A reactor, system and method for plasma conversion of carbon dioxide and water

Abstract

The application discloses a reactor, a system and a method for converting carbon dioxide and water by plasma, and belongs to the technical field of greenhouse gas resource utilization and plasma application. By arranging a double medium tube structure, arranging a high-voltage needle electrode in an inner medium tube, and arranging a low-voltage ring electrode at the bottom of the inner medium tube, atmospheric pressure glow discharge can be generated between the electrodes, and plasma jet can be realized. Meanwhile, a biomass carbon placement area and a catalyst placement area are arranged in the plasma jet area, and through the synergistic effect between the plasma and the catalyst, multi-stage catalysis is realized, and the selectivity of target products is improved. The plasma is driven by renewable zero-carbon electricity, CO2 and H2O are converted into synthesis gas and acetic acid through catalysis, and the conversion rate, energy efficiency and liquid product selectivity in the conversion of CO2 and H2O are improved.

Description

Technical Field

[0001] The present invention relates to the field of greenhouse gas resource utilization and plasma application technology, and in particular to a reactor, system and method for converting carbon dioxide and water into plasma. Background Art

[0002] The effective capture and efficient utilization of CO2 is not only a deep development of the abundant and economic carbon resources in nature, but also a key way to solve the problem of excessive CO2 emissions, promote resource recycling and green economic transformation.

[0003] Plasma, as the fourth state of matter, has shown great potential in the field of CO2 conversion due to its unique properties. It is composed of multiple particles such as electrons, positive ions, negative ions, excited and ground state atoms or molecules, photons, etc., presenting a highly ionized and charge-balanced gas state. According to the state of plasma, it can be divided into: (1) equilibrium plasma, which is a plasma with high gas pressure and electron temperature roughly equal to the gas temperature; (2) non-equilibrium plasma, which is a plasma with electron temperature much greater than the gas temperature at low pressure or normal pressure. As an important form of plasma, non-equilibrium plasma has characteristics that make it an ideal choice for catalyzing CO2 conversion reactions.

[0004] Currently, utilizing non-equilibrium plasma to catalyze CO2 conversion is a key technology for achieving stable activation reactions of CO2 molecules at ambient temperature and pressure. On the one hand, non-equilibrium plasma can activate and decompose ground-state CO2 molecules under relatively mild temperature and pressure conditions, producing high-density active species with a theoretical energy efficiency of up to 90%. On the other hand, non-equilibrium plasma can be driven by renewable, zero-carbon electricity, such as photovoltaic and wind power, thereby enabling on-site consumption of new energy and forming a green, low-carbon, and sustainable industrial system. Adding a hydrogen source to the plasma-catalyzed CO2 conversion process can synthesize high-value-added products, effectively promoting carbon recycling. Water (H2O) is the most readily available hydrogen source. Plasma-catalyzed conversion of CO2 and H2O to produce high-value-added products meets the requirements of sustainable development and has high industrial application value.

[0005] However, the non-equilibrium plasma catalytic conversion of carbon dioxide and water includes the following difficulties: the strong adsorption effect of H2O on electrons inhibits CO2 conversion, and the CO2 conversion rate is significantly reduced after the introduction of H2O; the main product of CO2 and H2O conversion is synthesis gas, and the separation, storage and transportation costs of gas products are high, while the product selectivity of liquid products such as alcohols and acids is extremely low.

[0006] Therefore, how to design a reactor, system and related methods for non-equilibrium plasma catalytic conversion of carbon dioxide and water to solve the above difficulties and achieve high conversion rate and liquid product selectivity in the conversion of CO2 and H2O has become a technical problem that technicians in this field urgently need to overcome. Summary of the Invention

[0007] The object of the present invention is to provide a reactor, system and method for plasma conversion of carbon dioxide and water to solve the problems existing in the prior art.

[0008] The present invention solves the above technical problems through the following technical solutions:

[0009] A reactor for converting carbon dioxide and water into plasma, comprising an outer medium tube, an inner medium tube, a high-voltage needle electrode, a low-voltage ring electrode, and a mesh support portion; an inlet and an outlet are provided at the top and bottom of the outer medium tube, respectively; and the mesh support portion is fixedly disposed on a horizontal cross-section at the lower portion of the outer medium tube;

[0010] The inner dielectric tube is shorter than the outer dielectric tube and is coaxially sleeved in the outer dielectric tube. The high-voltage needle electrode is shorter than the inner dielectric tube and is coaxially sleeved in the inner dielectric tube. The top ends of the inner dielectric tube and the high-voltage needle electrode are fixed on the top of the outer dielectric tube. The low-voltage ring electrode is set at the bottom of the inner dielectric tube.

[0011] An annular gap is formed between the high-voltage needle electrode and the inner medium tube, and the annular gap is connected to the inlet for introducing reaction gases, which include carbon dioxide and water; a plasma discharge zone is formed between the bottom of the high-voltage needle electrode and the top of the low-voltage ring electrode for the primary reaction; a plasma jet zone is formed between the bottom of the inner medium tube and the mesh support portion, and the plasma jet zone is provided with a biomass carbon placement zone and a catalyst placement zone from top to bottom, which are used for the secondary reaction and the tertiary reaction, respectively; a blank area is formed between the mesh support portion and the bottom of the outer medium tube.

[0012] Furthermore, the outer dielectric tube is a quartz tube, the inner dielectric tube is a corundum tube, the high-voltage needle electrode is a tungsten needle electrode, the low-voltage ring electrode is a stainless steel ring electrode, and the mesh support part is a stainless steel mesh.

[0013] A method for plasma conversion of carbon dioxide and water, using the above-mentioned plasma conversion reactor for carbon dioxide and water, comprises the following steps:

[0014] A catalyst is added to the catalyst placement area, and biomass carbon is added to the biomass carbon placement area. Water is introduced into the inlet of the reactor, and carbon dioxide is introduced at a gas flow rate of 300-1500 mL / min. High voltage is applied to the high-voltage needle electrode, and an atmospheric pressure glow discharge plasma is formed in the plasma discharge area. Under the action of the atmospheric pressure glow discharge plasma, the carbon dioxide and water undergo a first-order reaction to obtain a first-order reaction product.

[0015] At the same time, under the restraint of the inner medium tube and the effect of gas flow rate, the atmospheric pressure glow discharge plasma forms a plasma jet, allowing the products of the primary reaction, unreacted carbon dioxide and water to enter the plasma jet area, and a secondary reaction occurs on the surface of the biomass carbon to obtain the products of the secondary reaction;

[0016] Under the action of the catalyst, the product of the secondary reaction, unreacted carbon dioxide and water continue to undergo a tertiary reaction to obtain the product of the tertiary reaction.

[0017] Furthermore, the primary reaction is the vibration excitation dissociation of CO2 and H2O under the action of plasma, and the products of the primary reaction include CO·, O·, H·, OH· free radicals and CO, O2, H2 molecules; the secondary reaction is the Boudouard reaction and the water gas reaction, and the products of the secondary reaction include H·, CO· free radicals and CO, H2 molecules; the tertiary reaction is the hydrogenation reaction of CO· free radicals, CO and CO2, and the products of the tertiary reaction include acetic acid.

[0018] Furthermore, the catalyst is a hydrophobic iron-zinc catalyst.

[0019] Furthermore, the electron density of atmospheric pressure glow discharge plasma is 10 19 m -3 ~ 10 21 m -3 , the electron temperature is 2eV ~ 4 eV, the gas temperature is 1000~2000 ℃; the temperature of the plasma jet zone is 200~700 ℃.

[0020] Furthermore, the molar ratio of carbon dioxide and water introduced into the reactor is (1:2) to (2:1).

[0021] A system for converting carbon dioxide and water into plasma, comprising a gas supply module, a circuit module, a detection module, a process diagnosis module and the reactor for converting carbon dioxide and water into plasma;

[0022] A reactor for catalyzing primary, secondary and tertiary reactions between carbon dioxide and water;

[0023] A gas supply module, comprising a first CO2 gas cylinder and a water bath, wherein the first CO2 gas cylinder is connected to the inlet of the reactor via the water bath for providing reaction gas;

[0024] The circuit module includes an AC high-voltage power supply and a current-limiting resistor. The AC high-voltage power supply is connected to the high-voltage needle electrode via the current-limiting resistor. The current-limiting resistor is used to limit the discharge current to achieve atmospheric pressure glow discharge. When the voltage is high enough, non-equilibrium plasma is generated in the plasma discharge region, and a plasma jet is formed in the area where the low-voltage ring electrode is downward.

[0025] The detection module includes a cold trap bottle, a third flow meter and a gas chromatograph. The outlet of the reactor is connected to the cold trap bottle, the third flow meter and the gas chromatograph in sequence. The cold trap bottle is used to collect the reaction products. The third flow meter is used to obtain the flow rate of the gas products. The gas chromatograph is used to detect the type and content of the reaction products.

[0026] Process diagnostic module, including sampling resistor, oscilloscope, high voltage probe, thermocouple and spectrometer,

[0027] The low-voltage ring electrode is connected to the ground terminal via a sampling resistor, one end of the oscilloscope is electrically connected to the high-voltage needle electrode via a high-voltage probe, and the other end is electrically connected to the circuit between the low-voltage ring electrode and the sampling resistor;

[0028] Among them, the oscilloscope is used to obtain the electrical characteristics of the discharge, the high-voltage probe is used to obtain the discharge voltage, and the sampling resistor is used to obtain the discharge current;

[0029] Thermocouples are set in the blank area of ​​the reactor to obtain the spatial distribution of the axial temperature field of the plasma jet and the temperature of the catalyst placement area.

[0030] Furthermore, the gas supply module also includes a first flow meter, which is arranged between the CO2 gas cylinder and the water bath and is used to adjust the flow rate of the incoming carbon dioxide.

[0031] Furthermore, the gas supply module also includes a second CO2 gas cylinder and a second flow meter, and the second CO2 gas cylinder is connected between the water bath and the inlet via the second flow meter.

[0032] Compared with the prior art, the present invention has the following positive effects:

[0033] The present invention provides a reactor for converting carbon dioxide and water into plasma. By setting up a dual-medium tube structure, a high-voltage needle-shaped electrode is arranged in an inner medium tube, and a low-voltage ring-shaped electrode is arranged around the bottom of the inner medium tube, so that atmospheric pressure glow discharge can be generated between the electrodes to realize a plasma jet. At the same time, a biomass carbon placement area and a catalyst placement area are provided in the plasma jet area. Through the synergistic effect between the plasma and the catalyst, multi-stage catalysis is realized, thereby improving the selectivity of the target product.

[0034] The present invention provides a method for converting carbon dioxide and water by plasma. By using the method, atmospheric pressure glow discharge plasma can be formed in a plasma discharge zone, so that the dissociation of CO2 and H2O molecules is mainly based on vibration excitation, thereby achieving a higher conversion rate. Biomass carbon is added to a biomass carbon placement zone to inhibit the composite reaction of CO and H2, and the Boudouard reaction and the water-gas reaction can increase the conversion rate of CO2 and H2O and the CO and H2 yields, thereby solving the problem of low CO2 conversion rate in the CO2 and H2O conversion process. Furthermore, a hydrophobic iron-zinc catalyst is added to a catalyst placement zone to inhibit the water-gas conversion reaction and efficiently catalyze the hydrogenation of CO·free radicals, CO, and CO2 to synthesize acetic acid, thereby solving the problem of low liquid product selectivity in the CO2 and H2O conversion process.

[0035] The present invention provides a system for converting carbon dioxide and water by plasma. The system uses an oscilloscope, a thermocouple, and a spectrometer to collect the electrical, thermal, and optical properties of the discharge in real time, thereby achieving online diagnosis of the reaction process and facilitating the regulation of the reaction process. The system provides reaction gas through a CO2 cylinder, a flow meter, and a water bath, and the flow rate of the CO2 and the temperature of the water bath can be adjusted, thereby directly controlling the flow rate and molar ratio of the reaction gas. The system is simple, easy to use, and low-cost.

[0036] Furthermore, the system can be connected to a second CO2 cylinder and a second flow meter. Through two CO2 gas supply methods, one of which is pure CO2 and the other is CO2 and H2O, the flow rate of the reaction gas and the molar ratio of CO2 and H2O can be more conveniently controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0038] Figure 1 Schematic diagram of the structure of the reactor of the present invention;

[0039] Figure 2 It is a structural diagram of the system of the present invention;

[0040] Figure 3 It is a schematic diagram of the process of the present invention;

[0041] Figure 4 Schematic diagram of the reaction pathway of the present invention;

[0042] Figure 5 This is a schematic diagram of the application prospects of the present invention.

[0043] Among them, 1 is the first CO2 cylinder; 2 is the first flow meter; 3 is the water bath; 4 is the reactor; 5 is the AC high-voltage power supply; 6 is the current-limiting resistor; 7 is the high-voltage probe; 8 is the oscilloscope; 9 is the sampling resistor; 10 is the spectrometer; 11 is the thermocouple; 12 is the cold trap bottle; 13 is the gas chromatograph; 14 is the third flow meter; 15 is the second flow meter; 16 is the second CO2 cylinder.

[0044] 4-1 is the outer medium tube; 4-2 is the inner medium tube; 4-3 is the high-voltage needle electrode; 4-4 is the low-voltage ring electrode; 4-5 is the mesh support part; 4-6 is the plasma discharge area; 4-7 is the plasma jet area; 4-8 is the biomass carbon placement area; 4-9 is the catalyst placement area; 4-10 is the blank area. DETAILED DESCRIPTION

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0046] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0047] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0048] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0049] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0050] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0051] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings, which are intended to explain the present invention rather than to limit it.

[0052] See also Figure 1 This embodiment provides a reactor for plasma conversion of carbon dioxide and water, comprising an external medium tube 4-1, an internal medium tube 4-2, a high-voltage needle electrode 4-3, a low-voltage ring electrode 4-4, and a mesh support portion 4-5; an inlet and an outlet are provided at the top and bottom of the external medium tube 4-1, respectively, and the mesh support portion 4-5 is fixedly provided on a horizontal cross-section at the lower portion of the external medium tube 4-1;

[0053] The inner medium tube 4-2 is shorter than the outer medium tube 4-1 and is coaxially sleeved in the outer medium tube 4-1. The high-voltage needle electrode 4-3 is shorter than the inner medium tube 4-2 and is coaxially sleeved in the inner medium tube 4-2. The top ends of the inner medium tube 4-2 and the high-voltage needle electrode 4-3 are fixedly set on the top of the outer medium tube 4-1. The low-voltage ring electrode 4-4 is set at the bottom of the inner medium tube 4-2.

[0054] An annular gap is formed between the high-voltage needle electrode 4-3 and the inner medium tube 4-2, and the annular gap is connected to the inlet for introducing reaction gases, which include carbon dioxide and water; a plasma discharge zone 4-6 is formed between the bottom of the high-voltage needle electrode 4-3 and the top of the low-voltage ring electrode 4-4, for the primary reaction; a plasma jet zone 4-7 is formed between the bottom of the inner medium tube 4-2 and the mesh support part 4-5, and the plasma jet zone 4-7 is provided with a biomass carbon placement area 4-8 and a catalyst placement area 4-9 from top to bottom, which are used for the secondary reaction and the tertiary reaction, respectively; a blank area 4-10 is formed between the mesh support part 4-5 and the bottom of the outer medium tube 4-1.

[0055] Specifically, the outer medium tube 4-1 is a quartz tube, the inner medium tube 4-2 is a corundum tube, the high-voltage needle electrode 4-3 is a tungsten needle electrode, the low-voltage ring electrode 4-4 is a stainless steel ring electrode, and the mesh support part 4-5 is a stainless steel mesh.

[0056] In this embodiment, the outer diameter of the outer medium tube is 24 mm and the inner diameter is 20 mm, the outer diameter of the inner medium tube is 8 mm and the inner diameter is 6 mm, the diameter of the tungsten needle electrode is 3 mm, and the outer diameter of the stainless steel ring electrode is 8 mm and the aperture is 3 mm.

[0057] See also Figure 2 , this embodiment provides a system for plasma conversion of carbon dioxide and water, including a gas supply module, a circuit module, a detection module, a process diagnosis module and the above-mentioned reactor 4 for catalyzing the conversion of carbon dioxide and water; the reactor 4 is used to catalyze the primary reaction, secondary reaction and tertiary reaction of carbon dioxide and water; the gas supply module includes a first CO2 gas cylinder 1 and a water bath 3, the first CO2 gas cylinder 1 is connected to the inlet of the reactor 4 through the water bath 3, and is used to provide reaction gas; the circuit module includes an AC high-voltage power supply 5 and a current-limiting resistor 6, the AC high-voltage power supply 5 is connected to the high-voltage needle electrode 4-3 through the current-limiting resistor 6, and the current-limiting resistor 6 is used to limit the discharge current to achieve atmospheric pressure glow discharge. When the voltage is high enough, the plasma discharge region 4-6 generates non-equilibrium plasma and generates a low-pressure ring plasma. A plasma jet is formed in the area where the ring electrode 4-4 is downward; a detection module comprises a cold trap bottle 12, a third flow meter 14 and a gas chromatograph 13, the outlet of the reactor 4 is connected to the cold trap bottle 12, the third flow meter 14 and the gas chromatograph 13 in sequence, the cold trap bottle 12 is used to collect the reaction products, the third flow meter 14 is used to obtain the flow of the gas products, and the gas chromatograph 13 is used to detect the type and content of the reaction products; a process diagnosis module comprises a sampling resistor 9, an oscilloscope 8, a high-voltage probe 7, a thermocouple 11 and a spectrometer 10, the low-voltage ring electrode (4-4) is connected to the ground terminal via the sampling resistor (9), one end of the oscilloscope (8) is electrically connected to the high-voltage needle electrode via the high-voltage probe (7), and the other end is electrically connected to the circuit between the low-voltage ring electrode (4-4) and the sampling resistor (9);

[0058] Among them, the sampling resistor 9 is used to obtain the discharge current, the oscilloscope 8 is used to obtain the electrical characteristics of the discharge, the high-voltage probe 7 is used to obtain the discharge voltage, and the thermocouple 11 is set in the blank area of ​​the reactor 4 to obtain the spatial distribution of the axial temperature field of the plasma jet and the temperature of the catalyst placement area 4-9.

[0059] Specifically, the gas supply module further includes a first flow meter 2, which is arranged between the CO2 cylinder 1 and the water bath 3 and is used to adjust the flow rate of the introduced carbon dioxide.

[0060] Specifically, the gas supply module further includes a second CO 2 gas cylinder 16 and a second flow meter 15 , and the second CO 2 gas cylinder 16 is connected between the water bath and the inlet via the second flow meter 15 .

[0061] In this embodiment, the AC high-voltage source has a frequency of 20 kHz, a maximum output voltage of 20 kV, and a maximum output power of 500 W. The current-limiting resistor has a resistance of 160 kΩ, and the power rating of the current-limiting resistor should be greater than 400 W to prevent overheating. When the voltage is sufficiently high, the current-limiting resistor, the high-voltage needle electrode, and the low-voltage ring electrode generate an atmospheric-pressure glow discharge between the electrodes. During the reaction, when the temperature near the catalyst reached 200°C, the liquid product was collected using a cold trap bottle placed in ice water. During the collection process, the type and content of the gaseous product were detected online using the thermal conductivity detector (TCD) of a gas chromatograph (Bruker, scion 456-GC). 5 mL of liquid product was collected and placed in a headspace injection bottle, and the type and content of the liquid product were detected using the hydrogen flame ionization detector (FID) of the gas chromatograph. The gas product flow rate was monitored in real time using a flow meter. The product yield, selectivity, and reaction gas conversion rate were calculated based on the gas product flow rate, reaction time, reaction gas flow rate, and product content. Combined with the discharge power, the energy efficiency could be calculated. The process diagnostic module uses an oscilloscope (Puyuan, DH0924S) to obtain discharge electrical characteristics; a high-voltage probe (Tektronix, P6015A) to acquire discharge voltage; and the discharge current is acquired by measuring the voltage across a 50 Ω non-inductive resistor. The discharge voltage and current waveforms are analyzed to monitor the discharge form and calculate parameters such as discharge power and electric field intensity. A K-type thermocouple combined with a digital display is used to measure the spatial distribution of the axial temperature field in the plasma jet and monitor temperature changes near the catalyst. A spectrometer (Andor, Mechelle 500) coupled with an ICCD (Andor, iStar 334T-18U-63) camera is used to acquire discharge emission spectra, calculate electron density, electron excitation temperature, vibrational temperature, and rotational temperature, and analyze the effects of reaction parameters on active particles. The spectrometer described in this example has a minimum shutter time of less than 2 ns, a spectral measurement range of 200–900 nm, and a spectral measurement accuracy of 0.05 nm.

[0062] The first flow meter 2 and the second flow meter 15 are both set to 500 mL / min, and the water bath temperature is set to 95 °C (corresponding to a molar ratio of CO2 to H2O of 1:1). The flow rate and molar ratio of CO2 and H2O can be changed by adjusting the first flow meter 2, the second flow meter 15 and the water bath temperature.

[0063] For example, the CO2 flow rates of the two channels are the same. When the water bath temperature is set at 90°C, the molar ratio of CO2 to H2O is 2:1; when the water bath temperature is set at 95°C, the molar ratio of CO2 to H2O is 1:1; when the water bath temperature is set at 100°C, the corresponding molar ratio of CO2 to H2O is 1:2.

[0064] See also Figure 3 This embodiment provides a method for converting carbon dioxide and water into plasma, using the above-mentioned reactor, including the following steps:

[0065] First, the hydrophobic iron-zinc catalyst was treated. 1 g of the hydrophobic iron-zinc catalyst was calcined in a tube furnace at 350 °C for 10 h in an atmosphere of hydrogen and argon (H2:Ar volume ratio of 1:4) at 250 mL / min to obtain a reduced hydrophobic iron-zinc catalyst, which was then stored in a vacuum.

[0066] 5.5 g of biomass carbon (coconut shell carbon) and a reduced hydrophobic iron-zinc catalyst were then loaded into the corresponding areas of the reactor. The CO2 cylinder and water bath were turned on to supply the reactor with 1000 mL / min of CO2 and 1000 mL / min of water vapor. Once the gas supply stabilized, the AC high-voltage power supply was turned on and the voltage regulator was adjusted to apply 12 kV, 20 kHz AC high voltage to achieve a stable atmospheric pressure glow discharge and plasma jet. The reactant gases were synthesized into the target product through a three-stage catalytic reaction.

[0067] For details, see Figure 4 , first-order reaction: the reaction gas enters the reactor from the annular gap between the inner medium tube (corundum tube) and the high-voltage needle electrode (tungsten needle electrode), passes through the plasma discharge zone, and the atmospheric pressure glow discharge plasma is a typical non-equilibrium plasma with an electron density of 10 19 m -3 ~ 10 21 m -3With an electron temperature of 2 eV to 4 eV and a gas temperature of 1000-2000°C, CO2 and H2O can be decomposed via the most energy-efficient vibrational excitation dissociation. Secondary reactions: Boudouard reactions (CO2 + C → 2CO) and water-gas reactions (C + H2O → CO + H2) occur on the biomass carbon surface, increasing the conversion of CO2 and H2O and the yields of CO and H2. The biomass carbon also reacts with O2, O·, and other substances, inhibiting the recombination of CO and H2, further improving the conversion of CO2 and H2O. Tertiary reactions: The hydrophobic iron-zinc catalyst has a core-shell structure. The iron-zinc bimetallic catalyst is encapsulated by a porous SiO2 shell with hydrophobic groups attached to the SiO2 shell surface. This structure inhibits the water-gas reaction (CO + H2O → CO2 + H2) without reducing catalyst activity. CO· radicals, CO, and CO2 are hydrogenated on the catalyst surface to synthesize acetic acid. Finally, the products exit the reactor through a mesh support (stainless steel mesh).

[0068] Specifically, in the plasma discharge zone, CO2 and H2O reaction gases are vibrationally excited and dissociated into free radicals such as CO·, O·, H·, OH·, and molecules such as CO, O2, and H2; on the surface of biomass carbon (coconut shell carbon) in the plasma jet zone, carbon reacts with O·, OH·, O2, CO2, H2O, etc., while inhibiting the composite reaction of CO and H2, thereby improving the conversion rate of CO2, H2O and the yield of CO and H2; on the surface of the hydrophobic iron-zinc catalyst in the jet zone, CO· free radicals, CO, and CO2 are hydrogenated to synthesize acetic acid, while inhibiting the water gas change reaction.

[0069] After testing and calculation, the method provided in this embodiment achieved a CO2 conversion rate of more than 7%, an H2O conversion rate of 8%, and an acetic acid selectivity of 30%.

[0070] In addition, the preparation method of the hydrophobic iron-zinc catalyst described in this embodiment specifically includes: dissolving Fe(NO3)3 and Zn(NO3)2 (the molar ratio of Fe:Zn is 3:1) hydrate in deionized water to prepare a 0.5 mol / L first solution, and preparing a 0.5 mol / L K2CO3 solution, adding the K2CO3 solution dropwise to the first solution at 60°C under stirring conditions until the pH value of the solution is 7, stirring the mixture for 1 hour, standing for aging for 1 hour, centrifuging and washing the precipitate, drying in a 110°C oven for 24 hours, grinding into powder, and then calcining in a 350°C muffle furnace for 6 hours to obtain a FeZn catalyst; taking 1 g of FeZn catalyst and ultrasonically dispersing it (100 W, 20 min) in 250 mL of ethanol, adding 2.5 mL of ethyl silicate, stirring for 4 hours, adding 5 mL of ammonia water (analytical grade) and 20 mL of water, continuing to stir for 4 hours, centrifuging, washing the precipitate with ethanol, and calcining at 100 ℃ oven dried for 24 h to obtain FeZn@SiO2 catalyst; 1 g of FeZn@SiO2 catalyst was added with 100 mL of n-hexane and 2 mL of trimethylsilyl chloride, ultrasonicated (100 W, 2 h), centrifuged, washed with n-hexane, and dried in a vacuum oven at 80 ℃ for 6 h to obtain a hydrophobic iron-zinc catalyst (FeZn@SiO2-c).

[0071] The conversion results of CO2 and H2O can be further improved by adjusting the molar ratio of Fe and Zn in the hydrophobic iron-zinc catalyst, discharge power, gas flow rate and the molar ratio of CO2 to H2O.

[0072] See also Figure 5 The present invention uses renewable zero-carbon electricity to drive plasma, capture CO2 generated by transportation and industry, and catalyze CO2 and H2O into synthesis gas, acetic acid, etc. The synthesis gas can also be converted into acetic acid, etc. through processes such as the Fischer-Tropsch reaction, converting greenhouse gases into fuels and chemical raw materials, achieving energy conversion while reducing carbon emissions.

[0073] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A reactor for plasma conversion of carbon dioxide and water, characterized in that: It comprises an outer medium tube (4-1), an inner medium tube (4-2), a high-voltage needle-shaped electrode (4-3), a low-voltage ring-shaped electrode (4-4) and a mesh support portion (4-5); the top and bottom of the outer medium tube (4-1) are respectively provided with an inlet and an outlet, and the mesh support portion (4-5) is fixedly arranged on a horizontal cross-section at the lower portion of the outer medium tube (4-1); The inner dielectric tube (4-2) is shorter than the outer dielectric tube (4-1) and is coaxially sleeved in the outer dielectric tube (4-1). The high-voltage needle-shaped electrode (4-3) is shorter than the inner dielectric tube (4-2) and is coaxially sleeved in the inner dielectric tube (4-2). The top ends of the inner dielectric tube (4-2) and the high-voltage needle-shaped electrode (4-3) are fixedly arranged on the top of the outer dielectric tube (4-1). The low-voltage ring electrode (4-4) is arranged at the bottom of the inner dielectric tube (4-2). An annular gap is formed between the high-voltage needle-shaped electrode (4-3) and the inner medium tube (4-2), and the annular gap is connected to the inlet for introducing reaction gas, which includes carbon dioxide and water. A plasma discharge zone (4-6) is formed between the bottom of the high-voltage needle-shaped electrode (4-3) and the top of the low-voltage ring-shaped electrode (4-4), for generating a primary reaction. A plasma jet zone (4-7) is formed between the bottom of the inner medium tube (4-2) and the mesh support portion (4-5). The plasma jet zone (4-7) is provided with a biomass carbon placement zone (4-8) and a catalyst placement zone (4-9) from top to bottom, for generating a secondary reaction and a tertiary reaction, respectively. A blank zone (4-10) is formed between the mesh support portion (4-5) and the bottom of the outer medium tube (4-1).

2. The plasma conversion reactor for carbon dioxide and water according to claim 1, characterized in that: The outer medium tube (4-1) is a quartz tube, the inner medium tube (4-2) is a corundum tube, the high-voltage needle electrode (4-3) is a tungsten needle electrode, the low-voltage ring electrode (4-4) is a stainless steel ring electrode, and the mesh support part (4-5) is a stainless steel mesh.

3. A method for converting carbon dioxide and water by plasma, characterized in that: The reactor for converting carbon dioxide and water using the plasma of claim 1 or 2 comprises the following steps: A catalyst is added to the catalyst placement area (4-9), and biomass carbon is added to the biomass carbon placement area (4-8). Water is introduced into the inlet of the reactor, and carbon dioxide is introduced at a gas flow rate of 300-1500 mL / min. High voltage is applied to the high-voltage needle electrode, and an atmospheric pressure glow discharge plasma is formed in the plasma discharge area (4-6). Under the action of the atmospheric pressure glow discharge plasma, the carbon dioxide and water undergo a first-order reaction to obtain a first-order reaction product. At the same time, under the action of the restraining force of the inner medium tube (4-2) and the gas flow rate, the atmospheric pressure glow discharge plasma forms a plasma jet, so that the products of the primary reaction, unreacted carbon dioxide and water enter the plasma jet region (4-7), and a secondary reaction occurs on the surface of the biomass carbon to obtain the products of the secondary reaction; Under the action of the catalyst, the product of the secondary reaction, unreacted carbon dioxide and water continue to undergo a tertiary reaction to obtain the product of the tertiary reaction.

4. The method for plasma conversion of carbon dioxide and water according to claim 3, characterized in that: The primary reaction is the vibration excitation dissociation of CO2 and H2O under the action of plasma. The products of the primary reaction include CO·, O·, H·, OH· free radicals and CO, O2, H2 molecules; the secondary reaction is the Boudouard reaction and the water-gas reaction. The products of the secondary reaction include H·, CO· free radicals and CO, H2 molecules; the tertiary reaction is the hydrogenation reaction of CO· free radicals, CO and CO2. The products of the tertiary reaction include acetic acid.

5. The method for plasma conversion of carbon dioxide and water according to claim 3, characterized in that: The catalyst is a hydrophobic iron-zinc catalyst.

6. The method for plasma conversion of carbon dioxide and water according to claim 3, wherein: The electron density of atmospheric pressure glow discharge plasma is 10 19 m -3 ~ 10 21 m -3 , the electron temperature is 2 eV ~ 4 eV, the gas temperature is 1000~2000 ℃; the temperature of the plasma jet region (4-7) is 200~700 ℃.

7. The method for plasma conversion of carbon dioxide and water according to claim 3, characterized in that: The molar ratio of carbon dioxide and water introduced into the reactor (4) is (1:2) to (2:1).

8. A system for converting carbon dioxide and water by plasma, characterized in that: It comprises a gas supply module, a circuit module, a detection module, a process diagnosis module and a reactor (4) for converting carbon dioxide and water into plasma according to claim 1 or 2; A reactor (4) for catalyzing a primary reaction, a secondary reaction, and a tertiary reaction between carbon dioxide and water; A gas supply module comprises a first CO2 gas cylinder (1) and a water bath (3), wherein the first CO2 gas cylinder (1) is connected to the inlet of the reactor (4) via the water bath (3) for providing reaction gas; The circuit module includes an AC high-voltage power supply (5) and a current-limiting resistor (6). The AC high-voltage power supply (5) is connected to a high-voltage needle electrode (4-3) via the current-limiting resistor (6). The current-limiting resistor (6) is used to limit the discharge current to achieve atmospheric pressure glow discharge. When the voltage is high enough, a non-equilibrium plasma is generated in the plasma discharge region (4-6), and a plasma jet is formed in the region downward of the low-voltage ring electrode (4-4). The detection module comprises a cold trap bottle (12), a third flow meter (14) and a gas chromatograph (13), wherein the outlet of the reactor (4) is connected to the cold trap bottle (12), the third flow meter (14) and the gas chromatograph (13) in sequence, the cold trap bottle (12) is used to collect the reaction product, the third flow meter (14) is used to obtain the flow rate of the gas product, and the gas chromatograph (13) is used to detect the type and content of the reaction product; A process diagnostic module, comprising a sampling resistor (9), an oscilloscope (8), a high voltage probe (7), a thermocouple (11) and a spectrometer (10), The low-voltage ring electrode (4-4) is connected to the ground terminal via the sampling resistor (9); one end of the oscilloscope (8) is electrically connected to the high-voltage needle electrode via the high-voltage probe (7); and the other end is electrically connected to the circuit between the low-voltage ring electrode (4-4) and the sampling resistor (9); The oscilloscope (8) is used to obtain the electrical characteristics of the discharge, the high-voltage probe (7) is used to obtain the discharge voltage, and the sampling resistor (9) is used to obtain the discharge current; The thermocouple (11) is arranged in the blank area (4-10) of the reactor (4) to obtain the spatial distribution of the axial temperature field of the plasma jet and the temperature of the catalyst placement area (4-9).

9. The plasma conversion system for carbon dioxide and water according to claim 8, characterized in that: The gas supply module further comprises a first flow meter (2), which is arranged between the CO2 gas cylinder (1) and the water bath (3) and is used to adjust the flow rate of the introduced carbon dioxide.

10. The plasma conversion system for carbon dioxide and water according to claim 9, characterized in that: The gas supply module further comprises a second CO2 gas cylinder (16) and a second flow meter (15), and the second CO2 gas cylinder (16) is connected between the water bath and the inlet via the second flow meter (15).

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