A crude oil demulsifier and its preparation method

Abstract

This invention relates to the field of petroleum processing aids technology, and discloses a crude oil demulsifier and its preparation method. The crude oil demulsifier prepared by this invention differs from traditional demulsifiers that use linear polyethers as the main component. It is prepared by surface modification of hyperbranched polyether with Fe3O4@MOF-Cu nanomaterials, followed by mixing with water and methanol. This demulsifier not only achieves efficient demulsification during crude oil demulsification but can also be recycled, reducing demulsification costs.

Description

Technical Field

[0001] This invention relates to the field of petroleum processing aids technology, specifically to a crude oil demulsifier and its preparation method. Background Technology

[0002] During crude oil extraction, the presence of formation water and the intense shear forces applied during production typically lead to the formation of stable W / O emulsions. These emulsions increase crude oil viscosity, impacting production efficiency, transportation safety, and processing economics. Among various demulsification methods, chemical demulsifiers are the most widely used industrially due to their high efficiency, ease of operation, and relatively low cost. Traditional demulsifiers, such as block polyoxypropylene-polyoxyethylene, have dominated the field for decades. These demulsifiers adsorb onto the oil-water interface, replacing natural emulsifiers, and alter the rheological properties of the interfacial film through the movement of their hydrophilic-lipophilic segments, thereby achieving demulsification.

[0003] However, as crude oil extraction progresses into its later stages, the composition of the produced fluid becomes increasingly complex. Furthermore, to meet the demands of extraction in harsh environments such as the deep sea, traditional polyether demulsifiers have gradually revealed numerous limitations: (1) Limited demulsification and defoaming: their demulsification efficiency depends on molecular weight and hydrolytic stability. Excessively large molecular weight results in slow diffusion, while excessively small molecular weight leads to insufficient interfacial film strength; (2) Environmental friendliness and recycling issues: most demulsifiers are single-use and cannot be recycled, increasing costs and potentially creating an environmental burden. Therefore, to overcome these shortcomings, developing a novel crude oil demulsifier that is efficient, fast, recyclable, environmentally friendly, and widely adaptable has become a pressing technical challenge in this field. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a crude oil demulsifier and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a crude oil demulsifier, comprising the following steps:

[0007] Step S1: Disperse Fe3O4@MOF-Cu nanomaterials uniformly in tetrahydrofuran, add modified hyperbranched polyether, heat to 70℃, reflux under nitrogen for 48h, centrifuge, wash, and dry to obtain the composite product.

[0008] Step S2: Mix the composite product in a mixture of water and methanol until homogeneous to obtain the crude oil demulsifier.

[0009] Further, the mass ratio of Fe3O4@MOF-Cu nanomaterials and modified hyperbranched polyether in step S1 is 3-5:10-15;

[0010] Furthermore, the content of the composite product in the crude oil demulsifier described in step S2 is 45-55 wt%, and the remainder is a mixture of water and methanol, with a mass ratio of water to methanol of 7:3.

[0011] The Fe3O4@MOF-Cu nanomaterial was prepared by the following steps:

[0012] Step A1: Disperse Fe3O4 nanomaterials ultrasonically in a mixture of ethanol and water for 30 min, add APTES, and reflux and stir at 70°C for 8-10 h. After the reaction is complete, separate the product with a magnet, wash and dry to obtain amination Fe3O4 nanomaterials.

[0013] Furthermore, in step A1, the ratio of Fe3O4 nanomaterials, ethanol, water, and APTES is 0.3g:30mL:5mL:0.2-0.3mL;

[0014] Step A2: Mix copper nitrate trihydrate evenly in water to obtain copper nitrate solution; mix 2-aminoterephthalic acid (H3BTC) evenly in DMF and anhydrous ethanol to obtain H3BTC solution; add copper nitrate solution to H3BTC solution and sonicate for 30 min, then add amination Fe3O4 nanomaterials and sonicate for 20 min, then transfer to autoclave and hydrothermally react at 120℃ for 24 h, cool, filter, wash and dry to obtain Fe3O4@MOF-Cu nanomaterials;

[0015] Furthermore, in step A2, the ratio of copper nitrate solution, H3BTC solution, and amination Fe3O4 nanomaterials is 15mL:25mL:0.8-1.2g;

[0016] Further, in step A2, the ratio of copper nitrate trihydrate to water in the copper nitrate solution is 0.97-1.03 g: 15 mL, and the ratio of H3BTC, DMF, and anhydrous ethanol in the H3BTC solution is 0.42-0.5 g: 15 mL: 10 mL.

[0017] The modified hyperbranched polyether is prepared by the following steps:

[0018] Step B1: Under nitrogen atmosphere, tris(hydroxymethyl)aminomethane, 4-dimethylaminobutyrate, DMF and concentrated sulfuric acid are stirred evenly, then heated to 120°C and refluxed for 8 hours. Triethylamine is then added and stirred for 30 minutes. The triethylamine hydrochloride is removed by filtration, then poured into water, shaken and allowed to stand to separate into layers. The organic layer is washed and dried to obtain monomer 1.

[0019] Further, in step B1, the ratio of tris(hydroxymethyl)aminomethane, 4-dimethylaminobutyrate, DMF, concentrated sulfuric acid, and triethylamine is 0.01 mol: 0.01-0.012 mol: 200 mL: 0.06-0.1 mL: 0.01-0.012 mol;

[0020] Further, the organic layer washing in step B1 involves washing three times each with 0.1 mol / L sodium bicarbonate solution and water;

[0021] Step B2: Add trimethylolpropane triglycidyl ether and tetrabutylammonium bromide to DMF and mix and stir evenly. Then add monomer 1 and react under nitrogen at 90°C for 4 hours. Then add tetrahydrofuran and stir evenly. Wash and dry to obtain hyperbranched polyether.

[0022] Further, in step B2, the ratio of trimethylolpropane triglycidyl ether, tetrabutylammonium bromide, DMF, monomer 1, and tetrahydrofuran is 0.2-0.3 mol: 0.01-0.015 mol: 100 mL: 0.08-0.15 mol: 100 mL;

[0023] Step B3: Under nitrogen protection, the hyperbranched polyether is mixed and stirred evenly in DMF, then heated to 100℃, and then dichloroethyl ether is added to the system at a rate of 1 drop / min. The mixture is stirred and reacted for 4 hours, and then distilled under reduced pressure to obtain the modified hyperbranched polyether.

[0024] Furthermore, in step B3, the ratio of hyperbranched polyether, DMF, and dichloroethyl ether is 0.1 mol: 100 mL: 0.02-0.06 mol.

[0025] Secondly, the present invention also provides a crude oil demulsifier, which is prepared by the preparation method described in the first aspect.

[0026] The beneficial effects of this invention are:

[0027] The crude oil demulsifier prepared by this invention is made by modifying hyperbranched polyether with Fe3O4@MOF-Cu nanomaterials, and then mixing it with water and methanol. This demulsifier can not only demulsify efficiently in the crude oil demulsification process, but also be recycled, thus reducing the demulsification cost.

[0028] The crude oil demulsifier prepared in this invention differs from traditional polyether demulsifiers. This demulsifier not only incorporates a hyperbranched polyether structure but also magnetic nanomaterials (Fe3O4@MOF-Cu nanomaterials), quaternary ammonium salt cations, and amide bonds. Their synergistic effect rapidly and efficiently disrupts the stability of crude oil emulsions, promoting the aggregation and coalescence of tiny water droplets, ultimately separating them from the crude oil. The hyperbranched polyether, as the core of the demulsifier, utilizes its three-dimensional spherical, highly branched structure and numerous terminal ether bonds (-O-) and hydroxyl groups (-OH) to rapidly diffuse onto the oil-water interface film. After occupying the interface, it significantly reduces the interfacial tension and forms a new, but weaker, interfacial film. This new film is insufficient to support the stable existence of water droplets, leading to the rupture of the interfacial film and thus achieving the demulsification effect. Hyperbranched polyethers also contain amide bonds and quaternary ammonium salt cations. The amide bonds can form strong hydrogen bonds with polar groups (such as carboxyl groups and phenolic hydroxyl groups) on natural emulsifier molecules such as asphaltene and gum. This hydrogen bonding effect is equivalent to "anchoring" the demulsifier molecules to the natural emulsifier, thereby "pulling" the natural emulsifier off the interface or causing it to lose its emulsifying activity, directly destroying the original stable system. Meanwhile, the quaternary ammonium salt cations can neutralize the negative charge on the surface of water droplets in crude oil emulsions and eliminate the electrostatic repulsion between water droplets, which makes it easier for water droplets to approach, collide and merge with each other.

[0029] The introduction of Fe3O4@MOF-Cu nanomaterials into the demulsifier provides a huge loading platform for hyperbranched polyethers, greatly increasing the number of active sites. Furthermore, the nanoscale particles can more easily penetrate into the tight interfacial film, generating a stronger steric hindrance effect, disrupting the integrity of the interfacial film, and further improving the demulsification efficiency. In addition, as a superparamagnetic material, Fe3O4 allows the entire demulsifier to be controlled by an external magnetic field. After demulsification, the demulsifier that has adsorbed water droplets and impurities can be quickly and easily separated and recovered from the system through the magnetic field. This not only improves the demulsification efficiency but also enables the recycling of the demulsifier, which is in line with the concept of green chemistry. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1: Fe3O4@MOF-Cu nanomaterials were prepared by the following steps:

[0032] Step A1: Disperse 0.3g of Fe3O4 nanomaterials in a mixture of 30mL ethanol and 5mL water by ultrasonication for 30min, add 0.2mL APTES, and reflux and stir at 70℃ for 8h. After the reaction is complete, separate the product with a magnet, wash and dry to obtain amination Fe3O4 nanomaterials.

[0033] Step A2: Mix 0.97g of copper nitrate trihydrate with 15mL of water to obtain a copper nitrate solution; mix 0.42g of 2-aminoterephthalic acid with 15mL of DMF and 10mL of anhydrous ethanol to obtain an H3BTC solution; add 15mL of copper nitrate solution to 25mL of H3BTC solution and sonicate for 30min, then add 0.8g of amination Fe3O4 nanomaterials and sonicate for 20min, then transfer to an autoclave and hydrothermally react at 120℃ for 24h. After cooling, filter, wash, and dry to obtain Fe3O4@MOF-Cu nanomaterials.

[0034] The modified hyperbranched polyether is prepared by the following steps:

[0035] Step B1: Under nitrogen atmosphere, 0.01 mol of tris(hydroxymethyl)aminomethane, 0.01 mol of 4-dimethylaminobutyrate, 200 mL of DMF and 0.06 mL of concentrated sulfuric acid were stirred until homogeneous. The mixture was then heated to 120 °C and refluxed for 8 h. 0.01 mol of triethylamine was added and stirred for 30 min. The triethylamine hydrochloride was removed by filtration. The mixture was then poured into water, shaken, and allowed to stand to separate into layers. The organic layer was washed and dried to obtain monomer 1. The organic layer was washed three times each with 0.1 mol / L sodium bicarbonate solution and water.

[0036] Step B2: Add 0.2 mol of trimethylolpropane triglycidyl ether and 0.01 mol of tetrabutylammonium bromide to 100 mL of LDMF and mix well. Then add 0.08 mol of monomer 1 and react at 90 °C under nitrogen for 4 h. Then add 100 mL of tetrahydrofuran and stir well. Wash and dry to obtain hyperbranched polyether.

[0037] Step B3: Under nitrogen protection, 0.1 mol of hyperbranched polyether is mixed and stirred evenly in 100 mL of DMF, then heated to 100 °C. Subsequently, 0.02 mol of dichloroethyl ether is added dropwise to the system at a rate of 1 drop / min. The mixture is stirred and reacted for 4 h. The mixture is then distilled under reduced pressure to obtain the modified hyperbranched polyether.

[0038] Example 2: Fe3O4@MOF-Cu nanomaterials were prepared by the following steps:

[0039] Step A1: Disperse 0.3g of Fe3O4 nanomaterials in a mixture of 30mL ethanol and 5mL water by ultrasonication for 30min, add 0.25mL APTES, and reflux at 70℃ for 9h. After the reaction is complete, separate the product with a magnet, wash and dry to obtain amination Fe3O4 nanomaterials.

[0040] Step A2: Mix 1.0 g of copper nitrate trihydrate with 15 mL of water to obtain a copper nitrate solution; mix 0.45 g of 2-aminoterephthalic acid with 15 mL of DMF and 10 mL of anhydrous ethanol to obtain an H3BTC solution; add 15 mL of copper nitrate solution to 25 mL of H3BTC solution and sonicate for 30 min, then add 1.0 g of amination Fe3O4 nanomaterials and sonicate for 20 min, then transfer to an autoclave and hydrothermally react at 120 °C for 24 h. After cooling, filter, wash, and dry to obtain Fe3O4@MOF-Cu nanomaterials.

[0041] The modified hyperbranched polyether is prepared by the following steps:

[0042] Step B1: Under nitrogen atmosphere, 0.01 mol of tris(hydroxymethyl)aminomethane, 0.011-0.012 mol of 4-dimethylaminobutyrate, 200 mL of DMF, and 0.08 mL of concentrated sulfuric acid were stirred until homogeneous. The mixture was then heated to 120 °C and refluxed for 8 h. 0.011 mol of triethylamine was then added and stirred for 30 min. The triethylamine hydrochloride was removed by filtration. The mixture was then poured into water, shaken, and allowed to stand to separate into layers. The organic layer was washed and dried to obtain monomer 1. The organic layer was washed three times each with 0.1 mol / L sodium bicarbonate solution and water.

[0043] Step B2: Add 0.25 mol of trimethylolpropane triglycidyl ether and 0.013 mol of tetrabutylammonium bromide to 100 mL of DMF and mix well. Then add 0.12 mol of monomer 1 and react at 90 °C under nitrogen for 4 h. Then add 100 mL of tetrahydrofuran and stir well. Wash and dry to obtain hyperbranched polyether.

[0044] Step B3: Under nitrogen protection, 0.1 mol of hyperbranched polyether is mixed and stirred evenly in 100 mL of DMF, then heated to 100 °C. Subsequently, 0.04 mol of dichloroethyl ether is added dropwise to the system at a rate of 1 drop / min. The mixture is stirred and reacted for 4 h. The mixture is then distilled under reduced pressure to obtain the modified hyperbranched polyether.

[0045] Example 3: Fe3O4@MOF-Cu nanomaterials were prepared by the following steps:

[0046] Step A1: Disperse 0.3g of Fe3O4 nanomaterials in a mixture of 30mL ethanol and 5mL water by ultrasonication for 30min, add 0.3mL APTES, and reflux and stir at 70℃ for 10h. After the reaction is complete, separate the product with a magnet, wash and dry to obtain amination Fe3O4 nanomaterials.

[0047] Step A2: Mix 1.03g of copper nitrate trihydrate with 15mL of water to obtain a copper nitrate solution; mix 0.5g of 2-aminoterephthalic acid with 15mL of DMF and 10mL of anhydrous ethanol to obtain an H3BTC solution; add 15mL of copper nitrate solution to 25mL of H3BTC solution and sonicate for 30min, then add 1.2g of amination Fe3O4 nanomaterials and sonicate for 20min, then transfer to an autoclave and hydrothermally react at 120℃ for 24h. After cooling, filter, wash, and dry to obtain Fe3O4@MOF-Cu nanomaterials.

[0048] The modified hyperbranched polyether is prepared by the following steps:

[0049] Step B1: Under nitrogen atmosphere, 0.01 mol of tris(hydroxymethyl)aminomethane, 0.012 mol of 4-dimethylaminobutyrate, 200 mL of DMF and 0.1 mL of concentrated sulfuric acid were stirred until homogeneous. The mixture was then heated to 120 °C and refluxed for 8 h. 0.012 mol of triethylamine was then added and stirred for 30 min. The triethylamine hydrochloride was removed by filtration. The mixture was then poured into water, shaken, and allowed to stand to separate into layers. The organic layer was washed and dried to obtain monomer 1. The organic layer was washed three times each with 0.1 mol / L sodium bicarbonate solution and water.

[0050] Step B2: Add 0.3 mol of trimethylolpropane triglycidyl ether and 0.015 mol of tetrabutylammonium bromide to 100 mL of DMF and mix well. Then add 0.15 mol of monomer 1 and react at 90 °C under nitrogen for 4 h. Then add 100 mL of tetrahydrofuran and stir well. Wash and dry to obtain hyperbranched polyether.

[0051] Step B3: Under nitrogen protection, 0.1 mol of hyperbranched polyether is mixed and stirred evenly in 100 mL of DMF, then heated to 100 °C. Subsequently, 0.06 mol of dichloroethyl ether is added dropwise to the system at a rate of 1 drop / min. The mixture is stirred and reacted for 4 h. The mixture is then distilled under reduced pressure to obtain the modified hyperbranched polyether.

[0052] Example 4: A method for preparing a crude oil demulsifier, comprising the following steps:

[0053] Step S1: Disperse 3g of Fe3O4@MOF-Cu nanomaterial prepared in Example 1 evenly in 50mL of tetrahydrofuran, then add 10g of modified hyperbranched polyether prepared in Example 1, heat to 70℃, reflux under nitrogen for 48h, centrifuge, wash, and dry to obtain the composite product.

[0054] Step S2: Mix the composite product evenly in a mixture of water and methanol to obtain the crude oil demulsifier. The content of the composite product in the crude oil demulsifier is 45 wt%, and the remainder is a mixture of water and methanol with a mass ratio of 7:3.

[0055] Example 5: A method for preparing a crude oil demulsifier, comprising the following steps:

[0056] Step S1: Disperse 4g of Fe3O4@MOF-Cu nanomaterial prepared in Example 2 evenly in 50mL of tetrahydrofuran, then add 12g of modified hyperbranched polyether prepared in Example 2, heat to 70℃, reflux under nitrogen for 48h, centrifuge, wash and dry to obtain the composite product.

[0057] Step S2: Mix the composite product evenly in a mixture of water and methanol to obtain the crude oil demulsifier. The content of the composite product in the crude oil demulsifier is 50 wt%, and the remainder is a mixture of water and methanol with a mass ratio of 7:3.

[0058] Example 6: A method for preparing a crude oil demulsifier, comprising the following steps:

[0059] Step S1: Disperse 5g of Fe3O4@MOF-Cu nanomaterial prepared in Example 3 evenly in 50mL of tetrahydrofuran, then add 15g of modified hyperbranched polyether prepared in Example 3, heat to 70℃, reflux under nitrogen for 48h, centrifuge, wash and dry to obtain the composite product.

[0060] Step S2: Mix the composite product evenly in a mixture of water and methanol to obtain the crude oil demulsifier. The content of the composite product in the crude oil demulsifier is 55 wt%, and the remainder is a mixture of water and methanol with a mass ratio of 7:3.

[0061] Comparative Example 1: This comparative example is a crude oil demulsifier, which is prepared by mixing hyperbranched polyether in a mixture of water and methanol. The polyether content is 55 wt%, and the remainder is a mixture of water and methanol with a mass ratio of 7:3.

[0062] Comparative Example 2: This comparative example is a crude oil demulsifier, which is prepared by mixing and stirring polyoxyethylene polyoxypropylene octadecyl alcohol ether in a mixture of water and methanol. The content of polyether is 55 wt%, and the balance is a mixture of water and methanol with a mass ratio of 7:3.

[0063] Comparative Example 3: This comparative example is a crude oil demulsifier, specifically demulsifier T1001.

[0064] The performance of the crude oil demulsifiers prepared in Examples 4-6 and Comparative Examples 1-3 was tested:

[0065] Weigh 150g of crude oil into a beaker, add 350g of water, and then preheat in a constant temperature water bath at 50℃ for 30 minutes. Then, use a high shear dispersion emulsifier (GS-I) to stir three times at a speed of 11000rpm for 5 minutes each time until the water and oil phases are completely mixed and homogeneous, which is a stable oil-in-water emulsion.

[0066] Demulsification efficiency: According to SY / T 5281-2000 "Test Method for Performance of Crude Oil Demulsifiers (Bottle Test Method)", the demulsification performance was evaluated using the bottle test method; according to the China Petroleum and Natural Gas Industry Standard SY / T 0530-2011 "Determination of Oil Content in Oilfield Produced Water - Spectrophotometric Method", the residual oil content in the treated aqueous phase was determined, and the calculation formula is shown in (2-1): DE=(C0-C1) 100%, DE (%) is the demulsification efficiency, C0 and C1 are the initial concentration in the original emulsion and the concentration of residual oil in the aqueous phase, respectively, mg / L. Take 1L of stable oil-in-water emulsion, the demulsification temperature is 35℃, the demulsification time is 20min, and the demulsification efficiency is tested when the dosage is 200mg, 300mg and 400mg.

[0067] Cycle test: Under the influence of a magnetic field, 400 mg of the demulsifier from the example and the comparative example were added to every 1 mL of stable oil-in-water emulsion for 8 rounds of repeated "demulsification-recovery-demulsification" test, and then the demulsification efficiency was calculated.

[0068] The test results are shown in Table 1:

[0069] Table 1: Performance Test Results

[0070]

[0071] As can be seen from Table 1, the demulsifier prepared by this invention not only has excellent demulsification performance, but also has the advantages of high efficiency and environmental friendliness. Furthermore, it can be recycled by utilizing the magnetic components in the demulsifier, thereby reducing the cost of crude oil extraction.

[0072] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a crude oil demulsifier, characterized in that, Includes the following steps: Step S1: Disperse Fe3O4@MOF-Cu nanomaterials uniformly in tetrahydrofuran, add modified hyperbranched polyether, heat to 70℃, reflux under nitrogen for 48h, centrifuge, wash, and dry to obtain the composite product. The mass ratio of Fe3O4@MOF-Cu nanomaterials to modified hyperbranched polyether is 3-5:10-15. Step S2: Mix the composite product in a mixture of water and methanol until homogeneous to obtain the crude oil demulsifier. The content of the composite product is 45-55 wt%, and the remainder is a mixture of water and methanol with a mass ratio of 7:

3. The modified hyperbranched polyether is prepared by reacting hyperbranched polyether with dichloroethyl ether. The hyperbranched polyether is prepared by reacting trimethylolpropane triglycidyl ether with monomer 1. The monomer 1 is prepared by reacting trimethylolaminomethane with 4-dimethylaminobutyrate salt.

2. The method for preparing a crude oil demulsifier according to claim 1, characterized in that, The Fe3O4@MOF-Cu nanomaterial was prepared by the following steps: Step A1: Disperse Fe3O4 nanomaterials ultrasonically in a mixture of ethanol and water for 30 min, add APTES, and reflux and stir at 70°C for 8-10 h. After the reaction is complete, separate the product with a magnet, wash and dry to obtain amination Fe3O4 nanomaterials. Step A2: Mix copper nitrate trihydrate evenly in water to obtain copper nitrate solution; mix 2-aminoterephthalic acid evenly in DMF and anhydrous ethanol to obtain H3BTC solution; Copper nitrate solution was added to H3BTC solution and ultrasonically mixed for 30 min. Then, amination Fe3O4 nanomaterials were added and ultrasonically mixed for 20 min. The mixture was then transferred to an autoclave and hydrothermally reacted at 120℃ for 24 h. After cooling, the mixture was filtered, washed, and dried to obtain Fe3O4@MOF-Cu nanomaterials.

3. The method for preparing a crude oil demulsifier according to claim 2, characterized in that, In step A1, the ratio of Fe3O4 nanomaterials, ethanol, water and APTES is 0.3g:30mL:5mL:0.2-0.3mL.

4. The method for preparing a crude oil demulsifier according to claim 2, characterized in that, In step A2, the ratio of copper nitrate solution, H3BTC solution, and amination Fe3O4 nanomaterials is 15mL:25mL:0.8-1.2g. The ratio of copper nitrate trihydrate to water in the copper nitrate solution is 0.97-1.03g:15mL. The ratio of H3BTC, DMF, and anhydrous ethanol in the H3BTC solution is 0.42-0.5g:15mL:10mL.

5. The method for preparing a crude oil demulsifier according to claim 1, characterized in that, The modified hyperbranched polyether is prepared by the following steps: Step B1: Under nitrogen atmosphere, tris(hydroxymethyl)aminomethane, 4-dimethylaminobutyrate, DMF and concentrated sulfuric acid are stirred evenly, then heated to 120°C and refluxed for 8 hours. Triethylamine is then added and stirred for 30 minutes. The triethylamine hydrochloride is removed by filtration, then poured into water, shaken and allowed to stand to separate into layers. The organic layer is washed and dried to obtain monomer 1. Step B2: Add trimethylolpropane triglycidyl ether and tetrabutylammonium bromide to DMF and mix and stir evenly. Then add monomer 1 and react under nitrogen at 90°C for 4 hours. Then add tetrahydrofuran and stir evenly. Wash and dry to obtain hyperbranched polyether. Step B3: Under nitrogen protection, the hyperbranched polyether is mixed and stirred evenly in DMF, then heated to 100℃, and then dichloroethyl ether is added to the system at a rate of 1 drop / min. The mixture is stirred and reacted for 4 hours, and then distilled under reduced pressure to obtain the modified hyperbranched polyether.

6. The method for preparing a crude oil demulsifier according to claim 5, characterized in that, In step B1, the ratio of tris(hydroxymethyl)aminomethane, 4-dimethylaminobutyrate, DMF, concentrated sulfuric acid, and triethylamine is 0.01 mol: 0.01-0.012 mol: 200 mL: 0.06-0.1 mL: 0.01-0.012 mol.

7. The method for preparing a crude oil demulsifier according to claim 5, characterized in that, The organic layer washing in step B1 involves washing three times each with 0.1 mol / L sodium bicarbonate solution and water.

8. The method for preparing a crude oil demulsifier according to claim 5, characterized in that, In step B2, the ratio of trimethylolpropane triglycidyl ether, tetrabutylammonium bromide, DMF, monomer 1, and tetrahydrofuran is 0.2-0.3 mol: 0.01-0.015 mol: 100 mL: 0.08-0.15 mol: 100 mL.

9. The method for preparing a crude oil demulsifier according to claim 5, characterized in that, In step B3, the ratio of hyperbranched polyether, DMF and dichloroethyl ether is 0.1 mol: 100 mL: 0.02-0.06 mol.

10. A crude oil demulsifier, characterized in that, The crude oil demulsifier is prepared by the preparation method according to any one of claims 1-9.

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