Method for synthesizing betaine surfactant from natural grease through one-pot method and betaine surfactant

Abstract

The invention relates to a method for synthesizing a betaine surfactant from natural oil by a one-pot method and the betaine surfactant, and the method comprises the following steps: 1, placing the natural oil and N, N-dimethyl-1, 3-propane diamine in a reaction container according to a mass ratio of 7.5: 1-0.4: 1 at normal temperature, adding the natural oil and the N, N-dimethyl-1, 3-propane diamine into the reaction container, and reacting for 2-4 hours; the mass of the catalyst is 0.1-0.9% of the total mass of 1, 3-propane diamine; 2, mixing and stirring the reactants, heating to 120-190 DEG C, and carrying out reflux reaction for 5-9 hours; 3, after the reaction is finished, cooling to room temperature, and adding water which is 0.4-4.1 times of the total mass of the mixture, chloroacetate which is 0.6-1.8 times of the total mass of the mixture and a cosolvent which is 0.4-2.3 times of the total mass of the mixture; and 4, carrying out a stirring reflux reaction on the mixture at 60-110 DEG C for 4-8 hours, and after the reaction is finished, cooling to room temperature to obtain a finished product. According to the technical scheme, the synthesis process of the traditional long-chain fatty acid amide betaine is simplified, the process of preparing fatty acid by hydrolyzing natural oil can be reduced, the steps are simple, and the production cost is effectively reduced. Therefore, different types of oil-displacing agents suitable for oil fields are prepared.

Description

Technical Field

[0001] The invention relates to the technical field of preparation and application of betaine type surfactants, and in particular to a method for synthesizing betaine surfactants from natural oils and fats in one pot. Background Art

[0002] At present, surfactants used in oilfield flooding are required to have a sufficiently large carbon number, good water solubility, and suitable cost, and the synthesis process is simple, mature, and easy to industrialize. Fatty acid-based betaine-type surfactants have good properties such as temperature resistance, salt resistance, good biodegradability, and low damage. At the same time, its head group contains cationic and anionic groups, and the structure contains double bonds, amide bonds, and other groups that enhance solubility, showing many characteristics suitable for formulation, such as high water solubility, low critical micelle concentration, and reduced oil-water interfacial tension. This special molecular structure enables betaine-type surfactants to reduce the adhesion work required for stripping crude oil when used for oil recovery, significantly improving the efficiency of oil washing. Therefore, betaine-type surfactants are in huge demand in tertiary oil recovery in low permeability oil fields.

[0003] The synthesis of betaine-type surfactants usually uses natural oils as raw materials. Fatty acids are first produced through saponification, salting out, acidolysis, and hydrolysis, and then betaine-type surfactants are synthesized through a series of processes such as amidation and quaternization. This process has the disadvantages of complex flow, long production time, and high preparation cost. In addition, betaine-type surfactants for oil fields are mostly used in the form of surfactants with different chain lengths to reduce oil-water interfacial tension and improve oil washing efficiency. Summary of the invention

[0004] In view of the above problems, in order to solve the above problems, the present invention provides a preparation method, which uses natural oils as raw materials to directly synthesize betaine-type surfactants in a one-pot method. The method eliminates the saponification, salting out, acid hydrolysis, and hydrolysis process links, realizes the effective utilization of raw materials, improves the preparation efficiency, and the product has a good oil displacement effect, providing an efficient and convenient new way for the low-cost production of surfactants and the three-recovery enhancement of oil recovery.

[0005] To achieve the above object, the inventors provide a method for synthesizing betaine surfactants from natural oils in one pot, comprising: a first step, placing natural oils and N,N-dimethyl-1,3-propylenediamine in a reaction vessel at a mass ratio of 7.5:1 to 0.4:1 at room temperature, and adding a catalyst in an amount of 0.1% to 0.9% of the total mass of the natural oils and N,N-dimethyl-1,3-propylenediamine;

[0006] The second step is to mix and stir the above reactants, and heat them at 120°C-190°C for reflux reaction for 5-9 hours;

[0007] The third step is to cool the mixture to room temperature after the reaction is completed, and then add 0.4-4.1 times the total mass of water, 0.6-1.8 times the total mass of chloroacetate and 0.4-2.3 times the total mass of the mixture;

[0008] The fourth step is to stir the mixture under reflux at 60-110° C. for 4-8 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain the finished product.

[0009] In one embodiment of the present application, the natural oil is one or a mixture of two or more of commercially available qualified industrial grade or higher purity rapeseed oil, soybean oil, peanut oil, corn oil, cottonseed oil, castor oil, palm oil, lard, mutton fat, and tallow, and the reactant N,N-dimethyl-1,3-propylenediamine is a product of industrial grade or higher purity.

[0010] In one embodiment of the present application, the chloroacetate is sodium chloroacetate, potassium chloroacetate, or ammonium chloroacetate of industrial grade or higher purity.

[0011] In one embodiment of the present application, the water has a total mineralization of no more than 300 mg / L.

[0012] In one embodiment of the present application, the calcium and magnesium ion content is no more than 20 mg / L of deionized water or tap water.

[0013] In one embodiment of the present application, the co-solvent is one or more of glycerol, ethylene glycol, propylene glycol, isopropanol, and butanol.

[0014] In one embodiment of the present application, the catalyst is potassium carbonate or potassium hydroxide.

[0015] A betaine surfactant, wherein the betaine surfactant is a betaine-type surfactant prepared by any of the above methods.

[0016] In one embodiment of the present application, the betaine surfactant is used to improve crude oil recovery in oil fields.

[0017] Different from the prior art, the above technical scheme simplifies the synthesis process of traditional long-chain fatty acid amide betaine, and the synthesis of its amide intermediate is synthesized by high-temperature dehydration of traditional fatty acids and amines to synthesize amides. The required surfactant can be prepared in one pot by using a catalyst, which can reduce the process of preparing fatty acids by hydrolysis of natural oils and fats. The steps are simple and the production cost is effectively reduced. And by using the method of natural oils and fats, the long-chain fatty acids contained in natural oils and fats are directly assembled from the source to prepare oil displacement agents suitable for different types of oil fields. Compared with the traditional purification process, the long-chain fatty acid amide betaine prepared by the present invention has a comparable effect, has the advantages of good dispersibility in aqueous solution, high stability, low interfacial tension, etc., and can be used for oil field flooding to significantly improve the recovery rate.

[0018] The above-mentioned records related to the invention content are only an overview of the technical solution of the present application. In order to enable ordinary technicians in the field to more clearly understand the technical solution of the present application, and then implement it according to the written contents of the specification, and to make the above-mentioned purpose and other purposes, features and advantages of the present application easier to understand, the specific implementation methods of the present application are explained below. DETAILED DESCRIPTION

[0019] In order to explain in detail the possible application scenarios, technical principles, specific schemes that can be implemented, and the purposes and effects that can be achieved, the following is a detailed description in conjunction with the specific embodiments listed. The embodiments described herein are only used to more clearly illustrate the technical solutions of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0020] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0021] Unless otherwise defined, the technical terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms in this document is only for describing specific embodiments and is not intended to limit this application.

[0022] In the description of this application, the term "and / or" is an expression used to describe the logical relationship between objects, indicating that three relationships may exist, for example, A and / or B, which means: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this article generally indicates that the objects before and after are in an "or" logical relationship.

[0023] In the present application, terms such as “first” and “second” are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship of quantity, priority or sequence between these entities or operations.

[0024] Without further limitations, in this application, the words "include", "comprises", "has" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those limited elements, but also other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0025] In this application, expressions such as "greater than", "less than", "exceed" and the like are understood to exclude the number itself; expressions such as "above", "below", "within" and the like are understood to include the number itself. In addition, in the description of the embodiments of this application, "multiple" means more than two (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups", "multiple times", etc., unless otherwise clearly and specifically limited.

[0026] In the description of the embodiments of the present application, space-related expressions used, such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or position relationship based on the orientation or position relationship shown in the specific embodiments, which is only for the convenience of describing the specific embodiments of the present application or facilitating the reader's understanding, and does not indicate or imply that the referred device or component must have a specific position, a specific orientation, or be constructed or operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0027] In one aspect of the present application, a method for synthesizing a betaine surfactant from natural oils in one pot is provided, comprising: a first step, placing natural oils and N,N-dimethyl-1,3-propylenediamine in a reaction vessel at a mass ratio of 7.5:1 to 0.4:1 at room temperature, and adding a catalyst in an amount of 0.1%-0.9% of the total mass of the natural oils and N,N-dimethyl-1,3-propylenediamine; a second step, mixing and stirring the above reactants, heating to 120°C-190°C, and reflux reacting for 5-9 hours; a third step, after the reaction is completed, cooling to room temperature, and then adding 0.4-4.1 times the total mass of water, 0.6-1.8 times the amount of chloroacetate, and 0.4-2.3 times the amount of a solvent in an amount of the above mixture, wherein the chloroacetate is sodium chloroacetate, potassium chloroacetate, and ammonium chloroacetate of industrial grade or higher purity; a fourth step, stirring and reflux reacting the above mixture at 60-110°C for 4-8 hours, and after the reaction is completed, cooling to room temperature to obtain a finished product.

[0028] The one-pot method in the above steps means that all reactions can be carried out in a single reaction vessel from the beginning to the end, wherein the reflux reaction refers to the distillation operation in which the rising vapor drawn from the top of the distillation tower is condensed by the condenser and a portion of the liquid is sent back to the tower. The room temperature and normal temperature can be 15°C-30°C, and in some embodiments, preferably 22°C.

[0029] Through the above-mentioned preparation method, the synthesis process of traditional long-chain fatty acid amide betaine is simplified, and the synthesis of its amide intermediate is synthesized by high-temperature dehydration of traditional fatty acids and amines to synthesize amides. The required surfactant can be prepared in one pot by using a catalyst, which can reduce the process of preparing fatty acids by hydrolysis of natural oils and fats. The steps are simple and the production cost is effectively reduced. And by using the method of natural oils and fats, the long-chain fatty acids contained in natural oils and fats are directly assembled from the source to prepare oil displacement agents suitable for different types of oil fields. Compared with the traditional purification process, the long-chain fatty acid amide betaine prepared by the present invention has a comparable effect and has the advantages of good dispersibility in aqueous solution, high stability, and low interfacial tension.

[0030] In one aspect of the present application, the natural oil is one or a mixture of two or more of commercially available qualified industrial grade or higher purity rapeseed oil, soybean oil, peanut oil, corn oil, cottonseed oil, castor oil, palm oil, lard, sheep oil, and tallow, and the reactant N,N-dimethyl-1,3-propylenediamine is an industrial grade or higher purity product. The long-chain fatty acids contained in the natural oil are directly assembled from the source to prepare oil displacement agents suitable for different types of oil fields.

[0031] In one aspect of the present application, the water has a total mineralization of no more than 300 mg / L, which can ensure the smooth progress of the reaction.

[0032] In one aspect of the present application, deionized water or tap water with a calcium and magnesium ion content of no more than 20 mg / L can ensure the smooth progress of the reaction.

[0033] In some aspects of the present application, the cosolvent is one or more of glycerol, ethylene glycol, propylene glycol, isopropanol, and butanol. The cosolvent can promote the dissolution of natural oil fatty acids and reactants.

[0034] In one aspect of the present application, the catalyst is potassium carbonate or potassium hydroxide, and the catalyst may be of industrial grade purity or above, and the catalyst may promote the direct reaction of natural oils and amines to synthesize amides.

[0035] In one aspect of the present application, a betaine surfactant is also provided, wherein the betaine surfactant is a betaine-type surfactant prepared by any of the methods described above or by the method described in any group of embodiments.

[0036] In one embodiment of the present application, the betaine surfactant is used to improve crude oil recovery in oil fields. It is used as an oil displacement agent. It has the characteristics of high temperature resistance, salt resistance, low pollution, low damage, easy operation, and strong oil displacement function when used as an oil displacement agent. Second, it can effectively reduce the oil / water interfacial tension, thereby greatly reducing or eliminating the capillary action of the formation, reducing the adhesion work required for stripping crude oil, and improving the oil washing efficiency. Change the wettability of the rock surface. Third, it can greatly increase the wetting angle between crude oil and rock, so that any wettability rock surface can become strongly hydrophilic, and no wetting reversal will occur, which is extremely beneficial for water flooding. Core displacement increases the oil recovery efficiency by more than 10%.

[0037] The following describes the process in conjunction with some specific embodiments.

[0038] Example 1

[0039] The method for synthesizing betaine surfactant from natural oils and fats in one pot comprises the following steps:

[0040] The first step is to place rapeseed oil and N,N-dimethyl-1,3-propylenediamine in a reaction vessel at a mass ratio of 7.1:1 at room temperature, and add a catalyst potassium carbonate, the mass of which is 0.5% of the total mass of rapeseed oil and N,N-dimethyl-1,3-propylenediamine, wherein the natural oil is commercially available qualified industrial-grade rapeseed oil, the reactant N,N-dimethyl-1,3-propylenediamine is an industrial-grade purity product, and the catalyst is industrial-grade purity potassium carbonate;

[0041] The second step is to mix and stir the above reactants, heat to 160°C, and reflux for 6.5 hours;

[0042] The third step, after the reaction is completed, cool to room temperature, and then add 1.4 times the total mass of water, 1.1 times the sodium chloroacetate and 0.68 times the glycerol of the above mixture, wherein the water is deionized water with a total mineralization of 112 mg / L and a calcium and magnesium ion content of 8 mg / L, the sodium chloroacetate is an analytical grade purity product, and the glycerol is an industrial grade purity product;

[0043] The fourth step is to stir the mixture at 90° C. and reflux for reaction for 6 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a betaine surfactant for enhancing crude oil recovery in oil fields.

[0044] The oil displacement agent is prepared into a 1.5% aqueous solution, which can reduce the oil-water interfacial tension to 2.51×10-3mN / m and improve the core oil displacement efficiency by 12.7%.

[0045] Example 2

[0046] The method for synthesizing betaine surfactant from natural oils and fats in one pot comprises the following steps:

[0047] The first step is to place castor oil and N, N-dimethyl-1, 3-propylenediamine in a reaction container at a mass ratio of 0.63:1 at room temperature, and add a catalyst potassium hydroxide, the mass of which is 0.3% of the total mass of castor oil and N, N-dimethyl-1, 3-propylenediamine, the natural oil is commercially available qualified industrial grade castor oil, the reactant N, N-dimethyl-1, 3-propylenediamine is an industrial grade purity product, and the catalyst is industrial grade purity potassium hydroxide;

[0048] The second step is to mix and stir the above reactants, heat to 130°C, and reflux for 8 hours;

[0049] The third step, after the reaction is completed, cool to room temperature, and then add 2.3 times the total mass of the mixture of water, 0.9 times the potassium chloroacetate and 1.91 times the propylene glycol, wherein the water is deionized water with a total mineralization of 150 mg / L and a calcium and magnesium ion content of 11 mg / L, the potassium chloroacetate is an industrial grade purity product, and the propylene glycol is an industrial grade purity product;

[0050] The fourth step is to stir the mixture at 75° C. and reflux for reaction for 7 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a betaine surfactant for enhancing crude oil recovery in oil fields.

[0051] The oil displacement agent is prepared into a 0.8% aqueous solution, which can reduce the oil-water interfacial tension to 5.86×10-3mN / m and improve the core oil displacement efficiency by 11.4%.

[0052] Example 3

[0053] The method for synthesizing betaine surfactant from natural oils and fats in one pot comprises the following steps:

[0054] The first step is to place lard and N,N-dimethyl-1,3-propylenediamine in a reaction vessel at a mass ratio of 3.17:1 at room temperature, and add a catalyst potassium hydroxide, the mass of which is 0.6% of the total mass of lard and N,N-dimethyl-1,3-propylenediamine, wherein the natural oil is commercially available qualified industrial-grade lard, the reactant N,N-dimethyl-1,3-propylenediamine is a chemically pure product, and the catalyst is chemically pure potassium hydroxide;

[0055] The second step is to mix and stir the above reactants, heat to 170°C, and reflux for 6 hours;

[0056] The third step, after the reaction is completed, the mixture is cooled to room temperature, and then 3.7 times the total mass of water, 1.6 times the amount of potassium chloroacetate and 1.6 times the amount of butanol are added to the mixture, wherein the water is deionized water with a total mineralization of 185 mg / L and a calcium and magnesium ion content of 13.4 mg / L, the potassium chloroacetate is an analytical grade product, and the butanol is a chemically pure grade product;

[0057] The fourth step is to stir the mixture under reflux at 100° C. for 5 hours, and after the reaction is completed, the mixture is cooled to room temperature to obtain a betaine surfactant for enhancing crude oil recovery in oil fields.

[0058] The oil displacement agent is prepared into a 1.0% aqueous solution, which can reduce the oil-water interfacial tension to 2.34×10-3mN / m and improve the core oil displacement efficiency by 11.9%.

[0059] Example 4

[0060] The method for synthesizing betaine surfactant from natural oils and fats in one pot comprises the following steps:

[0061] The first step is to mix peanut oil and lard at a mass ratio of 1:1 at room temperature, place the mixed oil and N,N-dimethyl-1,3-propylenediamine in a reaction container at a mass ratio of 3.7:1, and add a catalyst potassium carbonate, the mass of which is 0.7% of the total mass of the mixed oil and N,N-dimethyl-1,3-propylenediamine, wherein the natural oil is commercially available qualified industrial grade peanut oil and lard, the reactant N,N-dimethyl-1,3-propylenediamine is an analytical grade purity product, and the catalyst is chemically pure grade potassium carbonate;

[0062] The second step is to mix and stir the above reactants, heat to 180°C, and reflux for 5.5 hours;

[0063] The third step, after the reaction is completed, cool to room temperature, and then add 0.9 times the total mass of water, 1.4 times the amount of ammonium chloroacetate and 0.5 times the amount of isopropanol in the above mixture, wherein the water is deionized water with a total mineralization of 110 mg / L and a calcium and magnesium ion content of 7.2 mg / L, the ammonium chloroacetate is a chemically pure product, and the isopropanol is an industrial grade product;

[0064] The fourth step is to stir the mixture at 60° C. and reflux for reaction for 8 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a betaine surfactant for enhancing crude oil recovery in oil fields.

[0065] The oil displacement agent is prepared into a 2.0% aqueous solution, which can reduce the oil-water interfacial tension to 7.58×10-4mN / m and improve the core oil displacement efficiency by 13.0%.

[0066] Example 5

[0067] The method for synthesizing betaine surfactant from natural oils and fats in one pot comprises the following steps:

[0068] The first step is to mix cottonseed oil and soybean oil at a mass ratio of 2:1 at room temperature, place the mixed oil and N,N-dimethyl-1,3-propylenediamine in a reaction container at a mass ratio of 2.6:1, and add a catalyst potassium carbonate, the mass of which is 0.2% of the total mass of the mixed oil and N,N-dimethyl-1,3-propylenediamine, the natural oils and fats are commercially available qualified industrial grade cottonseed oil and soybean oil, the reactant N,N-dimethyl-1,3-propylenediamine is a chemically pure product, and the catalyst is industrial grade potassium carbonate;

[0069] The second step is to mix and stir the above reactants, heat to 120°C, and reflux for 9 hours;

[0070] The third step, after the reaction is completed, cool to room temperature, and then add 2.3 times the total mass of the mixture of water, 0.5 times the sodium chloroacetate and 2.0 times the ethylene glycol, the water is tap water with a total mineralization of 280 mg / L and a calcium and magnesium ion content of 18.7 mg / L, the sodium chloroacetate is an industrial grade product, and the isopropanol is an industrial grade product;

[0071] In the fourth step, the mixture is stirred and refluxed at 80° C. for 6.5 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a betaine surfactant for enhancing crude oil recovery in oil fields.

[0072] The oil displacement agent is prepared into a 1.2% aqueous solution, which can reduce the oil-water interfacial tension to 1.47×10-3mN / m and improve the core oil displacement efficiency by 12.4%.

[0073] Example 6

[0074] The method for synthesizing betaine surfactant from natural oils and fats in one pot comprises the following steps:

[0075] The first step is to place palm oil and N,N-dimethyl-1,3-propylenediamine in a reaction vessel at a mass ratio of 1.8:1 at room temperature, and add a catalyst of potassium hydroxide, the mass of which is 0.8% of the total mass of palm oil and N,N-dimethyl-1,3-propylenediamine, the natural oil is commercially available qualified industrial grade palm oil, the reactant N,N-dimethyl-1,3-propylenediamine is an analytical grade purity product, and the catalyst is chemical grade purity potassium hydroxide;

[0076] The second step is to mix and stir the above reactants, heat to 145°C, and reflux for 8 hours;

[0077] The third step, after the reaction is completed, cool to room temperature, and then add 4.0 times the total mass of the mixture of water, 1.3 times the amount of ammonium chloroacetate and 0.7 times the amount of butanol, wherein the water is deionized water with a total mineralization of 74 mg / L and a calcium and magnesium ion content of 5.2 mg / L, the ammonium chloroacetate is a chemically pure product, and the isopropanol is an analytically pure product;

[0078] The fourth step is to stir the mixture at 60° C. and reflux for reaction for 8 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a betaine surfactant for enhancing crude oil recovery in oil fields.

[0079] The oil displacement agent is prepared into a 0.5% aqueous solution, which can reduce the oil-water interfacial tension to 3.9×10-3mN / m and improve the core oil displacement efficiency by 11.0%.

[0080] Finally, it should be noted that although the above embodiments have been described in the text of the specification of this application, this does not limit the scope of patent protection of this application. All technical solutions generated by replacing or modifying equivalent structures or equivalent processes based on the essential concept of this application using the contents recorded in the specification of this application, as well as directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, are included in the scope of patent protection of this application.

Claims

1. A method for synthesizing betaine surfactants from natural oils and fats in one pot, characterized in that: include: The first step is to place natural oil and N, N-dimethyl-1, 3-propylenediamine in a reaction vessel at a mass ratio of 7.5:1 to 0.4:1 at room temperature, and add a catalyst in an amount of 0.1% to 0.9% of the total mass of the natural oil and N, N-dimethyl-1, 3-propylenediamine; The second step is to mix and stir the above reactants, heat them, and reflux them for 5-9 hours; The third step is to cool the mixture to room temperature after the reaction is completed, and then add 0.4-4.1 times the total mass of water, 0.6-1.8 times the amount of chloroacetate, and 0.4-2.3 times the amount of a cosolvent, wherein the chloroacetate is sodium chloroacetate, potassium chloroacetate, or ammonium chloroacetate of industrial grade or higher purity; The fourth step is to stir the mixture under reflux at 60-110° C. for 4-8 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain the finished product.

2. The method for synthesizing betaine surfactant from natural oils and fats in one pot according to claim 1, characterized in that: The natural oil is one or a mixture of two or more of commercially available qualified industrial grade or higher purity rapeseed oil, soybean oil, peanut oil, corn oil, cottonseed oil, castor oil, palm oil, lard, sheep oil, and tallow, and the reactant N,N-dimethyl-1,3-propylenediamine is a product of industrial grade or higher purity.

3. The method for synthesizing betaine surfactant from natural oils and fats in one pot according to claim 1, characterized in that: The water has a total mineralization of no more than 300 mg / L.

4. The method for synthesizing betaine surfactant from natural oils and fats in one pot according to claim 3, characterized in that: Deionized water or tap water with a calcium and magnesium ion content not exceeding 20 mg / L.

5. The method for synthesizing betaine surfactant from natural oils and fats in one pot according to claim 1, characterized in that: The co-solvent is one or more of glycerol, ethylene glycol, propylene glycol, isopropanol and butanol.

6. The method for synthesizing betaine surfactant from natural oils and fats in one pot according to claim 1, characterized in that: The catalyst is potassium carbonate or potassium hydroxide.

7. The method for synthesizing betaine surfactant from natural oils and fats in one pot according to claim 1, characterized in that: The chloroacetate includes sodium chloroacetate, potassium chloroacetate and ammonium chloroacetate.

8. The method for synthesizing betaine surfactant from natural oils and fats in one pot according to claim 1, characterized in that: In the second step, the temperature is heated to 120° C.-190° C., and then a reflux reaction is performed.

9. A betaine surfactant, characterized in that The betaine surfactant is a betaine-type surfactant prepared by the method according to any one of claims 1 to 8.

10. The betaine surfactant according to claim 9, characterized in that The betaine surfactant is used for improving crude oil recovery in oil fields.