Molecular beam mass spectrometry detection device for plasma catalytic components of gas-liquid phase reactants

Abstract

The invention belongs to the technical field of mass spectrum analyzers, and particularly relates to a gas-liquid phase reactant plasma catalytic component molecular beam mass spectrum detection device which comprises a plasma catalytic reactor, a radio frequency driving discharge device, a microsyringe, a mass spectrum first-stage cavity and a molecular beam mass spectrum analyzer, a microsyringe is adopted to control the sample injection flow of a liquid-phase reactant, a mass flow meter is adopted to control the sample injection flow of a gas-phase reactant, and a radio frequency is adopted to drive a discharge device to discharge, so that the problem that a mass spectrum sample injection port is blocked due to excessive injection of the liquid-phase reactant is avoided, the stability of a reaction system is improved, and the experimental operation difficulty is reduced; the reaction time is greatly saved; the device is combined with a high-resolution molecular beam mass spectrometry analyzer, so that simultaneous high-mass-resolution and high-time-resolution online monitoring of reaction neutral products, ions and active species of gas-phase and liquid-phase reactants under the condition of plasma catalytic reaction is successfully realized.

Description

Technical Field

[0001] The invention belongs to the technical field of mass spectrometers, in particular to a molecular beam mass spectrometer detection device for gas-liquid phase reactant plasma catalytic components. Background Art

[0002] After decades of long, incremental development, plasma catalysis is now facing a rapid development phase. Compared with traditional thermal catalysis, the synergistic effect between plasma and catalyst shows great promise for improving conversion or increasing selectivity, so plasma catalysis has attracted increasing attention. Researchers have found that plasma catalysis shows better performance in many applications, including methane conversion, nitrogen oxide reduction, and nitrogen fixation, compared with pure plasma or pure catalytic conditions. However, the underlying mechanisms of these beneficial synergistic effects remain unclear to date. This is mainly due to the many possible plasma components and plasma-induced effects that may lead to such observed synergistic effects.

[0003] Molecular beam mass spectrometry is an analytical method that combines molecular beam sampling technology with mass spectrometry technology. It can achieve subatmospheric pressure and atmospheric pressure (10 2 ~10 5 The method was first used in the 1960s and 1970s, and has been widely used in chemical reaction kinetics, combustion chemistry, and plasma chemistry. Compared with spectral diagnosis, molecular beam mass spectrometry can simultaneously detect various species in the system, including ions, atoms, and free radicals, has high sensitivity in detecting ion species, and is relatively easy to judge unknown species. It has become an important diagnostic method in many plasma systems. However, the interface between the plasma catalytic reactor and the molecular beam mass spectrometer requires special design, especially when the reactants of the plasma catalytic system are gas and liquid, the liquid is easy to block the inlet of the molecular beam mass spectrometer. Summary of the invention

[0004] In view of the above problems existing in the existing plasma catalytic reactor and molecular beam mass spectrometer, the object of the present invention is to provide a molecular beam mass spectrometer detection device for plasma catalytic components of gas-liquid reactants.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] The invention comprises a plasma catalytic reactor, a radio frequency driven discharge device, a micro-injector, a mass spectrometer first-stage cavity and a molecular beam mass spectrometer, wherein the plasma catalytic reactor comprises a quartz tube, an inner quartz tube, copper wire and an annular wire mesh, the left end of the quartz tube is sealedly connected to a gas inlet, the right end of the quartz tube is sealedly connected to a quartz disc with an opening, a branch pipe is provided on the quartz tube, and the two ends of the branch pipe are respectively connected to the micro-injector and the inside of the quartz tube; the inner quartz tube is arranged inside the quartz tube, the left end of the inner quartz tube passes through the quartz tube and is connected from the left end to the inner quartz tube. Copper wire is passed through the tube; a catalyst is installed between the quartz tube and the inner lining quartz tube, an annular wire mesh is wound around the outside of the quartz tube between the branch tube and the quartz disc, one end of the radio frequency driven discharge device is grounded and connected to the annular wire mesh, and the other end is connected to the copper wire; the left end of the first-stage cavity of the mass spectrometer is sealed and connected to the quartz disc, the right end of the first-stage cavity of the mass spectrometer is provided with a differential electrode connected to a molecular beam mass spectrometer, and the side walls of the first-stage cavity of the mass spectrometer are respectively provided with a branch port connecting a valve and a molecular pump for maintaining the vacuum degree of the first-stage cavity of the mass spectrometer, and a branch port connected to a vacuum gauge for measuring the vacuum degree.

[0007] Wherein: the left end of the quartz tube is open and provided with a sealing connector, and the left end of the lined quartz tube can be relatively movably sealed and connected to the sealing connector; the sealing connector is provided with a gas inlet, and a mass flowmeter for controlling the gas injection flow rate is provided in the pipeline of the gas inlet.

[0008] The gas flow rate of the mass flow meter can be adjusted in the range of 0 to 10 L / min; the liquid injection speed of the micro-injector can be adjusted in the range of 0 to 2000 μL / min.

[0009] The right end of the annular wire mesh is flush with the right end of the quartz tube lined with the wire mesh, and the distance between the wire mesh and the quartz disc can be adjusted. The left end of the annular wire mesh is flush with the branch pipe.

[0010] A bracket with holes is arranged outside the right end of the inner-lined quartz tube, and the catalyst is arranged between the branch pipe and the bracket and is carried by the bracket.

[0011] The axial center lines of the quartz tube, the inner lining quartz tube, the quartz disc, the annular wire mesh and the differential electrode are collinear.

[0012] The advantages and positive effects of the present invention are:

[0013] 1. The present invention adopts a micro-injector to control the injection flow rate of liquid phase reactants, adopts a mass flowmeter to control the injection flow rate of gas phase reactants, and adopts a radio frequency driven discharge device to discharge, thereby avoiding the problem of blockage of the mass spectrometer injection port due to excessive injection of liquid phase reactants, improving the stability of the reaction system, reducing the difficulty of experimental operation, and greatly saving reaction time.

[0014] 2. The present invention is combined with a high-resolution molecular beam mass spectrometer to successfully achieve simultaneous high-mass resolution and high-time resolution online monitoring of neutral reaction products, ions and active species of gas and liquid reactants under plasma catalytic reaction conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the present invention;

[0016] Figure 2 The mass spectra of the intermediate products and products of the present invention are compared in the case of discharge with a catalyst added and discharge without a catalyst added (i.e., an empty tube);

[0017] Figure 3 This is the plasma catalytic mass spectrum of the present invention;

[0018] Among them: 1 is a radio frequency driven discharge device, 2 is a micro-injector, 3 is the first-stage cavity of the mass spectrometer, 4 is a molecular beam mass spectrometer, 5 is a quartz tube, 6 is a quartz disc, 7 is a branch pipe, 8 is a lined quartz tube, 9 is a copper wire, 10 is a ring-shaped wire mesh, 11 is a catalyst, 12 is a branch port connected to a valve, 13 is a molecular pump, 14 is a branch port connected to a vacuum gauge, 15 is a differential electrode, 16 is a sealing connector, 17 is a gas inlet, 18 is a mass flow meter, and 19 is a bracket. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with the accompanying drawings.

[0020] like Figure 1As shown, the present invention includes a plasma catalytic reactor, a radio frequency driven discharge device 1, a micro-injector 2, a mass spectrometer first-stage cavity 3 and a molecular beam mass spectrometer 4. The plasma catalytic reactor includes a quartz tube 5, a lined quartz tube 8, a copper wire 9 and a ring-shaped wire mesh 10. The left end of the quartz tube 5 is sealed and connected to a gas inlet 17, and the right end of the quartz tube 5 is sealed and connected to a quartz disc 6 with an opening. A branch pipe 7 is provided on the quartz tube 5, one end of the branch pipe 7 is connected to the micro-injector 2 for controlling the injection flow rate of the liquid sample, and the other end of the branch pipe 7 is connected to the inside of the quartz tube 5. The liquid in the micro-injector 2 is The injection speed can be adjusted in the range of 0 to 2000 μL / min; the lined quartz tube 8 is arranged inside the quartz tube 5, the left end of the lined quartz tube 8 passes through the quartz tube 5, and a copper wire 9 is passed from the left end to the inside of the lined quartz tube 8; a catalyst 11 is installed between the quartz tube 5 and the lined quartz tube 8, and a ring-shaped wire mesh 10 is wrapped around the outside of the quartz tube 5 between the branch pipe 7 and the quartz disc 6, one end of the radio frequency driven discharge device 1 is grounded and connected to the ring-shaped wire mesh 10, and the other end is connected to the copper wire 9; the ring-shaped wire mesh 10 is only used to connect to the radio frequency driven discharge device 1 for conductivity, so the mesh size and mesh number are not limited. The left end of the first-stage mass spectrometer cavity 3 is tightly connected to the quartz disk 6 through a vacuum sealing ring, and the right end of the first-stage mass spectrometer cavity 3 is provided with a differential electrode 15 connected to the molecular beam mass spectrometer 4. A branch port is provided on the upper side wall of the first-stage mass spectrometer cavity 3 to connect the valve 12 and the molecular pump 13 for maintaining the vacuum degree of the first-stage mass spectrometer cavity 3; a branch port is also provided on the lower side wall of the first-stage mass spectrometer cavity 3 to connect the vacuum gauge 14 for vacuum degree measurement.

[0021] The quartz tube 5 of this embodiment is a hollow round tube, the left end of which is open and provided with a sealing connector 16; the lined quartz tube 8 of this embodiment is a hollow round tube, the left end of which is relatively movable and sealedly connected to the sealing connector 16. The sealing connector 16 is provided with a gas inlet 17 connected to the inside of the quartz tube 5, and a mass flowmeter 18 for controlling the gas injection flow rate is provided in the pipeline of the gas inlet 17, and the gas flow rate of the mass flowmeter 18 is adjusted in the range of 0 to 10 L / min.

[0022] The quartz disc 6 of this embodiment has a hole in the center, and the center hole diameter is 0.01-2 mm. The quartz disc 6 is tightly connected to the right end of the quartz tube 5. The axial center lines of the quartz tube 5, the inner lining quartz tube 8, the quartz disc 6, the annular wire mesh 10 and the differential electrode 15 are collinear.

[0023] In this embodiment, the right end of the annular wire mesh 10 is flush with the right end of the lining quartz tube 8 and the distance between the annular wire mesh 10 and the quartz disc 6 can be adjusted within a range of 0 to 200 mm. The left end of the annular wire mesh 10 is flush with the branch pipe 7 .

[0024] In this embodiment, a bracket 19 with holes is provided on the right end of the inner lining quartz tube 8, and the catalyst 11 is installed between the branch pipe 7 and the bracket 19 and carried by the bracket 19. The bracket 19 is made of polytetrafluoroethylene, and the holes on the bracket 19 are used to pass gas samples and / or liquid samples.

[0025] The radio frequency driven discharge device 1 of the present invention is a commercially available product, purchased from a low temperature plasma experimental power supply produced by Nanjing Suman Electronics Co., Ltd., model CTP-2000K.

[0026] Experimental Example 1

[0027] like Figure 1 , Figure 2 As shown, the central aperture of the quartz disc 6 is 0.01mm, the distance between the annular wire mesh 10 and the right end of the inner quartz tube 8 and the quartz disc 6 is adjusted to 5mm, the gas flow rate of the mass flowmeter 18 is 15mL / min, the sampled gas material is a mixture of CH4 and N2, and the volume flow rate ratio of CH4 to N2 is 1:1; the liquid injection speed of the micro-injector 2 is 0μL / min, that is, there are only gas phase reactants and no liquid phase reactants. The catalyst 11 installed between the quartz tube 5 and the inner quartz tube 8 is a commercially available product, purchased from Suzhou Licheng Gas Equipment Co., Ltd., a special A106 iron catalyst for ammonia decomposition.

[0028] Working principle: The gas phase reactants CH4 and N2 mixed gas undergo plasma catalytic reaction under the conditions of catalyst and dielectric barrier discharge to generate products NH3 and CH3NH2. The molecular beam mass spectrometry ionization method is vacuum ultraviolet lamp ionization. Figure 2 Shown are the mass spectra comparing the intermediate products and products of discharge with catalyst added and discharge without catalyst added, i.e., empty tube discharge.

[0029] Experimental Example 2

[0030] like Figure 1 , Figure 3 As shown, the central aperture of the quartz disc 6 is 0.01mm, the distance between the annular wire mesh 10 and the right end of the inner quartz tube 8 and the quartz disc 6 is adjusted to 5mm, the gas flow rate of the mass flow meter 18 is 15mL / min, the injected gas substance is a mixture of CH4 and N2, and the volume flow rate ratio of CH4 to N2 is 1:1; the liquid injection speed of the micro-injector 2 is 5μL / min, and the liquid substance is cyclohexanone. The catalyst 11 installed between the quartz tube 5 and the inner quartz tube 8 is a Ni / SiAlO catalyst.

[0031] Working principle: The gas phase reactant is a mixture of CH4 and N2, and the liquid phase reactant is cyclohexanone. Plasma catalytic reaction occurs under the conditions of catalyst and dielectric barrier discharge to generate the product cyclohexanone cyanohydrin. The molecular beam mass spectrometry ionization method is vacuum ultraviolet lamp ionization. Figure 3 Shown is the plasma catalytic mass spectrum after adding this system.

Claims

1. A molecular beam mass spectrometry detection device for gas-liquid phase reactant plasma catalytic components, characterized in that: The invention comprises a plasma catalytic reactor, a radio frequency driven discharge device (1), a micro-injector (2), a mass spectrometer first-stage cavity (3) and a molecular beam mass spectrometer (4), wherein the plasma catalytic reactor comprises a quartz tube (5), a quartz lining tube (8), a copper wire (9) and a ring-shaped wire mesh (10), the left end of the quartz tube (5) is sealedly connected to a gas injection port (17), the right end of the quartz tube (5) is sealedly connected to a quartz disc (6) with an opening, a branch tube (7) is provided on the quartz tube (5), and the two ends of the branch tube (7) are respectively connected to the inside of the micro-injector (2) and the quartz tube (5); the quartz lining tube (8) is arranged inside the quartz tube (5), the left end of the quartz lining tube (8) passes through the quartz tube (5) and is connected from the left end to the inside of the quartz lining tube (8). A copper wire (9) is passed through the quartz tube (5) and the inner lining quartz tube (8). A catalyst (11) is installed between the quartz tube (5) and the inner lining quartz tube (8). The quartz tube (5) between the branch tube (7) and the quartz disc (6) is wound with an annular wire mesh (10). One end of the radio frequency driven discharge device (1) is grounded and connected to the annular wire mesh (10), and the other end is connected to the copper wire (9). The left end of the mass spectrometer first-stage cavity (3) is sealed and connected to the quartz disc (6). The right end of the mass spectrometer first-stage cavity (3) is provided with a differential electrode (15) connected to a molecular beam mass spectrometer (4). The side walls of the mass spectrometer first-stage cavity (3) are respectively provided with a branch port connection valve (12) and a molecular pump (13) for maintaining the vacuum degree of the mass spectrometer first-stage cavity (3), and a branch port connection vacuum gauge (14) for measuring the vacuum degree.

2. The gas-liquid phase reactant plasma catalytic component molecular beam mass spectrometry detection device according to claim 1, characterized in that: The left end of the quartz tube (5) is open and provided with a sealing connector (16); the left end of the inner lining quartz tube (8) is relatively movable and sealedly connected to the sealing connector (16); a gas inlet (17) is provided on the sealing connector (16); a mass flowmeter (18) for controlling the gas inlet flow rate is provided in the pipeline of the gas inlet (17).

3. The gas-liquid phase reactant plasma catalytic component molecular beam mass spectrometry detection device according to claim 2, characterized in that: The gas flow rate of the mass flow meter (18) can be adjusted in the range of 0 to 10 L / min; the liquid injection speed of the micro-injector (2) can be adjusted in the range of 0 to 2000 μL / min.

4. The gas-liquid phase reactant plasma catalytic component molecular beam mass spectrometry detection device according to claim 1, characterized in that: The right end of the annular wire mesh (10) is flush with the right end of the quartz tube (8) and the distance between the annular wire mesh and the quartz disc (6) can be adjusted. The left end of the annular wire mesh (10) is flush with the branch pipe (7).

5. The gas-liquid phase reactant plasma catalytic component molecular beam mass spectrometry detection device according to claim 1, characterized in that: A bracket (19) with holes is provided on the outside of the right end of the inner lining quartz tube (8), and the catalyst (11) is installed between the branch pipe (7) and the bracket (19) and is supported by the bracket (19).

6. The gas-liquid phase reactant plasma catalytic component molecular beam mass spectrometry detection device according to claim 1, characterized in that: The axial center lines of the quartz tube (5), the inner lining quartz tube (8), the quartz disc (6), the annular wire mesh (10) and the differential electrode (15) are collinear.

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