In-situ infrared dual observation device and method of variable plasma coupling structure

Abstract

The application discloses an in-situ infrared double observation device and method of a variable plasma coupling structure, which comprises four parts of a plasma power supply unit, a gas supply and separation and purification unit, an in-situ reaction / observation unit and a signal acquisition control unit. The in-situ reaction / observation cavity realizes initiation of multiple discharge modes and in-situ observation by regulating electrode structure and power supply parameters, and simultaneously obtains evolution processes of steady-state products, transient gas-phase species and surface adsorption species. The high-voltage electrode at the top of the cavity is directly connected with a parameterized pulse power supply after being isolated by an insulating medium, and reaction raw gas is mixed into the cavity after being controlled by a flow controller, so that the discharge process is controllable and stable. The application has high function integration degree, can be widely used in surface processing and catalytic reaction processes dominated by plasma technology, is easy to reveal a high-selectivity production route of target products and realizes real-time optimization of a process through process control feedback, and has a good prospect in basic research and industrial application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of greenhouse gas conversion, and particularly relates to an in-situ infrared double observation device and method of a variable plasma coupling structure. BACKGROUND

[0002] Plasma is the fourth state of matter after solid, liquid and gas. When the external voltage reaches the breakdown voltage, the gas molecules are ionized to produce a mixture including electrons, ions, atoms and atomic groups. Plasma-catalysis is a new branch of plasma processing, which involves the cross of various disciplines, such as physical chemistry, material science and plasma physics. The purpose is to enhance the catalytic reaction by adding plasma to the reaction. The interaction of specific plasma and catalyst may lead to synergistic effect. However, the basic process of current plasma-catalysis is still poorly understood. There are about 6 kinds of particles in low-temperature plasma, including electrons, positive ions, negative ions, ground-state atoms or molecules, excited-state atoms or molecules and free radicals. These particles are usually more active than the particles generated in chemical reactions, and are more likely to react with the contacted substances, so that the old chemical bonds on the material surface are broken and new chemical bonds are generated at the same time. Low-temperature plasma technology is a rapidly developing material surface modification technology in recent years, which can improve the physical and chemical properties of the material surface without affecting the performance of the material substrate, and has broad application prospects. With the development of low-temperature plasma technology, low-temperature plasma coupled multiphase catalysis technology and material modification technology have gradually become one of the current international frontiers, and have wide application prospects in military and civilian fields.

[0003] For plasma-catalysis research and plasma material modification research, infrared spectroscopy is generally used as an online / offline characterization means for steady-state products and treated solid samples. Infrared spectroscopy belongs to molecular spectroscopy, one of the four spectroscopies, and is an important basic means for determining the composition and structure of molecules. Due to the difficulty of introducing a plasma system with a breakdown voltage as high as tens of kilovolts into the traditional in-situ infrared spectroscopy technology, it is impossible to give the interaction information of plasma and material / catalytic surface in micro-time and space scale and the plasma synergistic mechanism, which limits the development and application of plasma technology in multiple fields. The in-situ infrared spectroscopy technology is an optical diagnostic technology for qualitative and quantitative description of gas molecules and solid surface adsorbed species under different steady-state reaction temperatures, temperature rise rates, gas pressures and material / catalyst types.

[0004] For low-temperature plasma coupled multiphase catalysis research and material modification research, in order to meet the comprehensive diagnosis of multiphase catalysis, material modification and pollutant degradation in the low-temperature plasma synergistic environment, it is urgent to develop an in-situ infrared spectroscopy characterization technology coupled with plasma.

[0005] Chinese patent application CN201510996781.9 discloses a device and method for in-situ capturing of heterogeneous catalytic reaction intermediates, the device comprising a reaction gas control system, an in-situ infrared cell system, and an analysis testing system. Its feature is that it can monitor online the intermediates and products with low content (ppm level), thereby enabling comparison of the performance of the catalyst and research of the heterogeneous catalytic reaction mechanism.

[0006] Chinese patent application CN201811475969.9 relates to a high-vacuum condition low-temperature to high-temperature controllable temperature infrared in-situ reaction cell. Its feature is that the in-situ cell can realize gas inlet under high-vacuum condition, vacuum maintenance, precise control from low temperature (110 K) to high temperature (1000 K or above), thereby enabling in-situ research of gas adsorption and reaction of powder samples and thin film samples under different conditions and effectively excluding the influence of background atmosphere.

[0007] Chinese patent application CN202020729407.9 relates to a photocatalytic material in-situ infrared cell system. Its feature is that the utility model can realize real-time monitoring of light.

[0008] Chinese patent application CN201920868008.8 discloses an in-situ diffuse reflectance infrared spectroscopy reaction cell capable of providing a plasma environment and enabling in-situ detection of the structure of catalyst surface species in the plasma environment.

[0009] In summary, the most mature research at present is the plasma-coupled in-situ infrared cell based on the straight-through transmission type, which has simple structure and low cost, but has strict sample preparation requirements for the sample, cannot meet the measurement of special-shaped materials, and has a single fixed form of coupling plasma (mostly dielectric barrier discharge), has small space for modification; the diffuse reflectance type in-situ infrared cell gradually introduced in recent years has the technical characteristics of modular structure design, various sample coupling modes, and wide working condition range, and is easy to couple with various plasma forms and modify, but it must be pointed out that the existing commercial in-situ cells only consider application and characterization under variable temperature, variable gas pressure environment, but there is no existing commercial technical solution for the high-voltage introduction and insulation problems that must be solved for plasma in-situ reaction; at the same time, the existing technology mainly focuses on simple infrared spectrum collection, and lacks linkage diagnosis of gas phase transient products and steady-state products. SUMMARY

[0010] To solve the above technical problems, the application provides an in-situ infrared double-observation device with a variable plasma coupling structure and a method, which is based on an in-situ reaction / observation cavity with a variable structure, combined with a parameterized plasma power supply and a high-resolution emission spectrometer / infrared spectrometer to realize various forms of discharge plasma initiation, obtain typical emission spectra of gas-phase species and infrared spectra of surface adsorbed species through in-situ double-observation, and study the time evolution law thereof; meanwhile, a circulating water cooling / resistance heating system and a vacuum pump are used to realize wide-range adjustment of the temperature of raw material gas in the cavity, the temperature of the sample and the overall pressure in the cavity, combined with upper computer program control feedback to ensure the stability and safety of plasma initiation under the conditions of various electrode structures and temperature and pressure, and to realize the overall work flow of automatic in-situ reaction, observation collection, spectrum analysis and feedback monitoring.

[0011] To achieve the above object, the technical scheme adopted by the application is as follows:

[0012] An in-situ infrared double-observation device with a variable plasma coupling structure, comprising a plasma power supply unit, a gas supply and separation and purification unit, an in-situ reaction observation unit and a signal acquisition and control unit.

[0013] The plasma power supply unit comprises various plasma power supplies, a signal generator and a high-voltage transmission line.

[0014] The gas supply and separation and purification unit comprises a high-pressure steel cylinder, a stainless steel pipeline, a ball valve, a flow controller, a mixing tank, a gas-liquid separation device, a gas storage and transportation tank and a liquid storage and transportation tank; the high-pressure steel cylinder, the ball valve and the flow controller are connected through the stainless steel pipeline, each road reaction gas is configured in a fixed ratio, then is uniformly input into the gas inlet of the in-situ reaction observation unit through the mixing tank to form a gas supply system; the gas-liquid mixed products flowing out of the gas outlet of the in-situ reaction observation unit are introduced into the gas storage and transportation tank and the liquid storage and transportation tank through the stainless steel pipeline after passing through the low-temperature gas-liquid separation device, to form a separation and purification system.

[0015] The in-situ reaction observation unit is composed of an in-situ reaction observation cavity, an emission spectrometer and an infrared spectrometer, wherein the in-situ reaction observation cavity comprises a cuboid metal cavity frame, an insulating adhesive layer, an insulating sleeve, a variable needle electrode, a sealing flange, a quartz flange window, an infrared flange window, an infrared mirror, a catalytic material base, an infrared concave mirror, a resistance heating system, a water cooling circulating pump, a vacuum pump, a pressure gauge, an air inlet / outlet and a water inlet / outlet; the variable needle electrode is sealed and fixed by a flange structure after passing through the insulating sleeve, the insulating sleeve is embedded into the top end of the metal cavity frame and connected in parallel, the quartz flange window / infrared flange window is installed at other openings of the metal cavity frame according to the light path design, and finally the cavity of the in-situ reaction observation unit is formed after the insulating adhesive layer is attached to the closed inner surface of the metal cavity frame; the variable needle electrode is connected to the high-voltage end of the power supply as an anode through a high-voltage transmission line, and the catalyst base is grounded as a cathode; the gas inlet is directly connected to a mixing tank, the gas outlet is connected to the vacuum pump, the water inlet / outlet is connected to the water cooling circulating pump; the in-situ reaction observation cavity is placed on the external light path based on the cavity structure, and the in-situ reaction observation unit is composed of the emission spectrometer.

[0016] The signal acquisition control unit comprises a host computer and a signal transmission line, and the host computer is in communication connection with a signal generator, an emission spectrometer, an infrared spectrometer, a water cooling circulating pump, a flow controller and a resistance heating system through the signal transmission line.

[0017] Further, the plasma power supply is used to excite the generation of low-temperature plasma in the cavity of the in-situ reaction observation unit, and is one of a high-frequency alternating current source, a microsecond pulse power supply, a parameterized nanosecond pulse power supply and a radio frequency power supply.

[0018] Further, the in-situ reaction observation unit comprises a square cavity composed of a metal cavity frame, a needle electrode, an insulating sleeve, an insulating inner layer, a flange and a flange window, the metal cavity frame, the needle electrode and the flange are all made of stainless steel, and the insulating material is ceramic-doped epoxy resin; all the metal fasteners in the in-situ reaction observation unit are connected through a vacuum flange structure to ensure air tightness, and the insulating sleeve and the metal cavity of the in-situ reaction observation unit are sealed and fastened in a flange structure.

[0019] Further, the needle electrode comprises a micrometer, a stainless steel connecting rod, a quartz dielectric groove, a stainless steel needle electrode and a stainless steel plate electrode to form a needle / plate electrode with adjustable discharge gap and a plate-type dielectric barrier electrode; or a plasma jet type structure composed of a T-shaped quartz tube, a tungsten needle, a metal clamp, a polytetrafluoro fastener and a perfluorinated sealing ring.

[0020] Further, the metal flange and the quartz window piece form a quartz flange window, and the infrared window piece and the flange form an infrared flange window; the material of the infrared window piece is KBr or ZnSe or CaF2.

[0021] Further, the materials of the infrared mirror and the infrared concave mirror are gold-plated single crystal silicon, which are fixed in the corresponding optical path positions through the clamping groove structure reserved on the inner wall of the cavity to realize the mirror reflection and diffuse reflection of infrared light.

[0022] Further, the catalytic material base is a special-shaped closed structure composed of a square groove body and a cylindrical support, the base has a circulating water cooling channel, and the inlet and outlet of the circulating water path are led out at the bottom; the bottom of the square groove body in contact with the catalyst sheet is directly connected to the ground by a metal rod; the cylindrical support is wrapped with a resistance heating and thermocouple module, and a controller is separately led out.

[0023] Further, the gas inlet and the gas outlet are connected with a gas supply system and a separation and purification system respectively, the gas pressure level in the cavity is controlled through a vacuum pump and a manometer; the water inlet and outlet of the base form a loop with a water cooling circulating pump, the circulating water flows in from the bottom and out from the top, tap water is used as the raw material, and the flow rate is 0-5L / min.

[0024] The application also provides a test method of an in-situ infrared double observation device with a variable plasma coupling structure, comprising the following steps:

[0025] Step (1), based on experimental requirements, one of a needle type, a plate type, a dielectric barrier discharge and a jet structure is selected as a needle electrode and a cavity of an in-situ reaction observation unit for assembly;

[0026] Step (2), start all devices of a signal acquisition control unit, confirm that an emission spectrometer and a signal generator can normally trigger and acquire signals, and after the communication between the upper computer and each instrument is normal, preset experimental parameter information in the upper computer;

[0027] Step (3), open a high-pressure steel cylinder and a ball valve to make gas flow into the corresponding pipeline, the upper computer controls the purge gas to flow into the in-situ reaction observation unit according to the program, feeds back the background spectrum collected by the reflection spectrometer to the upper computer, drives a flow controller to realize valve switching and flow control of the raw gas, and then the raw gas flows into the in-situ reaction observation unit after being fully mixed;

[0028] Step (4), acquire and obtain the real-time spectrum of the raw material flowing through the in-situ reaction observation unit, feed back the signal to the signal generator and the water cooling circulating pump after the spectrum is solved by the upper computer, and the signal generator excites the plasma according to the preset parameter range;

[0029] Step (5), the reflection spectrometer is cyclically acquired, the plasma is confirmed to be initiated through the change of the spectrum signal, the signal intensity evolution trend with time is obtained after being transmitted to the upper computer for analysis, and the in-situ reaction observation is realized synchronously;

[0030] Step (6), adjust the resistance heating system and the vacuum pump to realize the temperature and pressure control of gas molecules in the cavity, and the spectrum acquisition signal is fed back to the signal generator after being inversely analyzed by the host computer, so that the stability of the plasma is ensured.

[0031] Step (7), when the acquisition signal appears abnormal change, the host computer controls the signal generator and the resistance heating system to stop working, further sends a signal to control the flow controller, the water cooling circulating pump, the reflection spectrometer and the vacuum pump to be closed, and simultaneously triggers an alarm.

[0032] Step (8), after the exception is eliminated, the alarm is turned off, the cavity of the in-situ reaction observation unit is reset, and steps (2)-(6) are cycled according to requirements.

[0033] The beneficial effects of the present application are:

[0034] The reported modified plasma in-situ infrared cell can only adopt a single plasma discharge form and does not consider the synchronous study of the gas phase reaction process, which is not conducive to obtaining comprehensive information of the plasma action process. The present application can effectively control the plasma initiation form by designing and replacing different electrode structures and equipping a wide adjustment range parameterized pulse source for excitation. At the same time, the in-situ double observation structure is designed on the cavity to realize the collection of in-situ emission spectrum / infrared spectrum of gas phase transient species / surface adsorbed species, so as to meet the description of the overall picture of the action mechanism of plasma in material surface modification and synergistic catalytic reaction. The variable electrode coupling structure, double observation design, insulation design and automatic control system are the core designs of the device. BRIEF DESCRIPTION OF DRAWINGS

[0035] The drawings accompanying the specification of the present application serve to provide further understanding of the present application, the illustrative embodiments of the present application and the description thereof serve to explain the present application, and do not constitute a limitation of the present application.

[0036] Figure 1 It is a front view of the overall structure of an in-situ infrared double observation device with a variable plasma coupling structure in an embodiment of the present application;

[0037] Figure 2 It is a sectional view of the variable electrode structure in the present application;

[0038] Figure 3 It is a typical discharge image of the plasma jet induced by the present application under atmospheric pressure and low pressure conditions;

[0039] Figure 4 It is a typical emission spectrum image synchronously collected by the present application when H2+CO2 plasma is induced;

[0040] Figure 5In-situ infrared spectra synchronously collected by the present application when H2+CO2 plasma is initiated.

[0041] Figure 1 The reference signs shown in the drawings are as follows:

[0042] Barometer 1, micrometer 2, insulating sleeve 3, gas outlet 4, infrared concave mirror 5, needle electrode 6, quartz flange window 7, infrared flange window 8, test sample 9, water outlet 10, water inlet 11, circulating water path 12, gas inlet 13, cavity ground 14, power ground 15, metal cavity frame 16, infrared reflecting mirror 17, gas-liquid separator 18, gas storage tank 19, liquid storage tank 20, infrared spectrometer 21, resistance heating system 22, infrared light source 23, emission spectrometer 24, high-pressure steel cylinder 25, ball valve 26, flow controller 27, mixing tank 28, water-cooled circulating pump 29, water-cooled tank 30, signal generator 31, plasma power supply 32, vacuum pump 33, gas chromatograph 34, upper computer 35, high-voltage transmission line 36, and insulating adhesive layer 37.

[0043] Figure 2 The reference signs shown in the drawings are as follows:

[0044] T-shaped quartz tube 38, copper foil 39, sample groove 40, needle electrode head 41, flat plate electrode head 42, dielectric-coated flat plate electrode head 43, fastener 44. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the present application clearer and more apparent, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0046] Example 1

[0047] The present application provides an in-situ infrared dual observation device with a variable plasma coupling structure. The infrared light source reaches the detector through the sample in the form of straight transmission and diffuse reflection. The transmission type in-situ infrared cell is difficult to couple with various discharge forms, so the diffuse reflection type structure is selected for modification.

[0048] As shown in Figure 1 , Figure 2 The in-situ infrared cell includes:

[0049] The multi-layer composite frame includes the insulating sleeve 3, the metal cavity frame 16 and the insulating adhesive layer 37.

[0050] Double observation light path, including English flange window 7, infrared flange window 8, infrared concave mirror 5 and infrared mirror 17;

[0051] Temperature control system, including water outlet 10, water inlet 11, circulating water cooling pump 29, water cooling tank 30 and resistance heating system 22; electrode structure:

[0052] Needle electrode 6, micrometer 2 and cavity ground 14;

[0053] Gas path, including air inlet 13, air outlet 4 and air pressure gauge 1.

[0054] In order to realize high voltage insulation and high mechanical strength of the cavity at the same time, the overall structure is supported by the metal cavity frame 16, and the high voltage needle electrode 6 is discharged from the metal cavity frame 16 by installing the insulating sleeve 3 and attaching the insulating attachment layer 37 on the closed inner surface of the metal frame;

[0055] The electrode structure part is fixed at the top of the cavity in the form of high voltage needle electrode 6 combined with insulating sleeve 3, and the specific electrode configuration can be referred to Figure 2 The electrode head of the needle electrode 6 can be replaced by flat electrode head 42 and dielectric coated flat electrode head 43 by thread fixing, and the discharge gap of the needle electrode 6 in the cavity can be accurately adjusted by micrometer 2; at the same time, the overall high voltage electrode structure can also be replaced by plasma jet form, and the T-shaped quartz tube 38 is inserted into the cavity through the insulating sleeve 3, the electrode connecting rod of the needle electrode 6 is connected with the high voltage transmission line 36, the copper foil 39 is attached on the quartz tube as the ground electrode, and the opening outside the cavity is sealed by fastener 44. The sample tank 40 is below the high voltage electrode structure, which is made of metal material and wrapped with insulating attachment layer 37 in the non-catalyst contact area, and there is a circulating water pipeline in the tank body for cooling.

[0056] The upper and lower sides of the cavity are respectively provided with air outlet 4, air inlet 13 and air pressure gauge 1, which are used for replacing and controlling the gas pressure in the in-situ reaction / observation cavity;

[0057] The double observation light path introduces infrared signal through the left and right plane infrared flange window 8, and realizes the conduction of diffuse reflection infrared light path on the surface of the test sample 9 by the combination of infrared mirror 17 and infrared concave mirror 5; the quartz flange window 7 is installed on the front of the cavity corresponding to the needle electrode 6 for in-situ diagnosis of discharge image and emission spectrum; the infrared plane mirror 17 is a plane mirror, and the infrared concave mirror 5 is a diffuse mirror. The test sample 9 is a material / catalyst.

[0058] The temperature control system is a resistance heating system 22, which uses resistance heating to heat the reaction atmosphere, and a circulating water channel is arranged in the cavity base, a circulating water cooling pump 29 and a water cooling tank 30 are installed, and the water inlet 11 and the water outlet 10 are connected to realize the cooling of the base to eliminate the thermal deformation of the base, so as to guarantee the airtightness and stability.

[0059] Because the reflected infrared signal under the diffuse reflection structure is generally weaker than the straight-through transmission structure, a photoconductive detector (mercury cadmium telluride, MCT) is selected on the infrared spectrometer 21 to improve the detection sensitivity for signal acquisition.

[0060] The plasma power supply 32 receives the instruction signal of the signal generator 31 to control the power supply parameter and outputs to the in-situ reaction / observation cavity through the high-voltage transmission line 36, and the stable product after reaction is purified through the gas-liquid separator 18 under the action of the vacuum pump 33 and then enters the gas storage tank 19 and the liquid storage tank 20, and then the gas chromatograph 34 is used for quantitative and qualitative detection.

[0061] Example 2

[0062] The test method of the variable plasma coupling structure in-situ infrared double observation device of the application comprises the following steps:

[0063] Step one: disassemble the quartz flange window 7, place the test sample 9 in the sample groove, install the high-pressure needle electrode 6 according to the requirement and install the micrometer 2 at the tail, adjust the needle electrode 6 to the appropriate height, then the needle electrode 6 and the insulating sleeve 3 are fixed and sealed through the flange structure and the metal cavity frame 16, and the quartz flange window 7 is sealed.

[0064] Step two: place the in-situ reaction / observation cavity loaded with the test sample 9 after sealing on the double observation light path, connect the gas inlet 13 and the gas outlet 4 of the cavity with the gas supply system and the separation and purification system respectively and check the airtightness, connect the water inlet 11 and the water outlet 10 of the base with the circulating water channel 12 and seal them;

[0065] Step three: connect the signal acquisition control unit and other all electric equipment power supply, input the preset experimental condition into the upper computer 35;

[0066] Step four: open the ball valve 26 of the high-pressure steel cylinder 25, and control the flow controller 27 through the upper computer 35 to guide the pure Ar gas into the mixing tank 28 and then flow into the cavity gas inlet 13 for pre-reaction high flow rate purging;

[0067] Step five: after purging for 20 minutes, control the vacuum system, the resistance heating system 22 and the circulating water cooling system through the upper computer 35, and confirm whether the atmosphere and pressure conditions in the cavity meet the experimental requirements through the barometer 1 and the resistance heating system 22;

[0068] Step six: After the cavity environment is stable, the emission spectrometer 24, the infrared light source 23 and the infrared spectrometer 21 are programmed by the upper computer 35 to collect the background spectrum under the condition of no discharge, and the effluent is detected by the gas chromatograph 34 at the same time;

[0069] Step seven: When the gas chromatograph 34 detects that the impurity components in the cavity are removed, feedback to the upper computer 35, control the flow controller to introduce H2 and CO2 as reaction raw materials, mix fully and then introduce into the reaction cavity;

[0070] The upper computer 35 communicates with the signal generator 31, the signal generator drives the plasma power supply 32 to excite, and the discharge plasma is generated on the surface of the needle electrode 6 and the test sample 9, and the active species generated interact with the surface of the sample 9;

[0071] Step eight: The upper computer 35 realizes linkage triggering of the emission spectrometer 24, the infrared spectrometer 21 and the signal generator 31, wherein the emission spectrometer 24 and the signal generator 31 are synchronously triggered and collected, and the infrared spectrometer 21 is collected at a fixed time after being triggered;

[0072] Step nine: After the reaction product passes through the gas-liquid separator 18, the gas storage tank 19 and the liquid storage tank 20, it enters the gas chromatograph 34 for qualitative and quantitative detection, and the real-time spectrum of the stable product is obtained;

[0073] Step ten: After the collection is completed, the signal generator 31, the emission spectrometer 24, the infrared light source 23 and the infrared spectrometer 21 are programmed by the upper computer 35 to stop working;

[0074] Step eleven: The upper computer 35 programs to introduce large-flux Ar gas for purging, and the environment is confirmed to be removed by the online chromatographic results, and finally the purification and separation system and the gas chromatograph are closed;

[0075] Step twelve: The quartz flange window 7 is disassembled and the test sample 9 is taken out, and the next detection is waited.

[0076] The present application provides an in-situ infrared double observation device with a variable plasma coupling structure for observation, wherein Figure 3 It is a typical discharge image of the plasma jet initiated by the present application under atmospheric pressure and low pressure conditions; Figure 4 It is a typical emission spectrum synchronously collected by the present application when H2+CO2 plasma is initiated; Figure 5 It is an in-situ infrared spectrum synchronously collected by the present application when H2+CO2 plasma is initiated.

Claims

1. An in-situ infrared dual-observation device with a variable plasma coupling structure, characterized in that: It includes a plasma power supply unit, a gas supply and separation purification unit, an in-situ reaction observation unit, and a signal acquisition and control unit; The plasma power supply unit includes various plasma power supplies, a signal generator, and a high-voltage transmission line; The gas supply and separation purification unit includes a high-pressure steel cylinder, stainless steel pipelines, ball valves, flow controllers, a mixing tank, a gas-liquid separator, a gas storage tank, and a liquid storage tank. The high-pressure steel cylinder, ball valve, and flow controller are connected by stainless steel pipelines. After the reaction gases are mixed in a fixed ratio, they are merged into the mixing tank and then evenly fed into the inlet of the in-situ reaction observation unit to form a gas supply system. The gas-liquid mixture flowing out of the outlet of the in-situ reaction observation unit passes through a low-temperature gas-liquid separator and is then introduced into the gas storage tank and the liquid storage tank through stainless steel pipelines to form a separation purification system. The in-situ reaction observation unit consists of an in-situ reaction observation cavity, an emission spectrometer, and an infrared spectrometer. The in-situ reaction observation cavity includes a cuboid metal cavity frame, an insulating layer, an insulating sleeve, a variable high-voltage electrode, a sealing flange, a quartz flange window, an infrared flange window, an infrared reflector, a catalyst material base, an infrared concave mirror, a resistance heating system, a water-cooled circulating pump, a vacuum pump, a pressure gauge, an inlet / outlet for gas, and an inlet / outlet for water. The variable high-voltage electrode passes through the insulating sleeve and is sealed and fixed using a flange structure; the insulating sleeve is integrally embedded in the metal cavity frame. The top of the cavity is connected in parallel. Infrared flange windows / quartz flange windows are installed at other openings of the metal cavity frame according to the optical path design. Finally, an insulating layer is attached to the closed part of the inner surface of the metal cavity frame to form the cavity of the in-situ reaction observation unit. The variable electrode is connected to the high-voltage end of the power supply through a high-voltage transmission line as the anode, and the catalyst base is grounded as the cathode. The gas inlet is directly connected to the mixing tank, the gas outlet is connected to the vacuum pump, and the water inlet and outlet are connected to the water-cooled circulation pump. Based on the cavity structure, the in-situ reaction observation cavity is placed on the external optical path and forms an in-situ reaction observation unit with the emission spectrometer. The signal acquisition and control unit includes a host computer and a signal transmission line. Through the signal transmission line, the host computer is communicatively connected to a signal generator, an emission spectrometer, an infrared spectrometer, a water-cooled circulating pump, a flow controller, and a resistance heating system. The high-voltage electrode is composed of a micrometer, a stainless steel connecting rod, a quartz dielectric tank, a stainless steel needle electrode, and a stainless steel plate electrode, forming a needle / plate electrode with an adjustable discharge gap and a plate dielectric barrier electrode; or it is a plasma jet type structure composed of a T-shaped quartz tube, a tungsten needle, a metal clamp, a polytetrafluoroethylene fastener, and a perfluoropolymer sealing ring. The catalyst material base is an irregular closed structure composed of a square tank and a cylindrical support. The base has a circulating water cooling channel and the inlet and outlet of the circulating water circuit are led out from the bottom. The bottom of the square tank in contact with the catalyst sheet is directly connected to the bottom ground by a metal rod. The cylindrical support is wrapped with resistance heating and thermocouple modules, and the controller is led out separately.

2. The in-situ infrared dual-observation device with a variable plasma coupling structure according to claim 1, characterized in that: The plasma power source is used to excite the generation of low-temperature plasma within the cavity of the in-situ reaction observation unit, and is one of a high-frequency AC source, a microsecond pulse power source, a parameterized nanosecond pulse power source, or a radio frequency power source.

3. The in-situ infrared dual-observation device with a variable plasma coupling structure according to claim 1, characterized in that: The in-situ reaction observation unit is a square cavity consisting of a metal cavity frame, a high-voltage electrode, an insulating sleeve, an insulating inner layer, a flange, and a flange window. The metal cavity frame, the needle electrode, and the flange are all made of stainless steel, and the insulating material is ceramic-doped epoxy resin. All metal fasteners in the in-situ reaction observation unit are connected by a vacuum flange structure to ensure airtightness. The insulating sleeve and the metal cavity of the in-situ reaction observation unit are sealed and fastened using a flange structure.

4. The in-situ infrared dual-observation device with a variable plasma coupling structure according to claim 1, characterized in that: Metal flanges and quartz windows together form a quartz flange window, while infrared windows and flanges together form an infrared flange window; the infrared windows are made of KBr, ZnSe, or CaF2.

5. The in-situ infrared dual-observation device with a variable plasma coupling structure according to claim 1, characterized in that: Both the infrared reflector and the infrared concave mirror are made of gold-plated single-crystal silicon. They are fixed in the corresponding optical path positions by a pre-reserved slot structure on the inner wall of the cavity to achieve specular reflection and diffuse reflection of infrared light.

6. The in-situ infrared dual-observation device with a variable plasma coupling structure according to claim 1, characterized in that: The air inlet and outlet are connected to the air supply system and the separation and purification system, respectively. The air pressure level in the cavity is controlled by a vacuum pump and a barometer. The water inlet / outlet of the base forms a loop with the water-cooled circulating pump. The circulating water enters from the bottom and exits from the top. Tap water is used as raw material, and the flow rate is 0-5 L / min.

7. A testing method for an in-situ infrared dual-observation device with a variable plasma coupling structure according to any one of claims 1-6, characterized in that, Includes the following steps: Step (1): Based on experimental requirements, select one of the following structures as the high-voltage electrode and assemble it with the cavity of the in-situ reaction observation unit: needle type / plate type / dielectric barrier discharge / jet structure. Step (2): Start all devices in the signal acquisition control unit, confirm that the emission spectrometer and signal generator can trigger and acquire signals normally, and after the communication between the host computer and each instrument is normal, preset the experimental parameter information in the host computer. Step (3): Open the high-pressure cylinder and ball valve to allow the gas to flow into the corresponding pipeline. The host computer controls the purge gas to enter the in-situ reaction observation unit according to the preset program. After the emission spectrometer collects the background spectrum, it feeds back to the host computer and drives the flow controller to realize valve switching and flow control of the raw material gas. After being fully mixed, the gas flows into the in-situ reaction observation unit. Step (4): Collect and obtain the real-time spectrum of the raw material after it flows through the in-situ reaction observation unit. After the spectrum is deciphered by the host computer, the signal is fed back to the signal generator and the water-cooled circulating pump. The signal generator excites plasma generation according to the preset parameter range. Step (5): The emission spectrometer collects data cyclically, and the plasma initiation is confirmed by the change of the spectral signal. The data is then transmitted to the host computer for analysis to obtain the evolution trend of the signal intensity over time. In-situ reaction observation is realized simultaneously. Step (6): Adjust the resistance heating system and vacuum pump to control the temperature and pressure of gas molecules in the cavity. After the spectral acquisition signal is reverse-analyzed by the host computer, it is fed back to the signal generator in real time for adjustment to ensure the stable initiation of plasma. Step (7): When the acquired signal changes abnormally, the host computer controls the signal generator and the resistance heating system to stop working, and further sends a signal to control the flow controller, water-cooled circulating pump, emission spectrometer and vacuum pump to shut down, and at the same time triggers the alarm. Step (8): After eliminating the abnormality, turn off the alarm, reset the cavity of the in-situ reaction observation unit, and repeat steps (2) to (6) according to the requirements.

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