Prontier Laboratories, Japan) was used to check the type of by-product adsorbed by the catalyst after the reaction experiment. was used to confirm. After the catalyst was placed in a 10 mg sample cup, the sample cup was dropped into a tandem μ-reactor with a temperature of 300° C. and reacted for 2 minutes. After the reaction, the vaporized product was moved to a column (Ultra Alloy-5, Frontier Laboratories, Japan) through the GC inlet, and the spilt ratio was 20:1. The oven program was maintained at 50° C. for 2 minutes, then heated to 200° C. at a temperature increase rate of 30° C./min, and then maintained for 5 minutes. MS peak materials were identified with the NIST 05 Library (National Institute of Standards and Technology, USA).

<Characteristics analysis>

BET (Brunaure-Emmett-Teller)

Table 1 shows the specific surface area of Mn/ZSM-5 (SiO ₂ /Al ₂ O ₃ =280) and M(M= Fe, Cu, Ru, Ag)/ZSM-5 (SiO ₂ /Al ₂ O ₃ =280) and pore volume. The specific surface area of Mn/ZSM-5 is 365 m ³ /g, which has the largest specific surface area, and the pore volume also has the largest value. In the case of a bimetal catalyst in which metals (Fe, Cu, Ru, Ag) are added to Mn/ZSM-5, 364. 359, 358, and 357 m ³ /g specific surface areas are respectively shown. In the case of the bimetallic catalyst, it can be seen that the specific surface area of the bimetallic catalyst is decreased when the specific surface area of the single metal catalyst is compared. The pore volume of the bimetallic catalyst has a value in the range of 0.21-0.22cm ³ / g, it can be seen that having a pore volume the value lower than a single metal catalyst (0.23cm ³ / g). It can be seen that this was reduced by additional metal loading on the single metal catalyst. Specific surface area and pore volume are factors affecting the adsorption of VOCs. It can be seen that the difference between the specific surface area of the bimetal and the value of the pore volume is insignificant. In this experiment, it can be expected that the specific surface area and pore volume of the bimetal will not affect toluene oxidation.

XRD (X-ray diffraction)

The XRD patterns of ZSM-5, single metal catalyst Mn/ZSM-5, and bimetal catalyst M(M = Fe, Cu, Ru, Ag)-Mn/ZSM-5 are shown in FIG. 3 . It can be seen that all catalysts have peaks (2θ = 22-25°, 44-46°) indicating the structural characteristics of ZSM-5. Through this, it can be seen that the structures of the single metal catalyst and the bimetal catalyst are maintained. In addition, it can be seen that, on the XRD peak, no peak of the supported metal appears except for the peak indicating the structure of ZSM-5. This is related to the amount of metal supported on the support. Usually, crystals are formed when more than 5 wt% of a metal material is supported on a surface area of 100 m 2 /g, and the peak intensity increases as the amount of loading increases. Mn was supported in 5 wt%, and bimetallic metals (Fe, Cu, Ru, Pd, Ag, Pt) were supported in 1 wt%, and no peak of the corresponding metal was observed due to the low loading amount. In addition, it can be seen through the XRD peak that the supported metal material has a high degree of dispersion and does not affect the phase change and crystallinity.

XPS (X-ray photoelectron spectra)

4 shows the spectra of Mn 2p of a single metal catalyst and a bimetal catalyst. The ranges of 641.76-642.80 eV and 653.19-653.97 eV ^{indicate Mn +3} , and 644.42-646.39 eV and 655.88-657.2 eV indicate Mn ⁺⁴ .

Table 2 summarizes the XPS results for Mn 2p. Mn value of ^{3+ / (Mn 3+ + Mn 4+} ) when the bimetallic catalyst Mn ^{3+ / (Mn 3+ + Mn 4+} ) the result than the Mn / ZSM-5 (0.69) a single metal catalyst in It can be seen that there is an overall increase. It has ^{been reported that Mn 3+ is more efficient than Mn 4+ in} toluene oxidation, and Mn ³⁺ has good ozone decomposition ability. When a bimetal catalyst is used, it can be expected that the performance will be better than that of a single metal catalyst for toluene oxidation.

5 shows the spectra of O 1s of a single metal catalyst and a bimetal catalyst. The range of 530.0-532.0 eV indicates lattice oxygen (Olattice), and the range of 532.0-533.0 eV indicates defective oxygen or oxygen vacancy (Ovacancy) [7]. In addition, Table 3 summarizes the XPS results for O 1s. Looking at the O 1s Ovacancy/Olattice ratio, it can be seen that the overall Ovacancy/Olattice value is higher for the bimetal catalyst than for the single metal catalyst, Mn/ZSM-5 (1.53), except for Ag-Mn/ZSM-5. can be checked It can be confirmed that the bimetal catalyst improves the formation of oxygen vacancy on the surface than the single metal catalyst. Ozone is decomposed into reactive oxygen species (O ^{2 -} , O ₂ ^{2 -} , O - ) through oxygen vacancy. Therefore, it can be confirmed that as the area of oxygen vacancy increases, more ozone is decomposed into reactive oxygen species and affects toluene oxidation.

H ₂ -TPR (Temperature-Programmed Reduction)

6 shows the H2-TPR results of a single metal catalyst and a bimetal. Each symbol in FIG. 6 is as follows. (a) Mn/ZSM-5; (b) Fe-Mn/ZSM-5; (c) Cu-Mn/ZSM-5; (d) Ru-Mn/ZSM-5; (e) Pd-Mn/ZSM-5; (f) Ag-Mn/ZSM-5; (g) Pt-Mn/ZSM-5

TPR indicates the extent of metal reduction by calculating the amount of hydrogen consumed. The single metal catalyst, Mn/ZSM-5, exhibits reduction temperatures of 332°C and 448°C. The reduction temperature of 332° C. _{represents the temperature when MnO2 is reduced to Mn 2} O ₃ , and 448° C. represents the temperature when Mn ₂ O ₃ is reduced to MnO. Fe-Mn/ZSM-5 shows the reduction temperatures of 406°C and 652°C, 406°C represents the reduction of Fe ₂ O ₃ to Fe ₃ O ₄ , and 652°C represents the reduction of Fe ₃ O ₄ to Fe. indicates the process. Cu-Mn/ZSM-5 represents a reduction temperature of 346° C. and means the peak of the process in which _{Cu 2 O is reduced to CuO.} Ru-Mn/ZSM-5 has two reduction temperatures of 189°C and 338°C, and is a peak representing the reduction process of ^{Ru 4+} → Ru ²⁺ → Ru ^{0 .} Ag-Mn/ZSM-5 has a reduction temperature of 270°C and a reduction process of ^{Ag +} →Ag ^{0 .} It can be confirmed that the reduction peak of the bimetal catalyst moved to a lower temperature than the reduction peak of the single metal catalyst. Looking at the intensity values of all catalysts, Mn/ZSM-5, Fe-Mn/ZSM-5, Cu-Mn/ZSM-5, and Ru-Mn/ZSM-5 have high intensity values, and Pd-Mn/ZSM- 5, Ag-Mn/ZSM-5 can be confirmed to have a low intensity value. In ozone-catalyzed oxidation reactions, the reducing properties of catalysts are very important. Among the catalysts, Ru-Mn/ZSM-5, which has a broad intesity peak and a low reduction temperature, will be effective in oxidizing toluene. This confirms that the reducing ability of Ru-Mn/ZSM-5 is large even at low temperature.

<Ozone-catalyzed oxidation experiment according to the type of bimetal>

Ozone-catalyzed oxidation according to ozone concentration

In order to select the optimal ozone concentration required for ozone-catalyzed oxidation, ozone-catalyzed oxidation reaction according to ozone concentration was tested. As a catalyst, Mn/ZSM-5 (SiO ₂ /Al ₂ O ₃ =280) was used, and the reaction experiment was conducted at a concentration of toluene of 100 ppm. 7 and 8 show the toluene removal rate and ozone removal rate and the amount of _{CO x generated according to the concentration of ozone, respectively.} The toluene removal rate and ozone removal rate were calculated as follows.

The reaction experiment was carried out by controlling the ozone concentration in the range of 600 ppm to 1200 ppm. Overall, as the ozone concentration increased, the removal rate of toluene also increased. In addition, it can be seen that the amount of _{CO x production is also increased.} On the other hand, when ozone concentrations of 1000 ppm and 1200 ppm are injected, it can be confirmed that there is no difference in the values of _{the removal rate of toluene and the amount of CO x generated.} Through this, the optimum ozone concentration required for ozone-catalyzed oxidation in this experiment was selected as 1000 ppm.

Complete Reaction Scheme 1 of toluene is shown below, and according to Scheme 1, 1800 ppm of ozone is required to completely oxidize 100 ppm of toluene. The experiment was conducted at 1000 ppm, which is a lower concentration than 1800 ppm, which is the concentration of ozone required for complete oxidation. The reason for the difference in the required ozone concentration can be explained by the autoxidation reaction, and the autoxidation reaction is shown in Scheme 4. _{A final product, CO x ,} is generated _{through a reaction between an oxygen species (O 2} ) generated by the decomposition of ozone and a radical intermediate (R·). Therefore, in ozone-catalyzed oxidation, efficiency can be achieved even with a concentration lower than ozone required for complete oxidation.

(반응식 1)

(Scheme 1)

(반응식 2)

(Scheme 2)

Ozone-catalyzed oxidation test results according to the type of bimetal

In order to select the optimal active metal for ozone-catalyzed oxidation, ozone-catalyzed oxidation reaction according to the type of bimetal was tested. In this experiment, after toluene was passed through the catalyst layer, the ozone catalytic oxidation reaction was carried out by introducing ozone after reaching a break-through point in which the concentration of the inflow toluene and the concentration of the discharged toluene coincide. 9 shows the toluene removal rate and ozone removal rate after 2 hours of reaction at room temperature. Toluene removal efficiency is Ru-Mn/ZSM-5 (36%) > Fe-Mn/ZSM-5 (27.4%) > Cu-Mn/ZSM-5 (27.1%) > Ag-Mn/ZSM-5 (23%) ) > Mn/ZSM-5 (14%). As a result, it can be confirmed that the toluene removal efficiency of all bimetal catalysts is improved compared to Mn/ZSM-5, which is a single metal catalyst. The ozone removal efficiency is Cu-Mn/ZSM-5 (69.62%) > Fe-Mn/ZSM-5 (65%) > Ru-Mn/ZSM-5 (57.79%) > Ag-Mn/ZSM-5 (49.1%) ) > Mn/ZSM-5 (45.1%) gradually decreased. It can also be confirmed that the ozone removal rate of the bimetal catalyst is improved compared to the single metal catalyst. In particular, the toluene removal efficiency of Ru-Mn/ZSM-5 is 36.87%, which is about 2.6 times higher than that of Mn/ZSM-5, which has a toluene removal efficiency of 13.84%.

10 shows the amount of _{CO x} production after 2 hours of room temperature reaction. The amount of CO _x produced gradually decreased as Ru-Mn/ZSM-5 > Fe-Mn/ZSM-5 > Ru-Mn/ZSM-5 > Ag-Mn/ZSM-5 > Mn/ZSM-5. _{In particular, the CO x} production amount of Ru-Mn/ZSM-5 _{is 94.44 ppm, which is about 1.9 times higher than the CO x} production amount of 52.62 ppm Mn/ZSM-5. Also, _{the amount of CO x} produced tends to be proportional to the value of the ozone removal rate. Therefore, it can be confirmed that the higher the ozone decomposition rate, the higher the _{amount of CO x produced.}

Overall, it can be seen that the efficiency of the bimetal catalyst is improved compared to the single metal catalyst, and in particular, it can be confirmed that Ru-Mn has high efficiency in the room temperature catalytic ozone oxidation reaction. Based on the XPS results, the _{ozone resolution, toluene oxidation, and CO x} generation results ^{through the ratio of Mn +3} /(Mn ⁺³ +Mn ⁺⁴ ) and the molar ratio of Ovacancy/Olattice. It can be seen that indicates In addition, as can be seen from the TPR results, it was confirmed that the reducing ability of Ru-Mn/ZSM-5 was the highest, and it can be seen that it has a higher activity than other catalysts in oxidizing toluene at room temperature. Therefore, in this study, Ru-Mn was selected as the optimal catalyst.

Analysis of catalyst surface by-products after reaction experiments

In the room temperature ozone oxidation reaction, it can be seen that the toluene removal rate and the ozone removal rate are low. This is because in the room temperature ozone oxidation reaction, intermediate reactants that are not completely oxidized are deposited on the catalyst surface. Therefore, in order to find the cause of the deactivation of the catalyst, GC/MS was used to analyze the product material deposited on the catalyst surface after 2 hours of ozone-catalyzed oxidation. 11 shows the GC/MS chromatogram, and Table 4 shows the material for the peak of the chromatogram. Substances such as Acetic acid, Toluene, Benzene carboxylic acid, and 2,2'-Dimethylbiphenyl were detected as the mainly deposited substances. Research results have been reported by many researchers that acids and aldehydes are generated as by-products when toluene is partially oxidized. An intermediate oxide is generated due to incomplete oxidation, and deposition of the intermediate oxide causes catalyst deactivation and leads to a decrease in toluene efficiency.

<Ozone catalytic oxidation experiment according to the type of support>

Ozone-catalyzed oxidation test results according to the type of support

In order to select a support with an appropriate skeletal structure that can improve catalytic activity, the selected bimetal 1wt% Ru - 5wt% Mn was supported on ZSM-5 and Y, which are zeolite catalysts _{having different SiO 2} /Al ₂ O _{3 ratios.} A room temperature ozone-catalyzed oxidation reaction was carried out. Table 5 shows the specific surface area and pore volume of Ru-Mn/ZSM-5 (SiO ₂ /Al ₂ O ₃ =23, 80, 280) and Y (SiO ₂ /Al ₂ O _{3 =5.1, 80).} Ru-Mn/Y (80) > Ru-Mn/Y (5.1) > Ru-Mn/ZSM-5 (80) > Ru-Mn/ZSM-5 (280) > Ru-Mn/ZSM-5 (23) In the order of , the size of the specific surface area and the pore volume decrease. Compared to ZSM-5, Y had a relatively larger specific surface area and pore volume. This is because Y is a mesoporous catalyst having larger pores than ZSM-5. Specific surface area and pore volume are factors affecting the adsorption of VOCs. The larger the specific surface area and the larger the pore volume, the greater the adsorption capacity for toluene, and the toluene adsorbed by the supported metal may be decomposed. Therefore, it can be expected that it will be effective for toluene oxidation of Ru-Mn/Y(80) having the largest surface area.

In this experiment, after passing toluene through the catalyst layer, the ozone catalytic oxidation reaction was performed by introducing ozone after reaching a break-through point in which the concentration of the inflow toluene and the concentration of the discharged toluene coincide. 12 shows the toluene removal rate and ozone removal rate after 2 hours of room temperature reaction of each catalyst. The removal efficiency of toluene is Ru-Mn/Y (80) > Ru-Mn/Y (5.1) > Ru-Mn/ZSM-5 (80) > Ru-Mn/ZSM-5 (280) > Ru-Mn/ZSM It gradually decreased in the order of -5 (23). The ozone removal efficiency is Ru-Mn/Y (80) > Ru-Mn/ZSM-5 (80) > Ru-Mn/Y (5.1) > Ru-Mn/ZSM-5 (280) > Ru-Mn/ZSM- It gradually decreased in the order of 5(23). It was consistent with the order of high removal efficiency and the order of large specific surface area and pore volume. 13 shows the amount of _{CO x} produced after 2 hours of room temperature reaction. Ru-Mn/Y(80) > Ru-Mn/ZSM-5(80) > Ru-Mn/ZSM-5(280) > Ru-Mn/Y(5.1) > Ru-Mn/ZSM-5(23) gradually decreased in the order of

The ozone removal rates of Ru-Mn/Y (80) and Ru-Mn/ZSM-5 (80) were 88.92% and 86.66%, respectively, indicating similar values. However, it can be seen that the toluene removal rate of Ru-Mn/Y (80) is significantly higher than that of Ru-Mn/ZSM-5 (80). Since zeolite Y has a larger specific surface area than ZSM-5, it can be confirmed that toluene is well adsorbed to the catalyst and shows high performance. Production of CO _x is a Ru-Mn / Y (80) is 135.42ppm a Ru-Mn / ZSM-5 ( 80) is high, but the Ru-Mn / Y (80) the amount of CO _x to 125.26 ppm, CO ₂ It can be seen that the amount of Ru-Mn/ZSM-5 (80) is 83.65 ppm, which is higher than that of Ru-Mn/Y (80), where the amount _{of CO 2 is 69.02 ppm.} From this result, it can be seen that the more ozone decomposes, the more CO _{x is produced.} Based on the above results, in _{the case of a zeolite catalyst having a SiO 2} /Al ₂ O ₃ ratio of 80, it can be confirmed that the toluene removal rate and ozone removal rate are high, and it has a high CO _{x production amount.}

long experiment

To compare Ru-Mn/Y (SiO ₂ /Al ₂ O ₃ =80) and Ru-Mn/ZSM-5 (SiO ₂ /Al ₂ O ₃ =80), toluene and ozone pass through the catalyst layer without reaching the breakthrough point The reaction was carried out at room temperature for 420 minutes. FIG. 14 shows the toluene and ozone removal rates and the amount of _{CO and CO 2} produced according to time of the room temperature ozone-catalyzed oxidation reaction using Ru-Mn/ZSM-5 (SiO ₂ /Al ₂ O _{3 =80).} Overall, the toluene and ozone removal efficiency decreased over time, and the CO ₂ concentration was maintained at a constant level after 90 minutes, and it can be seen that the CO decreased from 90 minutes. The toluene removal rate after 420 minutes was 41%, and the ozone removal rate was 43%. CO was 23 ppm and CO ₂ was 98 ppm.

15 shows the removal rates of toluene and ozone and the amount of CO and CO2 production according to time of the room temperature ozone-catalyzed oxidation reaction using Ru-Mn/Y (SiO2/Al2O3 = 80). Toluene and ozone removal efficiency maintains a constant high efficiency at the beginning, but it can be seen that the efficiency decreases rapidly after 70 minutes. It can be seen that CO and CO ₂ maintain a constant concentration after 100 minutes. Toluene removal rate after 420 minutes was 21%, the ozone removal efficiency was 60%, CO is 68ppm, 79ppm CO ₂ is yiyeotda. Before the reaction time 60 minutes, Ru-Mn/Y (80) showed high toluene and ozone removal rates. It can be confirmed that the efficiency is high by initially adsorbing more toluene than Ru-Mn/ZSM-5 (80) due to the large specific surface area of Ru-Mn/Y (80). After 60 minutes, it can be seen that the removal rate of toluene and ozone is rapidly decreased in Ru-Mn/Y (80). This is because the inactivation due to the adsorbed toluene and intermediate by-products occurred rapidly. Both types of catalysts show a tendency to degrade over time. This is because an intermediate oxide is generated due to incomplete oxidation, and the catalyst is deactivated due to deposition of the intermediate oxide.

_{16 shows the carbon balance (%) and CO 2} selectivity (%) according to time of the room temperature ozone-catalyzed oxidation reaction using Ru-Mn/Y (80) and Ru-Mn/ZSM-5 (80). The formula for carbon balance (%) and CO ₂ selectivity (%) is shown in the following formula.

Overall, carbon balance and CO ₂ selectivity tend to increase. The carbon balance value of the Ru-Mn/ZSM-5(80) catalyst was 46%, and _{the value of the CO 2} selectivity was 35%. The carbon balance value of Ru-Mn/Y (80) was 41%, and the CO ₂ selectivity value was 18%. The Ru-Mn/ZSM-5(80) catalyst has higher carbon balance and CO ₂ selectivity than the Ru-Mn/Y(80) catalyst. Through this, it can be confirmed that the complete oxidation reaction of Ru-Mn/ZSM-5(80) is better than that of Ru-Mn/Y(80) when the ozone-catalyzed reaction is performed at room temperature.

Ru-Mn/ZSM-5(80) shows high efficiency in _{toluene removal rate, carbon balance and CO 2 selectivity.} Therefore, it can be seen that Ru-Mn/ZSM-5(80) is the optimal catalyst for the ozone-catalyzed oxidation reaction at room temperature.

In the present invention, in order to select a bimetal capable of removing VOCs even at room temperature, a bimetal catalyst was studied through physical and chemical properties. First, in order to select an optimal bimetal, a study was conducted by supporting the metal on _{ZSM-5 (SiO 2} /Al ₂ O _{3 =280).} The single metal catalyst Mn/ZSM-5 and the bimetal catalyst Ru-Mn/ZSM-5, Fe-Mn/ZSM-5, Cu-Mn/ZSM-5, and Ag-Mn/ZSM-5 were compared. Among the catalysts, Ru-Mn/ZSM-5(280) had the highest reducing ability ^{, and through the molar ratio of Mn 3+} /(Mn ³⁺ +Mn ⁴⁺ ) and Ovacancy/Olattice, it oxidized and ozone toluene at room temperature. Since it exhibits higher activity than other catalysts in decomposing the metal, it was selected as the optimal bimetal.

In order to select a zeolite support suitable for the toluene ozone catalytic oxidation reaction, the selected bimetal was supported on a zeolite having a different Si/Al ratio. Ru-Mn/ZSM-5 (SiO ₂ /Al ₂ O ₃ =23, 80, 280) and Ru-Mn/Y (SiO2/Al2O3 =5.1, 80) were compared. The greater the specific surface area and pore volume of the catalyst, the higher the efficiency in oxidizing toluene, and the zeolite catalyst with a Si/Al ratio of 80 had the highest efficiency. In the case of long-term test, Ru-Mn/ZSM-5 (SiO ₂ /Al ₂ O ₃ =80) showed the highest toluene removal rate of 41% and ozone removal rate of 43% after 420 minutes of reaction, and the carbon balance (45 %) and CO ₂ selectivity (34%). However, the generation of intermediate by-products occurred and the generated intermediate by-products were deposited on the catalyst surface, causing deactivation of the catalyst. As a result, it has low toluene removal efficiency and low carbon balance and CO ₂ selectivity. Therefore, there is a need to improve the toluene and ozone removal rate by modifying Ru-Mn/ZSM-5(80) to suppress the generation of by-products, and to further research to increase the carbon balance and CO2 selectivity.

Claims (11)

As an M1-M2 bimetal catalyst for room temperature ozone catalytic oxidation of volatile organic compounds,
The M1-M2 bimetal catalyst is supported on zeolite,
The room temperature is 10 degrees Celsius to 35 degrees Celsius,
M1 is Ru, M2 is Mn,
The zeolite is ZSM-5 (SiO ₂ /Al ₂ O ₃ ) (80), ZSM-5 (SiO ₂ /Al ₂ O ₃ ) (280), Y (SiO ₂ /Al ₂ O ₃ ) (5.1), Y (SiO ₂ /Al ₂ O ₃ ) At least one bimetallic catalyst selected from the group comprising (80). delete delete According to claim 1,
The M1-M2 bimetallic catalyst is Ru-Mn, and the zeolite is ZSM-5 (SiO ₂ /Al ₂ O ₃ ) (80). According to claim 1,
The volatile organic compound is at least one selected from the group consisting of trimethylbenzene, nonane, methyl ethyl ketone, isopropyl alcohol, formaldehyde, benzene, toluene, and cyclohexane. 6. The method of claim 5,
The volatile organic compound is toluene bimetal catalyst. [Claim 7] A method for ozone-catalyzed oxidation of a volatile organic compound at room temperature using the bimetal catalyst according to any one of claims 1 to 6. 8. The method of claim 7,
A method of ozone-catalyzed oxidation by separately supplying ozone. 8. The method of claim 7,
The room temperature is 10 degrees Celsius to 35 degrees Celsius ozone catalytic oxidation method. An apparatus for ozone-catalyzed oxidation of volatile organic compounds at room temperature using the bimetal catalyst according to any one of claims 1 to 6. 11. The method of claim 10,
Ozone catalytic oxidation device with a separate supply line for ozone.

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