A kind of synthetic method of N-tert-butyl diethanolamine

Abstract

The invention discloses a synthetic method of N-tert-butyldiethanolamine, and belongs to the technical field of organic synthesis. The synthetic method of the N-tert-butyldiethanolamine is by first adding a carbon-supported weak acid metal salt catalyst and an auxiliary agent into a reactor, pumping tert-butylamine at a negative pressure, slowly dropping ethylene oxide, and pre-reacting tert-butylamine with ethylene oxide, when the pressure in the kettle is rapidly reduced and the reaction temperature is significantly increased, the reaction is activated, cooling water is turned on, the reaction temperature is controlled, until the reaction is stable, then ethylene oxide is slowly dropped to react, and the addition is completed and ripened, until the pressure is substantially unchanged, the reaction is completed, and the filtrate is taken after degassing, cooling, and filtering, that is, to obtain. The present invention is catalytically reacted by a carbon-supported weak acid metal salt catalyst and an auxiliary agent, promotes the reaction, and adjusts the acid-base balance of the reaction environment to control the reaction process and then prevent overreaction, effectively improves product purity, and the process is simple and easy to operate, economical and environmentally friendly.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a method for synthesizing N-tert-butyl diethanolamine. Background Art

[0002] As an important chemical raw material or intermediate, N-tert-butyldiethanolamine is widely used in the fields of medicine, pesticides and dyes. However, the existing tert-butyldiethanolamine synthesis methods are complicated in operation, high in energy consumption, harsh in reaction conditions, serious in environmental pollution, and low in product purity. For example, the method disclosed in Japanese patent JP2011178664A requires an extremely high reaction temperature, which leads to excessive pressure and thus affects the feeding of ethylene oxide, making it difficult to achieve industrial production; although Chinese patent CN103373930A uses negative pressure feeding and catalyst to accelerate the reaction, the reaction process is difficult to control, the product purity is low, and there are problems such as corrosion of equipment and difficulty in recovery, high production cost, etc., and it will also increase the three wastes and cause environmental pollution. Due to the tert-butyl effect of tert-butylamine, the primary amine connected to it is usually difficult to react with ethylene oxide in an autocatalytic manner, and the use of ordinary acid and base catalysts for catalytic reaction makes the reaction process difficult to control and the reaction is not thorough. At the same time, the generated N-tert-butyldiethanolamine TBA can continue to react with ethylene oxide to generate the byproduct HETBA shown in the following reaction formula.

[0003]

[0004] It may even lead to further reaction and overreaction.

[0005] Therefore, it is very necessary to develop a method for synthesizing N-tert-butyl diethanolamine with controllable reaction process, high product purity, simple and easy operation, economy and environmental protection. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for synthesizing N-tert-butyl diethanolamine. The method adopts a specific catalyst in combination with a specific auxiliary agent, which can not only enhance the catalytic activity and stability without increasing the amount of the catalyst, but also the catalyst and the auxiliary agent can synergistically adjust the acid-base balance of the reaction environment to control the reaction process and prevent overreaction, thereby effectively improving the purity of the product, and the process is simple, easy to operate, economical and environmentally friendly.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0008] A method for synthesizing N-tert-butyl diethanolamine comprises the following steps:

[0009] S1. Put the catalyst and the auxiliary agent into a dry reactor, replace the nitrogen, and then pump tert-butylamine into the reactor under negative pressure, start stirring, and heat the temperature in the reactor to 50-130° C.; the catalyst is a carbon-supported weak acid metal salt catalyst; and the auxiliary agent is a weak acid;

[0010] S2. Keep the temperature in the kettle unchanged and slowly add ethylene oxide into the kettle until the pressure is maintained at 0.3-0.8Mpa to carry out a preliminary reaction;

[0011] S3. When the pressure in the kettle drops rapidly and the reaction temperature rises significantly, the reaction is activated, the cooling water is turned on, and the reaction temperature is controlled to be 50-130°C until the reaction is stable;

[0012] S4, controlling the reaction temperature to remain unchanged, slowly adding ethylene oxide dropwise to react, and aging after the addition is completed until the pressure remains substantially unchanged and the reaction is completed;

[0013] S5. Keep the temperature constant, degas, cool down, and filter the filtrate to obtain N-tert-butyl diethanolamine; the filtered catalyst can be reused after treatment.

[0014] The reaction equation of the above synthesis method is:

[0015] (1)

[0016] (2)

[0017] As a preferred embodiment of the present invention, the weak acid metal salt in the carbon-supported weak acid metal salt catalyst in step S1 is a weak acid transition metal salt, wherein the transition metal is one or more of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn; the weak acid radical ion in the weak acid transition metal salt is CH3COO-, CN-, F-, SO3 2- 、SiO3 2- One or more of .

[0018] More preferably, the transition metal is one or more of Cr, Ni, and Zn; the weak acid radical ions in the weak acid transition metal salt are CH3COO-, SO3 2- 、SiO3 2- One or more of.

[0019] As a preferred embodiment of the present invention, the auxiliary agent in step S1 is one or more of CH3COOH, C2H5COOH, H2SiO3, HCN, HF, H2SO3, C6H5COOH, CH2=CHCOOH; preferably one or more of CH3COOH, C6H5COOH, H2SiO3.

[0020] As a preferred embodiment of the present invention, the metal salt loading in the carbon-supported weak acid metal salt catalyst in step S1 is 10-40% of the total mass of the carbon-supported weak acid metal salt catalyst, preferably 15-30%.

[0021] As a preferred embodiment of the present invention, the amount of the carbon-supported weak acid metal salt catalyst added in step S1 is 0.15-4% of the mass of tert-butylamine, preferably 0.3-3%; the amount of the auxiliary agent added is 1-50% of the mass of the carbon-supported weak acid metal salt catalyst, preferably 5-30%.

[0022] As a preferred embodiment of the present invention, the number of nitrogen additions in step S1 is 2 to 3 times.

[0023] As a preferred embodiment of the present invention, in step S2, after the pressure drops, ethylene oxide is continuously added dropwise to keep the pressure within 0.3 to 0.8 MPa, preferably within 0.4 to 0.6 MPa.

[0024] As a preferred embodiment of the present invention, the reaction temperature in step S3 is 50-130°C.

[0025] As a preferred embodiment of the present invention, the amount of ethylene oxide added in step S4 is 1.5 to 2.5 times the molar number of tert-butylamine; preferably, the amount of ethylene oxide added is 1.8 to 2.2 times the molar number of tert-butylamine.

[0026] As a preferred embodiment of the present invention, in step S5, after degassing to a pressure of -0.098 MPa, degassing is continued for 30 minutes, and the temperature is lowered to below 60° C. before filtering.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The synthesis method provided by the present invention combines a carbon-supported weak acid metal salt catalyst with a weak acid auxiliary agent, and adjusts the acid-base balance of the reaction environment during the catalytic reaction of tert-butylamine and ethylene oxide, so that the reaction process is easy to control, thereby preventing overreaction, and the content of by-products in the product is small, thereby greatly improving the purity of the product N-tert-butyl diethanolamine. At the same time, the present invention does not need to perform high energy-consuming steps such as distillation separation to purify the product, and only needs to filter to separate the catalyst, so that the catalyst can be recycled and reused, the process is simple and easy to operate, and it is economical and environmentally friendly. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with specific implementation modes.

[0030] The synthesis method of N-tert-butyl diethanolamine provided by the present invention comprises the following steps:

[0031] S1. Put the catalyst and the auxiliary agent into a dry reactor, replace the nitrogen 2 to 3 times, then pump tert-butylamine into the reactor under negative pressure, start stirring and heat the temperature in the reactor to 50 to 130° C.; wherein the catalyst is a carbon-supported weak acid metal salt catalyst; and the auxiliary agent is a weak acid;

[0032] S2. Keep the temperature in the kettle unchanged and slowly add ethylene oxide to the kettle until the pressure is maintained at 0.3-0.8 MPa to perform a preliminary reaction; when the pressure drops, continue to add ethylene oxide to maintain the pressure at 0.3-0.8 MPa;

[0033] S3. When the pressure in the kettle drops rapidly and the reaction temperature rises significantly, it indicates that the reaction is activated. Turn on the cooling water and control the reaction temperature to 50-130°C until the reaction is stable.

[0034] S4, controlling the reaction temperature to remain unchanged, slowly adding ethylene oxide dropwise to react, and aging after the addition is completed until the pressure remains substantially unchanged and the reaction is completed;

[0035] S5. Keep the temperature constant and degas until the pressure reaches -0.098 MPa, then continue degassing for 30 minutes, lower the temperature to below 60°C, filter, and the filtrate obtained is the product N-tert-butyl diethanolamine; the filtered catalyst can be reused after treatment.

[0036] In the above-mentioned synthesis method, the weak acid metal salt in the carbon-supported weak acid metal salt catalyst in step S1 is a weak acid transition metal salt, wherein the transition metal is one or more of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, preferably one or more of Cr, Ni, and Zn; the weak acid radical ion in the weak acid transition metal salt is CH3COO-, CN-, F-, SO3 2- 、SiO3 2- One or more of, preferably CH3COO-, SO3 2- 、SiO3 2- Specifically, the metal salt loading in the carbon-supported weak acid metal salt catalyst is 10-40% of the total mass of the carbon-supported weak acid metal salt catalyst, preferably 15-30%. The amount of the carbon-supported weak acid metal salt catalyst added is 0.15-4% of the mass of tert-butylamine, preferably 0.3-3%.

[0037] In step S1, the auxiliary agent is one or more of CH3COOH, C2H5COOH, H2SiO4, HCN, HF, H2SO3, C6H5COOH, CH2=CHCOOH, preferably one or more of CH3COOH, C6H5COOH, H2SiO3. The amount of the auxiliary agent added is 1 to 50% of the mass of the carbon-supported weak acid metal salt catalyst, preferably 5 to 30%.

[0038] In step S4, the amount of ethylene oxide added is 1.5 to 2.5 times the molar number of tert-butylamine; preferably, the amount of ethylene oxide added is 1.8 to 2.2 times the molar number of tert-butylamine.

[0039] The preparation method of the carbon-supported weak acid metal salt catalyst adopts the absorption and impregnation method, and the activated carbon adopts the activated carbon that meets the standard ZBB13001-88. A 20% concentration of metal salt solution is prepared, and the ratio of the impregnation solution to the activated carbon is 5:1, and the temperature is between 50 and 60°C. The catalyst is prepared in a rotary evaporator, and after impregnation for 120 minutes, the product can be obtained by suction filtration and vacuum drying.

[0040] Example 1

[0041] A method for synthesizing N-tert-butyl diethanolamine, the synthesis steps of which are as follows:

[0042] S1. Add 7.3 g of carbon-supported (CH3COO)2Zn catalyst with a metal salt loading of 20% and 1 g of auxiliary H2SiO3 liquid into a 2.5 L dry reactor. After replacing nitrogen twice, 730 g of tert-butylamine is pumped into the reactor by negative pressure; start stirring and heat the reactor to between 90 and 95°C.

[0043] S2. Slowly add ethylene oxide dropwise until the pressure is maintained in the range of 0.4 to 0.45 MPa for preliminary reaction. When the pressure drops, additional ethylene oxide is added dropwise to the above pressure range.

[0044] S3. When the pressure in the kettle drops rapidly and the reaction temperature rises significantly, it indicates that the reaction is activated. Turn on the cooling water and adjust the reaction temperature to between 90 and 95°C.

[0045] S4, after the reaction is stable, slowly add ethylene oxide dropwise to react. When the amount of ethylene oxide added is 880 g, stop adding ethylene oxide dropwise and carry out aging. When the pressure remains substantially unchanged, the reaction aging is completed.

[0046] S5. Keep the temperature constant and degas. After the pressure reaches -0.098Mpa, degas for another 30 minutes. Lower the temperature to below 60°C and filter. The filtered solution is the final product.

[0047] Example 2

[0048] The difference between this embodiment and embodiment 1 is that: carbon-supported (CH3COO)2Zn with a metal salt loading of 35% is used as the catalyst, the catalyst addition amount remains unchanged, and the reaction temperature is 55-60° C. The other conditions are exactly the same as those in embodiment 1.

[0049] Example 3

[0050] The difference between this embodiment and embodiment 1 is that: the amount of carbon-supported (CH3COO)2Zn catalyst with a metal salt loading of 20% is 25g; the pressure during the pre-reaction is 0.6-0.65Mpa. The other conditions are exactly the same as those in embodiment 1.

[0051] Example 4

[0052] The difference between this embodiment and embodiment 1 is that the amount of the auxiliary agent H2SiO3 liquid added is 2.5 g, and the amount of ethylene oxide added dropwise in step S4 is 700 g. Other conditions are exactly the same as those in embodiment 1.

[0053] Example 5

[0054] The difference between this embodiment and embodiment 1 is that the reaction temperature of step S3 is 120-125° C., the auxiliary agent is CH3COOH, and the amount used is 1 g. The other conditions are exactly the same as those of embodiment 1.

[0055] Example 6

[0056] The difference between this embodiment and embodiment 1 is that 7.3 g of carbon-supported Ni2SO3 catalyst with a metal salt loading of 20% is used, and the pressure of the preliminary reaction in step S2 is 0.5-0.55 MPa. Other conditions are exactly the same as those in embodiment 1.

[0057] Example 7

[0058] The difference between this embodiment and embodiment 1 is that the amount of ethylene oxide added in step S4 is 1000 g. Other conditions are exactly the same as those in embodiment 1.

[0059] Example 8

[0060] The difference between this embodiment and embodiment 1 is that 25 g of carbon-supported CrCN3 catalyst with a metal loading of 10% is added in step S1. Other conditions are exactly the same as those in embodiment 1.

[0061] Example 9

[0062] The difference between this embodiment and embodiment 1 is that the auxiliary agent added in step S1 is a combined acid formed by mixing CH2=CHCOOH and C6H5COOH in a weight ratio of 1:1, and the reaction temperature in step S3 is 70-75° C. Other conditions are exactly the same as those in embodiment 1.

[0063] Example 10

[0064] The difference between this embodiment and embodiment 1 is that: 7.3 g of carbon-supported CuSiO3 catalyst with a metal salt loading of 20% is added in step S1, and the amount of ethylene oxide added in step S4 is 871 g. Other conditions are exactly the same as those in embodiment 1.

[0065] Comparative Example 1

[0066] A method for synthesizing N-tert-butyl diethanolamine, the synthesis steps of which are as follows:

[0067] S1. Add 7.3 g of carbon-supported (CH3COO)2Zn catalyst with a metal loading of 20% into a 2.5 L dry reactor, replace nitrogen twice, and then pump 730 g of tert-butylamine into the reactor. Start stirring and heat the reactor to between 90 and 95°C.

[0068] S2. Slowly add ethylene oxide dropwise until the pressure is maintained in the range of 0.4 to 0.45 MPa for preliminary reaction. When the pressure drops, additional ethylene oxide is added dropwise to the above pressure range.

[0069] S3. When the pressure in the kettle drops rapidly and the reaction temperature rises significantly, it means that the reaction is activated. Turn on the cooling water and adjust the reaction temperature to between 90 and 95°C.

[0070] S4, after the reaction is stable, slowly add ethylene oxide dropwise to react. When the amount of ethylene oxide added is 880 g, stop adding ethylene oxide dropwise and carry out aging. When the pressure remains substantially unchanged, the reaction aging is completed.

[0071] S5. Keep the temperature constant and degas. After the pressure reaches -0.098Mpa, degas for another 30 minutes. Lower the temperature to below 60°C and filter. The filtered solution is the final product.

[0072] Comparative Example 2

[0073] A method for synthesizing N-tert-butyl diethanolamine, the synthesis steps of which are as follows:

[0074] S1. Add 7.3 g of anhydrous (CH3COO)2Zn powder catalyst and 1 g of HSiO liquid additive into a 2.5 L dry reactor. After replacing nitrogen twice, pump 730 g of tert-butylamine into the reactor. Start stirring and heat the reactor to between 90-95°C.

[0075] S2. Slowly add ethylene oxide dropwise until the pressure is maintained in the range of 0.4 to 0.45 MPa for preliminary reaction. When the pressure drops, additional ethylene oxide is added dropwise to the above pressure range.

[0076] S3. When the pressure in the kettle drops rapidly and the reaction temperature rises significantly, it means that the reaction is activated. Turn on the cooling water and adjust the reaction temperature to between 90 and 95°C.

[0077] S4, after the reaction is stable, slowly add ethylene oxide dropwise to react. When the amount of ethylene oxide added is 880 g, stop adding ethylene oxide dropwise and carry out aging. When the pressure remains substantially unchanged, the reaction aging is completed.

[0078] S5. Keep the temperature constant and degas. After the pressure reaches -0.098Mpa, degas for another 30 minutes. Lower the temperature to below 60°C and filter. The filtered solution is the final product.

[0079] Comparative Example 3

[0080] A method for synthesizing N-tert-butyl diethanolamine, the synthesis steps of which are as follows:

[0081] S1. Add 7.3 g of KOH catalyst into a 2.5 L dry reactor, replace nitrogen twice, and then pump 730 g of tert-butylamine into the reactor. Start stirring and heat the reactor to between 90-95°C.

[0082] S2. Slowly add ethylene oxide dropwise until the pressure is maintained in the range of 0.4-0.45 MPa for preliminary reaction. When the pressure drops, add more ethylene oxide dropwise to the above pressure range.

[0083] S3. When the pressure in the kettle drops rapidly and the reaction temperature rises significantly, it means that the reaction is activated. Turn on the cooling water and adjust the reaction temperature to between 90 and 95°C.

[0084] S4, after the reaction is stable, slowly add ethylene oxide dropwise to react. When the amount of ethylene oxide added is 880 g, stop adding ethylene oxide dropwise and carry out aging. When the pressure remains substantially unchanged, the reaction aging is completed.

[0085] S5. Keep the temperature constant and degas. After the pressure reaches -0.098Mpa, degas for another 30 minutes. Lower the temperature to below 60°C and filter. The filtered solution is the final product.

[0086] Comparative Example 4

[0087] A method for synthesizing N-tert-butyl diethanolamine, the synthesis steps of which are as follows:

[0088] S1. Add 7.3g KOH catalyst and 1g H2SiO3 liquid as auxiliary agent into a 2.5L dry reactor, replace nitrogen twice, and then pump 730g tert-butylamine into the reactor. Start stirring and heat the reactor to between 90-95°C.

[0089] S2. Slowly add ethylene oxide dropwise until the pressure is maintained in the range of 0.4 to 0.45 MPa for preliminary reaction. When the pressure drops, additional ethylene oxide is added dropwise to the above pressure range.

[0090] S3. When the pressure in the kettle drops rapidly and the reaction temperature rises significantly, it means that the reaction is activated. Turn on the cooling water and adjust the reaction temperature to between 90 and 95°C.

[0091] S4, after the reaction is stable, slowly add ethylene oxide dropwise to react. When the amount of ethylene oxide added is 880 g, stop adding ethylene oxide dropwise and carry out aging. When the pressure remains substantially unchanged, the reaction aging is completed.

[0092] S5. Keep the temperature constant and degas. After the pressure reaches -0.098Mpa, degas for another 30 minutes. Lower the temperature to below 60°C and filter. The filtered solution is the final product.

[0093] Product performance comparison:

[0094] The components of the products obtained in Examples 1 to 10 and Comparative Examples 1 to 4 were measured, and the results are shown in Table 1.

[0095] Table 1 Analysis of liquid components in products obtained from Examples 1 to 10 and Comparative Examples 1 to 4

[0096]

[0097]

[0098] From the data in Table 1, it can be found that the content of N-tert-butyldiethanolamine in the products obtained in Example 1 and Example 7 is very high, while the content of N-tert-butylethanolamine and by-product HETBA is very low. The content of N-tert-butylethanolamine is low, indicating that the reaction is more thorough; at the same time, even if too much ethylene oxide is added in Example 7, the content of by-product HETBA does not increase significantly, indicating that the synthesis method of the present invention can effectively prevent overreaction. Compared with Example 1, the content of by-product HETBA in the product obtained in Comparative Example 1 is significantly increased, which shows that the present invention can enhance the reaction activity, react thoroughly, reduce the content of N-tert-butylethanolamine, and effectively prevent overreaction, and avoid the product TBA and ethylene oxide from reacting further to form by-product HETBA. Compared with Example 1, the content of N-tert-butylethanolamine and the by-product HETBA in the product prepared in Comparative Example 2 is high. This is because the common catalyst has low activity and cannot play a synergistic role with the auxiliary agent, and cannot adjust the acidity and alkalinity of the reaction environment, resulting in incomplete reaction of some N-tert-butylethanolamine, or causing the reaction to proceed further and produce side reactions. Compared with Example 1, the content of N-tert-butylethanolamine and the by-product HETBA in Comparative Examples 3 to 4 is relatively high, indicating that the use of conventional catalysts alone or in combination with weak acid auxiliary agents under the same synthesis process can neither synergistically control the reaction process nor have a good catalytic effect.

[0099] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A method for synthesizing N-tert-butyl diethanolamine, characterized in that: The following steps are involved: S1. Put the catalyst and the auxiliary agent into a dry reactor, replace the nitrogen, and then pump tert-butylamine into the reactor under negative pressure, start stirring, and heat the temperature in the reactor to 50-130° C.; the catalyst is a carbon-supported weak acid metal salt catalyst; and the auxiliary agent is a weak acid; S2. Keep the temperature in the kettle unchanged and slowly add ethylene oxide into the kettle until the pressure is maintained at 0.3-0.8Mpa to carry out a preliminary reaction; S3. When the pressure in the kettle drops rapidly and the reaction temperature rises significantly, the reaction is activated, the cooling water is turned on, and the reaction temperature is controlled to be 50-130°C until the reaction is stable; S4, controlling the reaction temperature to remain unchanged, slowly adding ethylene oxide dropwise to react, and aging after the addition is completed until the pressure remains substantially unchanged and the reaction is completed; S5. Keep the temperature constant, degas, cool down, and filter the filtrate to obtain N-tert-butyl diethanolamine.

2. The method for synthesizing N-tert-butyl diethanolamine according to claim 1, characterized in that: The weak acid metal salt in the carbon-supported weak acid metal salt catalyst in step S1 is a weak acid transition metal salt, wherein the transition metal is one or more of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn; the weak acid radical ion in the weak acid transition metal salt is CH3COO-, CN-, F-, SO3 2- 、SiO3 2- One or more of .

3. The method for synthesizing N-tert-butyldiethanolamine according to claim 2, characterized in that: The transition metal is one or more of Cr, Ni, and Zn; the weak acid radical ions in the weak acid transition metal salt are CH3COO-, SO3 2- 、SiO3 2- One or more of.

4. The method for synthesizing N-tert-butyldiethanolamine according to claim 1 or 2, characterized in that: The auxiliary agent in step S1 is one or more of CH3COOH, C2H5COOH, H2SiO3, HCN, HF, H2SO3, C6H5COOH, and CH2=CHCOOH.

5. The method for synthesizing N-tert-butyldiethanolamine according to claim 1 or 2, characterized in that: The metal salt loading in the carbon-supported weak acid metal salt catalyst in step S1 is 10-40% of the total mass of the carbon-supported weak acid metal salt catalyst.

6. The method for synthesizing N-tert-butyldiethanolamine according to claim 1 or 2, characterized in that: In step S1, the amount of the carbon-supported weak acid metal salt catalyst added is 0.15-4% of the mass of tert-butylamine, preferably 0.3-3%; the amount of the auxiliary agent added is 1-50% of the mass of the carbon-supported weak acid metal salt catalyst, preferably 5-30%.

7. The method for synthesizing N-tert-butyldiethanolamine according to claim 1 or 2, characterized in that: In step S2, when the pressure drops, ethylene oxide is continuously added dropwise to maintain the pressure within the range of 0.3 to 0.8 MPa.

8. The method for synthesizing N-tert-butyldiethanolamine according to claim 1 or 2, characterized in that: The reaction temperature in step S3 is 50-130°C.

9. The method for synthesizing N-tert-butyldiethanolamine according to claim 1 or 2, characterized in that: In step S4, the amount of ethylene oxide added is 1.5 to 2.5 times the molar number of tert-butylamine; preferably, the amount of ethylene oxide added is 1.8 to 2.2 times the molar number of tert-butylamine.

10. The method for synthesizing N-tert-butyldiethanolamine according to claim 1 or 2, characterized in that: In step S5, the degassing is continued for 30 minutes after the pressure is degassed to -0.098 MPa, and the temperature is lowered to below 60° C. before filtering.

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