A device and method for in-situ gas-phase radical trapping and on-line detection

Abstract

This invention discloses an in-situ capture and online detection device and method for gas-phase free radicals. The device includes a high-temperature reaction section and a medium-low temperature capture section. The high-temperature reaction section is provided with a reaction gas inlet for introducing the reaction gas stream to be detected. A reaction quartz pipe and a capture gas inlet are connected between the high-temperature reaction section and the medium-low temperature capture section for introducing the capture gas stream. A tail gas outlet is provided downstream of the medium-low temperature capture section. The tail gas outlet is connected to an online mass spectrometry detection unit through a capillary branch to extract a trace amount of gas stream from the tail gas and introduce it into the online mass spectrometry detection unit for detection and analysis. The device of this invention is simple, low-cost, in-situ online, and highly versatile. It can effectively distinguish between surface species and gas-phase free radicals and is suitable for mechanism studies in heterogeneous catalysis, surface reactions, energy conversion, and other fields. It solves the technical problems of traditional methods being complex, expensive, and unable to screen free radicals in situ.

Description

Technical Field

[0001] This invention relates to the fields of catalytic characterization technology, gas phase intermediate detection, and isotope tracer analysis technology. Specifically, it relates to a device and method for in-situ capture and online detection of gas phase free radicals, and in particular, a simple detection device and method using dual-stage independent temperature control, stepwise activation-isotope capture, and online mass spectrometry. It is suitable for in-situ capture, qualitative and quantitative detection, and sieving of gas phase free radical intermediates in heterogeneous catalysis, surface reactions, energy conversion, and environmental catalysis. Background Technology

[0002] Gas-phase free radicals (such as H·, O·, OH·, CH3· and RO·) are key active intermediates in heterogeneous catalysis, high-temperature reactions, combustion, and atmospheric chemistry. Their direct, in-situ, and reliable detection is of great significance for revealing reaction pathways, determining rate-determining steps, and optimizing catalyst design.

[0003] The existing technology has the following obvious drawbacks: (1) The detection equipment is expensive and complex, such as electron spin resonance (ESR), laser-induced fluorescence (LIF), photoionization mass spectrometry, etc., which are difficult to popularize; (2) Most of them are offline or indirect detection, and cannot distinguish between surface adsorbed species and real gas phase free radicals; (3) Single-temperature isotope exchange is easily affected by temperature, making it impossible to achieve stable capture of free radicals; (4) With a fixed temperature, selective sieving based on differences in free radical activation energies is not possible; (5) The gas path design is simple and cannot realize the step-by-step control of "generating first and then capturing", and the signal is easily distorted.

[0004] Therefore, developing a device and method that is simple in structure, low in cost, in-situ online, programmable temperature-controlled sieving, and capable of distinguishing gaseous free radicals is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a device and method for in-situ capture and online detection of gas-phase free radicals.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A gas-phase free radical in-situ capture and online detection device includes a dual-stage independently temperature-controlled tubular furnace. The dual-stage independently temperature-controlled tubular furnace has a high-temperature reaction section and a medium-low temperature capture section arranged sequentially. The upstream of the high-temperature reaction section is provided with a reaction gas inlet for introducing the reaction gas stream to be detected. A reaction quartz tube connects and communicates between the high-temperature reaction section and the medium-low temperature capture section. The reaction quartz tube is provided with a capture gas inlet for introducing the capture gas stream. The downstream of the medium-low temperature capture section is provided with a tail gas outlet. The tail gas outlet is connected to an online mass spectrometry detection unit through a capillary branch to extract a trace amount of gas stream from the tail gas and introduce it into the online mass spectrometry detection unit for detection and analysis.

[0007] Furthermore, the high-temperature reaction section and the medium-low temperature collection section are each equipped with a temperature control module. The temperature control range of the high-temperature reaction section is room temperature to 1000℃, the heating rate is 1 to 10℃ / min, and the temperature control accuracy is ±0.5℃. The temperature control range of the medium-low temperature collection section is room temperature to 600℃, the heating rate is 1 to 10℃ / min, and the temperature control accuracy is ±0.5℃.

[0008] Furthermore, the pipelines containing the reaction gas inlet and the capture gas inlet are independently controlled, and the gas flow is introduced in stages to achieve a stepwise reaction mode in which free radicals are first generated and then captured.

[0009] Furthermore, the high-temperature reaction section is loaded with a bed of gaseous molecule activators.

[0010] Furthermore, the low-temperature trapping section is the site for isotope capture and exchange. A catalyst bed is added as needed. The temperature control premise of the low-temperature trapping section is that only the reaction between active free radicals and isotope molecules occurs, and no direct exchange reaction between gas molecules and isotope molecules occurs.

[0011] Further, the reaction gas stream is at least one of H2, O2, N2, CH2, CO, CO2, NH3, and H2O.

[0012] Furthermore, the captured airflow is D2, H2, 18 O2, 13 CO 13 CH4 and H2 18 At least one of O.

[0013] Furthermore, this device can be applied to one scenario in heterogeneous catalysis mechanism research, catalyst activity evaluation, surface intermediate detection, and radical-solid interaction characterization.

[0014] A method for in-situ capture and online detection of gas-phase free radicals, using the gas-phase free radical in-situ capture and online detection device as described above, includes the following steps: The reaction gas to be tested is introduced into the high-temperature reaction section, and the reaction gas is activated into a gas-phase free radical intermediate under the action of a catalyst; Isotope gas is introduced into the medium-low temperature collection section, and the isotope gas undergoes isotope exchange or addition reaction with the gas phase free radical intermediate to obtain reaction products. The reaction products enter the online mass spectrometry detection unit through a capillary branch to detect the exchanged characteristic isotope products in real time. By adjusting the temperature of the high-temperature reaction section by raising the temperature, the generation temperature range of different gas-phase free radical intermediates was investigated based on the difference in the activation energy of gas molecule dissociation. By adjusting the temperature of the medium-low temperature collection section, the reactivity of different gas phase free radical intermediates is screened based on the differences in the reactivity of gas molecule free radicals.

[0015] Furthermore, through comparative experiments with blank control, presence or absence of catalyst, presence or absence of isotope gas, and presence or absence of solid adsorption bed, the true gas-phase free radical signal was confirmed.

[0016] Furthermore, this method also includes applications in the in-situ detection, qualitative and quantitative analysis, and sieving of gaseous free radicals such as H·, O·, OH·, CH3·, and RO·.

[0017] Compared with existing technologies, the beneficial effects of this invention are: 1. This in-situ capture and online detection device for gaseous free radicals adopts a dual-stage independent programmable temperature-controlled furnace, divided into a high-temperature reaction section and a medium-low temperature capture section, combined with two independent gas paths and online mass spectrometry, to achieve stepwise generation, stable capture, and real-time detection of gaseous free radicals; 2. This device has a simple structure, low cost, in-situ online operation, and strong versatility. It can effectively distinguish between surface species and gaseous free radicals, and is suitable for mechanism research in fields such as heterogeneous catalysis, surface reactions, and energy conversion, solving the technical problems of traditional methods being complex, expensive, and unable to screen free radicals in situ; 3. Through programmable temperature-controlled screening, different free radicals can be "screened" according to their activation order; 4. The device has strong versatility and is suitable for various gases and catalytic systems. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of an in-situ capture and online detection device for gas-phase free radicals according to the present invention; Figure 2 The tail gas spectroscopy results are obtained by introducing D2 to capture gas after high-temperature H2 activation (empty tube compared with FeAl catalyst) according to the present invention. Figure 3The tail gas spectroscopy results of the gas captured by D2 after H2 temperature program activation (empty tube comparison FeAl catalyst) in this invention; Figure 4 The tail gas spectroscopy results of CH4 high-temperature activation (empty tube comparison Ni@SBA-15 catalyst) and D2 capture gas were introduced in this invention. In the diagram: 1. High-temperature reaction section; 2. Medium- and low-temperature collection section; 3. Online mass spectrometry detection unit; 4. Reaction quartz tube; 5. Capture gas inlet; 6. Reaction gas inlet; 7. Capillary branch; 8. Gas molecule activator bed; 9. Catalyst bed; 10. Tail gas emission port. 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 device for in-situ capture and online detection of gas-phase free radicals, such as... Figure 1 As shown, the furnace includes a dual-stage independently temperature-controlled tubular furnace, which has a high-temperature reaction section 1 and a medium-low temperature trapping section 2 arranged sequentially. A reaction gas inlet 6 is located upstream of the high-temperature reaction section 1, used to introduce the reaction gas stream to be detected. A reaction quartz tube 4 connects and links the high-temperature reaction section 1 and the medium-low temperature trapping section 2. The reaction quartz tube 4 has a trapping gas inlet 5, used to introduce the trapping gas stream. A tail gas outlet 10 is located downstream of the medium-low temperature trapping section 2. The tail gas outlet 10 is connected to an online mass spectrometry detection unit 3 via a capillary branch 7, from which a trace amount of gas stream is extracted and introduced into the online mass spectrometry detection unit 3 for detection and analysis, with real-time monitoring of the m / z signal.

[0021] This in-situ capture and online detection device for gaseous free radicals adopts a dual-stage independent programmable temperature-controlled furnace, which is divided into a high-temperature reaction section 1 and a medium-low temperature capture section 2. Combined with two independent gas paths and online mass spectrometry, it realizes the stepwise generation, stable capture and real-time detection of gaseous free radicals.

[0022] This device features a simple structure, low cost, in-situ online operation, and strong versatility. It can effectively distinguish between surface species and gas-phase free radicals, making it suitable for mechanism studies in heterogeneous catalysis, surface reactions, and energy conversion. It solves the technical challenges of traditional methods being complex, expensive, and unable to screen free radicals in situ. This device can be designed and manufactured as a standalone gas-phase free radical detection system, or it can be integrated as a functional module into existing chemisorption analyzers to enhance instrument functionality, add value, and increase market competitiveness, demonstrating excellent industrial prospects.

[0023] The reaction gas inlet 6 and the capture gas inlet 5 can form two independent gas inlet systems, which are used to introduce the reaction gas flow and the capture gas flow, respectively, which are the molecular gas to be activated and the isotope capture gas. The molecular gas is dissociated into gaseous free radicals by the catalyst in the high-temperature reaction section. The free radicals enter the medium-low temperature capture section and react efficiently with the isotope capture gas. The products are directly introduced into the online mass spectrometry detection unit for detection and analysis, and qualitative and quantitative analysis is performed through characteristic isotope products.

[0024] Furthermore, the high-temperature reaction section 1 and the medium-low temperature collection section 2 are each equipped with a temperature control module. The temperature control range of the high-temperature reaction section is room temperature to 1000℃, the heating rate is 1 to 10℃ / min, and the temperature control accuracy is ±0.5℃. The temperature control range of the medium-low temperature collection section is room temperature to 600℃, the heating rate is 1 to 10℃ / min, and the temperature control accuracy is ±0.5℃. The temperature control module supports constant temperature, programmed temperature rise, stepped temperature rise, and segmented holding modes.

[0025] Furthermore, the pipelines containing the reactant gas inlet 6 and the capture gas inlet 5 are independently controlled, with gas flows introduced in stages to achieve a stepwise reaction mode in which free radicals are first generated and then captured. Gas flow control and mixing units are installed on their respective pipelines to control the flow rate, mixing ratio, and introduction sequence.

[0026] Furthermore, the high-temperature reaction section is equipped with a gaseous molecular activator bed 8, which achieves molecular activation by loading a catalyst. It is suitable for various catalyst forms such as powder, granules, and sheets. In some embodiments, the bed may not be loaded.

[0027] Furthermore, the low-temperature trapping section 2 is a site for isotope capture and exchange. A catalyst bed 9 is added as needed. The temperature control premise of the low-temperature trapping section 2 is that only the reaction between active free radicals and isotope molecules occurs, and no direct exchange reaction between gas molecules and isotope molecules occurs. This upper limit of the critical temperature can be determined through blank experiments.

[0028] Further, the reaction gas stream is at least one of H2, O2, N2, CH2, CO, CO2, NH3, and H2O.

[0029] Furthermore, the captured airflow is D2, H2, 18 O2, 13 CO 13 CH4 and H2 18 At least one of O.

[0030] Furthermore, this device can be applied to one scenario in heterogeneous catalysis mechanism research, catalyst activity evaluation, surface intermediate detection, and radical-solid interaction characterization.

[0031] Furthermore, through comparative experiments with blank control, presence or absence of catalyst, presence or absence of isotope gas, and presence or absence of solid adsorption bed, the true gas-phase free radical signal was confirmed.

[0032] Example 2: A method for in-situ capture and online detection of gas-phase free radicals is provided, using the in-situ capture and online detection device for gas-phase free radicals as described in Example 1.

[0033] The method includes the following steps: S1. The reaction gas to be tested is introduced into the high-temperature reaction section 1, and the reaction gas is activated into a gas-phase free radical intermediate under the action of a catalyst; S2. Isotope gas is introduced into the medium-low temperature collection section 2. The isotope gas undergoes isotope exchange or addition reaction with the gas phase free radical intermediate to obtain reaction products. S3. The reaction products enter the online mass spectrometry detection unit 3 through the capillary branch 7 to detect the exchanged characteristic isotope products in real time. S4. By adjusting the temperature of the high-temperature reaction section by raising the temperature, the generation temperature range of different gas-phase free radical intermediates is investigated based on the difference in the activation energy of gas molecule dissociation. S5. By adjusting the temperature of the medium-low temperature collection section, the reactivity of different gas phase free radical intermediates is screened according to the differences in the reactivity of gas molecule free radicals.

[0034] This method, through steps such as activation, capture, detection, and sieving, can activate molecular gases into free radicals at high temperatures, react with isotopic gases at medium and low temperatures, and perform qualitative and quantitative analysis by mass spectrometry; and can also achieve the sieving of different free radical intermediates through programmed temperature rise.

[0035] Furthermore, through comparative experiments with blank control, presence or absence of catalyst, presence or absence of isotope gas, and presence or absence of solid adsorption bed, the true gas-phase free radical signal was confirmed.

[0036] Furthermore, this method also includes applications in the in-situ detection, qualitative and quantitative analysis, and sieving of gaseous free radicals such as H·, O·, OH·, CH3·, and RO·.

[0037] Example 3: The apparatus in Example 1 and the method in Example 2 are further described using H· radical in situ capture and detection (H2 activation) as an example.

[0038] For the apparatus: FeAl catalyst is loaded into the high-temperature reaction section, and the collection section is left empty as a control group, in which no solid bed is loaded in the high-temperature section; For the gas path: the H2 reaction gas flow is introduced into the reaction gas inlet, and the D2 capture gas flow is introduced into the capture gas inlet; For temperature control: the high-temperature section is activated at a constant temperature of 700℃, and the collection section is captured at a constant temperature of 300℃; For detection: mass spectrometry monitoring m / z=3 (HD); Result: Combination Figure 2 As shown, the blank tube showed no HD signal, while the FeAl system exhibited significant HD, proving that the FeAl catalyst can catalyze the activation of H2 to H· radicals at 700 degrees Celsius, which are then captured. Figure 3 As shown, the high-temperature section implements temperature control from room temperature to 100°C, and characteristic product peaks appear in different temperature ranges.

[0039] Example 4: The apparatus in Example 1 and the method in Example 2 are further described using CH4 activated free radical in situ capture and detection as an example.

[0040] For the apparatus: Ni@SBA-15 catalyst is loaded into the high-temperature reaction section, and the trapping section is left empty as a control group, in which no solid bed is loaded in the high-temperature section; For the gas path: the CH4 reaction gas flow is introduced into the reaction gas inlet, and the D2 capture gas flow is introduced into the capture gas inlet; For temperature control: the high-temperature section is activated at a constant temperature of 700℃, and the collection section is captured at a constant temperature of 300℃; For detection: mass spectrometry monitoring m / z = 2 (H2) / 3 (HD), m / z = 16 (CH4) / 17 (CH3D) / 18 (CH2D2) / 19 (CHD3) / 20 (CD4); Result: Combination Figure 4 As shown, the blank control group only showed CH4 and its fragment peak signals (m / z = 1 / 2 / 14 / 15 / 16), but no signals of the isotope exchange products listed above, indicating that the methane molecules were not activated in the high-temperature blank tube; the system through the Ni catalyst bed showed three significant additional signals with m / z = 2 / 3 / 18, proving that the catalyst can catalytically activate CH4 to generate and capture H· radicals and CH2·methylene radicals at 700℃.

[0041] Example 5: The apparatus in Example 1 and the method in Example 2 are further described using the high-temperature programmed temperature rise activation of CH4 to generate different free radical intermediates as an example.

[0042] For the apparatus: Ni@SBA-15 catalyst is loaded into the high-temperature reaction section; For the gas path: the CH4 reaction gas flow is introduced into the reaction gas inlet, and the D2 capture gas flow is introduced into the capture gas inlet; For temperature control: the high-temperature reaction section is programmed to heat up from 200℃ to 800℃ at a rate of 10℃ / min; the collection section is kept at a constant temperature of 300℃. For detection: real-time monitoring of signals such as HD, CH3D, CH2D, and CHD2; Results: Characteristic product peaks appeared in different temperature ranges, enabling stepwise sieving of the activation difficulty of free radicals such as H· (420-800 ℃), CH3· (460 ℃), CH2· (550 ℃), and CH· (670 ℃).

[0043] Example 6: The apparatus in Example 1 and the method in Example 2 are further described using the example of the programmed temperature rise activation of CH4 in the medium-low temperature trapping section to generate different free radical intermediates.

[0044] For the apparatus: Ni@SBA-15 catalyst is loaded into the high-temperature reaction section; For the gas path: the CH4 reaction gas flow is introduced into the reaction gas inlet, and the D2 capture gas flow is introduced into the capture gas inlet; For temperature control: the high-temperature reaction section is kept at a constant temperature of 700℃; the collection section is programmed to increase the temperature from 100℃ to 600℃ at a rate of 10℃ / min. For detection: real-time monitoring of signals such as HD, CH3D, CH2D, and CHD2; Results: Characteristic product peaks appeared in different temperature ranges, enabling stepwise sieving of the reactivity of free radical intermediates such as H· (130 ℃), CH3· (570 ℃), CH2· (300 ℃), and CH· (170 ℃).

[0045] 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 device for in-situ gas-phase radical trapping and on-line detection, characterized in that, The furnace includes a dual-stage independently temperature-controlled tubular furnace, which has a high-temperature reaction section and a medium-low temperature trapping section arranged sequentially. The upstream of the high-temperature reaction section is a reaction gas inlet for introducing the reaction gas stream to be detected. A reaction quartz tube connects and links the high-temperature reaction section and the medium-low temperature trapping section, and the reaction quartz tube has a trapping gas inlet for introducing the trapping gas stream. Downstream of the medium-low temperature trapping section is a tail gas outlet, which is connected to an online mass spectrometry detection unit via a capillary branch. A trace amount of gas stream is extracted from the tail gas and introduced into the online mass spectrometry detection unit for detection and analysis.

2. The apparatus according to claim 1, wherein, The high-temperature reaction section and the medium-low temperature collection section are each equipped with a temperature control module. The temperature control range of the high-temperature reaction section is room temperature to 1000℃, the heating rate is 1 to 10℃ / min, and the temperature control accuracy is ±0.5℃. The temperature control range of the medium-low temperature collection section is room temperature to 600℃, the heating rate is 1 to 10℃ / min, and the temperature control accuracy is ±0.5℃.

3. The apparatus according to claim 1, wherein, The pipelines containing the reaction gas inlet and the capture gas inlet are controlled independently, and the gas flow is introduced in stages to achieve a stepwise reaction mode in which free radicals are first generated and then captured.

4. The apparatus of claim 1, wherein, The high-temperature reaction section is loaded with a bed of gaseous molecule activators.

5. The apparatus of claim 1, wherein, The low-temperature trapping section is the site for isotope capture and exchange. A catalyst bed is added as needed. The temperature control premise of the low-temperature trapping section is that only the reaction between active free radicals and isotope molecules occurs, and no direct exchange reaction between gas molecules and isotope molecules occurs.

6. The apparatus of claim 1, wherein, The reaction gas stream is at least one of H2, O2, N2, CH2, CO, CO2, NH3, and H2O.

7. The apparatus of claim 1, wherein, at least one of D2, H2, 18 O2, 13 CO, 13 CH4and H2 18 O 8. The apparatus of claim 1, wherein, It is applied in one scenario: heterogeneous catalysis mechanism research, catalyst activity evaluation, surface intermediate detection, and radical-solid interaction characterization.

9. A method for in-situ capturing and on-line detecting of gas phase radicals, using the in-situ capturing and on-line detecting apparatus for gas phase radicals according to any one of claims 1 to 8, characterized in that, Includes the following steps: The reaction gas to be tested is introduced into the high-temperature reaction section, and the reaction gas is activated into a gas-phase free radical intermediate under the action of a catalyst; Isotope gas is introduced into the medium-low temperature collection section, and the isotope gas undergoes isotope exchange or addition reaction with the gas phase free radical intermediate to obtain reaction products. The reaction products enter the online mass spectrometry detection unit through a capillary branch to detect the exchanged characteristic isotope products in real time. By adjusting the temperature of the high-temperature reaction section by raising the temperature, the generation temperature range of different gas-phase free radical intermediates was investigated based on the difference in the activation energy of gas molecule dissociation. By adjusting the temperature of the medium-low temperature collection section, the reactivity of different gas phase free radical intermediates is screened based on the differences in the reactivity of gas molecule free radicals.

10. The method of gas-phase in-situ trapping and on-line detection of radicals according to claim 9, wherein, The method confirms the true gas-phase free radical signal through comparative experiments with blank control, with and without catalyst, with and without isotopic gas, and with and without solid adsorption bed; the method also includes applications in in-situ detection, qualitative and quantitative analysis and sieving of gas-phase free radicals such as H·, O·, OH·, CH3· and RO·.

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