A reverse demulsifier, its preparation method and application

Abstract

The application belongs to the technical field of petroleum industry, and relates to a reverse demulsifier and a preparation method and application thereof. The reverse demulsifier comprises structural units derived from cationic unsaturated monomers, structural units derived from polyhydroxy structural monomers, structural units derived from acrylamide monomers, structural units derived from end group double bond containing aromatic hydrophobic monomers and structural units derived from crosslinkable monomers. The acrylamide cationic copolymer provided by the application contains cationic groups, polyhydroxy structures and hydrophobic functional groups containing benzene rings, can be quickly adsorbed to the oil-water interface, improves the interface adsorption and coiling and sweeping coalescence performance, reduces the oil-water interface stability and the electrostatic repulsion between oil droplets, has a fast dehydration speed, a strong water purification capacity, a very good treatment effect on complex oily sewage, clear water after dehydration, low solid suspended particle and oil content, and meets the oilfield reinjection or discharge requirements.

Description

Technical Field

[0001] This invention belongs to the field of petroleum industry technology, specifically relating to a reverse demulsifier, its preparation method, and its application. Background Technology

[0002] With the large-scale development of unconventional oil fields such as shale oil and heavy oil in my country, the properties of produced water from oil fields are becoming increasingly complex, characterized by high viscosity, high content of oil droplets and suspended solids, and strong emulsification stability, making demulsification and dehydration extremely difficult.

[0003] Cationic reverse demulsifiers are currently the main type of reverse demulsifiers used in oily wastewater treatment. Among them, cationic polyacrylamide is a widely used wastewater treatment agent. The O / W emulsion interface of produced water generally has negative charge. Cationic groups can neutralize the negative charge at the oil-water interface, compress and destroy the double layer, reduce the electrostatic repulsion between oil droplets, bridge oil droplets, and enhance the ability of oil droplets to coalesce, thereby achieving the purpose of demulsification and oil removal.

[0004] Existing cationic reverse demulsifiers struggle to meet the complex requirements of produced water treatment, particularly for organic-based impurities. Treatment often results in excessive oil and suspended solids levels, impacting subsequent discharge and reinjection. Therefore, there is an urgent need to develop a novel, highly efficient water-purifying reverse demulsifier to address the increasing complexity of oilfield produced water and ensure continuous and stable oilfield production. Summary of the Invention

[0005] The purpose of this invention is to address the deficiencies and shortcomings of existing technologies by providing a highly efficient water-purifying reverse demulsifier and its preparation method. It is prepared by micellar polymerization of acrylamide monomers with cationic unsaturated monomers, polyhydroxyl monomers, and hydrophobic monomers containing benzene rings. This method can further improve the demulsification and dehydration speed and water purification capacity of the reverse demulsifier, and it is effective in demulsifying, removing oil, and removing suspended solid particles from complex oily wastewater.

[0006] To achieve the above objectives, a first aspect of the present invention provides a reverse demulsifier, the reverse demulsifier comprising structural units derived from cationic unsaturated monomers, structural units derived from polyhydroxy structural monomers, structural units derived from acrylamide monomers, structural units derived from aromatic hydrophobic monomers with double bonds at the ends, and structural units derived from crosslinkable monomers.

[0007] A second aspect of the present invention provides a method for preparing the aforementioned reverse demulsifier, comprising the following steps:

[0008] A cationic unsaturated monomer, a polyhydroxy monomer, an acrylamide monomer, an aromatic hydrophobic monomer with a double bond at the end group, and a crosslinkable monomer are mixed, heated to the polymerization temperature, and an initiator is added dropwise to carry out the reaction, thereby obtaining the reverse demulsifier.

[0009] A third aspect of the present invention provides the application of the aforementioned reverse demulsifier in the treatment of produced water in oilfields.

[0010] The beneficial effects of this invention are as follows:

[0011] The acrylamide cationic copolymer provided by this invention, containing cationic groups, polyhydroxy structures, and hydrophobic functional groups containing benzene rings, can be rapidly adsorbed onto the oil-water interface, improving interfacial adsorption and sweeping aggregation performance, reducing oil-water interface stability and electrostatic repulsion between oil droplets, resulting in fast dehydration speed, strong water purification capacity, and excellent treatment effect on complex oily wastewater. The dehydrated water is clear with low levels of solid suspended particles and oil content, meeting the requirements for oilfield reinjection or discharge.

[0012] This invention uses micellar polymerization, which involves no toxic or harmful solvents, generates no waste, is environmentally friendly and energy-efficient, and has a safe, gentle and easy-to-operate production process.

[0013] The reverse demulsifier provided by this invention can be used alone or in combination with other existing reverse demulsifiers or flocculants, depending on the properties of the produced oil-in-water emulsion, to improve the versatility of the reverse demulsifier.

[0014] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0015] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0016] To achieve the above objectives, a first aspect of the present invention provides a reverse demulsifier, the reverse demulsifier comprising structural units derived from cationic unsaturated monomers, structural units derived from polyhydroxy structural monomers, structural units derived from acrylamide monomers, structural units derived from aromatic hydrophobic monomers with double bonds at the ends, and structural units derived from crosslinkable monomers.

[0017] According to the present invention, preferably, based on the total weight of all structural units in the reverse demulsifier, the content of structural units derived from cationic unsaturated monomers is 15-50 wt%, preferably 25-40 wt%; the content of structural units derived from polyhydroxy structural monomers is 5-20 wt%, preferably 10-15 wt%; the content of structural units derived from acrylamide monomers is 30-65 wt%, preferably 40-55 wt%; the content of structural units derived from aromatic hydrophobic monomers with double bonds at the ends is 2-12 wt%, preferably 5-10 wt%; and the content of structural units derived from crosslinkable monomers is 0.001-1 wt%, preferably 0.01-0.3 wt%.

[0018] According to the present invention, preferably, the structural formulas of cationic unsaturated monomers are shown in Formula A, the structural formulas of polyhydroxy monomers are shown in Formula B, the structural formulas of acrylamide monomers are shown in Formula C, and the structural formulas of aromatic hydrophobic monomers with double bonds at the ends are shown in Formula D.

[0019]

[0020] In formula A, R1 is H or a C1-C10 alkyl group, preferably H or a C1-C3 alkyl group; R2 is selected from C1-C10 alkylene groups, preferably C1-C5 alkylene groups, more preferably C1-C2 alkylene groups; R3, R4, and R5 are each independently selected from C1-C10 alkyl groups, preferably C1-C5 alkyl groups, more preferably methyl groups; X is a halogen, preferably Cl or Br.

[0021] In formula B, R6 is an H or C1-C10 alkyl group, preferably an H or C1-C3 alkyl group, and R7, R8, and R9 are each independently selected from C1-C10 alkylene groups, preferably from C1-C5 alkylene groups;

[0022] In formula C, R 10 It is an H or C1-C10 alkyl group, preferably an H or C1-C3 alkyl group;

[0023] In formula D, R 11 It is an alkyl group of H or C1-C10, preferably an alkyl group of H or C1-C3.

[0024] According to the present invention, preferably, the cationic unsaturated monomer is acryloyloxyethyltrimethylammonium chloride and / or methacryloyloxyethyltrimethylammonium chloride;

[0025] The polyhydroxy monomer is trimethylolpropionamide (R7, R8 and R9 are the same and are all methylene, and R6 is H);

[0026] The acrylamide monomer is acrylamide and / or methacrylamide;

[0027] The aromatic hydrophobic monomer with a double bond at the end group is methyl 4-acrylamide benzoate and / or methyl 4-methylacrylamide benzoate.

[0028] According to the present invention, preferably, the crosslinkable monomer is an olefin compound containing two or more unsaturated double bonds, and is preferably selected from at least one of N,N'-methylenebisacrylamide, trimethylolpropionic acid triacrylate, diethylene glycol dimethacrylate, butanediol dimethacrylate, butanediol diacrylate, and divinylbenzene.

[0029] A second aspect of the present invention provides a method for preparing the aforementioned reverse demulsifier, comprising the following steps:

[0030] A cationic unsaturated monomer, a polyhydroxy monomer, an acrylamide monomer, an aromatic hydrophobic monomer with a double bond at the end group, and a crosslinkable monomer are mixed, heated to the polymerization temperature, and an initiator is added dropwise to carry out the reaction, thereby obtaining the reverse demulsifier.

[0031] According to the present invention, preferably, the amounts of the cationic unsaturated monomer, polyhydroxy structural monomer, acrylamide monomer, aromatic hydrophobic monomer with double bonds at the ends, and crosslinkable monomer are such that, based on the total weight of all structural units in the reverse demulsifier, the content of structural units derived from the cationic unsaturated monomer is 15-50 wt%, preferably 25-40 wt%; the content of structural units derived from the polyhydroxy structural monomer is 5-20 wt%, preferably 10-15 wt%; the content of structural units derived from the acrylamide monomer is 30-65 wt%, preferably 40-55 wt%; the content of structural units derived from the aromatic hydrophobic monomer with double bonds at the ends is 2-12 wt%, preferably 5-10 wt%; and the content of structural units derived from the crosslinkable monomer is 0.001-1 wt%, preferably 0.01-0.3 wt%.

[0032] According to the present invention, preferably, the preparation method is micellar polymerization, comprising the following steps:

[0033] (1) Mix the cationic unsaturated monomer, the polyhydroxyl monomer, the acrylamide monomer and the solvent to obtain a stable solution;

[0034] (2) Add aromatic hydrophobic monomers with double bonds at the end groups, crosslinkable monomers and emulsifiers to a stable solution and stir thoroughly to form stable micelles;

[0035] (3) Heat to the polymerization temperature, add initiator dropwise to react, and obtain the reverse demulsifier.

[0036] The essential difference between this invention and the prior art lies in:

[0037] Acrylamide monomers, along with cationic unsaturated monomers, polyhydroxy acrylamide monomers, aromatic hydrophobic monomers with double bonds at the ends, and crosslinkable monomers, are polymerized via micellar polymerization to incorporate cationic groups, polyhydroxy structures, and hydrophobic functional groups containing benzene rings into the molecular chain segments. The polyhydroxy structure can regulate hydrophilicity and lipophilicity, reducing the stability of the oil-water interface and facilitating rapid and efficient demulsification. The hydrophobic functional groups can associate and solubilize with hydrophobic organic substances in oily wastewater and interact with hydrophobic oil droplets, enhancing bridging and demulsification. This results in better demulsification and dehydration, a clearer oil-water interface, and a high oil removal rate.

[0038] According to the present invention, preferably, the solvent is deionized water;

[0039] The emulsifier is selected from at least one of sodium dodecyl sulfate, sodium dodecyl sulfonate, hexadecyltrimethylammonium bromide, sodium alkylbenzene sulfonate, alkylphenol polyoxyethylene ether (such as OP-10), and sorbitan oleate (such as Span-80);

[0040] The initiator is a persulfate oxidant and / or a sulfite reducing agent, preferably selected from at least one of potassium persulfate, ammonium persulfate, potassium bisulfite, and sodium bisulfite.

[0041] According to the present invention, preferably, the total weight of the reactants is the total weight of the cationic unsaturated monomer, the polyhydroxy monomer, the acrylamide monomer, the aromatic hydrophobic monomer with a double bond at the end group, and the crosslinkable monomer; the amount of solvent added is 2 to 5 times the total weight of the reactants, preferably 3 to 4 times; the amount of emulsifier added is 1 to 6 wt% of the total weight of the reactants, preferably 2 to 4 wt%; and the amount of initiator added is 0.05 to 1 wt% of the total mass of the reactants, preferably 0.2 to 0.6 wt%.

[0042] In this invention, the persulfate oxidant and the sulfite reducing agent are introduced into the polymerization system in the form of aqueous solutions. More preferably, the persulfate oxidant is a 2% (w / w) aqueous solution of potassium persulfate and / or ammonium persulfate; and the sulfite reducing agent is a 1% (w / w) aqueous solution of potassium bisulfite and / or sodium bisulfite.

[0043] According to the present invention, preferably, the polymerization temperature is 30-60°C and the reaction time is 3-5 hours.

[0044] A third aspect of the present invention provides the application of the aforementioned reverse demulsifier in the treatment of produced water in oilfields.

[0045] The present invention will be further described below with reference to the embodiments, but the scope of the present invention is not limited to these embodiments.

[0046] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified were either readily available or prepared using methods disclosed in the prior art. Unless otherwise stated, all reagents used were commercially available chemically pure reagents, and identical products originated from the same source.

[0047] Example 1

[0048] Operating steps:

[0049] Step 1: Weigh 15g of methacryloyloxyethyltrimethylammonium chloride, 6g of trimethylolpropionic acid, and 22g of acrylamide and add them to a three-necked flask containing 150g of deionized water. Stir thoroughly to dissolve and obtain a stable aqueous solution.

[0050] Step 2: Weigh 4 g of methyl 4-acrylamide benzoate, 0.1 g of crosslinkable monomer N,N'-methylenebisacrylamide and 1.5 g of emulsifier Tween 60, add them to the above aqueous solution, and stir thoroughly to form stable micelles;

[0051] Step 3: Heat the reaction system to 50°C, continuously purge with nitrogen, and simultaneously add 5g of 2wt% potassium persulfate aqueous solution and 5g of 1wt% sodium bisulfite aqueous solution at a uniform rate. The addition is completed in 1 hour.

[0052] Step 4: Continue the reaction at a constant temperature for 3-5 hours. After stopping the reaction, reduce the temperature to room temperature and discharge the material to obtain the reverse demulsifier.

[0053] Example 2

[0054] Operating steps:

[0055] Step 1: Weigh 22g of methacryloyloxyethyltrimethylammonium chloride, 7g of trimethylolpropionic acid, and 24g of acrylamide and add them to a three-necked flask containing 185g of deionized water. Stir thoroughly to dissolve and obtain a stable aqueous solution.

[0056] Step 2: Weigh 5 g of methyl 4-acrylamide benzoate, 0.12 g of crosslinkable monomer N,N'-methylenebisacrylamide and 1.8 g of emulsifier Tween 60, add them to the above aqueous solution, and stir thoroughly to form stable micelles;

[0057] Step 3: Heat the reaction system to 50°C, continuously purge with nitrogen, and simultaneously add 6g of 2wt% potassium persulfate aqueous solution and 6g of 1wt% sodium bisulfite aqueous solution at a uniform rate. The addition is completed in 1 hour.

[0058] Step 4: Continue the reaction at a constant temperature for 3-5 hours. After stopping the reaction, reduce the temperature to room temperature and discharge the material to obtain the reverse demulsifier.

[0059] Example 3

[0060] Operating steps:

[0061] Step 1: Weigh 12g of methacryloyloxyethyltrimethylammonium chloride, 5.5g of trimethylolpropionic acid, and 24g of acrylamide and add them to a three-necked flask containing 150g of deionized water. Stir thoroughly to dissolve and obtain a stable aqueous solution.

[0062] Step 2: Weigh 3.5 g of methyl 4-acrylamide benzoate, 0.1 g of crosslinkable monomer N,N'-methylenebisacrylamide and 1.5 g of emulsifier Tween 60, add them to the above aqueous solution, and stir thoroughly to form stable micelles;

[0063] Step 3: Heat the reaction system to 50°C, continuously purge with nitrogen, and simultaneously add 5g of 2wt% potassium persulfate aqueous solution and 5g of 1wt% sodium bisulfite aqueous solution at a uniform rate. The addition is completed in 1 hour.

[0064] Step 4: Continue the reaction at a constant temperature for 3-5 hours. After stopping the reaction, reduce the temperature to room temperature and discharge the material to obtain the reverse demulsifier.

[0065] Example 4

[0066] The only difference from Example 1 is that 2.5 g of methyl 4-acrylamide benzoate is added in step 2.

[0067] Example 5

[0068] The only difference from Example 1 is that 4.5 grams of methyl 4-acrylamide benzoate is added in step 2.

[0069] Example 6

[0070] The only difference from Example 1 is that 5 grams of trimethylolpropionic acid was added in step 1.

[0071] Example 7

[0072] The only difference from Example 1 is that 7 grams of trimethylolpropionic acid was added in step 1.

[0073] Example 8

[0074] The only difference from Example 3 is that 8 grams of methacryloyloxyethyltrimethylammonium chloride, 3 grams of trimethylolpropionic acid, and 31.5 grams of acrylamide were added in step 1, and 2 grams of methyl 4-acrylamide benzoate were added in step 2.

[0075] Comparative Example 1

[0076] Operating steps:

[0077] Step 1: Weigh 17 g of methacryloyloxyethyltrimethylammonium chloride and 24 g of acrylamide and add them to a three-necked flask containing 145 g of deionized water. Stir thoroughly to dissolve and obtain a stable aqueous solution.

[0078] Step 2: Weigh 4 g of methyl 4-acrylamide benzoate, 0.1 g of crosslinkable monomer N,N'-methylenebisacrylamide and 1.5 g of emulsifier Tween 40, add them to the above aqueous solution, and stir thoroughly to form stable micelles;

[0079] Step 3: Heat the reaction system to 50°C, continuously purge with nitrogen, and simultaneously add 5g of 2wt% potassium persulfate aqueous solution and 5g of 1wt% sodium bisulfite aqueous solution at a uniform rate. The addition is completed in 1 hour.

[0080] Step 4: Continue the reaction at a constant temperature for 3-5 hours. After stopping the reaction, reduce the temperature to room temperature and discharge the material to obtain the reverse demulsifier.

[0081] Comparative Example 2

[0082] Operating steps:

[0083] Step 1: Weigh 17 g of methacryloyloxyethyltrimethylammonium chloride, 6 g of trimethylolpropionic acid, 24 g of acrylamide, and 0.1 g of N,N'-methylenebisacrylamide and add them to a three-necked flask containing 155 g of deionized water. Stir thoroughly to dissolve and obtain a stable aqueous solution.

[0084] Step 2: Heat the reaction system to 50°C, continuously purge with nitrogen, and simultaneously add 5g of 2wt% potassium persulfate aqueous solution and 5g of 1wt% sodium bisulfite aqueous solution at a uniform rate. The addition is completed in 1 hour.

[0085] Step 3: Continue the reaction at a constant temperature for 3-5 hours. After stopping the reaction, reduce the temperature to room temperature and discharge the material to obtain the reverse demulsifier.

[0086] Comparative Example 3

[0087] The only difference from Example 1 is that no crosslinkable monomer is added in step 1.

[0088] Comparative Example 4

[0089] SF-Y001 type cationic polyacrylamide, produced by Wenxian Sifang Water Treatment Materials Co., Ltd.

[0090] Test Example 1

[0091] The performance testing of reverse demulsifiers was conducted according to petroleum industry standards SY / T0530-93, SY / T5797-93, SY / T5329-94, and Q / SH1020 1516-2012. The bottle test method was used to observe and record the oil-water phase and interface conditions; the oil content in wastewater was tested using a UV spectrophotometer; and the suspended solids particle content was tested using a filtration experimental setup.

[0092] Examples 1-7 and Comparative Examples 1-4 were added to the oil production wastewater of the Chengdong Joint Station of the Hekou Oilfield. The wastewater contained 265 mg / L of oil and 97 mg / L of suspended solids. The concentration of the reverse demulsifier was 15 mg / L. The reaction was carried out at 50°C for 0.5 hours, and the results were observed and tested according to industry standards.

[0093] The performance of the examples and comparative examples is shown in Table 1.

[0094] Table 1 Performance Evaluation of Reverse Demulsifiers

[0095]

[0096]

[0097] The test results show that Examples 1-7 have better demulsification, oil removal, and solid suspended particle removal capabilities, and their treatment effect on oilfield wastewater from the Chengdong Joint Station of Shengli Oilfield is significantly better than that of Comparative Examples 1-4. Specifically, Comparative Example 1 did not contain polyhydroxyl monomers, and Comparative Example 2 did not contain hydrophobic functional monomers, resulting in a significant decrease in oil removal rate and a slight decrease in solid suspension removal compared to Example 1. Comparative Example 3 did not contain crosslinkable monomers, had a narrower molecular weight distribution, fewer branches, and weakened bridging and flocculation capabilities, leading to a decrease in both oil removal rate and solid suspension removal rate. Compared to Example 3, Example 2 had a lower cationic monomer content, reduced ability to neutralize negative charges, and decreased solid suspension removal capability. Example 8 had a high acrylamide monomer content and low content of other monomers, with the monomer ratio not within the optimal range, resulting in a significant decrease in both oil removal and solid suspension removal effects.

[0098] This invention combines specific components such as cationic groups, polyhydroxy structures, and hydrophobic functional groups containing benzene rings to achieve synergistic effects and achieve better results. The absence of any one component will prevent the improvement of oil and solids removal performance of complex produced water as described in this application. The dosage of each component within the specific range of this application results in better performance of the reverse demulsifier.

[0099] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0100] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A reverse demulsifier, characterized in that, The reverse demulsifier comprises structural units derived from cationic unsaturated monomers, structural units derived from polyhydroxy monomers, structural units derived from acrylamide monomers, structural units derived from aromatic hydrophobic monomers with double bonds at the ends, and structural units derived from crosslinkable monomers.

2. The reverse demulsifier according to claim 1, wherein, Based on the total weight of all structural units in the reverse demulsifier, the content of structural units derived from cationic unsaturated monomers is 15-50 wt%, preferably 25-40 wt%; the content of structural units derived from polyhydroxy monomers is 5-20 wt%, preferably 10-15 wt%; the content of structural units derived from acrylamide monomers is 30-65 wt%, preferably 40-55 wt%; the content of structural units derived from aromatic hydrophobic monomers with double bonds at the ends is 2-12 wt%, preferably 5-10 wt%; and the content of structural units derived from crosslinkable monomers is 0.001-1 wt%, preferably 0.01-0.3 wt%.

3. The reverse demulsifier according to claim 1, wherein, The structural formulas of cationic unsaturated monomers are shown in Formula A, the structural formulas of polyhydroxy monomers are shown in Formula B, the structural formulas of acrylamide monomers are shown in Formula C, and the structural formulas of aromatic hydrophobic monomers with double bonds at the ends are shown in Formula D. In formula A, R1 is H or a C1-C10 alkyl group, preferably H or a C1-C3 alkyl group; R2 is a C1-C10 alkylene group, preferably a C1-C5 alkylene group, more preferably a C1-C2 alkylene group; R3, R4, and R5 are each independently selected from C1-C10 alkyl groups, preferably from C1-C5 alkyl groups, more preferably methyl groups; and X is a halogen, preferably Cl or Br. In formula B, R6 is an H or C1-C10 alkyl group, preferably an H or C1-C3 alkyl group, and R7, R8, and R9 are each independently selected from C1-C10 alkylene groups, preferably from C1-C5 alkylene groups; In formula C, R 10 It is an H or C1-C10 alkyl group, preferably an H or C1-C3 alkyl group; In formula D, R 11 It is an alkyl group of H or C1-C10, preferably an alkyl group of H or C1-C3.

4. The reverse demulsifier according to claim 3, wherein, The cationic unsaturated monomer is acryloyloxyethyltrimethylammonium chloride and / or methacryloyloxyethyltrimethylammonium chloride; The polyhydroxy monomer is trimethylolpropionamide; The acrylamide monomer is acrylamide and / or methacrylamide; The aromatic hydrophobic monomer with a double bond at the end group is methyl 4-acrylamide benzoate and / or methyl 4-methylacrylamide benzoate.

5. The reverse demulsifier according to claim 1, wherein, The crosslinkable monomer is an olefin compound containing two or more unsaturated double bonds, preferably selected from at least one of N,N'-methylenebisacrylamide, trimethylolpropionic acid triacrylate, diethylene glycol dimethacrylate, butanediol dimethacrylate, butanediol diacrylate, and divinylbenzene.

6. A method for preparing the reverse demulsifier according to any one of claims 1-5, characterized in that, Includes the following steps: A cationic unsaturated monomer, a polyhydroxy monomer, an acrylamide monomer, an aromatic hydrophobic monomer with a double bond at the end group, and a crosslinkable monomer are mixed, heated to the polymerization temperature, and an initiator is added dropwise to carry out the reaction, thereby obtaining the reverse demulsifier.

7. The preparation method according to claim 6, wherein, The preparation method is micellar polymerization, which includes the following steps: (1) Mix the cationic unsaturated monomer, the polyhydroxyl monomer, the acrylamide monomer and the solvent to obtain a stable solution; (2) Add aromatic hydrophobic monomers with double bonds at the end groups, crosslinkable monomers and emulsifiers to a stable solution and stir thoroughly to form stable micelles; (3) Heat to the polymerization temperature, add initiator dropwise to react, and obtain the reverse demulsifier.

8. The preparation method according to claim 7, wherein, The solvent is deionized water; The emulsifier is selected from at least one of sodium dodecyl sulfate, sodium dodecyl sulfonate, hexadecyltrimethylammonium bromide, sodium alkylbenzene sulfonate, alkylphenol polyoxyethylene ether, and sorbitan anhydride oleate. The initiator is a persulfate oxidant and / or a sulfite reducing agent, preferably selected from at least one of potassium persulfate, ammonium persulfate, potassium bisulfite, and sodium bisulfite.

9. The preparation method according to claim 7, wherein, The total weight of the reactants is defined as the total weight of the cationic unsaturated monomers, polyhydroxy monomers, acrylamide monomers, aromatic hydrophobic monomers with double bonds at the ends, and crosslinkable monomers. The amount of solvent added is 2 to 5 times the total weight of the reactants, preferably 3 to 4 times. The amount of emulsifier added is 1 to 6 wt% of the total weight of the reactants, preferably 2 to 4 wt%. The amount of initiator added is 0.05 to 1 wt% of the total mass of the reactants, preferably 0.2 to 0.6 wt%.

10. The preparation method according to claim 7, wherein, The polymerization temperature is 30–60°C, and the reaction time is 3–5 hours.

11. The application of the reverse demulsifier according to any one of claims 1-5 or the reverse demulsifier prepared by the preparation method according to any one of claims 6-10 in the treatment of produced water in oilfields.

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