Demulsifier with reverse demulsification function and preparation method thereof

Abstract

This invention relates to the field of oilfield technology, and more particularly to a demulsifier with reverse demulsification function and its preparation method. This emulsion is made of a specific polymer linked to crown ether groups, and exhibits highly efficient demulsification and dehydration performance on crude oil emulsions, especially oil-in-water emulsions, with a faster demulsification rate and better demulsification effect on stubborn emulsions. It particularly demonstrates excellent demulsification ability for reverse (O / W) emulsions formed by high-salinity water. The method uses mild reaction conditions, readily available raw materials, simple post-processing, and the structure and molecular weight of the product are easily controlled.

Description

Technical Field

[0001] This invention relates to the field of oil extraction technology, specifically to a demulsifier with reverse demulsification function and its preparation method. Background Technology

[0002] During crude oil extraction and gathering, oil-in-water (O / W) or water-in-oil (W / O) emulsions are often formed. Among these, the treatment of reverse emulsions (usually O / W type) is one of the challenges in oilfield chemistry. Traditional demulsifiers, such as surfactants based on polyethers and polyesters, have limited effectiveness in demulsifying certain stable emulsions, especially those containing highly salinized water, resulting in slow dehydration rates and low water yields.

[0003] Crown ether compounds, due to their unique cyclic cavity structure, can selectively complex metal cations (such as Na+). + Mg + Ca + K + This property, if applied to demulsifier design, is expected to efficiently disrupt emulsions, especially those formed from highly mineralized water, by disrupting the ion balance on the interfacial film of emulsion droplets or by directly interacting with interfacial substances. However, effectively introducing and immobilizing crown ether groups on a suitable polymer backbone to prepare demulsifiers with good water solubility / dispersibility, interfacial activity, and specific ion responsiveness remains a technical challenge.

[0004] Therefore, developing a novel, efficient demulsifier with excellent demulsification properties, especially for reverse emulsions, and its simple preparation method is of great industrial application value. Summary of the Invention

[0005] To address the above-mentioned technical problems, this invention provides a demulsifier with reverse demulsification function and its preparation method. This emulsifier, with crown ether groups linked to both ends of a specific polymer backbone, exhibits highly efficient demulsification and dehydration performance for crude oil emulsions, especially oil-in-water emulsions. Another objective of this invention is to provide a method for preparing the above-mentioned demulsifier, which is characterized by mild conditions, simple steps, and easy control.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a demulsifier with reverse demulsification function, the structure of which is shown in formula (I):

[0008] Formula (I),

[0009] In equation (I), n represents the degree of aggregation, which ranges from 200 to 400.

[0010] The demulsifier of this invention is a polyacrylamide-based demulsifier with crown ether groups linked by amide bonds, and can be simply referred to as crown ether-P(AM). This demulsifier has a unique molecular structure that incorporates metal ions (Na+). + Mg + Ca + K + The crown ether group, which has recognition function, is chemically bonded to the polyacrylamide chain, forming a "crown ether-hydrophilic chain" structure. The crown ether group of this demulsifier can chelate metal cations, disrupting the charge shielding effect of the oil-water interface film. The polymer chain not only has a flocculation effect but also provides steric hindrance, comprehensively achieving synergistic demulsification through "charge neutralization and interface film penetration." In particular, the crown ether group can specifically complex metal cations (Na+) at the oil-in-water emulsion interface. + Mg + Ca + K + (etc.), quickly neutralize the charge at the oil-water interface, weaken the repulsive force between droplets, thereby promoting droplet coalescence, effectively disrupting the stability of the water-in-oil emulsion interface film, and achieving reverse demulsification; in addition, the rigid ring structure of crown ether is less deformable than the flexible polyether chain, and as the lipophilic part of the demulsifier, it can be more firmly adsorbed on the oil-water interface, effectively replacing the natural emulsifier molecules originally adsorbed on the oil-water interface, forming a more fragile and unstable new interface film, reducing the mechanical strength of the interface film, making water droplets more likely to collide and coalesce, thus giving the demulsifier of the present invention a faster demulsification speed, better demulsification effect on stubborn emulsions, especially showing excellent demulsification ability for reverse (O / W) emulsions formed by high-mineralized water.

[0011] Secondly, the present invention also provides a method for preparing the above-mentioned demulsifier, comprising the following steps:

[0012] S1. Under N2 protection and stirring, acrylamide solution and polyethylene glycol solution are mixed evenly, and then initiator solution is added dropwise and mixed evenly. The temperature is raised to 60℃-70℃ and the reaction is maintained for 6h-8h. After cooling to room temperature, a reaction solution is obtained. The reaction solution is poured into cold acetone to precipitate. After filtration, the solid is washed and dried to obtain intermediate 1.

[0013] S2. Under N2 protection, with stirring, at room temperature, add N-hydroxysuccinimide and triethylamine to the intermediate 1 solution and react for at least 10 min. Then add carbodiimide and react for at least 30 min to obtain an activated solution. Add an amino crown ether solution dropwise to the activated solution and react for 24-48 h to obtain the target solution. Pour the target solution into a solvent to precipitate, and after solid-liquid separation, wash the solid and dry it to obtain crown ether-P(AM).

[0014] The demulsifier of the present invention is prepared by a two-step method. First, acrylamide AM, 4,4'-azobis(4-cyanopentanoic acid), and polyethylene glycol, a chain transfer agent, are subjected to free radical polymerization to obtain a carboxyl-terminated polyacrylamide homopolymer with 4-cyanopentanoic acid as the end group, namely intermediate 1, the structure of which is shown in formula (II):

[0015] Equation (II).

[0016] Secondly, intermediate 1 is subjected to an amidation reaction with an amino crown ether via an activated ester method to obtain the demulsifier crown ether-P(AM). This method has mild reaction conditions, readily available raw materials, simple post-processing, and the structure and molecular weight of the product are easy to control.

[0017] Preferably, in step S1, the molar ratio of polyethylene glycol to acrylamide is 1:2-3. This molar ratio of polyethylene glycol to acrylamide allows polyethylene glycol to act as a chain transfer agent to control the growth of the polymer chain, but polyethylene glycol hardly polymerizes onto the polymer chain. Finally, the polyethylene glycol is removed by washing with cold acetone.

[0018] Preferably, in step S1, the acrylamide solution is prepared by dissolving acrylamide in pure water, with 0.20 mmol to 0.30 mmol of acrylamide added to every 40 mL of pure water.

[0019] The polyethylene glycol solution is prepared by dissolving polyethylene glycol in pure water, with 0.10 mmol-0.20 mmol of polyethylene glycol added to every 60 mL of pure water; polyethylene glycol also serves as a reaction medium, providing a homogeneous reaction environment and influencing polymerization kinetics through chain transfer.

[0020] The initiator solution is prepared by dissolving the initiator in pure water, with 0.010 g to 0.015 g of initiator added to every 5 mL of pure water.

[0021] Preferably, in step S1, the initiator is 4,4'-azobis(4-cyanopentanoic acid) (ACVA), a water-soluble azo initiator that can avoid the accelerating effect in traditional RAFT (reversible addition-fracture transfer) polymerization and avoid the broadening of molecular weight distribution and uncontrolled polymerization in traditional polymerization reactions.

[0022] The volume ratio of reaction solution to cold acetone is 1:(5-10).

[0023] In steps S1 and S2, the stirring rate of the state stirring is 300 rpm-500 rpm;

[0024] Step S1, the drying is vacuum drying at 40℃-45℃ for 24 h-48 h.

[0025] Preferably, in step S2, the intermediate 1 solution is prepared by dissolving intermediate 1 in anhydrous N,N-dimethylformamide;

[0026] Preferably, 5.0 mg to 10.0 mg of intermediate 1 is added to every 100 mL of anhydrous N,N-dimethylformamide;

[0027] Preferably, 5.0 mmol to 10.0 mmol of N-hydroxysuccinimide is added to every 100 mL of anhydrous N,N-dimethylformamide;

[0028] Preferably, 8.0 mmol-10.0 mmol of triethylamine is added to every 100 mL of anhydrous N,N-dimethylformamide;

[0029] Preferably, 6.0 mmol to 8.0 mmol of carbodiimide is added to every 100 mL of anhydrous N,N-dimethylformamide.

[0030] Preferably, the amino crown ether solution is prepared by dissolving 4'-aminobenzo-18-crown ether-6 in anhydrous N,N-dimethylformamide;

[0031] Preferably, 5.0 mmol to 10.0 mmol of 4'-aminobenzo-18-crown ether-6 is added to every 20 mL of anhydrous N,N-dimethylformamide;

[0032] Preferably, the dropping rate of the aminocrown ether solution is 1 mL / min to 3 mL / min;

[0033] Preferably, in step S2, the solvent is diethyl ether at 0°C;

[0034] Preferably, in step S2, the solid-liquid separation, washing of the solid, and drying are performed as follows: centrifugation at 4000 rpm for 10 min, dialyzing the obtained precipitate with 100 mL of pure water, MWCO 1 kDa, for 2 days, and finally, vacuum drying at 30 ℃-35 ℃ for 48 h.

[0035] Thirdly, this invention provides the application of the above-mentioned demulsifier or the demulsifier prepared by the above method in crude oil demulsification. The specific application method is as follows: the demulsifier, quaternary ammonium cationic surfactant, and white oil are mixed at a mass ratio of (15-20):(10-15):(75-80), and stirred at a speed of 1500 rpm-2000 rpm for at least 30 minutes to ensure uniform mixing, thus preparing a demulsifier stock solution. The stock solution is added to the crude oil emulsion to be treated at a dosage of 30 ppm-60 ppm (relative to the total mass of the crude oil emulsion) for demulsification and dehydration.

[0036] The application method of this invention combines the synthesized demulsifier with quaternary ammonium salt cations and white oil, achieving a synergistic demulsification effect. The lipophilic crown ether group of the demulsifier chelates metal cations, disrupting the charge shielding effect of the oil-water interface film. The hydrophilic polymer chains not only have a flocculation effect but also provide steric hindrance, achieving a synergistic demulsification effect of "charge neutralization and interface film penetration." The quaternary ammonium salt cations further neutralize the charge at the oil-water interface, and the white oil, as a carrier, helps the demulsifier disperse and migrate to the interface, thereby greatly improving the demulsification efficiency and speed. This method is suitable for various types of crude oil emulsions.

[0037] Preferably, the quaternary ammonium salt cation includes, but is not limited to, any one of: hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, or dodecyldimethylammonium chloride. Attached Figure Description

[0038] Figure 1 This is a reaction mechanism diagram for the preparation of the demulsifier of the present invention;

[0039] Figure 2 The infrared spectrum of crown ether-P(AM), the demulsifier prepared in Example 1 of this invention;

[0040] Figure 3 The Zeta potential diagrams are for the demulsifier of Example 1, the demulsifier of Comparative Example 1, and the blank emulsion. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0042] The reaction mechanism for the preparation of the demulsifier of this invention is as follows: Figure 1 .

[0043] Example 1

[0044] Phase 1: Synthesis of Intermediate 1

[0045] In a beaker, dissolve 0.04 g (0.10 mmol) of the chain transfer agent polyethylene glycol (PEG, Mn≈400) in 60 mL of pure water to prepare a PEG solution. In another beaker, dissolve 0.014 g (0.20 mmol) of acrylamide (AM) in 40 mL of pure water to prepare an AM solution.

[0046] Under N2 protection and with stirring at 300 rpm, AM solution and PEG solution were added to a 250 mL three-necked flask and reacted for 30 min to remove dissolved oxygen. Then, 4,4'-azobis(4-cyanopentanoic acid) solution (0.01 g of 4,4'-azobis(4-cyanopentanoic acid) dissolved in 5 mL of pure water) was added. The mixture was heated to 60 °C and maintained at this temperature for 6 h. After cooling to room temperature, the resulting reaction solution was poured into cold acetone (V). 冷丙酮 V 反应液 In a mixture of 5:1, a white flocculent precipitate was formed. The precipitate was collected by filtration and washed three times with fresh, cold acetone. The precipitate was then transferred to a vacuum drying oven and dried under vacuum at 40°C for 24 hours to obtain a white solid powder, i.e., intermediate 1.

[0047] Phase Two: Synthesis of the Target Product

[0048] Intermediate 1 was dried under vacuum at 40 °C for 6 h; amino crown ether: 4'-aminobenzo-18-crown ether-6 was dried under vacuum at 40 °C for 2 h.

[0049] Under N2 protection, at room temperature (25 °C) and with stirring at 300 rpm, 0.5 g of intermediate 1 and 100 mL of anhydrous N,N-dimethylformamide (DMF) were added to a 250 mL three-necked flask and stirred until completely dissolved (the concentration of intermediate 1 solution was 5.0 mg / mL). Then, 0.58 g of 5.0 mmol of N-hydroxysuccinimide (NHS) and 1.1 mL of 8 mmol of triethylamine (TEA) were added. After reacting for 10 min, 1.15 g of 6.0 mmol of carbodiimide (EDC) was rapidly added, and the reaction was activated for 30 min (slight turbidity in the flask is normal) to obtain the activated solution. An amino crown ether solution (1.78 g of 5.0 mmol of 4'-aminobenzo-18-crown ether-6 dissolved in 20 mL of anhydrous DMF) was added dropwise to the activated solution at a rate of 1 mL / min until the addition was complete. The reaction was allowed to proceed for 24 h, and 0.2 mL of the solution was then collected. TLC was performed (CH₂Cl₂ / MeOH = 9:1, product Rf ≈ 0.25; if free amine spots still appeared, 0.1 mol EDC / NHS was added and the reaction continued for 6 h until the free amine spots disappeared, indicating that the reaction was complete). After the reaction was completed, the resulting target solution was added to 250 mL of 0 °C diethyl ether to obtain a white precipitate. The precipitate was then centrifuged at 4000 rpm for 10 min for solid-liquid separation. The precipitate was washed with 100 mL of pure water (MWCO 1 kDa, 2 d) to remove impurities. Finally, it was dried under vacuum at 30 °C for 48 h to obtain 1.22 g of white, fluffy solid, which was the target product, crown ether-P(AM). The target product n=200 was determined.

[0050] The infrared spectrum of this emulsifier is as follows: Figure 2 As shown, the infrared spectrum analysis is as follows: 3320cm -1 ν(N–H) amide; 3070cm -1 ν(=C–H) aromatic ring; 2930cm -1 , 2850cm -1 ν(CH2); 1650cm -1 ν(C=O); 1545cm -1 , (δN–H + νC–N); 1460cm -1 δ(CH2); 1350cm -1 , ω(CH2); 1250cm -1 Characteristic of ν(Ar–O–C)benzo-18-crown ether; 1120 cm -1 ν(C–O–C) crown ether; 650cm -1 γ(Ar–H) confirmed the formation of the target structure.

[0051] Example 2

[0052] Phase 1: Synthesis of Intermediate 1

[0053] In a beaker, dissolve 0.40 g of 1.0 mmol of the chain transfer agent polyethylene glycol (PEG, Mn≈400) in 60 mL of pure water to prepare a PEG solution. In another beaker, dissolve 1.8 g of 2.5 mmol of acrylamide (AM) in 20 mL of pure water to prepare an AM solution.

[0054] Under N2 protection and with stirring at 300 rpm, AM solution and PEG solution were added to a 250 mL three-necked flask and reacted for 30 min to remove dissolved oxygen. Then, 4,4'-azobis(4-cyanopentanoic acid) solution (0.042 g, 0.15 mmol of 4,4'-azobis(4-cyanopentanoic acid) dissolved in 5 mL of pure water) was added, and the mixture was heated to 68 °C and maintained at this temperature for 7 h. After cooling to room temperature, the resulting reaction solution was poured into cold acetone (V... 冷丙酮 V 反应液 In a mixture of 8:1, a white flocculent precipitate was formed. The precipitate was collected by filtration and washed three times with fresh, cold acetone. The precipitate was then transferred to a vacuum drying oven and dried under vacuum at 40°C for 24 hours to obtain 1.32 g of white solid powder, namely intermediate 1, with the structural formula summarized as: COOH-PAM.

[0055] Phase Two: Synthesis of the Target Product

[0056] Intermediate 1 was dried under vacuum at 40 °C for 6 h; amino crown ether: 4'-aminobenzo-18-crown ether-6 was dried under vacuum at 40 °C for 2 h.

[0057] Under N2 protection, at room temperature (25 °C) and with stirring at 300 rpm, 1.0 g of intermediate 1 and 100 mL of anhydrous DMF were added to a 250 mL three-necked flask and stirred until completely dissolved (the concentration of intermediate 1 solution was 10.0 mg / mL). Then, 0.92 g of 8.0 mmol of N-hydroxysuccinimide (NHS) and 1.3 mL of 9.0 mmol of triethylamine (TEA) were added. After reacting for 10 min, 1.34 g of 7.0 mmol of carbodiimide (EDC) was rapidly added, and the reaction was activated for 30 min (slight turbidity in the flask is normal) to obtain the activated solution. The amino crown ether solution (2.49 g of 8.0 mmol of 4'-aminobenzo-18-crown ether-6 dissolved in 20 mL of anhydrous DMF) was added dropwise to the activated solution at a rate of 2 mL / min until the addition was complete. The reaction was allowed to proceed for 24 h, and 0.2 mL of the solution was then collected. TLC was performed (CH2Cl2 / MeOH = 9:1, product Rf ≈ 0.25; if free amine spots still appear, 0.1 mol EDC / NHS was added and the reaction continued for 6 h until the free amine spots disappeared, indicating that the reaction was complete). After the reaction was completed, the obtained target solution was added to 250 mL of 0 °C diethyl ether to obtain a white precipitate. The precipitate was then centrifuged at 4000 rpm for 10 min to separate the solid and liquid. The precipitate was washed by dialyzing with 100 mL of pure water (MWCO 1 kDa, 2 d) to remove impurities. Finally, it was dried under vacuum at 30 °C for 48 h to obtain 1.32 g of white fluffy solid, which is the target product, namely crown ether-P(AM). The n of the target product was determined to be 300.

[0058] Example 3

[0059] Phase 1: Synthesis of Intermediate 1

[0060] In a beaker, dissolve 0.04 g (0.10 mmol) of the chain transfer agent polyethylene glycol (PEG, Mn≈400) in 60 mL of pure water to prepare a PEG solution. In another beaker, dissolve 0.021 g (0.30 mmol) of acrylamide (AM) in 40 mL of pure water to prepare an AM solution.

[0061] Under N2 protection and with stirring at 300 rpm, AM solution and PEG solution were added to a 250 mL three-necked flask and reacted for 30 min to remove dissolved oxygen. Then, 4,4'-azobis(4-cyanopentanoic acid) solution (0.015 g of 4,4'-azobis(4-cyanopentanoic acid) dissolved in 5.0 mL of pure water) was added, the temperature was raised to 70 °C, and the reaction was maintained at this temperature for 8 h. After cooling to room temperature, the resulting reaction solution was poured into cold acetone (V... 冷丙酮 V 反应液 In a mixture of 10:1, a white flocculent precipitate was formed. The precipitate was collected by filtration and washed three times with fresh, cold acetone. The precipitate was then transferred to a vacuum drying oven and dried under vacuum at 40°C for 24 hours to obtain a white solid powder, i.e., intermediate 1.

[0062] Phase Two: Synthesis of the Target Product

[0063] Intermediate 1 was dried under vacuum at 40 °C for 6 h; amino crown ether: 4'-aminobenzo-18-crown ether-6 was dried under vacuum at 40 °C for 2 h.

[0064] Under N2 protection, at room temperature (25 °C) and with stirring at 300 rpm, 1 g of intermediate 1 and 100 mL of anhydrous DMF were added to a 250 mL three-necked flask and stirred until completely dissolved (the concentration of intermediate 1 solution was 10.0 mg / mL). Then, 1.15 g of 10.0 mmol N-hydroxysuccinimide (NHS) and 1.4 mL of 10.0 mmol triethylamine (TEA) were added. After reacting for 10 min, 1.53 g of 8.0 mmol carbodiimide (EDC) was rapidly added, and the reaction was activated for 30 min (slight turbidity in the flask is normal) to obtain the activated solution. The amino crown ether solution (3.11 g of 10.0 mmol of 4'-aminobenzo-18-crown ether-6 dissolved in 20 mL of anhydrous DMF) was added dropwise to the activated solution at a rate of 3 mL / min until the addition was complete. The reaction was allowed to proceed for 24 h, and 0.2 mL of the solution was then collected. TLC was performed (CH2Cl2 / MeOH = 9:1, product Rf ≈ 0.25; if free amine spots still appeared, 0.1 mol EDC / NHS was added and the reaction continued for 6 h until the free amine spots disappeared, indicating that the reaction was complete). After the reaction was completed, the target solution was added to 250 mL of 0 °C diethyl ether to obtain a white precipitate. The precipitate was then centrifuged at 4000 rpm for 10 min to separate the solid and liquid. The precipitate was washed by dialyzing with 100 mL of pure water (MWCO 1 kDa, 2 d). Finally, it was dried under vacuum at 30 °C for 48 h to obtain 1.4 g of white fluffy solid, which was the target product, crown ether-P(AM), with n determined to be 400.

[0065] Comparative Example 1

[0066] Commercially available polyether-based demulsifier (model: SP169) was used.

[0067] Application examples

[0068] Preparation of demulsifier stock solution: Take the demulsifiers prepared in Examples 1-3 and the demulsifiers in Comparative Example 1, respectively, and mix them with quaternary ammonium salt and white oil in the following mass ratio: demulsifier: cetyltrimethylammonium chloride: white oil = 18:12:70. Stir at 1800 rpm for 40 min to form uniform stock solutions A, B, C and D.

[0069] Verification Example

[0070] Crude oil emulsion preparation: Two types of oil samples from the oil field were selected and mixed to form a crude oil emulsion with a water content of 50%.

[0071] Crude oil emulsion 1 is a common W / O type emulsion: it is prepared from purified oil from an oilfield and wastewater without crude oil demulsifier. During preparation, firstly, 500g of the purified oil is weighed into the cup of an automatic mixer using a platform scale; separately, 500g of the wastewater is weighed into a beaker; then, both cups are placed in a constant temperature water bath (55℃) at a temperature 5-10℃ lower than the dehydration temperature for preheating; then, the automatic mixer is started, and the wastewater from the beaker is slowly and evenly added to the cup of the automatic mixer, and thoroughly stirred to obtain crude oil emulsion 1.

[0072] Crude oil emulsion 2 is a relatively stable O / W (reverse phase) emulsion prepared by mixing purified oil from an oilfield with high-mineralization (NaCl concentration 50000 mg / L) wastewater. During preparation, firstly, 500g of the purified oil was weighed into the cup of an automatic mixer using a platform scale; separately, 500g of the high-mineralization (NaCl concentration 50000 mg / L) wastewater was weighed into a beaker; then, both cups were placed in a constant-temperature water bath (55℃) at a temperature 5-10℃ lower than the dehydration temperature for preheating; then, the automatic mixer was started, and the wastewater from the beaker was slowly and evenly added to the cup of the automatic mixer, and thoroughly stirred to obtain crude oil emulsion 2.

[0073] The shelf life of crude oil emulsion samples should not exceed 3 days.

[0074] The separated oily wastewater should be sampled directly from the dehydration bottle using a syringe. During sampling, first draw a small amount of air into the syringe fitted with a rigid plastic pipette approximately 300mm long, insert it into the oily wastewater phase of the dehydration bottle (the pipette tip approximately 10mm from the bottom of the bottle), and slowly expel the air. After the liquid in the bottle stabilizes, slowly aspirate a certain amount of the separated oily wastewater (avoiding the intake of crude oil). Then remove the syringe, disconnect the plastic pipette, and inject the water sample into a graduated cylinder. Once the syringe has cooled to room temperature, draw in a small amount of unleaded gasoline or petroleum ether to rinse the sample, and add the rinsing solution to the graduated cylinder.

[0075] 1. Demulsification performance test: According to SY / T 5281-91 Crude oil demulsifier performance test method (bottle test method)

[0076] Static bottle demulsification experiment: 100 g of the above crude oil emulsion 1 and crude oil emulsion 2 were placed in stoppered graduated cylinders and preheated in a 55℃ constant temperature water bath for 10 min. Using a microsyringe, the mother solutions A, B, C, and D prepared in the verification example were added to each graduated cylinder, respectively, so that the concentration of the emulsion in the mother solution was 50 ppm. The cylinders were vigorously shaken 100 times to mix thoroughly, and then returned to the 55℃ water bath to settle. The amount of water removed at different times (30 min, 60 min, 120 min, 180 min) was recorded, and the dehydration rate (volume of removed water / total water volume in the emulsion × 100%) was calculated. The experimental results are shown in Table 1.

[0077] Table 1. Dehydration rate (%) 180 min after demulsification

[0078]

[0079] As can be seen from Table 1, for conventional W / O type emulsions (crude oil emulsion 1), the demulsifier of the present invention (Examples 1-3) and the commercially available conventional demulsifier (Comparative Example 1) both showed good demulsification effects, and the final dehydration rate was over 90%, with comparable performance.

[0080] However, for more stable O / W reverse emulsions formed by high-salinity water (crude oil emulsion 2), the mother liquor prepared with the demulsifier of this invention shows significant advantages. The final dehydration rate of the mother liquor prepared with the demulsifiers of Examples 1-3 all reached over 93%, significantly higher than the 71.5% of Comparative Example 1. This indicates that the crown ether group introduced in the demulsifier of this invention can effectively complex Na in high-salinity water. + Ions disrupt the interfacial film structure of O / W emulsions, thereby achieving efficient reverse demulsification and solving the technical problem of poor performance of traditional demulsifiers in such emulsions.

[0081] 2. Compatibility test

[0082] The demulsifier prepared in Example 1 was compounded with the in-situ corrosion inhibitor (IM-AC) and scale inhibitor (PPCA). According to the performance testing method for crude oil demulsifiers in SY / T5281-91, the original demulsification experiment was carried out. The oil-water samples after demulsification were observed and found that there was no secondary emulsification and the foam height was < 2 cm. The pH of the aqueous phase after demulsification was 6.8. After keeping it at 55 ℃ for 24 h, the amide bond hydrolysis rate was 75% and the COD contribution was reduced by 63%, which met the green emission requirements.

[0083] 3. Zeta potential

[0084] The demulsifiers of Example 1 and Comparative Example 1 were added to crude oil emulsion 2, while a blank control (crude oil emulsion 2 without any demulsifier was used as a blank emulsion) was performed. The Zeta potentials at different demulsifier concentrations were measured, and the results are shown in [Figure 1]. Figure 3 .

[0085] As shown in Figure 3, with the increase of the demulsifier concentration in Example 1, the absolute value of the Zeta potential of the emulsion decreased from 42 mV to 5 mV, and entered the -5 to +5 mV plateau region at 80–120 mg / L, indicating that the charge in the interfacial film was sufficiently neutralized. In contrast, the absolute values ​​of the Zeta potential of Comparative Example 1 and the blank emulsion were below 20 mV. This indicates that the demulsifier of the present invention has a good charge neutralization effect, and the crown ether group can more specifically complex the metal cations (Na+) at the oil-in-water emulsion interface. + Mg + Ca + K + (etc.), quickly neutralize the charge at the oil-water interface, weaken the repulsive force between droplets, thereby promoting droplet coalescence, effectively disrupting the stability of the water-in-oil emulsion interface film, and achieving reverse demulsification.

[0086] 4. Industrial scale-up of demulsifier in 5000 L volume

[0087] Following the formulation ratio of Example 1, S1 was completed in a 6500 L glass-lined reactor; the S2 coupling step was switched to a 5000 L stainless steel reactor. DMF was recovered via a triple-effect evaporator, and 4.5 t of demulsifier was produced in batches. The quality indicators were consistent with the laboratory samples (IR, dehydration rate). The mother liquor was injected into the platform wellhead pipeline via a 2-inch plunger pump (injection concentration 50 ppm). After 30 days of continuous operation, the average dehydration rate was 96%, the interface was clear, and there was no sediment, completely replacing the original reagent SP169.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A demulsifier with reverse demulsification function, characterized in that, include: The structure of the demulsifier is shown in formula (I): Equation (I), In equation (I), n = 200 - 400.

2. The method for preparing the demulsifier as described in claim 1, characterized in that, Includes the following steps: S1. Under N2 protection and stirring, acrylamide solution and chain transfer agent polyethylene glycol solution are mixed evenly, and then initiator solution is added dropwise and mixed evenly. The temperature is raised to 60℃-70℃ and the reaction is maintained for 6h-8h. After cooling to room temperature, a reaction solution is obtained. The reaction solution is poured into cold acetone to precipitate. After filtration, the solid is washed and dried to obtain intermediate 1. S2. Under N2 protection, with stirring, at room temperature, add N-hydroxysuccinimide and triethylamine to the intermediate 1 solution, react for at least 10 min, then add carbodiimide, react for at least 30 min, to obtain the activated solution; Then, an amino crown ether solution was added dropwise to the activation solution. After reacting for 24-48 hours, the target solution was obtained. The target solution was poured into a solvent to precipitate. After solid-liquid separation, the solid was washed and dried to obtain crown ether-P(AM). The structural formula of intermediate 1 is shown in formula (II): Equation (II).

3. The method for preparing the demulsifier according to claim 2, characterized in that, In step S1, the molar ratio of polyethylene glycol to acrylamide is 1:(2-3). The acrylamide solution was prepared by dissolving acrylamide in pure water, with 0.20 mmol-0.30 mmol of acrylamide added to every 40 mL of pure water; The polyethylene glycol solution is prepared by dissolving polyethylene glycol in pure water, with 0.10 mmol-0.20 mmol of polyethylene glycol added to every 60 mL of pure water; The initiator solution is prepared by dissolving the initiator in pure water, with 0.010 g to 0.015 g of initiator added to every 5 mL of pure water.

4. The method for preparing the demulsifier according to claim 3, characterized in that, The initiator is 4,4'-azobis(4-cyanopentaic acid). In step S1, the volume ratio of the reaction solution to cold acetone is 1:(5-10). In steps S1 and S2, the stirring rate during the stirring state is 300 rpm-500 rpm; Step S1, the drying is vacuum drying at 40℃-45℃ for 24 h-48 h.

5. The method for preparing the demulsifier according to claim 2, characterized in that, In step S2, the intermediate 1 solution is prepared by dissolving intermediate 1 in anhydrous N,N-dimethylformamide; Add 5.0 mg to 10.0 mg of intermediate 1 to every 100 mL of anhydrous N,N-dimethylformamide; Add 5.0 mmol-10.0 mmol of N-hydroxysuccinimide to every 100 mL of anhydrous N,N-dimethylformamide; Add 8.0 mmol-10.0 mmol of triethylamine to every 100 mL of anhydrous N,N-dimethylformamide; Add 6.0 mmol-8.0 mmol of carbodiimide to every 100 mL of anhydrous N,N-dimethylformamide.

6. The method for preparing the demulsifier according to claim 5, characterized in that, The amino crown ether solution was prepared by dissolving 4'-aminobenzo-18-crown ether-6 in anhydrous N,N-dimethylformamide; Add 5.0 mmol to 10.0 mmol of 4'-aminobenzo-18-crown ether-6 to every 20 mL of anhydrous N,N-dimethylformamide; The dropping rate of the amino crown ether solution is 1 mL / min-3 mL / min; In step S2, the solvent is diethyl ether at 0°C; In step S2, the solid-liquid separation, washing of the solid, and drying are as follows: centrifugation at 4000 rpm for 10 min, dialyzing the obtained precipitate with 100 mL of pure water, MWCO 1 kDa, for 2 days, and finally, vacuum drying at 30 ℃-35 ℃ for 48 h.

7. The application of the demulsifier according to claim 1 or the demulsifier prepared by any one of claims 1-6 in crude oil demulsification, characterized in that, The demulsifier, quaternary ammonium cation, and white oil are mixed and stirred evenly to obtain a mother liquor; then the mother liquor is added to the crude oil emulsion at 30 ppm-60 ppm to demulsify the crude oil.

8. The application according to claim 7, characterized in that, The mass ratio of the demulsifier, quaternary ammonium cation, and white oil is (15-20):(10-15):(75-80).

9. The application according to claim 8, characterized in that, The quaternary ammonium salt cation includes any one of hexadecyltrimethylammonium, octadecyltrimethylammonium, or dodecyldimethylammonium.

10. The application according to claim 7, characterized in that, The stirring speed is 1500 rpm-2000 rpm, and the stirring time is at least 30 minutes.

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