A green electricity coupled wellhead skid-mounted plasma catalytic methane direct oil production system and method

Abstract

A kind of green electricity coupling wellhead pry-mounted plasma catalytic methane direct oil production system and method, belong to natural gas production conversion and resource recycling technical field.The system includes pretreatment module, gas buffer and circulation module, plasma catalytic reaction module, condensation separation module, circulation loop and green power supply module;Wellhead gas is sent into buffer tank after pretreatment, by circulating compressor into plasma catalytic reactor, under the action of green electricity driven dielectric barrier discharge and hierarchical porous TiO2 / SiO2 Catalyst, methane is directly converted into C5-C 16 Hydrocarbon liquid hydrocarbon;Reaction product is obtained by condensation separation oil, unreacted methane is returned to system again by circulation loop and reacts again.The present application combines green electricity coupling, gas circulation and pry-mounted design organically, solves the problem of low single-pass conversion rate of plasma catalysis, realizes the distributed, low-carbon and efficient oil production of remote wellhead natural gas, and has significant economic and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of natural gas production, conversion, and resource recycling technology, specifically to a wellhead skid-mounted plasma catalytic methane direct oil production system and method driven by green electricity, which is particularly suitable for distributed value-added conversion of natural gas in remote wells and scattered gas wells. Background Technology

[0002] Methane (CH4), the main component of natural gas, is directly converted into liquid hydrocarbons (gasoline fraction C5-C6). 11 Diesel fraction C 9- C 16 Methane is a crucial target for the manufacture of chemical pharmaceutical raw materials. Traditional natural gas-to-liquids (NPG) processes typically employ an indirect route, first converting methane into syngas (CO + H2) through high-temperature reforming (700-1100°C), and then obtaining liquid hydrocarbons via Fischer-Tropsch synthesis to produce chemical pharmaceutical raw materials. This process suffers from drawbacks such as long process flow, high energy consumption, and large equipment investment, making it unsuitable for distributed scenarios such as remote wells and scattered gas wells.

[0003] In recent years, plasma catalysis technology has attracted widespread attention due to its ability to activate the CH bonds of methane at ambient temperature and pressure. Studies have shown that filling a dielectric barrier discharge plasma reactor with a hierarchical porous TiO2 / SiO2 catalyst can achieve the direct non-oxidative coupling of methane to C5-C. 16 Hydrocarbons (Applied Catalysis B: Environment and Energy 386 (2026) 126437). However, the existing technologies have the following shortcomings: (1) low single-pass conversion rate (only about 11.2% for the optimal catalyst), and a large amount of methane is not converted; (2) the device design is mostly laboratory-scale and does not consider field application scenarios; (3) plasma discharge requires electrical energy input, and using grid power will increase operating costs; (4) lack of integrated and skid-mounted design for wellhead applications. Existing circulating reactor patents, such as CN117919908A, involve low-temperature plasma circulating reactors, but they are mainly used for the selective oxidation of methane to produce oxygen-containing compounds; CN201610131555.9 involves the cyclic application of methane oxygen-free aromatization, but neither of them solves the problem of wellhead application and green electricity coupling. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, such as low single-pass conversion rate, high energy consumption cost, and difficulty in field application, this paper provides a green-electric coupling wellhead skid-mounted plasma catalytic methane direct oil production system and method to achieve efficient, low-carbon, distributed value-added conversion of natural gas in remote wellheads.

[0005] The technical solution provided by this invention is: a green-electric coupling wellhead skid-mounted plasma catalytic methane direct oil production system, including a pretreatment module, a gas buffer and circulation module, a plasma catalytic reaction module, a condensation separation module, and a green-electric power supply module;

[0006] The pretreatment module is connected to the wellhead gas production pipeline and is used to filter, dry, and regulate the pressure of the gas coming from the wellhead.

[0007] The gas buffering and circulation module includes a buffer tank, a circulation compressor, and a circulation loop. The inlet of the buffer tank is connected to the outlet of the pretreatment module, and the inlet of the circulation compressor is connected to the outlet of the buffer tank. The circulation loop connects the gas phase outlet of the condensation separation module to the circulation inlet of the buffer tank.

[0008] The plasma catalytic reaction module is a dielectric barrier discharge reactor, whose inlet is connected to the outlet of the circulating compressor. The dielectric barrier discharge reactor is filled with a hierarchical porous TiO2 / SiO2 catalyst, and the high-voltage electrode of the dielectric barrier discharge reactor is connected to the green power supply module.

[0009] The condensation separation module is connected to the gas outlet of the plasma catalytic reaction module and is used to cool the reaction products to below 10°C to separate them into liquid hydrocarbon products.

[0010] The green electricity power supply module is connected to the electrodes of the plasma catalytic reaction module to provide renewable energy power to drive plasma discharge.

[0011] The above-mentioned hierarchical porous TiO2 / SiO2 catalyst has a Ti / Si molar ratio of 1:1 to pure TiO2 and has a hierarchical porous structure, wherein the macropore diameter is ≥1.34μm and the mesopore diameter is 10-20nm.

[0012] The operating parameters of the above-mentioned dielectric barrier discharge reactor are: peak voltage 10-20kV, frequency 0.5-5kHz.

[0013] The aforementioned green power supply module includes a photovoltaic power generation unit, a wind power generation unit, or a combination thereof, and is equipped with an energy storage unit.

[0014] The aforementioned circulating compressor is an explosion-proof diaphragm compressor or a liquid ring compressor.

[0015] The aforementioned condensation separation module includes a refrigeration unit and a condenser tank, with the condensation temperature controlled at 5-15°C.

[0016] A wellhead skid-mounted plasma-catalyzed direct methane-to-oil method utilizing the above system for green-electric coupling includes the following steps:

[0017] Step 1: The gas from the wellhead is filtered, dried, and pressure regulated by the pretreatment module to obtain purified methane gas;

[0018] Step 2: Purified methane gas enters a buffer tank, is pressurized by a circulating compressor, and then sent to the plasma catalytic reaction module;

[0019] Step 3: The green power supply module provides power to the plasma catalytic reaction module. Under the combined action of dielectric barrier discharge plasma and hierarchical porous TiO2 / SiO2 catalyst, methane undergoes a non-oxidative coupling reaction to generate C5-C... 16 Reaction products of hydrocarbons;

[0020] Step 4: The reaction products enter the condensation separation module and are cooled to below 10°C, where the liquid hydrocarbon products are separated and collected;

[0021] Step 5: Unreacted methane and C2-C4 light hydrocarbons are discharged from the gas phase outlet of the condensation separation module, returned to the buffer tank through the circulation loop, mixed with fresh purified methane gas, and then re-enter the reaction module for cyclic reaction.

[0022] In step 1 above, the pressure is adjusted to 0.1-0.3 MPa, and in step 2, the pressure is increased to 0.05-0.2 MPa. The reaction space velocity is controlled at 500-1000 h⁻¹ using a circulating compressor. -1 .

[0023] The above method also includes a venting step: when inert gas accumulates in the circulation loop, a portion of the circulation gas is released through a venting valve.

[0024] The above method also includes a catalyst regeneration step: when the catalyst activity decreases, the feed is stopped, regeneration gas is introduced, and in-situ regeneration is carried out with plasma assistance.

[0025] The beneficial effects of this invention are as follows:

[0026] 1. Overcoming the bottleneck of low single-pass conversion rate: By using gas circulation for multiple catalysis steps, the inherent defect of low single-pass conversion rate in plasma catalysis is overcome, increasing the total conversion rate to over 90%. This overcomes the inherent defect of low single-pass conversion rate (approximately 11.2%) in plasma catalysis technology, significantly improving raw material utilization.

[0027] 2. Achieve green electricity coupling and low-carbon operation: Utilize renewable energy sources such as photovoltaic and wind power around the well site to drive plasma reactions, converting intermittent green electricity into storable and easily transportable liquid chemical energy. This not only reduces operating electricity costs and solves the energy consumption cost problem of plasma technology, but also realizes true "green electricity to oil".

[0028] 3. Skid-mounted design, adaptable to distributed scenarios: The entire system is integrated into a skid-mounted device (size controllable within 3m×2m×2m), which can be deployed at remote wellheads and scattered gas well sites, eliminating the need for large-scale chemical plants and pipeline networks, thus solving the problem of dispersed natural gas resources. With a daily production capacity of 1000 m³... 3 Taking remote natural gas wells as an example, this system can produce about 10-15 tons of light oil per year, avoiding the venting and combustion of natural gas.

[0029] 4. Simplified process and low energy consumption: Direct methane-to-oil production is achieved at ambient temperature and pressure, eliminating the need for high-temperature reforming (700-1100°C) and syngas preparation steps, significantly simplifying the process and reducing energy consumption. Compared to traditional indirect methods, energy consumption is reduced by approximately 30-50%.

[0030] 5. High atom economy: The reaction process does not introduce oxygen, thus avoiding the generation of CO2; some of the hydrogen in methane enters the oil product and some is released as hydrogen gas, which can be further recycled and reused, maximizing resource utilization.

[0031] 6. Good catalyst stability and in-situ regeneration: TiO2 catalyst has good anti-carbon deposition performance and chain growth promotion effect. Combined with in-situ plasma regeneration technology, it can ensure long-term stable operation of the device (expected life > 1000 hours, activity recovery after regeneration > 95%).

[0032] 7. High product added value: Combining recycling processes, C5-C is achieved. 16 Highly selective formation of hydrocarbons. The generated C5-C... 16 Hydrocarbons can be used directly as components in gasoline blending or diesel fuel, have high market value, and are easy to transport. Attached Figure Description

[0033] Appendix Figure 1 This is a schematic diagram of the structure of the wellhead skid-mounted plasma catalytic methane direct oil production system with green electrical coupling according to the present invention.

[0034] Appendix Figure 2 This is a flowchart of the process for the green electrocoupling wellhead skid-mounted plasma catalytic direct methane-to-oil method of the present invention.

[0035] Appendix Figure 3 This is a schematic diagram of the plasma catalytic reaction module in this invention.

[0036] Appendix Figure 4 This is a schematic diagram of the catalyst's microstructure.

[0037] Appendix Figure 5 This is a graph showing the number of cycles versus methane conversion rate in Example 2.

[0038] Appendix Figure 6This is a graph showing the catalyst activity regeneration. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0040] Example 1:

[0041] like Figures 1-3 As shown in the figure, this embodiment provides a green electrocoupling wellhead skid-mounted plasma catalytic methane direct production system, the structure of which is as follows: Figure 1 As shown, it includes: a pretreatment module 1, a gas buffer and circulation module 2, a plasma catalytic reaction module 3, a condensation and separation module 4, and a green electricity power supply module 5;

[0042] The pretreatment module 1 is connected to the wellhead gas production pipeline and has a built-in (5μm) filter, pressure regulating valve and molecular sieve drying tower to filter, dry and regulate the pressure of the wellhead gas, removing solid impurities, water vapor and other components that are detrimental to the plasma reaction.

[0043] The gas buffer and circulation module 2 is used to buffer gas flow fluctuations, provide a stable gas source for the reaction, and return unreacted gas to the reactor after pressurization. The gas buffer and circulation module 2 includes a 50L buffer tank 21, a circulation compressor 22, and a circulation loop 6. The inlet of the buffer tank 21 is connected to the outlet of the pretreatment module 1, and the inlet of the circulation compressor 22 is connected to the outlet of the buffer tank 21. The circulation loop 6 connects the gas phase outlet of the condensation separation module 4 to the circulation inlet of the buffer tank 21. The circulation compressor 22 is an explosion-proof diaphragm compressor with an adjustable flow rate of 0-10 L / min and an outlet pressure of 0.2 MPa; it is suitable for hydrocarbon gas media. The circulation loop 6 includes a gas pipeline, a one-way valve, and a release valve; the inlet of the circulation loop 6 is connected to the gas phase outlet of the condensation separation module, and the outlet of the circulation loop 6 is connected to the circulation inlet of the buffer tank; unreacted methane and C2-C4 light hydrocarbons are returned to the system for further reaction.

[0044] The plasma catalytic reaction module 3 has a discharge gap of 3mm, a discharge region length of 300mm, and is filled with 200g of catalyst. The plasma catalytic reaction module 3 is a dielectric barrier discharge reactor (structure as follows). Figure 2 As shown), the inlet of the dielectric barrier discharge reactor is connected to the outlet of the circulating compressor 22. The reactor is filled with a hierarchical porous TiO2 / SiO2 catalyst (Ti / Si molar ratio 1:1, macropore size 1.34 μm, mesopore size 17.4 nm), with a BET specific surface area of ​​147 m². 2 / g; The high-voltage electrode of the dielectric barrier discharge reactor is connected to the green power supply module 5; The plasma catalytic reaction module 3, under the synergistic effect of plasma and catalyst, converts methane into C5-C 16 Hydrocarbons.

[0045] The condensation separation module 4 has a built-in refrigeration unit and a condenser. It is connected to the outlet of the plasma catalytic reaction module 3. The liquid phase outlet of the condensation separation module 4 collects the product, and the gas phase outlet is connected to a circulation loop. The condensation separation module 4 has a refrigeration power of 200W, a condenser volume of 2L, and a condensation temperature controlled below 10°C. It cools the reaction products and separates them to obtain liquid hydrocarbon products.

[0046] The output of the green power supply module 5 is connected to the plasma reactor electrodes after inversion and voltage boosting. The green power supply module 5 provides renewable energy power to drive plasma discharge; it includes a 2kW photovoltaic power generation unit, a 5kWh lithium battery, a wind power generation unit or a combination thereof, and is equipped with an energy storage unit (battery); the output voltage is inverted and boosted to provide 15kV, 1kHz high-voltage AC power to the plasma reactor.

[0047] During system operation, the wellhead gas (mainly CH4, containing a small amount of N2) is purified by pretreatment module 1 and then enters buffer tank 21. Circulating compressor 22 pressurizes the gas and controls the space velocity to 750 h⁻¹. -1 The material is fed into plasma catalytic reaction module 3. Under the action of plasma discharge at 15kV and 1kHz, methane undergoes a non-oxidative coupling reaction on the catalyst surface, generating a product containing C5-C... 16 The reaction products of hydrocarbons.

[0048] The reaction products enter the condensation and separation module 4, where they are cooled to 10°C, and the liquid hydrocarbon products (gasoline and diesel fractions) are separated and collected. Unreacted methane and C2-C4 light hydrocarbons are discharged from the gas phase outlet and returned to the buffer tank 21 via the circulation loop 6. After mixing with fresh purified methane gas, it re-enters the reaction module for a cyclic reaction. When N2 accumulates in the circulation loop, a portion of the circulating gas is periodically released through the venting valve to maintain system stability.

[0049] After 100 hours of continuous operation, the total methane conversion rate reached over 95%, and the selectivity of liquid hydrocarbons was approximately 28%, achieving direct and efficient oil production from wellhead natural gas.

[0050] When the catalyst activity decreases, the feed is stopped, the circulation loop is closed, and hydrogen is introduced into the plasma catalytic reaction module 3 for in-situ regeneration with plasma assistance. The regeneration temperature is 30-40°C, and the regeneration time is 2 hours. After regeneration, the catalyst activity is restored to more than 95% of its initial level.

[0051] Example 2:

[0052] The green-electric coupling wellhead skid-mounted plasma-catalyzed direct methane-to-oil method includes the following steps:

[0053] Step 1: Simulated wellhead natural gas (composition: CH4 90%, N2 10%, no H2S) enters pretreatment module 1 at a flow rate of 5 L / min; the wellhead gas is filtered, dried and pressure regulated in pretreatment module 1 to obtain purified methane gas; the pressure is regulated to 0.1-0.3 MPa. Since the wellhead gas pressure usually fluctuates greatly, ranging from several MPa to tens of MPa, it must be adjusted to near atmospheric pressure, usually 0.1-0.3 MPa, before entering subsequent stages, especially before entering the buffer tank and plasma reactor. This pressure range serves two purposes: First, it protects system components: if the pressure rating of the buffer tank and skid-mounted piping is set too high, it will significantly increase the weight and cost of the equipment, which does not conform to the original intention of "skid-mounted" portability; Second, it protects plasma discharge characteristics: dielectric barrier discharge (DBD) is most likely to generate uniform micro-discharge near atmospheric pressure. If the pressure is too high, the breakdown voltage of the gas will rise significantly, causing the green electricity module to need to output a higher voltage, which can easily lead to dielectric breakdown or a decrease in energy efficiency.

[0054] Step 2: Purified methane gas enters buffer tank 21, and after being pressurized by circulating compressor 22, it is sent to plasma catalytic reaction module 3; the pressure is increased to 0.05-0.2 MPa. The pressurized pressure only needs to be slightly higher than the reactor outlet pressure to overcome the pressure drop (ΔP) of the catalyst bed and pipeline resistance. The reaction space velocity is controlled at 500-1000 h⁻¹ by circulating compressor 22. -1 The corresponding flow rate is approximately 8 L / min. The compressor maintains this space velocity by adjusting the flow rate, thereby ensuring the contact time of methane on the catalyst surface.

[0055] Step 3: The green power supply module 5 provides power to the plasma catalytic reaction module 3. The green power supply module 5 is a 2kW photovoltaic power generation unit or a 5kWh lithium battery, equipped with an energy storage unit (battery). Under the combined action of dielectric barrier discharge plasma and a hierarchical porous TiO2 / SiO2 catalyst with a mass ratio of 1:1, methane undergoes a non-oxidative coupling reaction to generate C5-C... 16 Reaction products of hydrocarbons; Reaction mechanism:

[0056] The plasma reactor discharges at 15 kV / 1 kHz, with a discharge power of approximately 150 W. Methane in plasma catalytic reaction module 3 is bombarded by high-energy electrons to generate free radicals such as CH3· and CH2·. These free radicals adsorb, couple, and grow on the TiO2 surface, forming long-chain hydrocarbons. The low CH3 desorption energy and high dehydrogenation barrier of TiO2 inhibit carbon deposition and promote chain growth. Macroscopically, the reactor does not require the intense heating required for traditional thermal catalysis (700-1100°C). The system is initially at room temperature. Microscopically, when the green electricity drives the plasma discharge, the high-energy electrons reach tens of thousands of degrees (enough to break the CH bonds of CH4), but the thermal motion temperature of the molecules (heavy particle temperature) remains relatively low. Operating temperature rise: During actual continuous operation, the internal temperature of the reactor naturally rises to 50-150°C due to the heat generated by the discharge. This not only eliminates the need for additional heating, but sometimes even requires the use of skid-mounted heat dissipation to maintain this temperature range, as a moderate temperature rise helps desorb the product (liquid hydrocarbons) and prevents catalyst carbon buildup.

[0057] Step 4: The reaction products enter the condensation and separation module 4, where they are cooled to below 10°C. Liquid hydrocarbon products (gasoline fraction and diesel fraction) are separated and collected. The system operates continuously for 100 hours, with samples taken for analysis every 8 hours. Analysis results: Methane single-pass conversion rate: 22.5%; Total methane conversion rate (considering recycling): 96.3%; Liquid hydrocarbons (C5-C60) 16 Selectivity: 27.8%; Liquid hydrocarbon yield: 0.15 kg / (kg catalyst·day); Energy consumption: 0.8 kWh / m³ CH4 (processing capacity).

[0058] Step 5: Unreacted methane and C2-C4 light hydrocarbons are discharged from the gas phase outlet of the condensation separation module 4, returned to the buffer tank 21 through the circulation loop 6, mixed with fresh purified methane gas, and then re-enter the reaction module for cyclic reaction.

[0059] The method further includes a venting step: when inert gas accumulates in the circulation loop 6, a portion of the circulating gas is released through the venting valve.

[0060] The method also includes a catalyst regeneration step: when the catalyst activity decreases, the feed is stopped, the circulation loop is closed, and a regeneration gas (hydrogen or air) is introduced to carry out in-situ regeneration under plasma assistance. The regeneration temperature is 30-40°C and the regeneration time is 1-3 hours.

[0061] Example 3:

[0062] The pure TiO2 catalyst scheme is basically the same as that in Example 2, except that the catalyst used is a pure TiO2 hierarchical porous catalyst; and the reactor parameters are adjusted to a peak voltage of 12kV and a frequency of 2kHz.

[0063] Experimental results: single-pass methane conversion: 11.8% (close to the literature); total methane conversion (considering recycling): 94.5%; liquid hydrocarbon selectivity: 29.2% (slightly higher than mixed oxides); carbon deposition: 0.8% (lower than 1.2% in Example 1).

[0064] Example 4:

[0065] The green electricity power supply module 5 adopts a wind power generation solution: This embodiment is basically the same as embodiment 2, except that: the green electricity power supply uses a 2kW wind turbine + energy storage battery; it is deployed in a well site with good wind resources; the operating parameters of the plasma reactor are adjusted to a peak voltage of 12kV and a frequency of 2kHz; and a pure TiO2 hierarchical porous catalyst is used. The operating effect is similar to that of embodiment 3, verifying the applicability of different green electricity sources.

[0066] Example 5:

[0067] Catalyst regeneration experiment: After the catalyst in Example 2 had run for 500 hours, the conversion rate dropped to 70% of the initial value. In-situ regeneration was then performed: the feed was stopped and the circulation was shut off; hydrogen gas was introduced (50 mL / min) to maintain the reactor pressure at 0.1 MPa; plasma treatment (10 kV / 1 kHz) was applied for 2 hours; the feed was resumed and the system was restarted. After regeneration, the catalyst activity recovered to 96% of the initial value, indicating that in-situ regeneration was effective.

[0068] This application integrates the entire process of pretreatment, reaction, separation, circulation, and regeneration, achieving long-term stable operation of the device. A comparison with existing technologies is shown in Table 1 below.

[0069]

Claims

1. A green-electric coupling wellhead skid-mounted plasma catalytic methane direct oil production system, comprising a pretreatment module (1), a gas buffer and circulation module (2), a plasma catalytic reaction module (3), a condensation separation module (4), and a green-electric power supply module (5). The pretreatment module (1) is connected to the wellhead gas production pipeline and is used to filter, dry and regulate the pressure of the gas coming from the wellhead. The gas buffer and circulation module (2) includes a buffer tank (21), a circulation compressor (22), and a circulation loop (6). The inlet of the buffer tank (21) is connected to the outlet of the pretreatment module (1), and the inlet of the circulation compressor (22) is connected to the outlet of the buffer tank (21). The circulation loop (6) connects the gas phase outlet of the condensation separation module (4) to the circulation inlet of the buffer tank (21). The plasma catalytic reaction module (3) is a dielectric barrier discharge reactor. Its inlet is connected to the outlet of the circulating compressor (22). The dielectric barrier discharge reactor is filled with a graded porous TiO2 / SiO2 catalyst. The high voltage electrode of the dielectric barrier discharge reactor is connected to the green power supply module (5). The condensation separation module (4) is connected to the outlet of the plasma catalytic reaction module (3) to cool the reaction products to below 10°C and separate them to obtain liquid hydrocarbon products. The green power supply module (5) is connected to the electrodes of the plasma catalytic reaction module (3) to provide renewable energy power to drive plasma discharge.

2. The system according to claim 1, characterized in that, The hierarchical porous TiO2 / SiO2 catalyst has a Ti / Si molar ratio of 1:1 to pure TiO2 and has a hierarchical porous structure, wherein the macropore diameter is ≥1.34μm and the mesopore diameter is 10-20nm.

3. The system according to claim 1, characterized in that, The operating parameters of the dielectric barrier discharge reactor are: peak voltage 10-20kV, frequency 0.5-5kHz.

4. The system according to claim 1, characterized in that, The green power supply module (5) includes a photovoltaic power generation unit, a wind power generation unit or a combination thereof, and is equipped with an energy storage unit.

5. The system according to claim 1, characterized in that, The circulating compressor (22) is an explosion-proof diaphragm compressor or a liquid ring compressor.

6. The system according to claim 1, characterized in that, The condensation separation module (4) includes a refrigeration unit and a condenser tank, and the condensation temperature is controlled at 5-15°C.

7. A wellhead skid-mounted plasma-catalyzed direct methane-to-oil method using the system described in any one of claims 1-6 for green-electric coupling, characterized in that, Includes the following steps: Step 1: The gas from the wellhead is filtered, dried and pressure regulated by the pretreatment module (1) to obtain purified methane gas; Step 2: Purified methane gas enters the buffer tank (21), and after being pressurized by the circulating compressor (22), it is sent to the plasma catalytic reaction module (3). Step 3: The green power supply module (5) provides power to the plasma catalytic reaction module (3), under the joint action of dielectric barrier discharge plasma and hierarchical porous TiO2 / SiO2 catalyst, methane undergoes non-oxidative coupling reaction to generate C5-C 16 hydrocarbons; Step 4: The reaction products enter the condensation separation module (4) and are cooled to below 10°C, where the liquid hydrocarbon products are separated and collected; Step 5: Unreacted methane and C2-C4 light hydrocarbons are discharged from the gas phase outlet of the condensation separation module (4), and returned to the buffer tank (21) through the circulation loop (6). After mixing with fresh purified methane gas, it re-enters the reaction module for cyclic reaction.

8. The method according to claim 7, characterized in that, In step 1, the pressure is adjusted to 0.1-0.3 MPa, and in step 2, the pressure is increased to 0.05-0.2 MPa. The reaction space velocity is controlled at 500-1000 h⁻¹ by the circulating compressor (22). -1 .

9. The method according to claim 7, characterized in that, The method further includes a release step: when inert gas accumulates in the circulation loop (6), a portion of the circulation gas is released through the release valve.

10. The method according to claim 7, characterized in that, The method further includes a catalyst regeneration step: when the catalyst activity decreases, the feed is stopped, regeneration gas is introduced, and in-situ regeneration is carried out with plasma assistance.

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