Low-temperature crude oil demulsifier and preparation method thereof

Abstract

The invention relates to a preparation method of a low-temperature crude oil demulsifier, which comprises the following specific steps: preparing block polyether by using propane diamine as an initiator and using epoxypropane and ethylene oxide as main agents, then grafting by using an organic silicon chain, and modifying by using isocyanate. The invention also relates to a low-temperature crude oil demulsifier. Compared with the prior art, the invention has the following beneficial effects: according to the technical scheme, isocyanate is used for modifying the whole block polyether molecular chain, the demulsification effect of the demulsifier can be obviously improved, and meanwhile, after organic silicon and isocyanate are used for modification, the application temperature of the demulsifier is positively influenced; the low-temperature crude oil demulsifier prepared by adopting the preparation method disclosed by the invention is high in demulsification speed and good in demulsification effect under a normal-temperature condition and can be applied to scenes with high temperature rise difficulty, high demulsification speed requirement and high demulsification performance requirement, and the adopted raw materials are low in price, simple in synthesis method and convenient for large-scale popularization.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development aids, and particularly relates to a low-temperature crude oil demulsifier and a preparation method thereof. Background Art

[0002] For current oil fields, most of them have entered the late stage of exploitation, and the water content of the produced fluid is high. For viscous oil and the produced fluid with a large amount of oil displacement agents, there is a strong emulsification phenomenon. Therefore, after the crude oil is produced, it is necessary to demulsify it to separate oil and water. Currently, for crude oil demulsification, it mainly includes sedimentation method, heating method, electro-dehydration and chemical demulsification. Among them, chemical demulsification is to add a corresponding demulsifier to the oil-water emulsion to change the interfacial properties of the emulsion, so that the stability of the emulsion system is greatly reduced, thereby achieving the purpose of demulsification. The block polyether graft-modified demulsifier is a commonly used demulsifier at present. It uses an initiator, ethylene oxide (EO), and propylene oxide (PO) to synthesize the corresponding demulsifier. In some cases, corresponding graft monomers are also designed for modification to increase the demulsification effect of the whole demulsifier. However, for the current block polyether demulsifier, most of them need to have a certain demulsification effect above 50 °C, and the demulsification effect can reach the expected value above 60 °C, with poor applicability. Even if there are some demulsifiers used at room temperature, their demulsification effect is relatively poor. At the same time, the demulsification time is long, and it usually takes at least 30 minutes to make the demulsification effect reach the expected value.

[0003] To solve one of the above problems, it is necessary to produce a low-temperature crude oil demulsifier to solve the problems of long demulsification time and poor demulsification effect in the prior art. Summary of the Invention

[0004] According to the above deficiencies in the prior art, the technical problem to be solved by the present invention is: to provide a low-temperature crude oil demulsifier and a preparation method thereof to adapt to a lower temperature environment, shorten the demulsification time, so as to achieve the purpose of enhancing the demulsification effect.

[0005] One of the technical solutions adopted by the present invention to solve the above technical problems is:

[0006] A preparation method of a low-temperature crude oil demulsifier includes the following steps: using propanediamine as an initiator, using propylene oxide and ethylene oxide as main agents to prepare a block polyether, then grafting with an organosilicon chain, and then modifying with isocyanate. The mass ratio of the initiator, propylene oxide, ethylene oxide, and organosilicon chain is 10:(50-100):(25-40):(5-20).

[0007] Preferably, the mass ratio of the initiator to the isocyanate monomer is 10:(1-3).

[0008] Preferably, the mass ratio of the initiator, propylene oxide, ethylene oxide, and silicone chain is 10:(65 - 75):(25 - 30):(5 - 20).

[0009] Preferably, for the silicone chain, those with a molecular weight greater than 1000 can be applied to the present invention, but low molecular weight hydrogen-containing silicone oil with a molecular weight greater than 2000 is preferred, which can effectively increase the molecular size of the entire demulsifier and make its demulsification effect better.

[0010] For the design of the molecular structure of the entire demulsifier, the structure of "initiator - PO - EO - terminator" can be adopted, the structure of "initiator - PO - EO - PO - terminator" can also be adopted, and the structures of "initiator - EO - PO - terminator" and "initiator - EO - PO - EO - terminator" can also be adopted. However, from the actual effect, the demulsification effects of the demulsifiers with the structures of "initiator - PO - EO - terminator" and "initiator - PO - EO - PO - terminator" are relatively better.

[0011] Modification is carried out using isocyanate. Preferably, toluene diisocyanate is used for modification.

[0012] Preferably, a preparation method of a low-temperature crude oil demulsifier with a synthetic structure of "initiator - PO - EO - graft modification" is as follows:

[0013] S1: Add the initiator and 0.2 - 0.8 parts by mass of alkali into the reaction kettle and mix well;

[0014] S2: After evacuating the reaction kettle, fill it with inert gas, adjust the temperature to 120 - 130 °C, add propylene oxide and maintain the system pressure below 0.4 MPa;

[0015] S3: When the system pressure drops below 0.02 MPa, continue to add ethylene oxide and maintain the system pressure below 0.4 MPa;

[0016] S4: When the system pressure drops below 0.02 MPa, adjust the temperature to 85 - 100 °C, add the catalyst and hydrogen-containing silicone oil, react for 2 - 4 hours, and then when the temperature drops to 60 °C, add toluene diisocyanate and react for 3 hours to obtain the finished product.

[0017] Preferably, a preparation method of a low-temperature crude oil demulsifier with a synthetic structure of "initiator - PO - EO - PO - terminator" is as follows:

[0018] S1: Add the initiator and 0.2 - 0.8 parts by mass of alkali into the reaction kettle and mix well;

[0019] S2: After evacuating the reactor and filling it with inert gas, adjust the temperature to 120 - 130 °C, add at least one-third of the mass fraction of propylene oxide, and maintain the system pressure below 0.4 MPa.

[0020] S3: When the system pressure drops below 0.02 MPa, continue to add ethylene oxide and maintain the system pressure below 0.4 MPa.

[0021] S4: When the system pressure drops below 0.02 MPa, add the remaining propylene oxide and maintain the system pressure below 0.4 MPa.

[0022] S5: When the system pressure drops below 0.02 MPa, adjust the temperature to 85 - 100 °C, add a catalyst and hydrogen-containing silicone oil, react for 2 - 4 hours, and then when the temperature drops to 60 °C, add toluene diisocyanate and react for 3 hours to obtain the finished product.

[0023] Preferably, the inert gas can be nitrogen, helium, etc. From the perspective of cost, nitrogen is preferred. The so-called decompression condition refers to the condition where the vacuum degree is not less than 0.08 MPa.

[0024] Preferably, when the system pressure drops to 0.02 MPa, the next step can be carried out because when the system pressure drops to 0.02 MPa, the propylene oxide or ethylene oxide inside the system has basically reacted completely. At this time, carrying out the next step has little impact on the final product. If one insists on waiting for the pressure to drop to 0 MPa, the reaction time will increase sharply, which is not conducive to production and increases production costs.

[0025] Preferably, the catalyst is one of trifluoroacetic acid and trifluoromethanesulfonic acid, the initiator is propylenediamine, and the base is one of sodium hydroxide and potassium hydroxide.

[0026] The technical solution of the present invention also includes a low-temperature crude oil demulsifier prepared by the above preparation method. This low-temperature crude oil demulsifier can rapidly demulsify crude oil at 30 °C, and the dehydration rate can reach more than 90% in 10 minutes and more than 95% in 30 minutes, having good practical application value.

[0027] The technical solution of the present invention has the following beneficial effects compared with the prior art:

[0028] (1) The technical solution of the present invention is modified with isocyanate, that is, the entire block polyether molecular chain is modified with isocyanate to enhance its performance; it has both silicone and isocyanate groups, and for block polyether, it also contains hydroxyl and carboxyl groups. Therefore, its size is small, which can significantly improve the demulsification effect of the demulsifier. At the same time, after being modified with silicone and isocyanate, it has a positive impact on the applicable temperature of the demulsifier;

[0029] (2) The low-temperature crude oil demulsifier prepared by the preparation method of the present invention has a fast demulsification speed and good demulsification effect at normal temperature. It can be applied to some scenarios with difficult temperature rise, high requirements for demulsification speed, and high requirements for demulsification performance. And because it can demulsify at normal temperature, the equipment and energy required for temperature rise can be saved. At the same time, the raw materials used are inexpensive, and the synthesis method is simple, which is convenient for large-scale promotion. Specific Embodiments

[0030] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0031] Example 1: A preparation method of a low-temperature crude oil demulsifier, the steps are as follows: Take 10 g of propylenediamine and 5 g of sodium hydroxide and add them to a reaction kettle for mixing. After evacuating the reaction kettle, inject nitrogen to discharge the oxygen in the reaction kettle, heat up to 120 °C, inject 70 g of propylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and let it react. When the pressure in the reaction kettle drops to 0.02 MPa, inject 28 g of ethylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and let it react. When the pressure in the reaction kettle drops to 0.02 MPa, adjust the temperature to 100 °C, add 7.5 g of hydrogen-containing silicone oil and 2.5 g of trifluoromethanesulfonic acid, react for 3 h, then cool down to 60 °C, add 3 g of toluene diisocyanate, and react for 3 hours to obtain the finished product.

[0032] Example 2: A preparation method of a low-temperature crude oil demulsifier, the steps are as follows: Take 10 g of propylene diamine and 5 g of sodium hydroxide and add them to a reaction kettle for mixing. After evacuating the reaction kettle, inject nitrogen to discharge the oxygen in the reaction kettle. Heat up to 120 °C, inject 70 g of propylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and make it react. When the pressure in the reaction kettle drops to 0.02 MPa, inject 28 g of ethylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and make it react. When the pressure in the reaction kettle drops to 0 MPa, adjust the temperature to 130 °C, add 7.5 g of hydrogen-containing silicone oil and 2.5 g of trifluoromethanesulfonic acid, react for 3 h, then cool down to 60 °C, add 3 g of toluene diisocyanate, and react for 3 hours to obtain the finished product.

[0033] Compared with Example 1, Example 2 is only different in that during the preparation of the demulsifier, when the pressure in the reaction kettle drops to 0 MPa, the next step is carried out, and the reaction temperature is 130 °C, and the rest are the same.

[0034] Example 3: A preparation method of a low-temperature crude oil demulsifier, the steps are as follows: Take 10 g of propylene diamine and 5 g of sodium hydroxide and add them to a reaction kettle for mixing. After evacuating the reaction kettle, inject nitrogen to discharge the oxygen in the reaction kettle. Heat up to 120 °C, inject 90 g of propylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and make it react. When the pressure in the reaction kettle drops to 0.02 MPa, inject 35 g of ethylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and make it react. When the pressure in the reaction kettle drops to 0.02 MPa, adjust the temperature to 100 °C, add 7.5 g of hydrogen-containing silicone oil and 2.5 g of trifluoromethanesulfonic acid, react for 3 h, then cool down to 60 °C, add 3 g of toluene diisocyanate, and react for 3 hours to obtain the finished product.

[0035] Compared with Example 1, Example 3 is only different in that during the preparation of the demulsifier, the addition amount of propylene oxide is 90 g, and the addition amount of ethylene oxide is 35 g, and the rest are the same.

[0036] Example 4: A preparation method of a low-temperature crude oil demulsifier comprises the following steps: Take 10 g of propylenediamine and 5 g of sodium hydroxide and add them to a reaction kettle for mixing. After evacuating the reaction kettle, inject nitrogen to discharge the oxygen in the reaction kettle. Heat up to 120 °C, inject 70 g of propylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and let it react. When the pressure in the reaction kettle drops to 0.02 MPa, inject 28 g of ethylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and let it react. When the pressure in the reaction kettle drops to 0.02 MPa, adjust the temperature to 100 °C, add 7.5 g of hydrogen-containing silicone oil and 2.5 g of trifluoroacetic acid, react for 10 h, then cool down to 60 °C, add 3 g of toluene diisocyanate, and react for 3 h to obtain the finished product.

[0037] Compared with Example 1, Example 4 is only different in that the catalyst is changed from p-toluenesulfonic acid to trifluoroacetic acid, and the reaction time is 10 h, and the rest are the same.

[0038] Example 5: A preparation method of a low-temperature crude oil demulsifier comprises the following steps: Take 10 g of propylenediamine and 5 g of sodium hydroxide and add them to a reaction kettle for mixing. After evacuating the reaction kettle, inject nitrogen to discharge the oxygen in the reaction kettle. Heat up to 120 °C, inject 28 g of ethylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and let it react. When the pressure in the reaction kettle drops to 0.02 MPa, inject 70 g of propylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and let it react. When the pressure in the reaction kettle drops to 0.02 MPa, adjust the temperature to 100 °C, add 7.5 g of hydrogen-containing silicone oil and 2.5 g of trifluoromethanesulfonic acid, react for 3 h, then cool down to 60 °C, add 3 g of toluene diisocyanate, and react for 3 h to obtain the finished product.

[0039] Compared with Example 1, Example 5 is only different in that in the preparation process of the demulsifier, ethylene oxide is added first and then propylene oxide, and the rest are the same.

[0040] Example 6: A preparation method of a low-temperature crude oil demulsifier, the steps are as follows: Take 10 g of propylenediamine and 5 g of sodium hydroxide and add them to a reaction kettle for mixing. After evacuating the reaction kettle, inject nitrogen to discharge the oxygen in the reaction kettle. Heat up to 120 °C, inject 30 g of propylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and let it react. When the pressure in the reaction kettle drops to 0.02 MPa, inject 28 g of ethylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and let it react. When the pressure in the reaction kettle drops to 0.02 MPa, inject 40 g of propylene oxide into the reaction kettle and let it react. When the pressure in the reaction kettle drops to 0.02 MPa, adjust the temperature to 90 °C, add 7.5 g of hydrogen-containing silicone oil and 2.5 g of p-trifluoromethanesulfonic acid, react for 4 h, then cool down to 50 °C, add 1 g of hexamethylene diisocyanate, and react for 3 hours to obtain the finished product.

[0041] Example 7: A preparation method of a low-temperature crude oil demulsifier, the steps are as follows: Take 10 g of propylenediamine and 5 g of sodium hydroxide and add them to a reaction kettle for mixing. After evacuating the reaction kettle, inject nitrogen to discharge the oxygen in the reaction kettle. Heat up to 120 °C, inject 15 g of ethylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and let it react. When the pressure in the reaction kettle drops to 0.02 MPa, inject 70 g of propylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and let it react. When the pressure in the reaction kettle drops to 0.02 MPa, inject 13 g of ethylene oxide into the reaction kettle and let it react. When the pressure in the reaction kettle drops to 0.02 MPa, adjust the temperature to 90 °C, add 10.5 g of hydrogen-containing silicone oil and 3.5 g of trifluoromethanesulfonic acid, react for 4 h, keep the temperature unchanged, add 3 g of toluene diisocyanate, and react for 1 hour to obtain the finished product.

[0042] Comparative Example 1: A preparation method of a low-temperature crude oil demulsifier, the steps are as follows: Take 10 g of propylenediamine and 5 g of sodium hydroxide and add them to a reaction kettle for mixing. After evacuating the reaction kettle, inject nitrogen to discharge the oxygen in the reaction kettle. Heat up to 120 °C, inject 70 g of propylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and let it react. When the pressure in the reaction kettle drops to 0.02 MPa, inject 28 g of ethylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and let it react. When the pressure in the reaction kettle drops to 0.02 MPa, adjust the temperature to 100 °C, add 7.5 g of hydrogen-containing silicone oil and 2.5 g of trifluoroacetic acid, react for 3 h, then cool down to 60 °C, add 3 g of toluene diisocyanate, and react for 3 hours to obtain the finished product.

[0043] Compared with Example 1, the difference in Comparative Example 1 is only that during the preparation of the demulsifier, the catalyst is changed to trifluoroacetic acid and the reaction is carried out under reduced pressure, and the rest are the same.

[0044] Comparative Example 2: A preparation method of a low-temperature crude oil demulsifier, the steps are as follows: Take 10 g of ethylenediamine and 5 g of sodium hydroxide and add them to a reaction kettle for mixing. After evacuating the reaction kettle, inject nitrogen to discharge the oxygen in the reaction kettle. Heat up to 120 °C, inject 70 g of propylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and make it react. When the pressure in the reaction kettle drops to 0.02 MPa, inject 28 g of ethylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and make it react. When the pressure in the reaction kettle drops to 0.02 MPa, adjust the temperature to 100 °C, add 7.5 g of hydrogen-containing silicone oil and 2.5 g of trifluoromethanesulfonic acid, react for 3 h, then cool down to 60 °C, add 3 g of toluene diisocyanate, and react for 3 hours to obtain the finished product.

[0045] Compared with Example 1, the difference in Comparative Example 2 is only that ethylenediamine is used as the initiator, and the rest are the same.

[0046] Comparative Example 3: A preparation method of a low-temperature crude oil demulsifier, the steps are as follows: Take 10 g of propylenediamine and 5 g of sodium hydroxide and add them to a reaction kettle for mixing. After evacuating the reaction kettle, inject nitrogen to discharge the oxygen in the reaction kettle. Heat up to 120 °C, inject 40 g of propylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and make it react. When the pressure in the reaction kettle drops to 0.02 MPa, inject 20 g of ethylene oxide into the reaction kettle and maintain the pressure in the reaction kettle not higher than 0.4 MPa and make it react. When the pressure in the reaction kettle drops to 0.02 MPa, adjust the temperature to 100 °C, add 7.5 g of hydrogen-containing silicone oil and 2.5 g of trifluoromethanesulfonic acid, react for 3 h, then cool down to 60 °C, add 3 g of toluene diisocyanate, and react for 3 hours to obtain the finished product.

[0047] Compared with Example 1, the difference in Comparative Example 3 is only that during the preparation of the demulsifier, the addition amount of propylene oxide is 40 g and the addition amount of ethylene oxide is 20 g, and the rest are the same.

[0048] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that during the preparation of the demulsifier, the number-average molecular weight of the hydrogen-containing silicone oil is 2000.

[0049] Performance test: In order to further illustrate the effect of the demulsifier prepared in the above examples, the following specific tests are used for illustration.

[0050] Take the produced oil from a well in Zhongyuan Oilfield. It is heavy crude oil. Mix it with water at a ratio of 1:1 and emulsify it for 30 minutes at 2000 r / min using a high-speed emulsifier to form an emulsion. Take the demulsifiers of Examples 1-7 and Comparative Examples 1-4. The dosage of the demulsifier is 150 mg / L, and the demulsification temperature is 30 °C. Test it using the method in SY / T5280-2018. The final results are shown in Table 1. In Table 1, the blank indicates that no demulsifier is added, and the emulsion is allowed to settle naturally.

[0051] Table 1 Demulsification effects of different demulsifiers

[0052]

[0053]

[0054] It can be seen from Table 1 that for the demulsifiers of Examples 1-7, their demulsification speed is fast. The dehydration rate can reach over 86% within 10 minutes, and the highest can reach 91.4%. According to the requirements of SY / T5280-2018, for a demulsifier with a dehydration temperature less than 40 °C, a dehydration rate of over 85% is qualified. For medium crude oil, a dehydration rate of over 85% is also qualified. This shows that the demulsifier prepared in the examples of the present invention can meet the corresponding requirements in terms of demulsification effect when the demulsification time is 10 minutes. When the demulsification time is extended to 30 minutes, the dehydration rate can reach up to 95% at most, indicating that the demulsification effect at this time has exceeded that of most demulsifiers on the market. When the demulsification time is extended to 60 minutes, the change in the dehydration rate is not significant, indicating that in actual use, the demulsification time does not need to be set too long.

[0055] Referring to the demulsification effect of Comparative Example 1, it shows that after silicone grafting, it can improve the low-temperature demulsification performance of the demulsifier to a certain extent. Referring to the demulsification effect of Comparative Example 2, it shows that using the initiator of the examples of the present invention can effectively improve the demulsification performance of the demulsifier at a lower temperature compared to conventional polyamine initiators. Referring to the demulsifier of Comparative Example 3, it shows that the addition amounts of propylene oxide and ethylene oxide have a great influence on the performance of the demulsifier. Referring to the demulsifier of Comparative Example 4, it shows that the composition of the initiator has a great influence on the performance of the demulsifier.

[0056] In fact, although the above only shows the demulsification effect of the demulsifier of the examples of the present invention at 30 °C, in essence, according to the inventor's test, it can be used at a minimum temperature of 20 °C. Under this temperature condition, for the demulsifier prepared in Example 1, the dehydration rate at 10 minutes is 86.5%. When the temperature is lower, the performance of the demulsifier drops sharply, and the final demulsification effect is difficult to meet the requirements. That is to say, the demulsifier prepared in the examples of the present invention can be used in an environment with a temperature not lower than 20 °C.

[0057] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

[0058] Where the present invention is not elaborated, it is the well-known technology of those skilled in the art of the present technology.

Claims

1. A preparation method of a low-temperature crude oil demulsifier, characterized in that, It includes the following steps: Using propanediamine as the starting agent, and propylene oxide and ethylene oxide as the main agents to prepare a block polyether, then grafting with an organosilicon chain and modifying with isocyanate. The mass ratio of the starting agent, propylene oxide, ethylene oxide, and organosilicon chain is 10:(50 - 100):(25 - 40):(5 - 20).

2. The preparation method of a low-temperature crude oil demulsifier according to claim 1, characterized in that, The mass ratio of the starting agent to the isocyanate monomer is 10:(1 - 3).

3. The preparation method of a low-temperature crude oil demulsifier according to claim 2, characterized in that, The mass ratio of the starting agent, propylene oxide, ethylene oxide, and organosilicon chain is 10:(65 - 75):(25 - 30):(5 - 20).

4. The preparation method of a low-temperature crude oil demulsifier according to claim 1, characterized in that, The steps are as follows: S1: Add the starting agent and 0.2 - 0.8 parts by mass of alkali into the reaction kettle and mix well; S2: After evacuating the reaction kettle, fill it with inert gas, adjust the temperature to 120 - 130 °C, add propylene oxide and maintain the system pressure below 0.4 MPa; S3: When the system pressure drops below 0.02 MPa, continue to add ethylene oxide and maintain the system pressure below 0.4 MPa; S4: When the system pressure drops below 0.02 MPa, adjust the temperature to 85 - 100 °C, add a catalyst and hydrogen-containing silicone oil, react for 2 - 4 hours, and then when the temperature drops to 60 °C, add toluene diisocyanate for reaction to obtain the finished product.

5. The preparation method of a low-temperature crude oil demulsifier according to claim 1, characterized in that, The steps: It is characterized in that the steps are as follows: S1: Add the starting agent and 0.2 - 0.8 parts by mass of alkali into the reaction kettle and mix well; S2: After evacuating the reaction kettle, fill it with inert gas, adjust the temperature to 120 - 130 °C, add no less than one-third of the mass parts of propylene oxide and maintain the system pressure below 0.4 MPa; S3: When the system pressure drops below 0.02 MPa, continue to add ethylene oxide and maintain the system pressure below 0.4 MPa; S4: When the system pressure drops below 0.02 MPa, add the remaining propylene oxide and maintain the system pressure below 0.4 MPa; S5: When the system pressure drops below 0.02 MPa, adjust the temperature to 85 - 100 °C, add a catalyst and hydrogen-containing silicone oil, react for 2 - 4 hours, and then when the temperature drops to 60 °C, add toluene diisocyanate for reaction to obtain the finished product.

6. The preparation method of a low-temperature crude oil demulsifier according to claim 1, characterized in that, The catalyst is one of trifluoroacetic acid and trifluoromethanesulfonic acid. The starting agent is propanediamine, and the alkali is one of sodium hydroxide and potassium hydroxide.

7. A low-temperature crude oil demulsifier prepared by the method according to any one of claims 1 - 6.

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