A Highly Efficient Heavy Crude Oil Demulsifier and Its Preparation Method

Abstract

This invention discloses a high-efficiency heavy crude oil demulsifier and its preparation method. The structural formula of the high-efficiency heavy crude oil demulsifier is shown in formula (I), where m = 1-200, R is x = 1-600, and y = 1-600. The high-efficiency heavy crude oil demulsifier provided by this technical solution undergoes chemical modification, where quaternary ammonium salt polymers form covalent bonds with polyether bases to form cationic modified polyethers as a new demulsifier molecular structure. This enhances product stability and avoids the problems of component stratification and poor compatibility that may occur with simple compounding. The modified demulsifier is more stable during storage, transportation, and use, and its product performance is more consistent. This high-efficiency heavy crude oil demulsifier exhibits good demulsification performance, requires less dosage, has a fast demulsification speed, high dehydration rate, uniform interface, and good aqueous phase cleanliness.

Description

Technical Field

[0001] This invention relates to the field of heavy crude oil demulsifier technology, and in particular to a high-efficiency heavy crude oil demulsifier and its preparation method. Background Technology

[0002] As a non-renewable resource, petroleum occupies an irreplaceable strategic position in national security fields such as defense and aerospace, as well as in industry, agriculture, and daily life. Crude oil extraction requires the injection of large amounts of water into the formation. In particular, the widespread application of enhanced oil recovery technologies such as polymer flooding, surfactant flooding, and multi-component composite flooding makes it easy for produced fluids in oilfields to form stable water-in-oil, oil-in-water, and complex water-in-oil emulsions. The presence of emulsions leads to a series of problems, including increased crude oil transportation costs, equipment and pipeline corrosion, and waste of oil resources. Therefore, oil-water separation of produced emulsions is crucial before crude oil transportation and processing, and demulsification technology plays a vital role in the demulsification process of produced emulsions in the petroleum industry.

[0003] Currently, common demulsification methods mainly include the addition of chemical demulsifiers, physical demulsification, and biological demulsification. Among them, chemical demulsifiers are widely used in oil-water separation due to their advantages such as simple operation, fast demulsification speed, and relatively low demulsification cost. However, heavy crude oil contains a high proportion of gums and asphaltenes, and has the characteristics of high density and high viscosity. Existing technologies for heavy crude oil still have problems such as large demulsifier dosage, high processing cost, slow demulsification speed, long processing cycle, and high oil content in the dewatered water.

[0004] Patent application CN107057754A discloses a demulsifier suitable for heavy crude oil emulsions with high water content. This demulsifier promotes oil phase aggregation and flocculation by adding a cationic polymer, thereby accelerating oil-water separation. However, this demulsifier is prone to problems such as component stratification and poor compatibility during use, and it is also prone to deterioration during storage, transportation, and use, resulting in unstable product performance.

[0005] Therefore, developing a new type of efficient, economical, and environmentally friendly heavy crude oil demulsifier is of great practical significance. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a stable and efficient heavy crude oil demulsifier and its preparation method, thereby achieving rapid and efficient demulsification, reducing processing costs, and improving crude oil quality.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A highly efficient heavy crude oil demulsifier, with the structural formula shown in formula (I):

[0009] (Formula I);

[0010] Where m = 1 - 200, R is x = 1 - 600, y = 1 - 600.

[0011] A method for preparing a highly efficient heavy crude oil demulsifier as described above involves reacting 3,5-difluorophenol with tetraethylenepentamine and formaldehyde solution to obtain an initiator. The initiator, propylene oxide, and ethylene oxide undergo block polymerization under a catalyst to obtain a polyether base. The polyether base reacts with an isocyanate-terminated quaternary ammonium salt polymer to obtain a highly efficient heavy crude oil demulsifier as shown in formula (I), with the following reaction formula:

[0012] ;

[0013] Wherein: PO is propylene oxide, EO is ethylene oxide, m=1-200, x=1-600, y=1-600.

[0014] As a preferred option, the following steps are included:

[0015] (1) Take 1-10 parts by weight of 3,5-difluorophenol and 5-50 parts by weight of tetraethylenepentamine, stir and mix, heat to 40 °C, then add 1-10 parts by weight of formaldehyde solution, keep the reaction at the temperature for 50 min after the addition is complete, add solvent, reflux to dehydrate for 2 h, evaporate the solvent, continue the reaction for 2 h to obtain the initiator;

[0016] (2) Take 10-100 parts by weight of the above-mentioned initiator and 0-50 parts by weight of the catalyst and introduce 10-50000 parts by weight of propylene oxide into a high-temperature and high-pressure reactor under inert gas protection. Control the reaction temperature and pressure. When the pressure in the reactor decreases to zero, the reaction ends and an intermediate is obtained. Take the obtained intermediate and 0-50 parts by weight of the catalyst and introduce 100-80000 parts by weight of ethylene oxide into a high-temperature and high-pressure reactor under inert gas protection. Control the reaction temperature and pressure. When the pressure in the reactor decreases to zero, the reaction ends and a polyether base is obtained.

[0017] (3) Under inert gas protection, 100-1000 parts by weight of polyether base are dissolved in xylene solvent, 1-500 parts by weight of isocyanate-terminated quaternary ammonium salt polymer are added and reacted at 60-80 °C for 2-4 h. The solvent is then evaporated to obtain the high-efficiency heavy crude oil demulsifier as shown in formula (I).

[0018] Preferably, the solvent mentioned in step (1) is one or more of petroleum ether, chloroform and tetrahydrofuran.

[0019] Preferably, the formaldehyde solution mentioned in step (1) refers to an aqueous formaldehyde solution with a mass fraction concentration of 33%-36%.

[0020] Preferably, the catalyst mentioned in step (2) is one or more of potassium hydroxide, sodium methoxide and potassium carbonate.

[0021] Preferably, the reaction temperature in step (2) is controlled at 115-125 °C and the pressure is controlled at 0.21-0.35 MPa.

[0022] Preferably, the isocyanate-terminated quaternary ammonium salt polymer described in step (3) is first prepared by reacting N-methyldiethanolamine with 1-bromododecane to obtain dodecylbis(2-hydroxyethyl)methylammonium bromide, and then reacting dodecylbis(2-hydroxyethyl)methylammonium bromide with dicyclohexylmethane-4,4'-diisocyanate. The preparation reaction formula is as follows:

[0023] ;

[0024] Where m = 1 - 200.

[0025] Preferably, the isocyanate-terminated quaternary ammonium salt polymer described in step (3) includes the following specific steps:

[0026] (1) Take 1-100 parts by weight of 1-bromododecane and 1-50 parts by weight of N-methyldiethanolamine, dissolve them in ethanol, and stir and reflux at 80°C for 24 h; after the reaction is completed, recrystallize, purify and dry to obtain dodecyl bis(2-hydroxyethyl)methylammonium bromide;

[0027] (2) Take 1-100 parts by weight of dicyclohexylmethane-4,4'-diisocyanate and 1-100 parts by weight of dodecylbis(2-hydroxyethyl)methylammonium bromide and dissolve them in acetone. Then add 1-5 parts by weight of dibutyltin dilaurate and reflux the reaction under a nitrogen atmosphere until the characteristic absorption peak of the hydroxyl group disappears in the spectrum by infrared testing. Crystallize and purify the product and dry it to obtain isocyanate-terminated quaternary ammonium salt polymer.

[0028] Preferably, the inert gas mentioned in step (3) refers to one or a combination of argon and helium.

[0029] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0030] 1. In this invention, through chemical modification, quaternary ammonium salt polymers form covalent bonds with polyether bases to form cationic modified polyether as a new demulsifier molecular structure, thereby enhancing product stability and avoiding the problems of component stratification and poor compatibility that may occur when simply compounding. The modified demulsifier is more stable during storage, transportation and use, and the product performance is more consistent.

[0031] 2. The demulsifier provided by this invention has enhanced demulsification ability. After modification, the number of molecular chains increases, and the molecular weight significantly increases. Simultaneously, the quaternary ammonium salt polymer carries a positive charge and has high surface activity, exhibiting strong electrostatic interaction with the negatively charged components in the emulsion system. This enables more effective disruption of the emulsion film, improving demulsification performance. It requires less dosage, has a faster demulsification speed, higher dehydration rate, uniform interface, and good aqueous phase cleanliness. Furthermore, the demulsifier's adaptability is enhanced, exhibiting greater versatility.

[0032] 3. In this invention, the cyanate-terminated quaternary ammonium salt polymer can react with the terminal hydroxyl groups of the polyether base containing fluorine elements to generate urethane groups. After the reaction, the number of molecular chains increases and the molecular weight increases significantly. At the same time, a positive charge is introduced. Under the synergistic effect of electrostatic interaction, polymerization bridging, and high surface activity of fluorine, the demulsification performance is improved. In addition, isocyanate end-capping gives the demulsifier stronger chemical stability. The acid resistance, alkali resistance, and salt resistance of the demulsifier molecular chain are significantly improved. It still maintains its demulsification performance under high and low temperature, high salt, or extreme pH conditions. Detailed Implementation

[0033] The invention will be further described in detail below with reference to specific embodiments. These embodiments are intended to enable those skilled in the art to more fully understand the invention and are not to be construed as limiting the invention.

[0034] Example 1:

[0035] The following is a method for preparing a high-efficiency heavy crude oil demulsifier in this embodiment:

[0036] (1) Take 5 parts by weight of 3,5-difluorophenol and 33 parts by weight of tetraethylenepentamine, stir and mix, heat to 40 °C, then add 3 parts by weight of 36% formaldehyde aqueous solution, keep the temperature for 50 min after the addition is complete, add chloroform solvent, reflux to dehydrate for 2 h, evaporate the solvent, continue to react for 2 h to obtain the initiator.

[0037] (2) Take 50 parts by weight of the above-mentioned initiator and 20 parts by weight of sodium methoxide, and introduce them into 10,000 parts by weight of propylene oxide in a high-temperature and high-pressure reactor under argon protection. Control the reaction temperature at 120 °C and the pressure at 0.25 MPa. The reaction ends when the pressure in the reactor decreases to zero, and an intermediate is obtained. Take the obtained intermediate and 20 parts by weight of sodium methoxide, and introduce them into 5,000 parts by weight of ethylene oxide in a high-temperature and high-pressure reactor under argon protection. Control the temperature at 120 °C and the pressure at 0.25 MPa. The reaction ends when the pressure in the reactor decreases to zero, and a polyether base is obtained.

[0038] (3) Take 50 parts by weight of 1-bromododecane and 25 parts by weight of N-methyldiethanolamine, dissolve them in ethanol, and stir and reflux at 80 °C for 24 h. After the reaction is completed, recrystallize and purify the product and dry it to obtain dodecylbis(2-hydroxyethyl)methylammonium bromide.

[0039] (4) Take 52 parts by weight of dicyclohexylmethane-4,4'-diisocyanate and 36 parts by weight of dodecylbis(2-hydroxyethyl)methylammonium bromide and dissolve them in acetone. Then add 1 part by weight of dibutyltin dilaurate and reflux the reaction under a nitrogen atmosphere until the characteristic absorption peak of the hydroxyl group disappears in the spectrum by infrared testing. Crystallize and purify the product and dry it to obtain isocyanate-terminated quaternary ammonium salt polymer.

[0040] (5) Under inert gas protection, 500 parts by weight of polyether base were dissolved in xylene solvent, and 100 parts by weight of isocyanate-terminated quaternary ammonium salt polymer were added. The mixture was reacted at 60 °C for 2 h, and the solvent was evaporated to obtain a new type of heavy crude oil demulsifier.

[0041] Example 2:

[0042] The preparation method of a high-efficiency heavy crude oil demulsifier involved in this embodiment is as follows:

[0043] (1) Take 5 parts by weight of 3,5-difluorophenol and 33 parts by weight of tetraethylenepentamine, stir and mix, heat to 40 °C, then add 3 parts by weight of 36% formaldehyde aqueous solution, keep the temperature for 50 min after the addition is complete, add chloroform solvent, reflux to dehydrate for 2 h, evaporate the solvent, continue to react for 2 h to obtain the initiator.

[0044] (2) Take 50 parts by weight of the above-mentioned initiator and 10 parts by weight of potassium hydroxide, and introduce them into a high-temperature and high-pressure reactor under argon protection. Control the reaction temperature at 120 °C and the pressure at 0.25 MPa. The reaction ends when the pressure in the reactor decreases to zero, and an intermediate is obtained. Take the obtained intermediate and 10 parts by weight of potassium hydroxide, and introduce them into a high-temperature and high-pressure reactor under argon protection. Control the temperature at 120 °C and the pressure at 0.25 MPa. The reaction ends when the pressure in the reactor decreases to zero, and a polyether base is obtained.

[0045] (3) Take 50 parts by weight of 1-bromododecane and 25 parts by weight of N-methyldiethanolamine, dissolve them in ethanol, and stir and reflux at 80 °C for 24 h. After the reaction is completed, recrystallize and purify the product and dry it to obtain dodecylbis(2-hydroxyethyl)methylammonium bromide.

[0046] (4) Dissolve 70 parts by weight of dicyclohexylmethane-4,4'-diisocyanate and 50 parts by weight of dodecylbis(2-hydroxyethyl)methylammonium bromide in acetone, then add 1 part by weight of dibutyltin dilaurate and reflux under nitrogen atmosphere until the characteristic absorption peak of the hydroxyl group disappears in the spectrum by infrared testing. Crystallize and purify the product and dry it to obtain isocyanate-terminated quaternary ammonium salt polymer.

[0047] (5) Under inert gas protection, 500 parts by weight of polyether base were dissolved in xylene solvent, and 150 parts by weight of isocyanate-terminated quaternary ammonium salt polymer were added. The mixture was reacted at 60 °C for 2 h, and the solvent was evaporated to obtain a new type of heavy crude oil demulsifier.

[0048] Example 3:

[0049] The preparation method of a high-efficiency heavy crude oil demulsifier involved in this embodiment is as follows:

[0050] (1) Take 5 parts by weight of 3,5-difluorophenol and 33 parts by weight of tetraethylenepentamine, stir and mix, heat to 40 °C, then add 3 parts by weight of 36% formaldehyde aqueous solution, keep the temperature for 50 min after the addition is complete, add chloroform solvent, reflux to dehydrate for 2 h, evaporate the solvent, continue to react for 2 h to obtain the initiator.

[0051] (2) Take 50 parts by weight of the above-mentioned initiator and 15 parts by weight of potassium hydroxide, and introduce them into 8000 parts by weight of propylene oxide in a high-temperature and high-pressure reactor under argon protection. Control the reaction temperature at 120 ℃ and the pressure at 0.25 MPa. The reaction ends when the pressure in the reactor decreases to zero, and an intermediate is obtained. Take the obtained intermediate and 15 parts by weight of potassium hydroxide, and introduce them into 5000 parts by weight of ethylene oxide in a high-temperature and high-pressure reactor under argon protection. Control the temperature at 120 ℃ and the pressure at 0.25 MPa. The reaction ends when the pressure in the reactor decreases to zero, and a polyether base is obtained.

[0052] (3) Take 50 parts by weight of 1-bromododecane and 25 parts by weight of N-methyldiethanolamine, dissolve them in ethanol, and stir and reflux at 80 °C for 24 h. After the reaction is completed, recrystallize and purify the product and dry it to obtain dodecylbis(2-hydroxyethyl)methylammonium bromide.

[0053] (4) Take 90 parts by weight of dicyclohexylmethane-4,4'-diisocyanate and 60 parts by weight of dodecylbis(2-hydroxyethyl)methylammonium bromide and dissolve them in acetone. Then add 1 part by weight of dibutyltin dilaurate and reflux the reaction under a nitrogen atmosphere until the characteristic absorption peak of the hydroxyl group disappears in the spectrum by infrared testing. Crystallize and purify the product and dry it to obtain isocyanate-terminated quaternary ammonium salt polymer.

[0054] (5) Under inert gas protection, 500 parts by weight of polyether base were dissolved in xylene solvent, and 200 parts by weight of isocyanate-terminated quaternary ammonium salt polymer were added. The mixture was reacted at 60 °C for 4 h, and the solvent was evaporated to obtain a new type of heavy crude oil demulsifier.

[0055] Comparative Example 1:

[0056] The preparation method of a polyether crude oil demulsifier involved in this comparative example is as follows:

[0057] (1) Take 5 parts by weight of 3,5-difluorophenol and 33 parts by weight of tetraethylenepentamine, stir and mix, heat to 40 °C, then add 3 parts by weight of 36% formaldehyde aqueous solution, keep the temperature for 50 min after the addition is complete, add chloroform solvent, reflux to dehydrate for 2 h, evaporate the solvent, continue to react for 2 h to obtain the initiator.

[0058] (2) Take 50 parts by weight of the above-mentioned initiator and 20 parts by weight of sodium methoxide, and introduce them into 10,000 parts by weight of propylene oxide in a high-temperature and high-pressure reactor under argon protection. Control the reaction temperature at 120 °C and the pressure at 0.25 MPa. The reaction ends when the pressure in the reactor decreases to zero, and an intermediate is obtained. Take the obtained intermediate and 20 parts by weight of sodium methoxide, and introduce them into 5,000 parts by weight of ethylene oxide in a high-temperature and high-pressure reactor under argon protection. Control the temperature at 120 °C and the pressure at 0.25 MPa. The reaction ends when the pressure in the reactor decreases to zero, and a polyether base is obtained, which is the demulsifier prepared in this comparative example.

[0059] Comparative Example 2:

[0060] The traditional commercial polyether crude oil demulsifier SP169 was used as a comparison.

[0061] Comparative Example 3:

[0062] The commercially available OFC-609 ionic demulsifier was used as a comparison.

[0063] Performance test and evaluation results:

[0064] Using simulated heavy crude oil emulsions as the treatment object, the demulsifier performance of the products provided in Examples 1-3 and Comparative Examples 1-3 was evaluated using the bottle test method. The simulated crude oil emulsions were prepared as follows: Heavy crude oil from a certain oilfield was taken, and free water and emulsion were separated. The emulsion contained about 20% water. A certain ratio of free water and emulsion was transferred into a stoppered graduated cylinder, with the total volume controlled at 80 mL and the overall water content controlled at 90%. The mixture was shaken 100 times and then kept at constant temperature and static temperature at pH 4.5, 6.0, and 7.5; salinity of 500 mg / L, 1000 mg / L, and 2000 mg / L; and temperature of 60 ℃, 80 ℃, and 100 ℃. The amount of water dehydrated, the color of the dehydrated water, the interface condition, and the adhesion to the wall were examined in each stoppered graduated cylinder at different times.

[0065] 1. Under conditions of pH 6, salinity 1000 mg / L, and temperature 80 ℃, the demulsifier performance evaluation data of the demulsifier products provided in each example and comparative example are shown in Table 1 below.

[0066] Table 1: Demulsification performance results of the demulsifier products provided in Examples 1-3 and Comparative Examples 1-3

[0067]

[0068] As shown in Table 1, the demulsifier provided by this invention, when used in the same dosage, exhibits faster demulsification speed, higher dehydration rate, uniform interface, and better aqueous phase cleanliness compared to the traditional commercial polyether crude oil demulsifier SP169 in Comparative Example 2 and the commercial OFC-609 ionic demulsifier in Comparative Example 3. At a dosage of 80 mg / L, the final dehydration rate can reach 95% after 24 hours. Compared to Comparative Example 1, the reaction between the polyether base in Examples 1 to 3 and the cyanate-terminated quaternary ammonium salt polymer results in an increased number of molecular chains and a significantly increased molecular weight. Simultaneously, the introduction of a positive charge enhances the demulsification performance through the synergistic effects of electrostatic interaction, polymerization bridging, and high surface activity.

[0069] 2. The effects of different pH values, salinities, and temperatures on the demulsifying performance of the demulsifier products provided in each example and comparative example are shown in Table 2 below, when the dosage is 80 mg / L.

[0070] Table 2: Demulsification performance results of the demulsifier products provided in Example 3 and Comparative Examples 1-3 under different conditions.

[0071]

[0072] As shown in Table 2, the demulsifier provided in Example 3, when used in the same dosage, exhibits faster demulsification speed, higher dehydration rate, smoother interface, and better aqueous phase cleanliness compared to the traditional commercial polyether crude oil demulsifier SP169 in Comparative Example 2 and the commercial OFC-609 ionic demulsifier in Comparative Example 3. Furthermore, the demulsifier in Example 3 maintains a final dehydration rate of 95% after 24 hours under acidic, alkaline, high-salt, and high / low temperature conditions, demonstrating stable demulsification performance under high / low temperature, high-salt, or extreme pH conditions. The demulsifier provided in Example 3, at a dosage of 80 mg / L, a temperature of 100 ℃, a pH of 7.5, and a salinity of 2000 mg / L, achieves a final dehydration rate of 98.6% after 24 hours. Compared with Comparative Example 1, the polyether bases in Examples 1 to 3 react with cyanate-terminated quaternary ammonium salt polymers, resulting in an increase in the number of molecular chains and a significant increase in molecular weight after the reaction. At the same time, positive charges are introduced, which improves the demulsification performance under the synergistic effect of electrostatic interaction, polymerization bridging, and high surface activity.

[0073] All features described in the specification and appended claims, whether individually or in any combination thereof, are essential features of this invention.

[0074] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, alterations, deletions of some features, additions of features, or recombinations of features to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the innovative principles of the present invention shall still fall within the scope of the technical solutions of the present invention.

Claims

1. A high-efficiency heavy crude oil demulsifier, characterized in that, The structure is shown in equation (I) below: (Formula I); Where m = 1 - 200, R is x = 1 - 600, y = 1 - 600.

2. A method for preparing the high-efficiency heavy crude oil demulsifier as described in claim 1, characterized in that, An initiator was obtained by reacting 3,5-difluorophenol with tetraethylenepentamine and formaldehyde solution. The initiator, propylene oxide and ethylene oxide were subjected to block polymerization under the action of a catalyst to obtain a polyether base. The polyether base was reacted with isocyanate-terminated quaternary ammonium salt polymers to obtain a high-efficiency heavy crude oil demulsifier as shown in formula (I).

3. The method for preparing a high-efficiency heavy crude oil demulsifier according to claim 2, characterized in that, Includes the following steps: (1) Take 1-10 parts by weight of 3,5-difluorophenol and 5-50 parts by weight of tetraethylenepentamine, stir and mix, heat to 40°C, then add 1-10 parts by weight of formaldehyde solution, keep the temperature for 50 min after the addition is complete, add solvent, reflux to dehydrate for 2 h, evaporate the solvent, continue to react for 2 h to obtain the initiator; (2) Take 10-100 parts by weight of the above-mentioned initiator and 0-50 parts by weight of the catalyst and introduce 10-50000 parts by weight of propylene oxide into a high-temperature and high-pressure reactor under inert gas protection. Control the reaction temperature and pressure. When the pressure in the reactor decreases to zero, the reaction ends and an intermediate is obtained. Take the obtained intermediate and 0-50 parts by weight of the catalyst and introduce 100-80000 parts by weight of ethylene oxide into a high-temperature and high-pressure reactor under inert gas protection. Control the reaction temperature and pressure. When the pressure in the reactor decreases to zero, the reaction ends and a polyether base is obtained. (3) Under inert gas protection, 100-1000 parts by weight of polyether base are dissolved in xylene solvent, 1-500 parts by weight of isocyanate-terminated quaternary ammonium salt polymer are added and reacted at 60-80 °C for 2-4 h. The solvent is then evaporated to obtain the high-efficiency heavy crude oil demulsifier as shown in formula (I).

4. The method for preparing a high-efficiency heavy crude oil demulsifier according to claim 3, characterized in that, The solvent mentioned in step (1) refers to one or more of petroleum ether, chloroform and tetrahydrofuran.

5. The method for preparing a high-efficiency heavy crude oil demulsifier according to claim 3, characterized in that, The formaldehyde solution mentioned in step (1) refers to an aqueous formaldehyde solution with a mass fraction concentration of 33%-36%.

6. The method for preparing a high-efficiency heavy crude oil demulsifier according to claim 3, characterized in that, The catalyst mentioned in step (2) refers to one or more of potassium hydroxide, sodium methoxide, and potassium carbonate.

7. The method for preparing a high-efficiency heavy crude oil demulsifier according to claim 3, characterized in that, The reaction temperature in step (2) is controlled at 115-125 ℃ and the pressure is controlled at 0.21-0.35 MPa.

8. The method for preparing a high-efficiency heavy crude oil demulsifier according to claim 3, characterized in that, The isocyanate-terminated quaternary ammonium salt polymer described in step (3) is obtained by first reacting N-methyldiethanolamine with 1-bromododecane to obtain dodecylbis(2-hydroxyethyl)methylammonium bromide, and then reacting dodecylbis(2-hydroxyethyl)methylammonium bromide with dicyclohexylmethane-4,4'-diisocyanate.

9. The method for preparing a high-efficiency heavy crude oil demulsifier according to claim 8, characterized in that, The isocyanate-terminated quaternary ammonium salt polymer described in step (3) includes the following specific steps: (1) Take 1-100 parts by weight of 1-bromododecane and 1-50 parts by weight of N-methyldiethanolamine, dissolve them in ethanol, and stir and reflux at 80 °C for 24 h; after the reaction is completed, recrystallize and purify and dry to obtain dodecyl bis(2-hydroxyethyl)methylammonium bromide; (2) Take 1-100 parts by weight of dicyclohexylmethane-4,4'-diisocyanate and 1-100 parts by weight of dodecylbis(2-hydroxyethyl)methylammonium bromide and dissolve them in acetone. Then add 1-5 parts by weight of dibutyltin dilaurate and reflux the reaction under a nitrogen atmosphere until the characteristic absorption peak of the hydroxyl group disappears in the spectrum by infrared testing. Crystallize and purify the product and dry it to obtain isocyanate-terminated quaternary ammonium salt polymer.

10. The method for preparing a high-efficiency heavy crude oil demulsifier according to claim 3, characterized in that, The inert gas mentioned in step (3) refers to one or a combination of argon and helium.

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