A demulsifier for oilfield wastewater treatment

Abstract

The invention discloses a demulsifier for oilfield sewage treatment, and relates to the technical field of sewage treatment. The preparation method of the demulsifier comprises the following steps: S1: after monomer A, monomer B and a catalyst are mixed evenly, propylene oxide is added and mixed evenly, and the mixture is reacted for 2-3 hours at 120-130°C, and then aged for 0.5-1.5 hours to obtain a low molecular weight polyether; S2: ethylene oxide is added to the low molecular weight polyether of step S1, mixed evenly, heated to 130-140°C, reacted for 2-3 hours, aged for 1-2 hours, cooled, washed, and obtained a high molecular weight polyether; S3: the high molecular weight polyether, monomer C, initiator and solvent in S2 are mixed evenly, the temperature is increased to 55-80°C, the mixture is reacted for 2-4 hours, cooled, and obtained a demulsifier. The demulsifier prepared by the invention not only has a good demulsification effect, but also has high stability and durability.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, in particular to a demulsifier for oilfield sewage treatment. Background Art

[0002] Oilfield sewage, also known as oilfield wastewater, mainly includes oil production wastewater, drilling wastewater and refinery wastewater. In many cases, it specifically refers to oil production wastewater. With the increase of oilfield exploitation years, the water content of the water production fluid continues to rise, and in some blocks it has reached more than 90%. These oily sewage has become the main water injection source for oilfields.

[0003] The main characteristics of oilfield wastewater are: first, the crude oil content is high, up to 1000~2000mg / L, mainly in the form of suspended oil, emulsified oil and dispersed oil. The oil content in the wastewater is mainly suspended oil and dispersed oil, accounting for about 90% of the oil content; second, the suspended matter content is high, and the oilfield wastewater contains a variety of solid particles, such as clay, paraffin, various bacteria, silt, insoluble organic matter, etc. If oilfield wastewater is not properly treated, it will not only easily cause scaling and corrosion of the gathering and transportation pipelines and water injection systems, but also cause great damage to the pores of the formation, and cause serious pollution to the soil and water bodies, endangering the health of the ecosystem and human life.

[0004] In addition, due to the presence of crude oil and suspended solids in oil production wastewater, the wastewater has high viscosity and viscosity, making it difficult to separate and treat. In order to make oilfield wastewater meet the standards for reinjection into the oil layer, these two pollutants need to be effectively treated. Oilfield wastewater demulsifier is a chemical substance that can demulsify the oil-water dispersion system. It can change the surface properties of the oil-water dispersion system and make it stable, thereby making it easier to separate oil and water.

[0005] The patent application document with publication number CN106335968A discloses a demulsifier for high-polymer thick oil content wastewater, which is prepared by polymerization reaction of 60-80 parts of polyether amine, 16-20 parts of high carbon alcohol, 15-20 parts of epoxy compound and 100-200 parts of organic solvent, 0.1-0.5 parts of metallocene catalyst, and then sulfonation reaction of 10-15 parts of sulfonating agent.

[0006] The demulsifier molecular chain in the application document presents a long chain structure, which may result in insufficient interaction between it and the emulsifier on the surface of the oil droplets during the demulsification process, thereby affecting the demulsification effect. Summary of the invention

[0007] In order to increase the interaction between the demulsifier and the emulsifier on the surface of the oil droplets, and thus enhance the demulsification effect, the present invention provides a demulsifier for oilfield wastewater treatment.

[0008] The demulsifier for oilfield wastewater treatment provided by the present invention adopts the following technical scheme:

[0009] A demulsifier for oilfield wastewater treatment, the preparation method of the demulsifier comprising the following steps:

[0010] S1: After monomer A, monomer B and catalyst are uniformly mixed, propylene oxide is added and mixed uniformly, reacted at 120-130°C for 2-3h, and aged for 0.5-1.5h to obtain a low molecular weight polyether;

[0011] S2: adding ethylene oxide to the low molecular weight polyether of step S1, mixing evenly, heating to 130-140° C., reacting for 2-3 hours, aging for 1-2 hours, cooling, adding hydrogen peroxide, continuously blowing nitrogen and evacuating, and washing to obtain a high molecular weight polyether;

[0012] S3: Evenly mix the high molecular weight polyether, monomer C, initiator and solvent in S2, raise the temperature to 55-80°C, react for 2-4 hours, and cool down to obtain a demulsifier;

[0013] The monomer A and the monomer B are both alcohols containing carbon-carbon double bonds; the monomer C is indole-3-acrylic acid;

[0014] The amount of hydrogen peroxide used accounts for 2% of the total mass of ethylene oxide and propylene oxide.

[0015] Preferably, the catalyst is potassium hydroxide, and the amount of potassium hydroxide used accounts for 2% of the total mass of monomer A and monomer B.

[0016] Preferably, the initiator is azobisisobutyronitrile, and the amount of the initiator used accounts for 0.3% of the total mass of the reactants.

[0017] Preferably, the solvent is xylene.

[0018] By adopting the above technical scheme, under the action of potassium hydroxide catalyst, alcohol containing carbon-carbon double bonds is used as an initiator, and ring-opening polymerization is carried out with propylene oxide and ethylene oxide monomers in sequence to obtain a high molecular weight polyether containing more carbon-carbon double bonds; the high molecular weight polyether has a long chain structure, and after further mixing with indole-3-acrylic acid, under the action of an initiator, a cross-linking reaction will occur between the high molecular weight polyether itself and indole-3-acrylic acid. At the same time, the carboxyl group of indole-3-acrylic acid and the hydroxyl group on the high molecular weight polyether will also react to obtain a demulsifier in a network with more branches, and the relative molecular weight of the demulsifier is greatly increased, and a three-dimensional network structure can be formed in oilfield wastewater, thereby more effectively capturing and fixing oil droplets, thereby maintaining a stable demulsification effect. While participating in the reaction, indole-3-acrylic acid introduces the indole group into the polymer structure of the demulsifier, which can improve the interfacial activity of the polyether and enhance its adsorption capacity on the oil-water interface, thereby enhancing the demulsification effect. In addition, the indole ring can also affect the intermolecular interactions of the polyethers, helping to form more stable aggregates that can more effectively separate the oil-water mixture during the demulsification process.

[0019] In the late stage of the synthesis of high molecular weight polyether, a small amount of hydrogen peroxide is added. On the one hand, it can react with impurities and by-products in the reaction system to oxidize them and convert them into substances that are easier to remove, thereby improving the purity of the high molecular weight polyether. On the other hand, hydrogen peroxide can also consume unreacted ethylene oxide and other active substances, reduce the occurrence of side reactions, and thus stabilize the structure and performance of the high molecular weight polyether.

[0020] Since the obtained polymer polyether has relatively high purity and relatively stable structure, the polyether molecules in the subsequently prepared demulsifier can be arranged more stably and orderly on the oil-water interface, giving full play to its role in reducing interfacial tension, greatly improving the demulsification effect and enhancing the thoroughness of demulsification.

[0021] Preferably, in step S1, after the monomer A and the catalyst are uniformly mixed, propylene oxide is added and mixed uniformly, and the mixture is reacted at 120-130° C. for 2-3 hours and aged for 0.5-1.5 hours to obtain a low molecular weight polyether A;

[0022] After the monomer B and the catalyst are mixed evenly, propylene oxide is added and mixed evenly, and the mixture is reacted at 120-130°C for 2-3 hours, and then aged for 0.5-1.5 hours to obtain a low molecular weight polyether B;

[0023] In the step S2, ethylene oxide is added to the low molecular weight polyether A of step S1, mixed evenly, heated to 130-140° C., reacted for 2-3 hours, aged for 1-2 hours, cooled, hydrogen peroxide is added, nitrogen is continuously blown and vacuumed, and then washed to obtain a high molecular weight polyether A;

[0024] Add ethylene oxide to the low molecular weight polyether B in step S1, mix evenly, heat to 130-140° C., react for 2-3 hours, age for 1-2 hours, cool, add hydrogen peroxide, continue nitrogen blowing and vacuum for 30 minutes, wash, and obtain high molecular weight polyether B;

[0025] In the step S3, the high molecular weight polyether A, high molecular weight polyether B, monomer C, initiator and solvent in S2 are uniformly mixed, the temperature is increased to 60-80° C., reacted for 2-4 hours, and cooled to obtain a demulsifier;

[0026] The amount of hydrogen peroxide used twice is the same, and the total amount of hydrogen peroxide used accounts for 2% of the total mass of ethylene oxide and propylene oxide.

[0027] Preferably, the catalyst is potassium hydroxide, and the amount of the catalyst used accounts for 2% of the weight of the monomer.

[0028] Preferably, the monomer is monomer A or monomer B.

[0029] By adopting the above technical solution, two high molecular weight polyethers with different structures are cross-linked with each other, and the demulsifier formed by the two polyethers can form a stronger binding force at the oil-water interface, thereby more effectively reducing the oil-water interfacial tension and improving the demulsification effect. This is mainly because after the two polyethers are cross-linked with each other, due to the introduction of different polyether molecules, a larger and more complex network structure is formed. This network structure not only increases the molecular weight of the polyether, but also may introduce more branched structures, thereby enhancing the demulsification effect of the demulsifier.

[0030] Preferably, the ratio of the total moles of monomer A and monomer B, the moles of propylene oxide, the moles of ethylene oxide, and the moles of monomer C is 3-4:0.5-1:1.5-4:1-3, and the molar ratio of monomer A to monomer B is 1-2:1-2.

[0031] Preferably, the carbon number of the alkyl group of the monomer A is 4-7; and the carbon number of the alkyl group of the monomer B is 12-16.

[0032] Preferably, the monomer A is any one of 2,3-dihydroxy-1-butene and trimethylbutenediol.

[0033] Preferably, the monomer B is any one of cis-11-hexadecene-1-ol and (Z)-dodec-9-ene-1-ol;

[0034] By adopting the above technical solution, different polyethers are synthesized by using long and short alkyl chain alcohols, and then further cross-linked, the demulsification effect can be further enhanced. This is because the demulsifier formed contains alkyl side chains of different lengths. The shorter side chains have better penetration properties and can better penetrate into small gaps to achieve better demulsification effects; while the longer alkyl side chains can further reduce the surface tension of water, help oil-water separation, enhance the adsorption and aggregation of oil droplets, and thus accelerate the oil-water separation process.

[0035] Preferably, in step S3, after monomer C is added, monomer D is also added, wherein monomer D is dimethylvinylsilanol, and the molar ratio of monomer C to monomer D is 3:1-2.

[0036] By adopting the above technical solution, the cross-linking of the polyether polymer and the monomer D can, on the one hand, form compounds with stronger surface activity. These compounds can more effectively destroy the stability of the emulsion and accelerate the oil-water separation process, thereby improving the demulsification efficiency. On the other hand, this reaction also increases the number of side chains of the demulsifier and enhances the adsorption capacity of the demulsifier at the oil-water interface, thereby more effectively destroying the stability of the emulsion and promoting oil-water separation. In addition, the increase in the number of side chains can also improve the dispersibility of the demulsifier in the oil phase, allowing it to exert a stronger force on the oil droplets, further accelerating the thoroughness of demulsification.

[0037] Preferably, in step S3, a portion of the high molecular weight polyether A, a portion of the high molecular weight polyether B, the monomer C, the initiator and the solvent in S2 are uniformly mixed to obtain a mixed solution A;

[0038] The other part of the high molecular weight polyether A in S2, the other part of the high molecular weight polyether B, the monomer D, the initiator and the solvent are uniformly mixed to obtain a mixed solution B;

[0039] After the mixed solution A and the mixed solution B are evenly mixed, the temperature is raised to 60-80°C, reacted for 2-4 hours, and then cooled to room temperature to obtain a demulsifier.

[0040] Preferably, in step S3, a portion of the high molecular weight polyether A in S2, a portion of the high molecular weight polyether B, the monomer C, the initiator and the solvent are uniformly mixed, the temperature is increased to 60-80° C., the reaction is carried out for 2-4 hours, and the temperature is cooled to room temperature to obtain a demulsifier A;

[0041] The other part of the high molecular weight polyether A in S2, the other part of the high molecular weight polyether B, the monomer D, the initiator and the solvent are uniformly mixed, the temperature is increased to 60-80°C, the reaction is carried out for 2-4 hours, and the temperature is cooled to room temperature to obtain a demulsifier B;

[0042] The demulsifier A and the demulsifier B are mixed evenly to obtain a demulsifier.

[0043] By adopting the above technical scheme, the demulsifier A and demulsifier B are mixed, which can speed up the demulsification process and make the water and oil in the emulsion separate faster. This is mainly because after demulsifier A and demulsifier B are mixed, the two interact at the molecular level, such as hydrogen bonding, van der Waals force, etc., which helps to form a more stable composite structure and enhance the demulsification effect. In addition, demulsifier B usually has good solubility and stability due to the introduction of monomer D, making it easier to diffuse and adsorb on the interface, which can effectively reduce the tension of the oil-water interface and promote oil-water separation. Demulsifier A increases the hydrophilicity and lipophilicity of the demulsifier due to the introduction of monomer C, which helps to enhance the demulsification effect. These two types of demulsifiers can not only increase the demulsification speed through complementary effects, but also increase the dehydration rate and the clarity of the dewatered water, showing a synergistic effect, which can better adapt to different types of crude oil emulsions and improve the adaptability and efficiency of demulsifiers.

[0044] Preferably, the demulsifier can also be used in combination with polyacrylamide.

[0045] Preferably, steps S1 and S2 are performed under an inert atmosphere.

[0046] In summary, the present invention includes at least one of the following beneficial technical effects:

[0047] 1. The demulsifier of the present invention has a stronger network structure, which can better adapt to oilfield sewage containing more impurities and higher viscosity, can more effectively capture and fix oil droplets, and can maintain a stable demulsification effect even under higher temperature and pressure conditions. In addition, the demulsifier with a network structure also has a strong shear resistance, which can resist the action of external forces during the treatment process and maintain its demulsification effect.

[0048] 2. Due to the introduction of the indole ring, the demulsifier in the present invention can improve the interfacial activity of the polyether and enhance the adsorption capacity of the demulsifier on the oil-water interface, thereby enhancing the demulsification effect. In addition, the rigid aromatic structure of the indole ring makes the demulsifier molecular structure have a certain rigidity, which can more effectively destroy the stability of the emulsion, thereby achieving rapid demulsification.

[0049] 3. The demulsifier prepared in the present invention has a more stable composite structure, not only has a good demulsification effect, but also has high stability and durability. DETAILED DESCRIPTION

[0050] The present invention is further described in detail below with reference to the embodiments.

[0051] In the following embodiments:

[0052] The main pollutants of the oil production wastewater in Changqing Oilfield are crude oil and suspended matter. The crude oil content is as high as 1500 mg / L, and it exists in various forms such as suspended oil (diameter greater than 100μm), dispersed oil (diameter 10~100μm), emulsified oil (diameter 0.1~10μm) and dissolved oil (diameter less than 0.1μm). Among them, suspended oil accounts for about 68% of the total oil content in the oil production wastewater, dispersed oil accounts for about 20% of the total oil content in the oil production wastewater, emulsified oil accounts for about 11% of the total oil content in the oil production wastewater, and dissolved oil accounts for about 1% of the total oil content in the oil production wastewater.

[0053] Polyacrylamide was purchased from Henan Xintianda Environmental Protection Technology Co., Ltd.;

[0054] Indole-3-acrylic acid was purchased from Shanghai Darui Fine Chemicals;

[0055] 2,3-Dihydroxy-1-butene was purchased from Shanghai Kaiyin Chemical Co., Ltd.;

[0056] cis-11-hexadecene-1-ol was purchased from Wuhan Kamik Technology Co., Ltd.;

[0057] Trimethylbutenediol was purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.;

[0058] -Dodec-9-en-1-ol was purchased from Hubei Hongxin Ruiyu Fine Chemical Co., Ltd.; Vinyl dimethyl silanol was purchased from Hubei Xingyan New Materials Technology Co., Ltd.;

[0059] An embodiment of an oilfield wastewater treatment demulsifier of the present invention is as follows:

[0060] Example 1

[0061] This embodiment provides a demulsifier for oilfield wastewater treatment, and the preparation method of the demulsifier comprises the following steps:

[0062] S1: Add 1 mol of 2,3-dihydroxy-1-butene, 2 mol of cis-11-hexadecene-1-ol and potassium hydroxide to a reaction axe equipped with a stirrer and a thermometer, stir and mix evenly, evacuate and introduce nitrogen for 40 minutes, adjust the temperature to 120°C and the pressure to 0.3 MPa, introduce 0.5 mol of propylene oxide, stir and react at constant temperature and pressure for 3 hours, age for 1.5 hours, wait for the reaction pressure to drop to 0.12 MPa, evacuate and react for 30 minutes to obtain a low molecular weight polyether;

[0063] S2: Continue to adjust the temperature to 130°C and the pressure to 0.3MPa, introduce 1.5mol of ethylene oxide, stir and react for 3h, age for 2h, wait for the reaction pressure to drop to 0.12MPa, vacuum react for 30min, stop heating, cool the reaction product to room temperature, maintain stirring, add a small amount of hydrogen peroxide, continue to blow nitrogen and vacuum for 30min, take out the reaction product and place it in deionized water, stir and wash with water at 60r / min for 1h, stand still and separate, take the upper layer of liquid, distill at 100°C under reduced pressure (2kPa) for 20min to obtain a high molecular weight polyether;

[0064] S3: Evenly mix the above-mentioned high molecular weight polyether, 1 mol of indole-3-acrylic acid, 0.3% of azobisisobutyronitrile by weight of the total weight of the high molecular weight polyether and indole-3-acrylic acid, and 500 ml of xylene, raise the temperature to 55°C, react for 4 hours, and cool to room temperature to obtain a demulsifier.

[0065] The amount of potassium hydroxide used is 2% of the total mass of 2,3-dihydroxy-1-butene and cis-11-hexadecene-1-ol;

[0066] The amount of hydrogen peroxide used accounts for 2% of the total mass of ethylene oxide and propylene oxide.

[0067] Example 2

[0068] This embodiment provides a demulsifier for oilfield wastewater treatment, and the preparation method of the demulsifier comprises the following steps:

[0069] S1: Add 1 mol of 2,3-dihydroxy-1-butene and 2% of potassium hydroxide by mass of 2,3-dihydroxy-1-butene to a reaction axe A equipped with a stirrer and a thermometer, stir and mix evenly, evacuate and introduce nitrogen for 40 minutes, adjust the temperature to 120°C and the pressure to 0.3 MPa, introduce 0.25 mol of propylene oxide, stir and react at constant temperature and pressure for 3 hours, age for 1.5 hours, wait for the reaction pressure to drop to 0.12 MPa, evacuate and react for 30 minutes, and obtain a low molecular weight polyether A;

[0070] S2: Continue to adjust the temperature to 130°C and the pressure to 0.3MPa, introduce 0.75mol of ethylene oxide, stir and react for 3h, age for 2h, wait for the reaction pressure to drop to 0.12MPa, vacuum react for 30min, stop heating, cool the reaction product to room temperature, maintain stirring, add hydrogen peroxide, continue to blow nitrogen and vacuum for 30min, take out the reaction product and place it in deionized water, stir and wash with water at 60r / min for 1h, stand still and separate, take the upper layer of liquid, distill at 100°C under reduced pressure (2kPa) for 20min to obtain high molecular weight polyether A;

[0071] S3: Add 2 mol of cis-11-hexadecene-1-ol and potassium hydroxide accounting for 2% of the mass of cis-11-hexadecene-1-ol to a reaction axe B equipped with a stirrer and a thermometer, stir and mix evenly, evacuate and introduce nitrogen for 40 minutes, adjust the temperature to 120° C. and the pressure to 0.3 MPa, introduce 0.25 mol of propylene oxide, stir and react at constant temperature and pressure for 3 hours, age for 1 hour, wait for the reaction pressure to drop to 0.12 MPa, evacuate and react for 30 minutes, and obtain a low molecular weight polyether B;

[0072] S4: Continue to adjust the temperature to 130°C and the pressure to 0.3MPa, introduce 0.75mol of ethylene oxide, stir and react for 3h, age for 2h, wait for the reaction pressure to drop to 0.12MPa, vacuum react for 30min, stop heating, cool the reaction product to room temperature, maintain stirring, add hydrogen peroxide, continue to blow nitrogen and vacuum for 30min, take out the reaction product and place it in deionized water, stir and wash with water at 60r / min for 1h, stand still and separate, take the upper layer of liquid, distill at 100°C under reduced pressure (2kPa) for 20min to obtain high molecular weight polyether B;

[0073] S5: Evenly mix the above-mentioned high molecular weight polyether A, high molecular weight polyether B, 1 mol of indole-3-acrylic acid, 0.3% of azobisisobutyronitrile by weight of the total weight of high molecular weight polyether A, high molecular weight polyether B and acrylic acid, and 500 ml of xylene, raise the temperature to 60°C, react for 4 hours, and cool to room temperature to obtain a demulsifier.

[0074] In step S2 and step S4, the amount of hydrogen peroxide used twice is the same, and the total amount of hydrogen peroxide used accounts for 2% of the total mass of ethylene oxide and propylene oxide in the entire embodiment.

[0075] Example 3

[0076] This embodiment provides a demulsifier for oilfield wastewater treatment, and the preparation method of the demulsifier comprises the following steps:

[0077] S1: Add 2 mol of 2,3-dihydroxy-1-butene and 2% of potassium hydroxide by mass of 2,3-dihydroxy-1-butene to a reaction axe A equipped with a stirrer and a thermometer, stir and mix evenly, evacuate and introduce nitrogen for 40 minutes, adjust the temperature to 120°C and the pressure to 0.3 MPa, introduce 0.5 mol of propylene oxide, stir and react at constant temperature and pressure for 3 hours, age for 1.5 hours, wait for the reaction pressure to drop to 0.12 MPa, evacuate and react for 30 minutes to obtain a low molecular weight polyether A;

[0078] S2: Continue to adjust the temperature to 130°C and the pressure to 0.3MPa, introduce 2 mol of ethylene oxide, stir and react for 3 hours, age for 2 hours, wait for the reaction pressure to drop to 0.12MPa, vacuum react for 30 minutes, stop heating, cool the reaction product to room temperature, maintain stirring, add hydrogen peroxide, continue to blow nitrogen and vacuum for 30 minutes, take out the reaction product and place it in deionized water, stir and wash with water at 60r / min for 1 hour, stand still and separate, take the upper layer of liquid, distill at 100°C under reduced pressure (2kPa) for 20 minutes to obtain high molecular weight polyether A;

[0079] S3: Add 1 mol of cis-11-hexadecene-1-ol and 2% of potassium hydroxide by mass of cis-11-hexadecene-1-ol to a reaction vessel B equipped with a stirrer and a thermometer, stir and mix evenly, evacuate and introduce nitrogen for 40 min, adjust the temperature to 120° C. and the pressure to 0.3 MPa, introduce 0.5 mol of propylene oxide, stir and react at constant temperature and pressure for 3 h, age for 1.5 h, wait for the reaction pressure to drop to 0.12 MPa, evacuate and react for 30 min, and obtain a low molecular weight polyether B;

[0080] S4: Continue to adjust the temperature to 130°C and the pressure to 0.3MPa, introduce 2 mol of ethylene oxide, stir and react for 3h, age for 2h, wait for the reaction pressure to drop to 0.12MPa, vacuum react for 30min, stop heating, cool the reaction product to room temperature, maintain stirring, add hydrogen peroxide, continue to blow nitrogen and vacuum for 30min, take out the reaction product and place it in deionized water, stir and wash with water at 60r / min for 1h, stand still and separate, take the upper layer of liquid, distill at 100°C under reduced pressure (2kPa) for 20min to obtain high molecular weight polyether B;

[0081] S5: Evenly mix the above-mentioned high molecular weight polyether A, high molecular weight polyether B, 3 mol of indole-3-acrylic acid, 0.3% of azobisisobutyronitrile in the total mass of high molecular weight polyether A, high molecular weight polyether B and indole-3-acrylic acid, and 500 ml of xylene, increase the temperature to 60°C, react for 4 hours, and cool to room temperature to obtain a demulsifier.

[0082] In step S2 and step S4, the amount of hydrogen peroxide used twice is the same, and the total amount of hydrogen peroxide used accounts for 2% of the total mass of ethylene oxide and propylene oxide in the entire embodiment.

[0083] Example 4

[0084] This embodiment provides a demulsifier for oilfield wastewater treatment, and the preparation method of the demulsifier comprises the following steps:

[0085] S1: Add 1.5 mol of 2,3-dihydroxy-1-butene and 2% of potassium hydroxide by mass of 2,3-dihydroxy-1-butene to a reaction axe A equipped with a stirrer and a thermometer, stir and mix evenly, evacuate and introduce nitrogen for 40 minutes, adjust the temperature to 120°C and the pressure to 0.3 MPa, introduce 0.5 mol of propylene oxide, stir and react at constant temperature and pressure for 3 hours, age for 1.5 hours, wait for the reaction pressure to drop to 0.12 MPa, evacuate and react for 30 minutes, and obtain a low molecular weight polyether A;

[0086] S2: Continue to adjust the temperature to 130°C and the pressure to 0.3MPa, introduce 1.5mol of ethylene oxide, stir and react for 3h, age for 2h, wait for the reaction pressure to drop to 0.12MPa, vacuum react for 30min, stop heating, cool the reaction product to room temperature, maintain stirring, add hydrogen peroxide, continue to blow nitrogen and vacuum for 30min, take out the reaction product and place it in deionized water, stir and wash with water at 60r / min for 1h, stand still and separate, take the upper layer of liquid, distill at 100°C under reduced pressure (2kPa) for 20min to obtain high molecular weight polyether A;

[0087] S3: Add 1.5 mol of cis-11-hexadecene-1-ol and potassium hydroxide accounting for 2% of the mass of cis-11-hexadecene-1-ol to a reaction axe B equipped with a stirrer and a thermometer, stir and mix evenly, evacuate and introduce nitrogen for 40 minutes, adjust the temperature to 120° C. and the pressure to 0.3 MPa, introduce 0.5 mol of propylene oxide, stir and react at constant temperature and pressure for 3 hours, age for 1.5 hours, wait for the reaction pressure to drop to 0.12 MPa, evacuate and react for 30 minutes, and obtain a low molecular weight polyether B;

[0088] S4: Continue to adjust the temperature to 130°C and the pressure to 0.3MPa, introduce 1.5mol of ethylene oxide, stir and react for 3h, age for 2h, wait for the reaction pressure to drop to 0.12MPa, vacuum react for 30min, stop heating, cool the reaction product to room temperature, maintain stirring, add hydrogen peroxide, continue to blow nitrogen and vacuum for 30min, take out the reaction product and place it in deionized water, stir and wash with water at 60r / min for 1h, stand still and separate, take the upper layer of liquid, distill at 100°C under reduced pressure (2kPa) for 20min to obtain high molecular weight polyether B;

[0089] S5: Evenly mix the above-mentioned high molecular weight polyether A, high molecular weight polyether B, 2 mol of indole-3-acrylic acid, 0.3% of azobisisobutyronitrile in the total mass of high molecular weight polyether A, high molecular weight polyether B and indole-3-acrylic acid, and 500 ml of xylene, increase the temperature to 60°C, react for 4 hours, and cool to room temperature to obtain a demulsifier.

[0090] In step S2 and step S4, the amount of hydrogen peroxide used twice is the same, and the total amount of hydrogen peroxide used accounts for 2% of the total mass of ethylene oxide and propylene oxide in the entire embodiment.

[0091] Example 5

[0092] The difference between this embodiment and embodiment 4 is that:

[0093] In step S1, the amount of 2,3-dihydroxy-1-butene is 1 mol;

[0094] The rest is the same as Example 4.

[0095] Example 6

[0096] This embodiment provides a demulsifier for oilfield wastewater treatment, and the preparation method of the demulsifier comprises the following steps:

[0097] S1: Add 2 mol of trimethylbutylene glycol and 2% of potassium hydroxide by mass of trimethylbutylene glycol to a reaction axe A equipped with a stirrer and a thermometer, stir and mix evenly, evacuate and introduce nitrogen for 40 minutes, adjust the temperature to 130°C and the pressure to 0.3MPa, introduce 0.5 mol of propylene oxide, stir and react at constant temperature and pressure for 2 hours, age for 0.5 hours, wait for the reaction pressure to drop to 0.12MPa, evacuate and react for 30 minutes, and obtain a low molecular weight polyether A;

[0098] S2: Continue to adjust the temperature to 140°C and the pressure to 0.3MPa, introduce 2 mol of ethylene oxide, stir and react for 2h, age for 1h, wait for the reaction pressure to drop to 0.12MPa, vacuum react for 30min, stop heating, cool the reaction product to room temperature, maintain stirring, add hydrogen peroxide, continue to blow nitrogen and vacuum for 30min, take out the reaction product and place it in deionized water, stir and wash with water at 60r / min for 1h, stand still and separate, take the upper layer of liquid, distill at 100°C under reduced pressure (2kPa) for 20min to obtain high molecular weight polyether A;

[0099] S3: Add 2 mol (Z)-dodec-9-ene-1-ol and 2% potassium hydroxide by mass of (Z)-dodec-9-ene-1-ol to a reaction vessel B equipped with a stirrer and a thermometer, stir and mix evenly, evacuate and introduce nitrogen for 40 min, adjust the temperature to 130° C. and the pressure to 0.3 MPa, introduce 0.5 mol propylene oxide, stir and react at constant temperature and pressure for 2 h, age for 0.5 h, wait for the reaction pressure to drop to 0.12 MPa, evacuate and react for 30 min, and obtain a low molecular weight polyether B;

[0100] S4: Continue to adjust the temperature to 140°C and the pressure to 0.3MPa, introduce 2 mol of ethylene oxide, stir and react for 2h, age for 1h, wait for the reaction pressure to drop to 0.12MPa, vacuum react for 30min, stop heating, cool the reaction product to room temperature, maintain stirring, add hydrogen peroxide, continue to blow nitrogen and vacuum for 30min, take out the reaction product and place it in deionized water, stir and wash with water at 60r / min for 1h, stand still and separate, take the upper layer of liquid, distill at 100°C under reduced pressure (2kPa) for 20min to obtain high molecular weight polyether B;

[0101] S5: Evenly mix the above-mentioned high molecular weight polyether A, high molecular weight polyether B, 3 mol of indole-3-acrylic acid, 0.3% of azobisisobutyronitrile in the total mass of high molecular weight polyether A, high molecular weight polyether B and indole-3-acrylic acid, and 500 ml of xylene, increase the temperature to 80°C, react for 2 hours, and cool to room temperature to obtain a demulsifier.

[0102] In step S2 and step S4, the amount of hydrogen peroxide used twice is the same, and the total amount of hydrogen peroxide used accounts for 2% of the total mass of ethylene oxide and propylene oxide in the entire embodiment.

[0103] Example 7

[0104] The difference between this embodiment and embodiment 6 is that:

[0105] S3: Add 2 mol of cis-11-hexadecene-1-ol and potassium hydroxide accounting for 2% of the mass of cis-11-hexadecene-1-ol to a reaction axe B equipped with a stirrer and a thermometer, stir and mix evenly, evacuate and introduce nitrogen for 40 minutes, adjust the temperature to 130° C. and the pressure to 0.3 MPa, introduce 0.5 mol of propylene oxide, stir and react at constant temperature and pressure for 2 hours, age for 0.5 hours, wait for the reaction pressure to drop to 0.12 MPa, evacuate and react for 30 minutes, and obtain a low molecular weight polyether B;

[0106] S5: Evenly mix the above-mentioned high molecular weight polyether A, high molecular weight polyether B, 3 mol of indole-3-acrylic acid, 1 mol of dimethylvinylsilanol, 0.3% of azobisisobutyronitrile of the total mass of high molecular weight polyether A, high molecular weight polyether B, indole-3-acrylic acid and dimethylvinylsilanol, and 500 ml of xylene, raise the temperature to 80°C, react for 2 hours, and cool to room temperature to obtain a demulsifier.

[0107] The rest is the same as Example 6.

[0108] Example 8

[0109] The difference between this embodiment and embodiment 7 is that:

[0110] S5: half of the high molecular weight polyether A, half of the high molecular weight polyether B, 3 mol of indole-3-acrylic acid, half of the high molecular weight polyether A, half of the high molecular weight polyether B and 0.3% of the total mass of indole-3-acrylic acid by azobisisobutyronitrile and 500 ml of xylene are uniformly mixed to obtain a mixed solution A;

[0111] The other half of the high molecular weight polyether A, the other half of the high molecular weight polyether B, 1 mol of dimethylvinylsilanol, 0.3% of azobisisobutyronitrile by weight of the other half of the high molecular weight polyether A, the other half of the high molecular weight polyether B and dimethylvinylsilanol, and 500 ml of xylene were uniformly mixed to obtain a mixed solution B;

[0112] After the mixed solution A and the mixed solution B are further mixed evenly, the temperature is raised to 70° C., reacted for 2 hours, and then cooled to room temperature to obtain a demulsifier.

[0113] The rest is the same as Example 7.

[0114] Example 9

[0115] The difference between this embodiment and embodiment 8 is that:

[0116] S5: half of the high molecular weight polyether A, half of the high molecular weight polyether B, 3 mol of indole-3-acrylic acid, half of the high molecular weight polyether A, half of the high molecular weight polyether B and 0.3% of the total mass of indole-3-acrylic acid by azobisisobutyronitrile and 500 ml of xylene are uniformly mixed to obtain a mixed solution A;

[0117] The other half of the high molecular weight polyether A, the other half of the high molecular weight polyether B, 2 mol of dimethylvinylsilanol, 0.3% of azobisisobutyronitrile by weight of the total weight of the high molecular weight polyether A, the high molecular weight polyether B, indole-3-acrylic acid and dimethylvinylsilanol, and 500 ml of xylene were uniformly mixed to obtain a mixed solution B;

[0118] After the mixed solution A and the mixed solution B are further mixed evenly, the temperature is raised to 70° C., reacted for 2 hours, and then cooled to room temperature to obtain a demulsifier.

[0119] The rest is the same as Example 8.

[0120] Example 10

[0121] The difference between this embodiment and embodiment 7 is that:

[0122] S5: half of the above high molecular weight polyether A, half of the high molecular weight polyether B, 3 mol of indole-3-acrylic acid, 0.3% of azobisisobutyronitrile by weight of the total weight of half of the high molecular weight polyether A, half of the high molecular weight polyether B and indole-3-acrylic acid, and 500 ml of xylene are mixed uniformly, the temperature is increased to 70° C., reacted for 2 hours, and cooled to room temperature to obtain demulsifier A;

[0123] The other half of the high molecular weight polyether A, the other half of the high molecular weight polyether B, 2 mol of dimethylvinylsilanol, 0.3% of the total weight of azobisisobutyronitrile and 500 ml of xylene were mixed evenly, the temperature was raised to 70° C., reacted for 2 hours, and cooled to room temperature to obtain demulsifier B;

[0124] The demulsifier A and the demulsifier B are mixed evenly to obtain a demulsifier.

[0125] The rest is the same as Example 7.

[0126] Comparative Example 1

[0127] The difference between this comparative example and Example 2 is:

[0128] S5: Evenly mix the above-mentioned high molecular weight polyether A, high molecular weight polyether B, 1 mol of acrylic acid, 0.3% of azobisisobutyronitrile by weight of the total weight of high molecular weight polyether A, high molecular weight polyether B and acrylic acid, and 500 ml of xylene, raise the temperature to 60° C., react for 4 hours, and cool to room temperature to obtain a demulsifier.

[0129] The rest is the same as in Example 2.

[0130] Comparative Example 2

[0131] The difference between this comparative example and Example 2 is:

[0132] S5: Evenly mix the above-mentioned high molecular weight polyether A, high molecular weight polyether B, 0.3% of azobisisobutyronitrile accounting for the total mass of high molecular weight polyether A and high molecular weight polyether B, and 500 ml of xylene, increase the temperature to 60° C., react for 4 hours, and cool to room temperature to obtain a demulsifier.

[0133] The rest is the same as in Example 2.

[0134] Performance Testing

[0135] Experimental raw materials: Oilfield sewage is oil production wastewater, in which the crude oil content is about 1500 mg / L and the suspended solids content is about 200 mg / L.

[0136] Determination standards: SY / T 0530-2011 "Determination of oil content in produced water from oil fields - spectrophotometric method" and SY / T5797-93 "Method for evaluating the performance of demulsifiers for oil-in-water emulsions".

[0137] (1) Detection 1

[0138] Take 12 portions of oil production wastewater, each of which is 500 ml, and pour them into 12 beakers, each of which is 800 ml. Then, place them in a water bath at 60°C for 30 minutes, add 10 mg of demulsifiers prepared in Examples 1 to 10 and Comparative Examples 1 to 2, respectively, stir and react in a constant temperature water bath at 60°C for 10 minutes at a stirring speed of 200 r / min, and then place them in a constant temperature water bath at 60°C for 30 minutes. Determine the oil content (mg / L) in the water phase of the oilfield wastewater after demulsifier treatment, the oil removal rate (%) and the demulsification condition (clarity of the water phase, oil phase and oil-water interface) in each sample. The treatment results are shown in Table 1.

[0139] Table 1 Performance test results of demulsifiers prepared in Examples 1 to 10 and Comparative Examples 1 to 2 after use

[0140]

[0141] By comparing and analyzing the performance test results of the demulsifiers in Example 1 and Example 2, it can be seen that the demulsification effect of the two different polymer structures after cross-linking is stronger than the demulsification effect of a single polymer self-crosslinking. The reason is that different polymer structures can form a more complex network structure after cross-linking. This structure can be better adsorbed on the oil-water interface during the demulsification process, thereby effectively reducing the interfacial tension and promoting the aggregation and separation of water droplets. In contrast, the network structure formed by the self-crosslinking of a single polymer is relatively simple, and its interface adsorption capacity and demulsification effect are relatively weak.

[0142] By comparing and analyzing the performance test results of the demulsifiers in Example 2 and Comparative Examples 1-2, it can be seen that the addition of indole-3-acrylic acid improves the demulsification effect of the demulsifier. The reason is that: first, indole-3-acrylic acid introduces the rigid aromatic structure of the indole ring relative to acrylic acid, so that the molecular structure of the demulsifier has a certain rigidity, which can more effectively destroy the stability of the emulsion, thereby achieving rapid demulsification. Secondly, the indole ring part has a high surface activity, can be preferentially adsorbed to the oil-water interface, and replace or displace the original emulsifier molecules to form a new, less stable interface film, thereby promoting emulsion demulsification.

[0143] By comparing and analyzing the performance test results of the demulsifiers in Examples 2 to 6, it can be seen that by adjusting the amount and type of the synthesized demulsifier reactants, the demulsification effect of the prepared demulsifier is maintained within a good range.

[0144] By comparing and analyzing Examples 7 to 10, the demulsifier obtained by mixing demulsifier A and demulsifier B, due to the interaction between demulsifier A and demulsifier B at the molecular level, helps to form a more stable composite structure, which helps to enhance the demulsification effect. After introducing dimethylvinylsilanol in step S5, the demulsifier obtained has better demulsification performance. This is mainly due to: on the one hand, the silanol group has strong hydrophilicity and surface activity, can be quickly adsorbed on the oil-water interface, and reduce the strength of the interfacial film. On the other hand, the organosilicon interface formed by silanol on the surface of the oil droplet may contribute to the adsorption and distribution of indole-3-acrylic acid, thereby improving the surface properties of the oil droplet, and showing stronger interface absorption capacity and better demulsification performance in the demulsification process.

[0145] (2) Test 2

[0146] Take 3 portions of oil production wastewater, each of which is 500 ml, and pour them into 3 beakers of 800 ml each, and then place them in a water bath at 60° C. for 30 min. Then, add 15 mg, 20 mg, and 30 mg of the demulsifier prepared in Example 10, respectively, stir and react in a constant temperature water bath at 60° C. for 10 min at a stirring speed of 200 r / min. Then, place them in a constant temperature water bath at 60° C. for 30 min. Determine the oil content (mg / L) in the water phase of the oilfield wastewater after demulsifier treatment, the oil removal rate (%), and the demulsification condition (clarity of the water phase, oil phase, and oil-water interface) in each sample. The test results are shown in Table 2.

[0147] Table 2 Performance test results after using different amounts of demulsifier (Example 10)

[0148]

[0149] Analysis of the performance test results in Table 2 shows that the optimal dosage of demulsifier is 40 mg / L. This is because different dosages of demulsifiers have different oil removal rates. This is because the appropriate dosage can ensure that the demulsifier molecules can fully cover the oil-water interface, effectively reduce the interfacial tension, change the contact angle of the droplets or form flocculation, thereby accelerating the coalescence and separation of the droplets. However, if the concentration of the demulsifier is too low, it may not be able to fully cover the interface, resulting in poor demulsification effect; while too high a concentration may have the opposite effect, resulting in poor demulsification effect.

[0150] (3) Test three

[0151] 500 ml of oil production wastewater was taken and poured into an 800 ml beaker, and then placed in a water bath at 60° C. for 30 min, and 20 mg of the demulsifier and 2 mg of polyacrylamide prepared in Example 10 were added in sequence, and stirred in a constant temperature water bath at 60° C. for 10 min, with a stirring speed of 200 r / min, and then placed in a constant temperature water bath at 60° C. for 30 min. The oil content (mg / L) in the water phase, the oil removal rate (%) and the demulsification condition (clarity of the water phase, the oil phase and the oil-water interface) of the oilfield wastewater after demulsifier treatment were determined in each sample. The test results are shown in Table 3.

[0152] Table 3 Performance test results of the demulsifier prepared in Example 10 after compounding with polyacrylamide

[0153]

[0154] Analysis of the performance test results in Table 3 shows that the demulsifier prepared in Example 10 has a better demulsification effect after being compounded with polyacrylamide. This is mainly because the silanol in the demulsifier is negatively charged, which helps the adsorption and deposition of polyacrylamide on the surface of the silanol, and through its flocculation, it helps to demulsify and promote oil-water separation.

[0155] In addition, the presence of indole ring in the demulsifier optimizes the attachment of polyacrylamide to the surface of oil droplets, further promoting oil-water separation.

Claims

1. A demulsifier for oilfield wastewater treatment, characterized in that: The preparation method of the demulsifier comprises the following steps: S1: After monomer A, monomer B and catalyst are uniformly mixed, propylene oxide is added and mixed uniformly, reacted at 120-130°C for 2-3h, and aged for 0.5-1.5h to obtain a low molecular weight polyether; S2: adding ethylene oxide to the low molecular weight polyether of step S1, mixing evenly, heating to 130-140° C., reacting for 2-3 hours, aging for 1-2 hours, cooling, adding hydrogen peroxide, continuously blowing nitrogen and evacuating, and washing to obtain a high molecular weight polyether; S3: Evenly mix the high molecular weight polyether, monomer C, initiator and solvent in S2, raise the temperature to 55-80°C, react for 2-4 hours, and cool down to obtain a demulsifier; The monomer A and the monomer B are both alcohols containing carbon-carbon double bonds; the monomer C is indole-3-acrylic acid; The amount of hydrogen peroxide used accounts for 2% of the total mass of ethylene oxide and propylene oxide; The ratio of the total moles of monomer A and monomer B, the moles of propylene oxide, the moles of ethylene oxide, and the moles of monomer C is 3-4:0.5-1:1.5-4:1-3, and the molar ratio of monomer A to monomer B is 1-2:1-2; The monomer A is any one of 2,3-dihydroxy-1-butene and trimethylbutenediol; The monomer B is any one of cis-11-hexadecene-1-ol and (Z)-dodec-9-ene-1-ol.

2. A demulsifier for oilfield wastewater treatment according to claim 1, characterized in that: In the step S1, after the monomer A and the catalyst are evenly mixed, propylene oxide is added and mixed evenly, and the mixture is reacted at 120-130° C. for 2-3 hours, and then aged for 0.5-1.5 hours to obtain a low molecular weight polyether A; After the monomer B and the catalyst are mixed evenly, propylene oxide is added and mixed evenly, and the mixture is reacted at 120-130°C for 2-3 hours, and then aged for 0.5-1.5 hours to obtain a low molecular weight polyether B; In the step S2, ethylene oxide is added to the low molecular weight polyether A of step S1, mixed evenly, heated to 130-140° C., reacted for 2-3 hours, aged for 1-2 hours, cooled, hydrogen peroxide is added, nitrogen is continuously blown and vacuumed, and then washed to obtain a high molecular weight polyether A; Add ethylene oxide to the low molecular weight polyether B in step S1, mix evenly, heat to 130-140° C., react for 2-3 hours, age for 1-2 hours, cool, add hydrogen peroxide, continue to blow nitrogen, evacuate, and wash to obtain a high molecular weight polyether B; In the step S3, the high molecular weight polyether A, high molecular weight polyether B, monomer C, initiator and solvent in S2 are uniformly mixed, the temperature is increased to 60-80° C., reacted for 2-4 hours, and cooled to obtain a demulsifier; The amount of hydrogen peroxide used twice is the same, and the total amount of hydrogen peroxide used accounts for 2% of the total mass of ethylene oxide and propylene oxide.

3. A demulsifier for oilfield wastewater treatment according to claim 2, characterized in that: In step S3, a monomer D is also added, wherein the monomer D is dimethylvinylsilanol, and the molar ratio of the monomer C to the monomer D is 3:1-2.

4. A demulsifier for oilfield wastewater treatment according to claim 3, characterized in that: In step S3, a portion of the high molecular weight polyether A, a portion of the high molecular weight polyether B, the monomer C, the initiator and the solvent in S2 are uniformly mixed to obtain a mixed solution A; The other part of the high molecular weight polyether A in S2, the other part of the high molecular weight polyether B, the monomer D, the initiator and the solvent are uniformly mixed to obtain a mixed solution B; After the mixed solution A and the mixed solution B are evenly mixed, the temperature is raised to 60-80°C, reacted for 2-4 hours, and then cooled to room temperature to obtain a demulsifier.

5. A demulsifier for oilfield wastewater treatment according to claim 4, characterized in that: In step S3, a portion of the high molecular weight polyether A in S2, a portion of the high molecular weight polyether B, the monomer C, the initiator and the solvent are uniformly mixed, the temperature is increased to 60-80° C., the reaction is carried out for 2-4 hours, and the temperature is cooled to room temperature to obtain a demulsifier A; The other part of the high molecular weight polyether A in S2, the other part of the high molecular weight polyether B, the monomer D, the initiator and the solvent are uniformly mixed, the temperature is increased to 60-80°C, the reaction is carried out for 2-4 hours, and the temperature is cooled to room temperature to obtain a demulsifier B; The demulsifier A and the demulsifier B are mixed evenly to obtain a demulsifier.

6. A demulsifier for oilfield wastewater treatment according to any one of claims 1 to 5, characterized in that: The demulsifier can also be used in combination with polyacrylamide.

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