Preparation method of L-aminopropanol

Abstract

The invention belongs to the technical field of preparation of aminopropanol, and particularly relates to a preparation method of L-aminopropanol. The preparation method of the L-aminopropanol comprises the following steps: (1) preparing a perlite-loaded zirconium oxide carrier; (2) preparing a modified perlite supported zirconium oxide catalyst; (3) preparing 2-methyl aziridine; and (4) uniformly mixing 2-methyl aziridine and tetrabutylammonium bromide, cooling to 0 DEG C, dropwise adding water to carry out hydrolysis reaction, and carrying out post-treatment after hydrolysis to obtain the L-aminopropanol. According to the preparation method of the L-aminopropanol, the 2-methyl aziridine is synthesized through direct dehydration and cyclization in isopropanolamine molecules, then the L-aminopropanol is obtained through direct hydrolysis, the process route is simple, the preparation method is a green chemical synthesis method, and the prepared L-aminopropanol is high in purity and yield.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of aminopropanol, and particularly relates to a method for preparing L-aminopropanol. Background Art

[0002] L-aminopropanol is an important intermediate for synthesizing the third-generation quinolone antibacterial drug levofloxacin, which has the advantages of a broad antibacterial spectrum, strong antibacterial activity, low toxic and side effects, and no cross-resistance with other antibiotics. At the same time, as a chiral modifier, L-aminopropanol has a wide application in the resolution of racemates, so it has a huge market demand.

[0003] The research on the synthesis method of L-aminopropanol can be mainly divided into three types. One is the chiral resolution method, and its main process is to prepare DL-aminopropanol and then obtain L-aminopropanol through chiral resolution. However, due to the high industrialization difficulty of chiral resolution, the second method is generally adopted in industrial production, that is, reducing the corresponding optically active alanine or its derivatives. The reducing agents mainly used in industrial production include KBH 4 , LiBH 4 , NaBH 4 or LiAlH 4 etc. However, such reducing agents are expensive, highly dangerous, have a complex post-treatment process, and cause large environmental pollution, with great limitations. The third is to first prepare 2-methylaziridine, and then hydrolyze 2-methylaziridine to prepare L-aminopropanol. The difficulty of this method lies in the preparation of 2-methylaziridine.

[0004] For the preparation of 2-methylaziridine, concentrated sulfuric acid is first added to generate the intermediate 2-aminopropyl sulfate, which is stable and soluble in water. Subsequently, the concentrated sulfuric acid intermediate is reacted with concentrated sodium hydroxide aqueous solution to finally generate methylaziridine. First, the operation of this liquid-phase production method is quite complex, involving multiple steps and the control of reaction conditions, increasing the technical difficulty of production. Second, due to the use of strong acids and bases such as concentrated sulfuric acid, there is a high risk in the operation process, and strict safety measures need to be taken. In addition, due to the complex production process, the production cost is relatively high, which to a certain extent limits the production scale and efficiency. This production method also has environmental pollution problems, especially when treating wastewater, the inorganic salts generated need to be treated. Therefore, although the liquid-phase kettle method for producing methylaziridine has certain advantages, such as a high yield, its complex operation, high risk, high production cost, and environmental pollution problems make it an urgent need to seek a safer, more economical, and more environmentally friendly production method.

[0005] Therefore, it is necessary to explore a new method for preparing L-aminopropanol. Summary of the Invention

[0006] The object of the present invention is to provide a preparation method of L - aminopropanol. The process route of the described preparation method is simple, environmentally friendly, and the yield and purity of the prepared L - aminopropanol are high.

[0007] The preparation method of L - aminopropanol according to the present invention comprises the following steps: (1) Dissolve zirconium oxychloride in deionized water, heat it to 70 - 73 °C, and dropwise add ammonia water to prepare a sol. Then add expanded perlite to the sol and stir to dissolve it. Aging, drying, and calcination are carried out at room temperature to prepare a perlite - supported zirconia carrier; (2) Dissolve strontium nitrate, nickel chloride, and stannous chloride in deionized water to prepare a mixed solution. Carry out equal - volume impregnation on the perlite - supported zirconia carrier. After impregnation is completed, evaporate the water, dry, and calcine to prepare a modified perlite - supported zirconia catalyst; (3) Pump isopropanolamine into a pre - heating vaporizer through a flowmeter for quantitative control, mix it with nitrogen, pre - heat and vaporize it, and then enter a fixed - bed reactor for reaction. The fixed - bed reactor is filled with a modified perlite - supported zirconia catalyst. After reaction, the material is condensed and gas - liquid separated. The obtained liquid phase is subjected to vacuum distillation to prepare 2 - methylaziridine; (4) Mix 2 - methylaziridine and tetrabutylammonium bromide evenly, cool it to 0 °C, then dropwise add water for hydrolysis reaction. After hydrolysis is completed, carry out post - treatment to prepare L - aminopropanol.

[0008] Wherein: In step (1), the mass ratio of zirconium oxychloride to deionized water is 1:10.

[0009] In step (1), the molar ratio of zirconium oxychloride to ammonia water is 1:2.5 - 2.7.

[0010] In step (1), the mass ratio of zirconium oxychloride to expanded perlite is 1.2 - 1.3:1.

[0011] In step (1), the stirring and dissolving time is 1.5 - 1.8 h, and the stirring and dissolving temperature is 50 - 55 °C.

[0012] In step (1), the aging temperature is room temperature, and the aging time is 24 h.

[0013] In step (1), the drying temperature is 100 - 103 °C, and the drying time is 12 h.

[0014] In step (1), the calcination temperature is 640 - 645 °C, and the calcination time is 2.5 h.

[0015] In step (2), the temperature for evaporating water is 85 °C, the drying temperature is 110 - 113 °C, the drying time is 16 h, the calcination temperature is 465 - 470 °C, and the calcination time is 4.8 h.

[0016] In the modified perlite-supported zirconia catalyst prepared in step (2), the mass of strontium oxide accounts for 22 - 24% of the total mass of the catalyst, the mass of nickel oxide accounts for 8 - 10% of the total mass of the catalyst, the mass of tin oxide accounts for 11 - 13% of the total mass of the catalyst, and the mass of perlite-supported zirconia accounts for 55 - 57% of the total mass of the catalyst.

[0017] In step (3), the volume space velocity of the modified perlite-supported zirconia catalyst in the fixed-bed reactor is 0.53 - 0.55 h -1 .

[0018] In step (3), nitrogen is used as the circulating gas to maintain the reaction pressure in the fixed-bed reactor at atmospheric pressure and the reaction temperature at 450 °C.

[0019] In step (3), the distillation temperature is 50 °C and the distillation pressure is 0.03 MPa.

[0020] In step (4), the mass ratio of 2-methylaziridine, tetrabutylammonium bromide, and water is 1:0.038:4.3.

[0021] In step (4), the dropping time of water is 4 h. During the dropping, the temperature of the system is controlled at 0 °C. After the dropping is completed, the reaction is carried out at room temperature for 20 h for the hydrolysis reaction.

[0022] In step (4), the post-treatment is to let it stand and separate layers after the reaction is completed. The aqueous layer is extracted with dichloromethane and then combined with the organic layer. Then, dichloromethane is removed by vacuum distillation, and finally, vacuum distillation is carried out to collect the fraction at 72 - 73 °C to prepare L-alaninol.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) In the preparation method of L - aminopropanol of the present invention, first, isopropanolamine is used as the reaction raw material, and nitrogen is used as the circulating gas for gas - solid phase reaction to prepare 2 - methylaziridine, and then 2 - methylaziridine is hydrolyzed to prepare L - aminopropanol. When preparing 2 - methylaziridine, zirconia - loaded modified perlite is used as the catalyst, and perlite - loaded zirconia is used as the catalyst support. The introduced zirconia can improve the thermal stability of the expanded perlite support at high temperatures and further increase the surface area of the support through its own porous structure, improving the dispersion of the active components, so that the catalyst support has both acidic and basic sites. Strontium, nickel, and tin are used as the catalyst active components. The acid - base bifunctional sites in the catalyst can stably generate methylaziridine. The addition of strontium can effectively prevent the occurrence of deamination reaction or intermolecular condensation reaction. The addition of nickel effectively prevents the promotion of intermolecular dehydration by acidic sites. The presence of tin can promote the conversion of isopropanolamine. The interaction between strontium and nickel promotes the synthesis of methylaziridine, and the presence of zirconia in the support can effectively prevent the loss of active components. Thus, the carrier and the active components in the catalyst act synergistically, showing good catalytic activity for the direct cyclization reaction of isopropanolamine.

[0024] (2) In the preparation method of L - aminopropanol of the present invention, the process route of directly dehydrating and cyclizing isopropanolamine intramolecularly to synthesize 2 - methylaziridine and then directly hydrolyzing to obtain L - aminopropanol is simple, which is a green chemical synthesis method, and the purity and yield of the prepared L - aminopropanol are high. Specific embodiments

[0025] The present invention will be further described below in conjunction with embodiments.

[0026] Example 1 The preparation method of L - aminopropanol described in Example 1 of the present invention consists of the following steps: (1) Dissolve zirconium oxychloride in deionized water, heat it to 71 °C, and dropwise add ammonia water to prepare a sol. Then add expanded perlite to the sol and stir to dissolve it. Age, dry, and calcine at room temperature to prepare a perlite - loaded zirconia support; (2) Dissolve strontium nitrate, nickel chloride, and stannous chloride in deionized water to prepare a mixed solution. Perform equal - volume impregnation on the perlite - loaded zirconia support. After impregnation, evaporate the water, dry, and calcine to prepare a zirconia - loaded modified perlite catalyst; (3) Pump isopropanolamine quantitatively through a flow meter and mix it with nitrogen in a pre - heating vaporizer, pre - heat and vaporize it, and then enter a fixed - bed reactor for reaction. The fixed - bed reactor is filled with a zirconia - loaded modified perlite catalyst. After the reaction, the material is condensed and separated into gas and liquid. The obtained liquid phase is subjected to vacuum distillation to prepare 2 - methylaziridine; (4) Mix 2-methylaziridine and tetrabutylammonium bromide evenly, cool to 0 °C, then add water dropwise for hydrolysis reaction. After the hydrolysis is completed, L-alaninol is prepared through post-treatment.

[0027] Among them: In step (1), the mass ratio of zirconium oxychloride to deionized water is 1:10.

[0028] In step (1), the molar ratio of zirconium oxychloride to ammonia water is 1:2.6.

[0029] In step (1), the mass ratio of zirconium oxychloride to expanded perlite is 1.25:1.

[0030] In step (1), the stirring and dissolving time is 1.6 h, and the stirring and dissolving temperature is 53 °C.

[0031] In step (1), the aging temperature is room temperature, and the aging time is 24 h.

[0032] In step (1), the drying temperature is 102 °C, and the drying time is 12 h.

[0033] In step (1), the calcination temperature is 643 °C, and the calcination time is 2.5 h.

[0034] In step (2), the temperature for evaporating water is 85 °C, the drying temperature is 112 °C, the drying time is 16 h, the calcination temperature is 467 °C, and the calcination time is 4.8 h.

[0035] In the modified perlite-supported zirconium oxide catalyst prepared in step (2), the mass of strontium oxide accounts for 23% of the total mass of the catalyst, the mass of nickel oxide accounts for 9% of the total mass of the catalyst, the mass of tin oxide accounts for 12% of the total mass of the catalyst, and the mass of perlite-supported zirconium oxide accounts for 56% of the total mass of the catalyst.

[0036] In step (3), the volume space velocity of the modified perlite-supported zirconium oxide catalyst in the fixed-bed reactor is 0.54 h -1 .

[0037] In step (3), nitrogen is used as the recycle gas to keep the reaction pressure in the fixed-bed reactor at atmospheric pressure, and the reaction temperature is 450 °C.

[0038] In step (3), the distillation temperature is 50 °C, and the distillation pressure is 0.03 MPa.

[0039] In step (4), the mass ratio of 2-methylaziridine, tetrabutylammonium bromide, and water is 1:0.038:4.3.

[0040] In step (4), the dropping time of water is 4 h, the temperature of the system is controlled at 0 °C during dropping, and after dropping, the reaction is carried out at room temperature for 20 h for hydrolysis reaction.

[0041] The post-treatment described in step (4) is to let it stand for layering after the reaction is completed. The aqueous layer is extracted with dichloromethane and then combined with the organic layer. Then, dichloromethane is removed by vacuum distillation. Finally, vacuum distillation is carried out to collect the fraction at 72 - 73 °C to prepare L-alaninol.

[0042] After analysis, the conversion rate of isopropanolamine in the preparation of 2-methylaziridine in step (3) is 95.32%, and the selectivity of 2-methylaziridine is 93.28%; the yield of L-alaninol prepared in step (4) is 86.46%, and the purity of L-alaninol is 99.63%.

[0043] Example 2 The preparation method of L-alaninol described in this Example 2 consists of the following steps: (1) Dissolve zirconium oxychloride in deionized water, heat it to 70 °C and dropwise add ammonia water to prepare a sol. Then add expanded perlite to the sol and stir to dissolve it. Aging, drying, and calcination are carried out at room temperature to prepare a perlite-supported zirconium oxide carrier. (2) Dissolve strontium nitrate, nickel chloride, and stannous chloride in deionized water to prepare a mixed solution. Perform equal-volume impregnation on the perlite-supported zirconium oxide carrier. After impregnation is completed, evaporate the water, dry it, and calcine it to prepare a modified perlite-supported zirconium oxide catalyst. (3) Pump isopropanolamine quantitatively into a preheating vaporizer through a flow meter and mix it with nitrogen for preheating and vaporization, then enter a fixed-bed reactor for reaction. The fixed-bed reactor is filled with a modified perlite-supported zirconium oxide catalyst. The reaction product is condensed and subjected to gas-liquid separation. The obtained liquid phase is subjected to vacuum distillation to prepare 2-methylaziridine. (4) Mix 2-methylaziridine and tetrabutylammonium bromide evenly, cool it to 0 °C and then dropwise add water for hydrolysis reaction. After hydrolysis is completed, carry out post-treatment to prepare L-alaninol.

[0044] Among them: In step (1), the mass ratio of zirconium oxychloride to deionized water is 1:10.

[0045] In step (1), the molar ratio of zirconium oxychloride to ammonia water is 1:2.5.

[0046] In step (1), the mass ratio of zirconium oxychloride to expanded perlite is 1.3:1.

[0047] In step (1), the stirring and dissolving time is 1.8 h, and the stirring and dissolving temperature is 50 °C.

[0048] In step (1), the aging temperature is room temperature, and the aging time is 24 h.

[0049] In step (1), the drying temperature is 100 °C and the drying time is 12 h.

[0050] In step (1), the calcination temperature is 645 °C and the calcination time is 2.5 h.

[0051] In step (2), the temperature for evaporating water is 85 °C, the drying temperature is 110 °C, the drying time is 16 h, the calcination temperature is 470 °C, and the calcination time is 4.8 h.

[0052] In the modified perlite-supported zirconia catalyst prepared in step (2), the mass of strontium oxide accounts for 24% of the total mass of the catalyst, the mass of nickel oxide accounts for 8% of the total mass of the catalyst, the mass of tin oxide accounts for 11% of the total mass of the catalyst, and the mass of perlite-supported zirconia accounts for 57% of the total mass of the catalyst.

[0053] In step (3), the volume space velocity of the modified perlite-supported zirconia catalyst in the fixed-bed reactor is 0.53 h -1 .

[0054] In step (3), nitrogen is used as the recycle gas to keep the reaction pressure in the fixed-bed reactor at atmospheric pressure and the reaction temperature at 450 °C.

[0055] In step (3), the distillation temperature is 50 °C and the distillation pressure is 0.03 MPa.

[0056] In step (4), the mass ratio of 2-methylaziridine, tetrabutylammonium bromide, and water is 1:0.038:4.3.

[0057] In step (4), the dropping time of water is 4 h, the temperature of the system is controlled at 0 °C during dropping, and after dropping, the reaction is carried out at room temperature for 20 h for hydrolysis reaction.

[0058] After analysis, the conversion rate of isopropanolamine is 94.37% and the selectivity of 2-methylaziridine is 92.09% in the preparation of 2-methylaziridine in step (3); the yield of L-alaninol is 83.68% and the purity of L-alaninol is 99.55% in the preparation of L-alaninol in step (4).

[0059] Example 3 The preparation method of L-alaninol described in this Example 3 consists of the following steps: (1) Dissolve zirconium oxychloride in deionized water, heat it to 73 °C, dropwise add ammonia water to prepare a sol, then add expanded perlite to the sol and stir to dissolve, and carry out aging, drying, and calcination at room temperature to prepare a perlite-supported zirconia carrier; (2) Dissolve strontium nitrate, nickel chloride, and stannous chloride in deionized water to prepare a mixed solution, and perform equal-volume impregnation on the perlite-supported zirconia carrier. After impregnation, evaporate the water, dry, and calcine to prepare a modified perlite-supported zirconia catalyst; (3) Pump isopropanolamine into a preheating vaporizer through a flow meter for quantitative control, mix it with nitrogen for preheating and vaporization, and then enter a fixed-bed reactor for reaction. The fixed-bed reactor is filled with the modified perlite-supported zirconia catalyst. After the reaction, the material is condensed and separated into gas and liquid. The obtained liquid phase is subjected to vacuum distillation to prepare 2-methylaziridine; (4) Mix 2-methylaziridine and tetrabutylammonium bromide evenly, cool to 0 °C, and then dropwise add water for hydrolysis reaction. After hydrolysis, perform post-treatment to prepare L-alaninol.

[0060] Among them: In step (1), the mass ratio of zirconium oxychloride to deionized water is 1:10.

[0061] In step (1), the molar ratio of zirconium oxychloride to ammonia water is 1:2.7.

[0062] In step (1), the mass ratio of zirconium oxychloride to expanded perlite is 1.2:1.

[0063] In step (1), the stirring and dissolution time is 1.5 h, and the stirring and dissolution temperature is 55 °C.

[0064] In step (1), the aging temperature is room temperature, and the aging time is 24 h.

[0065] In step (1), the drying temperature is 103 °C, and the drying time is 12 h.

[0066] In step (1), the calcination temperature is 640 °C, and the calcination time is 2.5 h.

[0067] In step (2), the temperature for evaporating water is 85 °C, the drying temperature is 113 °C, the drying time is 16 h, the calcination temperature is 465 °C, and the calcination time is 4.8 h.

[0068] In the modified perlite-supported zirconia catalyst prepared in step (2), the mass of strontium oxide accounts for 22% of the total mass of the catalyst, the mass of nickel oxide accounts for 10% of the total mass of the catalyst, the mass of tin oxide accounts for 13% of the total mass of the catalyst, and the mass of perlite-supported zirconia accounts for 55% of the total mass of the catalyst.

[0069] In step (3), the volume space velocity of the modified perlite-supported zirconia catalyst in the fixed-bed reactor is 0.55 h -1 .

[0070] In step (3), nitrogen is used as the recycle gas to keep the reaction pressure in the fixed-bed reactor at atmospheric pressure and the reaction temperature at 450 °C.

[0071] In step (3), the distillation temperature is 50 °C and the distillation pressure is 0.03 MPa.

[0072] In step (4), the mass ratio of 2-methylaziridine, tetrabutylammonium bromide, and water is 1:0.038:4.3.

[0073] In step (4), the dropping time of water is 4 h. During the dropping, the temperature of the system is controlled at 0 °C. After the dropping is completed, the reaction is carried out at room temperature for 20 h for the hydrolysis reaction.

[0074] After analysis, in step (3), the conversion rate of isopropanolamine in the preparation of 2-methylaziridine is 94.85%, and the selectivity of 2-methylaziridine is 92.73%; in step (4), the yield of L-alaninol prepared is 85.13%, and the purity of L-alaninol is 99.60%.

[0075] Comparative Example 1 The preparation method of L-alaninol described in this Comparative Example 1 is the same as that in Example 1. The only difference is that in step (1), instead of using zirconia to modify expanded perlite, expanded perlite is directly used as the catalyst support. After analysis, in step (3), the conversion rate of isopropanolamine in the preparation of 2-methylaziridine is 81.56%, and the selectivity of 2-methylaziridine is 77.61%; in step (4), the yield of L-alaninol prepared is 61.55%, and the purity of L-alaninol is 80.31%.

[0076] Comparative Example 2 The preparation method of L-alaninol described in this Comparative Example 2 is the same as that in Example 1. The only difference is that in step (2), strontium nitrate is not added. After analysis, in step (3), the conversion rate of isopropanolamine in the preparation of 2-methylaziridine is 83.72%, and the selectivity of 2-methylaziridine is 80.56%; in step (4), the yield of L-alaninol prepared is 65.58%, and the purity of L-alaninol is 83.43%.

[0077] Comparative Example 3 The preparation method of L-alaninol described in this Comparative Example 3 is the same as that in Example 1. The only difference is that in step (2), nickel chloride is not added. After analysis, in step (3), the conversion rate of isopropanolamine in the preparation of 2-methylaziridine is 90.93%, and the selectivity of 2-methylaziridine is 86.85%; in step (4), the yield of L-alaninol prepared is 76.79%, and the purity of L-alaninol is 90.45%.

[0078] Comparative Example 4 The preparation method of L - aminopropanol described in this Comparative Example 4 is the same as that in Example 1. The only difference is that stannous chloride is not added in step (2). After analysis, the conversion rate of isopropanolamine in the preparation of 2 - methylaziridine in step (3) is 87.91%, and the selectivity of 2 - methylaziridine is 85.20%; the yield of L - aminopropanol obtained in step (4) is 72.83%, and the purity of L - aminopropanol is 88.69%.

Claims

1. A method for preparing L-aminopropanol, characterized in that: It consists of the following steps: (1) dissolving zirconium oxychloride in deionized water, heating the water to 70-73° C., adding ammonia water dropwise thereto to prepare a sol, then adding expanded perlite to the sol, stirring and dissolving the sol, aging, drying and calcining the sol at room temperature to prepare a perlite-loaded zirconium oxide carrier; (2) Strontium nitrate, nickel chloride and stannous chloride are dissolved in deionized water to prepare a mixed solution, and an equal volume of the mixed solution is impregnated into a perlite-supported zirconia support. After the impregnation, the water is evaporated, the mixture is dried and calcined to prepare a modified perlite-supported zirconia catalyst; (3) isopropanolamine is quantitatively pumped into a preheating gasifier by a pump through a flow meter and mixed with nitrogen for preheating and gasification, and then enters a fixed bed reactor for reaction. The fixed bed reactor is filled with a modified perlite-supported zirconium oxide catalyst. After the reaction, the material is condensed and the gas-liquid is separated. The obtained liquid phase is subjected to reduced pressure distillation to prepare 2-methylaziridine; (4) 2-Methylaziridine and tetrabutylammonium bromide are mixed evenly, cooled to 0°C, and then water is added dropwise to carry out a hydrolysis reaction. After the hydrolysis is completed, L-aminopropanol is prepared by post-treatment.

2. The method for preparing L-aminopropanol according to claim 1, wherein: In step (1), the mass ratio of zirconium oxychloride to deionized water is 1:10; In step (1), the molar ratio of zirconium oxychloride to ammonia water is 1:2.5-2.7; In step (1), the mass ratio of zirconium oxychloride to expanded perlite is 1.2-1.3:

1.

3. The method for preparing L-aminopropanol according to claim 1, wherein: The stirring and dissolving time in step (1) is 1.5-1.8 hours, and the stirring and dissolving temperature is 50-55°C; In step (1), the aging temperature is room temperature and the aging time is 24 hours; In step (1), the drying temperature is 100-103°C and the drying time is 12h; In step (1), the calcination temperature is 640-645° C. and the calcination time is 2.5 h.

4. The method for preparing L-aminopropanol according to claim 1, wherein: In step (2), the temperature for evaporating water is 85°C, the drying temperature is 110-113°C, the drying time is 16 hours, the roasting temperature is 465-470°C, and the roasting time is 4.8 hours; In the modified perlite-supported zirconia catalyst prepared in step (2), the mass of strontium oxide accounts for 22-24% of the total mass of the catalyst, the mass of nickel oxide accounts for 8-10% of the total mass of the catalyst, the mass of tin oxide accounts for 11-13% of the total mass of the catalyst, and the mass of perlite-supported zirconia accounts for 55-57% of the total mass of the catalyst.

5. The method for preparing L-aminopropanol according to claim 1, wherein: Step (3) The volume space velocity of the modified perlite-supported zirconia catalyst in the fixed bed reactor is 0.53-0.55 h -1 .

6. The method for preparing L-aminopropanol according to claim 1, wherein: In step (3), nitrogen is used as circulating gas to maintain the reaction pressure in the fixed bed reactor at normal pressure and the reaction temperature at 450°C.

7. The method for preparing L-aminopropanol according to claim 1, wherein: In step (3), the distillation temperature is 50° C. and the distillation pressure is 0.03 MPa.

8. The method for preparing L-aminopropanol according to claim 1, wherein: In step (4), the mass ratio of 2-methylaziridine, tetrabutylammonium bromide and water is 1:0.038:4.

3.

9. The method for preparing L-aminopropanol according to claim 1, wherein: In step (4), the water is added dropwise for 4 hours, and the temperature of the system is controlled to be 0°C during the addition. After the addition is completed, the hydrolysis reaction is carried out at room temperature for 20 hours.

10. The method for preparing L-aminopropanol according to claim 1, characterized in that: The post-treatment in step (4) is to allow the reaction to stand for stratification after completion, extract the aqueous layer with dichloromethane and combine it with the organic layer, then distill under reduced pressure to remove the dichloromethane, and finally perform vacuum distillation to collect the fraction at 72-73° C. to prepare L-aminopropanol.