KR101574903B1 - Apparatus and method for methane oxidation - Google Patents

Abstract

Provided are a methane oxidation apparatus and a method thereof. The methane oxidation apparatus comprises: a methane oxidation reactor; an electrode part including a first electrode disposed in the methane oxidation reactor and a second electrode disposed on the outside of the methane oxidation reactor; and a methane oxidation catalyst disposed within the first electrode and the second electrode in the methane oxidation reactor.

Description

[0001] APPARATUS AND METHOD FOR METHANE OXIDATION [0002]

The present invention relates to a methane oxidation apparatus and a method thereof.

Oil, which is widely used as an energy source globally, is getting depleted, and oil prices are expected to remain high due to political unrest in the Middle East, which is the world's largest oil reserves. Compared to petroleum, natural gas is mainly methane, which is 40% richer than petroleum. It is a cheap and rich energy source buried all over the world. These natural gas are now widely used as fuel for cogeneration power plants and public transportation.

However, methane, which is released by incomplete combustion of natural gas, is a major cause of global warming, and they have a long life, which can have a greater adverse effect on global warming than carbon dioxide. Most industrialized countries have been striving to manage methane since the Euro III, including regulation of methane emissions from natural gas vehicles, especially heavy vehicles.

A fundamental way to reduce methane emissions is to completely burn methane. However, methane has very stable C-H bonds and is difficult to completely oxidize at low temperatures below 500 ° C. Therefore, the oxidation reaction of methane generally requires a large amount of noble metal as a catalyst. However, a certain amount of activation energy is required for a general catalytic reaction, and nowadays, the energy is supplied by thermal energy, which is a problem in that it is costly.

Recently, researches using plasma have been conducted to solve the above difficulties. Plasma can easily decompose C-H bond by high energy of plasma, and the time consumed in reaction is very short. However, if only plasma is used, there is a problem that a large amount of CO is generated due to high CO selectivity.

In order to solve the above problems, the present invention provides a methane oxidation apparatus capable of efficiently oxidizing methane.

The present invention provides a method for efficiently oxidizing methane.

Other objects of the present invention will become apparent from the following detailed description and the accompanying drawings.

The methane oxidation apparatus according to embodiments of the present invention includes a methane oxidation reactor, an electrode unit including a first electrode disposed inside the methane oxidation reactor and a second electrode disposed outside the methane oxidation reactor, And a methane oxidation catalyst disposed between the first electrode and the second electrode in the oxidation reactor.

The methane oxidation apparatus according to embodiments of the present invention includes a methane oxidation reactor, a methane oxidation catalyst disposed in the methane oxidation reactor, a first electrode passing through the catalyst, and a second electrode disposed outside the methane oxidation reactor, And an electrode unit including the electrode unit.

The methane oxidation catalyst may include palladium.

The methane oxidation catalyst may comprise at least one support selected from the group consisting of _{γ-Al 2 O 3, SiO} 2, and TiO _2.

The support may be? -Al ₂ O ₃ .

And a filter disposed in the methane oxidation reactor for filtering the gas that has passed through the methane oxidation catalyst.

The methane oxidation method according to embodiments of the present invention includes the steps of providing a methane oxidation catalyst inside a methane oxidation reactor, forming a plasma in a region provided with the methane oxidation catalyst, and introducing methane and oxygen into the methane oxidation reactor And injecting.

The methane oxidation catalyst may include palladium.

The methane oxidation catalyst may comprise at least one support selected from the group consisting of _{γ-Al 2 O 3, SiO} 2, and TiO _2.

The support may be? -Al ₂ O ₃ .

The oxygen may be injected at a molar ratio of 5 to 20 times with respect to the methane.

The methane oxidation apparatus according to the embodiments of the present invention can efficiently oxidize methane even at a relatively low temperature because the catalyst is formed inside the plasma, and the selectivity of carbon monoxide can be lowered.

Figure 1 schematically depicts a methane oxidation apparatus according to one embodiment of the present invention.
2 is a view for explaining a methane oxidation method using a methane oxidation system including a methane oxidation apparatus according to an embodiment of the present invention.
3 shows a Lisa main picture according to an experimental example.
Figure 4 shows the temperature function of the conversion of methane over a voltage under a single plasma condition according to an experimental example.
Figure 5 shows the input energy function of methane conversion under a single plasma condition according to an experimental example.
6 shows the concentration of carbon monoxide (CO) under a single plasma condition according to an experimental example.
FIG. 7 shows the selectivity of carbon monoxide (CO) under a single plasma condition according to an experimental example.
FIG. 8 shows the characteristics of the input voltage and the resultant current under a single plasma condition according to an experimental example.
Figure 9 shows the active starting temperature of various palladium-based catalysts under plasma-free conditions according to an experimental example.
10 to 12 show the reaction results when a methane oxidation catalyst of 2 wt% Pd / TiO ₂ according to an experimental example was used.
13 to 15 show the reaction results when a methane oxidation catalyst of 2 wt% Pd / SiO ₂ according to an experimental example is used.
16 to 18 show the results of reaction using a methane oxidation catalyst of 2 wt% Pd / γ-Al ₂ O ₃ according to an experimental example.
19 shows the methane conversion of 2 wt% Pd / γ-Al ₂ O ₃ in the post plasma according to an experimental example.

Hereinafter, the present invention will be described in detail with reference to examples. The objects, features and advantages of the present invention will be easily understood by the following embodiments. The present invention is not limited to the embodiments described herein, but may be embodied in other forms. The embodiments disclosed herein are provided so that the disclosure may be thorough and complete, and that those skilled in the art will be able to convey the spirit of the invention to those skilled in the art. Therefore, the present invention should not be limited by the following examples.

Methane oxidation unit

Figure 1 schematically depicts a methane oxidation apparatus according to one embodiment of the present invention.

Referring to FIG. 1, the methane oxidation apparatus 100 includes a methane oxidation reactor 110, an electrode unit 120, a methane oxidation catalyst 130, a gas injection unit 140, a filter 150, . ≪ / RTI >

The methane oxidation reactor 110 may have a shape of a cylinder, a faceted cylinder, and a plate. The methane oxidation reactor 110 may be formed of one or more materials selected from glass, Quartz, Pyrex, and ceramics. In the present embodiment, the methane oxidation reactor 110 may have a cylindrical shape of quartz having an inner diameter of 10 mm, a thickness of 1.3 mm, and a length of 500 mm.

The electrode unit 120 may include a first electrode 121 and a second electrode 122. The first electrode 121 may be disposed inside the methane oxidation reactor 110 to provide a high voltage. The first electrode 121 may be disposed to penetrate the methane oxidation catalyst 130. The first electrode 121 may have a shape such as a wire, a rod, a tube, or a plate. The first electrode 121 may be formed of a metal material including stainless steel. In this embodiment, the first electrode 121 may be a stainless steel rod having a thickness of 3 mm. The second electrode 122 may be a ground electrode disposed outside the methane oxidation reactor 110. The second electrode 122 may be a thin metal plate surrounding the outer wall of the methane oxidation reactor 110, and the metal plate may be, for example, a thin copper and / or stainless steel plate.

The electrode unit 120 may transmit the voltage supplied from the function generator 270 to the methane oxidation reactor 110. The voltage transferred to the methane oxidation reactor 110 may be a high voltage sinusoidal AC voltage and / or a pulse wave, thereby forming a plasma region 111 having a high energy level inside the methane oxidation reactor 110 . The plasma region 111 is a region where a plasma is formed due to a high voltage applied to the methane oxidation reactor 110. Specifically, when a high-voltage electric discharge is performed, electrons generated by the discharge collide with gas molecules in the inside, thereby changing the electron state of the outside of the gas molecules. As a result, radicals, excited molecules, and ions, which are chemically active species rich in reactivity, are positively or negatively charged to become an electrically neutral gas, which is called plasma. The plasma can be divided into a high-temperature plasma having a high temperature of electrons, ions and molecules, and a low-temperature plasma having only a high temperature of electrons. The high temperature plasma can be used to obtain a high temperature to melt the material or to treat the waste. Since the low-temperature plasma has only a high temperature of electrons, it can be applied to materials or conditions that can not be applied at high temperatures. The plasma can significantly reduce the selectivity of carbon monoxide that can be generated during the methane oxidation reaction.

The plasma may be formed as a dielectric barrier discharge. The dielectric barrier discharge is generated by the first electrode 121 of the electrode unit 120 and the second electrode 121 of the electrode unit 120 because the electrode unit 120 is surrounded by the dielectric by applying a high voltage in a state where one or both surfaces of the electrode unit 120 are surrounded by a dielectric. A direct discharge is not generated between the second electrodes 122, and a stable plasma having a high energy level can be formed. The methane oxidation reactor 110 may function as the dielectric.

The methane oxidation catalyst 130 may include palladium (Pd). Methane oxidation catalyst 130 may include at least one support selected from the group consisting of _{γ-Al 2 O 3, SiO} 2, and TiO _2. Preferably, the support may be? -Al ₂ O ₃ . The support may be preliminarily calcined at 400 to 600 ° C for 1 to 3 hours. The methane oxidation catalyst 130 may be formed by an initial wet impregnation method. For example, the methane oxidation catalyst 130 may be formed in such a manner that a Pd (NO ₃ ) ₂ .2H ₂ O precursor solution impregnates the support. The loading amount of the palladium may be 1-3 wt% of the methane oxidation catalyst 130. Preferably 2% by weight. After the precursor solution impregnates the support, the methane oxidation catalyst 130 can be calcined in air (N ₂ : O ₂ = 85: 15) at 400 to 600 ° C. for 1 to 3 hours. Preferably, the methane oxidation catalyst 130 can be calcined at 500 DEG C for 2 hours. In one embodiment, the methane oxidation catalyst 130 may be formed of particles having a size of 425-600 mu m in diameter.

The methane oxidation catalyst 130 may be disposed between the first electrode 121 and the second electrode 122 in the methane oxidation reactor 110. That is, the methane oxidation catalyst 130 may be disposed in the plasma region 111 formed by the first electrode 121 and the second electrode 122. The oxidation reaction of methane can be promoted by the methane oxidation catalyst 130 disposed in the plasma region 111. [ As described above, the methane oxidation catalyst 130 is disposed in the plasma region 111, so that the activation energy can be easily reached due to the energy of the plasma, so that the reactivity and efficiency can be increased.

The gas injection unit 140 may inject the injected gas a into the methane oxidation reactor 110. The injected gas (a) may comprise methane, oxygen, and an inert gas. The oxygen may have a molar ratio of 5 to 20 times the methane. Preferably, the oxygen may have a molar ratio of 10 times the methane. Whereby the methane can be completely oxidized by the relatively rich oxygen. The inert gas can function to stably generate and maintain a plasma region 111 having a high energy level. The inert gas may include at least one selected from helium, argon, and neon.

The filter 150 may be disposed below the methane oxidation catalyst 130 in the methane oxidation reactor 110 to filter the gas that has passed through the methane oxidation catalyst 130. In this embodiment, the filter 150 may be formed of quartz and may have a thickness of 2.0 mm. The filter 150 may be coupled with the first electrode 121 to fix the first electrode 122 inside the methane oxidation reactor 110.

The thermometer 160 can measure the temperature of the methane oxidation catalyst 130. The thermometer 160 may be disposed under the filter 150 and may be a K type thermocouple protected by a protective tube 161. The protection tube 161 may be formed of quartz and / or ceramic and may minimize interference between the thermometer 160 and the plasma region 111. Due to the protection tube 161, the thermometer 160 can measure the temperature without interference of the plasma region 111 during the methane oxidation reaction.

Methane oxidation method

2 is a view for explaining a methane oxidation method using a methane oxidation system including a methane oxidation apparatus according to an embodiment of the present invention.

Referring to FIG. 2, the methane oxidation system 200 includes a methane oxidation unit 100, a methane storage unit 210, an oxygen storage unit 220, an inert gas storage unit 230, a mass flow controller 240, A moisture trap 250, a gas chromatography 260, a function generator 270, a voltage amplifier 280, and a capacitor 290.

The methane oxidation method includes the steps of providing a methane oxidation catalyst 130 in the methane oxidation reactor 110, forming a plasma in a region where the methane oxidation catalyst 130 is provided, , Oxygen, and an inert gas.

Referring again to FIGS. 1 and 2, a methane oxidation catalyst 130 is provided within the methane oxidation reactor 110. The methane oxidation catalyst 130 may comprise palladium. Methane support of the oxidation catalyst 130 may comprise a _{γ-Al 2 O 3, SiO} 2, TiO ₂ and at least one selected from a. Preferably, the support may be? -Al ₂ O ₃ .

And forms the plasma in the region where the methane oxidation catalyst 130 is provided. The plasma may be formed by a high voltage. For example, a sinusoidal AC high voltage and / or a pulse wave is generated through the function generator 270 and the voltage amplifier 280, and the sinusoidal AC high voltage and / or the pulse wave is transmitted through the electrode unit 120 to the methane oxidation reactor 110 < / RTI > The plasma may be formed in the methane oxidation reactor 110 by the sinusoidal AC high voltage and / or the pulse wave transmitted to the methane oxidation reactor 110. For example, the sinusoidal AC high voltage may have a maximum peak voltage of 4 kVp-p (peak to peak), a maximum peak voltage of 20 kV, and a maximum frequency of 20 kHz. The plasma region 111 in which the plasma is formed may have a high energy level. The plasma region 111 may include a region where the methane oxidation catalyst 130 is provided. The plasma may be a low temperature plasma, and the temperature of the plasma region 111 may be 200 DEG C or less.

The methane, the oxygen, and the inert gas may be injected into the methane oxidation reactor 110 in which the plasma region 111 is formed. The gas stored in the methane storage unit 210, the oxygen storage unit 220, and the inert gas storage unit 230 may be injected through a mass flow controller (MFC) 240. The injected gas (a) containing the methane, the oxygen, and the inert gas may be injected into the methane oxidation reactor 110 through the gas inlet 140.

The oxygen may be injected at a molar ratio of 5 to 20 times with respect to the methane. Preferably, the oxygen can be injected at a molar ratio of 10 times with respect to the methane. The inert gas may be at least one selected from helium, argon, and neon. The concentration of the inert gas may be at least 95%. The inert gas may contribute to the stability of the plasma region 111.

The methane and oxygen supplied to the plasma region 111 may be decomposed to cause the methane oxidation reaction. The oxygen molecules excited by the plasma and the methane molecules may more easily cause an oxidation reaction by the methane oxidation catalyst 130.

The methane oxidation reaction is as follows. Radicals can be generated as in the reaction formula (1) by collision of electrons generated in the plasma region 111, the oxygen molecules, and the methane molecules. The methanation reaction may occur by the radicals.

In the equation (1), e * represents electrons having energy generated in the plasma region 111, and e represents electrons that have lost energy. In one embodiment, the oxygen radical may be greater than the methane radical, since the oxygen may have a molar ratio of 10 times the methane. As a result, a reaction similar to the reaction formula (2) can occur.

The hydrogen and carbon monoxide generated in the reaction formula (2) can cause an oxidation reaction by an excessive amount of the oxygen radical. As a result, water and carbon dioxide can be produced as in the reaction formula (3).

The methane oxidation apparatus 100 may further include a device capable of raising the temperature of the methane oxidation reactor 110 such as a furnace. In one embodiment, the furnace may raise the temperature of the methane oxidation catalyst 130 and the plasma region 111 within the methane oxidation reactor 110 to facilitate and complete the methane oxidation reaction.

The product gas (b) of the methane oxidation apparatus 100 may contain the water and the carbon dioxide. The product gas (b) can be removed while passing through the water trap (250). The product gas (b) from which the water has been removed can be inspected through gas chromatography (260).

[Experimental Example]

In the present specification, the term "plasma-catalytic hybrid condition" refers to a condition in which a methane oxidation reaction using both a plasma and a catalyst is referred to as a "plasma-catalyst hybrid condition", and a reaction using only a plasma is referred to as a "plasma single condition" '.

Through the following experimental examples, the degree of methane oxidation in the plasma-catalyst hybrid, the plasma single, and the single catalyst condition can be observed.

Plasma power measurement: Lissajous method

Fig. 3 shows a lithography diagram according to an input voltage.

According to the gas discharge theory, the load characteristic of the methane oxidation apparatus 100 is the same as that of the capacitor 290. The progress of the dielectric barrier discharge is the same as the charge and discharge transitions of the capacitor 290. The capacitor 290 may be located between the second electrode 122 of the methane oxidation apparatus 100 and a ground to measure charge transfer.

Referring to the following equations (1), (2) and FIG. 3, the power of the plasma region 111 can be obtained by measuring the area of the V-Q lithography cycle. The slope of the discharge transitions is equal to the capacitance of the dielectric, and the transition of the capacitance is equal to the total capacitance of the methane oxidizer 100.

In this case, P = discharge power, T = time, I = current, U = voltage, Q = charge, C _M = measuring capacitor, U _C = voltage of measuring capacitor, f = frequency,

How to measure activity

The activity of the methane oxidation catalyst 130 can be measured under atmospheric pressure in the methane oxidation apparatus 100.

In this experimental example, the injection gas (a) is 2500 ppm of the methane and 2.5% of the O ₂ , and the helium (He) can be balanced. The total gas flow rate can be maintained at 200 cm ³ / min. The space velocity can be about 24000 h < ^-1 >. The injection gas (a) can be controlled using the mass flow controller 240. The gases leaving the plasma region 111 can be analyzed with a gas chromatograph 260 equipped with a thermally conductive detector (TCD) and a 60/80 Carboxen-1000 packed bed. The methane oxidation can be divided into a state in which the methane oxidation catalyst 130 is present in the steady state condition and a state in which the methane oxidation catalyst 130 is absent.

In this experimental example, since the oxygen is present in excess, it can be assumed that the product after the reaction is most of the CO and the CO ₂ . Therefore, methane conversion, selectivity of CO and CO ₂ species can be defined by the following equations (3), (4), and (5).

Experiment result

1. Methane oxidation in a single plasma condition

When the plasma region 111 is in a single condition and both the plasma region 111 and the methane oxidation catalyst 130 are present, an experiment comparing the methane oxidation reaction can be performed as follows.

The input energy of the plasma region 111 is one of the important parameters in the methane oxidation. Specific input energy was measured by the Lisa diagram above, which is shown in FIG.

At the same input voltage and frequency, the plasma power can vary slightly with temperature, since the higher the temperature, the easier the active radicals such as electrons and ions can be generated. The plasma power can be increased with an increase in temperature. The non-injected energy may be 32 to 41 J / L at 2 kVp-p input voltage, 91 to 104 J / L at 3 kVp-p input voltage, and 165 to 231 J / L at 4 kVp-p input voltage.

Figure 4 shows the conversion of methane over various voltages under a single plasma condition as a function of temperature.

Referring to FIG. 4, the input voltage may be set to be less than 4 kVp-p, since electrical energy at 5 kVp-p can cause damage to the methane oxidizer 100 due to arc discharge.

Figure 5 shows methane conversion as a function of the input energy under plasma single conditions.

Referring to FIG. 5, the methane conversion rate increased with the increase of the non-input energy. This result can be explained by the phenomenon that active species such as the radicals are further generated at high non-input energies.

FIG. 6 shows the concentration of carbon monoxide (CO), and FIG. 7 shows the selectivity of carbon monoxide (CO).

Referring to FIGS. 6 and 7, the concentration and selectivity of CO begins to fall after 200 ° C. This is because the gas phase oxidation of CO to CO ₂ begins to operate under these conditions. However, under the dielectric barrier discharge plasma, the complete CO oxidation to CO ₂ can be stagnated to about 300 ° C, as the higher the input voltage, the more amount of CO can be predominantly produced by the partial oxidation of methane .

In the case of the plasma single condition, the CO selectivity may be about 50% below 100 < 0 > C. This can be explained by the following plasma chemistry. Under the plasma condition, the most abundant inert gas can transfer energy to molecules such as methane or oxygen by collision. However, the contribution of the inert gas in the overall reaction can be neglected, since the number of molecules of the inert gas does not change during the course of the reaction under the plasma. On the other hand, the methane and the oxygen can be separated by contact with the energy-rich plasma region 111 electrons to form the methane, the hydrogen, and the oxygen radical, respectively. Under these conditions, the oxygen radical is more reactive than the methane, and its amount can be enriched 10 times. The oxygen radical can react with the methane, the hydrogen, or the hydroxyl radical to form the CO, CO ₂ , and H ₂ O. The CO can be generated more selectively at low temperatures. The higher the temperature, the more CO ₂ can be produced through the gas phase oxidation of the CO to CO ₂ . At the low temperature condition, the following reaction may occur.

In this reaction, the higher the temperature, the more pronounced the final reaction. Therefore, the CO selectivity can be suddenly reduced as shown in FIG.

Figure 8 shows the characteristics of the input voltage and resulting current under a single plasma condition.

Referring to FIG. 8, it is shown that most of the discharge current peaks exist in the rising and falling parts of the applied voltage curve (black line). As the input voltage increases, the resulting current peak can also be larger. This is because the active species such as electrons, ions, and radicals are generated in large quantities.

2. Palladium-based catalysts Methane oxidation at single conditions

Specific surface area and palladium dispersion of the various methane oxidation catalysts 130 are shown in Table 1 below. , Containing a palladium support is γ-Al ₂ O ₃ of Pd / γ-Al ₂ O ₃ has the largest specific surface area of the methane oxidation catalyst (130). In the XRD results (not shown), the single peak assigned to the support appears to be present irrespective of the peak at which the palladium is concerned, indicating that the palladium is well dispersed. The degree of dispersion of the palladium is in the order of Pd / γ-Al ₂ O ₃ , Pd / SiO ₂ , and Pd / TiO ₂ .

Figure 9 shows the active starting temperature of the palladium-based methane oxidation catalyst 130 in the methane oxidation of the catalyst single conditions.

Referring to FIG. 9, when there is no plasma region 111, all of the methane oxidation catalyst 130 can start the reaction at 200 ° C or higher. The Pd / SiO ₂ showed the best performance in the methane oxidation, followed by Pd / γ-Al ₂ O ₃ and Pd / TiO ₂ . The oxidation of the methane may proceed on all catalysts as evidenced by the single production of the CO ₂ .

catalyst Specific surface area (m ² / g) Palladium dispersion (%) Pd / SiO ₂ 151 4.8 Pd / TiO ₂ 80 4.2 Pd / γ-Al ₂ O ₃ 240 5.7

3. Methane oxidation in plasma-catalytic hybrid conditions

In order to demonstrate the effect of the plasma-catalyst hybrid, a methane oxidation catalyst 130 may be prepared in the plasma region 111 plasma region 111. The synergistic factor f for evaluating the synergistic effect of the decrease of methane, the formation of CO, and the formation of CO ₂ is as shown in the following formulas (6) to (8).

The synergistic factor represents the correlation between the plasma-catalyst hybrid reaction, the plasma single reaction, and the catalyst single reaction. If the f- _methane value exceeds 1, it indicates that there is a synergistic effect of the plasma-catalyst hybrid reaction.

Table 2 below summarizes the synergy factors at room temperature of the catalysts in the plasma-catalyst hybrid system. Table 2 shows that the above plasma-catalyst system has no significant synergistic effect on the methane conversion except in the case of 2 wt% Pd / Al ₂ O ₃ . However, with regard to the CO or the CO ₂ , in most cases the synergy factor for the CO has decreased and the factor for the CO ₂ has increased. Thus, the palladium-based catalyst can improve the CO ₂ selectivity regardless of the support.

Input voltage
2 wt% Pd / Al ₂ O ₃ 2 wt% Pd / SiO ₂ 2 wt% Pd / TiO ₂ f _methane 2 kV _pp 0.75 0.40 0.69 3 kV _pp 1.06 0.62 1.00 4kV _pp 1.67 1.08 0.95 f _CO 2 kV _pp 0.25 0.35 0.56 3 kV _pp 0.31 0.35 0.52 4kV _pp 0.09 0.30 0.46 f _CO2 2 kV _pp 0.99 0.57 1.28 3 kV _pp 1.46 0.92 1.55 4kV _pp 2.47 1.75 1.47

The comparison of the catalyst single conditions, the plasma single conditions, and the plasma-catalytic hybrid methane oxidation conditions using a palladium catalyst can be expressed as a function of temperature and input voltage. The CO selectivity closer to 0% is better. The CO selectivity is much lower in the plasma-catalyst hybrid condition than in the plasma single condition, indicating that the methane oxidation catalyst 130 plays a positive role in the methane oxidation reaction.

10 to 12 show the reaction results when a methane oxidation catalyst of 2 wt% Pd / TiO ₂ was used.

Referring to Figures 10-12, the performance of the 2 wt% Pd / TiO ₂ is relatively low compared to other palladium-based catalysts. At low input voltages, synergy between the plasma region 111 and the methane oxidation catalyst 130 is hardly noticeable. Even at 4 kVp-p, the plasma-catalyst hybrid reaction exhibited the methane conversion similar to that of the plasma single reaction. The TiO ₂ is expected to have a better synergistic effect because it has a higher dielectric constant than the SiO ₂ or the Al ₂ O ₃ . However, TiO ₂ has a lower dielectric constant than a general ferroelectric material, and the Pd / TiO ₂ shows no synergistic effect in the methane oxidation reaction despite its relatively high dielectric constant.

13 to 15 show the reaction results when a methane oxidation catalyst of 2 wt% Pd / SiO ₂ is used.

When 13 to refer to FIG. 15, since the non-void ratio (non-porosity) and low dielectric constant of the SiO ₂ and the resulting current input energy ratio is significantly lower at a lower input voltage (2kVp-p and 3kVp-p). Therefore, the plasma-catalyst hybrid condition appears to have an antagonistic effect. It was also confirmed that f- _methane was low (0.40 and 0.62) in the plasma-catalyst hybrid conditions, as shown in Table 2. The 2 wt% Pd / SiO ₂ has a relatively low plasma energy at low input voltage, which increases the plasma energy recovered to the value of the plasma single response, as shown in Table 3.

catalyst Input voltage (Vp-p)
(Non-applied energy (J / L)) The dielectric constant (ε)
Pd / TiO ₂
2 (23-40)
80
3 (101-110) 4 (172-227)
Pd / SiO ₂
2 (8-32)
3.9
3 (83-94) 4 (169-194)
Pd / γ-Al ₂ O ₃
2 (18-34)
9
3 (88-97) 4 (163-191)

16 to 18 show the reaction results when a methane oxidation catalyst of 2 wt% Pd / γ-Al ₂ O ₃ was used.

16 to 18, in the case of ₂ kVp-p and 3 kVp-p, the slope of the graph is the same as the Pd / TiO ₂ and Pd / SiO ₂ , -off Temperature). Low power dielectric barrier spin plasma (2kVp-p and 3kVp-p) can not change the entire reaction as evidenced by the same termination temperature of the reaction. However, at 4 kVp-p, a strong synergy effect was observed between the above-mentioned methane oxidation plasma region 111 and the 2 wt% Pd / γ-Al ₂ O ₃ catalyst. At room temperature, the methane conversion of the plasma-catalyst hybrid reaction exceeded that of the plasma single reaction. The synergy factor in the plasma-catalyst hybrid condition was greater than 1 (1.67). The XRD (X-ray diffraction analysis) and BET analysis results of all the catalysts after the reaction were not changed. Thus, the dielectric barrier discharge plasma may not affect the textual properties of the methane oxidation catalyst 130 under these operating conditions.

In the case of the Pd / γ-Al ₂ O ₃ and the Pd / SiO _{2 having} a low light-off temperature, the input voltage can be activated at 4 kVp-p or more. This is because they have low activation energies, so that the plasma region 111 energy can easily overcome the activation energy barrier. However, except for the case of Pd / y-Al ₂ O ₃ , the combination of the plasma and the methane oxidation catalyst 130 may be similar or lower than the plasma single reaction. That is, the catalyst support, γ-Al ₂ O ₃ , may have a higher methane conversion rate when combined with the dielectric barrier discharge plasma. This is because the γ-Al ₂ O ₃ is porous with a high surface area, so that the plasma can be used to improve the synergistic ability of the methane oxidation.

4. Dielectric barrier discharge plasma and Pd / γ-Al ₂ O ₃ Effect of catalyst hybrids

When the Pd / γ-Al ₂ O ₃ catalyst is prepared in the methane oxidation reactor 110, the methane conversion can be expressed under specific conditions. However, since the length of the plasma region 111 may be longer than the layer of the methane oxidation catalyst 130, it is unclear whether the synergy of the methane oxidation catalyst 130 occurs due to the plasma. An in-plasma method in which the methane oxidation catalyst 130 is disposed in the plasma region 111 and a post-plasma method in which the methane oxidation catalyst 130 is disposed in a region different from the plasma region 111, Methods can be compared to reveal the source of the synergy effect.

19 shows the conversion of methane to the 2 wt% Pd / γ-Al ₂ O ₃ catalyst in the post-plasma.

Referring to FIG. 19, the CO selectivity was maintained at a low level similar to that of the phosphorous plasma. However, the synergy of the methane conversion in the post-plasma is hard to find. Therefore, it is preferable that the plasma region 111 and the methane oxidation catalyst 130 are present in the same region in order to enhance the synergy effect in the methane oxidation reaction. The post plasma may not allow the active radicals formed by the plasma to reach the methane oxidation catalyst 130.

Hereinafter, specific embodiments of the present invention have been described. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

100: methane oxidizer 110: methane oxidation reactor
111: plasma region 120: electrode portion
121: first electrode 122: second electrode
130: methane oxidation catalyst 140: gas injection unit
150: filter 160: thermometer
161: Protection tube 200: Methane oxidation system
210: methane storage part 220: oxygen storage part
230: inert gas storage unit 240: mass flow controller
250: Moisture trap 260: Gas chromatography
270: Function generator 280: Voltage amplifier
290: Capacitor a: Injection gas
b: product gas C + P: catalyst + plasma
C: Catalyst P: Plasma

Claims (9)

Methane oxidation reactor;
An electrode unit including a first electrode disposed inside the methane oxidation reactor and a second electrode disposed outside the methane oxidation reactor; And
And a methane oxidation catalyst disposed between the first electrode and the second electrode in the methane oxidation reactor,
Wherein the methane oxidation catalyst comprises palladium,
The methane oxidation catalyst is methane oxidation apparatus characterized in that it comprises at least one support selected from the group consisting of _{γ-Al 2 O 3, SiO} 2, and TiO _2. Methane oxidation reactor;
A methane oxidation catalyst disposed in the methane oxidation reactor; And
And an electrode unit including a first electrode passing through the methane oxidation catalyst and a second electrode disposed outside the methane oxidation reactor,
Wherein the methane oxidation catalyst comprises palladium,
The methane oxidation catalyst is methane oxidation apparatus characterized in that it comprises at least one support selected from the group consisting of _{γ-Al 2 O 3, SiO} 2, and TiO _2. delete 3. The method according to claim 1 or 2,
The support methane oxidation device, characterized in that γ-Al ₂ O _3. 3. The method according to claim 1 or 2,
And a filter disposed in the methane oxidation reactor for filtering gas passing through the catalyst. Placing a methane oxidation catalyst in the methane oxidation reactor;
Forming a plasma in a region where the methane oxidation catalyst is disposed; And
And injecting methane and oxygen into the methane oxidation reactor,
Wherein the methane oxidation catalyst comprises palladium,
The methane oxidation catalyst is methane oxidation method which is characterized in that it comprises at least one support selected from the group consisting of _{γ-Al 2 O 3, SiO} 2, and TiO _2. delete The method according to claim 6,
The support methane oxidation, characterized in that γ-Al ₂ O _3. The method according to claim 6,
Wherein the oxygen is injected at a molar ratio of 5 to 20 times with respect to the methane.

Images