Method for preparing beta-alkoxy-N, N-dimethyl propionamide

Abstract

The invention discloses a method for preparing beta-alkoxy-N, N-dimethyl propionamide, which comprises the following steps: preparing beta-alkoxy propionate in a fixed bed reactor by using acrylate, fatty alcohol and a catalyst, the catalyst comprising more than one of organic tin, imine salt and tetrafluoroborate; introducing the reaction liquid obtained in the previous step and dimethylamine into a fixed bed reactor for reaction; the reaction liquid obtained in the previous step is subjected to atmospheric distillation, dimethylamine recovery, aliphatic alcohol recovery and reduced pressure distillation, beta-alkoxy-N, N-dimethyl propionamide is obtained, and distillation residual liquid replaces a catalyst to be recycled. According to the method, continuous production of the fixed bed is combined with at least one catalyst of organic tin, imine salt and tetrafluoroborate, the two catalysts have a synergistic effect, the catalyst can be recycled, selectivity and conversion rate are not obviously reduced after multiple reactions, and the method has the characteristics of fast reaction, high yield, high purity and the like, and can be used for continuous and large-scale industrial production.

Description

Technical Field

[0001] The invention belongs to the field of preparation of beta-alkoxy-N,N-dimethylpropionamide, and specifically relates to a method for preparing beta-alkoxy-N,N-dimethylpropionamide. Background Art

[0002] NMP, the full name of N-methylpyrrolidone, is an important basic chemical raw material and an important raw material for the new energy industry. It has the characteristics of high boiling point, strong polarity, low viscosity, strong solubility, non-corrosive, low volatility, non-flammable, good chemical and thermal stability, degradable, and recyclable. It is easily soluble in water, ethanol, acetone, ethyl acetate, chloroform and benzene, and can dissolve most organic and inorganic compounds, polar gases, natural and synthetic polymer compounds. At present, China's NMP is mainly used in the lithium battery industry. China's NMP consumption in the lithium battery industry accounts for more than 80%. It is also used in small quantities in polymer materials, electronics, and pharmaceutical industries, but not as much as the application ratio in the lithium battery industry. In the lithium battery industry, it is mainly used as a front-end solvent for lithium batteries and is a supporting solvent for lithium battery positive electrode binders. In recent years, with the rapid development of the lithium battery industry, China's lithium battery consumption has increased significantly, driving the consumption explosion of lithium battery-related industries, and also driving the consumption growth of China's NMP in the lithium battery industry. In addition, NMP can also be used in the electronics industry, high-resolution materials, and pharmaceutical industries, which are all relatively hot industries in China. Among them, NMP is an essential chemical solvent for chemical reactions and dilutions in the manufacturing process of polymer materials such as aramid, polyphenylene sulfide, and polyimide. However, since NMP solvent is considered by the European Union to be harmful to the human body, has reproductive toxicity, and is irritating and allergic to the skin, its use is restricted in some countries. Therefore, it is necessary to develop a non-toxic solvent to replace NMP. Considering the boiling point and solubility, β-alkoxypropionamides are also superior to NMP in performance, and are highly expected in the above fields.

[0003] Patent applications CN104203905A, CN102245561A, and CN101616889A use a method in which β-alkoxypropionic acid esters are subjected to amidation reaction in the presence of polyols and alkaline catalysts, and then the alkaline catalysts are neutralized. The reaction residue obtained by distilling and removing the product is not discarded, but directly recovered to replace the polyol for re-reaction. The above method is an intermittent reaction. Since the alkaline catalysts used in the above method are mostly alkali metal alcoholates such as sodium methoxide, sodium ethoxide, and sodium tert-butoxide, it is necessary to neutralize such alkaline catalysts when separating and purifying the product. If the alkaline catalyst is not neutralized and distillation separation and purification are performed, the product will decompose. Therefore, the catalyst in the preparation of β-alkoxypropionamides using the above method cannot be recycled after neutralization, and can only be subjected to batch reactions in kettles, which makes it difficult to form large-scale production. Furthermore, intermittent reactions have many by-products and low selectivity. Currently, they are mainly concentrated in small-scale and pilot tests with low efficiency. There is no large-scale continuous mass production. In order to neutralize the solid waste salt and wastewater produced by the catalyst, each batch of materials needs to be filtered to remove the salt, and the process steps are complicated. Summary of the invention

[0004] In order to solve the above problems, the object of the present invention is to provide a method for preparing β-alkoxy-N,N-dimethylpropionamide.

[0005] The present invention provides a method for preparing β-alkoxy-N,N-dimethylpropionamide, comprising the following steps:

[0006] S1: preparing β-alkoxypropionate in a fixed bed reactor using acrylate, fatty alcohol and a catalyst, wherein the catalyst comprises one or more of an organic tin, an imine salt and a tetrafluoroborate;

[0007] S2: introducing the reaction solution obtained in step S1 and dimethylamine into a fixed bed reactor for reaction;

[0008] S3: distilling the reaction liquid obtained in step S2 under normal pressure, recovering and storing the dimethylamine, recycling the aliphatic alcohol, and then distilling under reduced pressure to obtain the β-alkoxy-N,N-dimethylpropionamide, and recycling the distillation residue to replace the catalyst.

[0009] The invention discloses a method for preparing β-alkoxy-N,N-dimethylpropionamide. On the one hand, at least one of organic tin, imine salt and tetrafluoroborate is used as a catalyst. The catalyst has high selectivity and is used in both the Michael addition reaction in step S1 and the amidation reaction in step S2, without adding other catalysts. Furthermore, after the amidation is completed, dimethylamine and fatty alcohol are distilled out at normal pressure for recycling, and the product β-alkoxy-N,N-dimethylpropionamide is obtained by reduced pressure distillation. The catalyst in the distillation residue liquid does not need to be purified by distillation purification, but the distillation residue liquid is directly used to replace the catalyst for continuous recycling. This is because the organic tin, imine salt and tetrafluoroborate catalysts used in the invention have weak alkalinity and strong nucleophilicity, are not decomposed when heated and meet water (the raw material contains trace water, and the water content is about 1000ppm), have high distillation stability and low reverse reaction, and the reaction liquid after amidation can be directly distilled to obtain the product β-alkoxy-N,N-dimethylpropionamide, thereby simplifying the process steps and reducing the generation of solid waste. Since commonly used alkali metal alkoxides are highly alkaline and have poor stability, non-neutralization during distillation will cause a large amount of products to undergo reverse reactions, resulting in product decomposition. Furthermore, alkali metal alkoxides will be hydrolyzed and deactivated when in contact with water, resulting in poor selectivity. Therefore, alkali metal alkoxides cannot be recycled when used as catalysts. On the other hand, the present invention can be continuously and uninterruptedly produced using a fixed bed, with high selectivity, few by-products, high production efficiency, and large-scale production. The present invention combines the above-mentioned catalyst through continuous production of a fixed bed, and the two act synergistically to improve the selectivity of the product, while further realizing the reuse of the catalyst, simplifying the process flow, and continuously and efficiently producing high-purity β-alkoxy-N, N-dimethylpropionamide on a large scale.

[0010] Preferably, the chemical reaction formula of the method for preparing high-purity β-alkoxy-N,N-dimethylpropionamide is as follows:

[0011]

[0012] Wherein, R1 includes methyl, ethyl or n-butyl.

[0013] This scheme stipulates that the R1 group in the fatty alcohol and the acrylate is the same, and after the amidation reaction occurs in reaction ②, an alcohol identical to the raw fatty alcohol is generated, and the generated alcohol enters the cycle as a raw material to participate in the reaction, which not only reduces the amount of fatty alcohol raw material, but also avoids the generation of other types of alcohols, thereby improving the yield of the product in the continuous preparation method.

[0014] In the conventional method, the reaction in step S1 needs distillation to make the purity of β-alkoxypropionate reach above 99.9% before starting the reaction in step S2. The present invention directly omits this step, and the β-alkoxypropionate can be used directly without distillation purification.

[0015] Preferably, in step S1, the fatty alcohol includes one or more of methanol, ethanol and n-butanol.

[0016] Preferably, in step S1, the mass of the catalyst is 0.1%-1% of the mass of the acrylate.

[0017] Preferably, in step S1, the organic tin comprises at least one of dibutyltin oxide (CAS No.: 818-08-6) and dibutyltin dilaurate (CAS No.: 77-58-7).

[0018] Preferably, in step S1, the imide salt includes one or more of tri-n-butylmethylammonium bis(trifluoromethanesulfonyl)imide salt (CAS No.: 405514-94-5) and 1-butyl-2,3-methylimidazole bis(ketone)imide (CAS No.: 350493-08-2).

[0019] Preferably, in step S1, the tetrafluoroborate includes one or more of N,N-diethyl-2-methoxy-N-methylethylammonium tetrafluoroborate (CAS No.: 464927-72-8) and 1-butyl-2,3-dimethylimidazolium tetrafluoroborate (CAS No.: 402846-78-0).

[0020] Preferably, in step S1, the molar ratio of the acrylic acid ester to the aliphatic alcohol is 1:(1.2-6). When the molar ratio of the acrylic acid ester to the aliphatic alcohol is within this range, the aliphatic alcohol is in excess, so that the reaction in step S1 is sufficient, and the excess aliphatic alcohol in the reaction in step S1 can act as a solvent in the reaction in step S2, thereby improving the conversion rate and selectivity, and the aliphatic alcohol can be recovered after the amidation reaction is completed.

[0021] Preferably, in step S1, the temperature for preparing the β-alkoxypropionate is 30-60°C and the time is 120s-360s.

[0022] Preferably, in step S2, the molar ratio of the β-alkoxypropionic acid ester in the reaction solution of step S1 to the dimethylamine is 1:(1-1.5).

[0023] Preferably, in step S2, the reaction temperature is 50-100°C.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention combines a catalyst (at least one of an organic tin, an imide salt, and a tetrafluoroborate) through continuous production of a fixed bed, and the two act synergistically, the catalyst does not need to be neutralized and discarded, and can be repeatedly recycled, and the selectivity and conversion rate are not significantly reduced after multiple reactions. At the same time, the present invention has the characteristics of fast reaction speed, short reaction time, high yield and purity, etc., can be continuous, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a process flow chart for preparing high-purity 3-methoxy-N,N-dimethylpropionamide.

[0026] Figure 2 This is a diagram of the device for preparing high-purity 3-methoxy-N,N-dimethylpropionamide according to the present invention.

[0027] Figure 3 This is the GC-MS graph of 3-methoxy-N,N-dimethylpropionamide prepared by using the catalyst in Example 1 of the present invention for the first time. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention and the drawings in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0029] Example 1

[0030] Figure 1 The process flow chart of preparing high-purity 3-methoxy-N,N-dimethylpropionamide according to the present invention is shown in FIG. Figure 1 The process flow in the preparation of 3-methoxy-N, N-dimethylpropionamide. The following examples 2-6 are also based on Figure 1 The process flow is to prepare the corresponding β-alkoxy-N,N-dimethylpropionamide.

[0031] Figure 2 The device diagram for preparing high-purity 3-methoxy-N,N-dimethylpropionamide of the present invention includes a material kettle 1 (for dissolving raw material alcohol and catalyst), an acrylate raw material kettle 2, a dimethylamine tank 3, a fixed bed reactor 4, a fixed bed reactor 5, a distillation kettle 6, a rectification tower 7, a condenser 8, a condenser 9, a gas-liquid separator 10 (for separating excess dimethylamine and produced alcohol), a finished product tank 11, and a dimethylamine recovery storage tank 12. This embodiment 1 adopts Figure 2 The apparatus shown in the figure is used to prepare 3-methoxy-N,N-dimethylpropionamide. The following Examples 2-6 are also prepared according to Figure 2 The apparatus shown prepares the corresponding β-alkoxy-N,N-dimethylpropionamide.

[0032] S1: 2381 g (74.31 mol) of methanol and 4.8 g of dibutyltin oxide were added to a material kettle and mixed and dissolved uniformly, and then introduced into a fixed bed reactor with 1600 g (18.585 mol) of methyl acrylate by metering pumps. The reaction temperature was 50° C. and the flow rate was adjusted so that the reaction time was controlled at 120 s.

[0033] S2: The reaction liquid of step S1 and 1004 g (22.27 mol) of dimethylamine were introduced into a fixed bed reactor by metering pumps respectively. The reaction temperature was 60° C. and the flow rate was adjusted so that the reaction time was controlled at 240 s.

[0034] S3: Distillation: The reaction liquid of step S2 is transferred to a still for atmospheric distillation. The dimethylamine is compressed, recovered and stored, and methanol is pumped in for recycling. Then, it is distilled under reduced pressure to obtain 2322 g (17.701 mol) of the product 3-methoxy-N,N-dimethylpropionamide with a yield of 95.3% and a purity of 99.97%. The catalyst in the residual liquid at the bottom of the still is recycled.

[0035] S4: The residual liquid at the bottom of the distillation kettle in step S3 was used to replace 4.8 g of dibutyltin oxide in step S1, and steps S1-S3 were repeated 10 times. Then, 2297 g (17.51 ​​mol) of the product 3-methoxy-N,N-dimethylpropionamide was obtained by distillation under reduced pressure with a yield of 94.2% and a purity of 99.97%.

[0036] Figure 3 This is the GC-MS chart of 3-methoxy-N,N-dimethylpropionamide prepared by using the catalyst of Example 1 of the present invention for the first time. Figure 3 It can be seen that the 3-methoxy-N,N-dimethylpropionamide prepared in Example 1 is successfully prepared, and the purity of the prepared 3-methoxy-N,N-dimethylpropionamide is 99.97%.

[0037] Example 2

[0038] S1: 2841 g (88.66 mol) of methanol and 14.8 g of tri-n-butylmethylammonium bis(trifluoromethanesulfonyl)imide salt were added to a material kettle and mixed and dissolved evenly, and then introduced into a fixed bed reactor with 1273 g (14.787 mol) of methyl acrylate by metering pumps. The reaction temperature was 45° C. and the flow rate was adjusted so that the reaction time was controlled at 120 s.

[0039] S2: The reaction liquid of step S1 and 866 g (19.21 mol) of dimethylamine were introduced into a fixed bed reactor by metering pumps respectively. The reaction temperature was 90° C. and the flow rate was adjusted so that the reaction time was controlled at 120 s.

[0040] S3: Distillation: The reaction liquid of step S2 is transferred to a still for atmospheric distillation. The dimethylamine is compressed, recovered and stored, and methanol is pumped in for recycling. Then, the product 3-methoxy-N,N-dimethylpropionamide (1857 g (14.16 mol)) is obtained by vacuum distillation with a yield of 95.8% and a purity of 99.99%. The catalyst in the residual liquid at the bottom of the still is recycled.

[0041] S4: The residual liquid at the bottom of the distillation kettle in step S3 was used to replace 14.8 g of tri-n-butylmethylammonium bis(trifluoromethanesulfonyl)imide salt in step S1, and steps S1-S3 were repeated 10 times, and then vacuum distillation was performed to obtain 1818 g (13.85 mol) of the product 3-methoxy-N,N-dimethylpropionamide with a yield of 93.7% and a purity of 99.98%.

[0042] Example 3

[0043] S1: 2250 g (48.84 mol) of ethanol and 6.2 g of N,N-diethyl-2-methoxy-N-methylethylammonium tetrafluoroborate were added to a material kettle and mixed and dissolved evenly. Then, they were introduced into a fixed bed reactor with 1630 g (16.28 mol) of ethyl acrylate by metering pumps. The reaction temperature was 60° C. and the flow rate was adjusted so that the reaction time was controlled at 240 s.

[0044] S2: The reaction solution of step S1 and 1100 g (24.34 mol) of dimethylamine were introduced into a fixed bed reactor by metering pumps respectively. The reaction temperature was 60° C. and the flow rate was adjusted so that the reaction time was controlled at 240 s.

[0045] S3: Distillation: The reaction liquid from step S2 is transferred to a still for atmospheric distillation. The dimethylamine is compressed, recovered and stored, and methanol is pumped in for recycling. Then, it is subjected to reduced pressure distillation to obtain 2203 g (15.17 mol) of the product 3-ethoxy-N,N-dimethylpropionamide with a yield of 93.1% and a purity of 99.93%. The catalyst in the residual liquid at the bottom of the still is recycled.

[0046] S4: The residual liquid at the bottom of the distillation kettle in step S3 was used to replace 6.2 g of N,N-diethyl-2-methoxy-N-methylethylammonium tetrafluoroborate in step S1, and steps S1-S3 were repeated 10 times, followed by reduced pressure distillation to obtain 2186 g (15.059 mol) of the product 3-ethoxy-N,N-dimethylpropionamide with a yield of 92.5% and a purity of 99.93%.

[0047] Example 4

[0048] S1: 2387 g (51.81 mol) of ethanol and 4.5 g of dibutyltin oxide were added to a material kettle and mixed and dissolved evenly. Then, the mixture and 1730 g (17.23 mol) of ethyl acrylate were introduced into a fixed bed reactor by metering pumps. The reaction temperature was 30° C. The flow rate was adjusted so that the reaction time was controlled at 240 s.

[0049] S2: The reaction liquid from step S1 and 856 g (18.99 mol) of dimethylamine were introduced into a fixed bed reactor by metering pumps respectively. The reaction temperature was 70° C. and the flow rate was adjusted so that the reaction time was controlled at 120 s.

[0050] S3: Distillation: The reaction liquid of step S2 is transferred to a still for atmospheric distillation. The dimethylamine is compressed, recovered and stored, and methanol is pumped in for recycling. Then, it is subjected to reduced pressure distillation to obtain 2311 g (15.92 mol) of the product 3-ethoxy-N,N-dimethylpropionamide with a yield of 92.0% and a purity of 99.92%. The catalyst in the residual liquid at the bottom of the still is recycled.

[0051] S4: The residual liquid at the bottom of the distillation kettle in step S3 was recycled to replace 4.5 g of dibutyltin oxide in step S1, and steps S1-S3 were repeated 10 times, and then vacuum distillation was performed to obtain 2278 g (15.7 mol) of the product 3-ethoxy-N,N-dimethylpropionamide with a yield of 91.2% and a purity of 99.92%.

[0052] Example 5

[0053] S1: 2235 g (30.15 mol) of n-butanol and 7.5 g of dibutyltin dilaurate were added to a material kettle and mixed and dissolved uniformly. Then, they were introduced into a fixed bed reactor with 1933 g (15.08 mol) of butyl acrylate by metering pumps. The reaction temperature was 40° C. and the flow rate was adjusted so that the reaction time was controlled at 360 s.

[0054] S2: The reaction liquid of step S1 and 815 g (18.08 mol) of dimethylamine were introduced into a fixed bed reactor by metering pumps respectively. The reaction temperature was 75° C. and the flow rate was adjusted so that the reaction time was controlled at 120 s.

[0055] S3: Distillation: The reaction liquid from step S2 is transferred to a still for atmospheric distillation. The dimethylamine is compressed, recovered and stored, and methanol is pumped in for recycling. Then, it is subjected to reduced pressure distillation to obtain 2516 g (14.52 mol) of the product 3-butoxy-N,N-dimethylpropionamide with a yield of 96.2% and a purity of 99.98%. The catalyst in the residual liquid at the bottom of the still is recycled.

[0056] S4: The residual liquid at the bottom of the distillation kettle in step S3 was recycled to replace 7.5 g of dibutyltin dilaurate in step S1, and steps S1-S3 were repeated 10 times, and then vacuum distillation was performed to obtain 2489 g (14.37 mol) of the product 3-butoxy-N,N-dimethylpropionamide with a yield of 95.3% and a purity of 99.97%.

[0057] Example 6

[0058] S1: 3138 g (42.34 mol) of n-butanol and 3.2 g of 1-butyl-2,3-dimethylimidazolium tetrafluoroborate were added to the material kettle and mixed and dissolved evenly. Then, they were introduced into the fixed bed reactor with 1357 g (10.59 mol) of butyl acrylate by metering pumps. The reaction temperature was 50°C and the flow rate was adjusted so that the reaction time was controlled at 120 s.

[0059] S2: The reaction liquid of step S1 and 572 g (12.69 mol) of dimethylamine were introduced into a fixed bed reactor by metering pumps respectively. The reaction temperature was 80° C. and the flow rate was adjusted so that the reaction time was controlled at 360 s.

[0060] S3: Distillation: The reaction liquid of step S2 is transferred to a still for atmospheric distillation. The dimethylamine is compressed, recovered and stored, and methanol is pumped in for recycling. Then, it is distilled under reduced pressure to obtain 1735 g (10.01 mol) of the product 3-butoxy-N,N-dimethylpropionamide with a yield of 94.5% and a purity of 99.99%. The catalyst in the residual liquid at the bottom of the still is recycled.

[0061] S4: The residual liquid at the bottom of the distillation kettle in step S3 was used to replace 3.2 g of 1-butyl-2,3-dimethylimidazolium tetrafluoroborate in step S1, and steps S1-S3 were repeated 10 times, and then vacuum distillation was performed to obtain 1698 g (9.8 mol) of the product 3-butoxy-N,N-dimethylpropionamide with a yield of 92.6% and a purity of 99.98%.

[0062] Comparative Example 1

[0063] 3-methoxypropionic acid methyl ester (0.6 mol), sodium methoxide (MeONa, 0.03 mol), glycerol (polyol, 0.6 mol) and dimethylamine (0.9 mol) were placed in a 300 mL autoclave and reacted at 60°C for 6 hours. After cooling, the autoclave was depressurized and the contents were taken out. A small amount of the contents was taken out, and the 3-methoxypropionic acid methyl ester as the raw material and the 3-methoxy-N,N-dimethylpropionic acid amide as the product were quantified by the internal standard method of gas chromatography (internal standard substance: NMP). From the quantitative results, the conversion rate of 3-methoxypropionic acid methyl ester was calculated to be 99%, the selectivity of 3-methoxypropionic acid methyl ester was 80%, and the yield was 79%. The contents of the autoclave after the reaction were transferred to a 300 mL beaker, and 0.016 mol of 98% concentrated sulfuric acid was added while stirring with a glass rod to neutralize the sodium methoxide as a catalyst and precipitate it as a white salt. Then, after removing the white salt by suction filtration, the mixture was concentrated by an evaporator. During heating, an oil bath kept at 100°C was used to carefully and slowly increase the degree of reduced pressure so that the contents did not boil over. When the pressure reached 2 mmHg, the concentration operation was completed to obtain 66.3 g of a yellowish brown reaction residue. In addition, the distilled liquid was analyzed by GC (gas chromatography) to confirm the excess amine, the alcohol as a by-product, and the target product.

[0064] The reaction conditions and results of Examples 1-6 are shown in Table 1 below:

[0065] Table 1

[0066]

[0067]

[0068] As can be seen from Table 1 and Comparative Example 1, the yields of β-alkoxy-N, N-dimethylpropionamide prepared for the first time by using at least one of organic tin, imine salt, and tetrafluoroborate as catalyst and fixed bed in Examples 1-6 of the present invention are all ≥92%, proving that the selectivity of the catalyst of the present invention is good. However, the yield of the product prepared by using sodium methoxide as catalyst in Comparative Example 1 of the prior art is only 79%. Furthermore, the catalyst of the present invention does not need to be neutralized and discarded, and can be repeatedly recycled and used, and can be used in combination with a fixed bed to achieve continuous preparation of β-alkoxy-N, N-dimethylpropionamide. The selectivity and conversion rate (≥91%) of the preparation method of Examples 1-6 are not significantly reduced after 10 reactions. At the same time, it has the characteristics of fast reaction speed, short reaction time, high yield and purity, etc., and can be continuous, suitable for large-scale industrial production.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention is described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the technical solutions of the present invention can be modified or equivalently replaced, but these modifications or replacements are all within the protection scope of the present invention.

Claims

1. A method for preparing β-alkoxy-N,N-dimethylpropionamide, characterized in that: The steps include: S1: preparing β-alkoxypropionate in a fixed bed reactor using acrylate, fatty alcohol and a catalyst, wherein the catalyst comprises one or more of an organic tin, an imine salt and a tetrafluoroborate; S2: introducing the reaction solution obtained in step S1 and dimethylamine into a fixed bed reactor for reaction; S3: distilling the reaction liquid obtained in step S2 under normal pressure, recovering and storing the dimethylamine, recycling the aliphatic alcohol, and then distilling under reduced pressure to obtain the β-alkoxy-N,N-dimethylpropionamide, and recycling the distillation residue to replace the catalyst.

2. A method for preparing β-alkoxy-N,N-dimethylpropionamide according to claim 1, characterized in that: In S1, the fatty alcohol includes one or more of methanol, ethanol and n-butanol.

3. A method for preparing β-alkoxy-N,N-dimethylpropionamide according to claim 1, characterized in that: In step S1, the mass of the catalyst is 0.1%-1% of the mass of the acrylate.

4. A method for preparing β-alkoxy-N,N-dimethylpropionamide according to claim 1, characterized in that: In step S1, the organic tin includes one or more of dibutyltin oxide and dibutyltin dilaurate.

5. A method for preparing β-alkoxy-N,N-dimethylpropionamide according to claim 1, characterized in that: In step S1, the imide salt includes one or more of tri-n-butylmethylammonium bis(trifluoromethanesulfonyl)imide salt and 1-butyl-2,3-methylimidazole bis(ketone)imide.

6. A method for preparing β-alkoxy-N,N-dimethylpropionamide according to claim 1, characterized in that: In step S1, the tetrafluoroborate includes one or more of N,N-diethyl-2-methoxy-N-methylethylammonium tetrafluoroborate and 1-butyl-2,3-dimethylimidazolium tetrafluoroborate.

7. A method for preparing β-alkoxy-N,N-dimethylpropionamide according to claim 1, characterized in that: In S1, the molar ratio of the acrylic acid ester to the aliphatic alcohol is 1:(1.2-6).

8. A method for preparing β-alkoxy-N,N-dimethylpropionamide according to claim 1, characterized in that: In S1, the temperature for preparing the β-alkoxy propionate is 30-60°C and the time is 120s-360s.

9. A method for preparing β-alkoxy-N,N-dimethylpropionamide according to claim 1, characterized in that: In step S2, the molar ratio of the β-alkoxypropionic acid ester in the reaction solution of step S1 to the dimethylamine is 1:(1-1.5).

10. A method for preparing β-alkoxy-N,N-dimethylpropionamide according to any one of claims 1 to 9, characterized in that: In step S2, the reaction temperature is 50-100°C.

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