Amphiphilic carbon-based nano-displacement oil and method of making same with high emulsification level

Abstract

The application discloses amphiphilic carbon-based nano oil-displacing agent with high emulsification level and a preparation method thereof, and belongs to the technical field of emulsification.The carbon-based quantum dots are prepared by one-step hydrothermal synthesis with a plurality of small molecular compounds as raw materials, and the hydroxyl group, carboxyl group and other functional groups of the carbon-based quantum dot material are post-modified by alkylamine, p-aminobenzenesulfonic acid-based diazonium salt and the like to direct control the hydrophilic and hydrophobic properties, so that the amphiphilic carbon-based nano oil-displacing agent with good surface activity is prepared.The method has universal adaptability to most carbon-based quantum dot materials, and the prepared carbon-based nano oil-displacing agent as a kind of surfactant shows good interfacial performance and emulsification performance.The plurality of carbon-based nano oil-displacing agents prepared by the application show good interfacial activity and excellent emulsification performance, and the water-oil two-phase emulsion system prepared by the carbon-based nano oil-displacing agent prepared by the application has dense emulsion, small emulsion bubble particle size and very excellent stability.

Description

Technical Field

[0001] This invention belongs to the field of emulsification technology, specifically relating to an amphiphilic carbon-based nano-oil displacement agent with high emulsification level and its preparation method. Background Technology

[0002] In recent years, with the depletion of oilfield resources and the increasing difficulty of extraction, tertiary oil recovery technology, primarily using chemical flooding, has gradually become the main means of improving oil recovery rates. However, chemical flooding agents such as polymers and surfactants suffer from drawbacks including high material consumption, poor resistance to salt, alkali, and high temperatures, high chemical loss, and limited oil displacement effects. Nano-flooding agents, on the other hand, demonstrate significant advantages in reducing interfacial tension, altering reservoir wettability, emulsifying crude oil, and stripping crude oil, showing promising development prospects.

[0003] Carbon-based materials are widely available, and through simple modification and group modification, there is great potential to develop low-cost, high-performance carbon-based nano-oil displacement agents. Carbon-based quantum dots (QDs) possess characteristics such as small particle size, large specific surface area, and ease of modification, which endow them with superior 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 hydrophobicity, modification with benzenesulfonic acid groups can enhance their hydrophilicity, and modification with amphiphilic polymer chains can provide more stable and superior emulsifying properties. Amphiphilic modification of carbon-based quantum dots can significantly enhance their interaction in oil-water systems. In the preparation of Pickering emulsion systems with small droplets, nanoparticles can reduce droplet coagulation and improve droplet stability, which is beneficial for improving oil recovery.

[0004] Carbon dot synthesis technology continues to develop, and low-cost preparation strategies are constantly being optimized and improved. Common carbon dot materials mainly include carbon quantum dots, graphene quantum dots, and carbon polymer quantum dots. Different types of carbon nanomaterials, after appropriate processing, hold promise as nano-oil displacement agents with excellent performance. Combining the small particle size and easy dispersibility of carbon dots with the excellent stability of Pickeringer emulsifiers to develop novel high-performance carbon-based nano-oil displacement agents has a very broad development prospect. Summary of the Invention

[0005] To address the limitations of current chemical flooding agents used in tertiary oil recovery processes, such as high material consumption, poor resistance to salt, alkali, and high temperatures, and high chemical loss, nano-flooding agents offer a promising solution. The purpose of this invention is to provide a method for synthesizing carbon-based quantum dot nanomaterials from low-cost raw materials and using these materials to prepare amphiphilic carbon-based nano-flooding agents with high emulsification levels.

[0006] This invention synthesizes carbon-based quantum dots in a one-step hydrothermal process using various small molecule compounds as raw materials. Then, by post-modifying the hydroxyl and carboxyl functional groups of the carbon-based quantum dot materials with alkylamines and diazonium salts of p-aminobenzenesulfonic acid, their hydrophilic and hydrophobic properties are directionally regulated, thereby preparing an amphiphilic carbon-based nano-oil displacement agent with good surface activity. This method has broad applicability to most carbon-based quantum dot materials, and the prepared carbon-based nano-oil displacement agent, as a surfactant, exhibits excellent interfacial and emulsifying properties.

[0007] The preparation method of the amphiphilic carbon-based nano-oil displacement agent with high emulsification level according to the present invention comprises the following steps:

[0008] (1) Add glucose to sodium hydroxide solution, stir to dissolve and carry out hydrothermal reaction; then cool the reaction system to room temperature, filter to remove blocky impurities and slowly add dilute hydrochloric acid to the obtained filtrate to flocculate the carbon dot material, collect the precipitate by centrifugation, wash with pure water and freeze dry to obtain hydrophilic powdered carbon quantum dot material prepared from glucose.

[0009] (2) 1,3,6-trinitropyrene was added to sodium hydroxide solution, ultrasonically dispersed, and then subjected to hydrothermal reaction; then concentrated hydrochloric acid (mass fraction 36~38%, 12mol / L) was slowly added dropwise to the reaction system cooled to room temperature to cause the graphene quantum dot material to flocculate, the precipitate was collected by centrifugation, washed with pure water and freeze-dried to obtain hydrophilic powdered graphene quantum dot material prepared from 1,3,6-trinitropyrene;

[0010] (3) Add citric acid to water to dissolve, add ethylenediamine and mix well, then slowly add sodium hydroxide solution until the reaction system is weakly alkaline and carry out hydrothermal reaction; then slowly add concentrated hydrochloric acid (mass fraction 36~38%, 12mol / L) to the reaction system cooled to room temperature to make the carbon dot material flocculate, centrifuge to collect the precipitate, wash with pure water and freeze dry to obtain hydrophilic powdered carbon polymer dot material prepared from citric acid;

[0011] (4) Lysine was added to sodium hydroxide solution, ultrasonically dispersed and then subjected to hydrothermal reaction; then concentrated hydrochloric acid (mass fraction 36~38%, 12mol / L) was slowly added dropwise to the reaction system cooled to room temperature to cause the carbon dot material to flocculate, the precipitate was collected by centrifugation, washed with pure water and freeze-dried to obtain hydrophilic powdered carbon quantum dot material prepared from lysine.

[0012] (5) Add ascorbic acid to pure water, disperse it by ultrasonication and carry out hydrothermal reaction; then slowly add concentrated hydrochloric acid (mass fraction 36~38%, 12mol / L) to the reaction system cooled to room temperature to make the carbon dot material flocculate, collect the precipitate by centrifugation, wash with pure water and freeze dry to obtain hydrophilic powdered carbon quantum dot material prepared from ascorbic acid.

[0013] (6) Chitosan was added to acetic acid solution, ultrasonically dispersed and then subjected to hydrothermal reaction; the reaction system was then cooled to room temperature, large pieces of material were filtered out with qualitative filter paper, the filtrate was dialyzed to remove impurities, and the liquid in the bag was freeze-dried to obtain hydrophilic powdered carbon quantum dot material prepared from chitosan.

[0014] (7) Add the hydrophilic powdered carbon quantum dot material prepared in any of steps (1) to (6) to a PBS buffer solution, then add the catalysts 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS), slowly add hexylamine and then ultrasonically disperse it evenly; react under water bath conditions, then cool the resulting reaction system to room temperature and transfer it to a dialysis bag for dialysis, freeze-dry the liquid in the bag to obtain the amphiphilic carbon-based nano oil displacement agent prepared by modifying carbon-based quantum dots as a precursor.

[0015] The preparation method of the amphiphilic carbon-based nano-oil displacement agent with high emulsification level according to the present invention comprises the following steps:

[0016] (a) 1,3,6-trinitropyrene was added to sodium hydroxide solution, followed by hexylamine. After ultrasonic dispersion, a hydrothermal reaction was carried out. After the reaction was completed, 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 one-pot method.

[0017] (b) Dissolve p-aminobenzenesulfonic acid in sodium hydroxide solution, add sodium nitrite under ice bath conditions to dissolve and mix evenly, and then slowly add concentrated hydrochloric acid while stirring to obtain the p-aminobenzenesulfonic acid diazonium salt system;

[0018] (c) The amphiphilic carbon-based nano-oil displacement agent prepared by one-pot method in step (a) is added to ethanol to obtain an ethanol dispersion; then the p-aminobenzenesulfonic acid diazonium salt system obtained in step (b) is slowly added dropwise to the ethanol dispersion. The reaction is first stirred in an ice bath, and then stirred at room temperature. After dialysis, the liquid in the bag is freeze-dried to obtain an amphiphilic carbon-based nano-oil displacement agent with optimized performance and high emulsification level.

[0019] Preferably, in the sodium hydroxide solution of step (1), the concentration of glucose is 30~60mg / mL, the concentration of sodium hydroxide is 10~15mg / mL, the hydrothermal reaction temperature is 160~190℃, the hydrothermal reaction time is 5~7h, and the concentration of dilute hydrochloric acid is 1~2mol / L.

[0020] 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℃, and the time of the hydrothermal reaction is 10-13 h.

[0021] Preferably, in step (3), the concentration of citric acid in the sodium hydroxide solution 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, the pH of the system is adjusted to 8~9, the temperature of the hydrothermal reaction is 160~200℃, and the time of the hydrothermal reaction is 4.5~6h.

[0022] 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℃ and the time of the hydrothermal reaction is 4~8h.

[0023] Preferably, in step (5), the concentration of ascorbic acid in the aqueous system is 40~60 mg / mL, the hydrothermal reaction temperature is 180~200℃, and the hydrothermal reaction time is 5~8 h;

[0024] Preferably, in step (6), the concentration of chitosan in the sodium hydroxide solution is 30~40 mg / mL, the mass concentration of 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℃.

[0025] Preferably, in step (7), the final concentration of carbon dot material in the PBS buffer solution is 5~10 mg / mL; the concentration of 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℃, and the water bath reaction time is 3~5 h;

[0026] 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 hydrothermal reaction temperature is 180-210°C, and the hydrothermal reaction time is 10-13 h.

[0027] Preferably, in step (b), the final concentration of sodium hydroxide in the sodium hydroxide solution 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.

[0028] Preferably, in step (c), the concentration of the ethanol dispersion of the amphiphilic carbon-based nano-oil displacement agent prepared by the one-pot method is 8~12 mg / mL, the volume ratio of the p-aminobenzenesulfonic acid diazonium salt system to the ethanol dispersion is 0.4~0.6:1, the ice bath temperature is 0~5℃, and the ice bath reaction time is 2~3 h; the room temperature is 20~28℃, and the room temperature reaction time is 6~10 h.

[0029] Preferably, in steps (1) to (5), hydrochloric acid is slowly added dropwise to adjust the pH of the reaction system to 1 to 2; after washing with pure water, the pH of the reaction system is 4 to 5.

[0030] Preferably, the dialysis bags used in steps (6), (7), (a), and (c) have a molecular weight cutoff of 500-1000, the dialysis time is 20-30 hours, and the water is changed every 6-10 hours.

[0031] The amphiphilic carbon-based nano-oil displacement agent with high emulsification level described in this invention is prepared by the above method.

[0032] The amphiphilic carbon-based nano-oil displacement agent obtained in steps (7) and (c) was added to pure water and ultrasonically dispersed to obtain an amphiphilic carbon-based nano-oil displacement agent dispersion. The dispersion was then mixed with cyclohexane, toluene, n-octane, etc., at a volume ratio of 1:1, and ultrasonically emulsified. After standing for a period of time, the emulsification rate and the average particle size of the emulsion droplets were measured to detect its amphiphilic emulsification performance. The surface tension of the aqueous dispersion of the amphiphilic carbon-based nano-oil displacement agent and the interfacial tension after mixing with organic solvents were measured to detect its surface activity.

[0033] This invention provides a method for preparing various carbon-based nano-oil displacement 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. It also provides an effective strategy for controlling the hydrophilic and hydrophobic properties of the carbon-based nano-oil displacement agent materials using alkylamines and diazonium salts of p-aminobenzenesulfonic acid. The various carbon-based nano-oil displacement agents prepared by this invention exhibit good interfacial activity and excellent emulsification properties. Water-oil two-phase emulsion systems prepared using the carbon-based nano-oil displacement agents of this invention have dense emulsions, small emulsion bubble particle sizes, and excellent stability. Attached Figure Description

[0034] Figure 1 Transmission electron microscope (TEM) image of the “CQ-nitropyrene” carbon-based nano-oil displacement agent prepared in Example 7;

[0035] 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;

[0036] Figure 3 Emulsification rate and average emulsion droplet size of the mixed emulsion systems of the amphiphilic carbon-based nano-oil displacement agent aqueous dispersions prepared in Examples 7, 8, and 9 with different organic solvents; Figure 3 The organic solvent in 'a' is cyclohexane. Figure 3 The organic solvent in component b is toluene. Figure 3 The organic solvent in c is n-octane;

[0037] Figure 4 Optical images of the dispersions of the amphiphilic carbon-based nano-oil displacement agent prepared by the "one-pot CQ" method and the emulsion systems prepared by cyclohexane, toluene, and n-octane, respectively.

[0038] Figure 5 The state of the emulsion droplets observed under a Leica microscope in the dispersion prepared by the "one-pot CQ" method for amphiphilic carbon-based nano-oil displacement agent and the emulsion systems prepared by cyclohexane, toluene, and n-octane, respectively.

[0039] Figure 6 The effect of the amphiphilic carbon-based nano-oil displacement agent aqueous dispersions prepared in Examples 7, 8, and 9 on reducing the surface tension of the aqueous system is shown in the figure.

[0040] Figure 7 The graph shows the effect of the carbon-based nano-oil displacement agent aqueous dispersions prepared in Examples 7, 8, and 9 on reducing the interfacial tension of the water / octane system.

[0041] Figure 8 The state of the emulsion droplets observed under a Leica microscope after mixing the dispersion of the amphiphilic carbon-based nano-oil displacement agent prepared by the "one-pot CQ" method with a gradient HLB oil phase to form an emulsion.

[0042] Figure 9 Average droplet size diagram of the emulsion formed by mixing the dispersion of the amphiphilic carbon-based nano-oil displacement agent prepared by the "one-pot CQ" method with the gradient HLB oil phase.

[0043] Table 1: Required Mass of Cottonseed Oil and Turpentine Oil for Different HLB Value Gradients

[0044] Detailed Implementation

[0045] To more clearly describe the technical solution and its achieved effects, a detailed description will be provided below with reference to specific embodiments. All raw materials and equipment used in this invention can be obtained through normal purchase. Based on the embodiments of this invention, those skilled in the art who directly obtain the embodiments of this invention without creative activity are all within the protection scope of this invention. The invention will be further described below with reference to the accompanying drawings and embodiments.

[0046] Example 1:

[0047] Water-soluble carbon dots were prepared using low-cost glucose as a raw material as a precursor for the preparation of carbon-based nano-oil displacement agents. First, 1.5 g of glucose was added to 30 mL of pure water and stirred until dissolved. Then, 0.40 g of sodium hydroxide was added. Next, the system was ultrasonically mixed and transferred to a hydrothermal reactor, where it was reacted at 180 °C for 6 h. After the reaction cooled to room temperature, large pieces were removed by simple filtration with ordinary qualitative filter paper. Then, 2 mL of concentrated hydrochloric acid was slowly added dropwise to the filtrate to flocculate the water-soluble carbon dot material. Finally, the flocculated carbon quantum dots were centrifuged, washed three times with pure water to reduce acidity, and freeze-dried to obtain powdered carbon quantum dots, named carbon quantum dot 1.

[0048] Example 2:

[0049] A precursor for preparing carbon-based nano-oil displacement agents was generated using 1,3,6-trinitropyrene as a raw material to prepare graphene quantum dot materials. 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 solution was then transferred to a reaction vessel and reacted at 200 °C for 12 h. After the reaction was completed and cooled to room temperature, 1 mL of concentrated hydrochloric acid was added to adjust the pH to acidic. The prepared graphene quantum dot materials flocculated due to charge neutralization. Finally, the product was centrifuged, washed three times with deionized water, and freeze-dried to obtain graphene quantum dots.

[0050] Example 3:

[0051] Water-soluble carbon polymer dots were prepared using low-cost citric acid as a raw material as a precursor for the preparation of carbon-based nano-oil displacement agents. First, 2.0 g of citric acid and 0.54 mL of ethylenediamine (molar ratio 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 of the system reached 8. The system was then transferred to a polytetrafluoroethylene reactor and reacted at 180 °C for 5 h. Afterward, concentrated hydrochloric acid was slowly added dropwise to the reaction system until the carbon dots flocculated. Finally, the carbon polymer dots were centrifuged, washed three times with pure water, and freeze-dried to obtain the carbon polymer dots.

[0052] Example 4:

[0053] Water-soluble carbon quantum dots were prepared using lysine as a raw material as a precursor for the preparation of 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 reaction vessel and reacted at 180 °C for 6 h. 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. The prepared graphene quantum dot material flocculated due to charge neutralization. Finally, the product was centrifuged, washed three times with deionized water, and freeze-dried to obtain carbon quantum dots, named carbon quantum dot 2.

[0054] Example 5:

[0055] Water-soluble carbon quantum dots were prepared using ascorbic acid as a raw material as a precursor for the preparation of carbon-based nano-oil displacement agents. First, 1.5 g of ascorbic acid was weighed and added to 30 mL of pure water, and sonicated until completely dissolved. The dissolved ascorbic acid solution was transferred to a hydrothermal reactor and reacted at 190 °C for 6 h. After the reaction cooled to room temperature, large pieces were removed by simple filtration with ordinary qualitative filter paper. Then, 0.5 mL of concentrated hydrochloric acid was slowly added dropwise to flocculate the water-soluble carbon quantum dots. Finally, the flocculated carbon quantum dots were centrifuged, washed three times with pure water to reduce acidity, and freeze-dried to obtain carbon quantum dots, named carbon quantum dot 3.

[0056] Example 6:

[0057] Water-soluble carbon quantum dots were prepared from chitosan as a precursor for the preparation of carbon-based nano-oil displacement agents. First, 1 g of chitosan was added to 30 mL of a 2% (w / w) acetic acid solution and ultrasonically dispersed. The system was then transferred to a hydrothermal reactor and reacted at 200 °C for 12 h. After cooling to room temperature, large particles were removed by simple filtration with ordinary qualitative filter paper. The filtrate was then dialyzed through a dialysis bag with a molecular weight cutoff of 500 for 24 h. Finally, the filtrate was freeze-dried to obtain carbon quantum dots, named carbon quantum dot 4.

[0058] Example 7:

[0059] Weigh 71.6 mg of Na₂HPO₄·12H₂O and 592.8 mg of NaH₂PO₄·2H₂O and dissolve them in 20 mL of water to prepare a PBS buffer system with pH=5.6. Add 0.2 g each of the catalysts 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) to the PBS buffer system and stir to dissolve. Weigh 120 mg of any of the hydrophilic carbon dot materials (carbon quantum dots 1-4, graphene quantum dots, carbon polymer dots) prepared in Examples 1-6 and add them to the PBS buffer system. Disperse by sonication and stir at 60 °C. Add 0.2 g of hexylamine and continue the reaction for 4 h. As the reaction proceeds, hexylamine will react with the carboxyl groups on the graphene quantum dot precursor in the aqueous system to form an amide. The hexyl group, as a hydrophobic group, improves the hydrophobicity of the material. After the reaction was completed, the mixture was transferred to a dialysis bag with a molecular weight cutoff of 500 and dialyzed for 24 hours. The liquid in the dialysis bag was then freeze-dried to obtain an amphiphilic carbon-based nano-oil displacement agent with carbon dot material as a precursor.

[0060] The carbon dot materials prepared in Examples 1-6 above can all have their hydrophobic properties improved by the method in Example 7, thus preparing an optimized amphiphilic carbon-based nano-oil displacement agent (in... Figure 3 In this study, the amphiphilic carbon-based nano-oil displacement agents prepared by this method were named CQ-glucose, CQ-nitropyrene, CQ-citric acid, CQ-lysine, CQ-ascorbic acid, and CQ-chitosan, respectively. Figure 1 As shown, the morphology of the prepared "CQ-nitropyrene" amphiphilic carbon-based nano-oil displacement agent was observed using transmission electron microscopy. The particle size was mainly concentrated in the range of 2-4 nm. Figure 2 As shown, the structural changes of "CQ-nitropyrene" obtained by modifying graphene quantum dots with hexylamine were detected using infrared absorption spectroscopy, with values ​​at 2862, 2931, and 2958 cm⁻¹. -1 The presence of characteristic peaks of hexylamine CH bonds at the point demonstrates that this method can successfully modify carbon-based quantum dot materials with hexylamine.

[0061] Example 8:

[0062] Graphene quantum dot materials were prepared using 1,3,6-trinitropyrene as a raw material to serve as precursors for carbon-based nano-oil displacement agents. First, 150 mg of light yellow 1,3,6-trinitropyrene was added to 30 mL of an 8 mg / mL sodium hydroxide solution and ultrasonically dispersed. Then, 0.3 mL of hexylamine was added, and the system was transferred to a reaction vessel and reacted at 200 °C for 12 h. After the reaction was completed and cooled to room temperature, an equal volume of ethanol was added to dissolve the oil-soluble carbon dots adhering to the inner wall. The system was then directly transferred to a dialysis bag with a molecular weight cutoff of 500 for dialyzing. The liquid in the bag was freeze-dried to obtain an amphiphilic carbon-based nano-oil displacement agent, named "One-Pot CQ".

[0063] Example 9:

[0064] Since the "one-pot CQ" prepared in Example 8 is more lipophilic, the performance of the carbon-based nano-oil displacement agent prepared in Example 8 can be further improved by using a p-aminobenzenesulfonic acid diazonium salt system, as specifically implemented below:

[0065] The solution prepared in Example 8 was added to 10 mL of ethanol to prepare a dispersion for later use.

[0066] Weigh out 0.4 g of p-aminobenzenesulfonic acid and 0.2 g of sodium hydroxide and dissolve them in 6 mL of water. Under ice bath conditions at 3°C, add 0.16 g of sodium nitrite and mix thoroughly. Continue to add 2 mL of concentrated hydrochloric acid dropwise under ice bath conditions, stirring for 30 minutes, finally obtaining a yellow diazonium salt system of p-aminobenzenesulfonic acid.

[0067] For oil-soluble carbon-based quantum dots, appropriately enhancing their water solubility is necessary to improve their amphiphilic properties in the preparation of nano-oil displacement agents. Specifically, under ice bath conditions, 5 mL of a yellow p-aminobenzenesulfonic acid diazonium salt system was slowly added dropwise to a graphene quantum dot dispersion, and stirring was continued for 2 h under ice bath conditions. The reaction was then stirred at room temperature for 8 h. The system was dialyzed for 24 h in a dialysis bag with a molecular weight cutoff of 500, and freeze-dried to obtain a carbon-based nano-oil displacement agent powder with optimized hydrophilicity, named "One-Pot CQ-Hydrophilic".

[0068] The above includes a total of 8 carbon-based nano-displacement agents: 6 amphiphilic carbon-based nano-displacement 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 using 1,3,6-trinitropyrene and hexylamine (prepared in Example 8); and an amphiphilic carbon-based nano-displacement agent "one-pot CQ-hydrophilic" obtained by hydrophilic modification of the p-aminobenzenesulfonic acid diazonium salt system (prepared in Example 9).

[0069] Example 10:

[0070] Eight amphiphilic carbon-based nano-oil displacement agents were added to water and ultrasonically dispersed to prepare dispersions with a concentration of 3 mg / mL. The dispersions were then mixed with cyclohexane, toluene, and n-octane at a volume ratio of 1:1, and ultrasonically emulsified for 3 minutes in a 300W probe-type ultrasonic disperser. After standing for 3 hours, the emulsification rate was measured, and the average particle size of the emulsion bubbles was observed and statistically analyzed under a microscope. The results are as follows: Figure 3 As shown in ac.

[0071] Eight amphiphilic carbon-based nano-displacement agents were successfully used to prepare stable emulsion systems with emulsification rates greater than 60% and particle sizes less than 20 micrometers in their dispersion / cyclohexane systems. In the dispersion / toluene system, stable emulsion systems with emulsification rates greater than 75% and particle sizes less than 15 micrometers were successfully prepared. In the dispersion / n-octane system, stable emulsion systems with emulsification rates greater than 40% and particle sizes less than 25 micrometers were successfully prepared. The differences between different solvents are related to their viscosity and interaction with the nano-displacement agents. The emulsification performance of the eight prepared amphiphilic carbon-based nano-displacement agents varied. The "one-pot CQ" prepared in Example 8 exhibited a significantly higher level of emulsification and smaller average droplet size. Specifically, its dispersion / cyclohexane system had an emulsification rate of 84.3% and an average droplet size of 8.23 ​​μm; its dispersion / toluene system had an emulsification rate of 92.5% and an average droplet size of 3.21 μm; and its dispersion / n-octane system had an emulsification rate of 72.3% and an average droplet size of 12.98 μm. Figure 4 , Figure 5 Optical photographs and microscopic images of emulsion systems prepared by mixing the dispersion (3 mg / mL) of the amphiphilic carbon-based nano-oil displacement agent with equal volumes of cyclohexane, toluene, and n-octane were shown. The emulsions exhibited high emulsification rates, dense droplets, and relatively uniform particle size.

[0072] The surface tension of 3 mg / mL dispersions of eight amphiphilic carbon-based nano-oil displacement agents was measured using a surface tension meter. The results are as follows: Figure 5 As shown, it significantly demonstrates that both the carbon-based nano-oil displacement agent dispersion / cyclohexane system can significantly reduce the surface tension of the water system. Among them, 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.

[0073] The interfacial tension between 3 mg / mL dispersions of eight 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, carbon-based nano-oil displacement agents significantly reduce the interfacial tension between water and n-octane. However, the extent of this reduction varies depending on the raw materials and preparation methods. In particular, the "one-pot CQ" prepared in Example 8 can reduce the interfacial tension between the two phases to an excellent 1.5 mN / m.

[0074] The HLB value of the "one-pot CQ" amphiphilic carbon-based nano-displacement agent was determined using a traditional emulsification method. First, the "one-pot CQ" amphiphilic carbon-based nano-displacement agent prepared in Example 8 was dispersed in an aqueous solution to prepare a 3 mg / mL dispersion. Cottonseed oil and turpentine oil of different masses were mixed according to Table 1 to prepare mixed oil phases with gradient HLB values. The mixed oil phases and dispersions were mixed at a mass ratio of 1:4, and the mixture was ultrasonically sonicated to form an emulsion. The emulsion system was then allowed to stand for 2 days. Figure 8 , Figure 9 The images show the droplet state and average particle size of an emulsion system formed by mixing a dispersion with oil phases of different HLB values, observed under a Leica microscope. The emulsion with the smallest particle size was observed at an HLB value of 13, indicating that the prepared high-emulsification-level "one-pot CQ" amphiphilic carbon-based nano-oil displacement agent has an HLB value of 13.

Claims

1. A method for preparing an amphiphilic carbon-based nano-oil displacement agent with high emulsification level, characterized in that: The steps are as follows: (1) Add glucose to sodium hydroxide solution, stir to dissolve and carry out hydrothermal reaction; then cool the reaction system to room temperature, filter to remove blocky impurities and slowly add dilute hydrochloric acid to the obtained filtrate to flocculate the carbon dot material, collect the precipitate by centrifugation, wash with pure water and freeze dry to obtain powdered carbon quantum dot material prepared from glucose. In the sodium hydroxide solution, 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℃, the hydrothermal reaction time is 5~7 h, and the concentration of dilute hydrochloric acid is 1~2 mol / L. (2) 1,3,6-trinitropyrene was added to a sodium hydroxide solution, ultrasonically dispersed, and then subjected to a hydrothermal reaction. Concentrated hydrochloric acid was then slowly added dropwise to the reaction system cooled to room temperature to cause the graphene quantum dot material to flocculate. The precipitate was collected by centrifugation, washed with pure water, and freeze-dried to obtain powdered graphene quantum dot material prepared from 1,3,6-trinitropyrene. In the sodium hydroxide solution, the concentration of 1,3,6-trinitropyrene was 4-6 mg / mL, the concentration of sodium hydroxide was 7-9 mg / mL, the hydrothermal reaction temperature was 190-210℃, and the hydrothermal reaction time was 10-13 h. The mass fraction of concentrated hydrochloric acid was 36-38%. (3) Lysine was added to sodium hydroxide solution, ultrasonically dispersed and then subjected to hydrothermal reaction; then concentrated hydrochloric acid was slowly added dropwise to the reaction system cooled to room temperature to cause the carbon dot material to flocculate, the precipitate was collected by centrifugation, washed with pure water and freeze-dried to obtain powdered carbon quantum dot material prepared from lysine. In the sodium hydroxide solution, the concentration of lysine is 8-12 mg / mL, and the concentration of sodium hydroxide is 10-14 mg / mL; the hydrothermal reaction temperature is 170-200℃, and the hydrothermal reaction time is 4-8 h; the mass fraction of concentrated hydrochloric acid is 36-38%. (4) Add ascorbic acid to pure water, disperse it by ultrasonication, and then carry out a hydrothermal reaction; then slowly add concentrated hydrochloric acid to the reaction system cooled to room temperature to cause the carbon dot material to flocculate, collect the precipitate by centrifugation, wash with pure water and freeze dry to obtain powdered carbon quantum dot material prepared from ascorbic acid; the concentration of ascorbic acid in the water system is 40~60mg / mL, the hydrothermal reaction temperature is 180~200℃, the hydrothermal reaction time is 5~8h; the mass fraction of concentrated hydrochloric acid is 36~38%; (5) Chitosan was added to acetic acid solution, ultrasonically dispersed and then subjected to hydrothermal reaction; the reaction system was then cooled to room temperature, large pieces of material 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 carbon quantum dot material prepared from chitosan; the concentration of chitosan in sodium hydroxide solution was 30~40 mg / mL, and the mass concentration of acetic acid solution was 1~2%; the hydrothermal reaction time was 180~210℃, the hydrothermal reaction time was 10~14h, and the freeze-drying temperature range was -40℃~-30℃; (6) Add the hydrophilic carbon-based quantum dot material prepared in any of steps (1) to (5) to a PBS buffer solution, then add the catalysts 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide, slowly add hexylamine and then ultrasonically disperse it evenly; react under water bath conditions, then cool the resulting reaction system to room temperature and transfer it to a dialysis bag for dialysis, freeze-dry the liquid in the bag to obtain an amphiphilic carbon-based nano-oil displacement agent with high emulsification level prepared by modifying with carbon-based quantum dots as a precursor; In the PBS buffer solution, the final concentration of carbon dot material is 5~10 mg / mL; the concentration of 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℃, and the water bath reaction time is 3~5 h.

2. The preparation method of an amphiphilic carbon-based nano-oil displacement agent with high emulsification level as described in claim 1, characterized in that: In steps (1) to (4), hydrochloric acid is slowly added to adjust the pH of the reaction system to 1 to 2; after washing with pure water, the pH of the reaction system is 4 to 5.

3. The preparation method of an amphiphilic carbon-based nano-oil displacement agent with high emulsification level as described in claim 1, characterized in that: In steps (5) and (6), the dialysis bag used for dialysis has a molecular weight cutoff of 500-1000, the dialysis time is 20-30 hours, and the water is changed every 6-10 hours.

4. An amphiphilic carbon-based nano-oil displacement agent with high emulsification level, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 3.

5. A method for preparing an amphiphilic carbon-based nano-oil displacement agent with 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 hexylamine. After ultrasonic dispersion, a hydrothermal reaction was carried out. After the reaction was completed, 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. The final concentration of 1,3,6-trinitropyrene in the sodium hydroxide solution was 4-6 mg / mL, the final concentration of sodium hydroxide was 7-9 mg / mL, and the final concentration of hexylamine was 8-12 mg / mL. The hydrothermal reaction temperature was 180-210℃, and the hydrothermal reaction time was 10-13 h. (b) Dissolve p-aminobenzenesulfonic acid in sodium hydroxide solution, add sodium nitrite under ice bath conditions to dissolve and mix evenly, then slowly add concentrated hydrochloric acid dropwise while stirring to obtain the p-aminobenzenesulfonic acid diazonium salt system; the final concentration of sodium hydroxide in the sodium hydroxide solution 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℃; 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 time after adding concentrated hydrochloric acid is 20~60 minutes; (c) The amphiphilic carbon-based nano-displacing agent prepared by the one-pot method in step (a) is added to ethanol to obtain an ethanol dispersion; then the p-aminobenzenesulfonic acid diazonium salt system obtained in step (c) is slowly added dropwise to the ethanol dispersion. The reaction is first stirred in an ice bath, and then stirred at room temperature. After dialysis, the liquid in the bag is freeze-dried to obtain an amphiphilic carbon-based nano-displacing agent with optimized performance and high emulsification level. The concentration of the ethanol dispersion of the amphiphilic carbon-based nano-displacing agent prepared by the one-pot method is 8~12 mg / mL, the volume ratio of the p-aminobenzenesulfonic acid diazonium salt system to the ethanol dispersion is 0.4~0.6:1, the temperature of the ice bath is 0~5℃, and the reaction time in the ice bath is 2~3 h; the temperature of the room temperature is 20~28℃, and the reaction time at room temperature is 6~10 h.

6. The preparation method of an amphiphilic carbon-based nano-oil displacement agent with high emulsification level as described in claim 5, characterized in that: In steps (a) and (c), the dialysis bag used for dialysis has a molecular weight cutoff of 500-1000, the dialysis time is 20-30 hours, and the water is changed every 6-10 hours.

7. An amphiphilic carbon-based nano-displacement agent with high emulsification level, characterized in that: It is prepared by the preparation method described in any one of claims 5 or 6.

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