Methods of coating a blade electrode, a blade electrode, a sliding arc plasma reactor, and a method of plasma conversion of methane

Abstract

The present application relates to the field of plasma, and discloses a method for coating a blade electrode, a blade electrode, a sliding arc plasma reactor and a method for plasma conversion of methane, the method comprising: using an atomic layer deposition method to apply a coating material to a blade electrode in a sliding arc plasma reactor to obtain a plating layer containing at least two single-layer atomic layer deposition metal oxide films arranged in layers on the surface of the blade electrode, the plating layer being a semiconductor material, and the forming material of each single-layer atomic layer deposition metal oxide film being the same. The scheme provided by the present application modifies the blade electrode by coating a dielectric layer on the surface of the blade electrode, thereby weakening the arc energy, reducing the plasma field temperature, and further allowing methane to be directly and efficiently converted into ethylene under the action of an electric field, and reducing energy consumption, effectively inhibiting carbon deposition, producing no CO2, having a high ethylene yield, no risk of combustion and explosion, and being more safe and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of plasma, and more specifically to a method for coating blade electrodes, blade electrodes, a sliding arc plasma reactor, and a method for plasma-converted methane. Background Technology

[0002] Plasma methane conversion technology has been studied in China since the 1980s, and has gradually become a patented technology since 2000.

[0003] CN1360008A discloses a method for producing gasoline from methane and carbon dioxide using plasma conversion, in which CO2 is added as another reactant and gasoline is the main product. CN1552680A discloses a method for producing acetylene from methane-containing gas via thermal plasma cracking, primarily using methane as raw material and acetylene as the main byproduct. CN100999432A discloses a method for producing C2 hydrocarbons from methane via plasma catalytic ionic liquid conversion. CN101734620A discloses a method for producing hydrogen from methane-rich plasma.

[0004] Southwest Chemical Research and Design Institute has announced a series of patented technologies for plasma cracking of methane, mainly focusing on the development of plasma conversion of methane to produce carbon black or acetylene and hydrogen, with a greater emphasis on process design and optimization.

[0005] Tsinghua University, Taiyuan University of Technology, and Xinjiang Tianye Group have jointly developed a plasma pyrolysis coal-to-acetylene process. The process mainly uses coal as raw material and natural gas as an auxiliary agent to produce acetylene and hydrogen. The working gas is hydrogen.

[0006] Zhejiang University has primarily developed methods for online plasma decoking, which can introduce CO2 or H2 to remove carbon buildup on the electrode surface. They have also developed a rotating arc plasma method for pyrolyzing methane to produce acetylene, where the working gas rotates into the discharge gap, and is simultaneously driven by an external magnetic field, resulting in millisecond-level pyrolysis.

[0007] Analysis of foreign literature and patents revealed that the initial method for converting methane into olefins was mainly based on arc cracking of methane, with acetylene as the main product. Carbon black was produced as a byproduct because carbon deposits were easily generated during the process.

[0008] Other researchers have discovered that product distribution can be adjusted by changing the inlet flow rate or incorporating inert gases. This technology has already been industrialized abroad, including four processes: the HUELS process, the AVCO process, the Du Pont process, and the Romanian process.

[0009] A comparison of literature revealed that using an electric arc to generate high-temperature cracking of natural gas to produce acetylene has low energy efficiency, consuming approximately 13,900 kWh of electricity per ton of acetylene produced, accounting for more than 50% of the cost. Therefore, changing the reactor structure to achieve energy saving and consumption reduction is one of the key innovations in foreign patent literature.

[0010] Building upon the aforementioned technologies, a series of "warm" plasma and "cold" plasma technologies have been developed. By altering the energy generation method and reducing energy consumption, and by incorporating catalysts for coupling, these technologies can directionally convert methane into the target product. Currently, this process is still under exploration; pilot-scale plants exist, but no industrial-scale plants have been reported.

[0011] In summary, most studies on the plasma conversion of natural gas to ethylene employ plasma-catalytic coupling. Dielectric barrier discharge primarily produces ethane, while thermal plasma or sliding arc plasma mainly produces acetylene. Currently, no plasma form can directly produce ethylene.

[0012] In addition, CN106925086A discloses a plasma degradation treatment device for organic waste gas. This plasma treatment device is a plasma reactor, including a reactor cylinder, a gas inlet at the top of the reactor cylinder, a gas outlet at the bottom of the reactor, a plasma discharge electrode located inside the reactor cylinder, and a power interface for supplying power to the plasma discharge device. The reactor cylinder is equipped with an energy utilization device that expands the area and length of the sliding arc. The energy utilization device is an arc expander rod, an arc expander plate, or a combination of both. However, when this reactor is used for the directional conversion of methane, the methane conversion rate is low, and the olefin selectivity is low. Summary of the Invention

[0013] The purpose of this invention is to overcome the shortcomings of existing plasma technology in the low conversion efficiency of methane to ethylene.

[0014] To achieve the above objectives, a first aspect of the present invention provides a method for coating a blade electrode, the method comprising: applying a coating material to a blade electrode in a sliding arc plasma reactor using atomic layer deposition to obtain a coating layer on the surface of the blade electrode containing at least two stacked monolayer atomic layer deposited metal oxide films, the coating layer being a semiconductor material, and each of the monolayer atomic layer deposited metal oxide films being formed of the same material.

[0015] A second aspect of the present invention provides a blade electrode obtained by coating using the method described in the first aspect above.

[0016] A third aspect of the present invention provides a sliding arc plasma reactor having a coaxial jacketed structure, and the reactor comprising:

[0017] The inner cylinder is provided with a reactor inlet, a side feed inlet, a lower reaction zone, and a product outlet.

[0018] An outer cylinder is nested outside the inner cylinder, and a heat-conducting medium inlet and a heat-conducting medium outlet are respectively provided on the outer cylinder;

[0019] A blade electrode sliding arc generator, comprising a gas nozzle, a blade electrode, and a base;

[0020] The side feed inlet passes through the outer cylinder and enters the inner cylinder, allowing the reaction gas to enter the inner cylinder through the side feed inlet; at least two blade electrodes are symmetrically distributed on the base of the blade electrode sliding arc generator, allowing a discharge area to be formed between the blade electrodes; the base is provided with a gas nozzle, allowing the raw material gas to enter the inner cylinder from the reactor inlet through the gas nozzle;

[0021] The blade electrode is the blade electrode described in the second aspect above.

[0022] A fourth aspect of the present invention provides a method for plasma conversion of methane, the method being carried out in the sliding arc plasma reactor described in the third aspect above, the method comprising:

[0023] Under plasma discharge conditions, a methane-containing feed gas is introduced into the inner cylinder of the sliding arc plasma reactor through the reactor inlet and the gas nozzle, while a hydrogen-containing reaction gas is introduced into the inner cylinder of the sliding arc plasma reactor through the side feed inlet. The feed gas then passes sequentially through the discharge region formed by the blade electrode and the lower reaction zone to carry out a methane conversion reaction. The product obtained after the reaction is led out of the sliding arc plasma reactor through the product outlet. Furthermore, the required temperature of the sliding arc plasma reactor is maintained by continuously introducing a heat-conducting medium into the outer cylinder of the sliding arc plasma reactor through the heat-conducting medium inlet and leading the heat-conducting medium out through the heat-conducting medium outlet.

[0024] Compared with the prior art, the solution provided by the present invention has at least the following advantages:

[0025] (1) The solution provided by the present invention modifies the blade electrode by coating the surface of the blade electrode with a dielectric layer, thereby weakening the arc energy and reducing the plasma field temperature, thereby enabling methane to be directly converted into ethylene; this solution can effectively simplify the process of converting methane into olefins, and directly and efficiently convert methane into ethylene under the action of an electric field.

[0026] (2) The solution provided by the present invention can achieve continuous and stable reaction with high reactant conversion efficiency, reduce energy consumption, effectively suppress carbon deposition, and compared with the traditional methane to olefins process, there is no CO2 generation, high ethylene yield, no risk of combustion and explosion, and it is safer and more environmentally friendly.

[0027] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a preferred embodiment of the sliding arc plasma reactor provided by the present invention.

[0029] Explanation of reference numerals in the attached figures

[0030] 1 Reactor inlet 2 Gas nozzle

[0031] 3 Blade electrode 4 Side feed inlet

[0032] 5. Heat transfer medium inlet 6. Heat transfer medium outlet

[0033] 7. Product export 8. Base

[0034] 9. Activity Connection Mechanism Detailed Implementation

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] As previously described, a first aspect of the present invention provides a method for coating a blade electrode, the method comprising: applying a coating material to a blade electrode in a sliding arc plasma reactor using atomic layer deposition to obtain a coating layer on the surface of the blade electrode comprising at least two stacked monolayer atomic layer deposited metal oxide films, the coating layer being a semiconductor material, and each of the monolayer atomic layer deposited metal oxide films being formed of the same material.

[0037] Preferably, the coating material is an organic compound containing a metal element.

[0038] Preferably, the semiconductor material is selected from at least one of metal oxides.

[0039] More preferably, the semiconductor material is selected from at least one of Al2O3, ZrO2, SnO2, ZnO, HfO2, TiO2, La2O3, Ta2O5, and Y2O3.

[0040] Preferably, the step of coating the blade electrode in the sliding arc plasma reactor using atomic layer deposition includes: in an atomic layer deposition apparatus,

[0041] (1) In the presence of carrier gas, open the ALD valve of the metal source tank so that the coating material in the metal source tank enters the oxygen-containing reaction chamber, so that the coating material reacts with oxygen on the blade electrode surface in the reaction chamber and forms a single-layer atomic layer deposited metal oxide film.

[0042] (2) Repeat step (1) to obtain the coating, each time forming a single atomic layer of deposited metal oxide film, and adjust the coating thickness by controlling the number of repetitions.

[0043] Preferably, in step (1), the temperature of the metal source tank is 140-160°C, the temperature of the reaction chamber is 50-400°C, and the temperature of the transport pipeline and the ALD valve is 180-200°C.

[0044] Preferably, in step (1), the reaction chamber and the transport pipeline are evacuated to a pressure of 10-200 Pa.

[0045] Preferably, in step (1), the flow rate of the carrier gas is 10-200 sccm.

[0046] Preferably, in step (1), the opening time of the ALD valve is 50-2000ms.

[0047] Preferably, step (1) further includes cleaning the reaction chamber by introducing an inert gas pulse.

[0048] More preferably, the cleaning time is 1-200 seconds.

[0049] In this invention, the number of monolayer atomic layer deposited metal oxide films repeatedly formed is 200-600.

[0050] In this invention, after coating the blade electrode in the sliding arc plasma reactor using atomic layer deposition, the blade electrode is calcined in a muffle furnace at 400-600°C.

[0051] The method for coating blade electrodes provided by this invention modifies the blade electrodes by coating their surface with a dielectric layer, thereby weakening the arc energy and reducing the plasma field temperature, thus enabling methane to be directly converted into ethylene. This method can effectively simplify the process of converting methane into olefins, and directly and efficiently convert methane into ethylene under the action of an electric field.

[0052] According to a preferred embodiment, the step of coating the blade electrode in a sliding arc plasma reactor using atomic layer deposition includes: in an atomic layer deposition apparatus...

[0053] (1) Place the coating material in the metal source tank and place the blade electrode to be coated in the reaction chamber;

[0054] (2) The metal source tank, the reaction chamber, the transport pipeline and the ALD valve are heated. The temperature of the metal source tank is 140-160℃, the temperature of the reaction chamber is 50-400℃, the temperature of the transport pipeline and the ALD valve is 180-200℃, and the reaction chamber and the transport pipeline are evacuated to a pressure of 10-200Pa.

[0055] (3) Turn on the carrier gas in the metal source tank, and the flow rate of the carrier gas is 10-200 sccm;

[0056] (4) Open the ALD valve of the metal source tank. The opening time of the ALD valve is 50-2000ms, so that the coating material enters the reaction chamber and oxygen is introduced, so that the coating material reacts with oxygen on the blade electrode surface in the reaction chamber and forms a single-layer atomic layer deposited metal oxide film.

[0057] (5) The reaction chamber is cleaned by introducing an inert gas pulse for 1-200 seconds;

[0058] (6) Repeat steps (1) to (5) to obtain the coating, each time forming a single atomic layer deposited metal oxide film, and adjusting the coating thickness by controlling the number of repetitions.

[0059] In a preferred embodiment, the method provided by the present invention can better coat the blade electrode by atomic layer deposition, and the resulting coating can more effectively regulate the arc energy, thereby improving the efficiency of direct conversion of methane into ethylene.

[0060] As previously described, a second aspect of the present invention provides a blade electrode obtained by coating using the method described in the first aspect.

[0061] As previously described, a third aspect of the present invention provides a sliding arc plasma reactor having a coaxial jacketed structure, and the reactor comprising:

[0062] The inner cylinder is provided with a reactor inlet, a side feed inlet, a lower reaction zone, and a product outlet.

[0063] An outer cylinder is nested outside the inner cylinder, and a heat-conducting medium inlet and a heat-conducting medium outlet are respectively provided on the outer cylinder;

[0064] A blade electrode sliding arc generator, comprising a gas nozzle, a blade electrode, and a base;

[0065] The side feed inlet passes through the outer cylinder and enters the inner cylinder, allowing the reaction gas to enter the inner cylinder through the side feed inlet; at least two blade electrodes are symmetrically distributed on the base of the blade electrode sliding arc generator, allowing a discharge area to be formed between the blade electrodes; the base is provided with a gas nozzle, allowing the raw material gas to enter the inner cylinder from the reactor inlet through the gas nozzle;

[0066] The blade electrode is the blade electrode described in the second aspect above.

[0067] In this invention, the symmetrical distribution is a symmetrical distribution with the central vertical axis of the base as a reference. The installation position of the blade electrode must ensure that it does not affect the discharge.

[0068] In this invention, there are no particular limitations on the shape and material of the base. It can be circular or other shapes that can achieve the aforementioned inventive objectives of this invention, and it can be insulating material or other materials that can achieve the aforementioned inventive objectives of this invention.

[0069] Preferably, the base is provided with two or six blade electrodes that are symmetrically distributed.

[0070] According to a preferred embodiment, the base of the blade electrode sliding arc generator is provided with two blade electrodes that are symmetrically distributed.

[0071] Preferably, the material forming the blade electrode is a conductive material.

[0072] More preferably, the conductive material is selected from at least one of 316L stainless steel, tungsten-cerium alloy, copper, and copper-tungsten alloy. The material forming the blade electrode can also be other conductive materials that are resistant to high temperatures and arc corrosion.

[0073] Preferably, the gas nozzle is disposed at the center of the base of the blade electrode sliding arc generator, and the gas nozzle is connected to the air inlet pipe of the reactor inlet.

[0074] In this invention, there is no particular limitation on the arrangement of the gas nozzles. One nozzle can be arranged at the center of the base or multiple nozzles can be arranged symmetrically on the base. Preferably, one nozzle is arranged at the center of the base.

[0075] Preferably, the ratio between the length L1 of the blade electrode and the diameter D1 of the inner cylinder is L1:D1 = 1:1-3, more preferably L1:D1 = 1:1-2, and even more preferably L1:D1 = 1:1-1.5.

[0076] In this invention, the length L1 of the blade electrode and the diameter D1 of the inner cylinder can both be measured in mm.

[0077] Preferably, the ratio between the length L1 of the blade electrode and the length L2 of the inner cylinder is L1:L2 = 1:1.5-6, more preferably L1:L2 = 1:2-5, and even more preferably L1:L2 = 1:2-3.

[0078] In this invention, the length L1 of the blade electrode and the length L2 of the inner cylinder can both be measured in mm.

[0079] Preferably, the ratio between the thickness L3 of the blade electrode and the length L1 of the blade electrode is L3:L1 = 1:10-50, more preferably L3:L1 = 1:20-30, and even more preferably L3:L1 = 1:20-25.

[0080] In this invention, the thickness L3 and the length L1 of the blade electrode can both be measured in mm.

[0081] Preferably, the upper end of the blade electrode is provided with a movable connecting mechanism that connects to the base, so that the blade electrode can be freely adjusted in the lower region of the base.

[0082] In this invention, there is no particular limitation on the way the movable connecting mechanism is connected to the base; it can be a fixed connection or a movable connection. The freely adjustable position refers to adjustment in various directions, not limited to... Figure 1 The specific implementation details are shown in the diagram.

[0083] More preferably, the upper end of the blade electrode is provided with a movable connecting mechanism that connects to the base, so that the position of the blade electrode can be adjusted in the vertical and horizontal directions.

[0084] Preferably, the movable connecting mechanism is vertically connected to the base.

[0085] In this invention, the movable connecting mechanism can also be connected to the base in a non-vertical manner.

[0086] Preferably, the upper end of the blade electrode is rotatably connected to the movable connecting mechanism, so that the blade electrode can rotate freely to adjust the angle.

[0087] More preferably, the upper end of the blade electrode is rotatably connected to the movable connecting mechanism, so that the blade electrode can rotate to adjust the angle with the vertical direction.

[0088] Preferably, the included angle θ between the extensions of the hypotenuses of every two blade electrodes in symmetrical positions is 10°-90°, more preferably 30°-60°.

[0089] In this invention, "every two blade electrodes in symmetrical positions" means that this invention does not limit there to only two blade electrodes in symmetrical positions, but only makes a specific limitation on the two blade electrodes in symmetrical positions.

[0090] Preferably, the ratio between the minimum spacing D2 between every two blade electrodes in symmetrical positions and the diameter D1 of the inner cylinder is D2:D1 = 1:20-100, more preferably D2:D1 = 1:30-70, and even more preferably D2:D1 = 1:35-50.

[0091] In this invention, the minimum spacing D2 refers to the distance between the two closest points of two symmetrically positioned blade electrodes. The position of the minimum spacing D2 will be different for blade electrodes of different shapes.

[0092] In this invention, the minimum spacing D2 between every two blade electrodes in the symmetrical position and the diameter D1 of the inner cylinder can both be in mm.

[0093] Preferably, the ratio between the diameter D4 of the gas nozzle and the diameter D1 of the inner cylinder is D4:D1 = 1:35-100, more preferably D4:D1 = 1:40-70, and even more preferably D4:D1 = 1:45-65.

[0094] In this invention, the diameter D4 of the gas nozzle refers to the inner diameter of the gas nozzle.

[0095] In this invention, the diameter D4 of the gas nozzle and the diameter D1 of the inner cylinder can both be measured in mm.

[0096] Preferably, the ratio between the distance L4 between the arc-starting end of the blade electrode and the outlet of the gas nozzle and the length L2 of the inner cylinder is: L4:L2 = 1:5-30, more preferably L4:L2 = 1:7-20, and even more preferably L4:L2 = 1:10-15.

[0097] In this invention, the arc-starting end of the blade electrode refers to the position of the two ends of the minimum spacing D2 on the blade electrode, and the distance L4 between the arc-starting end of the blade electrode and the outlet of the gas nozzle refers to the vertical distance between the outlet of the gas nozzle and the midpoint of the minimum spacing D2 of the two blade electrodes.

[0098] In this invention, the distance L4 between the arc-starting end of the blade electrode and the outlet of the gas nozzle and the length L2 of the inner cylinder can both be measured in mm.

[0099] The sliding arc plasma reactor provided by the present invention enables the raw material gas to pass more concentratedly through the discharge region formed by the blade electrode, thereby effectively increasing the gas flow rate through the discharge region and improving the conversion efficiency of the reactants.

[0100] Preferably, the material forming the inner cylinder is an insulating material or a conductive material with an insulating liner.

[0101] More preferably, the insulating material is selected from at least one of ordinary glass, quartz glass, and corundum.

[0102] In this invention, the material forming the inner cylinder can also be a conductive material, provided that the blade electrode avoids contact with the inner cylinder.

[0103] In this invention, there is no particular limitation on the shape of the inner cylinder, as long as it can provide a sealed space for the reactor, it can be cylindrical, rectangular or other shapes that can achieve the aforementioned inventive objectives of this invention.

[0104] Preferably, the material forming the lower reaction zone is a metallic material.

[0105] Preferably, the lower reaction zone is conical. The inventors have found that this shape is more conducive to the distribution of reactant gases.

[0106] Preferably, the lower reaction zone is a reaction zone in which a catalyst bed can be provided, and the ratio between the height L5 of the catalyst bed and the length L2 of the inner cylinder is: L5:L2 = 1:2-15, more preferably L5:L2 = 1:3-12, and even more preferably L5:L2 = 1:5-10. The height L5 of the catalyst bed is the height of the cone of the lower reaction zone.

[0107] In this invention, the height L5 of the catalyst bed is the height of the bed in the lower reaction zone where the catalyst can be added. The units for both the height L5 of the catalyst bed and the length L2 of the inner cylinder can be mm.

[0108] The sliding arc plasma reactor provided by this invention can be filled with a catalyst capable of catalyzing methane conversion, preferably in the lower reaction zone of the reactor. This invention does not impose any particular requirements on the packing volume or type of catalyst; it can be any catalyst known in the art for catalyzing methane conversion.

[0109] Preferably, the heat transfer medium inlet and the heat transfer medium outlet are respectively located at the lower and upper parts of the outer cylinder.

[0110] Preferably, the side feed inlet is located in the middle of the inner cylinder.

[0111] As previously described, a fourth aspect of the present invention provides a method for plasma conversion of methane, the method being carried out in the sliding arc plasma reactor described in the third aspect above, the method comprising:

[0112] Under plasma discharge conditions, a methane-containing feed gas is introduced into the inner cylinder of the sliding arc plasma reactor through the reactor inlet and the gas nozzle, while a hydrogen-containing reaction gas is introduced into the inner cylinder of the sliding arc plasma reactor through the side feed inlet. The feed gas then passes sequentially through the discharge region formed by the blade electrode and the lower reaction zone to carry out a methane conversion reaction. The product obtained after the reaction is led out of the sliding arc plasma reactor through the product outlet. Furthermore, the required temperature of the sliding arc plasma reactor is maintained by continuously introducing a heat-conducting medium into the outer cylinder of the sliding arc plasma reactor through the heat-conducting medium inlet and leading the heat-conducting medium out through the heat-conducting medium outlet.

[0113] The plasma conversion of methane provided by this invention does not impose any particular restrictions on the reaction conditions involved in the conversion of methane to ethylene. It can be carried out under various conditions involved in plasma conversion of methane conventionally used in the art. The embodiments section of this invention exemplarily lists the conditions for converting methane to ethylene, which should not be construed as limiting the invention by those skilled in the art.

[0114] The plasma conversion method for methane provided by this invention does not particularly limit the concentration of methane in the reaction gas at the reactor inlet. For example, the concentration of methane in the gas can be 0.01 to 100 vol%. Exemplarily, it can be 5 vol%, 10 vol%, 15 vol%, 20 vol%, 25 vol%, 30 vol%, 35 vol%, 40 vol%, 45 vol%, 50 vol%, 55 vol%, 60 vol%, 65 vol%, 70 vol%, 75 vol%, 80 vol%, 85 vol%, 90 vol%, or 95 vol%.

[0115] In this invention, after the reactive gas passes through the discharge area formed by the blade electrode, it carries the heat generated by the discharge and the reactants into the lower reaction zone. The heat generated can provide the heat required for the catalyst bed in the lower reaction zone, eliminating the need for additional heating of the catalyst bed and reducing energy consumption without affecting the conversion efficiency.

[0116] In this invention, the heat transfer medium can be raw material gas, boiling water, heat transfer oil, cooling water, etc. Using raw material gas for heat exchange can reduce the reactor temperature and effectively utilize the heat generated by the plasma, further reducing plasma energy consumption. Using boiling water for heat exchange can maintain a constant reactor temperature and generate steam as a byproduct of the heat, improving the economy of the plasma process. Heat transfer oil and cooling water are mainly used for cooling, with relatively little heat recovery and utilization. However, due to their wide applicability, they can be considered as cooling media.

[0117] In this invention, the plasma process is significantly exothermic. After a long period of operation, the heat inside the plasma cannot be dissipated. The materials of the blade electrode and the reactor wall have high temperature requirements. By cooling the reactor wall and the electrode together, the temperature of the reactor wall and the blade electrode can be effectively reduced, the rate of electrode coating erosion can be slowed down, and the working time of the plasma reactor can be increased.

[0118] The plasma conversion method for methane provided by this invention can achieve continuous and stable reaction with high reactant conversion efficiency, reduce energy consumption, effectively suppress carbon deposition, and compared with the traditional methane to olefins process, it produces no CO2, has a high ethylene yield, no risk of combustion or explosion, and is safer and more environmentally friendly.

[0119] The following combination Figure 1 The structure of a preferred embodiment of the sliding arc plasma reactor of the present invention is provided, specifically:

[0120] The reactor has a coaxial jacketed structure and includes:

[0121] The inner cylinder is provided with a reactor inlet 1, a side feed inlet 4, a lower reaction zone and a product outlet 7;

[0122] The outer cylinder is nested outside the inner cylinder, and the outer cylinder is provided with a heat-conducting medium inlet 5 and a heat-conducting medium outlet 6 respectively;

[0123] A blade electrode sliding arc generator, comprising a gas nozzle 2, a blade electrode 3, and a base 8, wherein the blade electrode is the blade electrode described in the second aspect above;

[0124] The side feed inlet 4 passes through the outer cylinder and enters the inner cylinder, allowing the reaction gas to enter the inner cylinder through the side feed inlet 4. Two blade electrodes 3 are symmetrically distributed on the base 8 of the blade electrode sliding arc generator, so that a discharge area can be formed between the blade electrodes 3. The gas nozzle 2 is located at the center of the base 8, and the gas nozzle 2 is connected to the air inlet pipe of the reactor inlet 1, so that the raw material gas can enter the inner cylinder from the reactor inlet 1 through the gas nozzle 2.

[0125] Preferably, the upper end of the blade electrode 3 is provided with a movable connecting mechanism 9 connected to the base 8, so that the position of the blade electrode 3 can be adjusted in the vertical and horizontal directions.

[0126] Preferably, the movable connecting mechanism 9 is vertically connected to the base 8.

[0127] Preferably, the upper end of the blade electrode 3 is rotatably connected to the movable connecting mechanism 9, so that the blade electrode 3 can rotate to adjust the angle with the vertical direction.

[0128] The following is a preferred embodiment of the application of the sliding arc plasma reactor described above in this invention for the conversion of methane:

[0129] Nitrogen gas is introduced into the inner cylinder of the sliding arc plasma reactor from the reactor inlet to purge air from the discharge region and to guide the gas out from the product outlet. Then, a feed gas containing methane is introduced into the inner cylinder from the reactor inlet, and a reaction gas containing hydrogen is introduced into the inner cylinder through the side feed inlet. After the feed gas flow stabilizes, a high-voltage power supply is connected, and a plasma discharge field is formed between the blade electrodes by adjusting the voltage and frequency. The feed gas sequentially passes through the discharge region formed by the blade electrodes and the lower reaction region, undergoing ionization and hydrogenation reactions respectively. The resulting product is then exited from the sliding arc plasma reactor through the product outlet. Furthermore, the required temperature of the sliding arc plasma reactor is maintained by continuously introducing heat-conducting medium into the outer cylinder through a heat-conducting medium inlet located at the lower part of the outer cylinder and by exiting the heat-conducting medium through a heat-conducting medium outlet located at the upper part of the outer cylinder.

[0130] The present invention will be described in detail below through examples.

[0131] In the following examples, unless otherwise specified, all raw materials are commercially available products.

[0132] In the following examples, methane conversion, ethylene selectivity, ethane selectivity, acetylene selectivity, C3+ hydrocarbon selectivity, and coke deposition are calculated using the following formulas:

[0133] Methane conversion rate % = (methane inlet molars - methane outlet molars) / methane inlet molars × 100%;

[0134] Ethylene selectivity % = (Ethylene export molar quantity) × 2 / (Methane import molar quantity - Methane export molar quantity) × 100%;

[0135] Ethane selectivity % = (Ethane export molar amount) × 2 / (Methane import molar amount - Methane export molar amount) × 100%;

[0136] Acetylene selectivity % = (Acetylene outlet molar amount) × 2 / (Methane inlet molar amount - Methane outlet molar amount) × 100%;

[0137] Selectivity % for hydrocarbons of C3 and above = Σ(C n (Export molar quantity) × n / (Methane import molar quantity - Methane export molar quantity) × 100%, where n = an integer from 3 to 5;

[0138] Carbon deposits % = 1 - [Σ(C n [(export molar quantity) × n / (methane import molar quantity - methane export molar quantity) × 100%], where n is an integer from 2 to 5.

[0139] Example 1

[0140] A sliding arc plasma reactor is used for the methane conversion reaction. The specific structure and structural parameters of the reactor are shown below:

[0141] The reactor has a coaxial jacketed structure and includes:

[0142] The inner cylinder is provided with a reactor inlet, a side feed inlet, a lower reaction zone, and a product outlet.

[0143] An outer cylinder is nested outside the inner cylinder, and a heat-conducting medium inlet and a heat-conducting medium outlet are respectively provided on the outer cylinder;

[0144] The blade electrode sliding arc generator includes a gas nozzle, a blade electrode, and a base. The blade electrode is coated with 200 HfO2 thin films using atomic layer deposition (ALD) on the blade surface. During coating, the entire blade electrode except for the blade surface is covered. In this embodiment and all subsequent examples, the blade surface area is the same, 27 mm². 2 ;

[0145] The side feed inlet passes through the outer cylinder and enters the inner cylinder, allowing the reaction gas to enter the inner cylinder through the side feed inlet. Two symmetrically distributed blade electrodes are arranged on the base of the blade electrode sliding arc generator, forming a discharge area between the blade electrodes. A gas nozzle is located at the center of the base, and the gas nozzle is connected to the inlet pipe of the reactor, allowing the raw material gas to enter the inner cylinder from the reactor inlet through the gas nozzle.

[0146] The upper end of the blade electrode is provided with a movable connecting mechanism that connects to the base, so that the position of the blade electrode can be adjusted in the vertical and horizontal directions; the movable connecting mechanism is vertically connected to the base; the upper end of the blade electrode and the movable connecting mechanism are rotatably connected, so that the blade electrode can rotate to adjust the angle with the vertical direction.

[0147] The material forming the blade electrode is 316L stainless steel;

[0148] The ratio between the length L1 of the blade electrode and the diameter D1 of the inner cylinder is: L1:D1 = 1:1;

[0149] The ratio of the length L1 of the blade electrode to the length L2 of the inner cylinder is: L1:L2 = 1:3;

[0150] The ratio between the thickness L3 and the length L1 of the blade electrode is: L3:L1 = 1:20;

[0151] The ratio between the minimum spacing D2 between the two blade electrodes in symmetrical positions and the diameter D1 of the inner cylinder is: D2:D1 = 1:35;

[0152] The ratio between the diameter D4 of the gas nozzle and the diameter D1 of the inner cylinder is: D4:D1 = 1:46;

[0153] The ratio between the distance L4 between the arc-starting end of the blade electrode and the outlet of the gas nozzle and the length L2 of the inner cylinder is: L4:L2 = 1:10;

[0154] The ratio between the distance L3 between the arc-starting end of the blade electrode and the outlet of the gas nozzle and the minimum spacing D2 between two symmetrically positioned blade electrodes is: L3:D2 = 1:0.2;

[0155] The included angle θ between the extensions of the hypotenuses of the two blade electrodes in symmetrical positions is 45°.

[0156] The material forming the inner cylinder is quartz glass;

[0157] The ratio of the height L5 of the catalyst bed to the length L2 of the inner cylinder is: L5:L2 = 1:7;

[0158] In this embodiment, the volume of the sliding arc plasma reactor is 3L.

[0159] The operating conditions of the sliding arc plasma reactor in this embodiment are as follows:

[0160] First, cooling water is introduced into the outer cylinder through the heat transfer medium inlet. Then, nitrogen gas is introduced into the inner cylinder through the reactor inlet for 30 minutes at an inlet flow rate of 3 L / min to replace the oxygen in the reactor. Next, a mixed gas is introduced at an inlet flow rate of 1 L / min for methane and 3 L / min for hydrogen. The power supply is turned on, and the voltage and frequency are adjusted. The voltage is adjusted to 5 kV and the frequency is adjusted to 25 kHz to start discharging. Then, the voltage is adjusted to the specified 2 kV, at which point the power is 300 W, and the reaction is carried out for 8 hours.

[0161] The exhaust gas was analyzed, and the results are shown in Table 1. The exhaust gas analysis results for the other examples are also listed in Table 1.

[0162] Example 2

[0163] This embodiment uses a sliding arc plasma reactor similar to that in Example 1 for the methane conversion reaction. The difference is that in this embodiment:

[0164] The blade electrode is coated with 400 ZrO2 thin films using atomic layer deposition.

[0165] Everything else is the same as in Example 1.

[0166] Example 3

[0167] This embodiment uses a sliding arc plasma reactor similar to that in Example 1 for the methane conversion reaction. The difference is that in this embodiment:

[0168] The blade electrode is coated with 600 La2O3 thin films using atomic layer deposition.

[0169] Everything else is the same as in Example 1.

[0170] Example 4

[0171] This embodiment uses a sliding arc plasma reactor similar to that in Example 1 for the methane conversion reaction. The difference is that in this embodiment:

[0172] The blade electrode is coated with 200 Ta2O5 thin films using atomic layer deposition.

[0173] Everything else is the same as in Example 1.

[0174] Example 5

[0175] This embodiment uses a sliding arc plasma reactor similar to that in Example 1 for the methane conversion reaction. The difference is that in this embodiment:

[0176] The blade electrode is coated with 200 SnO2 thin films using atomic layer deposition.

[0177] Everything else is the same as in Example 1.

[0178] Example 6

[0179] This embodiment uses a sliding arc plasma reactor similar to that in Example 1 for the methane conversion reaction. The difference is that in this embodiment:

[0180] The blade electrode is coated with 200 ZnO thin films using atomic layer deposition.

[0181] Everything else is the same as in Example 1.

[0182] Example 7

[0183] This embodiment uses a sliding arc plasma reactor similar to that in Example 1 for the methane conversion reaction. The difference is that in this embodiment:

[0184] The blade electrode is coated with 200 TiO2 thin films using atomic layer deposition.

[0185] Everything else is the same as in Example 1.

[0186] Example 8

[0187] This embodiment uses a sliding arc plasma reactor similar to that in Example 1 for the methane conversion reaction. The difference is that in this embodiment:

[0188] The blade electrode is coated with 200 Y2O3 thin films using atomic layer deposition.

[0189] Everything else is the same as in Example 1.

[0190] Comparative Example 1

[0191] This comparative example uses a sliding arc plasma reactor similar to that in Example 1 for the methane conversion reaction. The difference is that in this comparative example:

[0192] The blade electrode was not coated;

[0193] Everything else is the same as in Example 1.

[0194] Comparative Example 2

[0195] This comparative example uses a sliding arc plasma reactor similar to that in Example 1 for the methane conversion reaction. The difference is that in this comparative example:

[0196] The blade electrode is coated using existing chemical electroplating technology. The coating material is copper, and the specific conditions are: copper nitrate concentration 0.1 mol / mL, voltage 0.3V, pH=6.7, temperature 25℃, electroplating time 300s. During coating, the blade electrode is completely covered except for the blade surface.

[0197] Everything else is the same as in Example 1.

[0198] Table 1

[0199]

[0200]

[0201] As can be seen from the above results, the solution provided by the present invention modifies the blade electrode by coating the surface of the blade electrode with a dielectric layer, thereby weakening the arc energy and reducing the plasma field temperature. This effectively simplifies the process of converting methane to olefins, and directly and efficiently converts methane into ethylene under the action of an electric field. Furthermore, the solution provided by the present invention can achieve continuous and stable reaction with high reactant conversion efficiency, reduce energy consumption, effectively suppress carbon deposition, and compared with the traditional methane to olefins process, there is no CO2 generation, the ethylene yield is high, there is no risk of combustion or explosion, and it is safer and more environmentally friendly.

[0202] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for coating blade electrodes, characterized in that, The method includes: applying a coating material to a blade electrode in a sliding arc plasma reactor using atomic layer deposition to obtain a coating layer on the surface of the blade electrode containing at least two stacked atomic layer deposited metal oxide films, the coating layer being a semiconductor material, and each of the atomic layer deposited metal oxide films being formed of the same material; the coating material being an organic compound containing a metal element; The steps for coating blade electrodes in a sliding arc plasma reactor using atomic layer deposition include: in an atomic layer deposition apparatus, (1) In the presence of carrier gas, open the ALD valve of the metal source tank so that the coating material in the metal source tank enters the oxygen-containing reaction chamber, so that the coating material reacts with oxygen on the blade electrode surface in the reaction chamber and forms a single-layer atomic layer deposited metal oxide film. (2) Repeat step (1) to obtain the coating, each time forming a single atomic layer of deposited metal oxide film, and adjust the coating thickness by controlling the number of repetitions.

2. The method according to claim 1, wherein, The semiconductor material is selected from at least one of metal oxides.

3. The method according to claim 2, wherein, The semiconductor material is selected from at least one of Al2O3, ZrO2, SnO2, ZnO, HfO2, TiO2, La2O3, Ta2O5, and Y2O3.

4. The method according to any one of claims 1-3, wherein, In step (1), the temperature of the metal source tank is 140-160℃, the temperature of the reaction chamber is 50-400℃, and the temperature of the transport pipeline and the ALD valve is 180-200℃.

5. The method according to claim 4, wherein, In step (1), the reaction chamber and the transport pipeline are evacuated to a pressure of 10-200 Pa.

6. The method according to any one of claims 1-3, wherein, In step (1), the flow rate of the carrier gas is 10-200 sccm.

7. The method according to any one of claims 1-3, wherein, In step (1), the opening time of the ALD valve is 50-2000ms.

8. The method according to any one of claims 1-3, wherein, In step (1), an inert gas pulse is also introduced to clean the reaction chamber.

9. The method according to claim 8, wherein, The cleaning time is 1-200 seconds.

10. A blade electrode obtained by coating using the method described in any one of claims 1-9.

11. A sliding arc plasma reactor, characterized in that, The reactor has a coaxial jacketed structure and includes: The inner cylinder is provided with a reactor inlet (1), a side feed inlet (4), a lower reaction zone and a product outlet (7). The outer cylinder is nested outside the inner cylinder, and the outer cylinder is provided with a heat-conducting medium inlet (5) and a heat-conducting medium outlet (6). Blade electrode sliding arc generator, the blade electrode sliding arc generator includes a gas nozzle (2), a blade electrode (3) and a base (8); The side feed inlet (4) passes through the outer cylinder and enters the inner cylinder, allowing the reaction gas to enter the inner cylinder through the side feed inlet (4); at least two blade electrodes (3) are symmetrically distributed on the base (8) of the blade electrode sliding arc generator, so that a discharge area can be formed between the blade electrodes (3); the gas nozzle (2) is provided on the base (8), allowing the raw material gas to enter the inner cylinder from the reactor inlet (1) through the gas nozzle (2); The blade electrode is the blade electrode described in claim 10.

12. The sliding arc plasma reactor according to claim 11, wherein, The base (8) is provided with two or six blade electrodes (3) symmetrically distributed.

13. The sliding arc plasma reactor according to claim 11 or 12, wherein, The material forming the blade electrode (3) is a conductive material.

14. The sliding arc plasma reactor according to claim 13, wherein, The conductive material is selected from at least one of 316L stainless steel, tungsten-cerium alloy, copper, and copper-tungsten alloy.

15. The sliding arc plasma reactor according to claim 11 or 12, wherein, The gas nozzle (2) is located at the center of the base (8) of the blade electrode sliding arc generator, and the gas nozzle (2) is connected to the air inlet pipe of the reactor inlet (1).

16. The sliding arc plasma reactor according to claim 11 or 12, wherein, The ratio between the length L1 of the blade electrode (3) and the diameter D1 of the inner cylinder is: L1:D1=1:1-3.

17. The sliding arc plasma reactor according to claim 16, wherein, The ratio between the length L1 of the blade electrode (3) and the diameter D1 of the inner cylinder is: L1:D1=1:1-2.

18. The sliding arc plasma reactor according to claim 17, wherein, The ratio between the length L1 of the blade electrode (3) and the diameter D1 of the inner cylinder is: L1:D1=1:1-1.

5.

19. The sliding arc plasma reactor according to claim 11 or 12, wherein, The ratio between the length L1 of the blade electrode (3) and the length L2 of the inner cylinder is: L1:L2=1:1.5-6.

20. The sliding arc plasma reactor according to claim 19, wherein, The ratio between the length L1 of the blade electrode (3) and the length L2 of the inner cylinder is: L1:L2=1:2-5.

21. The sliding arc plasma reactor according to claim 20, wherein, The ratio between the length L1 of the blade electrode (3) and the length L2 of the inner cylinder is: L1:L2=1:2-3.

22. The sliding arc plasma reactor according to claim 11 or 12, wherein, The ratio between the thickness L3 of the blade electrode (3) and the length L1 of the blade electrode (3) is: L3:L1=1:10-50.

23. The sliding arc plasma reactor according to claim 22, wherein, The ratio between the thickness L3 of the blade electrode (3) and the length L1 of the blade electrode (3) is: L3:L1=1:20-30.

24. The sliding arc plasma reactor according to claim 23, wherein, The ratio between the thickness L3 of the blade electrode (3) and the length L1 of the blade electrode (3) is: L3:L1=1:20-25.

25. The sliding arc plasma reactor according to claim 11 or 12, wherein, The upper end of the blade electrode (3) is provided with a movable connecting mechanism (9) that is connected to the base (8), so that the blade electrode (3) can be freely adjusted in the lower region of the base (8).

26. The sliding arc plasma reactor according to claim 25, wherein, The upper end of the blade electrode (3) is provided with a movable connecting mechanism (9) connected to the base (8), so that the position of the blade electrode (3) can be adjusted in the vertical and horizontal directions.

27. The sliding arc plasma reactor according to claim 25, wherein, The movable connecting mechanism (9) is vertically connected to the base (8).

28. The sliding arc plasma reactor according to claim 25, wherein, The upper end of the blade electrode (3) is rotatably connected to the movable connecting mechanism (9), so that the blade electrode (3) can rotate freely to adjust the angle.

29. The sliding arc plasma reactor according to claim 28, wherein, The upper end of the blade electrode (3) is rotatably connected to the movable connecting mechanism (9), so that the blade electrode (3) can rotate to adjust the angle with the vertical direction.

30. The sliding arc plasma reactor according to claim 11 or 12, wherein, The included angle θ between the extensions of the hypotenuses of every two blade electrodes (3) in symmetrical positions is 10°-90°.

31. The sliding arc plasma reactor according to claim 30, wherein, The included angle θ between the extensions of the hypotenuses of every two blade electrodes (3) in symmetrical positions is 30°-60°.

32. The sliding arc plasma reactor according to claim 11 or 12, wherein, The ratio between the minimum spacing D2 between every two blade electrodes (3) in symmetrical positions and the diameter D1 of the inner cylinder is: D2:D1=1:20-100.

33. The sliding arc plasma reactor according to claim 32, wherein, The ratio between the minimum spacing D2 between every two blade electrodes (3) in symmetrical positions and the diameter D1 of the inner cylinder is: D2:D1=1:30-70.

34. The sliding arc plasma reactor according to claim 33, wherein, The ratio between the minimum spacing D2 between every two blade electrodes (3) in symmetrical positions and the diameter D1 of the inner cylinder is: D2:D1=1:35-50.

35. The sliding arc plasma reactor according to claim 11 or 12, wherein, The ratio between the diameter D4 of the gas nozzle (2) and the diameter D1 of the inner cylinder is: D4:D1=1:35-100.

36. The sliding arc plasma reactor according to claim 35, wherein, The ratio between the diameter D4 of the gas nozzle (2) and the diameter D1 of the inner cylinder is: D4:D1=1:40-70.

37. The sliding arc plasma reactor according to claim 36, wherein, The ratio between the diameter D4 of the gas nozzle (2) and the diameter D1 of the inner cylinder is: D4:D1=1:45-65.

38. The sliding arc plasma reactor according to claim 11 or 12, wherein, The ratio between the distance L4 between the arc-starting end of the blade electrode (3) and the outlet of the gas nozzle (2) and the length L2 of the inner cylinder is: L4:L2=1:5-30.

39. The sliding arc plasma reactor according to claim 38, wherein, The ratio between the distance L4 between the arc-starting end of the blade electrode (3) and the outlet of the gas nozzle (2) and the length L2 of the inner cylinder is: L4:L2=1:7-20.

40. The sliding arc plasma reactor according to claim 39, wherein, The ratio between the distance L4 between the arc-starting end of the blade electrode (3) and the outlet of the gas nozzle (2) and the length L2 of the inner cylinder is: L4:L2=1:10-15.

41. The sliding arc plasma reactor according to claim 11 or 12, wherein, The material forming the inner cylinder is an insulating material or a conductive material with an insulating lining.

42. The sliding arc plasma reactor according to claim 41, wherein, The insulating material is selected from at least one of ordinary glass, quartz glass, and corundum.

43. The sliding arc plasma reactor according to claim 11 or 12, wherein, The material forming the lower reaction zone is a metallic material.

44. The sliding arc plasma reactor according to claim 43, wherein, The lower reaction zone is cone-shaped.

45. The sliding arc plasma reactor according to claim 11 or 12, wherein, The lower reaction zone is a reaction zone in which a catalyst bed can be provided. The ratio between the height L5 of the catalyst bed and the length L2 of the inner cylinder is: L5:L2=1:2-15. The height L5 of the catalyst bed is the height of the cone of the lower reaction zone.

46. ​​The sliding arc plasma reactor according to claim 45, wherein, The lower reaction zone is a reaction zone in which a catalyst bed can be provided. The ratio between the height L5 of the catalyst bed and the length L2 of the inner cylinder is: L5:L2=1:3-12. The height L5 of the catalyst bed is the height of the cone of the lower reaction zone.

47. The sliding arc plasma reactor according to claim 46, wherein, The lower reaction zone is a reaction zone in which a catalyst bed can be provided. The ratio between the height L5 of the catalyst bed and the length L2 of the inner cylinder is: L5:L2=1:5-10. The height L5 of the catalyst bed is the height of the cone of the lower reaction zone.

48. The sliding arc plasma reactor according to claim 11 or 12, wherein, The heat-conducting medium inlet (5) and the heat-conducting medium outlet (6) are respectively located at the lower and upper parts of the outer cylinder.

49. The sliding arc plasma reactor according to claim 11 or 12, wherein, The side feed inlet (4) is located in the middle of the inner cylinder.

50. A method for plasma-converted methane, characterized in that, The method is carried out in the sliding arc plasma reactor according to any one of claims 11-49, and the method includes: Under plasma discharge conditions, a raw material gas containing methane is introduced into the inner cylinder of the sliding arc plasma reactor through the reactor inlet (1) and the gas nozzle (2), and a reaction gas containing hydrogen is introduced into the inner cylinder of the sliding arc plasma reactor through the side feed inlet (4). The raw material gas passes sequentially through the discharge area formed by the blade electrode (3) and the lower reaction zone to carry out the methane conversion reaction. The product obtained after the reaction is led out of the sliding arc plasma reactor through the product outlet (7). Furthermore, the temperature required for the sliding arc plasma reactor is maintained by continuously introducing a heat-conducting medium into the outer cylinder of the sliding arc plasma reactor through the heat-conducting medium inlet (5) and leading out the heat-conducting medium through the heat-conducting medium outlet (6).

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