Purification method for 3-methoxy-n,n-dimethylpropionamide

Abstract

The present invention discloses a purification method for 3-methoxy-N,N-dimethylpropionamide. The purification method comprises the following steps: sequentially performing the steps of adsorption, polymerization, nanofiltration and rectification on a crude product of 3-methoxy-N,N-dimethylpropionamide, so as to obtain purified 3-methoxy-N,N-dimethylpropionamide, wherein the polymerization step is to add an initiator to 3-methoxy-N,N-dimethylpropionamide having undergone adsorption and then perform polymerization at a set temperature, and after the polymerization reaction is completed, the nanofiltration step is started. The purification method of the present invention is relatively simple and easy to realize industrialization. The purity of MMPA can be increased to 99.9% or higher, which meets the use standards for solvents used for electrolyte solutions and positive electrode materials of batteries, and therefore the application field of MMPA can be expanded. Moreover, the product is also used to replace the toxic product NMP, is environmentally friendly, and is of great strategic significance to the development of the battery industry.

Description

A method for purifying 3-methoxy-N,N-dimethylpropionamide Technical Field

[0001] The invention belongs to the technical field of chemical materials, and particularly relates to a method for purifying 3-methoxy-N,N-dimethylpropionamide. Background Art

[0002] 3-Methoxy-N,N-dimethylpropionamide (MMPA) is a colorless, transparent solvent containing both amide and alkyl groups. It is a high-boiling-point, highly polar, aprotic, colorless, transparent solvent. It can be mixed with a variety of solvents and can dissolve the polymer polyamide to a high degree. MMPA has strong solubility, high permeability, low viscosity, low volatility, non-corrosiveness, high fluidity, and low surface tension. It is also non-irritating to the skin, safe, and environmentally friendly. It can effectively replace the traditional solvent N-methylpyrrolidone and is widely used in industries such as electronics, pharmaceuticals, pesticides, pigments, cleaning agents, and insulation materials. In today's increasingly competitive safety solvent market, high volatility and low toxicity, in addition to solubility, have become important competitive advantages for solvents. Therefore, the product has a broad market prospect.

[0003] Currently, the purity of commercially available MMPA ranges from 97% to 98%. For example, the MMPA supplied by Myrel Reagents boasts a purity of 98%. While this purity satisfies applications in pesticides, pigments, and cleaning agents, specialized applications, such as battery electrolyte and cathode material solvents, require a purity of 99.9% or higher to ensure optimal battery performance. However, most current MMPA products fall short of these purity requirements, leading to the widespread use of toxic NMP as the primary solvent. While some patents report obtaining high-purity MMPA (>99.9%) through improved synthesis processes, high-purity products are not yet commercially available. This may be because these improved synthesis processes have only been tested in small batches and fail to meet the requirements upon scale-up. Alternatively, new synthesis processes may place higher demands on raw materials or equipment, resulting in significant investment costs. Currently, the goal of producing high-purity products is to further optimize the purification process, which can achieve superior results at lower costs. There is currently no report on the MMPA purification process, so further research on the MMPA purification process is very necessary for the preparation of high-purity MMPA. Summary of the Invention

[0004] In order to further improve the purity of 3-methoxy-N,N-dimethylpropionamide and broaden its application field, the present invention provides a method for purifying 3-methoxy-N,N-dimethylpropionamide.

[0005] A method for purifying 3-methoxy-N,N-dimethylpropionamide adopts the following technical scheme:

[0006] A method for purifying 3-methoxy-N,N-dimethylpropionamide comprises the following steps:

[0007] The crude 3-methoxy-N,N-dimethylpropionamide is subjected to adsorption, polymerization, nanofiltration and distillation steps in sequence to obtain purified 3-methoxy-N,N-dimethylpropionamide; wherein: in the polymerization step, an initiator is added to the adsorbed 3-methoxy-N,N-dimethylpropionamide, and then polymerization is carried out at a set temperature. After the polymerization reaction is completed, the process enters the nanofiltration step.

[0008] MMPA contains impurities such as N,N-dimethylpropionamide, which are difficult to separate and remove by distillation or filtration. The method of the present invention primarily involves adding an initiator to induce polymerization of these impurities, increasing their molecular weight. These impurities are then removed by nanofiltration, separating them from MMPA and improving the purity of MMPA.

[0009] Preferably, the adsorption step includes two processes: activated carbon adsorption and molecular sieve adsorption.

[0010] Further preferably, the specific steps of the molecular sieve adsorption are: the crude 3-methoxy-N,N-dimethylpropionamide is first subjected to activated carbon adsorption at a flow rate of 1 to 8 times the volume of activated carbon per hour, then passed through the molecular sieve at a flow rate of 1 to 8 times the volume of the molecular sieve per hour, and then enters the subsequent nanofiltration step.

[0011] In the present invention, by adopting activated carbon adsorption and molecular sieve adsorption steps, most of the impurities such as water, ammonium salt, methanol, methyl acrylate, etc. in the MMPA crude product can be removed, and during purification, these impurities are prevented from affecting the polymerization purification step in the subsequent step.

[0012] Preferably, in the polymerization step, the initiator is one or more of an organic peroxide initiator, an inorganic peroxide initiator, an azo initiator, and a redox initiator; more preferably, it is one or more of ammonium persulfate, benzoyl peroxide, 2,2'-azobisisobutylamidine hydrochloride, and sodium persulfate; and the initiator is 0.05 to 0.15% of the crude quality of 3-methoxy-N,N-dimethylpropionamide.

[0013] Preferably, the set temperature is 75-85° C., and the polymerization time is 1-3 hours.

[0014] Preferably, during nanofiltration, the flow rate is controlled at 10 to 150 L / h and the pressure is controlled at 0.01 to 0.1 MPa.

[0015] Preferably, the distillation is vacuum distillation, and the distillation temperature is controlled to be 90-130° C., and the vacuum degree of the distillation is controlled to be -0.85-0.1 MPa.

[0016] Further preferably, in the distillation step, when the temperature at the top of the distillation tower reaches 74-84° C., the purity of the fraction is detected, and when the purity of the fraction reaches 99.9%, the fraction is collected.

[0017] Beneficial effects of the present invention:

[0018] 1) The purification method of the present invention is relatively simple and easy to industrialize. It can increase the purity of MMPA to above 99.9%, meeting the standards for use as a solvent in battery electrolytes and cathode materials, thereby expanding the application field of MMPA. It can also be used to replace the toxic product NMP, is environmentally friendly, and has great strategic significance for the development of the battery industry.

[0019] 2) In the purification method of the present invention, an adsorption step is first performed to remove impurities such as water, ammonium salts, methanol, and methyl acrylate, while preventing the presence of impurities that could affect subsequent polymerization steps. An initiator is then added to the polymerization step to polymerize N,N-dimethylpropionamide impurities, increasing their molecular weight to form a high-molecular-weight compound or polymer colloid. These impurities are then removed by a nanofiltration step. Finally, a distillation step is performed for further purification to obtain high-purity MMPA. The process flow of the present invention is rationally designed and can efficiently purify MMPA. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a gas chromatogram of the MMPA product after purification in Example 1.

[0021] Figure 2 is a gas chromatogram of the MMPA product after purification in Comparative Example 1.

[0022] Figure 3 is a gas chromatogram of the MMPA product after purification in Comparative Example 2.

[0023] FIG4 is a gas chromatogram of the purified MMPA product in Example 2. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below through specific examples and drawings. The following examples are only used to further illustrate the present invention and should not be construed as limiting the present invention.

[0025] The purity detection method of MMPA in the present invention is gas chromatography.

[0026] Example 1

[0027] 400g of crude MMPA (98.15% purity) was weighed and first subjected to activated carbon adsorption at a flow rate of 6 times the volume of activated carbon per hour, followed by molecular sieve adsorption at a flow rate of 5 times the volume of molecular sieve per hour. (The molecular sieve adsorption step removes impurities such as water, ammonium salts, methanol, and methyl acrylate from the MMPA solvent.) The MMPA, after molecular sieve adsorption, was fed into a polymerization reactor. 0.4g of ammonium persulfate was added as an initiator, and polymerization was carried out at 80°C for 2 hours. After completion of the reaction, the product was passed into a nanofiltration unit at a controlled flow rate of 80 L / h and a pressure of 0.01 to 0.1 MPa for nanofiltration. (Nanofiltration removes high molecular weight compounds and residual polymer colloids.) After nanofiltration, the MMPA enters the distillation kettle for vacuum distillation. First, the vacuum is slowly drawn. When the vacuum reaches a gauge pressure of -0.095 MPa, the front fraction is removed under a stable vacuum state. At this time, the bottom temperature of the kettle is 90°C and the top temperature of the tower is 60°C; the temperature is slowly increased (the heating rate is 0.5°C / min). When the bottom temperature of the kettle reaches 100°C and the top temperature of the tower reaches 76-80°C, the outflowing fraction is continuously detected (once every 10 minutes). When the fraction is detected to be 99.9%, the finished product is received and the finished product is received until the end. The obtained product is 382.65g, and the final detected product content is 99.99%. The gas phase spectrum can be seen in Figure 1.

[0028] Comparative Example 1

[0029] The results are basically the same as those in Example 1, except that the polymerization step is not performed in this comparative example, that is, the MMPA after nanofiltration is directly subjected to vacuum distillation.

[0030] 400 g of crude MMPA (crude purity of 98.15%) was weighed and first subjected to activated carbon adsorption at a flow rate of 6 times the volume of activated carbon per hour, and then subjected to molecular sieve adsorption at a flow rate of 5 times the volume of molecular sieve per hour (the molecular sieve adsorption step can remove water, ammonium salts, methanol, methyl acrylate, and other impurities in the MMPA solvent); the MMPA after molecular sieve adsorption entered the nanofiltration device, and the nanofiltration flow rate was controlled at 80 L / h and the nanofiltration pressure was controlled at 0.01-0.1 MPa for nanofiltration (nanofiltration can remove high molecular weight compounds and residual polymer colloids); the MMPA after nanofiltration entered the rectification kettle, Carry out vacuum distillation, slowly evacuate the vacuum, and remove the front fraction under stable vacuum state when the vacuum reaches the gauge pressure of -0.095MPa. At this time, the bottom temperature of the kettle is 90°C and the top temperature of the tower is 60°C. Slowly increase the temperature (heating rate is 0.5°C / min). When the bottom temperature of the kettle reaches 100°C and the top temperature of the tower reaches 76-80°C, start to continuously detect the outflowing fraction (once every 10 minutes). Continue to detect for 1 hour. The fraction is difficult to reach 99.9%. Therefore, when the fraction is 99.3%, start to receive the finished product and continue to receive the finished product until the end. The obtained product is 385.95g, and the product content of the final detection is 99.78%.

[0031] Compared with Comparative Example 1, Example 1 shows that the MMPA in Example 1 has a higher purity. This may be because no polymerization reaction is performed, and N,N-dimethylpropionamide impurities are difficult to remove, thus making it difficult to further improve its purity.

[0032] Comparative Example 2

[0033] The results are basically the same as those in Example 1, except that the molecular sieve adsorption step is not performed in this comparative example, that is, the crude product is directly polymerized.

[0034] 400 g of MMPA (crude purity of 98.15%) was weighed and directly added to the polymerization reactor, 0.4 g of ammonium persulfate was added to the polymerization reactor as an initiator, and polymerization was carried out at 80°C for 2 hours. After the reaction was completed, it entered the nanofiltration device, controlled the nanofiltration flow rate to 80 L / h, and controlled the nanofiltration pressure to 0.01-0.1 MPa for nanofiltration (nanofiltration can remove high molecular weight compounds and residual polymer colloids). After nanofiltration, the MMPA enters the distillation kettle for vacuum distillation. First, the vacuum is slowly drawn. When the vacuum reaches a gauge pressure of -0.095 MPa, the front fraction is removed under a stable vacuum state. At this time, the bottom temperature of the kettle is 90°C and the top temperature of the tower is 60°C. The temperature is slowly increased (the heating rate is 0.5°C / min). When the bottom temperature of the kettle reaches 100°C and the top temperature of the tower reaches 76-80°C, the outflowing fraction is continuously detected (once every 10 minutes). When the fraction is detected to be 99.9%, the finished product is received and the finished product is received until the end. The obtained product is 383.14g, and the final detected product content is 99.92%. The gas phase spectrum can be seen in Figure 3.

[0035] Compared with Comparative Example 2, Example 1 shows that the MMPA in Example 1 has a higher purity. This may be because no polymerization reaction is carried out, and the adsorption step can remove some impurities to avoid affecting the polymerization reaction, thereby making it more pure.

[0036] Example 2

[0037] 400g of crude MMPA (97.80% purity) was weighed and first subjected to activated carbon adsorption at a flow rate of 6 times the volume of activated carbon per hour, followed by molecular sieve adsorption at a flow rate of 5 times the volume of molecular sieve per hour (the molecular sieve adsorption step removes impurities such as water, ammonium salts, methanol, and methyl acrylate from the MMPA solvent). The MMPA, after molecular sieve adsorption, was then fed into a polymerization reactor. 0.2g of sodium persulfate was added as an initiator, and polymerization was carried out at 75°C for 2.5 hours. After completion of the reaction, the product was passed into a nanofiltration unit at a controlled flow rate of 50 L / h and a pressure of 0.01 to 0.1 MPa for nanofiltration (nanofiltration removes high molecular weight compounds and residual polymer colloids). After nanofiltration, the MMPA enters the distillation kettle for vacuum distillation. First, the vacuum is slowly drawn. When the vacuum reaches a gauge pressure of -0.095 MPa, the front fraction is removed under a stable vacuum state. At this time, the bottom temperature of the kettle is 92°C and the top temperature of the tower is 63°C. The temperature is slowly increased (the heating rate is 1°C / min). When the bottom temperature of the kettle reaches 100°C and the top temperature of the tower reaches 78-82°C, the outflowing fraction is continuously detected (once every 10 minutes). When the fraction is detected to be 99.9%, the finished product is received and the finished product is received until the end. The obtained product is 380.65g, and the final detected product content is 99.96%. The gas phase spectrum can be seen in Figure 4.

[0038] Example 3

[0039] 400g of crude MMPA (98.02% purity) was weighed and first subjected to activated carbon adsorption at a flow rate of 7 times the volume of activated carbon per hour, followed by molecular sieve adsorption at a flow rate of 5 times the volume of molecular sieve per hour. (The molecular sieve adsorption step removes impurities such as water, ammonium salts, methanol, and methyl acrylate from the MMPA solvent.) The MMPA following molecular sieve adsorption was then fed into a polymerization reactor. 0.6g of 2,2'-azobisisobutylamidine hydrochloride was added as an initiator, and polymerization was carried out at 75°C for 1.5 hours. After completion of the reaction, the product was passed into a nanofiltration unit at a controlled flow rate of 100 L / h and a pressure of 0.01-0.1 MPa for nanofiltration. (Nanofiltration removes high molecular weight compounds and residual polymer colloids.) After nanofiltration, the MMPA enters the distillation kettle for vacuum distillation. First, the vacuum is slowly drawn. When the vacuum reaches a gauge pressure of -0.095 MPa, the front fraction is removed under a stable vacuum state. At this time, the bottom temperature of the kettle is 88°C and the top temperature of the tower is 59°C; the temperature is slowly increased (the heating rate is 1°C / min). When the bottom temperature of the kettle reaches 98°C and the top temperature of the tower reaches 74-78°C, the outflowing fraction is continuously detected (once every 10 minutes). When the distillate is detected to be 99.9%, the finished product is received and the finished product is received until the end. The obtained product is 384.26g, and the final detected product content is 99.97%.

Claims

1. A method for purifying 3-methoxy-N,N-dimethylpropionamide, comprising the following steps: The crude 3-methoxy-N,N-dimethylpropionamide is sequentially subjected to adsorption, polymerization, nanofiltration, and distillation steps to obtain purified 3-methoxy-N,N-dimethylpropionamide; wherein, in the polymerization step, an initiator is added to the adsorbed 3-methoxy-N,N-dimethylpropionamide, followed by polymerization at a set temperature. After the polymerization reaction is completed, the process proceeds to the nanofiltration step; The adsorption is molecular sieve adsorption, and the specific steps are as follows: the crude 3-methoxy-N,N-dimethylpropionamide is first adsorbed on activated carbon at a flow rate of 6 to 7 times the volume of activated carbon per hour, then passed through the molecular sieve at a flow rate of 5 times the volume of the molecular sieve per hour, and then enters the subsequent polymerization step; In the polymerization step, the initiator is one or more of ammonium persulfate, 2,2'-azobisisobutylamidine hydrochloride, and sodium persulfate; the initiator is 0.05-0.15% of the crude quality of 3-methoxy-N,N-dimethylpropionamide; the set temperature is 75-80° C., and the polymerization time is 1-2.5 hours; In the distillation step: the distillation is vacuum distillation, the distillation temperature is controlled at 90-130°C, and the vacuum degree is controlled at -0.85-0.1 MPa; when the temperature at the top of the distillation tower reaches 74-84°C, the purity of the distillate is detected, and when the purity of the distillate reaches 99.9%, the distillate is collected.

2. The purification method according to claim 1, wherein During the nanofiltration, the flow rate is controlled to be 10-150 L / h, and the pressure is controlled to be 0.01-0.1 MPa.

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