A nano-emulsifier and its preparation method and application

Abstract

The present application discloses a nano-emulsifier and its preparation method and application. The nano-emulsifier is prepared by polymerization reaction of carbon dot material, propylene oxide, ethylene oxide and a catalyst. The carbon dot material is a nanoparticle formed by stacking layered structures, and the carbon atoms in any layered structure are arranged in a regular hexagonal array, and the edge of any layered structure has a hydroxyl group that reacts with propylene oxide and / or ethylene oxide. The present application uses a carbon dot material with a layered structure as an initiator. Not only does it utilize the layered structure arrangement to make the carbon dot material have a higher chemical stability, thereby making the nano-emulsifier have the characteristics of high temperature and high salt resistance; it also introduces a carbon dot material containing multiple hydroxyl groups and hydrophobic groups on the surface, so that the prepared nano-emulsifier forms a strong interaction with the cycloalkanes, asphaltenes and colloids of the crude oil components, thereby significantly improving the low-temperature oil-water separation efficiency of the crude oil emulsion; the raw materials are green and economical, which is conducive to large-scale industrial promotion and production.

Description

Technical Field

[0001] The present application relates to the field of oil-water separation in oilfield chemistry, and in particular to a nano-emulsifier and a preparation method and application thereof. Background Art

[0002] Demulsifiers are surfactants or polymer compounds that destabilize emulsions. The first generation of demulsifiers primarily consisted of small-molecule surfactants, which effectively separate oil and water by altering the HLB value, but this resulted in a longer dehydration time. The second generation of demulsifiers primarily consisted of polyether-based polymers. These polymers disperse in the oil phase and penetrate the protective layer of emulsified water droplets, disrupting the protective layer and bringing the droplets closer together and into contact, thereby breaking the emulsion through flocculation. Compared to small-molecule surfactants, polymer demulsifiers exhibit a more pronounced flocculation effect, enabling rapid oil-water separation. They are now widely used in various fields, including oilfields. Polyether demulsifiers also allow for easier manipulation of demulsifier molecular properties by varying the ratio of PO (propylene oxide) to EO (ethylene oxide), to meet the demulsification requirements of different crude oils.

[0003] The most commonly used polyether polymer demulsifiers are mainly phenolamine and phenolic demulsifiers. The starting agents of the above demulsifiers are mainly phenolamine resins and phenolic resins, and their preparation process mainly uses phenolic substances such as phenol, nonylphenol, cardanol, bisphenol A, and raw materials such as formaldehyde and polyethylene polyamine. The above raw materials are highly biotoxic and have a great impact on the environment. At the same time, because phenolic resin polyether mainly has a comb-like structure, while phenolamine resin polyether has a branched structure, it is difficult to further increase the branching degree of polyether polymer demulsifiers with existing processes, and thus it is difficult to further improve the flocculation effect on water droplets. Therefore, it is urgent to propose a new demulsifier to solve the above problems existing in existing polyether polymer demulsifiers. Summary of the Invention

[0004] The purpose of this application is to provide a nano-emulsifier and its preparation method and application, which are used to solve the problems of existing polyether polymer demulsifiers, such as high raw material toxicity, difficulty in increasing the degree of branching, and low oil-water separation efficiency at low temperatures.

[0005] To solve the above technical problems, the first solution provided in this application is a nano-emulsifier, which is prepared by polymerization reaction of carbon dot material, propylene oxide, ethylene oxide and a catalyst; the carbon dot material is a nanoparticle formed by stacking layered structures, and the carbon atoms in any layered structure are arranged in a regular hexagonal array, and the edge of any layered structure has a hydroxyl group that reacts with propylene oxide and / or ethylene oxide.

[0006] In the technical solution of the embodiment of the present application, a carbon dot material with a special structure (abbreviated as CDs) is used as an initiator, and the synthesized carbon dot material is a layered structure nanoparticle in a three-dimensional space, as shown in the attached Figure 1 As shown, first, since the carbon atoms in the single layered structure are arranged in a regular hexagonal array, the carbon dot material has high chemical stability, so that the prepared nano-emulsifier has the characteristics of resistance to high temperature and high salt; secondly, the hydroxyl groups (-OH) at the edge of the carbon dot layered structure are polymerized with PO and EO, and the lipophilicity of PO and the hydrophilicity of EO are utilized to improve the interfacial activity of the carbon dot material, thereby significantly improving the flocculation effect of the demulsifier on nearby water droplets; furthermore, the nano-emulsifier prepared in this application has a three-dimensional spatial structure that is not possessed by existing polyether polymer demulsifiers. By introducing carbon dot materials containing multiple hydroxyl groups and hydrophobic groups on the surface, the branching degree of the polyether is effectively improved. At the same time, the hydrocarbon chains on the surface of the carbon dot material can effectively improve the interaction between the initiator and the crude oil components, thereby significantly improving the low-temperature oil-water separation efficiency of the crude oil emulsion; finally, the raw materials used in this application are green and economical, which solves the problem of high toxicity of the raw materials of existing polyether polymer demulsifiers and is conducive to large-scale industrial promotion and production.

[0007] In some embodiments, the mass ratio of the carbon dot material to propylene oxide is 1:30-1:110, and the mass ratio of propylene oxide to ethylene oxide is 1:1-2.5:1; and the particle size of the carbon dot material is 1-10 nm.

[0008] In some embodiments, the catalyst is selected from any one of barium laurate, sodium hydroxide, and potassium hydroxide.

[0009] To solve the above technical problems, the second solution provided by this application is a method for preparing a nano-emulsifier. This method is used to prepare the nano-emulsifier described in the first solution, and this nano-emulsifier can be used as a demulsifier for oil-water separation in oilfield produced fluids. The preparation method of the nano-emulsifier comprises the following steps:

[0010] S1, sucrose is mixed with a surfactant and subjected to a pyrolysis reaction to prepare a carbon dot material.

[0011] S2, mixing the carbon dot material, propylene oxide, ethylene oxide and a catalyst and performing a polymerization reaction to prepare a nano-emulsifier.

[0012] In some embodiments, the specific steps of step S1 are:

[0013] S11, after mixing sucrose with a surfactant, pyrolysis reaction is carried out at 160°C~220°C for 12 h~18 h to obtain initial carbon dots.

[0014] S12, mixing the initial carbon dots and water in a mass ratio of 1:1 to prepare a carbon dot aqueous solution, and freeze-drying to obtain the carbon dot material.

[0015] In some embodiments, the mass ratio of sucrose to surfactant is 1:4 to 4:1; the surfactant includes at least one of Tween80, Tween20, Tween21, Tween40, Tween60, Tween61, and Tween81.

[0016] In some embodiments, the catalyst includes a first catalyst and a second catalyst, and the first catalyst and the second catalyst are both selected from any one of barium laurate, sodium hydroxide, and potassium hydroxide.

[0017] In some embodiments, the specific steps of step S2 are:

[0018] S21, add the first catalyst to the carbon dot material, heat to 60°C and evacuate to -0.01MPa, then raise the temperature to 115°C~125°C, add propylene oxide intermittently and maintain the ambient pressure less than 0.2MPa, and continue the reaction after the addition is completed until the ambient pressure drops to -0.01MPa to obtain a polyether propylene oxide block polymer (denoted as CDs-PO).

[0019] S22, adding a second catalyst to the polyether propylene oxide block polymer, heating to 60°C and evacuating to -0.01 MPa, then raising the temperature to 85°C~95°C, intermittently adding ethylene oxide while maintaining the ambient pressure less than 0.4 MPa, and continuing the reaction after the addition is completed until the ambient pressure drops to -0.01 MPa to obtain a nano-emulsifier (denoted as CDs-PO-EO).

[0020] In some embodiments, the mass ratio of the carbon dot material to propylene oxide is 1:30-1:110, and the mass ratio of propylene oxide to ethylene oxide is 1:1-2.5:1.

[0021] In some embodiments, the mass ratio of the carbon dot material, the first catalyst, and the second catalyst is 1:(1-2):(0.5-1).

[0022] The beneficial effects of this application are:

[0023] 1) This application uses a layered carbon dot material as an initiator. Not only does it utilize the regular hexagonal array arrangement of a single layered structure to give the carbon dot material a high chemical stability, thereby making the prepared nano-emulsifier resistant to high temperature and high salt; it also effectively improves the branching degree of the polyether by introducing a carbon dot material containing multiple hydroxyl and hydrophobic groups on the surface, so that the prepared nano-emulsifier forms a strong interaction with the cycloalkanes, asphaltenes and colloids of the crude oil components, thereby significantly improving the low-temperature oil-water separation efficiency of the crude oil emulsion.

[0024] 2) The raw materials used in this application are green and economical, and have good foaming, foam stabilization and liquid carrying properties, which are conducive to large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0026] Figure 1 This is a schematic structural diagram of the carbon dot material in one embodiment of the method for preparing the nano-emulsifier provided in this application;

[0027] Figure 2 TEM image of the carbon dot material in Example 1 of the present application (the inset in the upper left corner is the particle size distribution diagram, and the inset in the upper right corner is the HRTEM image);

[0028] Figure 3 TEM image of the carbon dot material in Comparative Example 3 of this application (the illustration in the upper right corner is an HRTEM image);

[0029] Figure 4 This is a comparison chart of the dehydration experiments of the nano-emulsifier prepared in Example 1 of the present application at different concentrations. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0031] Unless otherwise specified, the experimental materials used in this application were purchased from the market.

[0032] 1. Preparation method

[0033] Example 1

[0034] Example 1 of the present application provides a method for preparing a nano-emulsifier, the steps of which are:

[0035] (1) 2 g of sucrose and 8 g of Tween 80 were mixed and pyrolyzed at 220 °C for 12 h to prepare the initial carbon dots. After the reaction, the initial carbon dots were added to 10 g of water to prepare a carbon dot aqueous solution, which was then freeze-dried to obtain the carbon dot material.

[0036] (2) The carbon dot material was added to a high-pressure reactor, along with 10 g of the catalyst barium laurate. The reaction mixture was heated to 60°C and evacuated to a gauge pressure of -0.01 MPa using a vacuum pump. Subsequently, when the temperature was raised to 120 ± 5°C, 300 g of propylene oxide was intermittently added while maintaining the reactor pressure below 0.2 MPa. After the addition was complete, the reaction was continued until the pressure dropped to -0.01 MPa. The reactor was then opened to obtain a polyether propylene oxide block polymer.

[0037] (3) The polyether propylene oxide block polymer was added to an autoclave, along with 5 g of the catalyst barium laurate. The mixture was heated to 60°C and evacuated to -0.01 MPa. The temperature was then raised to 90 ± 5°C, and 120 g of ethylene oxide was intermittently added while maintaining the reactor pressure below 0.4 MPa. After the addition was complete, the reaction was continued until the pressure dropped to -0.01 MPa. The reactor was then opened to obtain a nano-emulsifier.

[0038] Example 2

[0039] Example 2 of the present application provides a method for preparing a nano-emulsifier, the steps of which are:

[0040] (1) 8 g of sucrose and 2 g of Tween 80 were mixed and pyrolyzed at 160°C for 18 h to prepare the initial carbon dots. After the reaction, the initial carbon dots were added to 10 g of water to prepare a carbon dot aqueous solution, which was then freeze-dried to obtain the carbon dot material.

[0041] (2) The carbon dot material was added to a high-pressure reactor, along with 10 g of sodium hydroxide catalyst. The reaction mixture was heated to 60°C and evacuated to a gauge pressure of -0.01 MPa using a vacuum pump. Subsequently, when the temperature was raised to 120 ± 5°C, 1100 g of propylene oxide was intermittently added while maintaining the reactor pressure below 0.2 MPa. After the addition was complete, the reaction was continued until the pressure dropped to -0.01 MPa. The reactor was then opened to obtain a polyether propylene oxide block polymer.

[0042] (3) The polyether propylene oxide block polymer was added to an autoclave, and 5 g of sodium hydroxide catalyst was added. The reaction was heated to 60°C and evacuated to -0.01 MPa. The temperature was then raised to 90 ± 5°C, and 1100 g of ethylene oxide was intermittently added while maintaining the reactor pressure below 0.4 MPa. After the addition was completed, the reaction was continued until the pressure dropped to -0.01 MPa. The reactor was opened to obtain a nano-emulsifier.

[0043] Example 3

[0044] Example 3 of the present application provides a method for preparing a nano-emulsifier, the steps of which are:

[0045] (1) 5 g of sucrose and 5 g of Tween 80 were mixed and pyrolyzed at 220 °C for 12 h to prepare the initial carbon dots. After the reaction, 10 g of water was added to the initial carbon dots to prepare a carbon dot aqueous solution, which was then freeze-dried to obtain the carbon dot material.

[0046] (2) The carbon dot material was added to a high-pressure reactor, along with 10 g of potassium hydroxide catalyst. The reaction mixture was heated to 60°C and evacuated to a gauge pressure of -0.01 MPa using a vacuum pump. Subsequently, when the temperature was raised to 120 ± 5°C, 300 g of propylene oxide was intermittently added while maintaining the reactor pressure below 0.2 MPa. After the addition was completed, the reaction was continued until the pressure dropped to -0.01 MPa. The reactor was then opened to obtain a polyether propylene oxide block polymer.

[0047] (3) The polyether propylene oxide block polymer was added to an autoclave, and 5 g of potassium hydroxide catalyst was added. The reaction mixture was heated to 60°C and evacuated to -0.01 MPa. The temperature was then raised to 90 ± 5°C, and 120 g of ethylene oxide was intermittently added while maintaining the pressure in the autoclave below 0.4 MPa. After the addition was completed, the reaction was continued until the pressure dropped to -0.01 MPa. The autoclave was opened to obtain a nano-emulsifier.

[0048] Example 4

[0049] Example 4 of the present application provides a method for preparing a nano-emulsifier, the steps of which are:

[0050] (1) 4 g of sucrose and 6 g of Tween 20 were mixed and pyrolyzed at 160°C for 18 h to prepare the initial carbon dots. After the reaction, the initial carbon dots were added to 10 g of water to prepare a carbon dot aqueous solution, which was then freeze-dried to obtain the carbon dot material.

[0051] (2) The carbon dot material was added to a high-pressure reactor, along with 10 g of the catalyst barium laurate. The reaction mixture was heated to 60°C and evacuated to a gauge pressure of -0.01 MPa using a vacuum pump. Subsequently, when the temperature was raised to 120 ± 5°C, 1100 g of propylene oxide was intermittently added while maintaining the reactor pressure below 0.2 MPa. After the addition was complete, the reaction was continued until the pressure dropped to -0.01 MPa. The reactor was then opened to obtain a polyether propylene oxide block polymer.

[0052] (3) The polyether propylene oxide block polymer was added to an autoclave, along with 5 g of the catalyst barium laurate. The reaction mixture was heated to 60°C and evacuated to -0.01 MPa. The temperature was then raised to 90 ± 5°C, and 1100 g of ethylene oxide was intermittently added while maintaining the reactor pressure below 0.4 MPa. After the addition was complete, the reaction was continued until the pressure dropped to -0.01 MPa. The reactor was then opened to obtain a nanoemulsifier.

[0053] Example 5

[0054] Example 5 of the present application provides a method for preparing a nano-emulsifier, the steps of which are:

[0055] (1) 5 g of sucrose and 5 g of Tween 80 were mixed and pyrolyzed at 180 °C for 16 h to prepare the initial carbon dots. After the reaction, the initial carbon dots were added to 10 g of water to prepare a carbon dot aqueous solution, which was then freeze-dried to obtain the carbon dot material.

[0056] (2) The carbon dot material was added to a high-pressure reactor, along with 10 g of the catalyst barium laurate. The reaction mixture was heated to 60°C and evacuated to a gauge pressure of -0.01 MPa using a vacuum pump. Subsequently, when the temperature was raised to 120 ± 5°C, 500 g of propylene oxide was intermittently added while maintaining the reactor pressure below 0.2 MPa. After the addition was complete, the reaction was continued until the pressure dropped to -0.01 MPa. The reactor was then opened to obtain a polyether propylene oxide block polymer.

[0057] (3) The polyether propylene oxide block polymer was added to an autoclave, along with 5 g of the catalyst barium laurate. The mixture was heated to 60°C and evacuated to -0.01 MPa. The temperature was then raised to 90 ± 5°C, and 250 g of ethylene oxide was intermittently added while maintaining the reactor pressure below 0.4 MPa. After the addition was complete, the reaction was continued until the pressure dropped to -0.01 MPa. The reactor was then opened to obtain a nano-emulsifier.

[0058] Comparative Example 1

[0059] The steps for preparing the nano-emulsifier provided in Comparative Example 1 are as follows:

[0060] (1) Add 5 g of nonylphenol and 5 g of polyethylene polyamine into a three-necked flask, place it in an oil bath, and slowly add formaldehyde solution at a rate of 1 drop / s. After the addition is completed, quickly raise the temperature to 85°C and react for 3 h. Then, add xylene for high-temperature dehydration, and then remove the xylene by vacuum distillation to obtain a reddish-brown viscous liquid, which is the phenolamine resin.

[0061] (2) The phenolamine resin was added to a high-pressure reactor, along with 10 g of the catalyst barium laurate. The mixture was heated to 60°C and evacuated to a gauge pressure of -0.01 MPa using a vacuum pump. Subsequently, when the temperature was raised to 120±5°C, 500 g of propylene oxide was intermittently added while maintaining the reactor pressure below 0.2 MPa. After the addition was completed, the reaction was continued until the pressure dropped to -0.01 MPa. The reactor was then opened to obtain a polyether propylene oxide block polymer.

[0062] (3) The polyether propylene oxide block polymer was added to an autoclave, along with 5 g of the catalyst barium laurate. The reaction mixture was heated to 60°C and evacuated to -0.01 MPa. The temperature was then raised to 90±5°C, and 250 g of ethylene oxide was intermittently added while maintaining the reactor pressure below 0.4 MPa. After the addition was complete, the reaction was continued until the pressure dropped to -0.01 MPa. The reactor was then opened to obtain a comparative demulsifier.

[0063] Comparative Example 2

[0064] The steps for preparing the nano-emulsifier provided in Comparative Example 2 are as follows:

[0065] (1) Add 10 g of nonylphenol to a three-necked flask, place it in an oil bath, and slowly add formaldehyde solution at a rate of 1 drop / s. After the addition is completed, quickly raise the temperature to 85 °C and react for 3 h. Then, add xylene for high-temperature dehydration, and then remove the xylene by vacuum distillation to obtain a reddish-brown viscous liquid, which is phenolic resin.

[0066] (2) The phenolamine resin was added to a high-pressure reactor, along with 10 g of the catalyst barium laurate. The mixture was heated to 60°C and evacuated to a gauge pressure of -0.01 MPa using a vacuum pump. Subsequently, when the temperature was raised to 120±5°C, 1100 g of propylene oxide was intermittently added while maintaining the reactor pressure below 0.2 MPa. After the addition was completed, the reaction was continued until the pressure dropped to -0.01 MPa. The reactor was then opened to obtain a polyether propylene oxide block polymer.

[0067] (3) The polyether propylene oxide block polymer was added to an autoclave, along with 5 g of the catalyst barium laurate. The autoclave was heated to 60°C and evacuated to -0.01 MPa. The temperature was then raised to 90±5°C, and 1100 g of ethylene oxide was intermittently added while maintaining the autoclave pressure below 0.4 MPa. After the addition was complete, the reaction was continued until the pressure dropped to -0.01 MPa. The autoclave was then opened to obtain a comparative demulsifier.

[0068] Comparative Example 3

[0069] The steps for preparing the nano-emulsifier provided in Comparative Example 3 are as follows:

[0070] (1) 10 g of sugarcane bagasse and 2 g of ethylenediamine were reacted at 220°C for 7 h. The ratio of sugarcane bagasse to water was 1 g:30 mL. Initial carbon dots were prepared by a hydrothermal method. After the reaction, 10 g of water was added to the initial carbon dots to prepare a carbon dot aqueous solution, which was then freeze-dried to obtain the carbon dot material.

[0071] (2) The carbon dot material was added to a high-pressure reactor, along with 10 g of the catalyst barium laurate. The reaction mixture was heated to 60°C and evacuated to a gauge pressure of -0.01 MPa using a vacuum pump. Subsequently, when the temperature was raised to 120 ± 5°C, 300 g of propylene oxide was intermittently added while maintaining the reactor pressure below 0.2 MPa. After the addition was complete, the reaction was continued until the pressure dropped to -0.01 MPa. The reactor was then opened to obtain a polyether propylene oxide block polymer.

[0072] (3) The polyether propylene oxide block polymer was added to an autoclave, along with 5 g of the catalyst barium laurate. The mixture was heated to 60°C and evacuated to -0.01 MPa. The temperature was then raised to 90 ± 5°C, and 120 g of ethylene oxide was intermittently added while maintaining the reactor pressure below 0.4 MPa. After the addition was complete, the reaction was continued until the pressure dropped to -0.01 MPa. The reactor was then opened to obtain a nano-emulsifier.

[0073] 2. Test Method

[0074] 1) TEM characterization of the carbon dot materials prepared in Example 1 and Comparative Example 3.

[0075] 2) With reference to SY-T 5281-2000 Crude Oil Demulsifier Performance Test Method (Bottle Test Method), demulsifier was added at a concentration of 100 mg / L to demulsify the emulsion gel.

[0076] The specific steps are as follows: accurately pour 100 mL of crude oil emulsion (water content 50%) into a 100 mL colorimetric tube, place it in a constant temperature water bath at 50 ° C to heat, then use a pipette to add a certain amount of demulsifier (concentration of 100 mg / L), use a constant temperature oscillator to shake at 100 rpm for 1 minute to mix the demulsifier and crude oil evenly, then place it in a constant temperature water bath at 50 ° C to stand for demulsification, and read and record the volume percentage of demulsified water at the specified time.

[0077] 3) Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were aged at 120° C. for 24 hours to perform a demulsification and dehydration test, and the dehydration amount and interface conditions before and after aging were recorded.

[0078] 3. Analysis of test results of various embodiments

[0079] I. The carbon dot material prepared in Example 1 was subjected to TEM test, and the results are shown in the attached figure. Figure 2 As shown, combined with the attached Figure 1 It can be seen that the average diameter of the carbon dot material prepared in Example 1 of the present application is 3.22±1.00 nm, with obvious lattice fringes, and the lattice fringes spacing is 0.34 nm, which corresponds to the lattice fringes spacing of graphene, indicating that the above-mentioned preparation method of the present application can be used to prepare the carbon dot material with the same structure as the attached graphene. Figure 1The carbon dot material prepared in Comparative Example 3 was subjected to TEM test, and the results are shown in the attached figure. Figure 3 As shown, it can be seen that the carbon dots prepared in Comparative Example 3 of the present application are amorphous carbon materials, which are different from the carbon dot material structure prepared in Example 1 and do not have a special layered structure.

[0080] II. Dehydration experiments were conducted on the nano-emulsifier prepared in Example 1 at different concentrations. The results were as follows Figure 4 As shown, Figure 4 The concentrations of nano-emulsifiers used in the experiment are as follows from left to right: 0 mg / L, 10 mg / L, 25 mg / L, 50 mg / L, 75 mg / L, 100 mg / L. Figure 4 It can be seen that as the concentration of the nano-emulsifier prepared in Example 1 gradually increases, the dehydration effect also gradually improves, wherein the preferred concentration is 50 mg / L to 100 mg / L.

[0081] III. The dehydration test results of the demulsifiers prepared in Examples 1 to 5 and Comparative Examples 1 to 3 at 50°C are shown in Table 1:

[0082] Table 1 Dehydration test results of different demulsifiers at 50℃

[0083]

[0084] As can be seen from Table 1, the dehydration effect of the nano-emulsifiers prepared in Examples 1 to 5 of the present application is significantly better than that of the demulsifiers prepared by the existing process in Comparative Examples 1 to 2 and the demulsifier prepared based on the amorphous carbon material in Comparative Example 3. This shows that the present application uses a layered carbon dot material as an initiator. By introducing a carbon dot material containing multiple hydroxyl groups and hydrophobic groups on the surface, the branching degree of the polyether can be effectively improved, so that the prepared nano-emulsifier forms a strong interaction with the cycloalkanes, asphaltenes and colloids of the crude oil components, and significantly improves the low-temperature oil-water separation efficiency of the crude oil emulsion; among them, the performance of Example 5 is better.

[0085] IV. The dehydration test results of Examples 1 to 2 and Comparative Examples 1 to 3 before and after aging at 120°C for 24 h are shown in Table 2:

[0086] Table 2 Dehydration test results of different demulsifiers before and after aging at 120℃ for 24 h

[0087]

[0088] As can be seen from Table 2, the dehydration amount and interface conditions of Examples 1-2 did not change significantly before and after aging at 120°C for 24 h, while the dehydration amount of Comparative Examples 1-3 was significantly reduced before and after aging at 120°C for 24 h. This proves that the carbon dot material synthesized in the present application has high chemical stability, and the prepared nano-emulsifier has better high temperature resistance than the existing demulsifier and the demulsifier prepared based on amorphous carbon material.

[0089] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0090] The above-described embodiments merely represent implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A nano-emulsifier, characterized in that: The nano-emulsifier is prepared by polymerization reaction of carbon dot material, propylene oxide, ethylene oxide and catalyst; The carbon dot material is obtained by mixing sucrose with a surfactant and subjecting the mixture to a pyrolysis reaction at 160°C to 220°C for 12 h to 18 h, wherein the surfactant comprises at least one of Tween80, Tween20, Tween21, Tween40, Tween60, Tween61, and Tween81, and the mass ratio of the sucrose to the surfactant is 1:4 to 4:

1.

2. The nano-emulsifier according to claim 1, characterized in that The mass ratio of the carbon dot material to propylene oxide is 1:30 to 1:110, and the mass ratio of propylene oxide to ethylene oxide is 1:1 to 2.5:1; The particle size of the carbon dot material is 1-10 nm.

3. The nano-emulsifier according to claim 1, characterized in that The catalyst is selected from any one of barium laurate, sodium hydroxide and potassium hydroxide.

4. A method for preparing a nano-emulsifier as claimed in any one of claims 1 to 3, characterized in that: The steps include: S1, sucrose and surfactant were mixed and pyrolyzed at 160℃~220℃ for 12 h~18 h to prepare carbon dot material; S2, mixing the carbon dot material, propylene oxide, ethylene oxide and a catalyst and performing a polymerization reaction to prepare a nano-emulsifier; The surfactant includes at least one of Tween80, Tween20, Tween21, Tween40, Tween60, Tween61, and Tween81; The mass ratio of the sucrose to the surfactant is 1:4 to 4:

1.

5. The method for preparing the nano-emulsifier according to claim 4, wherein: The specific steps of the S1 step are: S11, after mixing sucrose with a surfactant, pyrolysis reaction was carried out at 160℃~220℃ for 12 h~18 h to obtain initial carbon dots; S12, mixing the initial carbon dots and water in a mass ratio of 1:1 to prepare a carbon dot aqueous solution, and freeze-drying to obtain the carbon dot material.

6. The method for preparing the nano-emulsifier according to claim 4, wherein: The catalyst includes a first catalyst and a second catalyst, and the first catalyst and the second catalyst are both selected from any one of barium laurate, sodium hydroxide, and potassium hydroxide; The specific steps of the S2 step are: S21, adding a first catalyst to the carbon dot material, heating to 60° C. and evacuating to -0.01 MPa, then raising the temperature to 115° C. to 125° C., intermittently adding propylene oxide while maintaining the ambient pressure less than 0.2 MPa, and continuing the reaction after the addition is completed until the ambient pressure drops to -0.01 MPa to obtain a polyether propylene oxide block polymer; S22, adding a second catalyst to the polyether propylene oxide block polymer, heating to 60°C and evacuating to -0.01 MPa, then raising the temperature to 85°C~95°C, intermittently adding ethylene oxide while maintaining the ambient pressure less than 0.4 MPa, and continuing the reaction after the addition is completed until the ambient pressure drops to -0.01 MPa to obtain the nano demulsifier.

7. The method for preparing the nano-emulsifier according to claim 6, wherein: The mass ratio of the carbon dot material to propylene oxide is 1:30-1:110, and the mass ratio of propylene oxide to ethylene oxide is 1:1-2.5:

1.

8. The method for preparing the nano-emulsifier according to claim 6, wherein: The mass ratio of the carbon dot material, the first catalyst and the second catalyst is 1: (1-2): (0.5-1).

9. Use of the nano-emulsifier as claimed in any one of claims 1 to 3 as an oilfield produced fluid demulsifier.

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