Amphiphilic carbon-based nano oil-displacing agent with high emulsification level and preparation method of amphiphilic carbon-based nano oil-displacing agent

Abstract

The invention discloses an amphiphilic carbon-based nano oil displacement agent with a high emulsification level and a preparation method thereof, and belongs to the technical field of emulsification. The carbon-based quantum dots are synthesized by taking various small molecule compounds as raw materials through one-step hydrothermal synthesis, and then functional groups such as hydroxyl and carboxyl of the carbon-based quantum dot material are subjected to post-modification by using alkylamine, sulfanilic diazonium salt and the like, so that the hydrophilic and hydrophobic properties of the carbon-based quantum dot material are directionally regulated and controlled; therefore, the amphiphilic carbon-based nano oil displacement agent with good surface activity is prepared. The method has general adaptability to most of carbon-based quantum dot materials, and the prepared carbon-based nano oil displacement agent shows good interface performance and emulsifying performance as a surfactant. Various prepared carbon-based nano oil displacement agents show good interfacial activity and excellent emulsifying performance, and a water-oil two-phase emulsion system prepared from the carbon-based nano oil displacement agents prepared by the method is dense in emulsion, small in emulsion bubble particle size and very excellent in stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of emulsification, and in particular relates to an amphiphilic carbon-based nano oil-displacing agent with a high emulsification level and a preparation method thereof. Background Art

[0002] In recent years, as oilfield resources have become increasingly depleted and extraction has become increasingly difficult, tertiary oil recovery (TER) technologies, primarily based on chemical flooding, have gradually become the primary means of enhancing oil recovery. Chemical flooding agents, such as polymers and surfactants, suffer from high material consumption, poor resistance to salt, alkali, and high-temperature environments, high chemical losses, and limited flooding effectiveness. Nano-flooding agents offer significant advantages in reducing interfacial tension, modifying reservoir wettability, emulsifying crude oil, and stripping it, offering promising development prospects.

[0003] Carbon-based materials are widely available, and there is great potential for developing low-cost, high-performance carbon-based nano-oil displacement agents through simple modification and group modification. Carbon-based quantum dots have the characteristics of small particle size, large specific surface area, and easy modification, which give them better dispersion and surface properties in solvents. Modification of specific groups on the surface of quantum dots can regulate their hydrophilic and hydrophobic properties. For example, modification with hydrocarbon groups of different carbon chain lengths can improve their hydrophobic properties, modification with benzenesulfonic acid groups can enhance their hydrophilicity, and modification with amphiphilic polymer chains can provide more stable and excellent emulsification properties. Carbon-based quantum dots modified with amphiphilic groups can significantly enhance the interaction in oil-water systems and prepare small droplet Pickering emulsion systems. Nanoparticles can reduce the aggregation of droplets and improve the stability of droplets, which is beneficial for improving oil recovery.

[0004] Carbon dot synthesis technology continues to advance, and low-cost preparation strategies are being optimized and improved. Common carbon dot materials include carbon quantum dots, graphene quantum dots, and carbon polymer quantum dots. Various carbon nanomaterials, after appropriate processing, have the potential to become high-performance nanoscale oil-displacement agents. Combining the small particle size and easy dispersion of carbon dots with the excellent stability of Pickeringr emulsifiers has great potential for developing new, high-performance carbon-based nanoscale oil-displacement agents. Summary of the Invention

[0005] Nanoscale oil-displacement agents offer a promising solution to the limitations of current chemical oil-displacement agents in tertiary oil recovery, including high material consumption, poor salt, alkali, and high-temperature resistance, and high chemical losses. The present invention aims to synthesize carbon-based quantum dot nanomaterials using low-cost raw materials, and to prepare amphiphilic carbon-based nanoscale oil-displacement agents with high emulsification levels.

[0006] This method uses a variety of small molecule compounds as raw materials to hydrothermally synthesize carbon-based quantum dots in a single step. The hydroxyl and carboxyl functional groups of the carbon-based quantum dot materials are then post-modified with alkylamines, p-aminobenzenesulfonic acid diazonium salts, and other methods to selectively regulate their hydrophilic and hydrophobic properties, thereby producing an amphiphilic carbon-based nano-oil-displacing agent with excellent surface activity. This method is universally applicable to the vast majority of carbon-based quantum dot materials, and the resulting carbon-based nano-oil-displacing agent exhibits excellent interfacial and emulsifying properties as a surfactant.

[0007] The preparation method of the amphiphilic carbon-based nano oil-displacing agent with a high emulsification level described in the present invention comprises the following steps: (1) Glucose is added to a sodium hydroxide solution, stirred and dissolved, and then a hydrothermal reaction is carried out; the reaction system is then cooled to room temperature, and after filtering to remove blocky impurities, dilute hydrochloric acid is slowly added to the resulting filtrate to flocculate the carbon dot material, and the precipitate is collected by centrifugation, washed with pure water, and freeze-dried to obtain a hydrophilic powdered carbon quantum dot material prepared using glucose as a raw material; (2) 1,3,6-trinitropyrene was added to a sodium hydroxide solution, ultrasonically dispersed, and then a hydrothermal reaction was carried out; then concentrated hydrochloric acid (mass fraction 36-38%, 12 mol / L) was slowly added to the reaction system cooled to room temperature to flocculate the graphene quantum dot material, and the precipitate was collected by centrifugation, washed with pure water, and freeze-dried to obtain a hydrophilic powdered graphene quantum dot material prepared with 1,3,6-trinitropyrene as the raw material; (3) Add citric acid to water to dissolve, add ethylenediamine and mix evenly, then slowly add sodium hydroxide solution until the reaction system becomes weakly alkaline and then conduct hydrothermal reaction; then slowly add concentrated hydrochloric acid (mass fraction 36-38%, 12 mol / L) to the reaction system cooled to room temperature to flocculate the carbon dot material, collect the precipitate by centrifugation, wash with pure water and freeze-dry to obtain a hydrophilic powdered carbon polymer dot material prepared with citric acid as raw material; (4) Lysine was added to a sodium hydroxide solution and subjected to hydrothermal reaction after ultrasonic dispersion. Then, concentrated hydrochloric acid (mass fraction 36-38%, 12 mol / L) was slowly added dropwise to the reaction system cooled to room temperature to flocculate the carbon dot material. The precipitate was collected by centrifugation, washed with pure water, and freeze-dried to obtain a hydrophilic powdered carbon quantum dot material prepared with lysine as the raw material. (5) Ascorbic acid was added to pure water, ultrasonically dispersed, and then a hydrothermal reaction was carried out; concentrated hydrochloric acid (mass fraction 36-38%, 12 mol / L) was then slowly added dropwise to the reaction system cooled to room temperature to flocculate the carbon dot material, and the precipitate was collected by centrifugation, washed with pure water, and freeze-dried to obtain a hydrophilic powdered carbon quantum dot material prepared with ascorbic acid as the raw material; (6) Chitosan is added to an acetic acid solution, ultrasonically dispersed, and then subjected to a hydrothermal reaction; the reaction system is then cooled to room temperature, large blocks of matter are filtered out with qualitative filter paper, and the resulting filtrate is dialyzed to remove impurities. The liquid in the bag is freeze-dried to obtain a hydrophilic powdered carbon quantum dot material prepared using chitosan as a raw material; (7) The hydrophilic powdered carbon quantum dot material prepared in any one of steps (1) to (6) is added to a PBS buffer solution, and then the catalyst 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) are added, and hexylamine is slowly added dropwise and then dispersed evenly by ultrasonication; the reaction is carried out under water bath conditions, and then the resulting reaction system is cooled to room temperature and transferred to a dialysis bag for dialysis, and the liquid in the bag is freeze-dried to obtain an amphiphilic carbon-based nano oil-displacing agent prepared by modifying the carbon-based quantum dots as precursors.

[0008] The preparation method of the amphiphilic carbon-based nano oil-displacing agent with a high emulsification level described in the present invention comprises the following steps: (a) 1,3,6-trinitropyrene was added to a sodium hydroxide solution, followed by the addition of hexylamine, and then ultrasonically dispersed and subjected to a hydrothermal reaction. After the reaction, the reaction system was cooled to room temperature, dialyzed, and the liquid in the bag was freeze-dried to obtain an amphiphilic carbon-based nano-oil displacement agent prepared by a one-pot method. (b) dissolving p-aminobenzenesulfonic acid in a sodium hydroxide solution, adding sodium nitrite in an ice bath to dissolve and mix uniformly, and then slowly adding concentrated hydrochloric acid dropwise with stirring to obtain a p-aminobenzenesulfonic acid diazonium salt system; (c) adding the amphiphilic carbon-based nano-oil-displacing agent prepared by the one-pot method obtained in step (a) to ethanol to obtain an ethanol dispersion; then slowly dropping the p-aminobenzenesulfonic acid diazonium salt system obtained in step (b) into the ethanol dispersion, stirring the reaction first in an ice bath, then stirring the reaction at room temperature, and after dialysis, freeze-drying the liquid in the bag to obtain an amphiphilic carbon-based nano-oil-displacing agent with optimized performance and a high emulsification level.

[0009] Preferably, in the sodium hydroxide solution of step (1), the concentration of glucose is 30-60 mg / mL, the concentration of sodium hydroxide is 10-15 mg / mL, the hydrothermal reaction temperature is 160-190° C., the hydrothermal reaction time is 5-7 h, and the concentration of dilute hydrochloric acid is 1-2 mol / L; Preferably, in the sodium hydroxide solution of step (2), the concentration of 1,3,6-trinitropyrene is 4-6 mg / mL, the concentration of sodium hydroxide is 7-9 mg / mL, the temperature of the hydrothermal reaction is 190-210° C., and the time of the hydrothermal reaction is 10-13 h; Preferably, in the sodium hydroxide solution of step (3), the concentration of citric acid is 80-120 mg / mL, the molar ratio of ethylenediamine to citric acid is 0.8-1:1, the concentration of the sodium hydroxide solution is 1-2 mol / L, and the pH of the adjustment system is 8-9; the temperature of the hydrothermal reaction is 160-200°C, and the time of the hydrothermal reaction is 4.5-6 hours; Preferably, in the sodium hydroxide solution of step (4), the concentration of lysine is 8-12 mg / mL, and the concentration of sodium hydroxide is 10-14 mg / mL; the temperature of the hydrothermal reaction is 170-200° C., and the time of the hydrothermal reaction is 4-8 h; Preferably, the concentration of ascorbic acid in the water system in step (5) is 40-60 mg / mL, the hydrothermal reaction temperature is 180-200° C., and the reaction time of the hydrothermal reaction is 5-8 h; Preferably, in the sodium hydroxide solution of step (6), the concentration of chitosan is 30-40 mg / mL, the mass concentration of the acetic acid solution is 1-2%; the hydrothermal reaction time is 180-210°C, the hydrothermal reaction time is 10-14 h, and the freeze-drying temperature range is -40°C to -30°C; Preferably, in the PBS buffer solution of step (7), the final concentration of the carbon dot material is 5-10 mg / mL; the concentration of the PBS buffer is 0.15-0.25 mol / L, and the pH is 5.5-5.7; the final concentrations of EDC and NHS are the same, 8-12 mg / mL, and the final concentration of hexylamine is 8-12 mg / mL; the water bath reaction temperature is 50-80°C, and the water bath reaction time is 3-5 h; Preferably, in the sodium hydroxide solution of step (a), the final concentration of 1,3,6-trinitropyrene is 4-6 mg / mL, the final concentration of sodium hydroxide is 7-9 mg / mL, and the final concentration of hexylamine is 8-12 mg / mL; the temperature of the hydrothermal reaction is 180-210° C., and the hydrothermal reaction time is 10-13 h; Preferably, in the sodium hydroxide solution of step (b), the final concentration of sodium hydroxide is 30-40 mg / mL, the final concentration of p-aminobenzenesulfonic acid is 60-80 mg / mL, the temperature of the ice bath is 0-5°C; the final concentration of sodium nitrite is 20-30 mg / mL, the volume ratio of concentrated hydrochloric acid to sodium hydroxide solution is 0.3-0.4:1, and the stirring reaction time after adding concentrated hydrochloric acid is 20-60 minutes; Preferably, in step (c), the concentration of the ethanol dispersion of the amphiphilic carbon-based nano-oil-displacing agent prepared by the one-pot method is 8-12 mg / mL, the volume ratio of the diazonium p-aminobenzenesulfonic acid salt system to the ethanol dispersion is 0.4-0.6:1, the temperature of the ice bath is 0-5°C, and the reaction time of the ice bath is 2-3 hours; the temperature of the room temperature is 20-28°C, and the reaction time of the room temperature is 6-10 hours; Preferably, in steps (1) to (5), hydrochloric acid is slowly added dropwise to adjust the pH of the reaction system to 1-2; after washing with pure water, the pH of the reaction system is 4-5; Preferably, the molecular weight cut-off of the dialysis bag used for dialysis in step (6), step (7), step (a), and step (c) is 500-1000, the dialysis time is 20-30 hours, and the water is changed every 6-10 hours.

[0010] The amphiphilic carbon-based nano oil-displacing agent with a high emulsification level described in the present invention is prepared by the above method.

[0011] The amphiphilic carbon-based nano oil-displacing agent obtained in step (7) and step (c) is added to pure water for ultrasonic dispersion to obtain an amphiphilic carbon-based nano oil-displacing agent dispersion, and the dispersion is then mixed with cyclohexane, toluene, n-octane, etc. at a volume ratio of 1:1, ultrasonically emulsified, and after standing for a period of time, the emulsification rate and the average particle size of the emulsion droplets are measured to detect its amphiphilic emulsification performance; the surface tension of the amphiphilic carbon-based nano oil-displacing agent aqueous dispersion and the interfacial tension after mixing with an organic solvent are measured to detect its surface activity.

[0012] The present invention provides methods for preparing various carbon-based nano-oil-displacing agents using low-cost raw materials such as glucose, 1,3,6-trinitropyrene, citric acid, lysine, ascorbic acid, and chitosan through simple hydrothermal synthesis and post-treatment. The method also provides an effective strategy for regulating the hydrophilic and hydrophobic properties of carbon-based nano-oil-displacing agent materials using alkylamines and diazonium p-aminobenzenesulfonic acid salts. The various carbon-based nano-oil-displacing agents prepared by the present invention exhibit good interfacial activity and excellent emulsification properties. Water-oil two-phase emulsion systems prepared using the carbon-based nano-oil-displacing agents produced by the present invention exhibit dense emulsions, small emulsified bubble size, and excellent stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a transmission electron microscope (TEM) image of the "CQ-nitropyrene" carbon-based nano-oil displacement agent prepared in Example 7; Figure 2 : The infrared absorption spectra of graphene quantum dots and "CQ-nitropyrene" carbon-based nano-oil displacement agent before and after hexylamine modification in Example 7; Figure 3 The emulsification ratio and average emulsion droplet size of the mixed emulsion system of the amphiphilic carbon-based nano oil-displacing agent aqueous dispersion and different organic solvents prepared in Examples 7, 8, and 9; Figure 3 The organic solvent in a is cyclohexane, Figure 3 The organic solvent in b is toluene. Figure 3 The organic solvent in c is n-octane; Figure 4Optical images of the emulsion systems prepared with cyclohexane, toluene, and n-octane respectively, of the dispersion prepared by the "one-pot CQ" amphiphilic carbon-based nano-oil displacement agent; Figure 5 The emulsion droplet states of the dispersion prepared by the amphiphilic carbon-based nano-oil displacement agent "one-pot CQ" and the emulsion system prepared with cyclohexane, toluene, and n-octane were observed under a Leica microscope; Figure 6 This is a diagram showing the effect of the amphiphilic carbon-based nano-oil-displacing agent aqueous dispersion prepared in Examples 7, 8, and 9 on reducing the surface tension of the water system; Figure 7 This is a diagram showing the effect of reducing the interfacial tension of the water / octane system by the carbon-based nano-oil-displacing agent aqueous dispersion prepared in Examples 7, 8, and 9; Figure 8 The dispersion prepared by the amphiphilic carbon-based nano-oil displacement agent "one-pot CQ" was mixed with the gradient HLB oil phase to form an emulsion, and the emulsion droplet state was observed under a Leica microscope; Figure 9 The average droplet size of the emulsion formed by mixing the dispersion prepared by the amphiphilic carbon-based nano-oil displacement agent "one-pot CQ" with the gradient HLB oil phase; Table 1: Mass of cottonseed oil and turpentine required to prepare different HLB values DETAILED DESCRIPTION

[0014] In order to more clearly describe the technical solutions and the technical effects achieved in the present invention, detailed description will be given below in conjunction with specific embodiments. Various raw materials and instruments and equipment used in the present invention can be obtained by normal purchase. Based on the embodiments of the present invention, those skilled in the art directly obtain the embodiments of the present invention without creative activities, and all fall within the scope of protection of the present invention. The present invention will be further described below in conjunction with the accompanying drawings and Examples.

[0015] Example 1: Water-soluble carbon dots (CDOs) were prepared using low-cost glucose as a precursor for carbon-based nano-oil-displacing agents. First, 1.5 g of glucose was added to 30 mL of pure water, stirred to dissolve, and then 0.40 g of sodium hydroxide was added. Next, the system was ultrasonically mixed and transferred to a hydrothermal reactor, where the reaction was incubated at 180°C for 6 h. After cooling to room temperature, the reaction was briefly filtered using standard qualitative filter paper to remove large aggregates. The filtrate was then slowly added dropwise with 2 mL of concentrated hydrochloric acid to flocculate the water-soluble CDO material. Finally, the flocculated CDOs were centrifuged, washed three times with pure water to reduce the acidity, and freeze-dried to obtain a powdered CDO, designated CDO 1.

[0016] Example 2: Graphene quantum dots (1,3,6-trinitropyrene) were prepared as a precursor for a carbon-based nano-oil-displacing agent. First, 150 mg of light yellow 1,3,6-trinitropyrene was added to 30 mL of 8 mg / mL sodium hydroxide solution and ultrasonically dispersed. The mixture was then transferred to a reactor and reacted at 200°C for 12 hours. After the reaction was completed and cooled to room temperature, 1 mL of concentrated hydrochloric acid was added to adjust the pH to acidic. This resulted in flocculation of the prepared graphene quantum dots due to charge neutralization. Finally, the product was centrifuged, washed three times with deionized water, and freeze-dried to obtain the graphene quantum dots.

[0017] Example 3: Water-soluble carbon polymer dots (CPDs) were prepared using low-cost citric acid as a precursor for carbon-based nano-oil displacement agents. First, 2.0 g of citric acid and 0.54 mL of ethylenediamine (molar ratio of 1:0.8) were added to 20 mL of water and mixed thoroughly. Then, 1 mol / L sodium hydroxide solution was slowly added dropwise until the pH reached 8. The reaction mixture was transferred to a polytetrafluoroethylene reactor and reacted at 180°C for 5 hours. Concentrated hydrochloric acid was then slowly added dropwise to the reaction mixture to flocculate the CPDs. Finally, the CPDs were centrifuged, washed three times with pure water, and freeze-dried to obtain the CPDs.

[0018] Example 4: Water-soluble carbon quantum dots were prepared using lysine as a precursor for carbon-based nano-oil displacement agents. First, 300 mg of lysine was added to 30 mL of a 12 mg / mL sodium hydroxide solution and ultrasonically dispersed. The mixture was then transferred to a reactor and reacted at 180°C for 6 hours. After the reaction was completed and cooled to room temperature, 1 mL of concentrated hydrochloric acid was added to adjust the pH to 1-2. This resulted in flocculation of the prepared graphene quantum dots due to charge neutralization. Finally, the product was centrifuged, washed three times with deionized water, and freeze-dried to obtain carbon quantum dots, designated carbon quantum dots 2.

[0019] Example 5: Water-soluble carbon quantum dots (CQDs) were prepared using ascorbic acid as a precursor for carbon-based nano-oil displacement agents. First, 1.5 g of ascorbic acid was weighed and added to 30 mL of pure water. Ultrasonic treatment was performed until completely dissolved. The dissolved ascorbic acid solution was transferred to a hydrothermal reactor and subjected to a hydrothermal reaction at 190°C for 6 h. After the reaction cooled to room temperature, it was briefly filtered using standard qualitative filter paper to remove large aggregates. The filtrate was then slowly added dropwise with 0.5 mL of concentrated hydrochloric acid to flocculate the water-soluble CQD material. Finally, the flocculated CQDs were centrifuged, washed three times with pure water to reduce the acidity, and freeze-dried to obtain CQDs, designated CQD 3.

[0020] Example 6: Water-soluble carbon quantum dots (CQDs) were prepared using chitosan as a precursor for carbon-based nano-oil displacement agents. First, 1 g of chitosan was added to 30 mL of a 2% acetic acid solution. After ultrasonic dispersion, the mixture was transferred to a hydrothermal reactor and reacted at 200°C for 12 hours. After cooling to room temperature, the mixture was briefly filtered using standard qualitative filter paper to remove large aggregates. The filtrate was then dialyzed for 24 hours using a dialysis bag with a molecular weight cutoff of 500. Finally, the mixture was freeze-dried to obtain CQDs, designated CQD 4.

[0021] Example 7: 71.6 mg of Na₂HPO₄·12H₂O and 592.8 mg of Na₂PO₄·2H₂O were weighed and dissolved in 20 mL of water to prepare a PBS buffer system with a pH of 5.6. 0.2 g each of the catalysts 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) were added to the PBS buffer system and stirred to dissolve. 120 mg of any of the hydrophilic carbon dot materials prepared in Examples 1-6 (carbon quantum dots 1-4, graphene quantum dots, carbon polymer dots) was added to the PBS buffer system and ultrasonically dispersed. Stirring was performed at 60°C, 0.2 g of hexylamine was added and the reaction continued for 4 hours. As the reaction proceeded, the hexylamine reacted with the carboxyl groups on the graphene quantum dot precursor in the aqueous solution to form an amide. The hexyl group, acting as a hydrophobic group, enhanced the hydrophobicity of the material. After the reaction, the solution was transferred to a dialysis bag with a molecular weight cut-off of 500 and dialyzed for 24 hours. The liquid in the dialysis bag was freeze-dried to obtain an amphiphilic carbon-based nano-oil displacement agent with carbon dot material as a precursor.

[0022] The carbon dot materials prepared in the above examples 1-6 can all be improved in hydrophobicity by the method of example 7 to prepare an amphiphilic carbon-based nano oil displacement agent with optimized performance (in Figure 3 In the present invention, the amphiphilic carbon-based nano oil-displacing agents prepared by this method are named CQ-glucose, CQ-nitropyrene, CQ-citric acid, CQ-lysine, CQ-ascorbic acid, and CQ-chitosan, respectively). Figure 1 As shown in the figure, the morphology was observed by transmission electron microscopy, and the particle size of the prepared "CQ-nitropyrene" amphiphilic carbon-based nano oil-displacing agent was mainly concentrated in 2~4nm. Figure 2 As shown, infrared absorption spectroscopy was used to detect the structural changes of "CQ-nitropyrene" obtained by modifying graphene quantum dots with hexylamine. -1 The characteristic peak of the C-H bond of hexylamine appeared at , proving that this method can be used to successfully modify carbon-based quantum dot materials with hexylamine.

[0023] Example 8: Graphene quantum dots (GQDs) were prepared using 1,3,6-trinitropyrene as a precursor for a carbon-based nano-oil-displacing agent. First, 150 mg of light yellow 1,3,6-trinitropyrene was added to 30 mL of 8 mg / mL sodium hydroxide solution and ultrasonically dispersed. 0.3 mL of hexylamine was then added, and the mixture was transferred to a reactor and reacted at 200°C for 12 hours. After the reaction was complete and cooled to room temperature, an equal volume of ethanol was added to dissolve the oil-soluble GQDs attached to the inner wall. The mixture was then directly transferred to a dialysis bag with a molecular weight cutoff of 500 for dialysis. The liquid in the bag was freeze-dried to obtain an amphiphilic carbon-based nano-oil-displacing agent, designated "one-pot CQ."

[0024] Example 9: Since the "one-pot CQ" prepared in Example 8 is more lipophilic, the performance of the carbon-based nano oil-displacing agent prepared in Example 8 can be further improved by using a diazonium salt system of p-aminobenzenesulfonic acid, as follows: The product prepared in Example 8 was added with 10 mL of ethanol to prepare a dispersion solution for later use.

[0025] Weigh 0.4g of p-aminobenzenesulfonic acid and 0.2g of sodium hydroxide and dissolve them in 6mL of water. Add 0.16g of sodium nitrite and dissolve thoroughly in an ice bath at 3°C. Continue to slowly add 2mL of concentrated hydrochloric acid dropwise in an ice bath and stir for 30 minutes to obtain the yellow p-aminobenzenesulfonic acid diazonium salt.

[0026] For oil-soluble carbon-based quantum dots, appropriately enhancing their water solubility is essential for enhancing their amphiphilic properties in the preparation of nano-oil-displacing agents. Specifically, 5 mL of yellow diazonium salt of p-aminobenzenesulfonic acid was slowly added dropwise to the graphene quantum dot dispersion under ice-bath conditions and stirred for 2 hours. The reaction was then stirred at room temperature for 8 hours. The system was dialyzed for 24 hours in a dialysis bag with a molecular weight cut-off of 500 and freeze-dried to obtain a carbon-based nano-oil-displacing agent powder with optimized hydrophilic properties, named "One-Pot CQ-Hydrophilic."

[0027] The above-mentioned eight carbon-based nano-oil-displacing agents are as follows: six amphiphilic carbon-based nano-oil-displacing agent powders named CQ-glucose, CQ-nitropyrene, CQ-citric acid, CQ-lysine, CQ-ascorbic acid, and CQ-chitosan (prepared in Example 7); a "one-pot CQ" prepared by a one-pot method of 1,3,6-trinitropyrene and hexylamine (prepared in Example 8); and an amphiphilic carbon-based nano-oil-displacing agent "one-pot CQ-hydrophilic" (prepared in Example 9) obtained by hydrophilic modification of a diazonium salt system of p-aminobenzenesulfonic acid.

[0028] Example 10: The above 8 kinds of amphiphilic carbon-based nano oil-displacing agents were added to water and ultrasonically dispersed to prepare 3mg / mL concentration dispersions. The dispersions were mixed with cyclohexane, toluene, and n-octane in a volume ratio of 1:1, and ultrasonically emulsified for 3 minutes in a probe ultrasonic disperser with a power of 300W. After standing for 3 hours, the emulsification rate was measured and the average particle size of the emulsified bubbles was observed and counted under a microscope. The results were as follows: Figure 3 As shown in ac.

[0029] All eight amphiphilic carbon-based nano-oil-displacing agents successfully prepared stable emulsions with emulsification rates exceeding 60% and particle sizes less than 20 microns in their dispersion / cyclohexane systems. In the dispersion / toluene system, stable emulsions with emulsification rates exceeding 75% and particle sizes less than 15 microns were successfully prepared. In the dispersion / n-octane system, stable emulsions with emulsification rates exceeding 40% and particle sizes less than 25 microns were successfully prepared. The differences between the solvents are related to their viscosity and interaction with the nano-oil-displacing agents. The eight prepared amphiphilic carbon-based nano-oil-displacing agents exhibited varying emulsification performance. Among them, the "one-pot CQ" prepared in Example 8 showed a significantly higher emulsification level and emulsion droplets with a smaller average particle size. Specifically, the emulsification rate of the dispersion liquid / cyclohexane system was 84.3%, and the average droplet particle size was 8.23 ​​μm; the emulsification rate of the dispersion liquid / toluene system was 92.5%, and the average droplet particle size was 3.21 μm; and the emulsification rate of the dispersion liquid / n-octane system was 72.3%, and the average droplet particle size was 12.98 μm. Figure 4 、 Figure 5 The optical photographs of the emulsion system prepared by mixing the dispersion (3 mg / mL) of the amphiphilic carbon-based nano-oil displacement agent "one-pot CQ" with equal volumes of cyclohexane, toluene, and n-octane, and the state diagram of the emulsion droplets observed under a microscope are shown. The emulsion has a high emulsification rate, dense droplets and relatively uniform particle size.

[0030] The surface tension of 8 kinds of amphiphilic carbon-based nano oil-displacing agents at a concentration of 3 mg / mL was measured using a surface tension meter. Figure 5 As shown, it is significantly demonstrated that the carbon-based nano oil-displacing agent dispersion / cyclohexane system can significantly reduce the surface tension of the water system, among which the "one-pot CQ" prepared in Example 8 can reduce the surface tension of water from 71.8 mN / m to 28.5 mN / m.

[0031] The interfacial tension between 3 mg / mL dispersions of 8 kinds of amphiphilic carbon-based nano-oil displacement agents and n-octane was measured using a surface tension meter. The results are as follows: Figure 6 As shown in the figure, the carbon-based nano oil displacement agent significantly reduces the interfacial tension between water and n-octane. The extent of reducing the interfacial tension varies due to the limitations of raw materials and preparation methods. Among them, the "one-pot CQ" prepared in Example 8 can reduce the interfacial tension of the two phases to an excellent 1.5 mN / m.

[0032] The HLB value of the "one-pot CQ" amphiphilic carbon-based nano-oil-displacing agent was determined using a traditional emulsification method. First, the "one-pot CQ" amphiphilic carbon-based nano-oil-displacing agent prepared in Example 8 was dispersed in an aqueous solution to prepare a 3 mg / mL dispersion. Cottonseed oil and turpentine oil of varying weights were mixed according to Table 1 to prepare a mixed oil phase with a gradient HLB value. The mixed oil phase and the dispersion were mixed in a mass ratio of 1:4, ultrasonically applied to form an emulsion, and the emulsion was allowed to stand for 2 days. Figure 8 、 Figure 9 This is an emulsion system formed by mixing a dispersion with oils of different HLB values. The emulsion droplet state and average particle size were observed under a Leica microscope. The emulsion with an HLB value of 13 formed the smallest particle size, indicating that the prepared "one-pot CQ" amphiphilic carbon-based nano-oil displacement agent with a high emulsification level has an HLB of 13.

Claims

1. A method for preparing an amphiphilic carbon-based nano oil-displacing agent with a high emulsification level, characterized in that: The steps are as follows: (1) Glucose is added to a sodium hydroxide solution, stirred and dissolved, and then a hydrothermal reaction is carried out; the reaction system is then cooled to room temperature, and after filtering to remove blocky impurities, dilute hydrochloric acid is slowly added to the resulting filtrate to flocculate the carbon dot material, and the precipitate is collected by centrifugation, washed with pure water, and freeze-dried to obtain a powdered carbon quantum dot material prepared using glucose as a raw material; (2) 1,3,6-trinitropyrene is added to a sodium hydroxide solution, ultrasonically dispersed, and then a hydrothermal reaction is carried out; then concentrated hydrochloric acid is slowly added to the reaction system cooled to room temperature to flocculate the graphene quantum dot material, the precipitate is collected by centrifugation, washed with pure water, and freeze-dried to obtain a powdered graphene quantum dot material prepared using 1,3,6-trinitropyrene as a raw material; (3) Add citric acid to water and dissolve it, add ethylenediamine and mix well, then slowly add sodium hydroxide solution until the reaction system becomes weakly alkaline and then conduct hydrothermal reaction; then slowly add concentrated hydrochloric acid to the reaction system cooled to room temperature to flocculate the carbon dot material, collect the precipitate by centrifugation, wash with pure water and freeze-dry to obtain a powdered carbon polymer dot material prepared with citric acid as raw material; (4) Lysine is added to a sodium hydroxide solution, ultrasonically dispersed, and then hydrothermally reacted; concentrated hydrochloric acid is then slowly added to the reaction system cooled to room temperature to flocculate the carbon dot material, and the precipitate is collected by centrifugation, washed with pure water, and freeze-dried to obtain a powdered carbon quantum dot material prepared using lysine as the raw material; (5) Ascorbic acid is added to pure water, ultrasonically dispersed, and then hydrothermally reacted; concentrated hydrochloric acid is then slowly added to the reaction system cooled to room temperature to flocculate the carbon dot material, and the precipitate is collected by centrifugation, washed with pure water, and freeze-dried to obtain a powdered carbon quantum dot material prepared using ascorbic acid as a raw material; (6) Chitosan was added to an acetic acid solution, ultrasonically dispersed, and then subjected to a hydrothermal reaction; the reaction system was then cooled to room temperature, large blocks of matter were filtered out with qualitative filter paper, and the resulting filtrate was dialyzed to remove impurities. The liquid in the bag was freeze-dried to obtain a carbon quantum dot material prepared using chitosan as a raw material; (7) The hydrophilic carbon-based quantum dot material prepared in any one of steps (1) to (6) is added to a PBS buffer solution, and then the catalyst 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide are added, and hexylamine is slowly added dropwise and then ultrasonically dispersed uniformly; the reaction is carried out under water bath conditions, and then the resulting reaction system is cooled to room temperature and transferred to a dialysis bag for dialysis, and the liquid in the bag is freeze-dried to obtain an amphiphilic carbon-based nano oil-displacing agent with a high emulsification level prepared by modifying the carbon-based quantum dots as precursors.

2. The method for preparing an amphiphilic carbon-based nano oil-displacing agent with a high emulsification level according to claim 1, wherein: In the sodium hydroxide solution of step (1), the concentration of glucose is 30~60 mg / mL, the concentration of sodium hydroxide is 10~15 mg / mL, the hydrothermal reaction temperature is 160~190°C, the hydrothermal reaction time is 5~7h, and the concentration of dilute hydrochloric acid is 1~2 mol / L; in the sodium hydroxide solution of step (2), the concentration of 1,3,6-trinitropyrene is 4~6 mg / mL, the concentration of sodium hydroxide is 7~9 mg / mL, the hydrothermal reaction temperature is 190~210°C, and the hydrothermal reaction time is 10~13h; the mass fraction of concentrated hydrochloric acid is 36~38%; in the sodium hydroxide solution of step (3), the concentration of citric acid is 80~120 mg / mL, the molar ratio of ethylenediamine to citric acid is 0.8~1:1, the concentration of sodium hydroxide solution is 1~2 mol / L, and the pH of the adjustment system is 8~9; the hydrothermal reaction temperature is 160~200°C, the water The thermal reaction time is 4.5~6h; the mass fraction of concentrated hydrochloric acid is 36~38%; in the sodium hydroxide solution of step (4), the concentration of lysine is 8~12mg / mL, and the concentration of sodium hydroxide is 10~14mg / mL; the temperature of the hydrothermal reaction is 170~200℃, and the hydrothermal reaction time is 4~8h; the mass fraction of concentrated hydrochloric acid is 36~38%; the concentration of ascorbic acid in the water system of step (5) is 40~60mg / mL, the hydrothermal reaction temperature is 180~200℃, and the reaction time of the hydrothermal reaction is 5~8h; the mass fraction of concentrated hydrochloric acid is 36~38%; in the sodium hydroxide solution of step (6), the concentration of chitosan is 30~40mg / mL, and the mass concentration of the acetic acid solution is 1~2%; the hydrothermal reaction time is 180~210℃, the hydrothermal reaction time is 10~14h, and the freeze-drying temperature range is -40℃~-30℃.

3. The method for preparing an amphiphilic carbon-based nano oil-displacing agent with a high emulsification level according to claim 1, wherein: In the PBS buffer solution of step (7), the final concentration of the carbon dot material is 5-10 mg / mL; the concentration of the PBS buffer is 0.15-0.25 mol / L, and the pH is 5.5-5.7; the final concentrations of EDC and NHS are the same, 8-12 mg / mL, and the final concentration of hexylamine is 8-12 mg / mL; the water bath reaction temperature is 50-80°C, and the water bath reaction time is 3-5 h.

4. The method for preparing an amphiphilic carbon-based nano oil-displacing agent with a high emulsification level according to claim 1, wherein: In steps (1) to (5), hydrochloric acid is slowly added dropwise to adjust the pH of the reaction system to 1-2; after washing with pure water, the pH of the reaction system is 4-5.

5. The method for preparing an amphiphilic carbon-based nano oil-displacing agent with a high emulsification level according to claim 1, wherein: In step (6) and step (7), the molecular weight cut-off of the dialysis bag used for dialysis is 500-1000, the dialysis time is 20-30 hours, and the water is changed every 6-10 hours.

6. An amphiphilic carbon-based nano oil-displacing agent with high emulsification level, characterized by: The invention is prepared by the preparation method according to any one of claims 1 to 5.

7. A method for preparing an amphiphilic carbon-based nano oil-displacing agent with a high emulsification level, characterized in that: The steps are as follows: (a) 1,3,6-trinitropyrene was added to a sodium hydroxide solution, followed by the addition of hexylamine, and then ultrasonically dispersed and subjected to a hydrothermal reaction. After the reaction, the reaction system was cooled to room temperature, dialyzed, and the liquid in the bag was freeze-dried to obtain an amphiphilic carbon-based nano-oil displacement agent prepared by a one-pot method. (b) dissolving p-aminobenzenesulfonic acid in a sodium hydroxide solution, adding sodium nitrite in an ice bath to dissolve and mix uniformly, and then slowly adding concentrated hydrochloric acid dropwise with stirring to obtain a p-aminobenzenesulfonic acid diazonium salt system; (c) adding the amphiphilic carbon-based nano-oil-displacing agent prepared by the one-pot method obtained in step (a) to ethanol to obtain an ethanol dispersion; then slowly dropping the p-aminobenzenesulfonic acid diazonium salt system obtained in step (c) into the ethanol dispersion, stirring the reaction first in an ice bath, then stirring the reaction at room temperature, and after dialysis, freeze-drying the liquid in the bag to obtain an amphiphilic carbon-based nano-oil-displacing agent with optimized performance and a high emulsification level.

8. The method for preparing an amphiphilic carbon-based nano oil-displacing agent with a high emulsification level according to claim 7, wherein: In the sodium hydroxide solution of step (a), the final concentration of 1,3,6-trinitropyrene is 4-6 mg / mL, the final concentration of sodium hydroxide is 7-9 mg / mL, and the final concentration of hexylamine is 8-12 mg / mL; the temperature of the hydrothermal reaction is 180-210°C, and the hydrothermal reaction time is 10-13 h; in the sodium hydroxide solution of step (b), the final concentration of sodium hydroxide is 30-40 mg / mL, the final concentration of p-aminobenzenesulfonic acid is 60-80 mg / mL, and the temperature of the ice bath is 0-5°C; the final concentration of sodium nitrite is 2 0~30 mg / mL, the volume ratio of concentrated hydrochloric acid to sodium hydroxide solution is 0.3~0.4:1, and the stirring reaction time after adding concentrated hydrochloric acid is 20~60 minutes; in step (c), the concentration of the ethanol dispersion of the amphiphilic carbon-based nano oil-displacing agent prepared by the one-pot method is 8~12 mg / mL, the volume ratio of the diazonium p-aminobenzenesulfonic acid system to the ethanol dispersion is 0.4~0.6:1, the temperature of the ice bath is 0~5°C, and the reaction time of the ice bath is 2~3h; the temperature of the room temperature is 20~28°C, and the reaction time of the room temperature is 6~10h.

9. The method for preparing an amphiphilic carbon-based nano oil-displacing agent with a high emulsification level according to claim 7, wherein: In step (a) and step (c), the molecular weight cut-off of the dialysis bag used for dialysis is 500-1000, the dialysis time is 20-30 hours, and the water is changed every 6-10 hours.

10. An amphiphilic carbon-based nano oil-displacing agent with a high emulsification level, characterized by: The compound is prepared by the preparation method according to any one of claims 7 to 9.

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