Method and system for preparing dihydroxypropyl hydroxylamine

Abstract

The invention relates to the technical field of preparation of dihydroxypropyl hydroxylamine, and discloses a method and a system for preparing dihydroxypropyl hydroxylamine, and the method comprises the following steps: (1) mixing propylene oxide, hydroxylamine salt and water; (2) mixing the mixture obtained in the step (1) with inorganic alkali for reaction to obtain a mixed product containing dihydroxypropyl hydroxylamine; (3) carrying out first reduced pressure distillation on the mixed product to remove water so as to obtain a solid intermediate product; (4) dissolving the solid intermediate product in an organic solvent, and then carrying out solid-liquid separation; wherein the organic solvent is selected from at least one of alkane of C5-C12, alcohol of C1-C6 and ketone of C3-C6; and (5) carrying out second reduced pressure distillation on the liquid phase obtained by solid-liquid separation to remove the organic solvent. According to the method, inorganic salt impurities can be more efficiently removed through a simple primary reduced pressure distillation-filtration-secondary reduced pressure distillation method, the separation process is simple, and the purity and yield of the obtained product are high.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of dihydroxypropylhydroxylamine, and in particular to a method and system for preparing dihydroxypropylhydroxylamine. Background Art

[0002] Bis(hydroxypropyl)hydroxylamine is an important fine chemical product with two main uses. First, it has a very good inhibitory effect on olefin polymerization and is often used in styrene production equipment. It can be used alone or in combination with other inhibitors. On the other hand, bis(hydroxypropyl)hydroxylamine is an organic reducing agent. It can be used to produce antioxidants or as a boiler descaling agent.

[0003] At present, there are few reports on the synthesis method of dihydroxypropylhydroxylamine. CN106957240A discloses a synthesis method of hydroxypropylhydroxylamine, which is prepared by a two-step method: the first step is to dissolve the substituted hydroxylamine in a solvent and then add alkali solution to fully mix and prepare a free base, the second step is to add propylene oxide to the solvent to obtain a mixed product, and finally, after extraction and rotary evaporation, hydroxypropylhydroxylamine can be obtained. The intermediate product free base of this method is a highly reactive substance, which has great safety hazards, and the method does not finally give the yield and purity of the product, and the economic benefit cannot be evaluated. US6028225A discloses a method for generating dihydroxypropylhydroxylamine by reacting 50% hydroxylamine free base and propylene oxide. The raw materials of this method are difficult to obtain, and the data such as product yield and purity are also not given, and the economic benefit cannot be evaluated. CN112159333A discloses a method for preparing dihydroxypropylhydroxylamine by reacting propylene oxide, hydroxylamine salt and inorganic alkali solution. Since the method uses inorganic alkali solution, the reaction will generate inorganic salts soluble in water, and the subsequent purification steps are relatively complicated. In addition, the inorganic salts in the aqueous solution are difficult to separate, which affects the purity and yield of the product. CN115724763A discloses a method for preparing diisopropylhydroxylamine. Diisopropylhydroxylamine is prepared by using hydroxylamine salt, organic solvent, propylene oxide and organic base, which can improve the purity of the product. However, since the organic base is easily decomposed, the required reaction conditions are relatively harsh and the raw material cost is high.

[0004] Therefore, there is an urgent need to develop a method for synthesizing dihydroxypropylhydroxylamine with a simple preparation method, a safe and reliable preparation process, high product purity and no inorganic salt impurities in the product. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of high inorganic salt impurity content, insufficient purity and low yield in the prior art of dihydroxypropylhydroxylamine, and to provide a method and system for preparing dihydroxypropylhydroxylamine, which can take into account both high dihydroxypropylhydroxylamine purity and yield, and low inorganic salt impurity content in the product.

[0006] In order to achieve the above object, the present invention provides a method for preparing dihydroxypropylhydroxylamine, which comprises:

[0007] (1) mixing propylene oxide, hydroxylamine salt and water;

[0008] (2) mixing the mixture obtained in step (1) with an inorganic base to react to obtain a mixed product containing dihydroxypropylhydroxylamine;

[0009] (3) subjecting the mixed product to a first reduced pressure distillation to remove water to obtain a solid intermediate product;

[0010] (4) dissolving the solid intermediate product in an organic solvent, and then performing solid-liquid separation;

[0011] Wherein, the organic solvent is selected from at least one of C5-C12 alkanes, C1-C6 alcohols and C3-C6 ketones;

[0012] (5) The liquid phase obtained by solid-liquid separation is subjected to a second reduced-pressure distillation to remove the organic solvent.

[0013] Preferably, in step (1), the mass ratio of water to propylene oxide is 0.5-5:1, preferably 0.8-2:1.

[0014] Preferably, in step (2), the reaction conditions include: the reaction temperature is 40-70°C, preferably 55-65°C, and the reaction time is 1-8h, preferably 3-6h.

[0015] Another aspect of the present invention provides a reaction system for preparing dihydroxypropylhydroxylamine, comprising: a reactor 11, a primary vacuum distillation device 12, a solid-liquid separator 13 and a secondary vacuum distillation device 14 connected in sequence;

[0016] The reactor 11 is provided with a first raw material inlet and a second raw material inlet, propylene oxide, hydroxylamine salt and water are fed into the reactor 11 through the first raw material inlet, and the inorganic base is fed into the reactor 11 through the second raw material inlet;

[0017] The primary vacuum distillation device 12 is provided with a mixed product inlet and an organic solvent inlet, and is used to perform a first vacuum distillation to remove water from the mixed product containing dihydroxypropylhydroxylamine from the reactor 11, and then mix it with the organic solvent fed into the primary vacuum distillation device 12 through the organic solvent inlet;

[0018] The solid-liquid separator 13 is used to separate the solid and liquid of the product from the primary vacuum distillation device 12, and the obtained liquid phase is sent to the secondary vacuum distillation device 14 for a second vacuum distillation to remove the organic solvent.

[0019] The method provided by the present invention obtains dihydroxypropylhydroxylamine in one step by reacting hydroxylamine salt, propylene oxide and inorganic base. The inorganic salt impurities can be removed more efficiently by a simple method of once vacuum distillation-filtration-second vacuum distillation, the separation process is simple, and the purity and yield of the obtained product are high. Furthermore, the inventors of the present invention have found in their research that by controlling the reaction temperature and the amount of water, the water removal effect of the subsequent vacuum distillation is beneficial, and the purity of the product is further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of a reaction system for preparing dihydroxypropylhydroxylamine in the present invention.

[0021] Description of Reference Numerals

[0022] 11 Reactor 12 Primary vacuum distillation device 13 Solid-liquid separator

[0023] 14 Secondary vacuum distillation device 1 First raw material inlet 2 Second raw material inlet

[0024] 3 Mixed product inlet 4 Solvent water outlet 5 Organic solvent inlet

[0025] 6 Solid-liquid separator feed port 7 Solid phase outlet 8 Liquid phase inlet

[0026] 9 Organic solvent outlet 10 Product outlet DETAILED DESCRIPTION

[0027] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0028] One aspect of the present invention provides a method for preparing dihydroxypropylhydroxylamine, the method comprising:

[0029] (1) mixing propylene oxide, hydroxylamine salt and water;

[0030] (2) mixing the mixture obtained in step (1) with an inorganic base to react to obtain a mixed product containing dihydroxypropylhydroxylamine;

[0031] (3) subjecting the mixed product to a first reduced pressure distillation to remove water to obtain a solid intermediate product;

[0032] (4) dissolving the solid intermediate product in an organic solvent, and then performing solid-liquid separation;

[0033] Wherein, the organic solvent is selected from at least one of C5-C12 alkanes, C1-C6 alcohols and C3-C6 ketones;

[0034] (5) The liquid phase obtained by solid-liquid separation is subjected to a second reduced-pressure distillation to remove the organic solvent.

[0035] When bishydroxypropylhydroxylamine is prepared by reacting hydroxylamine salt with inorganic alkali solution in a water system, the reaction will generate water-soluble inorganic salts due to the use of inorganic alkali solution. The presence of inorganic salts will affect the purity of the product. Usually, extraction and distillation are required to separate the inorganic salts. However, it is difficult to remove the inorganic salts in one step by traditional extraction methods. Usually, more than two extraction treatments are required. The purification steps are relatively complicated, and multiple extractions will inevitably lead to product losses. Although the purity of the product can be improved, the yield of the product is not ideal.

[0036] The inorganic salt content (in terms of metal) in the commercialized bishydroxypropylhydroxylamine is usually about 5wt%, and the residual inorganic salt will corrode the process equipment, affecting the application of bishydroxypropylhydroxylamine in various processes. The method for preparing bishydroxypropylhydroxylamine provided by the present invention can control the inorganic salt content in the product to within 1wt%, and can take into account the high purity and yield of bishydroxypropylhydroxylamine. Controlling the inorganic salt content in the product to within 1wt% is conducive to the application of the bishydroxypropylhydroxylamine product in downstream industrial devices.

[0037] According to the present invention, the mixing in step (1) is carried out under heating conditions, preferably, the mixing temperature is 40-70°C, preferably 55-65°C.

[0038] The present invention has no particular requirements for the mixing method and order of propylene oxide, hydroxylamine salt and water in step (1). Propylene oxide, hydroxylamine salt and water can be added to the reaction kettle together for mixing, or hydroxylamine salt and water can be mixed first and then propylene oxide can be added for mixing.

[0039] According to some preferred embodiments of the present invention, in step (1), the mass ratio of water to propylene oxide is 0.5-5:1, for example, it can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 2:1, 3:1, 4:1, 5:1, etc., which are typical but not limiting mass ratios or ranges therebetween. Preferably, the mass ratio of water to propylene oxide is 0.8-2:1. The inventors of the present invention have found in their research that by controlling the amount of water and propylene oxide, the water removal effect of the subsequent vacuum distillation is facilitated, the removal effect of inorganic salts is further improved, and the product purity is improved.

[0040] According to some preferred embodiments of the present invention, in step (1), the mass ratio of water to hydroxylamine salt is 2-10:1, preferably 2-4:1.

[0041] In the present invention, the selection range of the hydroxylamine salt is relatively wide, and it can be the type of hydroxylamine salt conventionally used in the art for preparing dihydroxypropylhydroxylamine. According to the present invention, preferably, the hydroxylamine salt is selected from at least one of hydroxylamine sulfate, hydroxylamine hydrochloride and hydroxylamine phosphate.

[0042] According to a particularly preferred embodiment of the present invention, the hydroxylamine salt is hydroxylamine hydrochloride. Using hydroxylamine hydrochloride as the hydroxylamine raw material can further improve the purity and yield of the dihydroxypropylhydroxylamine product.

[0043] According to the present invention, preferably, in step (2), the reaction conditions include: the reaction temperature is 40-70°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C or other specific temperature values ​​or any range between two. Preferably, the reaction temperature is 55-65°C, and the reaction time is 1-8h, preferably 3-6h. The above preferred embodiment is conducive to further improving the purity and yield of the reaction product.

[0044] In the present invention, the reaction system is carried out in the presence of water, so that propylene oxide, hydroxylamine salt and inorganic base react to prepare dihydroxypropylhydroxylamine, the reaction raw materials are easily available and the cost is low.

[0045] According to the present invention, the inorganic base can be provided by an aqueous solution of an inorganic base, and the concentration of the aqueous solution of the inorganic base can be, for example, 10-45 wt %.

[0046] Preferably, the mass ratio of the hydroxylamine salt to the inorganic base is (0.01-5):1, preferably (1-2):1.

[0047] The present invention has no particular limitation on the specific type of the inorganic base, and conventional inorganic bases in the art can be used, and the inorganic base can be, for example, an alkali metal hydroxide. Preferably, the inorganic base is sodium hydroxide and / or potassium hydroxide.

[0048] In the present invention, water in the mixed product containing dihydroxypropylhydroxylamine is removed by the first vacuum distillation, the top discharge of the distillation tower is water, and the bottom discharge is a solid intermediate product. The present invention has no special requirements for the specific operating conditions of the first vacuum distillation, as long as the above-mentioned water removal effect can be achieved. Preferably, the conditions of the first vacuum distillation include: a pressure of 0-500mbar, preferably 50-200mbar; a temperature of 20-150°C, preferably 60-110°C. The above preferred embodiment can not only ensure a sufficient water removal effect, but also help to reduce energy consumption.

[0049] According to the present invention, preferably, the method further comprises: subjecting the product obtained by the first decompression distillation to first drying, and then obtaining the solid intermediate product. The first drying method may be, for example, allowing the product obtained by the first decompression distillation to stand at room temperature.

[0050] According to the present invention, the inorganic salt generated by the reaction is insoluble in the organic solvent, and the precipitated insoluble impurities can be removed by solid-liquid separation by dissolving the solid intermediate product in the organic solvent. The organic solvent is selected from at least one of C5-C12 alkanes, C1-C6 alcohols and C3-C6 ketones. Preferably, the organic solvent is selected from at least one of n-pentane, n-hexane, n-heptane, acetone, methanol, ethanol, propanol, n-butanol, isobutanol and cyclohexanol, more preferably methanol and / or n-butanol.

[0051] According to the present invention, preferably, the mass ratio of the organic solvent to the solid intermediate product is 0.5-10:1, preferably 1-4:1.

[0052] The present invention has no particular limitation on the solid-liquid separation method, and it can be carried out by conventional operation methods in the art, such as filtration, suction filtration or centrifugation.

[0053] The present invention has no particular requirements for the specific operating conditions of the second vacuum distillation, as long as the above-mentioned effect of removing organic solvent can be achieved. Preferably, the conditions of the second vacuum distillation include: a pressure of 0-500 mbar, preferably 50-200 mbar; a temperature of 20-140°C, preferably 30-100°C.

[0054] According to the present invention, preferably, the method further comprises: subjecting the product obtained by the second reduced pressure distillation to a second drying step. The second drying step may be carried out in the same manner as the first drying step.

[0055] Another aspect of the present invention provides a reaction system for preparing dihydroxypropylhydroxylamine, comprising: a reactor 11, a primary vacuum distillation device 12, a solid-liquid separator 13 and a secondary vacuum distillation device 14 connected in sequence;

[0056] The reactor 11 is provided with a first raw material inlet 1 and a second raw material inlet 2, propylene oxide, hydroxylamine salt and water are fed into the reactor 11 through the first raw material inlet 1, and the inorganic base is fed into the reactor 11 through the second raw material inlet 2; the discharge port of the reactor 11 is connected with the mixed product inlet 3 of the primary vacuum distillation device 12, and the mixed product containing dihydroxypropylhydroxylamine from the reactor 11 is fed into the primary vacuum distillation device 12 for first vacuum distillation to remove water, and the removed water is discharged from the system through the solvent water outlet 4, and the primary vacuum distillation device 12 is also provided with an organic solvent inlet 5, and the organic solvent is fed into the primary vacuum distillation device 12 through the organic solvent inlet 5 to be mixed with the product of the first vacuum distillation.

[0057] The solid-liquid separator 13 is provided with a solid-liquid separator feed port 6, a solid phase outlet 7 and a liquid phase outlet. The discharge port of the primary vacuum distillation device 12 is connected to the solid-liquid separator feed port 6. The mixture of the solid intermediate product and the organic solvent is fed into the solid-liquid separator 13 for solid-liquid separation, and the obtained solid phase impurities are sent out of the reaction system through the solid phase outlet 7; the obtained liquid phase is fed into the secondary vacuum distillation device 14 through the liquid phase inlet 8 for a second vacuum distillation to remove the organic solvent, and the obtained organic solvent is sent out of the system through the organic solvent outlet 9 of the secondary vacuum distillation device 14 or returned to the first vacuum distillation device, and the remaining product is collected through the product outlet 10.

[0058] Preferably, the reactor is a reactor.

[0059] Preferably, the primary vacuum distillation apparatus and / or the secondary vacuum distillation apparatus is an evaporator.

[0060] Preferably, the solid-liquid separator is a filter.

[0061] The present invention will be described in detail below through examples.

[0062] Unless otherwise specified, the raw materials used in the following examples and comparative examples are commercially available.

[0063] In the following examples and comparative examples:

[0064] Yield (%) = mass of dihydroxypropylhydroxylamine in the product / theoretical mass of dihydroxypropylhydroxylamine produced;

[0065] The purity analysis method is: perform chromatographic analysis on the product and compare it with the standard sample of dihydroxypropylhydroxylamine to obtain the purity of the product.

[0066] Example 1

[0067] Use Figure 1 The reaction system is shown.

[0068] Add 6.95g of hydroxylamine hydrochloride, 11.7g of propylene oxide, and 15g of water to the reactor, heat to 60°C and mix thoroughly; add 13.4g of 30% by mass sodium hydroxide aqueous solution dropwise, and continue to react for 4h after the addition is complete. After the reaction is completed, perform a reduced pressure distillation at 100°C and 50mbar to remove the solvent water, and after standing and drying for a period of time, obtain 19.85g of crude product, dissolve the crude product in 60g of methanol, filter out undissolved impurities after sufficient dissolution, and perform a second reduced pressure distillation of the methanol solution at 40°C and 50mbar to remove the organic solvent. After the obtained product is stood and dried for a period of time, obtain 13.876g of bishydroxypropylhydroxylamine with a purity of 96.1%, and the yield is 89.38%. The content of sodium ions in the product bishydroxypropylhydroxylamine is less than 1500ppm.

[0069] Example 2

[0070] Add 6.95g of hydroxylamine hydrochloride, 17.4g of propylene oxide, and 15g of water to the reactor, heat to 60°C and mix thoroughly; add 13.4g of 30% by mass sodium hydroxide aqueous solution dropwise, and continue to react for 4h after the addition is complete. After the reaction is completed, perform a reduced pressure distillation at 80°C and 100mbar to remove the solvent water, and after standing and drying for a period of time, obtain 21.05g of crude product, dissolve the crude product in 60g of methanol, filter out undissolved impurities after sufficient dissolution, and perform a second reduced pressure distillation of the methanol solution at 60°C and 200mbar to remove the organic solvent. After the obtained product is stood and dried for a period of time, obtain 13.528g of bishydroxypropylhydroxylamine with a purity of 95.5%, and the yield is 86.59%. The content of sodium ions in the product bishydroxypropylhydroxylamine is <1500ppm.

[0071] Example 3

[0072] Add 16.41g hydroxylamine sulfate, 34g propylene oxide, and 65g water to the reactor, heat to 40°C and mix thoroughly; add 19g of 45% by mass sodium hydroxide aqueous solution, and continue to react for 6h after the addition is complete. After the reaction is completed, perform a reduced pressure distillation at 110°C and 200mbar to remove the solvent water, and after standing and drying for a period of time, obtain 46g of crude product, dissolve the crude product in 60g methanol, filter out undissolved impurities after sufficient dissolution, and perform a second reduced pressure distillation at 40°C and 80mbar to remove the organic solvent. After the obtained product is stood and dried for a period of time, obtain 26.127g of bishydroxypropylhydroxylamine with a purity of 96.5%, and the yield is 84.49%. The content of sodium ions in the product bishydroxypropylhydroxylamine is <2000ppm.

[0073] Example 4

[0074] Add 19.71g hydroxylamine phosphate, 50g propylene oxide, and 77g water to the reactor, heat to 60°C and mix thoroughly; add 80g of 20% by mass sodium hydroxide aqueous solution, and continue to react for 6h after the addition. After the reaction is completed, perform a reduced pressure distillation at 100°C and 100mbar to remove the solvent water, and after standing and drying for a period of time, obtain 58g of crude product, dissolve the crude product in 60g tert-butyl alcohol, filter out undissolved impurities after sufficient dissolution, and perform a second reduced pressure distillation of the tert-butyl alcohol solution at 70°C and 80mbar to remove the organic solvent. After the obtained product is stood and dried for a period of time, 40.968g of dihydroxypropyl hydroxylamine with a purity of 95.8% is obtained, and the yield is 87.68%. The content of sodium phosphate in the product dihydroxypropyl hydroxylamine is sodium ion content <1800ppm.

[0075] Example 5

[0076] Add 6.95g of hydroxylamine hydrochloride, 11.7g of propylene oxide, and 15g of water to the reactor, heat to 60°C and mix thoroughly; add 23g of 30% by mass sodium hydroxide aqueous solution dropwise, and continue to react for 6h after the addition is complete. After the reaction is completed, perform a reduced pressure distillation at 100°C and 100mbar to remove the solvent water, and after standing and drying for a period of time, obtain 21.025g of crude product, dissolve the crude product in 80g of methanol, filter out the undissolved impurities after sufficient dissolution, and perform a second reduced pressure distillation of the methanol solution at 70°C and 200mbar to remove the organic solvent. After the obtained product is stood and dried for a period of time, obtain 12.876g of bishydroxypropylhydroxylamine with a purity of 97.4%, and the yield is 84.06%. The content of sodium ions in the product bishydroxypropylhydroxylamine is <2000ppm.

[0077] Example 6

[0078] The method of Example 1 was followed, except that the mixing temperature was 70° C., 23 g of a 30% by mass sodium hydroxide aqueous solution was added dropwise, and the reaction was continued for 6 hours after the addition was completed.

[0079] The obtained product was dried for a period of time to obtain 13.285 g of bishydroxypropylhydroxylamine with a purity of 90.2% and a yield of 80.32%. The sodium ion content in the product bishydroxypropylhydroxylamine was less than 2000 ppm.

[0080] Example 7

[0081] The method of Example 1 is followed, except that the mass of water used is 50 g.

[0082] The obtained product was dried for a period of time to obtain 14.010 g of bishydroxypropylhydroxylamine with a purity of 89.3% and a yield of 83.85%. The sodium ion content in the product bishydroxypropylhydroxylamine was less than 2000 ppm.

[0083] Comparative Example 1

[0084] Add 6.95g of hydroxylamine hydrochloride and 20g of deionized water to the reactor, and add 17.4g of propylene oxide after being fully mixed and dissolved; control the reaction temperature at 0°C and keep stirring; prepare a 31% by mass NaOH aqueous solution and add it dropwise to the reactor, the amount of which is 12.89g, of which NaOH is 4.0g. The dropwise addition time is 2h, and after the dropwise addition is completed, stir the reaction at 30°C for 10h. Add 0.05% of methyl trioctyl ammonium chloride to the reaction product, the amount of which is 0.02g, and then extract it twice with dichloromethane, each time with an amount of 30mL, combine the extracts, and remove the dichloromethane solvent by vacuum distillation to obtain 13.61g of dihydroxypropyl hydroxylamine, with a purity of 88.60% and a yield of 80.82%.

[0085] By comparing the above embodiments and comparative examples, it can be seen that the method for preparing dihydroxypropylhydroxylamine provided in the embodiment of the present invention can more efficiently remove inorganic salt impurities through a simple method of one vacuum distillation-filtration-second vacuum distillation, the separation process is simple, and the purity and yield of the obtained product are higher.

[0086] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing dihydroxypropylhydroxylamine, characterized in that: The method comprises: (1) mixing propylene oxide, hydroxylamine salt and water; (2) mixing the mixture obtained in step (1) with an inorganic base to react to obtain a mixed product containing dihydroxypropylhydroxylamine; (3) subjecting the mixed product to a first reduced pressure distillation to remove water to obtain a solid intermediate product; (4) dissolving the solid intermediate product in an organic solvent, and then performing solid-liquid separation; Wherein, the organic solvent is selected from at least one of C5-C12 alkanes, C1-C6 alcohols and C3-C6 ketones; (5) The liquid phase obtained by solid-liquid separation is subjected to a second reduced-pressure distillation to remove the organic solvent.

2. The method according to claim 1, wherein: The mixing temperature in step (1) is 40-70°C; Preferably, in step (1), the mass ratio of water to propylene oxide is 0.5-5:1, preferably 0.8-2:1; Preferably, in step (1), the mass ratio of water to hydroxylamine salt is 2-10:1, preferably 2-4:

1.

3. The method according to claim 1 or 2, wherein: The hydroxylamine salt is selected from at least one of hydroxylamine sulfate, hydroxylamine hydrochloride and hydroxylamine phosphate.

4. The method according to any one of claims 1 to 3, wherein: In step (2), the reaction conditions include: reaction temperature of 40-70°C, preferably 55-65°C, and reaction time of 1-8h, preferably 3-6h.

5. The method according to any one of claims 1 to 4, wherein: The inorganic base is provided by an aqueous solution of an inorganic base, and the concentration of the aqueous solution of the inorganic base is 10-45wt%; Preferably, the mass ratio of the hydroxylamine salt to the inorganic base is (0.01-5):1, preferably (1-2):

1.

6. The method according to any one of claims 1 to 5, wherein: The inorganic base is sodium hydroxide and / or potassium hydroxide.

7. The method according to any one of claims 1 to 6, wherein: The conditions of the first reduced pressure distillation include: a pressure of 0-500 mbar, preferably 50-200 mbar; a temperature of 20-150°C, preferably 60-110°C.

8. The method according to any one of claims 1 to 7, wherein: The organic solvent is selected from at least one of n-pentane, n-hexane, n-heptane, acetone, methanol, ethanol, propanol, n-butanol, isobutanol and cyclohexanol; Preferably, the mass ratio of the organic solvent to the solid intermediate product is 0.5-10:1, preferably 1-4:

1.

9. The method according to any one of claims 1 to 8, wherein: The conditions of the second reduced pressure distillation include: pressure of 0-500 mbar, preferably 50-200 mbar; temperature of 20-140°C, preferably 30-100°C.

10. A reaction system for preparing dihydroxypropylhydroxylamine, comprising: A reactor (11), a primary vacuum distillation device (12), a solid-liquid separator (13) and a secondary vacuum distillation device (14) connected in sequence; The reactor (11) is provided with a first raw material inlet (1) and a second raw material inlet (2), propylene oxide, hydroxylamine salt and water are fed into the reactor (11) through the first raw material inlet (1), and the inorganic base is fed into the reactor (11) through the second raw material inlet (2); The primary vacuum distillation device (12) is provided with a mixed product inlet (3) and an organic solvent inlet (5), and is used to perform a first vacuum distillation to remove water from the mixed product containing dihydroxypropylhydroxylamine from the reactor (11), and then mix the mixed product with the organic solvent fed into the primary vacuum distillation device (12) through the organic solvent inlet (5); The solid-liquid separator (13) is used to separate the solid and liquid of the product from the primary vacuum distillation device (12), and the obtained liquid phase is sent to the secondary vacuum distillation device (14) for a second vacuum distillation to remove the organic solvent.

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