Synthesis method of fatty acid monoethanolamide polyoxyethylene ether

Abstract

The invention relates to a method for synthesizing fatty acid monoethanolamide polyoxyethylene ether, and mainly solves the problem of high chromaticity of products in the prior art. The technical scheme is: the method for synthesizing fatty acid monoethanolamide polyoxyethylene ether comprises: in the presence of an alkaline catalyst and a catalytic aid, using fatty acid monoethanolamide as an initiator, subjecting ethylene oxide to a ring-opening polymerization reaction to obtain a fatty acid monoethanolamide polyoxyethylene ether product; the catalytic aid comprises a compound containing boron in the molecule, wherein the boron exists in the form of a borate ester bond, and can be used in the industrial application of fatty acid monoethanolamide polyoxyethylene ether.

Description

Technical Field

[0001] The invention relates to a method for synthesizing fatty acid monoethanolamide polyoxyethylene ether, in particular to a polymerization reaction using fatty acid monoethanolamide and ethylene oxide as raw materials in the presence of an alkaline catalyst, and belongs to the technical field of synthesis of organic compounds. Background Art

[0002] Fatty acid alkanolamide is a new type of green and efficient surfactant. Its raw materials are derived from natural fatty acids. It has good foaming, thickening, emulsifying and other properties. However, studies in recent years have shown that there is a lot of diethanolamine remaining in fatty acid diethanolamide, and diethanolamine has a certain carcinogenic effect on the human body. Therefore, fatty acid monoethanolamide products that do not contain diethanolamine are one of the better substitutes. Due to the poor hydrophilicity of fatty acid monoethanolamide, the application of fatty acid monoethanolamide is greatly limited. At present, there are many hydrophilic modified derivatives of fatty acid monoethanolamide. Among the many hydrophilic modified derivatives, the various properties of fatty acid monoethanolamide polyoxyethylene ether are closest to fatty acid monoethanolamide.

[0003] The current synthesis method of fatty acid monoethanolamide polyoxyethylene ether is as follows: fatty acid monoethanolamide undergoes polymerization reaction with ethylene oxide under the action of an alkaline catalyst to obtain fatty acid monoethanolamide polyoxyethylene ether; however, the fatty acid monoethanolamide polyoxyethylene ether synthesized by the current synthesis method has a darker color, which limits its scope of application.

[0004] CN110845716A provides a method for synthesizing low-color fatty acid monoethanolamide polyoxyethylene ether, wherein the main method for reducing the color is to add borohydride to reduce and decolorize after the synthesis reaction is completed. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the fatty acid monoethanolamide polyoxyethylene ether synthesized in the prior art has a deep chromaticity, and a synthesis method of fatty acid monoethanolamide polyoxyethylene ether is provided. The fatty acid monoethanolamide polyoxyethylene ether synthesized by the synthesis method has the advantage of light chromaticity.

[0006] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0007] The synthesis method of fatty acid monoethanolamide polyoxyethylene ether comprises: in the presence of an alkaline catalyst and a catalytic aid, using fatty acid monoethanolamide as an initiator, subjecting ethylene oxide to a ring-opening polymerization reaction to obtain a fatty acid monoethanolamide polyoxyethylene ether product; the catalytic aid comprises a compound containing boron in the molecule, wherein the boron exists in the form of borate ester.

[0008] The use of the above-mentioned catalytic aid significantly reduces the chromaticity of the fatty acid monoethanolamide polyoxyethylene ether product obtained in the production process of the fatty acid monoethanolamide polyoxyethylene ether obtained by ring-opening polymerization of ethylene oxide using fatty acid monoethanolamide as an initiator in the presence of an alkaline catalyst.

[0009] In the above technical solution, the catalyst promoter preferably includes a compound containing nitrogen in the molecule, or the catalyst promoter preferably includes a compound containing both boron and nitrogen in the molecule; the nitrogen exists in the form of tertiary amine nitrogen.

[0010] We found that no matter the case where the catalyst aid includes both the nitrogen-containing compound and the boron-containing compound in the above molecule, or the case where the catalyst aid includes both the boron-containing and nitrogen-containing compounds in the above molecule, in terms of reducing the chromaticity of the fatty acid monoethanolamide polyoxyethylene ether product, the nitrogen and the boron have an obvious mutual promoting effect, and this promoting effect is particularly significant in the case where the catalyst aid includes both the boron-containing and nitrogen-containing compounds in the above molecule.

[0011] In the above technical solution, the atomic ratio of boron to nitrogen is preferably 0.2 to 5. For example, but not limited to, the atomic ratio of boron to nitrogen is 0.2 (i.e. 1 / 5), 0.25 (i.e. 1 / 4), 1 / 3, 0.4, 0.5 (i.e. 1 / 2), 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.5, 3, 3.5, 4, 4.5, 5, etc.

[0012] In the above technical solution, it is preferred that the boron-containing compound in the molecule conforms to the following structural formula 1:

[0013] Structural formula 1;

[0014] Wherein, R1-R3 are independently C1-C6 aliphatic groups, for example but not limited to, R1-R3 are independently C1 aliphatic groups, C2 aliphatic groups, C3 aliphatic groups, C4 aliphatic groups, C5 aliphatic groups, C6 aliphatic groups; more preferably, hydrocarbon groups, and even more preferably, alkyl groups. For comparison only, in the specific embodiments of the present invention, when the boron-containing compound in the molecule is used, triisopropyl borate is used as a representative.

[0015] In the above technical solution, the number of carbon atoms in the molecule of the nitrogen-containing compound is preferably 3 to 30. For example, but not limited to, the number of carbon atoms in the molecule of the nitrogen-containing compound is 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, etc. For comparison only, in the specific embodiments of the present invention, triisopropanolamine is used as a representative of the nitrogen-containing compound in the molecule.

[0016] In the above technical solution, the catalyst promoter preferably includes a compound containing both boron and nitrogen in the molecule, which conforms to the following structural formula 2:

[0017] Structural formula 2;

[0018] Among them, R4, R5 and R6 are independently C2 to C18 alkylene groups, for example but not limited to, R4, R5 and R6 are independently C2 alkylene groups, C3 alkylene groups, C4 alkylene groups, C5 alkylene groups, C6 alkylene groups, C7 alkylene groups, C8 alkylene groups, C9 alkylene groups, C10 alkylene groups, C11 alkylene groups, C12 alkylene groups, C13 alkylene groups, C14 alkylene groups, C15 alkylene groups, C16 alkylene groups, C17 alkylene groups, C18 alkylene groups and the like.

[0019] In the above technical solution, preferably, R4, R5 and R6 are independently alkylene groups.

[0020] In the above technical solution, the catalyst promoter preferably conforms to the following structural formula 3:

[0021] Structural formula 3;

[0022] Among them, R7~R 18 independently selected from H or C1-C4 alkyl, such as but not limited to R7-R 18 is independently H, C1 alkyl, C2 alkyl, C3 alkyl or C4 alkyl.

[0023] For comparison only, in the specific embodiments of the present invention, when the compound containing both boron and nitrogen in the molecule is used, triethanolamine borate (CAS 283-56-7) or triisopropanolamine borate (CAS 101-00-8) is used as a representative, and triisopropanolamine borate (CAS 101-00-8) is particularly used as a representative.

[0024] In the above technical solution, the alkaline catalyst is preferably an alkali metal hydroxide or an alkali metal alkoxy compound. For example, but not limited to, the alkaline catalyst is at least one selected from the group consisting of, for example, but not limited to, potassium hydroxide, sodium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide and potassium ethoxide. For comparison only, the alkaline catalyst in the examples and comparative examples of the specific embodiments of the present invention is potassium hydroxide.

[0025] In the above technical solution, the preferred usage ratio of the catalyst promoter to the alkaline catalyst is a, 0<a≤0.5, by weight. For example, but not limited to, a is 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, etc. For comparison only, the usage ratio of the catalyst promoter to the alkaline catalyst in the examples and comparative examples of the specific embodiments of the present invention is generally 0.2.

[0026] In the above technical scheme, the amount of the catalyst used is preferably 0.1% to 0.8% of the theoretical output of fatty acid monoethanolamide polyoxyethylene ether by weight. For example, but not limited to 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, etc. For comparison only, the amount of the catalyst used in the examples and comparative examples of the specific embodiments of the present invention is generally 0.5% of the theoretical output of fatty acid monoethanolamide polyoxyethylene ether.

[0027] In the above technical solution, the fatty acid in the fatty acid monoethanolamide is preferably C8 to C 18 For example, but not limited to, the fatty acid is a C1 fatty acid, a C2 fatty acid, a C3 fatty acid, a C4 fatty acid, a C5 fatty acid, a C6 fatty acid, a C7 fatty acid, a C8 fatty acid, a C9 fatty acid, a C 10 Fatty acids, C 11 Fatty acids, C 12 Fatty acids, C 13 Fatty acids, C 14 Fatty acids, C 15 Fatty acids, C 16 Fatty acids, C 17 Fatty acids and C 18 At least one of the group consisting of fatty acids.

[0028] In the above technical solution, the fatty acid in the fatty acid monoethanolamide is a saturated or unsaturated fatty acid.

[0029] The key to the present invention is the selection of the catalyst aid. Those skilled in the art can reasonably select the amount of the catalyst, the reaction temperature, the total feed molar ratio of ethylene oxide to fatty acid monoethanolamine, the reaction pressure, etc. to achieve comparable technical effects without having to make creative efforts.

[0030] In the above technical solution, the reaction temperature is preferably 120-180° C., for example but not limited to 125° C., 130° C., 135° C., 140° C., 145° C., 150° C., 155° C., 160° C., 165° C., 170° C., 175° C., etc. More preferably, 130-150° C. For comparison only, the reaction temperature in the examples and comparative examples of the specific embodiments of the present invention is generally 150° C.

[0031] In the above technical solution, the preferred reaction pressure is -0.05MPa to 0.5MPa. For example, but not limited to, the reaction pressure is -0.04MPa, -0.03MPa, -0.02MPa, -0.01MPa, 0MPa, 0.01MPa, 0.02MPa, 0.03MPa, 0.04MPa, 0.05MPa, 0.06MPa, 0.07MPa, 0.08MPa, 0.09MPa, 0.1MPa, 0.2MPa, 0.3MPa, 0.4MPa, etc. For comparison only, the reaction pressure in the embodiments and comparative examples of the specific embodiments of the present invention is generally 0.3MPa.

[0032] In the above technical scheme, it is preferred that the total feed molar ratio of ethylene oxide to fatty acid monoethanolamide is 4 to 25, for example but not limited to the total feed molar ratio of ethylene oxide to fatty acid monoethanolamide is 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, etc. More preferably, the feed molar ratio of ethylene oxide to fatty acid monoethanolamide is 7 to 15. For comparison only, the total feed molar ratio of ethylene oxide to fatty acid monoethanolamide in the examples and comparative examples of the specific embodiments of the present invention is generally 10.

[0033] In the above technical solution, the fatty acid can be a straight-chain fatty acid or a branched fatty acid, and there is no particular limitation on this, and both can achieve comparable technical effects. For comparison only, the examples and comparative examples of the specific embodiments of the present invention all use straight-chain fatty acids.

[0034] For comparison only, the fatty acid monoethanolamide in the examples and comparative examples of the specific embodiments of the present invention all adopts oleic acid monoethanolamide.

[0035] Just as an example, a specific embodiment of the present invention includes:

[0036] Fatty acid monoethanolamide, a catalyst and a catalytic aid are put into a reaction kettle, and polymerization reaction is carried out with ethylene oxide at a reaction pressure of 0.2MPa to 0.4MPa and a reaction temperature of 120°C to 170°C to obtain fatty acid monoethanolamide polyoxyethylene ether.

[0037] The pressures in the present invention are all gauge pressures.

[0038] The chromaticity value in the specific implementation manner of the present invention is measured by using a Lovibond PFXi195 / 1 fully automatic chromaticity analyzer to measure the platinum-cobalt chromaticity of the product.

[0039] The present invention will be further described below in conjunction with various embodiments. DETAILED DESCRIPTION

[0040] [Comparative Example 1]

[0041] 150.0g oleic acid monoethanolamide and 1.77g potassium hydroxide were added to a 1L reactor with stirring, electric heating jacket and internal water cooling coil, and the reactor was sealed. The nitrogen in the reactor was replaced with nitrogen three times, stirring was turned on, the temperature was raised to 80°C and vacuum treated at a pressure of -0.06MPa for 60min, then the temperature was raised to 150°C and maintained at this temperature, ethylene oxide was introduced, and the reaction pressure was kept at 0.3MPa by controlling the introduction speed of ethylene oxide. When a total of 203.1g of ethylene oxide was introduced, the material was stopped, and the aging reaction was carried out at 150°C until the pressure no longer decreased (indicating that the aging reaction had been completed), and the vacuum treatment was carried out at a pressure of -0.09MPa for 30min, and then the temperature was reduced to 60°C to obtain the oleic acid monoethanolamide polyoxyethylene ether product.

[0042] After testing, the colorimetry (APHA) value of the fatty acid monoethanolamide polyoxyethylene ether product is 430.

[0043] [Example 1]

[0044] 150.0g oleic acid monoethanolamide, 1.77g potassium hydroxide, 0.35g triisopropyl borate were added to a 1L reactor with stirring, electric heating jacket and internal water cooling coil, and the reactor was sealed. The nitrogen in the reactor was replaced with nitrogen three times, stirring was turned on, the temperature was raised to 80°C and vacuum treated at a pressure of -0.06MPa for 60min, then the temperature was raised to 150°C and maintained at this temperature, ethylene oxide was introduced, and the reaction pressure was kept at 0.3MPa by controlling the introduction speed of ethylene oxide. When a total of 203.1g of ethylene oxide was introduced, the feed was stopped, and a slaking reaction was carried out at 150°C until the pressure no longer decreased (indicating that the slaking reaction had been completed), and a vacuum treatment was carried out at a pressure of -0.09MPa for 30min, and then the temperature was reduced to 60°C to obtain an oleic acid monoethanolamide polyoxyethylene ether product.

[0045] After testing, the colorimetry (APHA) value of the fatty acid monoethanolamide polyoxyethylene ether product is 286.

[0046]

Comparison 2

[0047] 150.0g oleic acid monoethanolamide, 1.77g potassium hydroxide, 0.35g trisodium borate (CAS14312-40-4) were added to a 1L reactor with stirring, electric heating jacket and internal water cooling coil, and the reactor was sealed. The nitrogen in the reactor was replaced with nitrogen three times, stirring was turned on, the temperature was raised to 80°C and vacuum treated at a pressure of -0.06MPa for 60min, then the temperature was raised to 150°C and maintained at this temperature, ethylene oxide was introduced, and the reaction pressure was kept at 0.3MPa by controlling the introduction speed of ethylene oxide, and the feeding was stopped after a total of 203.1g of ethylene oxide was introduced, and a slaking reaction was carried out at 150°C until the pressure no longer decreased (indicating that the slaking reaction had been completed), and a vacuum treatment was carried out at a pressure of -0.09MPa for 30min, and then the temperature was reduced to 60°C to obtain an oleic acid monoethanolamide polyoxyethylene ether product.

[0048] After testing, the colorimetry (APHA) value of the fatty acid monoethanolamide polyoxyethylene ether product is 438.

[0049]

Comparison 3

[0050] 150.0g oleic acid monoethanolamide, 1.77g potassium hydroxide, 0.35g boric acid were added to a 1L reactor with stirring, electric heating jacket and internal water cooling coil, and the reactor was sealed. The nitrogen in the reactor was replaced with nitrogen three times, stirring was turned on, the temperature was raised to 80°C and vacuum treated at a pressure of -0.06MPa for 60min, then the temperature was raised to 150°C and maintained at this temperature, ethylene oxide was introduced, and the reaction pressure was kept at 0.3MPa by controlling the introduction speed of ethylene oxide. When a total of 203.1g of ethylene oxide was introduced, the material was stopped, and a slaking reaction was carried out at 150°C until the pressure no longer decreased (indicating that the slaking reaction had been completed), and a vacuum treatment was carried out at a pressure of -0.09MPa for 30min, and then the temperature was reduced to 60°C to obtain an oleic acid monoethanolamide polyoxyethylene ether product.

[0051] After testing, the colorimetry (APHA) value of the fatty acid monoethanolamide polyoxyethylene ether product is 389.

[0052]

Comparison 4

[0053] 150.0g oleic acid monoethanolamide, 1.77g potassium hydroxide, 0.35g triisopropanolamine were added to a 1L reactor with stirring, electric heating jacket and internal water cooling coil, and the reactor was sealed. The nitrogen in the reactor was replaced with nitrogen three times, stirring was turned on, the temperature was raised to 80°C and vacuum treated for 60min at a pressure of -0.06MPa, then the temperature was raised to 150°C and maintained at this temperature, ethylene oxide was introduced, and the reaction pressure was kept at 0.3MPa by controlling the introduction speed of ethylene oxide, and the feed was stopped after a total of 203.1g of ethylene oxide was introduced, and the aging reaction was carried out at 150°C until the pressure no longer decreased (indicating that the aging reaction had been completed), and vacuum treated for 30min at a pressure of -0.09MPa, and then the temperature was reduced to 60°C to obtain the oleic acid monoethanolamide polyoxyethylene ether product.

[0054] After testing, the colorimetry (APHA) value of the fatty acid monoethanolamide polyoxyethylene ether product is 441.

[0055] [Example 2]

[0056] 150.0g oleic acid monoethanolamide, 1.77g potassium hydroxide, 0.18g triisopropyl borate and 0.18g triisopropanolamine were added to a 1L reactor with stirring, an electric heating jacket and an internal water-cooling coil, and the reactor was sealed. The nitrogen in the reactor was replaced with nitrogen three times, stirring was turned on, the temperature was raised to 80°C and vacuum-treated for 60min at a pressure of-0.06MPa, then the temperature was raised to 150°C and maintained, ethylene oxide was introduced, and the reaction pressure was kept at 0.3MPa by controlling the introduction speed of ethylene oxide, and the feed was stopped after a total of 203.1g of ethylene oxide was introduced, and the aging reaction was carried out at 150°C until the pressure no longer decreased (indicating that the aging reaction had been completed), and vacuum-treated for 30min at a pressure of-0.09MPa, and then the temperature was reduced to 60°C to obtain the oleic acid monoethanolamide polyoxyethylene ether product.

[0057] After testing, the colorimetry (APHA) value of the fatty acid monoethanolamide polyoxyethylene ether product is 237.

[0058] [Example 3]

[0059] 150.0g oleic acid monoethanolamide, 1.77g potassium hydroxide, 0.35g triisopropanolamine boric acid ester were added into a 1L reactor with stirring, electric heating jacket and internal water-cooling coil, and the reactor was sealed. The nitrogen in the reactor was replaced with nitrogen three times, stirring was turned on, and the temperature was raised to 80°C and vacuum-treated for 60min at a pressure of-0.06MPa, then the temperature was raised to 150°C and maintained, ethylene oxide was passed, and the reaction pressure was kept to be 0.3MPa by controlling the feeding speed of ethylene oxide, and the feed was stopped after a total of 203.1g of ethylene oxide was passed, and aging reaction was carried out at 150°C until the pressure no longer decreased (indicating that aging reaction had been completed), and vacuum-treated for 30min at a pressure of-0.09MPa, and then the temperature was cooled to 60°C to obtain oleic acid monoethanolamide polyoxyethylene ether product.

[0060] After testing, the colorimetry (APHA) value of the fatty acid monoethanolamide polyoxyethylene ether product is 45.

[0061] [Example 4]

[0062] 150.0g oleic acid monoethanolamide, 1.77g potassium hydroxide, 0.35g triethanolamine borate are added to a 1L reactor with stirring, electric heating jacket and internal water cooling coil, and the reactor is sealed. The nitrogen in the reactor is replaced with nitrogen three times, stirring is turned on, the temperature is raised to 80°C and vacuum treated at a pressure of -0.06MPa for 60min, then the temperature is raised to 150°C and maintained at this temperature, ethylene oxide is introduced, and the reaction pressure is kept at 0.3MPa by controlling the introduction speed of ethylene oxide. When a total of 203.1g of ethylene oxide is introduced, the material is stopped, and the aging reaction is carried out at 150°C until the pressure no longer decreases (indicating that the aging reaction has been completed), and the vacuum treatment is carried out at a pressure of -0.09MPa for 30min, and then the temperature is reduced to 60°C to obtain the oleic acid monoethanolamide polyoxyethylene ether product.

[0063] After testing, the colorimetry (APHA) value of the fatty acid monoethanolamide polyoxyethylene ether product is 56.

[0064] [Example 5]

[0065] 150.0g oleic acid monoethanolamide, 0.54g potassium hydroxide, 0.05g triisopropanolamine boric acid ester are dropped into the 1L reactor with stirring, electric heating jacket and internal water cooling coil, and the reactor is sealed. The nitrogen in the nitrogen replacement reactor is replaced three times, stirring is opened, and the temperature is raised to 80 DEG C and vacuum-treated for 60min at a pressure of-0.06MPa, then the temperature is raised to 170 DEG C and maintained at this temperature, ethylene oxide is passed, and the reaction pressure is kept to be 0.3MPa by controlling the feeding speed of ethylene oxide, and the feeding is stopped after a total of 121.8g of ethylene oxide is passed, and the aging reaction is carried out at 170 DEG C to the pressure no longer decreasing (indicating that the aging reaction has been completed), and the pressure of-0.09MPa is vacuum-treated for 30min, and then the temperature is cooled to 60 DEG C to obtain the oleic acid monoethanolamide polyoxyethylene ether product.

[0066] After testing, the colorimetry (APHA) value of the fatty acid monoethanolamide polyoxyethylene ether product is 88.

[0067] [Example 6]

[0068] 150.0g oleic acid monoethanolamide, 4.45g potassium hydroxide, 1.78g triisopropanolamine boric acid ester were added into a 1L reactor with stirring, electric heating jacket and internal water-cooling coil, and the reactor was sealed. The nitrogen in the nitrogen replacement reactor was replaced three times, stirring was opened, and the temperature was raised to 80°C and vacuum-treated for 60min at a pressure of-0.06MPa, then the temperature was raised to 120°C and maintained, ethylene oxide was passed, and the reaction pressure was kept to be 0.3MPa by controlling the feeding speed of ethylene oxide, and the feed was stopped after a total of 406.2g of ethylene oxide was passed, and aging reaction was carried out at 120°C until the pressure no longer decreased (indicating that aging reaction had been completed), and vacuum-treated for 30min at a pressure of-0.09MPa, and then the temperature was cooled to 60°C to obtain oleic acid monoethanolamide polyoxyethylene ether product.

[0069] After testing, the colorimetry (APHA) value of the fatty acid monoethanolamide polyoxyethylene ether product is 62.

[0070] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for synthesizing fatty acid monoethanolamide polyoxyethylene ether, comprising: In the presence of an alkaline catalyst and a catalyst aid, fatty acid monoethanolamide is used as an initiator, and ethylene oxide undergoes a ring-opening polymerization reaction to obtain a fatty acid monoethanolamide polyoxyethylene ether product; The catalyst aid includes a compound containing boron in the molecule; the weight ratio of the catalyst aid to the alkaline catalyst is a, 0<a≤0.5; the amount of the catalyst is 0.1% to 0.8% of the theoretical output of fatty acid monoethanolamide polyoxyethylene ether; The boron-containing compound in the molecule conforms to the following structural formula 1 or conforms to the following structural formula 2: , structural formula 1, Wherein, R1~R3 ​​are independently C1~C6 alkyl groups, , structural formula 2; Wherein, R4, R5 and R6 are independently C2~C18 alkylene groups.

2. The synthesis method according to claim 1, characterized in that The catalyst promoter includes a compound containing nitrogen in the molecule and a compound shown in structural formula 1, wherein the nitrogen exists in the form of tertiary amine nitrogen.

3. The synthetic method according to claim 2, characterized in that The atomic ratio of the boron to the nitrogen is 0.2-5.

4. The synthesis method according to claim 2, characterized in that The carbon number of the nitrogen-containing compound in the molecule is 3 to 30.

5. The synthesis method according to claim 1, characterized in that The boron-containing compound in the molecule conforms to the following structural formula 3: , structural formula 3; Among them, R7~R 18 Independently selected from H or C1~C4 alkyl.

6. The synthesis method according to claim 1, characterized in that The alkaline catalyst is an alkali metal hydroxide or an alkali metal alkoxide.

7. The synthesis method according to claim 1, characterized in that The fatty acid described in fatty acid monoethanolamide is C8~C 18 of fatty acids.

8. The synthesis method according to claim 7, characterized in that The fatty acid is a saturated or unsaturated fatty acid.

9. The synthesis method according to claim 1, characterized in that The reaction temperature is 120-180°C.

10. The synthesis method according to claim 1, characterized in that The reaction temperature is 130-150°C.

11. The synthesis method according to claim 1, characterized in that The reaction pressure is -0.05MPa~0.5MPa.

12. The synthesis method according to claim 1, characterized in that The total feed molar ratio of ethylene oxide to fatty acid monoethanolamide is 4-25.

13. The synthesis method according to claim 12, characterized in that The feeding molar ratio of ethylene oxide to fatty acid monoethanolamide is 7-15.

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