A mobile sampling time-of-flight mass spectrometry detection device and application

Abstract

The application discloses a mobile sampling time-of-flight mass spectrometry detection device and application, and belongs to the technical field of mass spectrometry analysis. The device comprises the following: a reaction tube with an axial multi-sampling area, a sleeve pipe sleeved outside the reaction tube and provided with a quartz nozzle on the side wall, a moving mechanism for driving the sleeve pipe to move axially, a staged pumping mechanism comprising a funnel and a multi-stage turbo pump, a photoionization chamber provided with a synchrotron radiation vacuum ultraviolet light source, and a reflection type time-of-flight mass spectrometer. When working, the moving mechanism drives the sleeve pipe so that the quartz nozzle is aligned with the sampling area, gas forms an ultrasonic molecular beam through the funnel, neutral molecules are ionized by the light source after pressure reduction through the staged pumping, and the mass spectrometer analyzes ions. The device is used for researching spatial distribution of short-chain olefins prepared through Fischer-Tropsch synthesis, product selectivity and reaction mechanism, can distinguish isomers, accurately characterizes axial species distribution, and improves detection selectivity and reliability.

Description

Technical Field

[0001] This invention relates to the field of mass spectrometry analysis technology, specifically to a mobile sampling time-of-flight mass spectrometry detection device and its application. Background Technology

[0002] Fischer-Tropsch synthesis is a mature route for producing liquid fuels and basic chemical feedstocks from syngas (carbon monoxide / hydrogen). It plays a fundamental role in the low-carbon transformation and has received considerable attention in recent years for its application in the targeted production of sustainable fuels and short-chain olefins. Industrially, fixed-bed reactors are commonly used, and the system is a multiphase coupled process.

[0003] However, there are usually significant temperature and composition gradients along the catalytic bed, which leads to non-uniform spatial distribution of reactants, products, and secondary reaction products. Accurately identifying and quantifying these gaseous intermediates that vary with axial position is of great significance for understanding the chain growth and secondary conversion mechanism, suppressing side reactions, and optimizing the reaction under near-industrial conditions.

[0004] The "mobile sampling-molecular beam-vacuum ultraviolet photoionization-reflection time-of-flight mass spectrometry" system described in this invention is specifically designed to address the needs of spatial gradient and mechanism analysis. On the one hand, it achieves highly selective identification of isomers / isomass species through near-threshold vacuum ultraviolet single-photon photoionization and mobile time-of-flight mass spectrometry. On the other hand, it directly obtains species-location profiles along the bed layer by means of mobile sampling and axial positioning, providing key observational means for the study of the distribution and mechanism of Fischer-Tropsch synthesis products. Summary of the Invention

[0005] The purpose of this invention is to provide a mobile sampling time-of-flight mass spectrometry detection device and its application to solve the problems mentioned in the background art.

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

[0007] The reaction tube has multiple sampling zones along its axial direction on its wall surface.

[0008] A sleeve is fitted over the outside of the reaction tube and a quartz nozzle is installed on the side wall of the sleeve. The quartz nozzle is connected to a sealing joint.

[0009] The moving mechanism drives the axial movement of the sleeve.

[0010] The funnel, with its tip inserted into the sealing joint and aligned with the sampling area;

[0011] The system consists of three interconnected chambers. The left chamber is connected to the funnel, the middle chamber is a photoionization chamber with a light source inside. The light source is used to photoionize neutral molecules in the photoionization chamber into ions. The right chamber is equipped with a reflectance time-of-flight mass spectrometer for mass analysis and detection of the ions.

[0012] The staged gas extraction module is installed in three chambers to depressurize the three chambers in stages, so that the sampled gas forms an ultrasonic molecular beam and enters the three chambers in sequence.

[0013] Preferably, the staged extraction module includes multiple turbopumps distributed in each chamber.

[0014] Preferably, the moving mechanism is a linear displacement platform arranged along the axial direction 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 conical sealing structure, with a pressure resistance of 2-5MPa and a temperature resistance of 500-800℃.

[0016] Preferably, three or more sampling zones are arranged along the axial direction on the reaction tube. The sampling zones are arranged with a micropore array of 5-7 pores, with a single pore diameter of 0.5-1.2 mm and an inter-zone spacing of 12-24 mm.

[0017] Preferably, the quartz nozzle has a nozzle diameter of 50-150 μm and is coaxially aligned with the funnel.

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

[0019] Preferably, the time-of-flight mass spectrometer 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.

[0020] The present invention also provides one use of the above-described apparatus for detecting the effect of spatial distribution on product selectivity and reaction mechanism in the Fischer-Tropsch synthesis of short-chain olefins.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. Accurately capturing spatial gradients provides a key observational tool for studying reaction mechanisms.

[0023] This device addresses the common temperature and compositional gradient issues in Fischer-Tropsch synthesis catalytic beds by employing a "multi-sampling zone design + moving sampling mechanism" to achieve high-resolution detection of axial species distribution. The reaction tube is equipped with three or more sampling zones along the axial direction. Each zone utilizes an array of 5-7 micropores (0.5-1.2 mm) with a spacing of 12-24 mm, covering key reaction areas of the catalytic bed. Combined with a sleeve mechanism driven by a linear displacement platform, it precisely controls the docking of the quartz nozzle with the target sampling zone, collecting gaseous products at different axial positions point by point, directly obtaining "species-location" profile data. This design overcomes the difficulty of quantifying spatially non-uniform distribution in traditional detection methods, clearly observing the axial variation patterns of reactants, products, and intermediates, providing direct experimental evidence for elucidating chain growth and secondary transformation mechanisms (such as secondary hydrogenation of olefins).

[0024] 2. End-to-end integrated optimization improves testing efficiency and reliability.

[0025] The device highly integrates the entire process of "mobile sampling - molecular beam transmission - vacuum ultraviolet photoionization - reflective time-of-flight mass spectrometry," with strong synergy among components, effectively reducing errors and losses in intermediate steps. From gas collection through micropores in the sampling area, to the precise docking of the quartz nozzle and funnel, to the ultrasonic molecular beam transmission after staged gas extraction, and finally to photoionization and mass spectrometry detection, the entire process requires no complex intermediate conversion steps. Attached Figure Description

[0026] Figure 1 A schematic diagram of a mobile sampling time-of-flight mass spectrometry detection device;

[0027] Figure 2 A schematic diagram of the reaction tube, sleeve, and moving mechanism;

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

[0029] Figure 4 Schematic diagram of the sleeve, sealing joint, and funnel;

[0030] Figure 5 This is a schematic diagram of the sampling process in the reaction tube.

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

[0032] Figure 7 This is a mass spectrometry image showing the effect of spatial distribution on product selectivity in the Fischer-Tropsch synthesis of short-chain olefins. Figure 7 a is a graph showing the in-situ syngas product data at sampling area -1; Figure 7bg represents the amplified signal marked by the red triangle; the peak positions of the markers 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 diagram: 1. Reaction tube; 2. Sleeve; 3. Sealing joint; 4. Funnel; 5. Photoionization chamber; 6. Light source; 7. Time-of-flight mass spectrometer (TOF-MS); 8. Moving mechanism; 9. Sampling area; 10. Staged gas extraction module; 11. Pressure regulating valve; 12. Back pressure valve; 13. Heating wire; 14. Catalyst; 15. Quartz wool; 16. Slot. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Combined with appendix Figures 1-7 From the overall architecture, core component collaboration, workflow to practical applications, this paper gradually unfolds a detailed introduction to the mobile sampling time-of-flight mass spectrometry detection device, clearly presenting the structural features and application value of the device.

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

[0037] Firstly, through Figure 1 (Overall schematic diagram of the device) To establish an overall understanding of the device, which operates on the core logic of "sampling-transmission-ionization-detection," the components are arranged in an orderly manner along the gas flow and signal transmission path: On the left is the reaction tube 1, which is fitted with a sleeve 2. The side wall of sleeve 2 is connected to a funnel 4 via a sealing joint 3. Three sequentially connected chambers are located at the end of funnel 4 furthest from the sealing joint 3. The left chamber is connected to funnel 4, the middle chamber is a photoionization chamber 5, and the right chamber houses a reflectance time-of-flight mass spectrometer 7. A staged gas extraction module 10 is installed within the chamber; the staged gas extraction module 10 consists of multiple turbopumps that extract gas from each chamber, achieving a step-by-step depressurization of the three chambers from left to right (10 levels in total). -2 Pa, 10 -4 Pa, 10 -6 Pa). A light source 6 is provided inside the photoionization chamber 5 to photoionize neutral molecules into ions within the chamber. The sleeve 2 is connected to a moving mechanism 8 arranged axially along the reaction tube 1. 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 for 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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