In-situ online detection method for hydroxyl radicals in hydrocarbon-water system high-temperature action process

Abstract

The invention belongs to the technical field of free radical detection, and provides an in-situ online detection method for hydroxyl free radicals in a hydrocarbon-water system high-temperature action process. The method comprises the following steps: preparing a capillary reaction kettle, preparing a capillary injector, preparing a test solution, and injecting a sample: sequentially injecting an aqueous solution and a hydrocarbon mixed solution containing a paramagnetic trapping agent into the capillary reaction kettle, so that the hydrocarbon mixed solution is discontinuous in short-column-shaped sections in the aqueous solution, a'hydrocarbon-water-hydrocarbon-water-hydrocarbon-water... 'multi-hydrocarbon-water 'interface is completed; sample detection and image analysis. According to the invention, hydrocarbons and a water solution to be detected are sealed by using a fused quartz capillary tube and a high-pressure valve, and multiple sections of hydrocarbon-water interfaces are sealed in a quartz capillary tube system, so that the oil-water interfaces of the hydrocarbon-water system in the capillary tube are densely arranged near detection points; the distribution density of oil and water droplets near an interface under a high-temperature condition and the generation of a large amount of free radicals are increased, and the signal-to-noise ratio of effective signals is improved.

Description

Technical Field

[0001] The invention relates to the technical field of free radical detection, and in particular to an in-situ online detection method for hydroxyl free radicals in a high-temperature process of a hydrocarbon-water system. Background Art

[0002] In the process of organic-inorganic interaction of hydrocarbon-water system, the addition of alkane free radicals or hydroxyl free radicals may reduce the chemical reaction threshold and promote the material exchange between alkane and aqueous solution under the catalytic conditions of initiator-free. At present, in the process of studying the organic-inorganic interaction between crude oil and water in oil and gas reservoirs, researchers rarely involve in-depth dissection of free radical reaction processes because it is difficult to directly identify short-lived free radicals under high temperature and high pressure conditions. Instead, they deduce the free radical reactions that may be involved in the reaction process based on the characterization and analysis of the products before and after the reaction, and then determine the mechanism of the chemical reaction. In this type of method, due to the lack of direct detection of free radicals (especially water-derived hydroxyl radicals) that are extremely critical in the reaction process, the reaction mechanism obtained is usually lacking in evidence. In recent years, researchers have proposed that the generation of water droplets at room temperature and pressure can promote H + and OH - It is noted that microdroplets can also be generated near the oil-water contact interface in a high-temperature environment. Whether these high-temperature microdroplets can generate free radicals and promote organic-inorganic interactions has not been studied yet. Therefore, it is necessary to accurately detect whether free radicals are generated at the oil-water interface microdroplets under high-temperature conditions in order to gain a deeper understanding of the role of free radicals in organic-inorganic interactions.

[0003] Electron paramagnetic resonance spectrometer (EPR) is widely used in the detection of various free radicals. However, since more than 99.9% of free radicals react rapidly during the reaction and are converted into more stable non-free radical substances, the free radical information in the product cannot be correctly described by non-in-situ detection methods. In-situ online detection methods must be used to characterize the free radicals involved in the reaction. The technical difficulty of high-temperature in-situ detection of free radicals is that the detection point of the electron paramagnetic resonance spectrometer is fixed and the detection range is small. Due to thermal expansion or pressure changes during the oil-water reaction, the interface in the capillary filled with the oil and water mixture often cannot be fixed near the detection point, and no free radical signal can be obtained. In addition, the trace free radicals generated by the single oil-water interface cannot be effectively captured by the capture agent.

[0004] Therefore, it is necessary to use sealed heating methods for electron paramagnetic resonance spectrometers to seal multiple sections of hydrocarbons and aqueous solutions in capillaries to create a "hydrocarbon-water-hydrocarbon-water-hydrocarbon-water..." multiple "hydrocarbon-water" interface system, so that in a high-temperature environment there are still multiple sections of hydrocarbon-water solutions located near the detection point, which can not only promote the generation of droplets, but also enable the generated free radicals to be quickly captured by the capture agent, so as to realize the high-temperature in-situ online detection function of free radicals in the "hydrocarbon-water" system. Summary of the invention

[0005] The purpose of the present invention is to provide an in-situ online detection method for hydroxyl radicals in a hydrocarbon-water system during high temperature action in order to overcome the deficiencies of the prior art.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides an in-situ online detection method for hydroxyl radicals in a hydrocarbon-water system during high temperature action, comprising the following steps:

[0008] 1) Prepare a capillary reactor: remove the coating on the bottom of the fused silica capillary to serve as the sample detection end; then clean, dry, and seal both ends of the fused silica capillary in sequence;

[0009] The uncoated end of the fused silica capillary is inserted into the valve assembly, the valve assembly and the fused silica capillary are bonded and then dried and solidified; the fused silica capillary is cut open near the end of the valve assembly to serve as the sample injection end;

[0010] 2) preparing a capillary syringe: bonding a fused silica capillary to a disposable syringe and then drying and solidifying the resulting capillary syringe;

[0011] 3) preparing a test solution: mixing a hydrocarbon solution and a paramagnetic capture agent to obtain a hydrocarbon mixed solution, and the hydrocarbon mixed solution and water simulate the organic-inorganic interaction process of a hydrocarbon-water system;

[0012] 4) Sample injection: insert the capillary syringe of step 2) into the capillary reactor of step 1), inject the aqueous solution and the hydrocarbon mixture into the capillary reactor in sequence, connect the sample detection end of the capillary reactor to the valve assembly, insert the sample injection end of the capillary reactor into the high-temperature and high-pressure valve, and close the valve to seal, thereby obtaining the capillary reactor of the experimental group;

[0013] During the process of injecting the hydrocarbon mixture, the capillary syringe is slowly withdrawn outwards, so that the hydrocarbon mixture is discontinuously divided into short columns in the aqueous solution, until the capillary syringe is completely removed from the capillary reactor, completing the "hydrocarbon-water-hydrocarbon-water-hydrocarbon-water..." multiple "hydrocarbon-water" interfaces;

[0014] One end of the capillary reactor of step 1) is connected to the valve assembly, and the other end is inserted into the high-temperature and high-pressure valve. The other end of the high-temperature and high-pressure valve is connected to a vacuum pump, and the inside of the capillary reactor is evacuated. After closing the high-temperature and high-pressure valve, a capillary reactor of the control group is obtained;

[0015] 5) Sample detection: the sample detection ends of the capillary reactors of the experimental group and the control group are respectively placed downward, and the samples are detected in an electron paramagnetic resonance spectrometer to obtain the EPR spectra of the experimental group and the EPR spectra of the control group;

[0016] 6) Image analysis: The EPR spectrum of the control group was used as the background value, and the EPR spectrum of the experimental group was cut out of the background, and then smoothed and denoised to obtain the free radical signal of the "hydrocarbon-water" system in the experimental group.

[0017] Preferably, the valve assembly in step 1) consists of a hollow stainless steel tube, a ball valve assembly and a high-temperature and high-pressure valve, and the length of the hollow stainless steel tube is 1.5 to 2.5 cm and the inner diameter is 1.5 to 2.5 mm.

[0018] Preferably, the cross-section of the fused silica capillary in step 1) is circular, the inner diameter of the fused silica capillary is 200-400 μm, and the outer diameter is 800-1200 μm; the length of the fused silica capillary is greater than the distance between the sample inlet and the detection window of the electron paramagnetic resonance spectrometer.

[0019] Preferably, the coating is removed in step 1) at a position 3 to 5 cm from the bottom of the fused silica capillary; the bonding position is 1 to 2 cm from the top of the fused silica capillary, and the ball valve assembly end faces outward.

[0020] Preferably, the drying and curing temperatures in step 1) and step 2) are independently 35-45° C., and the drying and curing time is independently 23-25 ​​h.

[0021] Preferably, in step 2), the cross-section of the fused silica capillary is circular, the length of the fused silica capillary is ≥20 cm, the capacity of the disposable syringe is 2.5-5.0 mL, and the bonding position is 1-2 cm away from the top of the fused silica capillary.

[0022] Preferably, the hydrocarbon solution in step 3) includes but is not limited to n-hexadecane and crude oil.

[0023] Preferably, in step 4), the liquid outlet end of the capillary syringe is located at the bottom of the capillary reactor, and the aqueous solution is injected until the aqueous solution overflows from the injection end of the capillary reactor;

[0024] After the injection of the aqueous solution is completed, the liquid outlet end of the capillary syringe is fixed and the hydrocarbon mixture is injected; the length of the short columnar hydrocarbon mixture is ≤500 μm.

[0025] Preferably, in step 5), the detection temperature is 180-220° C., the detection time is 5-10 min, the magnetic field strength is 1.8-2.2 G, the frequency is 90-110 kHz, and the power is 1.8-2.2 mW.

[0026] The beneficial effects of the present invention include the following:

[0027] 1) The present invention uses a fused silica capillary and a high-pressure valve to seal hydrocarbons and aqueous solutions to be detected, and adjusts the injection ratio and position of different solutions to seal multiple sections of "hydrocarbon-water" interfaces in the quartz capillary system, so that the oil-water interface of the hydrocarbon-water system in the capillary is densely arranged near the detection point, increasing the distribution density of oil and water droplets near the interface under high temperature conditions and the large-scale generation of corresponding free radicals, improving the capture ability of the capture agent for free radicals, and improving the signal-to-noise ratio of the effective signal, avoiding the problem of low signal intensity and distortion caused by the movement of the oil-water interface at a single interface or near the detection point; at the same time, by filling the capillary with hydrocarbon-water fluid and then sealing it, it is avoided that the existence of the cavity in the tube after heating causes the liquid to be vaporized, resulting in an unstable hydrocarbon-water interface.

[0028] 2) High-temperature ERP detection is performed on the cavity of the fused silica capillary as the background value for correction, eliminating the influence of oxygen vacancies or lattice defects in the quartz capillary as a sample reaction container on the test signal. Therefore, it is possible to perform high-precision electron paramagnetic resonance spectrum measurement on the hydrocarbon-water system interaction process at a microscopic scale in a high-temperature sealed environment, and detect free radicals that appear in the organic-inorganic interaction process under high-temperature conditions, thereby providing the most direct evidence support for the study of organic-inorganic interaction pathways and material transfer processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the preparation steps of the capillary reactor of the present invention;

[0030] Figure 2 This is a diagram of the oil-water interface distribution state after the sample is injected observed under a polarizing microscope in Example 1;

[0031] Figure 3 is a schematic diagram of an electron paramagnetic resonance spectrometer of the present invention;

[0032] Figure 4 The processing steps of the EPR spectrum of Example 1;

[0033] Figure 5 The EPR spectra of Examples 1 to 4 are shown. DETAILED DESCRIPTION

[0034] The present invention provides an in-situ online detection method for hydroxyl radicals in a hydrocarbon-water system during high temperature action, comprising the following steps:

[0035] 1) Prepare a capillary reactor: remove the coating on the bottom of the fused silica capillary to serve as the sample detection end; then clean, dry, and seal both ends of the fused silica capillary in sequence;

[0036] The uncoated end of the fused silica capillary is inserted into the valve assembly, the valve assembly and the fused silica capillary are bonded and then dried and solidified; the fused silica capillary is cut open near the end of the valve assembly to serve as the sample injection end;

[0037] 2) preparing a capillary syringe: bonding a fused silica capillary to a disposable syringe and then drying and solidifying the resulting capillary syringe;

[0038] 3) preparing a test solution: mixing a hydrocarbon solution and a paramagnetic capture agent to obtain a hydrocarbon mixed solution, and the hydrocarbon mixed solution and water simulate the organic-inorganic interaction process of a hydrocarbon-water system;

[0039] 4) Sample injection: insert the capillary syringe of step 2) into the capillary reactor of step 1), inject the aqueous solution and the hydrocarbon mixture into the capillary reactor in sequence, connect the sample detection end of the capillary reactor to the valve assembly, insert the sample injection end of the capillary reactor into the high-temperature and high-pressure valve, and close the valve to seal, thereby obtaining the capillary reactor of the experimental group;

[0040] During the process of injecting the hydrocarbon mixture, the capillary syringe is slowly withdrawn outwards, so that the hydrocarbon mixture is discontinuously divided into short columns in the aqueous solution, until the capillary syringe is completely removed from the capillary reactor, completing the "hydrocarbon-water-hydrocarbon-water-hydrocarbon-water..." multiple "hydrocarbon-water" interfaces;

[0041] One end of the capillary reactor of step 1) is connected to the valve assembly, and the other end is inserted into the high-temperature and high-pressure valve. The other end of the high-temperature and high-pressure valve is connected to a vacuum pump, and the inside of the capillary reactor is evacuated. After closing the high-temperature and high-pressure valve, a capillary reactor of the control group is obtained;

[0042] 5) Sample detection: the sample detection ends of the capillary reactors of the experimental group and the control group are respectively placed downward, and the samples are detected in an electron paramagnetic resonance spectrometer to obtain the EPR spectra of the experimental group and the EPR spectra of the control group;

[0043] 6) Image analysis: The EPR spectrum of the control group was used as the background value, and the EPR spectrum of the experimental group was cut out of the background, and then smoothed and denoised to obtain the free radical signal of the "hydrocarbon-water" system in the experimental group.

[0044] In the present invention, the valve assembly in step 1) is preferably composed of a hollow stainless steel tube, a ball valve assembly and a high-temperature and high-pressure valve. The length of the hollow stainless steel tube is preferably 1.5 to 2.5 cm, more preferably 1.8 to 2.2 cm, and more preferably 2 cm. The inner diameter is preferably 1.5 to 2.5 mm, more preferably 1.8 to 2.2 mm, and more preferably 2 mm.

[0045] In the present invention, the cross-section of the fused silica capillary in step 1) is preferably circular, the inner diameter of the fused silica capillary is preferably 200-400 μm, more preferably 250-350 μm, more preferably 300 μm, and the outer diameter is preferably 800-1200 μm, more preferably 900-1100 μm, more preferably 1000 μm; the length of the fused silica capillary is greater than the distance from the sample inlet to the detection window of the electron paramagnetic resonance spectrometer.

[0046] In the present invention, the coating removal position in step 1) is preferably 3 to 5 cm from the bottom of the fused silica capillary, and more preferably 4 cm from the bottom of the fused silica capillary; the bonding position is preferably 1 to 2 cm from the top of the fused silica capillary, with the ball valve assembly end facing outward.

[0047] In the present invention, the cleaning reagent in step 1) preferably comprises alcohol and water, the number of alcohol and water cleanings is preferably 2 to 3 times independently, the drying temperature is preferably 57 to 63°C, more preferably 60°C, and the two ends are preferably welded and sealed using a hydrogen-oxygen welding gun.

[0048] In the present invention, for the EPR200Plus electron paramagnetic resonance spectrometer, the length of the fused silica capillary is preferably ≥240 mm; the fused silica capillary is an experimental detection capillary used to seal a hydrocarbon-water solution and to create a plurality of hydrocarbon-water interfaces.

[0049] In the present invention, the drying and curing temperatures in step 1) and step 2) are independently preferably 35-45°C, more preferably 38-42°C, and more preferably 40°C, and the drying and curing time is independently preferably 23-25h, more preferably 23.5-24.5h, and more preferably 24h.

[0050] In the present invention, the bonding agent in step 1) and step 2) is preferably AB glue, and the purpose of drying and curing is to solidify the AB glue.

[0051] In the present invention, the cross-section of the fused silica capillary in step 2) is preferably circular, the length of the fused silica capillary is preferably ≥20 cm, more preferably ≥23 cm, more preferably ≥25 cm, the capacity of the disposable syringe is preferably 2.5 to 5.0 mL, more preferably 2.5 mL; the bonding position is preferably 1 to 2 cm away from the top of the fused silica capillary, more preferably 1.5 cm away from the top of the fused silica capillary.

[0052] In the present invention, the hydrocarbon solution in step 3) includes but is not limited to n-hexadecane and crude oil.

[0053] In the present invention, the paramagnetic capture agent is preferably 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), which is used to capture hydroxyl radicals or superoxide anions generated during the organic-inorganic interaction process.

[0054] In the present invention, the liquid outlet end of the capillary syringe in step 4) is preferably located at the bottom of the capillary reactor, and the aqueous solution is injected until the aqueous solution overflows from the injection end of the capillary reactor;

[0055] After the injection of the aqueous solution is completed, the liquid outlet end of the capillary syringe is fixed and the hydrocarbon mixture is injected; the length of the short columnar hydrocarbon mixture is preferably ≤500 μm.

[0056] In the present invention, step 4) is preferably evacuated to a vacuum degree of -0.9 to 1.0 bar, more preferably -0.96 bar.

[0057] In the present invention, after the solution injection is completed, the sample detection end of the capillary reactor is placed under a polarizing microscope to observe the distribution of the hydrocarbon mixture to ensure that there is no air residue in the capillary, and the number and length of the hydrocarbon mixture segments in the detection window and the number of oil-water interfaces are recorded.

[0058] In the present invention, the test solution is not injected into the capillary reactor of the control group. After the vacuum pump is started and the valve switch is opened, the interior of the capillary reactor is evacuated. After the vacuum negative pressure reaches -0.9 to 1.0 bar, the valve switch and the vacuum pump are closed, and the valve and the capillary reactor are removed from the vacuum pump.

[0059] In the present invention, the detection temperature in step 5) is preferably 180-220°C, more preferably 190-210°C, and more preferably 200°C. The detection time is preferably 5-10 min, more preferably 6-9 min, and more preferably 7-8 min. The detected magnetic field intensity is preferably 1.8-2.2 G, more preferably 1.9-2.1 G, and more preferably 2 G. The detected frequency is preferably 90-110 kHz, more preferably 95-105 kHz, and more preferably 100 kHz. The detected power is preferably 1.8-2.2 mW, more preferably 1.9-2.1 mW, and more preferably 2 mW.

[0060] In step 5) of the present invention, under the protection of a non-magnetic silicon tube, the sample detection ends of the capillary reactors of the experimental group and the control group are placed downward into an electron paramagnetic resonance spectrometer, preferably an EPR200-plus electron paramagnetic resonance spectrometer.

[0061] In the present invention, the purpose of the smoothing and noise reduction processing in step 6) is to highlight the obtained free radical signal.

[0062] The schematic diagram of the preparation steps of the capillary reactor of the present invention is as follows Figure 1 shown.

[0063] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0064] In the embodiment, the fused silica capillary was purchased from Polymicro Technologies, USA, the air drying oven was Shanghai Yiheng DHG-9145A air drying oven, the AB glue was Red Star brand fully transparent 509AB glue produced by Ningbo Tiandong Adhesive Co., Ltd., the high temperature and high pressure valve was the American HIP straight-through high pressure needle valve 15-11AF1 type, the polarizing microscope was AxToScope.A1APoL polarizing microscope, and the electron paramagnetic resonance spectrometer was EPR200-plus electron paramagnetic resonance spectrometer.

[0065] Example 1

[0066] (1) Preparation of capillary reactor: Select 5 fused silica capillaries with circular cross-sections, with a length of 240 mm, an inner diameter of 400 μm, and an outer diameter of 800 μm. Use the outer flame of an alcohol lamp to burn off the polyimide coating within 5 cm from the bottom of the capillary, which is used as the sample detection end. Then use an ear-cleaning bulb to blow away the polyimide residue, and clean the capillary wall and inner wall with alcohol and deionized water, and wash with alcohol and deionized water 3 times each. Put the cleaned quartz capillary into a blast drying oven and dry it at 60°C, and then use a hydrogen-oxygen welding gun to weld and seal the two ends of the dried quartz capillary.

[0067] Insert the valve assembly from the unburned coating end of the quartz capillary, and use AB glue to bond the valve assembly to the quartz capillary. The bonding and fixing position is 1 cm away from the top of the quartz capillary, and the end of the ball valve assembly faces outward. The valve assembly consists of a hollow stainless steel tube (length 2 cm, inner diameter 2 mm), a fixed ball valve assembly and a high-temperature and high-pressure valve. After cleaning the glue seeping from the wall of the quartz capillary, the quartz capillary is placed in a blast drying oven and dried at a constant temperature of 40°C for 24 hours to solidify the glue. After solidification, use a ceramic blade to cut the quartz capillary close to the valve assembly end as the sample injection end.

[0068] (2) Preparation of a capillary syringe: A fused silica capillary with a circular cross-section and an outer diameter of 150 μm and a length of 25 cm was selected and connected to a disposable syringe with a capacity of 2.5 mL. The interface between the syringe and the capillary was bonded with AB glue. The bonding position was 2 cm away from the top of the quartz capillary. After cleaning the glue that had seeped from the wall of the quartz capillary, the quartz capillary was placed in a forced air drying oven and dried at a constant temperature of 40°C for 24 h to solidify the glue, thereby obtaining a capillary syringe.

[0069] (3) Preparation of test solution: n-hexadecane was used as the hydrocarbon solution, and 0.2 mmol of EPR paramagnetic capture agent (DMPO) was added to 5 mL of n-hexadecane to obtain a hydrocarbon mixed solution. Distilled water was used as the aqueous solution to simulate the organic-inorganic interaction process of the hydrocarbon-water system and to detect the generation of free radicals near the oil-water interface.

[0070] (4) Sample injection: insert the capillary syringe into the capillary reactor so that its liquid outlet is located at the bottom of the capillary reactor, and inject the aqueous solution into the capillary reactor until the aqueous solution overflows from the injection end of the capillary reactor. At this time, fix the liquid outlet end of the capillary syringe and replace the injection solution with a hydrocarbon mixture. During the injection of the hydrocarbon mixture, slowly withdraw the capillary syringe so that the hydrocarbon mixture appears in the aqueous solution in short columnar (length <500 μm) segments and is discontinuous until the capillary syringe is completely removed from the capillary reactor, completing the "hydrocarbon-water-hydrocarbon-water-hydrocarbon-water..." multiple "hydrocarbon-water" interfaces.

[0071] After the sample injection is completed, the sample detection end of the capillary reactor is placed under a polarizing microscope to observe the distribution of hydrocarbon solutions, and the number of oil-water interfaces in the detection window is counted (the number of oil-water interfaces in the detection area is 20). The capillary reactor with the sample added is fixed to the high-temperature and high-pressure valve with a nut. First, the nut is inserted from the sample detection end of the capillary, so that the threaded end of the nut is sleeved on the valve assembly, and then the sample injection end is inserted into the high-temperature and high-pressure valve, and the nut is tightened to completely fix the capillary reactor on the high-temperature and high-pressure valve, and the valve is closed to obtain the capillary reactor of the experimental group.

[0072] Take another prepared capillary reactor, do not inject the test solution, connect one end of the capillary reactor to the valve assembly, insert the other end into the high-temperature and high-pressure valve, connect the other end of the high-temperature and high-pressure valve to the vacuum pump, start the vacuum pump and open the valve switch to evacuate the inside of the capillary reactor. When the vacuum negative pressure reaches -0.96 bar, close the valve switch and the vacuum pump, remove the valve and the capillary reactor from the vacuum pump, and obtain the capillary reactor of the control group (the number of oil-water interfaces in the detection area is 0).

[0073] (5) EPR test: Under the protection of a non-magnetic silicon tube, the capillary reactors of the experimental group and the control group were placed in an electron paramagnetic resonance spectrometer with the detection end facing downward. The heating module was set to 200°C, and the test modulation magnetic field strength was 2G, the frequency was 100kHz, and the power was 2mW. After stabilization for 10 minutes, the EPR spectra were measured and obtained. The EPR spectra of the control group and the experimental group were detected and obtained respectively.

[0074] (6) Subtracting capillary vacancy signals and image analysis: Using image analysis software, the EPR curve of the control group is used as the background value, and the EPR spectrum of the experimental group is subtracted from the background. The obtained free radical signal is smoothed and denoised to highlight the obtained free radical signal, thereby obtaining the signal of free radicals in the hydrocarbon-water system during the actual reaction process.

[0075] Example 2

[0076] The number of oil-water interfaces in the detection area is 1, and other conditions are the same as those in Example 1.

[0077] Example 3

[0078] The n-hexadecane in Example 1 was replaced by crude oil, and other conditions were the same as in Example 1.

[0079] Example 4

[0080] The n-hexadecane in Example 1 was replaced by crude oil, the number of oil-water interfaces in the detection area was 1, and the other conditions were the same as in Example 1.

[0081] The distribution state of the oil-water interface after the sample injection was observed under the polarizing microscope of Example 1 is as follows: Figure 2 As shown, the first view and the second view together represent a whole sample, with a total of 20 hydrocarbon-water interfaces; the schematic diagram of the electron paramagnetic resonance spectrometer of the present invention is shown in Figure 3 As shown; the processing steps of the EPR spectrum of Example 1 are as follows Figure 4 As shown, A is the spectrum obtained from the original detection data, B is the spectrum obtained after A is background removed, C is the spectrum obtained after baseline smoothing based on B, and D is the final spectrum obtained after noise reduction processing of C; the EPR spectra of Examples 1 to 4 are shown Figure 5shown.

[0082] Analysis of the EPR spectra of Examples 1 to 4 shows that, whether the hydrocarbon solution is n-hexadecane or crude oil, the free radical signal can be effectively captured only when and only when there are more oil-water interfaces in the detection area. By comparison, it is found that in Examples 1 and 3, hydroxyl radicals and alkyl radicals are generated, while in Examples 2 and 4, although the number and position of the oil-water interface did not change before and after the experiment, the number of hydroxyl or other types of free radicals generated in the system was still lower than the detection line, and no effective free radical signal appeared in the EPR spectra after image processing. Therefore, by using a high-temperature and high-pressure valve to seal the solution in the reactor in a capillary reactor, multiple groups of oil-water interfaces can appear in the detection area under high temperature conditions, thereby promoting the generation of droplets of hydrocarbons or aqueous solutions and improving the capture efficiency of free radical scavengers, so that the free radical intermediates generated in the organic-inorganic reaction process in the hydrocarbon-water system can be recorded by electron paramagnetic resonance. In addition, after image processing, the oxygen vacancy signal generated by the empty capillary can be effectively suppressed, thereby eliminating the limitations of the fused silica capillary in electron paramagnetic detection, and providing new experimental methods and research ideas for detecting organic-inorganic interactions and conducting in situ thermal simulation experiments using capillary systems.

[0083] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An in-situ online detection method for hydroxyl radicals in a hydrocarbon-water system during high temperature action, characterized in that: The following steps are included: 1) Prepare a capillary reactor: remove the coating on the bottom of the fused silica capillary to serve as the sample detection end; then clean, dry, and seal both ends of the fused silica capillary in sequence; The uncoated end of the fused silica capillary is inserted into the valve assembly, and the valve assembly and the fused silica capillary are bonded and then dried and solidified; The fused silica capillary was cut near the valve assembly end to serve as the sample injection end; 2) preparing a capillary syringe: bonding a fused silica capillary to a disposable syringe and then drying and solidifying the resulting capillary syringe; 3) preparing a test solution: mixing a hydrocarbon solution and a paramagnetic capture agent to obtain a hydrocarbon mixed solution, and the hydrocarbon mixed solution and water simulate the organic-inorganic interaction process of a hydrocarbon-water system; 4) Sample injection: insert the capillary syringe of step 2) into the capillary reactor of step 1), inject the aqueous solution and the hydrocarbon mixture into the capillary reactor in sequence, connect the sample detection end of the capillary reactor to the valve assembly, insert the sample injection end of the capillary reactor into the high-temperature and high-pressure valve, and close the valve to seal, thereby obtaining the capillary reactor of the experimental group; During the process of injecting the hydrocarbon mixture, the capillary syringe is slowly withdrawn outwards, so that the hydrocarbon mixture is discontinuous in the aqueous solution in the form of short columns, until the capillary syringe is completely removed from the capillary reactor, completing the "hydrocarbon-water-hydrocarbon-water-hydrocarbon-water..." multiple "hydrocarbon-water" interfaces; One end of the capillary reactor of step 1) is connected to the valve assembly, and the other end is inserted into the high-temperature and high-pressure valve. The other end of the high-temperature and high-pressure valve is connected to a vacuum pump, and the inside of the capillary reactor is evacuated. After closing the high-temperature and high-pressure valve, a capillary reactor of the control group is obtained; 5) Sample detection: the sample detection ends of the capillary reactors of the experimental group and the control group are respectively placed downward, and the samples are detected in an electron paramagnetic resonance spectrometer to obtain the EPR spectra of the experimental group and the EPR spectra of the control group; 6) Image analysis: The EPR spectrum of the control group was used as the background value, and the EPR spectrum of the experimental group was cut out of the background, and then smoothed and denoised to obtain the free radical signal of the "hydrocarbon-water" system in the experimental group.

2. The in-situ online detection method according to claim 1, characterized in that: Step 1) The valve assembly consists of a hollow stainless steel tube, a ball valve assembly and a high-temperature and high-pressure valve. The length of the hollow stainless steel tube is 1.5 to 2.5 cm and the inner diameter is 1.5 to 2.5 mm.

3. The in-situ online detection method according to claim 1 or 2, characterized in that: Step 1) The cross section of the fused silica capillary is circular, the inner diameter of the fused silica capillary is 200-400 μm, and the outer diameter is 800-1200 μm; the length of the fused silica capillary is greater than the distance between the sample inlet and the detection window of the electron paramagnetic resonance spectrometer.

4. The in-situ online detection method according to claim 3, characterized in that: Step 1) The coating removal position is 3 to 5 cm from the bottom of the fused silica capillary; the bonding position is 1 to 2 cm from the top of the fused silica capillary, and the ball valve assembly end faces outward.

5. The in-situ online detection method according to claim 3, characterized in that: The drying and curing temperatures in step 1) and step 2) are independently 35-45° C., and the drying and curing time is independently 23-25 ​​hours.

6. The in-situ online detection method according to claim 1 or 5, characterized in that: Step 2) The cross section of the fused silica capillary is circular, the length of the fused silica capillary is ≥20 cm, the capacity of the disposable syringe is 2.5-5.0 mL; the bonding position is 1-2 cm away from the top of the fused silica capillary.

7. The in-situ online detection method according to claim 6, characterized in that: Step 3) The hydrocarbon solution includes but is not limited to n-hexadecane and crude oil.

8. The in-situ online detection method according to claim 7, characterized in that: Step 4) the liquid outlet end of the capillary syringe is located at the bottom of the capillary reactor, and the aqueous solution is injected until the aqueous solution overflows from the injection end of the capillary reactor; After the injection of the aqueous solution is completed, the liquid outlet end of the capillary syringe is fixed and the hydrocarbon mixture is injected; The length of the short columnar hydrocarbon mixture is ≤500 μm.

9. The in-situ online detection method according to claim 7 or 8, characterized in that: Step 5) The detection temperature is 180-220° C., the time is 5-10 min, the magnetic field strength is 1.8-2.2 G, the frequency is 90-110 kHz, and the power is 1.8-2.2 mW.

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