Method for converting methane to acetylene using plasma

Abstract

The present application relates to the field of plasma, and discloses a method for converting methane into acetylene by plasma, which is implemented in a sliding arc plasma reactor, wherein the sliding arc plasma reactor comprises a reactor inlet (1), a blade electrode sliding arc generator and a product outlet (4), the blade electrode sliding arc generator comprises a gas nozzle (2), a blade electrode (3) and a base (5), and at least two blade electrodes (3) are symmetrically arranged on the base (5). The method for converting methane into acetylene by plasma can significantly improve the conversion rate of methane, reduce energy consumption, improve the selectivity of acetylene in the product, significantly reduce carbon deposition, and has no CO2 generation, no risk of combustion and explosion, and is more safe and environmentally friendly compared with traditional processes.

Description

Technical Field

[0001] This invention relates to the field of plasma, and more specifically to a method for converting methane into acetylene using plasma. Background Technology

[0002] Plasma technology, a new technology that emerged in the 1960s, can generate highly reactive particles, making many chemically inert substances more reactive and leading to its increasing application in the chemical field. In the 1980s, my country gradually began research on plasma methane conversion technology.

[0003] CN1360008A, Tianjin University disclosed a method for preparing gasoline by plasma conversion of methane and carbon dioxide, in which CO2 is added as another reactant and gasoline is the main product.

[0004] CN1552680A discloses a method for producing acetylene by thermal plasma pyrolysis of methane-containing gas, which mainly uses methane as raw material and acetylene as the main by-product. This patent expired in 2012.

[0005] CN100999432A discloses a method for the catalytic plasma conversion of ionic liquids to C2 hydrocarbons from methane. This patent expired in 2015.

[0006] Southwest Chemical Research and Design Institute has announced a series of patented technologies for plasma cracking of methane (CN210367505U, CN109294284A, CN106478332A, CN101921163A), which are mainly aimed at developing processes for plasma conversion of methane to produce carbon black or acetylene and hydrogen, with a greater emphasis on process design and optimization.

[0007] Tsinghua University, Taiyuan University of Technology, and Xinjiang Tianye Group have jointly developed a plasma pyrolysis coal-to-acetylene process (CN203582763U, CN102068953A, CN101734620A, CN101550057A, CN101734995A, CN1613839A). 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.

[0008] Zhejiang University has primarily developed methods for online plasma decoupling (CN104056828A, CN104056829A), which can introduce CO2 or H2 to remove carbon deposits on the electrode surface. They have also developed a rotating arc plasma method for pyrolyzing methane to produce acetylene (CN103333044A, CN101844744A), where the working gas rotates into the discharge gap, and an external magnetic field drives the process, resulting in millisecond-level pyrolysis.

[0009] Analysis of foreign literature and patents revealed that the hydrocarbon products formed by plasma conversion of methane are mainly divided into two categories: one is mainly alkanes such as ethane, and the other is mainly acetylene.

[0010] 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.

[0011] 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.

[0012] Building upon the aforementioned technologies, a series of "warm" plasma technologies and "cold" plasma technologies have been gradually 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. This process is currently still under exploration.

[0013] RUEANGJITT N et al. (Non-oxidative reforming of methane in a mini-gliding arc discharge reactor: Effects of feed methane concentration, feed flow rate, electrode gap distance, residence time, and catalyst distance[J]. Plasma ChemPlasma Process, 2011, 31(4): 517-534.) used a blade-type sliding arc to convert methane, with acetylene as the main product. Under power conditions of 110-190W, the methane conversion rate was 40%-50%, and the C2H2 selectivity was 20%.

[0014] Rueangjitt et al. (Plasma-catalytic reforming of methane in AC microsizedgliding arc discharge: Effects of input power, reactor thickness, and catalyst existence[J]. Chem Eng J, 2009, 155(3): 874-80.) conducted a study on methane cracking for hydrogen production under an argon atmosphere using a blade-type sliding arc, investigating the effects of input energy, reactor width, and catalyst (Ni / Al2O3-SiO2) addition on the reaction efficiency. With increasing input energy or reactor width, the methane conversion rate gradually increased, reaching a maximum of approximately 45%, while the product selectivity remained largely unchanged, mainly consisting of acetylene and hydrogen. The addition of the catalyst increased the methane conversion rate by about 5%, but had little effect on the product selectivity. Summary of the Invention

[0015] The purpose of this invention is to overcome the shortcomings of existing plasma technology in the low conversion efficiency of methane to acetylene.

[0016] To achieve the above objectives, the present invention provides a method for plasma conversion of methane to acetylene, the method being carried out in a sliding arc plasma reactor, the sliding arc plasma reactor comprising a reactor inlet, a blade electrode sliding arc generator and a product outlet, the blade electrode sliding arc generator comprising a gas nozzle, a blade electrode and a base;

[0017] The blade electrode sliding arc generator has at least two symmetrically distributed blade electrodes on its base, allowing a discharge region to be formed between the blade electrodes. A gas nozzle is provided on the base, enabling the reaction gas to enter the sliding arc plasma reactor from the reactor inlet through the gas nozzle.

[0018] The blade electrode is a planar sheet structure, and the sheet structures of every two blade electrodes are symmetrically distributed and correspond to each other so that discharge can occur.

[0019] The method includes: under plasma discharge conditions, introducing a methane-containing reaction gas into the sliding arc plasma reactor through the reactor inlet and the gas nozzle, so that the reaction gas passes through the discharge region formed by the blade electrode to carry out a methane conversion reaction, and the product obtained after the reaction is led out of the sliding arc plasma reactor through the product outlet.

[0020] The conditions for the methane conversion reaction include: a discharge voltage U1 of 1.0-5.0 kV and a discharge current of 100-3000 mA; the ratio between the flow rate V1 of the reaction gas at the minimum distance D2 between every two blade electrodes in symmetrical positions and the discharge voltage U1 is: V1:U1 = 50-100:1.

[0021] Compared with the prior art, the solution provided by the present invention has at least the following advantages:

[0022] (1) The plasma conversion method for methane to acetylene provided by the present invention uses blade electrodes to form a discharge region and matches and controls the discharge parameters, which can improve the quality of discharge arc formation and thus increase the volume of the effective discharge channel, thereby achieving efficient conversion of methane to acetylene.

[0023] (2) The plasma conversion method for methane to acetylene 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 traditional processes, there is no CO2 generation, no risk of combustion and explosion, and it is safer and more environmentally friendly.

[0024] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a preferred embodiment of the sliding arc plasma reactor used in the plasma conversion of methane to acetylene method provided by the present invention.

[0026] Explanation of reference numerals in the attached figures

[0027] 1 Reactor inlet 2 Gas nozzle

[0028] 3 Blade electrode 4 Product outlet

[0029] 5. Base; 6. Movable connecting mechanism Detailed Implementation

[0030] 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.

[0031] As mentioned above, the present invention provides a method for plasma conversion of methane to acetylene, which is carried out in a sliding arc plasma reactor. The sliding arc plasma reactor includes a reactor inlet, a blade electrode sliding arc generator, and a product outlet. The blade electrode sliding arc generator includes a gas nozzle, a blade electrode, and a base.

[0032] The blade electrode sliding arc generator has at least two symmetrically distributed blade electrodes on its base, allowing a discharge region to be formed between the blade electrodes. A gas nozzle is provided on the base, enabling the reaction gas to enter the sliding arc plasma reactor from the reactor inlet through the gas nozzle.

[0033] The blade electrode is a planar sheet structure, and the sheet structures of every two blade electrodes are symmetrically distributed and correspond to each other so that discharge can occur.

[0034] The method includes: under plasma discharge conditions, introducing a methane-containing reaction gas into the sliding arc plasma reactor through the reactor inlet and the gas nozzle, so that the reaction gas passes through the discharge region formed by the blade electrode to carry out a methane conversion reaction, and the product obtained after the reaction is led out of the sliding arc plasma reactor through the product outlet.

[0035] The conditions for the methane conversion reaction include: a discharge voltage U1 of 1.0-5.0 kV and a discharge current of 100-3000 mA; the ratio between the flow rate V1 of the reaction gas at the minimum distance D2 between every two blade electrodes in symmetrical positions and the discharge voltage U1 is: V1:U1 = 50-100:1.

[0036] Preferably, in this invention, the symmetrical distribution is symmetrical about the central vertical axis of the base. The installation position of the blade electrode does not affect the discharge.

[0037] 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.

[0038] Preferably, the conditions for the methane conversion reaction include: a discharge voltage U1 of 2.0-5.0 kV and a discharge current of 1000-3000 mA.

[0039] Preferably, the ratio between the flow rate V1 of the reaction gas at the minimum spacing D2 between every two blade electrodes in symmetrical positions and the discharge voltage U1 is: V1:U1 = 50-80:1, more preferably V1:U1 = 60-80:1.

[0040] In this invention, the velocity V1 of the reaction gas at the minimum spacing D2 between every two blade electrodes in symmetrical positions can be in m / s, and the discharge voltage U1 can be in kV.

[0041] Preferably, the base of the blade electrode sliding arc generator is provided with two or six blade electrodes that are symmetrically distributed.

[0042] According to a preferred embodiment, the base of the blade electrode sliding arc generator is provided with two blade electrodes that are symmetrically distributed.

[0043] 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.

[0044] 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.

[0045] Preferably, the material forming the gas nozzle is selected from at least one of conductive materials and insulating materials.

[0046] More preferably, the material forming the gas nozzle is an insulating material.

[0047] According to a preferred embodiment, the material forming the gas nozzle is a conductive material, and the outlet position of the gas nozzle does not overlap with the blade electrode in the vertical direction.

[0048] Preferably, the material forming the blade electrode is a conductive material.

[0049] More preferably, the conductive material is selected from at least one of 316L stainless steel, tungsten-cerium alloy, nickel-chromium alloy, cobalt-chromium-nickel alloy, cobalt-nickel-copper alloy, cobalt-copper alloy, cobalt-nickel alloy, and graphite. The material forming the blade electrode can also be other conductive materials that are resistant to high temperatures and arc corrosion.

[0050] Preferably, the blade electrode is connected to the base via a movable connection mechanism, allowing the blade electrode to be freely adjusted in the lower region of the base.

[0051] 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.

[0052] More preferably, the blade electrode is connected to the base via a movable connection mechanism, allowing the blade electrode to be adjusted in both vertical and horizontal directions.

[0053] Preferably, the movable connecting mechanism is vertically connected to the base.

[0054] In this invention, the movable connecting mechanism can also be connected to the base in a non-vertical manner.

[0055] Preferably, the blade electrode and the movable connection mechanism are rotatably connected, allowing the blade electrode to rotate freely to adjust the angle.

[0056] More preferably, the blade electrode and the movable connection mechanism are rotatably connected, so that the blade electrode can rotate to adjust the angle with the vertical direction.

[0057] 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.

[0058] Preferably, the included angle θ between the extensions of the tangents at the midpoints of the arc edges of every two blade electrodes in symmetrical positions is 5°-160°, more preferably 10°-90°, and even more preferably 30°-60°.

[0059] The sliding arc plasma reactor used in the method provided by this 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.

[0060] Preferably, the material forming the outer cylinder of the sliding arc plasma reactor is selected from at least one of insulating materials, conductive materials, and conductive materials with an insulating liner.

[0061] More preferably, the material forming the outer cylinder of the sliding arc plasma reactor is an insulating material or a conductive material with an insulating liner.

[0062] More preferably, the insulating material is selected from at least one of ordinary glass, quartz glass, and corundum.

[0063] In this invention, provided that the blade electrode avoids contact with the outer cylinder of the sliding arc plasma reactor, the material forming the outer cylinder can also be a conductive material.

[0064] In this invention, there is no particular limitation on the shape of the outer cylinder of the sliding arc plasma reactor, 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.

[0065] Preferably, the material forming the bottom of the sliding arc plasma reactor is a metallic material.

[0066] Preferably, the bottom is conical. The inventors have found that this shape is more conducive to the distribution of reactant gases.

[0067] The plasma conversion method for methane to acetylene provided by this invention can achieve continuous and stable reaction with high reactant conversion efficiency. Compared with traditional processes, it produces no CO2 and has no risk of combustion or explosion, making it safer and more environmentally friendly.

[0068] The aforementioned plasma conversion method for methane to acetylene provided by this invention uses a blade electrode to form a discharge region, which is matched and controlled with the discharge parameters. This improves the quality of the discharge arc and thus increases the effective discharge channel volume, achieving efficient conversion of methane to acetylene.

[0069] The plasma conversion method for methane to acetylene 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%, and exemplaryly, 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%.

[0070] The following combination Figure 1 A preferred embodiment of the structure of the sliding arc plasma reactor for applying the method of the present invention is provided, specifically:

[0071] The reactor includes a reactor inlet 1, a blade electrode sliding arc generator and a product outlet 4. The blade electrode sliding arc generator includes a gas nozzle 2, a blade electrode 3, a base 5 and a movable connection mechanism 6.

[0072] The blade electrode sliding arc generator has two symmetrically distributed blade electrodes 3 on its base 5, which allows a discharge region to be formed between the blade electrodes 3. The base 5 has a gas nozzle 2 at its center, which is connected to the gas inlet pipe of the reactor inlet 1, so that the reaction gas can enter the sliding arc plasma reactor from the reactor inlet 1 through the gas nozzle 2.

[0073] Preferably, the blade electrode 3 is connected to the base 5 via a movable connecting mechanism 6, so that the position of the blade electrode 3 can be adjusted in the vertical and horizontal directions.

[0074] Preferably, the movable connecting mechanism 6 is vertically connected to the base 5.

[0075] Preferably, the blade electrode 3 is rotatably connected to the movable connecting mechanism 6, so that the blade electrode 3 can rotate to adjust the angle with the vertical direction.

[0076] 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:

[0077] Nitrogen gas is introduced into the sliding arc plasma reactor through the reactor inlet to purge air from the discharge region and guide the gas out through the product outlet. Then, a reaction gas containing methane is introduced into the sliding arc plasma reactor through the reactor inlet. After the 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 reaction gas passes through the discharge region formed by the blade electrodes, undergoing an ionization reaction. The resulting product is then guided out of the sliding arc plasma reactor through the product outlet.

[0078] The present invention will be described in detail below through examples.

[0079] In the following examples, unless otherwise specified, all raw materials are commercially available products.

[0080] In the following examples, methane conversion, ethylene selectivity, ethane selectivity, acetylene selectivity, C3+ hydrocarbon selectivity, and coke deposition are calculated using the following formulas:

[0081] Methane conversion rate % = (Amount of methane before reaction - Amount of methane after reaction) / Amount of methane before reaction × 100%;

[0082] Hydrocarbons (C n H m Product selectivity % = (C after reaction) n H m(Amount of substance) × n / (Amount of methane before reaction - Amount of methane after reaction) × 100%, where n is an integer from 2 to 5;

[0083] Carbon deposits % = 1 - Hydrocarbons (C n H m Product selectivity%, n = 2-5 integers.

[0084] Example 1

[0085] A sliding arc plasma reactor is used for the methane conversion reaction. The specific structure and structural parameters of the reactor are shown below:

[0086] The reactor includes a reactor inlet, a blade electrode sliding arc generator, and a product outlet. The blade electrode sliding arc generator includes a gas nozzle, a blade electrode, a base, and a movable connection mechanism.

[0087] The blade electrode sliding arc generator has two symmetrically distributed blade electrodes on its base, which allows a discharge region to be formed between the blade electrodes. A gas nozzle is located at the center of the base and is connected to the gas inlet pipe of the reactor inlet, so that the reaction gas can enter the sliding arc plasma reactor from the reactor inlet through the gas nozzle.

[0088] The blade electrode is connected to the base via a movable connecting mechanism, allowing the blade electrode to be adjusted in both vertical and horizontal directions; the movable connecting mechanism is vertically connected to the base; the blade electrode and the movable connecting mechanism are rotatably connected, allowing the blade electrode to rotate to adjust its angle with the vertical direction.

[0089] The material forming the blade electrode is a cobalt-nickel alloy;

[0090] The included angle θ between the extensions of the tangents at the midpoints of the arc edges of the two blade electrodes in symmetrical positions is 60°.

[0091] The outer cylinder of the sliding arc plasma reactor is made of quartz glass;

[0092] In this embodiment, the volume of the sliding arc plasma reactor is 3L.

[0093] The operating conditions of the sliding arc plasma reactor in this embodiment are as follows:

[0094] The discharge power is adjusted to 290W, the discharge frequency is 26.5kHz, the discharge current is 2500mA, and the inlet flow rate is 2.0L / min for methane and 2.0L / min for hydrogen. The ratio between the flow rate V1 of the reaction gas at the minimum distance D2 between the two blade electrodes in symmetrical positions and the discharge voltage U1 is: V1:U1=60:1.

[0095] Nitrogen gas is introduced into the reactor through the reactor inlet for 30 minutes at an inlet flow rate of 4 L / min to replace the oxygen in the reactor. Then, a mixed gas (methane at an inlet flow rate of 2.0 L / min and hydrogen at an inlet flow rate of 2.0 L / min) is introduced, the power is turned on to start discharging, and the reaction is carried out for 8 hours.

[0096] Analysis of the exhaust gas showed that the methane conversion rate was 47.5%, the acetylene selectivity was 90.7%, the ethylene selectivity was 4.9%, the C3 and above hydrocarbon selectivity was 4.4%, and there was no obvious carbon deposition.

[0097] Example 2

[0098] 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:

[0099] The material forming the blade electrode is 316L stainless steel;

[0100] The included angle θ between the extensions of the tangents at the midpoints of the arc edges of the two blade electrodes in symmetrical positions is 82°.

[0101] The outer cylinder of the sliding arc plasma reactor is made of 304 stainless steel with a quartz liner;

[0102] In this embodiment, the volume of the sliding arc plasma reactor is 4L.

[0103] In this embodiment, the discharge power is adjusted to 350W, the discharge frequency is 18.5kHz, the discharge current is 2350mA, and the gas flow rate is 1.0L / min for methane and 1.5L / min for hydrogen. The ratio between the flow rate V1 of the reaction gas at the minimum distance D2 between the two blade electrodes in symmetrical positions and the discharge voltage U1 is: V1:U1=75:1.

[0104] Nitrogen gas is introduced into the reactor through the reactor inlet for 30 minutes at a flow rate of 4 L / min to replace the oxygen in the reactor. Then, a mixed gas (methane at a flow rate of 1.0 L / min and hydrogen at a flow rate of 1.5 L / min) is introduced, the power is turned on to start discharging, and the reaction is carried out for 8 hours.

[0105] Everything else is the same as in Example 1.

[0106] Analysis of the exhaust gas showed that the methane conversion rate was 48.3%, the acetylene selectivity was 91.8%, the ethylene selectivity was 5.1%, the C3+ hydrocarbon selectivity was 3.1%, and there was no obvious carbon buildup.

[0107] Example 3

[0108] 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:

[0109] The base of the blade electrode sliding arc generator is provided with six blade electrodes symmetrically distributed, and the material forming the blade electrodes is a nickel-chromium alloy;

[0110] The included angle θ between the extensions of the tangents at the midpoints of the arc edges of the two blade electrodes in symmetrical positions is 50°.

[0111] The outer cylinder of the sliding arc plasma reactor is made of tempered glass;

[0112] In this embodiment, the volume of the sliding arc plasma reactor is 3.3L.

[0113] In this embodiment, the discharge power is adjusted to 400W, the discharge frequency is 23.7kHz, the discharge current is 2700mA, and the gas flow rate is 1.5L / min for methane and 2.5L / min for hydrogen. The ratio between the flow rate V1 of the reaction gas at the minimum distance D2 between the two blade electrodes in symmetrical positions and the discharge voltage U1 is: V1:U1=80:1.

[0114] Nitrogen gas is introduced into the reactor through the reactor inlet for 30 minutes at a flow rate of 4 L / min to replace the oxygen in the reactor. Then, a mixed gas (methane at a flow rate of 1.5 L / min and hydrogen at a flow rate of 2.5 L / min) is introduced, the power is turned on to start discharging, and the reaction is carried out for 8 hours.

[0115] Everything else is the same as in Example 1.

[0116] Analysis of the exhaust gas showed that the methane conversion rate was 58.7%, the acetylene selectivity was 92.1%, the ethylene selectivity was 4.5%, the C3 and above hydrocarbon selectivity was 3.4%, and there was no obvious carbon deposit.

[0117] Example 4

[0118] 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:

[0119] The base of the blade electrode sliding arc generator is provided with six blade electrodes symmetrically distributed, and the material forming the blade electrodes is a cobalt-nickel alloy.

[0120] The included angle θ between the extensions of the tangents at the midpoints of the arc edges of the two blade electrodes in symmetrical positions is 30°.

[0121] The outer cylinder of the sliding arc plasma reactor is made of ceramic.

[0122] In this embodiment, the volume of the sliding arc plasma reactor is 5L.

[0123] In this embodiment, the discharge power is adjusted to 250W, the discharge frequency is 25.4kHz, the discharge current is 2300mA, and the gas flow rate is 2.5L / min for methane and 2.0L / min for hydrogen. The ratio between the flow rate V1 of the reaction gas at the minimum distance D2 between the two blade electrodes in symmetrical positions and the discharge voltage U1 is: V1:U1=75:1.

[0124] Nitrogen gas is introduced into the reactor through the reactor inlet for 30 minutes at a flow rate of 4 L / min to replace the oxygen in the reactor. Then, a mixed gas (methane at a flow rate of 2.5 L / min and hydrogen at a flow rate of 2.0 L / min) is introduced, the power is turned on to start discharging, and the reaction is carried out for 8 hours.

[0125] Everything else is the same as in Example 1.

[0126] Analysis of the exhaust gas showed that the methane conversion rate was 60.4%, the acetylene selectivity was 90.4%, the ethylene selectivity was 5.4%, the C3+ hydrocarbon selectivity was 4.2%, and there was no obvious carbon buildup.

[0127] Example 5

[0128] 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:

[0129] The material forming the blade electrode is a cobalt-nickel-copper alloy;

[0130] The included angle θ between the extensions of the tangents at the midpoints of the arc edges of the two blade electrodes in symmetrical positions is 65°.

[0131] The outer cylinder of the sliding arc plasma reactor is made of 316L stainless steel with a quartz liner.

[0132] In this embodiment, the volume of the sliding arc plasma reactor is 6.2L.

[0133] In this embodiment, the discharge power is adjusted to 350W, the discharge frequency is 27.5kHz, the discharge current is 2900mA, and the gas flow rate is 1.8L / min for methane and 2.5L / min for hydrogen. The ratio between the flow rate V1 of the reaction gas at the minimum distance D2 between the two blade electrodes in symmetrical positions and the discharge voltage U1 is: V1:U1=50:1.

[0134] Nitrogen gas is introduced into the reactor through the reactor inlet for 30 minutes at a flow rate of 4 L / min to replace the oxygen in the reactor. Then, a mixed gas (methane at a flow rate of 1.8 L / min and hydrogen at a flow rate of 2.5 L / min) is introduced, the power is turned on to start discharging, and the reaction is carried out for 8 hours.

[0135] Everything else is the same as in Example 1.

[0136] Analysis of the exhaust gas showed that the methane conversion rate was 47.2%, the acetylene selectivity was 89.7%, the ethylene selectivity was 6.7%, the C3+ hydrocarbon selectivity was 3.6%, and there was no obvious carbon buildup.

[0137] Example 6

[0138] 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:

[0139] The material forming the blade electrode is a cobalt-copper alloy;

[0140] The included angle θ between the extensions of the tangents at the midpoints of the arc edges of the two blade electrodes in symmetrical positions is 55°.

[0141] The outer cylinder of the sliding arc plasma reactor is made of copper with a glass liner;

[0142] In this embodiment, the volume of the sliding arc plasma reactor is 5L.

[0143] In this embodiment, the discharge power is adjusted to 240W, the discharge frequency is 17.8kHz, the discharge current is 1500mA, and the gas flow rate is 1.0L / min for methane and 2.0L / min for hydrogen. The ratio between the flow rate V1 of the reaction gas at the minimum distance D2 between the two blade electrodes in symmetrical positions and the discharge voltage U1 is: V1:U1=72:1.

[0144] Nitrogen gas is introduced into the reactor through the reactor inlet for 30 minutes at a flow rate of 4 L / min to replace the oxygen in the reactor. Then, a mixed gas (methane at a flow rate of 1.0 L / min and hydrogen at a flow rate of 2.0 L / min) is introduced, the power is turned on to start discharging, and the reaction is carried out for 8 hours.

[0145] Everything else is the same as in Example 1.

[0146] Analysis of the exhaust gas showed that the methane conversion rate was 49.7%, the acetylene selectivity was 90.4%, the ethylene selectivity was 5.5%, the C3+ hydrocarbon selectivity was 4.1%, and there was no obvious carbon buildup.

[0147] Comparative Example 1

[0148] 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:

[0149] The material forming the blade electrode is 316L stainless steel. The specific references for the properties and parameters of the blade electrode are as follows: Zhong Li et al., "Sliding Arc Discharge Plasma Reforming of Methane to Syngas", Journal of Zhejiang University (Engineering Science Edition) (2010).

[0150] In this comparative example, the volume of the sliding arc plasma reactor is 2L.

[0151] In this comparative example, the discharge power was adjusted to 300W, the voltage was 3.0kV, the discharge frequency was 22.3kHz, and the inlet flow rate was 1L / min for methane and 3L / min for hydrogen.

[0152] Nitrogen gas is introduced into the reactor through the reactor inlet for 30 minutes at a flow rate of 3 L / min to replace the oxygen in the reactor. Then, a mixed gas (methane 1 L / min and hydrogen 3 L / min) is introduced. The power is turned on, and the voltage and frequency are adjusted. The voltage is adjusted to 2.0 kV and the frequency is adjusted to 22.3 kHz to start discharging. The voltage is then adjusted to the specified 3.0 kV, at which point the power is 300 W, and the reaction is carried out for 8 hours.

[0153] Everything else is the same as in Example 1.

[0154] Analysis of the exhaust gas revealed the following results: methane conversion rate of 23.7%, acetylene selectivity of 56.2%, ethylene selectivity of 2.3%, ethane selectivity of 1.6%, C3+ hydrocarbon selectivity of 0.5%, and carbon deposition of 39.4%.

[0155] The results above demonstrate that the method provided by this invention significantly improves methane conversion efficiency, reduces energy consumption, enhances acetylene selectivity in the products, and significantly reduces carbon deposition compared to existing technologies. Furthermore, the method provided by this invention enables continuous and stable reaction at high reactant conversion efficiency, and compared to traditional processes, it generates no CO2, eliminates the risk of combustion and explosion, and is therefore safer and more environmentally friendly.

[0156] 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 plasma conversion of methane to acetylene, characterized in that, The method is implemented in a sliding arc plasma reactor, which includes a reactor inlet (1), a blade electrode sliding arc generator and a product outlet (4). The blade electrode sliding arc generator includes a gas nozzle (2), a blade electrode (3) and a base (5). The blade electrode sliding arc generator has at least two symmetrically distributed blade electrodes (3) on its base (5), allowing a discharge region to be formed between the blade electrodes (3); the base (5) has a gas nozzle (2) that allows the reaction gas to enter the sliding arc plasma reactor from the reactor inlet (1) through the gas nozzle (2); and The blade electrode (3) is a planar sheet structure, and the sheet structures of every two blade electrodes (3) are symmetrically distributed and correspond to each other so that discharge can occur. The method includes: under plasma discharge conditions, introducing a methane-containing reaction gas into the sliding arc plasma reactor through the reactor inlet (1) and the gas nozzle (2), so that the reaction gas passes through the discharge region formed by the blade electrode (3) to carry out a methane conversion reaction, and the product obtained after the reaction is led out of the sliding arc plasma reactor through the product outlet (4); the reaction gas is a mixture of methane and hydrogen, and the concentration of methane is 30-60% by volume%. The conditions for the methane conversion reaction include: a discharge voltage U1 of 2.0-5.0 kV and a discharge current of 1000-3000 mA; the ratio between the flow rate V1 of the reaction gas at the minimum distance D2 between every two blade electrodes (3) at symmetrical positions and the discharge voltage U1 is: V1:U1=60-80:1; the unit of V1 is m / s and the unit of U1 is kV; The included angle θ between the extension lines of the tangents at the midpoints of the arc edges of every two blade electrodes (3) in symmetrical positions is 10°-90°; the bottom of the sliding arc plasma reactor is conical.

2. The method according to claim 1, wherein, The base (5) of the blade electrode sliding arc generator is provided with two blade electrodes (3) or six blade electrodes (3) symmetrically distributed.

3. The method according to claim 1 or 2, wherein, The gas nozzle (2) is located at the center of the base (5) of the blade electrode sliding arc generator, and the gas nozzle (2) is connected to the air inlet pipe of the reactor inlet (1).

4. The method according to claim 1 or 2, wherein, The material forming the gas nozzle (2) is selected from at least one of conductive materials and insulating materials.

5. The method according to claim 4, wherein, The material forming the gas nozzle (2) is an insulating material.

6. The method according to claim 1 or 2, wherein, The gas nozzle (2) is made of a conductive material, and the outlet position of the gas nozzle (2) does not overlap with the blade electrode (3) in the vertical direction.

7. The method according to claim 1 or 2, wherein, The material forming the blade electrode (3) is a conductive material.

8. The method according to claim 7, wherein, The conductive material is selected from at least one of 316L stainless steel, tungsten-cerium alloy, nickel-chromium alloy, cobalt-chromium-nickel alloy, cobalt-nickel-copper alloy, cobalt-copper alloy, cobalt-nickel alloy, and graphite.

9. The method according to claim 1 or 2, wherein, The blade electrode (3) is connected to the base (5) via a movable connection mechanism (6), so that the blade electrode (3) can be freely adjusted in the area below the base (5).

10. The method according to claim 9, wherein, The blade electrode (3) is connected to the base (5) via a movable connecting mechanism (6), so that the position of the blade electrode (3) can be adjusted in the vertical and horizontal directions.

11. The method according to claim 9, wherein, The movable connecting mechanism (6) is vertically connected to the base (5).

12. The method according to any one of claims 9-11, wherein, The blade electrode (3) is rotatably connected to the movable connection mechanism (6), allowing the blade electrode (3) to rotate freely to adjust the angle.

13. The method according to claim 12, wherein, The blade electrode (3) is rotatably connected to the movable connection mechanism (6), so that the blade electrode (3) can rotate to adjust the angle with the vertical direction.

14. The method according to claim 1 or 2, wherein, The included angle θ between the extensions of the tangents at the midpoints of the arc edges of every two blade electrodes (3) in symmetrical positions is 30°-60°.

15. The method according to claim 1 or 2, wherein, The material forming the outer cylinder of the sliding arc plasma reactor is selected from at least one of insulating materials, conductive materials, and conductive materials with an insulating liner.

16. The method according to claim 15, wherein, The outer cylinder of the sliding arc plasma reactor is made of an insulating material or a conductive material with an insulating liner.

17. The method according to claim 1 or 2, wherein, The material forming the bottom of the sliding arc plasma reactor is a metallic material.

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