A research device and method for gas-solid heterogeneous catalytic reaction

Abstract

The application discloses a research device and a research method for gas-solid heterogeneous catalytic reaction, and the device comprises three independent temperature control furnace hearths, which realize gas high-temperature radical activation, fixed bed working condition catalytic reaction and low-temperature isotope radical capture in sequence, and can accurately disassemble the multi-coupling gas-solid heterogeneous catalytic reaction process by matching a staged gas distribution module and a mass spectrum detection module. By comparison between a blank group and an experimental group and isotope labeling tracing, the L-H and E-R core reaction mechanisms can be directly distinguished; by independent program heating of each furnace hearth, multi-dimensional reaction kinetics parameters can be obtained. The research device adopts a modular design and can be independently prepared or integrated in an existing chemical adsorption equipment, solves the problems of low mechanism distinguishing precision, difficult intermediate product detection and single characterization dimension of a traditional characterization equipment, is suitable for mechanism research of various radical type gas-solid heterogeneous catalytic reactions, and has wide application prospects in scientific research and industrial application.

Description

Technical Field

[0001] This invention relates to the fields of catalytic reaction characterization, gas free radical detection, and catalytic mechanism research. Specifically, it relates to a research device and method for gas-solid heterogeneous catalytic reactions, which is particularly suitable for identifying the mechanism and characterizing the kinetic parameters of free radical heterogeneous catalytic reactions occurring on the surface of a solid catalyst involving multiple gas molecules. Background Technology

[0002] Gas-solid heterogeneous catalysis is a core technology in chemical, energy, and environmental fields. Typical reactions such as methane coupling, hydrocarbon conversion, and gas-phase oxidation all rely on solid catalysts for efficient conversion. In heterogeneous catalytic reaction systems involving multiple gases, multi-stage coupled processes such as free radical evolution, gas-phase mass transfer, surface adsorption reactions, and product desorption are common. The core reaction mechanisms are mainly divided into two categories: the Langmuir-Hinshelwood (LH) mechanism and the Eley-Rideal (ER) mechanism. In the LH mechanism, two reactants are co-adsorbed on the catalyst surface before reacting, while in the ER mechanism, a single reactant is adsorbed on the catalyst surface, and the gas-phase reactant reacts directly with the adsorbed substance. The kinetics, reaction pathways, and rate-controlling steps of the two mechanisms differ significantly, directly determining the catalyst design optimization and reaction process parameter control.

[0003] Taking the methane coupling reaction as a typical example, its core reaction pathway involves the high-temperature activation of methane to generate methyl radicals. After the radicals desorb and enter the gas phase, they migrate via mass transfer to different active sites on the catalyst, undergoing a CC coupling reaction. This process involves the simultaneous coupling effect of gas-phase radical reactions and catalyst surface reactions. Existing traditional catalytic characterization equipment and research methods have significant technical shortcomings: First, the reaction processes are highly coupled, making it impossible to independently separate individual processes such as gas activation, surface reactions, radical evolution, and product desorption, thus hindering the accurate capture of gas-phase radical intermediates. Second, there is a lack of targeted isotope capture and low-temperature stabilization mechanisms, making it easy for active radical intermediates to undergo secondary reactions, thus preventing precise tracing of the reaction pathway. Third, it is impossible to directly identify the LH and ER reaction mechanisms, and only indirect inferences can be made through macroscopic product distribution, resulting in low accuracy in mechanism studies. Fourth, traditional equipment uses integrated temperature control, which cannot achieve independent programmed temperature characterization of each stage of the reaction, resulting in single-dimensional kinetic parameters that are difficult to comprehensively analyze the essence of the reaction.

[0004] Meanwhile, existing commercial chemisorption analyzers and temperature-programmed reaction equipment have limited functionality, only capable of routine adsorption, desorption, and reaction testing. They lack integrated functions such as free radical activation, low-temperature capture, and isotope tracing, failing to meet the needs of mechanism research for complex free radical-based heterogeneous catalytic reactions. This limits the added value and application scenarios of these devices. Therefore, developing a modularly integrated method and apparatus for studying gas-solid heterogeneous catalytic reactions—one that can disassemble the reaction process, accurately identify the reaction mechanism, characterize kinetic parameters in multiple dimensions, and is designed to address this critical technical challenge. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a research apparatus and method for gas-solid heterogeneous catalytic reactions.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A research device for gas-solid heterogeneous catalytic reaction includes three independently temperature-controlled reaction chambers connected and interconnected, a precise gas distribution module, a low-temperature capture and exchange module, and a mass spectrometry detection module; The three-section independently temperature-controlled reaction furnace includes a gas activation zone, a free radical reaction zone, and a low-temperature free radical capture zone arranged sequentially along the airflow direction, and each is equipped with an independent temperature control component; The precise gas mixing module includes a test reaction gas inlet, a reaction gas mixing inlet, and a capture gas mixing inlet. The test reaction gas inlet is connected to the gas activation zone and is used to activate the introduced reaction gas F1 at high temperature to generate a gaseous free radical intermediate. The reaction gas mixing inlet is connected between the gas activation zone and the free radical reaction zone and is used to introduce reaction gas F2, so that reaction gas F2 mixes with the activated gaseous free radical intermediate and enters the free radical reaction zone together. The capture gas mixing inlet is located between the free radical reaction zone and the low-temperature free radical capture zone and is used to introduce isotope capture gas F3. The low-temperature capture exchange module is located inside the low-temperature free radical capture zone. The low-temperature free radical capture zone is used to provide a low-temperature environment, and the low-temperature capture exchange module is used for the exchange reaction between the isotope capture gas F3 and the reacted gaseous free radical intermediate to capture a stable and active intermediate. The mass spectrometry detection module is connected to the exhaust gas outlet of the low-temperature free radical capture zone, and extracts a trace gas flow F5 from the exhaust gas F4 for real-time detection of the components and content of the captured and exchanged exhaust gas.

[0007] Furthermore, this device has a modular integrated structure. The three independently temperature-controlled reaction furnaces, the precise gas distribution module, the low-temperature capture and exchange module, and the mass spectrometry detection module are all independent and detachable modules. They can be assembled independently as a dedicated catalytic reaction characterization device, or integrated as a functional expansion module into existing chemisorption analyzers and programmed temperature characterization devices.

[0008] Furthermore, the temperature control ranges of the gas activation zone, the free radical reaction zone, and the low-temperature free radical capture zone are mutually adapted and differentiated. The temperature control range of the gas activation zone is 300–1200°C to meet the requirements of high-temperature gas activation for free radical production. The temperature control range of the free radical reaction zone is room temperature–800°C to adapt to the fixed-bed catalytic reaction conditions. The temperature control range of the low-temperature free radical capture zone is room temperature–600°C to meet the requirements of low-temperature stable capture of free radicals and suppress secondary reactions of intermediate products. For the heating process, the heating rate is 1–10°C / min, and the temperature control accuracy is ±0.5°C.

[0009] Furthermore, the precise gas mixing module also includes a mass flow controller configured on the gas path of the test reaction gas inlet, the reaction gas mixing inlet and the capture gas mixing inlet, respectively, for realizing the flow regulation and ratio of reaction gas F1, reaction gas F2 and isotope capture gas F3.

[0010] Furthermore, the gas activation zone uses an empty tube or is loaded with an activation solid bed to obtain the gas-phase free radical intermediate to be investigated.

[0011] Furthermore, the free radical reaction zone is equipped with a replaceable catalytic reaction bed to replicate the industrial fixed-bed reaction conditions.

[0012] Furthermore, it also includes a main control module, which is electrically connected to the temperature control component, the precise gas distribution module and the mass spectrometry detection module, respectively, for realizing the coordinated control and acquisition analysis of temperature, gas path and detection data.

[0013] Secondly, a method for studying gas-solid heterogeneous catalytic reactions is provided, the method comprising the following steps: Pretreatment: The airtightness of the three independently temperature-controlled reaction chambers is tested. According to the catalytic reaction system to be tested, the initial temperatures of the gas activation zone, the free radical reaction zone and the low-temperature free radical capture zone are set respectively. The precise gas distribution module and the mass spectrometry detection module are adjusted to the working state. Blank control group test: No catalyst is loaded in the free radical reaction zone. Reactant gas F1 and reactant gas F2 are introduced at a preset flow rate and the set temperature is maintained. After the gas is exchanged with isotope capturing gas F3 in the low-temperature free radical capture zone, the tail gas components are detected by the mass spectrometry detection module, and the blank group data is recorded to eliminate interference from gas phase homogeneous reaction. Experimental group test: A catalytic reaction bed (the solid catalyst to be tested) was packed in the free radical reaction zone, and the industrial fixed bed operating parameters were replicated, maintaining the same gas path parameters and temperature parameters as the blank control group; Reaction gas F1 was introduced into the gas activation zone, and after being activated at high temperature into a gas-phase free radical intermediate product, it was mixed with the introduced reaction gas F2 and entered the catalytic reaction bed of the free radical reaction zone to undergo a gas-solid heterogeneous catalytic reaction; After the reaction, it entered the low-temperature free radical capture zone and underwent a low-temperature exchange reaction with the introduced isotope capture gas F3 to capture stable active intermediate products; Mechanism identification and data analysis: By comparing the tail gas components, product distribution, and isotope-labeled product content of the experimental group and the blank control group, the LH mechanism and ER mechanism of the catalytic reaction were identified. If both reactant gases F1 and F2 are adsorbed on the catalyst surface and then react, the product distribution conforms to the kinetic characteristics of the LH mechanism. If only a single gas is adsorbed on the catalyst surface and another gas in the gas phase reacts directly with the adsorbed reactants, the product distribution conforms to the kinetic characteristics of the ER mechanism.

[0014] Furthermore, the research method also includes a multi-dimensional kinetic characterization step: by independently conducting programmed temperature rise tests in the gas activation zone, the free radical reaction zone, and the low-temperature free radical capture zone, temperature-product response data of the gas activation process, surface reaction process, and free radical desorption process are collected respectively, and the reaction activation energy, free radical evolution law, and reaction rate control are analyzed.

[0015] Furthermore, the reaction gas F1 is a hydrocarbon or alkane gas that can be activated at high temperature to generate free radicals, the reaction gas F2 is an oxidizing gas, a reducing gas, or an inert doped gas, and the isotope capturing gas F3 is a stable isotope gas corresponding to the reaction gas. The isotope labeling enables precise traceability of reaction intermediates and final products, and distinguishes between gas-phase free radical reactions and catalyst surface reactions.

[0016] Furthermore, when studying the methane coupling radical catalytic reaction, the temperature of the gas activation zone is set to 800–1100 °C to activate methane molecules and generate methyl radicals; the temperature of the radical reaction zone is set to 400–700 °C to match the fixed-bed reaction conditions of methane coupling; and the temperature of the low-temperature radical capture zone is set to 0–50 °C, using 13CH4 as the isotope capture gas F3 to achieve low-temperature exchange capture and source detection of methyl radicals.

[0017] Compared with existing technologies, the beneficial effects of this invention are: 1. The research device for gas-solid heterogeneous catalytic reactions, through the above-mentioned module settings, can realize the stepwise decomposition of multi-gas heterogeneous catalytic reactions, precise capture of free radicals, direct identification of reaction mechanisms, and multi-dimensional kinetic characterization. It also considers both independent equipment application and modular integration. Each functional unit is independently detachable, and can be assembled separately as a dedicated free radical catalytic characterization device, or directly integrated into existing chemisorption analyzers and temperature-programmed reaction equipment, rapidly expanding the mechanism research functions of traditional equipment and enhancing the technical advantages and industrial added value of catalytic characterization equipment; 2. Precise decomposition of the reaction process and high accuracy in mechanism research: Through three independently temperature-controlled furnace sections, the three core processes of gas free radical activation, catalyst surface reaction, and low-temperature capture of free radicals are completely separated, thoroughly solving the problems of reaction process coupling and difficulty in capturing intermediate products in traditional equipment. It can accurately track the evolution of free radicals and mass transfer reactions. 3. Direct identification of LH and ER reaction mechanisms: Through dual-gas-path staged feeding, isotope low-temperature capture, and blank control experiments, the co-adsorption reaction of two reactants (LH mechanism) and the gas-phase-adsorption phase reaction (ER mechanism) can be directly distinguished, providing direct and reliable experimental evidence for the study of heterogeneous catalytic reaction mechanisms and breaking through the technical bottleneck of traditional indirect speculation; 4. Multi-dimensional kinetic characterization and comprehensive data: The three-section furnace can independently carry out isothermal reaction and programmed temperature rise tests, and can collect multi-dimensional parameters such as gas activation characteristics, surface reaction kinetics, free radical desorption, and thermal stability, comprehensively analyzing the rate control steps and micro-reaction pathways of catalytic reactions; 5. Strong anti-interference ability and good experimental repeatability: The low-temperature isotope capture technology stabilizes highly active free radical intermediates, inhibits secondary reactions of intermediates, and combines blank control to eliminate interference from gas-phase homogeneous reactions, significantly improving the accuracy and repeatability of experimental data. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a research apparatus for a gas-solid heterogeneous catalytic reaction according to the present invention; Figure 2 This is a schematic diagram of the tail gas spectral results of the H2 high-temperature FeAl catalytic activation of the present invention, which is adsorbed by calcium carbonate in the reaction zone and exchanged with D2 in the capture zone. In the figure: 1. Gas activation zone; 2. Free radical reaction zone; 3. Low temperature free radical capture zone; 4. Mass spectrometer; 5. Quartz tube; 6. Capture gas inlet; 7. Reaction gas inlet; 8. Analytical reaction gas inlet; 9. Tail gas outlet; 10. Capillary; 11. Activated solid bed; 12. Catalytic reaction bed. Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely 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.

[0020] Example 1: A research apparatus for gas-solid heterogeneous catalytic reactions, such as... Figure 1 As shown, it includes three independently temperature-controlled reaction chambers connected and interconnected, a precision gas distribution module, a low-temperature capture and exchange module, and a mass spectrometry detection module; The three-section independent temperature-controlled reaction furnace includes a gas activation zone 1, a free radical reaction zone 2, and a low-temperature free radical capture zone 3 arranged sequentially along the airflow direction, and each is equipped with an independent temperature control component; The precise gas distribution module includes a test reaction gas inlet 8, a reaction gas distribution inlet 7, and a capture gas distribution inlet 6. The test reaction gas inlet 8 is connected to the gas activation zone 1 and is used to activate the introduced reaction gas F1 at high temperature to generate gaseous free radical intermediates. The reaction gas distribution inlet 7 is connected between the gas activation zone and the free radical reaction zone through a quartz tube 5 (integrated reaction chamber) and is used to introduce reaction gas F2, so that the reaction gas F2 mixes with the activated gaseous free radical intermediates and enters the free radical reaction zone 2 together. The capture gas distribution inlet 6 is located between the free radical reaction zone 2 and the low-temperature free radical capture zone 3 and isotope capture gas F3 is introduced through the quartz tube 5. The low-temperature capture exchange module is located inside the low-temperature free radical capture zone 3. The low-temperature free radical capture zone 3 is used to provide a low-temperature environment. The low-temperature capture exchange module is used for the exchange reaction between the isotope capture gas F3 and the gaseous free radical intermediates (tail gas from the previous reaction) to capture stable active intermediates. The mass spectrometry detection module (e.g., a mass spectrometer 4) is connected to the exhaust gas outlet 9 of the low-temperature free radical capture zone 3 via a capillary tube 10. A trace gas flow F5 is extracted from the exhaust gas F4 for real-time detection of the components and content of the captured and exchanged exhaust gas.

[0021] This research apparatus for gas-solid heterogeneous catalytic reactions, through the aforementioned modular design, enables stepwise decomposition of multi-gas heterogeneous catalytic reactions, precise capture of free radicals, direct identification of reaction mechanisms, and multi-dimensional kinetic characterization. It also accommodates both independent equipment applications and modular integration. Each functional unit is independently detachable, allowing it to be assembled separately as a dedicated free radical catalytic characterization device or directly integrated into existing chemisorption analyzers and temperature-programmed reaction equipment. This rapidly expands the mechanistic research capabilities of traditional equipment, enhancing the technological advantages and industrial added value of catalytic characterization devices.

[0022] The three-section independent temperature-controlled reactor has three interconnected independent reactor areas, which can respectively realize high-temperature free radical activation, medium-temperature fixed-bed catalytic reaction, and low-temperature free radical stabilization and capture, completely dismantling the traditional coupled reaction process; the gas activation zone is used to activate the introduced reaction gas F1 at high temperature, and can optionally load an activation solid bed 11 to generate gas-phase free radical intermediates (intermediates); the free radical reaction zone 2 can be filled with the solid catalyst to be tested, completely simulating the catalyst bed structure, space velocity and operating conditions of the fixed-bed reactor, and is used to allow the activated reaction gas free radicals to undergo gas-solid heterogeneous catalytic reactions with the external gas; the low-temperature free radical capture zone 3 also serves as an isotope capture zone, which provides a low-temperature environment to exchange, capture and stabilize the active free radicals and intermediates in the reaction tail gas through isotope capture gas.

[0023] In terms of gas path design, this device features a reactive gas inlet (F2) between the activation and reaction zones to enable staged feeding of the two reactants, simulating a real multi-component catalytic reaction system. An isotope-capturing gas inlet (F3) is located between the reaction and capture zones. Through low-temperature isotope exchange technology, highly reactive free radical intermediates are stabilized, preventing secondary reactions from interfering with the detection results. A high-precision mass spectrometer is connected in series at the detection end to achieve real-time quantitative detection of exhaust gas components and isotope-labeled products.

[0024] Furthermore, the temperature control ranges of the gas activation zone 1, the free radical reaction zone 2, and the low-temperature free radical capture zone 3 are mutually adapted and differentiated. The temperature control range of the gas activation zone 1 is 300–1200°C, which meets the requirements for high-temperature activation of gas to produce free radicals. The temperature control range of the free radical reaction zone 2 is room temperature–800°C, which is suitable for fixed-bed catalytic reaction conditions. The temperature control range of the low-temperature free radical capture zone 3 is room temperature–600°C, which meets the requirements for low-temperature stable capture of free radicals and inhibits secondary reactions of intermediate products. For the heating process, the heating rate is 1–10°C / min, and the temperature control accuracy is ±0.5°C.

[0025] By setting the temperature control method described above, the gas activation zone can be heated separately to test the activation temperature threshold of gas free radicals; the free radical reaction zone can be heated separately to test the temperature characteristics of the catalytic reaction; and the low-temperature free radical capture zone can be heated separately to test the thermal stability of intermediate products.

[0026] Furthermore, the precise gas distribution module also includes a mass flow controller configured on the gas path of the test reaction gas inlet 8, the reaction gas distribution inlet 7, and the capture gas distribution inlet 6, respectively, for realizing the flow regulation and proportioning of reaction gas F1, reaction gas F2, and isotope capture gas F3.

[0027] Furthermore, the gas activation zone 1 uses an empty tube or is loaded with an activated solid bed 11 (active catalyst) to obtain the gas-phase free radical intermediate to be investigated.

[0028] Furthermore, the free radical reaction zone 2 is loaded with a replaceable catalytic reaction bed 12, which can be adapted to different forms of solid catalysts such as granular, powdered, and honeycomb. The bed height and packing density can be adjusted as needed to replicate the industrial fixed bed reaction conditions.

[0029] Furthermore, the device also includes a main control module, which is electrically connected to the temperature control component, the precise gas distribution module, and the mass spectrometry detection module, respectively, for the purpose of achieving coordinated control and acquisition analysis of temperature, gas path, and detection data.

[0030] Example 2: A method for studying gas-solid heterogeneous catalytic reactions is provided, the method comprising the following steps: Step 1, Pretreatment: The airtightness of the three independently temperature-controlled reaction furnaces is tested. According to the catalytic reaction system to be tested, the initial temperatures of the gas activation zone 1, the free radical reaction zone 2 and the low-temperature free radical capture zone 3 are set respectively. The precise gas distribution module and the mass spectrometry detection module are adjusted to the working state. Step 2, Blank control group test: No catalyst is loaded in the free radical reaction zone 2. Reactant gas F1 and reactant gas F2 are introduced at a preset flow rate and the set temperature is maintained. After the gas is exchanged with isotope capturing gas F3 in the low temperature free radical capture zone 3, the tail gas components are detected by the mass spectrometry detection module, and the blank group data is recorded to eliminate interference from gas phase homogeneous reaction. Step 3, Experimental Group Testing: A catalytic reaction bed (the solid catalyst to be tested) is loaded into the free radical reaction zone 2. The industrial fixed bed operating parameters are replicated, and the gas path parameters and temperature parameters are kept consistent with those of the blank control group. Reaction gas F1 is introduced into the gas activation zone, and after being activated at high temperature into a gas-phase free radical intermediate, it is mixed with the introduced reaction gas F2 and enters the catalytic reaction bed of the free radical reaction zone 2 to undergo a gas-solid heterogeneous catalytic reaction. After the reaction, it enters the low-temperature free radical capture zone 3 and undergoes a low-temperature exchange reaction with the introduced isotope capture gas F3 to capture stable active intermediates. Step 4, Mechanism Identification and Data Analysis: By comparing the tail gas components, product distribution, and isotope-labeled product content of the experimental group and the blank control group, the LH mechanism and ER mechanism of the catalytic reaction are identified; if both reactant gases F1 and F2 are adsorbed on the catalyst surface and then react, the product distribution conforms to the kinetic characteristics of the LH mechanism; if only a single gas is adsorbed on the catalyst surface, and another gas in the gas phase reacts directly with the adsorbed reactants, the product distribution conforms to the kinetic characteristics of the ER mechanism.

[0031] This research method for gas-solid heterogeneous catalytic reactions completely separates the three core processes—gas radical activation, catalyst surface reaction, and low-temperature radical capture—through a three-stage independently temperature-controlled furnace. This thoroughly solves the problems of process coupling and difficulty in capturing intermediate products in traditional equipment, and allows for precise tracking of radical evolution and mass transfer reaction processes. By comparing the blank group with the experimental group, interference from gas-phase homogeneous reactions is eliminated. Combined with isotope tracing technology, the LH co-adsorption reaction and the ER gas-phase-adsorption phase reaction mechanism can be directly distinguished.

[0032] Furthermore, the research method also includes step 5, multi-dimensional kinetic characterization: by controlling the gas activation zone 1, the free radical reaction zone 2 and the low-temperature free radical capture zone 3 to independently carry out programmed temperature rise tests, temperature-product response data of the gas activation process, surface reaction process and free radical desorption process are collected respectively, and the reaction activation energy, free radical evolution law and reaction rate control are analyzed.

[0033] By conducting independent temperature-programmed tests in three furnace sections, multi-dimensional kinetic parameters such as gas activation threshold, catalytic reaction activation energy, and free radical thermal stability were obtained, providing a comprehensive analysis of the microscopic mechanism of the catalytic reaction. The heating rates of the three furnace sections ranged from 1 to 10 °C / min, allowing for individual heating of the gas activation zone to test the gas free radical activation temperature threshold; individual heating of the free radical reaction zone to test the catalytic reaction temperature characteristics; and individual heating of the low-temperature free radical capture zone to test the thermal stability of intermediate products.

[0034] Furthermore, the reaction gas F1 is a hydrocarbon or alkane gas that can be activated at high temperatures to generate free radicals, including hydrogen, methane, ethane, and propane; the reaction gas F2 is an oxidizing gas, a reducing gas, or an inert doped gas, including carbon dioxide, oxygen, and H2O, etc. Therefore, the reactions that can be involved include dry reforming of alkanes, hydrogenation of carbon dioxide, coupling of alkanes, and oxidative dehydrogenation of alkanes.

[0035] The isotope capturing gas F3 is a stable isotope gas corresponding to the reactant gas, including D2, 13 CH4 18 O2, 13 Any type of CO2 can be used to accurately trace the intermediate and final products of the reaction through isotope labeling, distinguishing between gas-phase free radical reactions and catalyst surface reactions.

[0036] Furthermore, when studying the methane coupling radical catalytic reaction, the temperature of the gas activation zone is set to 800–1100 °C to activate methane molecules and generate methyl radicals; the temperature of the radical reaction zone is set to 400–700 °C to match the fixed-bed reaction conditions of methane coupling; and the temperature of the low-temperature radical capture zone is set to 0–50 °C, using 13CH4 as the isotope capture gas F3 to achieve low-temperature exchange capture and source detection of methyl radicals.

[0037] Example 3: This example uses the free radical mechanism of the co-thermal decomposition reaction between hydrogen and calcium carbonate as an example to further illustrate the research apparatus in Example 1 and the research method in Example 2.

[0038] In the research apparatus: the high-temperature activation section (gas activation zone 1) is filled with FeAl catalyst, the reaction section (free radical reaction zone 2) is equipped with a calcium carbonate powder bed, and the working conditions of the reaction between hydrogen and calcium carbonate are simulated. The capture section (low-temperature free radical capture zone 3) is left empty as a control group, and no calcium carbonate bed is loaded in the reaction section. Gas path: Reactant gas F1 is introduced into H2, no gas is introduced into the reaction mixture, and the gas for collection is introduced into D2; Temperature control: activation section is activated at a constant temperature of 700℃, reaction section is reacted at a constant temperature of 700℃, and collection section is captured at a constant temperature of 300℃. Detection: Mass spectrometry monitoring m / z=3 (HD).

[0039] Result: Combination Figure 2 As shown, in the control group, a significant HD signal was observed in the blank tube without calcium carbonate in the reaction section, indicating that the FeAl catalyst can catalyze the activation of H2 to generate H· free radicals at 700℃ and capture them. When a CaCO3 bed was set in the reaction section before the capture section, the HD signal disappeared, indicating that the activated H· free radicals reacted directly with calcium carbonate. This provides strong evidence for the free radical reaction pathway of the calcium carbonate hydrogenation decomposition reaction.

[0040] Example 4: This example uses the study of the catalytic reaction mechanism of alkyl coupling radicals as an example to further illustrate the research apparatus in Example 1 and the research method in Example 2.

[0041] (1) Device commissioning: Complete the airtightness test of the device, set the initial temperature of the three furnace sections: 950℃ for the gas activation zone, 550℃ for the free radical reaction zone, and 25℃ for the low-temperature free radical capture zone (low-temperature free radical capture zone 3); debug the mass spectrometry detection module to the high-precision detection state, and complete the calibration of the mass flow controllers of each gas path.

[0042] (2) Blank control group test: No catalyst was loaded in the free radical reaction zone 2. High-purity methane (reaction gas) was introduced at a flow rate of 50 mL / min. After the gas path stabilized, the test was continued for 30 min. The mass spectrometer detected the tail gas components in real time and recorded the blank group data to confirm that no gas-phase homogeneous coupling reaction occurred under this temperature condition.

[0043] (3) Experimental group test: Commercial molybdenum-based catalyst for methane coupling was loaded into the free radical reaction zone 2, and the bed height and packing density were adjusted to replicate the industrial fixed bed reaction conditions; the flow rate of the reaction gas (methane) was kept at 50 mL / min, and it was activated into methyl free radicals in the gas activation zone 1 at 950℃; a small amount of oxygen (reaction gas) was introduced between the first and second furnace sections at a flow rate of 5 mL / min, and after mixing, it entered the catalyst bed to undergo catalytic coupling reaction; the gas after reaction in the free radical reaction zone 2 entered the low temperature free radical capture zone 3, and was introduced into the catalyst bed. 13 CH4 isotope methane was used as the capturing gas at a flow rate of 20 mL / min, and the methyl radical exchange capture was completed at a low temperature of 25 °C, stabilizing the intermediate product.

[0044] (4) Mechanism identification: Mass spectrometry detection revealed that the experimental group detected a large amount of 13 The C2 coupling product labeled with C, combined with the control result of the blank group without coupling product, can determine that the reaction has two pathways: the co-adsorption reaction of methane on the catalyst surface (LH mechanism) and the reaction of gas-phase methyl radicals with surface-adsorbed methane (ER mechanism), thus achieving a precise distinction between the two mechanisms.

[0045] (5) Temperature program characterization: The three furnace sections were independently temperature-programmed at a rate of 5℃ / min. The methane activation temperature threshold was found to be 820℃, the optimal temperature range for the methane coupling reaction was 520~580℃, and the low-temperature stability range for methyl radicals was ≤40℃, thus accurately obtaining the key parameters of the reaction kinetics.

[0046] 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 research apparatus for gas-solid heterogeneous catalytic reactions, characterized in that, It includes three independently temperature-controlled reaction chambers that are connected and interconnected, a precise gas distribution module, a low-temperature capture and exchange module, and a mass spectrometry detection module; The three-section independently temperature-controlled reaction furnace includes a gas activation zone, a free radical reaction zone, and a low-temperature free radical capture zone arranged sequentially along the airflow direction, and each is equipped with an independent temperature control component; The precise gas mixing module includes a test reaction gas inlet, a reaction gas mixing inlet, and a capture gas mixing inlet. The test reaction gas inlet is connected to the gas activation zone and is used to activate the introduced reaction gas F1 at high temperature to generate a gaseous free radical intermediate. The reaction gas mixing inlet is connected between the gas activation zone and the free radical reaction zone and is used to introduce reaction gas F2, so that reaction gas F2 mixes with the activated gaseous free radical intermediate and enters the free radical reaction zone together. The capture gas mixing inlet is located between the free radical reaction zone and the low-temperature free radical capture zone and is used to introduce isotope capture gas F3. The low-temperature capture and exchange module is disposed inside the low-temperature free radical capture region. The low-temperature free radical capture region is used to provide a low-temperature environment. The low-temperature capture and exchange module is used for the exchange reaction between the isotope capture gas F3 and the gaseous free radical intermediate after the reaction, thereby capturing stable and active intermediates. The mass spectrometry detection module is connected to the exhaust gas outlet of the low-temperature free radical capture zone, and extracts a trace gas flow F5 from the exhaust gas F4 for real-time detection of the components and content of the captured and exchanged exhaust gas.

2. The research apparatus for gas-solid heterogeneous catalytic reactions according to claim 1, characterized in that, The temperature control ranges of the gas activation zone, the free radical reaction zone, and the low-temperature free radical capture zone are mutually compatible and differentiated. The temperature control range of the gas activation zone is 300–1200°C to meet the requirements of high-temperature gas activation for free radical production. The temperature control range of the free radical reaction zone is room temperature–800°C to adapt to fixed-bed catalytic reaction conditions. The temperature control range of the low-temperature free radical capture zone is room temperature–600°C to meet the requirements of low-temperature stable capture of free radicals and suppress secondary reactions of intermediate products. For the heating process, the heating rate is 1–10°C / min, and the temperature control accuracy is ±0.5°C.

3. The research apparatus for gas-solid heterogeneous catalytic reactions according to claim 1, characterized in that, The precise gas mixing module also includes a mass flow controller configured on the gas path of the test reaction gas inlet, the reaction gas mixing inlet and the capture gas mixing inlet, respectively, for realizing the flow regulation and ratio of reaction gas F1, reaction gas F2 and isotope capture gas F3.

4. The research apparatus for gas-solid heterogeneous catalytic reactions according to claim 1, characterized in that, The gas activation zone uses an empty tube or is loaded with an activation solid bed to obtain the gas-phase free radical intermediate to be investigated.

5. The research apparatus for gas-solid heterogeneous catalytic reactions according to claim 1, characterized in that, The free radical reaction zone is equipped with a replaceable catalytic reaction bed, replicating the industrial fixed-bed reaction conditions.

6. The research apparatus for gas-solid heterogeneous catalytic reactions according to claim 1, characterized in that, It also includes a main control module, which is electrically connected to the temperature control component, the precise gas distribution module and the mass spectrometry detection module, respectively, for the purpose of achieving coordinated control and acquisition analysis of temperature, gas path and detection data.

7. A method for studying gas-solid heterogeneous catalytic reactions, implemented based on the research apparatus for gas-solid heterogeneous catalytic reactions as described in any one of claims 1 to 6, characterized in that, The research method includes the following steps: The airtightness of the three independently temperature-controlled reaction chambers was tested. The initial temperatures of the gas activation zone, the free radical reaction zone, and the low-temperature free radical capture zone were set according to the catalytic reaction system to be tested. The precise gas distribution module and the mass spectrometry detection module were adjusted to the working state. Blank control group test: No catalyst is loaded in the free radical reaction zone. Reactant gas F1 and reactant gas F2 are introduced at a preset flow rate and the set temperature is maintained. After the gas is exchanged with isotope capturing gas F3 in the low-temperature free radical capture zone, the tail gas components are detected by the mass spectrometry detection module, and the blank group data is recorded to eliminate interference from gas phase homogeneous reaction. Experimental group test: A catalytic reaction bed (the solid catalyst to be tested) was packed in the free radical reaction zone, and the industrial fixed bed operating parameters were replicated, maintaining the same gas path parameters and temperature parameters as the blank control group; Reaction gas F1 was introduced into the gas activation zone, and after being activated at high temperature into a gas-phase free radical intermediate product, it was mixed with the introduced reaction gas F2 and entered the catalytic reaction bed of the free radical reaction zone to undergo a gas-solid heterogeneous catalytic reaction; After the reaction, it entered the low-temperature free radical capture zone and underwent a low-temperature exchange reaction with the introduced isotope capture gas F3 to capture stable active intermediate products; By comparing the exhaust gas composition, product distribution, and isotope-labeled product content of the experimental group and the blank control group, the LH mechanism and ER mechanism of the catalytic reaction were identified. If both reactant gases F1 and F2 are adsorbed on the catalyst surface and then react, the product distribution conforms to the kinetic characteristics of the LH mechanism. If only a single gas is adsorbed on the catalyst surface and another gas in the gas phase reacts directly with the adsorbed reactants, the product distribution conforms to the kinetic characteristics of the ER mechanism.

8. The method for studying gas-solid heterogeneous catalytic reactions according to claim 7, characterized in that, The research method also includes a multi-dimensional kinetic characterization step: by independently conducting programmed temperature rise tests in the gas activation zone, the free radical reaction zone, and the low-temperature free radical capture zone, temperature-product response data of the gas activation process, surface reaction process, and free radical desorption process are collected respectively, and the reaction activation energy, free radical evolution law, and reaction rate control are analyzed.

9. The method for studying gas-solid heterogeneous catalytic reactions according to claim 7, characterized in that, The reaction gas F1 is a hydrocarbon or alkane gas that can be activated at high temperature to generate free radicals. The reaction gas F2 is an oxidizing gas, a reducing gas, or an inert doped gas. The isotope capturing gas F3 is a stable isotope gas corresponding to the reaction gas. The isotope labeling enables precise traceability of reaction intermediates and final products, and distinguishes between gas-phase free radical reactions and catalyst surface reactions.

10. The method for studying gas-solid heterogeneous catalytic reactions according to claim 7, characterized in that, When studying the methane coupling radical catalytic reaction, the temperature of the gas activation zone was set to 800–1100℃ to activate methane molecules and generate methyl radicals; the temperature of the radical reaction zone was set to 400–700℃ to match the fixed-bed reaction conditions of methane coupling; and the temperature of the low-temperature radical capture zone was set to 0–50℃. 13 CH4 is used as the isotope-capturing gas F3 to achieve low-temperature exchange capture and source detection of methyl radicals.

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