Preparation method of water droplets in hydrocarbon-water system

Abstract

The invention belongs to the technical field of water microdroplet manufacturing, and provides a preparation method of water microdroplets in a hydrocarbon-water system. The method comprises the following steps: preparing a quartz capillary reaction tube; preparing a microdroplet observation end and a sample injection end; sample injection: respectively inserting thin capillary syringes filled with water and hydrocarbon liquid into the quartz capillary reaction tubes, and injecting the water and the hydrocarbon liquid; fixing the quartz capillary reaction tube; preparing liquid drops, namely adjusting the temperature and the pressure in the quartz capillary reaction tube by using a cold and hot table and a constant-pressure liquid pump. The fused quartz capillary is utilized to quickly prepare the water microdroplets in a hydrocarbon-water system under high-temperature and high-pressure conditions, so that the defects that a traditional emulsification method depends on a large number of surfactants to introduce impurities and is unstable at high temperature and high pressure, microfluidic technical equipment is complex, the cost is high, the microdroplets are easy to damage at high temperature and high pressure, the preparation efficiency is low and the like are overcome; and a new way is opened up for preparing the water microdroplets under high-temperature and high-pressure conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water droplet manufacturing, and particularly relates to a preparation method of water droplets in a "hydrocarbon-water" system. BACKGROUND

[0002] In many fields such as material science, biomedical science, and chemical engineering, microdroplet manufacturing technology has always been one of the research hotspots. Traditional water droplet manufacturing methods such as emulsification and microfluidic technology can achieve the preparation of water droplets to some extent, but still have many limitations when facing some special needs.

[0003] At present, traditional water droplet manufacturing technology is mostly applied under normal temperature and pressure. In special fields involving high temperature and high pressure, such as the preparation of reservoir displacement agents in oil exploitation, the construction of high-temperature and high-pressure catalytic reaction systems, and the simulation of formation environment in geological research, the application of traditional technology is extremely limited. The emulsification method usually needs a large amount of surfactant to maintain the stability of the emulsion, which not only introduces impurities and affects the subsequent application, but also the surfactant may decompose or change in properties under high temperature and high pressure, making it difficult to accurately control the size and monodispersity of the droplets. Although the microfluidic technology can achieve high-precision droplet generation, the device is complex and costly, the internal microchannel structure is easily deformed and damaged under high temperature and high pressure, and the preparation efficiency is low, which cannot meet the needs of large-scale production.

[0004] With the continuous development of science and technology, the demand for rapid water droplet manufacturing in a "hydrocarbon-water" system is increasingly urgent. Such a system can provide a unique reaction environment and has great application potential in the fields of nanomaterial synthesis, drug delivery, and catalytic reaction. In particular, in the field of high temperature and high pressure, the lack of water droplet manufacturing technology in the "hydrocarbon-water" system greatly limits the development of related research and industrial applications. At present, there is still a relative lack of rapid water droplet manufacturing technology for the "hydrocarbon-water" system, and the existing technology cannot well balance the requirements of rapid preparation, accurate size control, and good stability, and it is difficult to meet the needs under high temperature and high pressure.

[0005] Therefore, it is of great practical significance and application value to develop an efficient, accurate, and stable method for rapid water droplet manufacturing in a "hydrocarbon-water" system, which can effectively promote the further development of related fields. SUMMARY

[0006] The present application relates to the technical field of water droplet manufacturing, and particularly relates to a preparation method of water droplets in a "hydrocarbon-water" system.

[0007] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0008] The present application provides a method for preparing water microdroplets in a "hydrocarbon-water" system, comprising the following steps:

[0009] 1) Preparing a quartz capillary reaction tube: removing the coating at the bottom of the fused quartz capillary tube as the microdroplet observation end; then sequentially cleaning, drying and welding the two ends of the fused quartz capillary tube;

[0010] The fused quartz capillary tube is inserted into the conical sleeve at the end without coating, and the conical sleeve and the fused quartz capillary tube are bonded and then dried and solidified; the end of the fused quartz capillary tube close to the conical sleeve is cut open as the sample injection end;

[0011] 2) Sample injection: inserting a fine capillary syringe containing water into the bottom of the quartz capillary reaction tube to inject water;

[0012] Inserting a fine capillary syringe containing a hydrocarbon liquid into the quartz capillary reaction tube until the tip of the fine capillary syringe contacts the water interface, injecting the hydrocarbon liquid until the injection end overflows with the hydrocarbon liquid, and the hydrocarbon-water interface is free of impurities and bubbles, and the sample loading is completed;

[0013] 3) Fixing the quartz capillary reaction tube: connecting the sample-loaded quartz capillary reaction tube with a high-pressure needle valve, and then inserting it into a cooling and heating stage, with the microdroplet observation end of the quartz capillary reaction tube above the temperature control plate of the cooling and heating stage, and using a silver sheet to fix the quartz capillary reaction tube;

[0014] 4) Droplet preparation: gradually increasing the temperature and pressure in the quartz capillary reaction tube using the cooling and heating stage and a constant-pressure liquid pump until water microdroplets form at the hydrocarbon-water interface; then reducing the temperature and pressure of the quartz capillary reaction tube using the cooling and heating stage and the constant-pressure liquid pump.

[0015] Preferably, the conical sleeve in step 1) is composed of a hollow stainless steel tube and a ball valve assembly, with the length of the hollow stainless steel tube being 1.8-2.2 cm and the inner diameter being 1.8-2.2 mm.

[0016] Preferably, the cross section of the fused quartz capillary tube in step 1) is circular, with the inner diameter of the fused quartz capillary tube being 200-400 μm, the outer diameter being 800-1200 μm, and the length being 18-25 cm.

[0017] Preferably, the position of removing the coating in step 1) is 3-5 cm away from the bottom of the fused quartz capillary tube; the position of bonding is 1-2 cm away from the top end of the fused quartz capillary tube, and the ball valve assembly end faces outward.

[0018] Preferably, the drying temperature in step 1) is 58-62°C, and the drying and solidification temperature is 38-43°C, with the time being 23-24.5 h.

[0019] Preferably, the water injection amount in step 2) is to form a liquid column with a height of 2-3 cm in the quartz capillary reaction tube.

[0020] Preferably, the length of the fine capillary injector in step 2) is ≥20 cm, and the outer diameter is 150-200 μm; the fine capillary injector is extracted outward while the water is injected, and the fine capillary injector is extracted outward while the hydrocarbon liquid is injected.

[0021] Preferably, the hydrocarbon liquid in step 2) comprises n-hexadecane.

[0022] Preferably, in step 4), the initial pressure is 4.8-5.2 MPa, the initial temperature is 22-26℃, the temperature is raised to 170-200℃, the pressure is raised to 42-48 MPa, the temperature is lowered to 22-120℃, and the pressure is lowered to 5-30 MPa.

[0023] The beneficial effects of the present application include:

[0024] The present application utilizes a fused quartz capillary to rapidly prepare water microdroplets in a "hydrocarbon-water" system under high temperature and high pressure conditions, avoids the drawbacks of traditional emulsification methods, such as the introduction of impurities due to the use of a large amount of surfactants, instability under high temperature and high pressure, complex equipment, high cost, easy damage under high temperature and high pressure, and low preparation efficiency, and opens up a new way for the preparation of water microdroplets under high temperature and high pressure conditions. By adjusting the temperature and pressure conditions of the "hydrocarbon-water" system in the quartz capillary system, a large number of water microdroplets can be rapidly generated in a short time, significantly improving the preparation efficiency. Moreover, since a large amount of surfactants is not required, the introduction of impurities is effectively reduced, and the purity of the microdroplets is improved, laying a good foundation for subsequent applications. The rapid preparation method of water microdroplets of the present application is suitable for scenarios under high temperature and high pressure conditions, such as oil extraction, high temperature and high pressure catalytic reaction system construction, and geological research simulation of formation environment experiments, filling the gap of "hydrocarbon-water" system water microdroplet manufacturing technology in the field of high temperature and high pressure, and promoting the technological progress and industrial application development in related fields, providing key technical support for in-depth exploration of material interaction and reaction mechanism in various fields. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A device for rapid preparation of water microdroplets in a "hydrocarbon-water" system under high temperature and high pressure conditions;

[0026] Figure 2 An image of the interface between deionized water and n-hexadecane in the quartz capillary reaction tube under the initial temperature and pressure (24℃ / 5MPa) state of Example 1 under transmitted light of an optical microscope;

[0027] Figure 3The image of the interface between deionized water and n-hexadecane in the quartz capillary reaction tube of Example 1 under the high temperature and high pressure (180℃ / 45MPa) state under the optical microscope transmission light state;

[0028] Figure 4 The image of the interface between deionized water and n-hexadecane in the quartz capillary reaction tube of Example 1 under the temperature and pressure rapidly reduced to 24℃ / 5MPa state under the optical microscope transmission light state. DETAILED DESCRIPTION

[0029] The present application provides a preparation method of water droplets in a "hydrocarbon-water" system, comprising the following steps:

[0030] 1) Preparation of a quartz capillary reaction tube: removing the coating at the bottom of the fused quartz capillary tube as the droplet observation end; and then sequentially cleaning, drying and welding-sealing the two ends of the fused quartz capillary tube;

[0031] The end of the fused quartz capillary tube close to the conical sleeve is cut open as the sample injection end; and the end of the fused quartz capillary tube without the coating is sleeved into the conical sleeve, and the conical sleeve and the fused quartz capillary tube are bonded and then dried and solidified;

[0032] 2) Sample injection: inserting a fine capillary syringe containing water into the bottom of the quartz capillary reaction tube, and injecting water;

[0033] Inserting a fine capillary syringe containing a hydrocarbon liquid into the quartz capillary reaction tube until the tip of the fine capillary syringe contacts the water interface, and injecting the hydrocarbon liquid until the hydrocarbon liquid overflows from the injection end, and the hydrocarbon-water interface is free of impurities and bubbles, and the sample loading is completed;

[0034] 3) Quartz capillary reaction tube fixation: connecting the sample-loaded quartz capillary reaction tube with a high-pressure needle valve, and then inserting it into a cooling and heating stage, with the droplet observation end of the quartz capillary reaction tube located above the temperature control plate of the cooling and heating stage, and using a silver sheet to fix the quartz capillary reaction tube;

[0035] 4) Droplet preparation: gradually increasing the temperature and pressure in the quartz capillary reaction tube using the cooling and heating stage and a constant-pressure liquid pump until water microdroplets are formed at the hydrocarbon-water interface; and then reducing the temperature and pressure of the quartz capillary reaction tube using the cooling and heating stage and the constant-pressure liquid pump.

[0036] In the present application, the conical sleeve in step 1) is preferably composed of a hollow stainless steel tube and a ball valve assembly, the length of the hollow stainless steel tube is preferably 1.8-2.2 cm, further preferably 1.9-2.1 cm, and more preferably 2 cm, and the inner diameter of the hollow stainless steel tube is preferably 1.8-2.2 mm, further preferably 1.9-2.1 mm, and more preferably 2 mm.

[0037] In the present application, the cross section of the fused quartz capillary in step 1) is preferably circular, the inner diameter of the fused quartz capillary is preferably 200-400 μm, further preferably 250-350 μm, more preferably 300 μm, the outer diameter is preferably 800-1200 μm, further preferably 900-1100 μm, more preferably 1000 μm, and the length is preferably 18-25 cm, further preferably 20-24 cm, more preferably 22-23 cm.

[0038] In the present application, the position of removing the coating in step 1) is preferably 3-5 cm from the bottom of the fused quartz capillary, further preferably 3.5-4.5 cm, more preferably 4 cm; the position of the adhesion is preferably 1-2 cm from the top end of the fused quartz capillary, further preferably 1.5 cm, and the ball valve assembly end is outward.

[0039] In the present application, the outer flame of the alcohol lamp is used to burn the position 3-5 cm from the bottom of the fused quartz capillary to remove the polyimide coating at this position, ensuring that the coating can be effectively removed without damaging the fused quartz capillary; after removing the coating, the polyimide residue is blown off with an ear cleaning ball, and then the tube wall and inner wall of the fused quartz capillary are sequentially cleaned with alcohol and water, each for 2-3 times, to ensure that the tube wall and inner wall are free of impurities, and the volume concentration of alcohol is preferably 73-77%, further preferably 75%; the adhesive for adhesion is preferably AB glue, further preferably the full transparent 509 adhesive of the Red Star brand produced by Ningbo Tiandong Adhesive Co., Ltd.

[0040] In the present application, the temperature of drying in step 1) is preferably 58-62℃, further preferably 59-61℃, more preferably 60℃, the temperature of drying and curing is preferably 38-43℃, further preferably 40-42℃, more preferably 41℃, and the time of drying and curing is preferably 23-24.5 h, further preferably 23.5-24 h.

[0041] In the present application, the two ends of the fused quartz capillary are welded with a hydrogen-oxygen welding gun to ensure good sealing; the conical sleeve can be used in cooperation with a high temperature and high pressure valve; after adhesion is completed, the glue solution seeping from the tube wall of the fused quartz capillary is cleaned to ensure the surface of the capillary is clean; the end of the fused quartz capillary close to the conical sleeve is cut open with a ceramic blade.

[0042] In the present application, the injection amount of water in step 2) is preferably to form a liquid column with a height of 2-3 cm in the quartz capillary reaction tube, further preferably 2.5 cm.

[0043] In the present application, the length of the fine capillary injector in step 2) is preferably ≥ 20 cm, further preferably ≥ 22 cm, and more preferably ≥ 25 cm, the outer diameter of the fine capillary injector is preferably 150-200 μm, further preferably 160-190 μm, and more preferably 170-180 μm; the fine capillary injector is pulled out while injecting water, and the fine capillary injector is pulled out while injecting the hydrocarbon liquid.

[0044] In the present application, the hydrocarbon liquid in step 2) preferably comprises n-hexadecane.

[0045] In the present application, the droplet observation end of the quartz capillary reaction tube is wiped clean with anhydrous alcohol before the quartz capillary reaction tube is inserted into the cooling and heating table; the droplet observation end of the quartz capillary reaction tube is located above the temperature control plate of the cooling and heating table, so as to ensure that the droplet observation end can accurately receive temperature control and provide a stable temperature environment; a silver sheet is used to fix the quartz capillary reaction tube, so as to prevent the quartz capillary reaction tube from shaking or tilting during the reaction, thereby affecting the observation effect and test accuracy; the silver sheet is a hollow silver sheet with a slender middle part.

[0046] In the present application, the initial pressure in step 4) is preferably 4.8-5.2 MPa, further preferably 5 MPa, the initial temperature is preferably 22-26℃, further preferably 24℃, the temperature is preferably increased to 170-200℃, further preferably 180-190℃, and more preferably 185℃, the pressure is preferably increased to 42-48 MPa, further preferably 43-47 MPa, and more preferably 45-46 MPa, the temperature is preferably decreased to 22-120℃, further preferably 24-84℃, and more preferably 31.5-56℃, and the pressure is preferably decreased to 5-30 MPa, further preferably 8-20 MPa, and more preferably 10-15 MPa.

[0047] In the present application, the temperature and pressure in the quartz capillary reaction tube are gradually increased to the set temperature and set pressure by using the cooling and heating table and the constant pressure liquid pump, and after being stabilized for 5-10 min, the contact interface between the aqueous solution and the hydrocarbon liquid at the droplet observation end is observed by an optical microscope; then the temperature and pressure of the quartz capillary reaction tube are decreased by using the cooling and heating table and the constant pressure liquid pump, and after being stabilized for 5-10 min, the contact interface between the aqueous solution and the hydrocarbon liquid at the droplet observation end is observed by the optical microscope.

[0048] The technical solutions provided by the present application will be described in detail below in conjunction with the examples, but they should not be understood as limiting the scope of protection of the present application.

[0049] In the examples, the fused quartz capillary tube is a circular cross-section fused quartz capillary tube produced by the American Polymicro Technologies company, with an inner diameter of 400 μm, an outer diameter of 800 μm, and a length of 24 cm.

[0050] The conical sleeve is combined with a ball valve assembly from a hollow stainless steel tube with an inner diameter of 2 mm and a length of 2 cm, and a high-pressure needle valve is a HIP straight-through high-pressure needle valve 15-11AF1 type from the United States, and the conical sleeve can be used with the high-pressure needle valve;

[0051] The air-blast drying oven is a Shanghai Yiheng DHG-9145A air-blast drying oven, the adhesive is a Hongxing brand full-transparent 509 adhesive, the length of the fine capillary injector is 25 cm, the inner diameter is 75 μm, and the outer diameter is 150 μm.

[0052] Example 1

[0053] (1) Preparation of a quartz capillary reaction tube

[0054] An alcohol lamp outer flame is used to burn and remove the polyimide coating at a distance of 5 cm from the bottom of the fused quartz capillary tube, which serves as a microdrop observation end. After removing the coating, an ear cleaning ball is used to thoroughly remove the residual coating residue. Subsequently, the inner and outer walls of the capillary tube are first cleaned with alcohol with a volume concentration of 75%, and then this operation is repeated with deionized water, and the alcohol and deionized water are circulated for cleaning 3 times to ensure that there is no impurity residue on the inner and outer walls of the capillary tube. After cleaning, the capillary tube is placed smoothly into an air-blast drying oven and dried at 60°C, and after the capillary tube is dried, a hydrogen-oxygen welding gun with a flame temperature of 2000°C is used to weld and seal the two ends of the capillary tube for 5 min. The conical sleeve is sleeved at the end of the capillary tube from which the coating is not removed, and is fixed at a distance of 1 cm from the top end of the capillary tube using 509 adhesive, to ensure that the ball valve assembly faces outward.

[0055] After the conical sleeve is installed, the excess glue liquid overflowing from the tube wall is carefully removed to ensure that the surface of the capillary tube is clean. The assembled capillary tube is again placed into an air-blast drying oven and dried at 40°C for 24 h to ensure that the conical sleeve is firmly fixed. Finally, a ceramic blade is used to carefully cut the capillary reaction tube near the conical sleeve, the cutting position is 1 mm away from the end of the capillary reaction tube, and a sample injection port is formed.

[0056] (2) Sample injection

[0057] A fine capillary injector containing deionized water is slowly inserted along the inner wall of the quartz capillary reaction tube to the bottom of the capillary reaction tube, and deionized water is injected into the quartz capillary reaction tube to form a liquid column with a height of 2.5 cm in the capillary reaction tube. While injecting deionized water, the fine capillary injector is slowly pulled out to ensure that the deionized water is uniformly distributed in the capillary reaction tube. Then, a fine capillary injector containing n-hexadecane liquid is inserted along the opening of the conical sleeve until the tip of the fine capillary injector reaches the interface position of the deionized water. While injecting n-hexadecane, the fine capillary injector is continuously and uniformly pulled out. When it is observed that n-hexadecane overflows from the injection end and that there is no impurity and bubble at the "hydrocarbon-water" interface, the sample loading is completed.

[0058] (3) Quartz capillary reaction tube fixation

[0059] After the sample is loaded, connect the quartz capillary reaction tube to the high-pressure needle valve. Use degreased cotton soaked in anhydrous alcohol to wipe the microdroplet observation end of the quartz capillary reaction tube clean. Then insert the quartz capillary reaction tube into the hot and cold stage, so that the microdroplet observation end is placed above the temperature control plate of the hot and cold stage, ensuring that this area can be accurately controlled by temperature. Use a long and thin hollow silver sheet in the middle to fix the quartz capillary reaction tube to prevent it from shaking or tilting upward.

[0060] (4) Droplet preparation

[0061] Heating and pressurization: The temperature and pressure in the quartz capillary reaction tube were gradually increased using a heating and cooling stage and a constant pressure liquid pump. The initial temperature of the quartz capillary reaction tube was 24℃ and the initial pressure was 5MPa. The temperature was increased to 180℃ at a rate of 10℃ / min and the pressure was increased to 45MPa. After reaching the target temperature and pressure, the tube was stabilized for 8 minutes. The temperature and pressure values ​​are shown in Table 1. This process continued until microdroplets of water were formed at the hydrocarbon-water interface. After stabilizing for 8 minutes, the hydrocarbon-water interface and the interior of the hydrocarbon were observed using an optical microscope to see if a large number of droplets had formed.

[0062] Cooling and depressurization: The temperature and pressure in the molten silica capillary were rapidly reduced using a hot and cold stage (CAP.500.Stage) and a constant pressure pump (Corpright 2018 & PLC V4.1). The temperature and pressure were reduced to 24℃ and 5MPa, respectively. After stabilizing for 8 minutes, the presence of a large number of droplets at the hydrocarbon-water interface and inside the hydrocarbon was observed using an optical microscope.

[0063] Table 1 Temperature and pressure values ​​of quartz capillary reaction tubes

[0064] Temperature / °C Pressure / MPa Temperature / °C Pressure / MPa Temperature / °C Pressure / MPa 24 5 56 15 130 34 31.5 5 84 20 145 36 42 8 120 30 155 40 49 10 130 30 180 45

[0065] The image of the deionized water-n-hexadecane interface in the quartz capillary reactor under transmitted light under an optical microscope at the initial temperature and pressure (24℃ / 5MPa) of this embodiment is shown below. Figure 2 As shown, by Figure 2 It can be seen that when the quartz capillary reaction tube is under the initial temperature and pressure conditions of 24℃ / 5MPa, no water microdroplets are formed at the interface between deionized water and n-hexadecane.

[0066] The image of the deionized water-n-hexadecane interface in a quartz capillary reactor under transmitted light under an optical microscope in this embodiment is shown below. Figure 3 As shown, by Figure 3It can be seen that when the temperature and pressure are increased to 180℃ / 45MPa, no large amount of water microdroplets is formed at the interface between deionized water and n-hexadecane in a short time.

[0067] The image of the interface between deionized water and n-hexadecane in the quartz capillary under the condition that the temperature and pressure are rapidly decreased to 24℃ / 5MPa is shown in FIG. 4. Figure 4 As shown in FIG. 4, a large amount of microdroplets is observed at the interface between the "hydrocarbon-water" and inside the hydrocarbon by optical microscopy.

[0068] Figures 2 to 4 The scale in FIG. 4 is 20μm.

[0069] Example 2

[0070] The polyimide coating at a distance of 3cm from the bottom of the fused quartz capillary tube is removed by burning with the outer flame of an alcohol lamp, deionized water is injected into the quartz capillary reaction tube, and a liquid column with a height of 2cm is formed in the capillary reaction tube; the initial temperature of the quartz capillary reaction tube is 23℃, the initial pressure is 4.9MPa, the temperature is increased to 200℃, the pressure is increased to 47MPa, and the other conditions are the same as in Example 1.

[0071] Example 3

[0072] The polyimide coating at a distance of 4cm from the bottom of the fused quartz capillary tube is removed by burning with the outer flame of an alcohol lamp, deionized water is injected into the quartz capillary reaction tube, and a liquid column with a height of 3cm is formed in the capillary reaction tube;

[0073] The initial temperature of the quartz capillary reaction tube is 25℃, the initial pressure is 5.1MPa, the temperature is increased to 170℃, the pressure is increased to 43MPa, and the other conditions are the same as in Example 1.

[0074] The method for preparing water microdroplets in a "hydrocarbon-water" system under high temperature and high pressure conditions of the present application uses a fused quartz capillary tube and a high-pressure valve to store hydrocarbon liquid and water, adjusts the temperature and pressure conditions of the "hydrocarbon-water" system in the quartz capillary tube system, promotes the formation of a large amount of microdroplets near the interface and inside the hydrocarbon, solves the problems of decomposition or property change of other impurities under high temperature conditions, and makes it possible to rapidly prepare water microdroplets in the process of organic-inorganic interaction in the "hydrocarbon-water" system under high temperature conditions. The method of the present application can realize the rapid preparation of water microdroplets and ensure good stability, thereby meeting the application requirements in conventional fields such as nanomaterial synthesis, drug delivery, and catalytic reaction, especially in high-temperature and high-pressure special fields such as oil exploitation, high-temperature and high-pressure catalytic reaction system construction, and geological research simulation of formation environment experiments, filling the gap of water microdroplet manufacturing technology in the "hydrocarbon-water" system, and promoting the technological progress and industrial application development in related fields.

[0075] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A method for preparing water droplets in a hydrocarbon-water system, characterized in that, It includes the following steps: 1) Preparation of quartz capillary reaction tube: Remove the coating at the bottom of the molten quartz capillary tube to serve as the microdroplet observation end; then clean, dry and seal both ends of the molten quartz capillary tube in sequence. The end of the fused silica capillary without the coating removed is fitted into a conical sleeve. The conical sleeve and the fused silica capillary are then bonded together and dried to cure. The end of the fused silica capillary near the conical sleeve is cut off to serve as the sample injection end; 2) Sample injection: Insert a thin capillary syringe filled with water into the bottom of the quartz capillary reaction tube and inject the water; Insert a capillary syringe containing hydrocarbon liquid into a quartz capillary reaction tube until the tip of the capillary syringe contacts the water interface. Inject the hydrocarbon liquid until hydrocarbon liquid overflows from the injection end. The hydrocarbon-water interface is free of impurities and bubbles, and the sample loading is complete. 3) Quartz capillary reaction tube fixation: Connect the sample-loaded quartz capillary reaction tube to the high-pressure needle valve, and then insert it into the hot and cold stage. The microdroplet observation end of the quartz capillary reaction tube is located above the temperature control plate of the hot and cold stage. The quartz capillary reaction tube is fixed with a silver sheet. 4) Droplet preparation: The temperature and pressure in the quartz capillary reaction tube are gradually increased using a heating and cooling stage and a constant pressure pump until water microdroplets are formed at the hydrocarbon-water interface; then the temperature and pressure in the quartz capillary reaction tube are decreased using a heating and cooling stage and a constant pressure pump.

2. The method for preparing water droplets in a hydrocarbon-water system according to claim 1, characterized in that, Step 1) The conical sleeve is composed of a hollow stainless steel tube and a ball valve assembly. The length of the hollow stainless steel tube is 1.8 to 2.2 cm and the inner diameter is 1.8 to 2.2 mm.

3. The method for preparing water droplets in a "hydrocarbon-water" system according to claim 1 or 2, characterized in that, Step 1) The fused silica capillary has a circular cross-section, an inner diameter of 200-400 μm, an outer diameter of 800-1200 μm, and a length of 18-25 cm.

4. The method for preparing water droplets in the "hydrocarbon-water" system according to claim 3, characterized in that, Step 1) The coating removal position is 3-5 cm away from the bottom of the fused silica capillary; the bonding position is 1-2 cm away from the top of the fused silica capillary, and the ball valve assembly end faces outward.

5. The method for preparing water droplets in a hydrocarbon-water system according to claim 3, characterized in that, The drying temperature in step 1) is 58-62℃, the drying and curing temperature is 38-43℃, and the time is 23-24.5h.

6. The method for preparing water droplets in a "hydrocarbon-water" system according to claim 1 or 4, characterized in that, Step 2) The amount of water injected is such that a liquid column of 2-3 cm in height is formed in the quartz capillary reaction tube.

7. The method for preparing water droplets in a hydrocarbon-water system according to claim 6, characterized in that, Step 2) The capillary syringe has a length of ≥20cm and an outer diameter of 150~200μm; the capillary syringe is withdrawn while water is injected, and the capillary syringe is withdrawn while hydrocarbon liquid is injected.

8. The method for preparing water droplets in a "hydrocarbon-water" system according to claim 6, characterized in that, Step 2) The hydrocarbon liquid includes n-hexadecane.

9. The method for preparing water droplets in a "hydrocarbon-water" system according to claim 7 or 8, characterized in that, In step 4), the initial pressure is 4.8–5.2 MPa, the initial temperature is 22–26°C, the temperature is increased to 170–200°C, the pressure is increased to 42–48 MPa, the temperature is decreased to 22–120°C, and the pressure is decreased to 5–30 MPa.

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