Efficient heavy crude oil demulsifier and preparation method thereof

Abstract

The invention discloses an efficient heavy crude oil demulsifier and a preparation method thereof, the structural formula of the efficient heavy crude oil demulsifier is as shown in formula (I) # imgabs0 #, m = 1-200, R is # imgabs1 #, x = 1-600, and y = 1-600. According to the high-efficiency heavy crude oil demulsifier provided by the technical scheme, through chemical modification, the quaternary ammonium salt polymer and the polyether base material form a covalent bond, and cation modified polyether is formed as a new demulsifier molecular structure, so that the product stability is enhanced, the problems of component layering and poor compatibility possibly occurring during simple compounding are avoided, and the demulsifier is suitable for large-scale production. The modified demulsifier is more stable in the storage, transportation and use processes, the product performance is more consistent, and the high-efficiency heavy crude oil demulsifier has the advantages of good demulsification performance, small dosage, high demulsification speed, high dehydration rate, uniform interface and good water phase cleanliness.

Description

Technical Field

[0001] The invention relates to the technical field of heavy crude oil demulsifiers, and in particular to a high-efficiency heavy crude oil demulsifier and a preparation method thereof. Background Art

[0002] As a non-renewable resource, petroleum occupies an irreplaceable strategic position in national security such as national defense and aerospace, industry, agriculture and daily life. A large amount of water needs to be injected into the formation during crude oil extraction. In particular, the promotion and application of tertiary oil recovery technologies such as polymer flooding, surfactant flooding and multi-component composite flooding make it easy for oilfield produced fluid to form stable water-in-oil, oil-in-water emulsions and composite water-in-oil emulsions. The presence of emulsions will lead to a series of problems such as increased crude oil transportation costs, equipment and pipeline corrosion, and waste of oil resources. Therefore, oil-water separation of oilfield produced emulsions is the key 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] At present, the common demulsification methods mainly include adding chemical demulsifiers, physical demulsification and biological demulsification. Among them, chemical demulsifiers are widely used in oil-water separation due to their advantages of simple operation, fast demulsification speed and relatively low demulsification cost. However, heavy crude oil contains a high proportion of colloids and asphaltene, and has the characteristics of high density and high viscosity. The existing technology for heavy crude oil still has problems such as large amount of demulsifiers, high treatment cost, slow demulsification speed, long treatment cycle, and high oil content in the demulsified water.

[0004] Patent application with publication number CN107057754A discloses a demulsifier suitable for heavy crude oil emulsion with high water content, in which cationic polymer is added to promote oil phase coagulation and flocculation, thereby accelerating the oil-water separation rate. However, this demulsifier is prone to component stratification and poor compatibility when used, and is prone to deterioration during storage, transportation and use, resulting in unstable product performance.

[0005] Therefore, it is of great practical significance to develop a new type of heavy crude oil demulsifier that is efficient, economical and environmentally friendly. Summary of the invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a heavy crude oil demulsifier with stable and efficient performance and a preparation method thereof, so as to achieve rapid and efficient demulsification, reduce processing costs and improve crude oil quality.

[0007] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

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

[0009]

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

[0011] A method for preparing the above-mentioned high-efficiency heavy crude oil demulsifier comprises the following steps: 3,5-difluorophenol is reacted with tetraethylenepentamine and formaldehyde solution to obtain a new initiator; the new initiator, propylene oxide and ethylene oxide are subjected to block polymerization reaction under the action of a catalyst to obtain a polyether base; the polyether base is reacted with an isocyanate-terminated quaternary ammonium salt polymer to obtain a high-efficiency heavy crude oil demulsifier as shown in formula (I), and the reaction formula is as follows:

[0012]

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

[0014] As a preference, the method comprises the following steps:

[0015] (1) 1-10 parts by weight of 3,5-difluorophenol and 5-50 parts by weight of tetraethylenepentamine are stirred and mixed, heated to 40° C., and then 1-10 parts by weight of formaldehyde solution are added dropwise. After the addition is completed, the mixture is kept warm for 50 minutes, an α solvent is added, and the mixture is refluxed for dehydration for 2 hours. The solvent is evaporated and the reaction is continued for 2 hours to obtain a new initiator;

[0016] (2) taking 10-100 parts by weight of the novel initiator and 0-50 parts by weight of the catalyst and introducing 10-50000 parts by weight of propylene oxide to react in a high-temperature and high-pressure reactor protected by inert gas, controlling the reaction temperature and pressure, and waiting for the pressure in the reactor to decrease to zero to complete the reaction, thereby obtaining an intermediate; introducing 100-80000 parts by weight of ethylene oxide into the obtained intermediate and 0-50 parts by weight of the catalyst, and reacting in a high-temperature and high-pressure reactor protected by inert gas, controlling the reaction temperature and pressure, and waiting for the pressure in the reactor to decrease to zero to complete the reaction, thereby obtaining a polyether base;

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

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

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

[0020] Preferably, the catalyst 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 obtained by reacting N-methyldiethanolamine with 1-bromodecane 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] Among them, m=1-200.

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

[0026] (1) dissolving 1-100 parts by weight of dodecane bromide and 1-50 parts by weight of N-methyldiethanolamine in ethanol, stirring and refluxing at 80° C. for 24 hours; after the reaction is completed, recrystallizing, purifying and drying to obtain dodecylmethyldihydroxyethylammonium bromide;

[0027] (2) 1-100 parts by weight of dicyclohexylmethane-4,4'-diisocyanate and 1-100 parts by weight of dodecylmethyl dihydroxyethyl ammonium bromide are dissolved in acetone, and then 1-5 parts by weight of dibutyltin dilaurate are added and refluxed under a nitrogen atmosphere until the characteristic absorption peak of the hydroxyl group disappears in the spectrum as observed by infrared testing, and the product is crystallized, purified and dried to obtain an isocyanate-terminated quaternary ammonium salt polymer.

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

[0029] The present invention has the following beneficial effects due to the adoption of the above technical solution:

[0030] 1. In the present invention, by chemical modification, the quaternary ammonium salt polymer forms a covalent bond with the polyether base to form a cationic modified polyether as a new demulsifier molecular structure, thereby enhancing the product stability and avoiding the problems of component stratification and poor compatibility that may occur during simple 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 the present invention has enhanced demulsification ability, increased molecular chains after modification, and significantly increased molecular weight. At the same time, the quaternary ammonium salt polymer has a positive charge, high surface activity, and has a strong electrostatic effect with the negatively charged components in the emulsification system, which can more effectively destroy the emulsion film and improve the demulsification performance. It has a small amount of use, a fast demulsification speed, a high dehydration rate, a uniform interface, and good water phase cleanliness. The demulsifier has enhanced adaptability and stronger versatility;

[0032] 3. In the present invention, the quaternary ammonium salt polymer terminated with cyanate can react with the terminal hydroxyl group of the polyether base having fluorine element in the present invention to generate carbamate group. After the reaction, the number of molecular chains increases, the molecular weight increases significantly, and positive charge is introduced at the same time. Under the synergistic effect of electrostatic action, polymer bridging, and high fluorine-containing surface activity, the demulsification performance is improved; in addition, the isocyanate end-capping gives the demulsifier stronger chemical stability, and the acid, alkali and salt resistance of the demulsifier molecular chain are significantly improved, and the demulsification performance is still maintained under high and low temperature, high salt or extreme pH conditions. DETAILED DESCRIPTION

[0033] The invention is further described in detail below in conjunction with specific examples. The examples can enable professionals in this field to more fully understand the invention, and are intended to be used to explain the invention, but should not be understood as limiting the invention.

[0034] Embodiment 1:

[0035] The preparation method of a high-efficiency heavy crude oil demulsifier involved in this embodiment is as follows:

[0036] (1) 5 parts by weight of 3,5-difluorophenol and 33 parts by weight of tetraethylenepentamine were stirred and mixed, heated to 40° C., and then 3 parts by weight of a 36% formaldehyde aqueous solution were added dropwise. After the addition was completed, the mixture was kept warm for 50 minutes, chloroform solvent was added, refluxed for dehydration for 2 hours, the solvent was evaporated, and the reaction was continued for 2 hours to obtain an initiator.

[0037] (2) Take 50 parts by weight of the above-mentioned initiator, 20 parts by weight of sodium methoxide and introduce 10,000 parts by weight of propylene oxide to react in a high-temperature and high-pressure reactor protected by argon, control the reaction temperature to 120°C and the pressure to 0.25 MPa, wait until the pressure in the reactor is reduced to zero and the reaction is completed to obtain an intermediate. The obtained intermediate and 20 parts by weight of sodium methoxide are introduced into 5,000 parts by weight of ethylene oxide to react in a high-temperature and high-pressure reactor protected by argon, control the temperature to 120°C and the pressure to 0.25 MPa, wait until the pressure in the reactor is reduced to zero and the reaction is completed to obtain a polyether base.

[0038] (3) 50 parts by weight of dodecane bromide and 25 parts by weight of N-methyldiethanolamine were dissolved in ethanol, and stirred and refluxed at 80° C. for 24 hours. After the reaction, dodecylmethyldihydroxyethylammonium bromide was obtained by recrystallization, purification and drying.

[0039] (4) 52 parts by weight of dicyclohexylmethane-4,4'-diisocyanate and 36 parts by weight of dodecylmethyldihydroxyethylammonium bromide were dissolved in acetone, and then 1 part by weight of dibutyltin dilaurate was added and refluxed under a nitrogen atmosphere until the characteristic absorption peak of the hydroxyl group disappeared in the spectrum as observed by infrared testing. The product was crystallized, purified and dried to obtain an isocyanate-terminated quaternary ammonium salt polymer.

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

[0041] Embodiment 2:

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

[0043] (1) 5 parts by weight of 3,5-difluorophenol and 33 parts by weight of tetraethylenepentamine were stirred and mixed, heated to 40° C., and then 3 parts by weight of a 36% formaldehyde aqueous solution were added dropwise. After the addition was completed, the mixture was kept warm for 50 minutes, chloroform solvent was added, refluxed for dehydration for 2 hours, the solvent was evaporated, and the reaction was continued for 2 hours to obtain an initiator.

[0044] (2) Take 50 parts by weight of the above-mentioned initiator, 10 parts by weight of potassium hydroxide and introduce 5000 parts by weight of propylene oxide to react in a high-temperature and high-pressure reactor protected by argon, control the reaction temperature to 120°C and the pressure to 0.25 MPa, wait until the pressure in the reactor is reduced to zero and the reaction is completed to obtain an intermediate. The obtained intermediate and 10 parts by weight of potassium hydroxide, and introduce 5000 parts by weight of ethylene oxide to react in a high-temperature and high-pressure reactor protected by argon, control the temperature to 120°C and the pressure to 0.25 MPa, wait until the pressure in the reactor is reduced to zero and the reaction is completed to obtain a polyether base.

[0045] (3) 50 parts by weight of dodecane bromide and 25 parts by weight of N-methyldiethanolamine were dissolved in ethanol, and stirred and refluxed at 80° C. for 24 hours. After the reaction, dodecylmethyldihydroxyethylammonium bromide was obtained by recrystallization, purification and drying.

[0046] (4) 70 parts by weight of dicyclohexylmethane-4,4'-diisocyanate and 50 parts by weight of dodecylmethyldihydroxyethylammonium bromide were dissolved in acetone, and then 1 part by weight of dibutyltin dilaurate was added and refluxed under a nitrogen atmosphere until the characteristic absorption peak of the hydroxyl group disappeared in the spectrum as observed by infrared testing. The product was crystallized, purified and dried to obtain an isocyanate-terminated quaternary ammonium salt polymer.

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

[0048] Embodiment 3:

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

[0050] (1) 5 parts by weight of 3,5-difluorophenol and 33 parts by weight of tetraethylenepentamine were stirred and mixed, heated to 40° C., and then 3 parts by weight of a 36% formaldehyde aqueous solution were added dropwise. After the addition was completed, the mixture was kept warm for 50 minutes, chloroform solvent was added, refluxed for dehydration for 2 hours, the solvent was evaporated, and the reaction was continued for 2 hours to obtain an initiator.

[0051] (2) Take the above 50 parts by weight of the initiator, 15 parts by weight of potassium hydroxide and introduce 8000 parts by weight of propylene oxide to react in a high-temperature and high-pressure reactor protected by argon, control the reaction temperature to 120°C and the pressure to 0.25 MPa, wait until the pressure in the reactor is reduced to zero and the reaction is completed to obtain an intermediate. The obtained intermediate and 15 parts by weight of potassium hydroxide are introduced into 5000 parts by weight of ethylene oxide to react in a high-temperature and high-pressure reactor protected by argon, control the temperature to 120°C and the pressure to 0.25 MPa, wait until the pressure in the reactor is reduced to zero and the reaction is completed to obtain a polyether base.

[0052] (3) 50 parts by weight of dodecane bromide and 25 parts by weight of N-methyldiethanolamine were dissolved in ethanol, and stirred and refluxed at 80° C. for 24 hours. After the reaction, dodecylmethyldihydroxyethylammonium bromide was obtained by recrystallization, purification and drying.

[0053] (4) 90 parts by weight of dicyclohexylmethane-4,4'-diisocyanate and 60 parts by weight of dodecylmethyldihydroxyethylammonium bromide were dissolved in acetone, and then 1 part by weight of dibutyltin dilaurate was added and refluxed under a nitrogen atmosphere until the characteristic absorption peak of the hydroxyl group disappeared in the spectrum as observed by infrared testing. The product was crystallized, purified and dried to obtain an isocyanate-terminated quaternary ammonium salt polymer.

[0054] (5) Under the protection of inert gas, 500 parts by weight of the polyether base was dissolved in xylene solvent, 200 parts by weight of isocyanate-terminated quaternary ammonium salt polymer was added, and the mixture was reacted at 60° C. for 4 h, and the solvent was evaporated to obtain a novel 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) 5 parts by weight of 3,5-difluorophenol and 33 parts by weight of tetraethylenepentamine were stirred and mixed, heated to 40° C., and then 3 parts by weight of a 36% formaldehyde aqueous solution were added dropwise. After the addition was completed, the mixture was kept warm for 50 minutes, chloroform solvent was added, refluxed for dehydration for 2 hours, the solvent was evaporated, and the reaction was continued for 2 hours to obtain an initiator.

[0058] (2) Take the above 50 parts by weight of the initiator, 20 parts by weight of sodium methoxide and introduce 10,000 parts by weight of propylene oxide to react in a high-temperature and high-pressure reactor protected by argon, control the reaction temperature to 120°C and the pressure to 0.25 MPa, wait for the pressure in the reactor to decrease to zero and the reaction is completed to obtain an intermediate. The obtained intermediate and 20 parts by weight of sodium methoxide, and introduce 5,000 parts by weight of ethylene oxide to react in a high-temperature and high-pressure reactor protected by argon, control the temperature to 120°C and the pressure to 0.25 MPa, wait for the pressure in the reactor to decrease to zero and the reaction is completed to obtain a polyether base, 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 commercial OFC-609 ionic demulsifier was used as a comparison.

[0063] Performance test and evaluation results:

[0064] The simulated heavy crude oil emulsion was used as the treatment object, and the demulsification performance of the demulsifier products provided in Examples 1 to 3 and Comparative Examples 1 to 3 was evaluated by the bottle test method, wherein the simulated crude oil emulsion was prepared as follows: heavy crude oil from a certain oil field was taken, free water and emulsion were separated, and the emulsion contained about 20% water; a certain ratio of free water and emulsion was transferred into a stoppered measuring cylinder, the total volume was controlled to 80 mL, the comprehensive water content was controlled to 90%, and oscillated 100 times, respectively at pH 4.5, 6.0, and 7.5; the salinity was 500 mg / L, 1000 mg / L, and 2000 mg / L; the temperature was 60°C, 80°C, and 100°C, and the dehydration amount, the color of the desorbed water, the interface condition, and the wall adhesion condition in each stoppered measuring cylinder at different times were examined.

[0065] 1. When the pH value is 6, the salinity is 1000 mg / L and the temperature is 80° C., the demulsifier products provided in the embodiments and comparative examples are evaluated for their demulsification performance. The data are shown in Table 1 below.

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

[0067]

[0068]

[0069] According to Table 1, the demulsifier provided by the present invention has the characteristics of fast demulsification speed, high dehydration rate, uniform interface and good water phase cleanliness compared with the traditional commercial polyether crude oil demulsifier SP169 in Comparative Example 2 and the commercial OFC-609 ion demulsifier in Comparative Example 3 when the dosage is the same. When the dosage is 80 mg / L, the final dehydration rate in 24 hours can reach 95%. Compared with Comparative Example 1, since the polyether base in Examples 1 to 3 reacts with the quaternary ammonium salt polymer terminated with cyanate, the number of molecular chains after the reaction increases, the molecular weight increases significantly, and positive charges are introduced at the same time, and the demulsification performance is improved under the synergistic effect of electrostatic action, polymer bridging and high surface activity.

[0070] 2. When the dosage is 80 mg / L, the effects of different pH, different salinity and different temperature on the demulsification performance of the demulsifier products provided in each embodiment and comparative example are shown in Table 2 below.

[0071] Table 2: Demulsification performance results of demulsifier products provided by Example 3 and Comparative Examples 1-3 under different conditions

[0072]

[0073] As shown in Table 2, the demulsifier provided in Example 3 has the characteristics of fast demulsification speed, high dehydration rate, neat interface and good water phase cleanliness compared with the traditional commercial polyether crude oil demulsifier SP169 in Comparative Example 2 and the commercial OFC-609 ion demulsifier in Comparative Example 3 when the dosage is the same. Moreover, the demulsifier in Example 3 always maintains a final dehydration rate of 95% in 24 hours under acidic, alkaline, high salt and high and low temperature conditions, and the demulsification performance is stable under high and low temperature, high salt or extreme pH conditions. The demulsifier provided in Example 3 can reach a final dehydration rate of 98.6% in 24 hours when the dosage is 80 mg / L, the temperature is 100°C, the pH is 7.5, and the salinity is 2000 mg / L. Compared with Comparative Example 1, since the polyether base in Examples 1 to 3 reacts with the quaternary ammonium salt polymer terminated with cyanate, the number of molecular chains increases after the reaction, the molecular weight increases significantly, and positive charges are introduced at the same time. Under the synergistic effects of electrostatic action, polymer bridging, and high surface activity, the demulsification performance is improved.

[0074] All features described in the description and the appended claims are essential features of the invention both individually and in any combination.

[0075] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Ordinary technicians in the field can change, modify, replace, modify, delete some features, add features or re-combine features to form a technical solution in the above embodiments without departing from the principles and purpose of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the innovative principles of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A high-efficiency heavy crude oil demulsifier, characterized in that: The structure is shown in the following formula (I): Wherein, m = 1-200, R is x=1-600, y=1-600.

2. A method for preparing a high-efficiency heavy crude oil demulsifier as claimed in claim 1, characterized in that: A novel initiator is obtained by reacting 3,5-difluorophenol with tetraethylenepentamine and formaldehyde solution. The novel initiator, propylene oxide and ethylene oxide are subjected to block polymerization reaction under the action of a catalyst to obtain a polyether base. The polyether base is reacted with an isocyanate-terminated quaternary ammonium salt polymer 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: The following steps are involved: (1) 1-10 parts by weight of 3,5-difluorophenol and 5-50 parts by weight of tetraethylenepentamine are stirred and mixed, heated to 40° C., and then 1-10 parts by weight of formaldehyde solution are added dropwise. After the addition is completed, the mixture is kept warm for 50 minutes, an α solvent is added, and the mixture is refluxed for dehydration for 2 hours. The solvent is evaporated and the reaction is continued for 2 hours to obtain a new initiator; (2) taking 10-100 parts by weight of the novel initiator and 0-50 parts by weight of the catalyst and introducing 10-50000 parts by weight of propylene oxide to react in a high-temperature and high-pressure reactor protected by inert gas, controlling the reaction temperature and pressure, and waiting for the pressure in the reactor to decrease to zero to complete the reaction, thereby obtaining an intermediate; introducing 100-80000 parts by weight of ethylene oxide into the obtained intermediate and 0-50 parts by weight of the catalyst, and reacting in a high-temperature and high-pressure reactor protected by inert gas, controlling the reaction temperature and pressure, and waiting for the pressure in the reactor to decrease to zero to complete the reaction, thereby obtaining a polyether base; (3) Under the protection of inert gas, 100-1000 parts by weight of the polyether base is dissolved in xylene solvent, 1-500 parts by weight of isocyanate-terminated quaternary ammonium salt polymer is added, and the mixture is reacted at 60-80° C. for 2-4 hours, and the solvent is evaporated to obtain a 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 α solvent in step (1) is 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 described in step (1) refers to: a formaldehyde aqueous 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 in step (2) is 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° C., 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 first obtained by reacting N-methyldiethanolamine with 1-bromodecane 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) comprises the following specific steps: (1) dissolving 1-100 parts by weight of dodecane bromide and 1-50 parts by weight of N-methyldiethanolamine in ethanol, stirring and refluxing at 80° C. for 24 hours; after the reaction is completed, recrystallizing, purifying and drying to obtain dodecylmethyldihydroxyethylammonium bromide; (2) 1-100 parts by weight of dicyclohexylmethane-4,4'-diisocyanate and 1-100 parts by weight of dodecylmethyl dihydroxyethyl ammonium bromide are dissolved in acetone, and then 1-5 parts by weight of dibutyltin dilaurate are added and refluxed under a nitrogen atmosphere until the characteristic absorption peak of the hydroxyl group disappears in the spectrum as observed by infrared testing, and the product is crystallized, purified and dried to obtain an 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 described in step (3) refers to: one or a combination of argon and helium.

Images