Mobile sampling time-of-flight mass spectrometry detection device and application

Abstract

The invention discloses a mobile sampling time-of-flight mass spectrometry detection device and application, and belongs to the technical field of mass spectrometry. The device comprises a reaction tube, a sleeve, a moving mechanism, a grading air exhaust mechanism, a photoionization chamber and a reflective time-of-flight mass spectrometer, wherein the wall surface of the reaction tube is provided with multiple axial sampling areas; the sleeve is sleeved outside the reaction tube; the side wall of the sleeve is provided with a quartz nozzle; during working, the moving mechanism drives the sleeve to enable the quartz nozzle to be aligned with a sampling area, gas forms an ultrasonic molecular beam through the funnel, neutral molecules are ionized by the light source after graded gas extraction and pressure reduction, and ions are analyzed by the mass spectrometer. The device is used for research on product selectivity and reaction mechanism by spatial distribution of short-chain olefin prepared by Fischer-Tropsch synthesis, isomeride can be distinguished, axial species distribution can be accurately represented, and detection selectivity and reliability can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of mass spectrometry, in particular to a mobile sampling time-of-flight mass spectrometry detection device and application. BACKGROUND

[0002] Fischer-Tropsch synthesis is a mature route for preparing liquid fuels and chemical basic raw materials from synthesis gas (carbon monoxide / hydrogen) as raw materials, and has a basic position in low-carbon transformation. In recent years, it has attracted much attention in the field of sustainable fuels and short-chain olefin directed preparation. In industry, a fixed bed reactor is commonly used, and the system is a multiphase coupled process.

[0003] However, there are usually obvious temperature and composition gradients along the catalytic bed, resulting in non-uniform distribution of reactants, products and secondary reaction products in space. Accurate identification and quantification of these gas-phase intermediates that change with axial position are of key significance for analyzing chain growth and secondary conversion mechanisms, inhibiting side reactions, and optimizing reactions under conditions close to industrial conditions.

[0004] The "mobile sampling-molecular beam-vacuum ultraviolet photoionization-reflecting time-of-flight mass spectrometry" system described in the present application is exactly aimed at such spatial gradient and mechanism analysis needs: on the one hand, through near-threshold vacuum ultraviolet single-photon photoionization and mobile time-of-flight mass spectrometry, high selectivity identification of isomers / equal mass species is achieved; on the other hand, by means of movable sampling and axial positioning, species-position profiles along the bed are directly obtained, providing a key observation means for Fischer-Tropsch synthesis product distribution and mechanism research. SUMMARY

[0005] The present application aims to provide a mobile sampling time-of-flight mass spectrometry detection device and application to solve the problems raised in the background art.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solution: a mobile sampling time-of-flight mass spectrometry detection device, comprising the following parts:

[0007] A reaction tube, the wall surface of the reaction tube is provided with a plurality of sampling zones along the axial direction;

[0008] A sleeve, the sleeve is sleeved outside the reaction tube, and a quartz nozzle is arranged on the side wall of the sleeve, and the quartz nozzle is connected with a sealing joint;

[0009] A moving mechanism, the moving mechanism drives the sleeve to move axially;

[0010] A funnel, the tip of the funnel is inserted into the sealing joint and is connected with the sampling zone;

[0011] Three cavities are connected in sequence, the left cavity is connected with the funnel, the middle cavity is a photoionization chamber, a light source is arranged in the photoionization chamber, and the light source is used for photoionizing neutral molecules in the photoionization chamber into ions, and a reflection type time-of-flight mass spectrometer is arranged in the right cavity to analyze and detect the mass of the ions.

[0012] A hierarchical pumping module is arranged in the three cavities to form an ultrasonic molecular beam of the sampling gas and sequentially enter the three cavities.

[0013] Preferably, the hierarchical pumping module comprises a plurality of turbine pumps distributed in each cavity.

[0014] Preferably, the moving mechanism is a linear displacement platform arranged along the axis of the reaction tube.

[0015] Preferably, the sealing joint is a high-pressure threaded type, and the sealing joint adopts a metal ring gasket or a conical sealing structure, and the pressure resistance is 2-5MPa, and the temperature resistance is 500-800℃.

[0016] Preferably, more than three sampling areas are arranged on the reaction tube along the axis, the micropore array arranged in the sampling area has 5-7 holes, the single hole diameter is 0.5-1.2mm, and the interval distance is 12-24mm.

[0017] Preferably, the jet hole diameter of the quartz nozzle is 50-150um, and the jet hole is coaxially aligned with the funnel.

[0018] Preferably, the light source is a synchrotron radiation vacuum ultraviolet light source, and the energy is adjustable.

[0019] Preferably, the mass resolution of the time-of-flight mass spectrometer is 3000-6000 (at mass-to-charge ratio m / z=100), and the full-spectrum sampling period is 0.1s-1s.

[0020] The application also provides a use of the device, which is used for detecting the space distribution of short-chain olefins prepared by the Fischer-Tropsch synthesis, and studying the product selectivity and reaction mechanism.

[0021] Compared with the prior art, the application has the following beneficial effects:

[0022] 1. Precise capture of spatial gradient, providing a key observation means for reaction mechanism research

[0023] The device is aimed at the temperature and composition gradient problem commonly existing in Fischer-Tropsch synthesis catalytic bed, and realizes high-resolution detection of axial species distribution through "multi-sampling zone design + moving sampling mechanism". The reaction tube is provided with more than three sampling zones along the axial direction, each sampling zone is provided with 5-7 0.5-1.2mm micropore arrays, and the interval distance is controlled to be 12-24mm, which can cover the key reaction region of the catalytic bed; in combination with the sleeve mechanism driven by the linear displacement platform, the quartz nozzle can be accurately controlled to be connected with the target sampling zone, the gas phase products at different axial positions are collected point by point, and the "species-position" profile data are directly obtained. This design solves the pain point that the traditional detection is difficult to quantify the spatial non-uniform distribution, and can clearly observe the axial variation law of reactants, products and intermediates, and provides direct experimental basis for analyzing the chain growth and secondary conversion mechanism (such as olefin secondary hydrogenation).

[0024] 2. Full-process integrated optimization, improving detection efficiency and reliability

[0025] The device highly integrates the whole process of "moving sampling-molecular beam transmission-vacuum ultraviolet photoionization-reflecting time-of-flight mass spectrometry", and the cooperation of each component is good, so that the error and loss of intermediate links are effectively reduced. From the collection of gas from the micropore of the sampling zone to the accurate connection of the quartz nozzle and the funnel, then to the ultrasonic molecular beam transmission after staged pumping, and finally to the photoionization and mass spectrometry detection, the whole process does not need complex intermediate conversion steps. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a schematic diagram of a moving sampling time-of-flight mass spectrometry detection device;

[0027] Figure 2 It is a schematic diagram of a reaction tube, a sleeve and a moving mechanism;

[0028] Figure 3 It is a schematic diagram of a reaction tube;

[0029] Figure 4 It is a schematic diagram of a sleeve, a sealing joint and a funnel;

[0030] Figure 5 It is a schematic diagram of a reaction tube sampling;

[0031] Figure 6 (a) is a data graph that the spatial distribution has no influence on the product selectivity in the preparation of short-chain olefins by Fischer-Tropsch synthesis; Figure 6 (b) is a data graph that the spatial distribution has influence on the product selectivity in the preparation of short-chain olefins by Fischer-Tropsch synthesis;

[0032] Figure 7 It is a mass spectrometry data graph that the spatial distribution has influence on the product selectivity in the preparation of short-chain olefins by Fischer-Tropsch synthesis; Figure 7 a is an in-situ synthesis gas product data graph at sampling zone-1; Figure 7b-g are red triangle marks for amplified signals; the marked peak positions are: (b) m / z = 28.033, (c) m / z = 30.046, (d) m / z = 42.047 (e) m / z = 44.062, (f) m / z = 56.062, and (g) m / z = 58.076.

[0033] In the figure: 1, reaction tube; 2, sleeve; 3, sealing joint; 4, funnel; 5, photoionization chamber; 6, light source; 7, reflective time-of-flight mass spectrometer; 8, moving mechanism; 9, sampling area; 10, staged pumping module; 11, pressure stabilizing valve; 12, back pressure valve; 13, heating wire; 14, catalyst; 15, quartz cotton; 16, clamping groove. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0035] In combination with the drawings Figures 1-7 The detailed introduction of the mobile sampling time-of-flight mass spectrometry detection device is gradually unfolded from the overall architecture of the device, the cooperation of the core components, the work flow to the actual application, and the structural characteristics and application value of the device are clearly presented.

[0036] Overall architecture of the device and positioning of the core components

[0037] Firstly, the overall cognition of the device is established through Figure 1 The overall architecture of the device is established through (the overall schematic diagram of the device). The device takes "sampling-transmission-ionization-detection" as the core logic, and each component is arranged in order along the gas flow and signal transmission path: the left side is the reaction tube 1, the outside of which is sleeved with the sleeve 2, the side wall of the sleeve 2 is connected with the funnel 4 through the sealing joint 3, the funnel 4 is provided with three cavities which are communicated in sequence, the left side cavity is connected with the funnel 4, the middle is the photoionization chamber 5, the right side cavity is provided with the reflective time-of-flight mass spectrometer 7, and the staged pumping module 10 is arranged in the cavity; the staged pumping module 10 is a plurality of turbine pumps, which pumps each cavity and realizes the step-by-step pressure reduction of the three cavities from left to right (10 -2 Pa, 10 -4 Pa, 10 -6 Pa). The photoionization chamber 5 is provided with the light source 6 for photoionizing the neutral molecules into ions in the photoionization chamber 5, the sleeve 2 is connected with the moving mechanism 8 arranged along the axis of the reaction tube 1 (the moving mechanism 8 is connected with the pressure stabilizing valve 11 and the back pressure valve 12), the left side cavity is provided with the heating wire 13 and the catalyst 14, the right side cavity is provided with the quartz cotton 15, and the clamping groove 16 is arranged on the right side of the right side cavity. Figure 2(The connection between the moving mechanism 8 and the sleeve 2 is visible). The overall architecture realizes the seamless connection of the entire process from sampling of the reaction system to detection of ion signals.

[0038] Sampling adapter design between reaction tube 1 and sleeve 2

[0039] from Figure 3 (Diagram of the reaction tube) As can be seen, the wall of the reaction tube 1 is provided with multiple sampling zones 9 along the axial direction (e.g., in this embodiment, there are 4 sampling zones 9, namely sampling zone-1 to sampling zone-4). Each sampling zone 9 is an array of 5-7 micropores, with a single pore diameter of 0.5-1.2 mm. The spacing between adjacent sampling zones 9 is 12-24 mm. This design can cover different axial positions of the catalyst bed and capture spatial distribution differences. Figure 2 and Figure 4 The sleeve 2 is fitted outside the reaction tube 1, and its side wall is equipped with a quartz nozzle (orifice diameter 50-150µm). The quartz nozzle is connected to the funnel 4 through a high-pressure threaded sealing joint 3. The sealing joint 3 adopts a metal ring gasket or conical sealing structure, with a pressure resistance of 2-5MPa and a temperature resistance of 500-800℃, which can adapt to the high-temperature and high-pressure reaction conditions of Fischer-Tropsch synthesis. The moving mechanism 8 is a linear displacement platform that can drive the sleeve 2 to slide along the axial direction of the reaction tube 1, so that the quartz nozzle is precisely aligned with different sampling areas 9, realizing point-by-point sampling. Figure 2 The slider of the moving mechanism 8 is snapped together with the sleeve 2 to ensure stability during sliding.

[0040] Staged pumping and molecular beam transport system

[0041] Combination Figure 1 and Figure 4 The tip of the funnel 4 is inserted into the sealing joint 3 and aligned coaxially with the quartz nozzle. The staged air extraction module 10 consists of multiple turbine pumps. Figure 1 (Multiple directional lines are marked in the middle), the turbine pump is distributed in each chamber, so that each chamber maintains a different vacuum level and achieves gradual depressurization of the three chambers from left to right. The sampling gas is gradually depressurized from the high pressure environment (2-5MPa) of reaction tube 1 to form an ultrasonic molecular beam.

[0042] Photoionization and mass spectrometry detection unit

[0043] from Figure 1 As can be seen, the light source 6 inside the photoionization chamber 5 is a synchrotron radiation vacuum ultraviolet light source, whose beam can cover the path of the ultrasonic molecular beam, and can accurately photoionize neutral molecules into ions (and the energy of the light source 6 is adjustable, and the photoionization efficiency curve can be obtained through energy-resolved scanning); the outlet of the photoionization chamber 5 is docked with a reflective time-of-flight mass spectrometer 7, which has a mass resolution of 3000-6000 at a mass-to-charge ratio m / z=100, and a full-spectrum sampling period of 0.1s-1s. Figure 7The mass spectrometry data is collected by it, which can quickly and accurately perform mass analysis and signal detection of ions, and distinguish isomers or species with equal mass.

[0044] Core working process of the device

[0045] Taking the detection of short-chain olefins produced by Fischer-Tropsch synthesis as an example, combined with Figure 5 (Sampling diagram of reaction tube) and Figure 1 The complete workflow is as follows: First, the reaction gas (H2 / CO) enters reaction tube 1 through the flow controller, and the reaction occurs in the catalyst bed. Figure 5 Catalyst 14 is visible inside reaction tube 1; subsequently, the moving mechanism 8 drives the sleeve 2 to slide, aligning the quartz nozzle with the target sampling area (e.g., sampling area-1). The gaseous products (containing olefins, alkanes, and intermediates) in reaction tube 1 enter the quartz nozzle through the micropores of the sampling area; then, the product gas enters the funnel 4 through the sealed connector 3, and after being depressurized in the left chamber, it enters the photoionization chamber 5; in the photoionization chamber 5, the synchrotron radiation vacuum ultraviolet light source 6 ionizes the neutral molecules into ions, which enter the reflection time-of-flight mass spectrometer 7; finally, the mass spectrometer collects the ion signal and generates a mass spectrum (e.g., ...). Figure 7 By analyzing signal data from different sampling areas, the spatial distribution pattern of the product can be obtained (e.g., Figure 6 (The olefin / alkane ratios in different sampling areas are shown).

[0046] This apparatus is primarily used to study the effect of spatial distribution on product selectivity and reaction mechanism in the Fischer-Tropsch synthesis of short-chain olefins, combined with... Figure 6 (Product selectivity data chart) and Figure 7 (Mass spectrometry data graphs) can intuitively demonstrate application value: from Figure 6 It can be seen that along the axial direction of reaction tube 1 from the inlet end (sampling zone-1) to the outlet end (sampling zone-4), the olefin / alkane ratios of C2H4 / C2H6 and C3H6 / C3H8 of the nanocube catalyst remain basically unchanged, while the olefin-alkane ratio of the nanoparticle catalyst decreases significantly. This indicates that the product selectivity of the nanoparticle catalyst varies with spatial position, and that olefins are prone to secondary hydrogenation at the rear end of the bed, while the nanocube catalyst does not undergo secondary hydrogenation, providing direct evidence for the high olefin selectivity of the nanocube catalyst. Figure 7 In the mass spectrometry data, the signal peaks corresponding to different mass-to-charge ratios (m / z) are clearly distinguishable (e.g., m / z=28 corresponds to C2H4, m / z=30 corresponds to C2H6), and isomers can be distinguished by energy-resolved scanning (e.g., C3H6 with m / z=42 and cyclopropane), further revealing the types of reaction intermediates and providing a basis for clarifying the reaction mechanism and reaction pathway.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A mobile sampling time-of-flight mass spectrometry detection device, characterized in that, Includes the following parts: The reaction tube (1) has multiple sampling areas (9) along its axial direction on its wall surface. The sleeve (2) is fitted outside the reaction tube (1) and a quartz nozzle is provided on the side wall of the sleeve (2). The quartz nozzle is connected to a sealing joint (3). The moving mechanism (8) drives the sleeve (2) to move axially; Funnel (4), the tip of funnel (4) is inserted into the sealing joint (3) and connected to the sampling area (9); The three chambers are connected in sequence. The left chamber is connected to the funnel (4), the middle chamber is a photoionization chamber (5), and a light source (6) is installed inside the photoionization chamber (5). The light source (6) is used to photoionize the neutral molecules in the photoionization chamber (5) into ions. A reflection time-of-flight mass spectrometer (7) is installed in the right chamber to perform mass analysis and detection of the ions. The graded gas extraction module (10) is installed in three chambers to grade and depressurize the three chambers, so that the sampled gas forms an ultrasonic molecular beam and enters the three chambers in sequence.

2. The mobile sampling time-of-flight mass spectrometry detection device according to claim 1, characterized in that, The staged extraction module (10) includes multiple turbo pumps distributed in each chamber.

3. The mobile sampling time-of-flight mass spectrometry detection device according to claim 1, characterized in that, The moving mechanism (8) is a linear displacement platform arranged along the axial direction of the reaction tube (1).

4. The mobile sampling time-of-flight mass spectrometry detection device according to claim 1, characterized in that, The sealing joint (3) is a high-pressure threaded type. The sealing joint (3) adopts a metal ring gasket or conical sealing structure, with a pressure resistance of 2-5MPa and a temperature resistance of 500-800℃.

5. The mobile sampling time-of-flight mass spectrometry detection device according to claim 1, characterized in that, More than three sampling areas (9) are set along the axial direction on the reaction tube (1). The sampling area (9) is arranged with a micropore array of 5-7 pores, with a single pore diameter of 0.5-1.2 mm and an inter-area spacing of 12-24 mm.

6. The mobile sampling time-of-flight mass spectrometry detection device according to claim 1, characterized in that, The diameter of the nozzle orifice of the quartz nozzle is 50-150um and is aligned coaxially with the funnel (4).

7. The mobile sampling time-of-flight mass spectrometry detection device according to claim 1, characterized in that, The light source (6) is a synchrotron radiation vacuum ultraviolet light source and supports adjustable energy.

8. The mobile sampling time-of-flight mass spectrometry detection device according to claim 1, characterized in that, The time-of-flight mass spectrometer (7) has a mass resolution of 3000-6000 (at a mass-to-charge ratio of m / z=100) and a full-spectrum sampling period of 0.1s-1s.

9. An application of the mobile sampling time-of-flight mass spectrometry detection device as described in any one of claims 1-8, characterized in that, This device is used to study the effect of spatial distribution on product selectivity and reaction mechanism in the Fischer-Tropsch synthesis of short-chain olefins.

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