Nano demulsifier as well as preparation method and application thereof

Abstract

The invention discloses a nano demulsifier as well as a preparation method and application thereof. The nano demulsifier is prepared from a carbon dot material, epoxypropane, ethylene oxide and a catalyst through a polymerization reaction, the carbon dot material is nano-particles formed by stacking layered structures, carbon atoms in any layered structure are arranged in a regular hexagon array, and the edge of any layered structure is provided with hydroxyl which is subjected to polymerization reaction with propylene oxide and / or ethylene oxide. According to the preparation method, the carbon dot material with a layered structure is taken as an initiator, and the carbon dot material has relatively high chemical stability by utilizing a layered structure arrangement mode, so that the nano demulsifier has the characteristics of high temperature resistance and high salt resistance; a carbon dot material with polyhydroxy and hydrophobic groups on the surface is introduced, so that the prepared nano demulsifier has strong interaction with cycloalkane, asphaltene and colloid of crude oil components, and the low-temperature oil-water separation efficiency of crude oil emulsion is remarkably improved; the raw materials are green and economical, and industrial large-scale popularization and production are facilitated.

Description

Technical Field

[0001] This application relates to the field of oil-water separation in oilfield chemistry, and particularly relates to a nano-demulsifier and its preparation method and application. Background Art

[0002] A demulsifier is a surfactant or polymer compound that can destroy the stability of an emulsion. The first-generation demulsifiers are mainly small-molecule surfactants. The small-molecule surfactants achieve effective oil-water separation by changing the HLB value, but the dehydration time is relatively long. The second-generation demulsifiers are mainly polyether-based polymer demulsifiers. The polymer demulsifiers are dispersed in the oil phase and penetrate into the protective layer of the emulsified water droplets, destroying the protective layer to make the water droplets approach and contact each other, and achieving demulsification through flocculation. Compared with small-molecule surfactants, the polymer demulsifiers have obvious flocculation effects, so they can achieve rapid oil-water separation and are also the demulsifiers commonly used in various fields such as oilfields. The polymer polyether demulsifiers can also easily regulate the molecular properties of the demulsifiers by changing the ratio of PO (i.e., propylene oxide) and EO (i.e., ethylene oxide) to meet the demulsification requirements of different crude oils.

[0003] The most commonly used polyether polymer demulsifiers currently are mainly phenolic amine and phenolic aldehyde demulsifiers. The initiators of the above demulsifiers are mainly phenolic amine resins and phenolic aldehyde resins, and their preparation processes mainly use phenolic substances such as phenol, nonylphenol, cashew phenol, and bisphenol A, and raw materials such as formaldehyde and polyethylenepolyamine. The above raw materials have relatively high biological toxicity and have a greater impact on the environment; at the same time, since phenolic aldehyde resin polyethers are mainly comb-shaped structures, while phenolic amine resin polyethers are branched structures, it is difficult for the existing process to further improve the degree of branching of the polyether polymer demulsifiers, 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 the existing polyether polymer demulsifiers. Summary of the Invention

[0004] The purpose of this application is to provide a nano-demulsifier and its preparation method and application, which are used to solve the problems of relatively high toxicity of the raw materials of the existing polyether polymer demulsifiers, difficult to improve the degree of branching, and low oil-water separation efficiency at low temperatures.

[0005] To solve the above technical problems, the first solution provided by this application is a nano-demulsifier, which is prepared by a polymerization reaction of carbon dot materials, propylene oxide, ethylene oxide, and a catalyst; the carbon dot materials are nano-particles formed by stacking of layered structures, in which carbon atoms in any layered structure are arranged in a regular hexagon array, and the edge of any layered structure has hydroxyl groups for polymerization reaction 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 three-dimensional space. As shown in the appendix Figure 1 As shown, first, since the carbon atoms in a single layered structure are arranged in a regular hexagonal array, the carbon dot material has high chemical stability, so that the prepared nano demulsifier has the characteristics of high temperature and high salt resistance; second, through the polymerization reaction of the hydroxyl groups (-OH) at the edges of the layered structure of the carbon dot material with PO and EO, and by utilizing the lipophilicity of PO and the hydrophilicity of EO, the interfacial activity of the carbon dot material is improved, and the flocculation effect of the demulsifier on nearby water droplets is significantly enhanced; third, the nano demulsifier prepared in the present application has a three-dimensional space structure that the existing polyether polymer demulsifier does not have. By introducing a carbon dot material with polyhydroxy and hydrophobic groups on the surface, the branching degree of the polyether is effectively improved. At the same time, the carbon-hydrogen chain on the surface of the carbon dot material can effectively improve the interaction between the initiator and the components of the crude oil, thereby significantly improving the low-temperature oil-water separation efficiency of the crude oil emulsion; finally, the raw materials used in the present application are green and economical, solving the problem of high toxicity of the raw materials of the existing polyether polymer demulsifier, which is conducive to large-scale industrial production and promotion.

[0007] In some embodiments, 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 to 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 the present application is a preparation method of a nano demulsifier. This preparation method of the nano demulsifier is used to prepare the nano demulsifier in the first solution described above, and this nano demulsifier can be used as a demulsifier for oil-water separation of oilfield produced fluids. The preparation method of this nano demulsifier includes the following steps: S1, Mix sucrose with a surfactant and carry out a pyrolysis reaction to obtain a carbon dot material.

[0010] S2, Mix the carbon dot material, propylene oxide, ethylene oxide, and a catalyst and carry out a polymerization reaction to obtain a nano demulsifier.

[0011] In some embodiments, the specific steps of step S1 are: S11, After mixing sucrose with a surfactant, carry out a pyrolysis reaction at 160 °C to 220 °C for 12 h to 18 h to obtain initial carbon dots.

[0012] S12, Mix the initial carbon dots and water in a mass ratio of 1:1 to prepare a carbon dot aqueous solution, and obtain the carbon dot material after freeze-drying.

[0013] 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.

[0014] In some embodiments, the catalyst includes a first catalyst and a second catalyst, and both the first catalyst and the second catalyst are selected from any one of barium laurate, sodium hydroxide, and potassium hydroxide.

[0015] In some embodiments, the specific steps of step S2 are as follows: S21, adding the 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 and maintaining the ambient pressure less than 0.2 MPa. After the addition is completed, continue the reaction until the ambient pressure drops to -0.01 MPa to obtain a polyether propylene oxide block polymer (denoted as CDs-PO).

[0016] S22, adding the 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 to 95°C, intermittently adding ethylene oxide and maintaining the ambient pressure less than 0.4 MPa. After the addition is completed, continue the reaction until the ambient pressure drops to -0.01 MPa to obtain a nano-demulsifier (denoted as CDs-PO-EO).

[0017] In some embodiments, 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.

[0018] In some embodiments, the mass ratio of the carbon dot material, the first catalyst, and the second catalyst is 1:(1 to 2):(0.5 to 1).

[0019] The beneficial effects of this application are as follows: 1) This application uses a carbon dot material with a layered structure as an initiator. Not only does it utilize the hexagonal array arrangement of a single-layered structure to endow the carbon dot material with high chemical stability, thereby enabling the prepared nano-demulsifier to have the characteristics of high temperature and high salt resistance; but also by introducing a carbon dot material with multiple hydroxyl groups and hydrophobic groups on the surface, it effectively improves the branching degree of the polyether, enabling the prepared nano-demulsifier to form strong interactions with the naphthenes, asphaltenes, and resins in the crude oil composition, and significantly enhancing the low-temperature oil-water separation efficiency of the crude oil emulsion.

[0020] 2) The raw materials used in this application are green and economical, with good foaming performance, foam stability performance, and liquid-carrying performance, which is conducive to large-scale industrial production and promotion. Brief Description of the Drawings

[0021] To more clearly illustrate the technical solutions of the present application, the drawings used in the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 Schematic diagram of the structure of the carbon dot material in an embodiment of the preparation method of the nano demulsifier provided by the present application; Figure 2 TEM image of the carbon dot material in Example 1 of the present application (the upper left inset is the particle size distribution diagram, and the upper right inset is the HRTEM image); Figure 3 TEM image of the carbon dot material in Comparative Example 3 of the present application (the upper right inset is the HRTEM image); Figure 4 Comparison diagram of dehydration experiments of the nano demulsifier prepared in Example 1 of the present application at different concentrations. Detailed Description of the Embodiments

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0024] The experimental materials used in the present application are all obtained by market purchase unless otherwise specified.

[0025] I. Preparation Method Example 1 Example 1 of the present application provides a preparation method of a nano demulsifier, and its steps are as follows: (1) After mixing 2 g of sucrose and 8 g of Tween80, pyrolysis reaction is carried out at 220 °C for 12 h to prepare initial carbon dots by pyrolysis method. After the reaction is completed, the initial carbon dots are added to 10 g of water to prepare a carbon dot aqueous solution, and then freeze-drying can obtain the carbon dot material.

[0026] (2) Add the above carbon dot material into a high-pressure reactor, add 10 g of catalyst barium laurate, heat to 60 °C, evacuate to a gauge pressure of -0.01 MPa with a vacuum pump, and then raise the temperature to 120 ± 5 °C. Intermittently add 300 g of propylene oxide and maintain the pressure in the reactor less than 0.2 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and open the reactor to obtain a polyether propylene oxide block polymer.

[0027] (3) Add the above polyether propylene oxide block polymer into a high-pressure reactor, add 5 g of barium laurate as the catalyst, heat to 60 °C and evacuate to -0.01 MPa, then raise the temperature to 90 ± 5 °C, intermittently add 120 g of ethylene oxide and maintain the reactor pressure below 0.4 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and then open the reactor to obtain the nano-demulsifier.

[0028] Example 2 Example 2 of this application provides a method for preparing a nano-demulsifier, and the steps are as follows: (1) Mix 8 g of sucrose and 2 g of Tween80, and carry out a pyrolysis reaction at 160 °C for 18 h to prepare initial carbon dots by pyrolysis. After the reaction is completed, add the initial carbon dots to 10 g of water to prepare an aqueous solution of carbon dots, and then freeze-dry to obtain the carbon dot material.

[0029] (2) Add the above carbon dot material into a high-pressure reactor, add 10 g of sodium hydroxide as the catalyst, heat to 60 °C, evacuate to a gauge pressure of -0.01 MPa with a vacuum pump, and then raise the temperature to 120 ± 5 °C. Intermittently add 1100 g of propylene oxide and maintain the reactor pressure below 0.2 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and then open the reactor to obtain the polyether propylene oxide block polymer.

[0030] (3) Add the above polyether propylene oxide block polymer into a high-pressure reactor, add 5 g of sodium hydroxide as the catalyst, heat to 60 °C and evacuate to -0.01 MPa, then raise the temperature to 90 ± 5 °C, intermittently add 1100 g of ethylene oxide and maintain the reactor pressure below 0.4 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and then open the reactor to obtain the nano-demulsifier.

[0031] Example 3 Example 3 of this application provides a method for preparing a nano-demulsifier, and the steps are as follows: (1) Mix 5 g of sucrose and 5 g of Tween80, and carry out a pyrolysis reaction at 220 °C for 12 h to prepare initial carbon dots by pyrolysis. After the reaction is completed, add the initial carbon dots to 10 g of water to prepare an aqueous solution of carbon dots, and then freeze-dry to obtain the carbon dot material.

[0032] (2) Add the above carbon dot material into a high-pressure reactor, add 10 g of the catalyst potassium hydroxide, heat to 60 °C, evacuate with a vacuum pump to a gauge pressure of -0.01 MPa, then raise the temperature to 120 ± 5 °C, intermittently add 300 g of propylene oxide and maintain the reactor pressure below 0.2 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and open the reactor to obtain a polyether propylene oxide block polymer.

[0033] (3) Add the above polyether propylene oxide block polymer into a high-pressure reactor, add 5 g of the catalyst potassium hydroxide, heat to 60 °C and evacuate to -0.01 MPa, then raise the temperature to 90 ± 5 °C, intermittently add 120 g of ethylene oxide and maintain the reactor pressure below 0.4 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and open the reactor to obtain a nano-demulsifier.

[0034] Example 4 Example 4 of the present application provides a method for preparing a nano-demulsifier, and its steps are as follows: (1) Mix 4 g of sucrose and 6 g of Tween20, and carry out a pyrolysis reaction at 160 °C for 18 h to prepare initial carbon dots by pyrolysis. After the reaction is completed, add the initial carbon dots to 10 g of water to prepare a carbon dot aqueous solution, and then freeze-dry to obtain a carbon dot material.

[0035] (2) Add the above carbon dot material into a high-pressure reactor, add 10 g of the catalyst barium laurate, heat to 60 °C, evacuate with a vacuum pump to a gauge pressure of -0.01 MPa, then raise the temperature to 120 ± 5 °C, intermittently add 1100 g of propylene oxide and maintain the reactor pressure below 0.2 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and open the reactor to obtain a polyether propylene oxide block polymer.

[0036] (3) Add the above polyether propylene oxide block polymer into a high-pressure reactor, add 5 g of the catalyst barium laurate, heat to 60 °C and evacuate to -0.01 MPa, then raise the temperature to 90 ± 5 °C, intermittently add 1100 g of ethylene oxide and maintain the reactor pressure below 0.4 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and open the reactor to obtain a nano-demulsifier.

[0037] Example 5 Example 5 of the present application provides a method for preparing a nano-demulsifier, and its steps are as follows: (1) Mix 5 g of sucrose and 5 g of Tween80, and carry out a pyrolysis reaction at 180 °C for 16 h to prepare initial carbon dots by pyrolysis. After the reaction is completed, add the initial carbon dots to 10 g of water to prepare a carbon dot aqueous solution, and then freeze-dry to obtain a carbon dot material.

[0038] (2) Add the above carbon dot material into a high-pressure reactor, add 10 g of barium laurate catalyst, heat to 60 °C, evacuate to a gauge pressure of -0.01 MPa with a vacuum pump, then raise the temperature to 120 ± 5 °C, intermittently add 500 g of propylene oxide and maintain the reactor pressure below 0.2 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and open the reactor to obtain a polyether polypropylene oxide block polymer.

[0039] (3) Add the above polyether polypropylene oxide block polymer into a high-pressure reactor, add 5 g of barium laurate catalyst, heat to 60 °C and evacuate to -0.01 MPa, then raise the temperature to 90 ± 5 °C, intermittently add 250 g of ethylene oxide and maintain the reactor pressure below 0.4 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and open the reactor to obtain a nano-demulsifier.

[0040] Comparative Example 1 The preparation method steps of the nano-demulsifier provided in Comparative Example 1 are as follows: (1) Add 5 g of nonylphenol and 5 g of polyethylenepolyamine into a three-necked flask, place it in an oil bath, slowly add formaldehyde solution at a rate of 1 drop / s, after the dropping is completed, quickly raise the temperature to 85 °C, react for 3 h, add xylene for high-temperature dehydration, and then distill off xylene under reduced pressure. Finally, a red-brown viscous liquid is obtained, which is phenolic amine resin.

[0041] (2) Add the above phenolic amine resin into a high-pressure reactor, add 10 g of barium laurate catalyst, heat to 60 °C, evacuate to a gauge pressure of -0.01 MPa with a vacuum pump, then raise the temperature to 120 ± 5 °C, intermittently add 500 g of propylene oxide and maintain the reactor pressure below 0.2 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and open the reactor to obtain a polyether polypropylene oxide block polymer.

[0042] (3) Add the above polyether polypropylene oxide block polymer into a high-pressure reactor, add 5 g of barium laurate catalyst, heat to 60 °C and evacuate to -0.01 MPa, then raise the temperature to 90 ± 5 °C, intermittently add 250 g of ethylene oxide and maintain the reactor pressure below 0.4 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and open the reactor to obtain a comparative demulsifier.

[0043] Comparative Example 2 The preparation method steps of the nano-demulsifier provided in Comparative Example 2 are as follows: (1) Add 10 g of nonylphenol into a three-necked flask and place it in an oil bath. Slowly add the formaldehyde solution at a rate of 1 drop / s. After the addition is completed, quickly raise the temperature to 85 °C. After reacting for 3 h, add xylene for high-temperature dehydration, and then remove the xylene by vacuum distillation. Finally, a red-brown viscous liquid is obtained, which is phenolic resin.

[0044] (2) Add the above phenolic amine resin into a high-pressure reactor, add 10 g of barium laurate as a catalyst, heat to 60 °C, evacuate to a gauge pressure of -0.01 MPa with a vacuum pump, and then raise the temperature to 120 ± 5 °C. Intermittently add 1100 g of propylene oxide and maintain the pressure in the reactor less than 0.2 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and open the reactor to obtain a polyether polypropylene oxide block polymer.

[0045] (3) Add the above polyether polypropylene oxide block polymer into a high-pressure reactor, add 5 g of barium laurate as a catalyst, heat to 60 °C and evacuate to -0.01 MPa, and then raise the temperature to 90 ± 5 °C. Intermittently add 1100 g of ethylene oxide and maintain the pressure in the reactor less than 0.4 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and open the reactor to obtain a comparative demulsifier.

[0046] Comparative Example 3 The preparation method of the nano-demulsifier provided by Comparative Example 3 is as follows: (1) React 10 g of bagasse and 2 g of ethylenediamine at 220 °C for 7 h. The dosage ratio of bagasse to water is 1 g:30 mL. The initial carbon dots are prepared by a hydrothermal method. After the reaction is completed, add the initial carbon dots to 10 g of water to prepare a carbon dot aqueous solution, and then freeze-dry to obtain a carbon dot material.

[0047] (2) Add the above carbon dot material into a high-pressure reactor, add 10 g of barium laurate as a catalyst, heat to 60 °C, evacuate to a gauge pressure of -0.01 MPa with a vacuum pump, and then raise the temperature to 120 ± 5 °C. Intermittently add 300 g of propylene oxide and maintain the pressure in the reactor less than 0.2 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and open the reactor to obtain a polyether polypropylene oxide block polymer.

[0048] (3) Add the above polyether polypropylene oxide block polymer into a high-pressure reactor, add 5 g of barium laurate as a catalyst, heat to 60 °C and evacuate to -0.01 MPa, and then raise the temperature to 90 ± 5 °C. Intermittently add 120 g of ethylene oxide and maintain the pressure in the reactor less than 0.4 MPa. After the feeding is completed, continue the reaction until the pressure drops to -0.01 MPa, and open the reactor to obtain a nano-demulsifier.

[0049] II. Test method 1) Perform TEM characterization on the carbon dot materials prepared in Example 1 and Comparative Example 3.

[0050] 2) Refer to "SY-T 5281-2000 Detection Method for the Performance of Crude Oil Demulsifiers (Bottle Test Method)", with the demulsifier injection concentration of 100 mg / L, and demulsify the emulsion gel.

[0051] 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 for heating, then use a pipette gun to add a quantitative demulsifier (concentration 100 mg / L), shake it with a constant temperature shaker at 100 rpm for 1 min to mix the demulsifier and crude oil evenly, and then place it in a constant temperature water bath at 50 °C for static demulsification. Read and record the volume percentage of the separated water at the specified time.

[0052] 3) Age Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3 at 120 °C for 24 hours, conduct demulsification dehydration experiments, and record the water separation amounts and interface conditions before and after aging respectively.

[0053] III. Analysis of the test results of each example I. Perform TEM testing on the carbon dot materials prepared in Example 1. The results are as shown in the appendix Figure 2 As shown, combined with the appendix Figure 1 It can be seen that the average diameter of the carbon dot materials prepared in Example 1 of this application is 3.22 ± 1.00 nm, with obvious lattice fringes. The lattice fringe spacing is 0.34 nm, corresponding to the lattice fringe spacing of graphene, indicating that the above preparation method of this application can prepare nanometer particles with a layered structure matching that of the appendix Figure 1 Perform TEM testing on the carbon dot materials prepared in Comparative Example 3. The results are as shown in the appendix Figure 3 As shown, it can be seen that the carbon dots prepared in Comparative Example 3 of this application are amorphous carbon materials, different from the carbon dot materials prepared in Example 1, and do not have a special layered structure.

[0054] II. Conduct dehydration experiments on the nano-demulsifier prepared in Example 1 at different concentrations. The results are as shown in Figure 4 As shown, Figure 4 The concentrations of the nano-demulsifier used in Figure 4 from left to right are: 0 mg / L, 10 mg / L, 25 mg / L, 50 mg / L, 75 mg / L, 100 mg / L. It can be seen from

[0055] III. The dehydration experiment results of the demulsifiers prepared in Examples 1 - 5 and Comparative Examples 1 - 3 at 50°C are shown in Table 1 as follows: Table 1 Dehydration experiment results of different demulsifiers at 50°C

[0056] As can be seen from Table 1, the dehydration effect of the nano - demulsifiers prepared in Examples 1 - 5 of this application is significantly better than that of the demulsifiers prepared by the existing process in Comparative Examples 1 - 2 and the demulsifiers prepared based on the amorphous - structured carbon materials in Comparative Example 3. This shows that by using the carbon dot material with a layered structure as an initiator and introducing carbon dot materials with polyhydroxy and hydrophobic groups on the surface in this application, the branching degree of polyether can be effectively improved, enabling the prepared nano - demulsifier to form strong interactions with naphthenes, asphaltenes, and resins in the crude oil composition, and significantly enhancing the low - temperature oil - water separation efficiency of crude oil emulsions; among them, the performance of Example 5 is better.

[0057] IV. The dehydration experiment results of Examples 1 - 2 and Comparative Examples 1 - 3 before and after aging at 120°C for 24 h are shown in Table 2 as follows: Table 2 Dehydration experiment results of different demulsifiers before and after aging at 120°C for 24 h

[0058] As can be seen from Table 2, there are no obvious changes in the water - removal amount and interface situation of Examples 1 - 2 before and after aging at 120°C for 24 h, while the water - removal amount of Comparative Examples 1 - 3 decreases significantly before and after aging at 120°C for 24 h. This proves that the carbon dot material synthesized in this application has high chemical stability, and the prepared nano - demulsifier has better high - temperature resistance compared with the existing demulsifiers and the demulsifiers prepared based on the amorphous - structured carbon materials.

[0059] It should be noted that the above - mentioned embodiments all belong to the same inventive concept. The descriptions of the embodiments have their own emphases. For the parts not described in detail in individual embodiments, reference can be made to the descriptions in other embodiments.

[0060] The above - mentioned embodiments only represent the implementation manners of this application. The descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can still be made, and these all belong to the protection scope of this application. Therefore, the protection scope of this application patent should be subject to the appended claims.

Claims

1. A nano demulsifier, characterized in that, The nano-demulsifier is prepared by a polymerization reaction of carbon dot materials, propylene oxide, ethylene oxide and a catalyst; The carbon dot material is nanoparticles formed by stacking of layered structures, in which carbon atoms in any layered structure are arranged in a regular hexagon array, and hydroxyl groups for polymerization reaction with propylene oxide and / or ethylene oxide are present at the edge of any layered structure.

2. The nano-demulsifier 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 to 10 nm.

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

4. A preparation method of the nano demulsifier according to any one of claims 1 to 3, characterized in that, It includes the following steps: S1. Mix sucrose with a surfactant and carry out a pyrolysis reaction to obtain carbon dot materials; S2. Mix the carbon dot materials, propylene oxide, ethylene oxide and a catalyst and carry out a polymerization reaction to obtain the nano-demulsifier.

5. The preparation method of the nano demulsifier according to claim 4, characterized in that, The specific steps of the S1 step are as follows: S11. After mixing sucrose with a surfactant, carry out a pyrolysis reaction at 160°C to 220°C for 12 h to 18 h to obtain initial carbon dots; S12. Mix the initial carbon dots and water in a mass ratio of 1:1 to prepare an aqueous carbon dot solution, and obtain the carbon dot materials after freeze-drying.

6. The preparation method of the nano demulsifier according to claim 5, characterized in that, The mass ratio of sucrose to the surfactant is 1:4 to 4:1; The surfactant includes at least one of Tween80, Tween20, Tween21, Tween40, Tween60, Tween61 and Tween81.

7. The preparation method of the nano demulsifier according to claim 4, characterized in that, The catalyst includes a first catalyst and a second catalyst, and both the first catalyst and the second catalyst are selected from any one of barium laurate, sodium hydroxide and potassium hydroxide; The specific steps of the S2 step are as follows: S21. Add the first catalyst to the carbon dot materials, heat to 60°C and evacuate to -0.01 MPa, then raise the temperature to 115°C to 125°C, intermittently add propylene oxide and maintain the ambient pressure less than 0.2 MPa. After the feeding is completed, continue the reaction until the ambient pressure drops to -0.01 MPa to obtain a polyether propylene oxide block polymer; S22. Add the second catalyst to the polyether propylene oxide block polymer, heat to 60°C and evacuate to -0.01 MPa, then raise the temperature to 85°C to 95°C, intermittently add ethylene oxide and maintain the ambient pressure less than 0.4 MPa. After the feeding is completed, continue the reaction until the ambient pressure drops to -0.01 MPa to obtain the nano-demulsifier.

8. The preparation method of the nano demulsifier according to claim 7, 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.

9. The preparation method of the nano demulsifier according to claim 7, characterized in that The mass ratio of the carbon dot material, the first catalyst and the second catalyst is 1:(1 to 2):(0.5 to 1).

10. Application of the nano-demulsifier according to any one of claims 1 to 3 as a demulsifier for oilfield produced fluids.

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