A method for continuously producing 3-amino-1,2-propanediol

Abstract

The present invention discloses a method for continuously producing 3-amino-1,2-propanediol, specifically relating to the technical field of producing 3-amino-1,2-propanediol. (1) Ammonolysis reaction; (2) Evaporation and recovery; (3) Coarse distillation and rectification. Beneficial effects: The present invention provides a method for continuously producing 3-amino-1,2-propanediol, which improves the product quality, simplifies the production process of 3-amino-1,2-propanediol, greatly reduces the production cost, by-produces high-value 2-amino-1,3-propanediol and 1,3-diamino-2-propanol (DAP) while synthesizing 3-amino-1,2-propanediol, without low-value by-products, and has good overall economic benefits.

Description

Technical Field

[0001] The patent of this invention relates to the technical field of producing 3-amino-1,2-propylene glycol, and specifically to a method for continuously producing 3-amino-1,2-propylene glycol. Background Art

[0002] 3-Amino-1,2-propanediol, molecular formula C 3 H 9 NO 2 , CAS NO: 616-30-8, boiling point 264-265℃, 3-amino-1,2-propanediol is a pharmaceutical intermediate, mainly used as a synthetic raw material for water-soluble, non-ionic X-CT contrast agents iohexol (i.e., Omnipaque), ioflurane, and iodixanol. Uses of iohexol and other series products: Diagnostic drugs, non-ionic water-soluble triiodine ring X-ray diagnosis positive contrast agents, which can absorb more X-rays than surrounding tissue structures after entering the body, thus forming a contrast on the X-ray image. It shows the contour of the lumen and the morphology of its internal structure, and is a commonly used drug in various hospitals. Among them, publication number CN104130140B discloses a method patent for synthesizing 3-amino-1,2-propylene glycol using a continuous reaction device. The process mixes 3-chloro-1,2-propylene glycol with ammonia water for aminolysis, then adds sodium hydroxide to neutralize 3-amino-1,2-propylene glycol hydrochloride, and finally obtains 3-amino-1,2-propylene glycol through deamination and desalination. The above process has the following problems: 1. The above process directly mixes 3-chloro-1,2-propylene glycol with ammonia water for aminolysis. Since the activity of primary amine is lower than that of secondary amine and tertiary amine, about 5% of conjugates will be produced, which are generally sold as by-product amino alcohols and have low commercial value. 2. The above process requires the addition of sodium hydroxide to neutralize 3-amino-1,2-propylene glycol hydrochloride, so a large amount of sodium chloride will be produced as a by-product, and a subsequent crystallization and desalination process is required. The process is cumbersome and the production cost is high. Summary of the invention

[0003] The object of the present invention is to provide a method for continuously producing 3-amino-1,2-propanediol which simplifies the production process and improves the product yield.

[0004] The purpose of the present invention is implemented by the following technical scheme: a method for continuously producing 3-amino-1,2-propanediol, which comprises the following steps in sequence:

[0005] (1) Ammonolysis reaction: Ammonia water with a concentration of 40% to 60%, glycerol and hydrogen are mixed in a mixer at a molar ratio of 15-20:1:4-6, and then continuously sent to a fixed bed tubular reactor to react under the action of a palladium carbon catalyst at a reaction temperature of 70-90°C and a reaction pressure of 5-7MPa to obtain a reaction mixture; wherein the glycerol is refined glycerol.

[0006] The specific reaction equation of the aminolysis reaction is as follows:

[0007]

[0008] (2) Evaporation recovery: the reaction mixture obtained in step (1) is subjected to a pressure reducing device to reduce its pressure to 0.35-0.45 MPa, and then continuously heated and evaporated at a heating temperature of 110-130° C. for a continuous heating and evaporation time of 30-60 min to obtain an evaporation mother liquor;

[0009] (3) crude distillation: crude distillation and distillation of the evaporated mother liquor obtained in step (2) to obtain by-product 1,3-diamino-2-propanol, by-product 2-amino-1,2-propanediol and product 3-amino-1,2-propanediol.

[0010] Furthermore, in step (2), the specific evaporation process is as follows:

[0011] a. Send the decompressed reaction mixture to a primary falling film evaporator for heating and evaporation at a temperature of 110-120°C and an evaporation time of 10-30 min to obtain a primary concentrated liquid and a mixed gas A;

[0012] b. Send the primary concentrated liquid in step a to a secondary thin film evaporator for heating and evaporation at a heating temperature of 120-130° C. for an evaporation time of 20-30 min to obtain the evaporation mother liquid and mixed gas B.

[0013] Furthermore, after the mixed gas A in step a is condensed by the first condenser, the non-condensable gas passes through the first absorption tower, the second absorption tower and the third absorption tower in sequence to absorb ammonia. After the mixed gas B in step b is condensed by the second condenser, the non-condensable gas passes through the second absorption tower and the third absorption tower in sequence to absorb ammonia. The hydrogen discharged from the third absorption tower is compressed by the compressor and then returned to the mixer.

[0014] Furthermore, the ammonia water discharged from the tertiary absorption tower and the condensed water discharged from the second condenser are sprayed down from the top of the secondary absorption tower as absorption liquid; the ammonia water discharged from the secondary absorption tower and the condensed water discharged from the first condenser are sprayed down from the top of the primary absorption tower as absorption liquid; the ammonia water discharged from the primary absorption tower returns to the mixer to participate in the reaction.

[0015] Furthermore, the crude distillation conditions in step (3) are: distillation temperature is 155-175° C., and distillation time is 30-70 min.

[0016] Furthermore, the distillation process in step (3) is as follows: when the distillation pressure reaches 10Pa-200Pa and the distillation temperature reaches 90-100°C, the reflux ratio is set to 20:5, and the by-product 1,3-diamino-2-propanol is produced; when the temperature reaches 100-110°C, the reflux ratio is set to 20:1, and the by-product 2-amino-1,2-propanediol is produced; when the temperature reaches 110-130°C, the reflux ratio is set to 10:8, and the product 3-amino-1,2-propanediol is produced. When the temperature reaches 131-135°C, the production is stopped and the kettle residue is discharged.

[0017] Advantages of the present invention:

[0018] 1. The present invention provides a method for continuously producing 3-amino-1,2-propylene glycol, wherein ammonia water with a concentration of 40% to 60% and glycerol are mixed in proportion, and 3-amino-1,2-propylene glycol is synthesized in one step under the action of palladium-carbon catalysis, and then the 3-amino-1,2-propylene glycol product can be obtained only through the steps of evaporation, rough steaming and rectification, thereby improving the quality of the product.

[0019] 2. The present invention provides a method for continuously producing 3-amino-1,2-propylene glycol, which does not require the use of sodium hydroxide for neutralization, thus avoiding the generation of sodium chloride. At the same time, it does not require a crystallization and desalting process, thus simplifying the production process of 3-amino-1,2-propylene glycol and greatly reducing the production cost.

[0020] 3. The present invention provides a method for continuously producing 3-amino-1,2-propanediol, which produces high-value 2-amino-1,3-propanediol and 1,3-diamino-2-propanol (DAP) as by-products while synthesizing 3-amino-1,2-propanediol, has no low-value by-products, and has good overall economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a process system diagram of the present invention.

[0023] Mixer 1, primary fixed bed tubular reactor 2, secondary fixed bed tubular reactor 3, pressure reducing device 4, primary falling film evaporator 5, secondary thin film evaporator 6, first condenser 7, primary absorption tower 8, secondary absorption tower 9, tertiary absorption tower 10, second condenser 11, compressor 12, crude distillation kettle 13, distillation kettle 14. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below by way of examples.

[0025] Example 1: Figure 1 As shown, a method for continuously producing 3-amino-1,2-propanediol comprises the following steps in sequence:

[0026] (1) Ammonolysis reaction: hydrogen is introduced into a fixed-bed tubular reactor containing a palladium-carbon catalyst until the reactor pressure reaches 5 MPa, the reactor jacket heating system is turned on, the temperature is raised to 70°C, an ammonia water feed pump with a concentration of 40%-60% is turned on, the ammonia water feed flow rate is adjusted to 1 m³ / h, the hydrogen gas inlet regulating valve group is turned on, the hydrogen gas inlet flow rate is adjusted to 1.5 L / min, the glycerol feed pump is turned on, the glycerol feed flow rate is adjusted to 100 L / h, and the glycerol and ammonia water are mixed in the mixer 1 and then enter the primary fixed-bed tubular reactor 2 for reaction, and then continue to enter the secondary fixed-bed tubular reactor 3 for reaction, and the temperature of the secondary fixed-bed tubular reactor 3 is controlled to be 80°C for reaction to obtain a reaction mixture;

[0027] (2) Evaporation recovery: the reaction mixture obtained in step (1) is passed through a pressure reducing device 4 to reduce its pressure to 0.4 MPa, and then continuously heated and evaporated to obtain an evaporation mother liquor;

[0028] The specific evaporation process is as follows:

[0029] a. Send the decompressed reaction mixture to a primary falling film evaporator 5 for heating and evaporation at a temperature of 110-120° C. for an evaporation time of 10-30 min to obtain a primary concentrated liquid and a mixed gas A;

[0030] b. Send the primary concentrated liquid in step a to the secondary thin film evaporator 6 for heating and evaporation at a heating temperature of 120-130° C. for an evaporation time of 20-30 min to obtain an evaporation mother liquid and a mixed gas B.

[0031] Among them, after the mixed gas A in step a is condensed by the first condenser 7, the non-condensable gas passes through the primary absorption tower 8, the secondary absorption tower 9 and the tertiary absorption tower 10 in sequence to absorb ammonia. After the mixed gas B in step b is condensed by the second condenser 11, the non-condensable gas passes through the secondary absorption tower 9 and the tertiary absorption tower 10 in sequence to absorb ammonia. The hydrogen discharged from the tertiary absorption tower 10 is compressed by the compressor 12 and then returned to the mixer 1. The ammonia water discharged from the tertiary absorption tower 10 and the condensed water discharged from the second condenser 11 are sprayed down from the upper part of the secondary absorption tower 9 as absorption liquid; the ammonia water discharged from the secondary absorption tower 9 and the condensed water discharged from the first condenser 7 are sprayed down from the upper part of the primary absorption tower 8 as absorption liquid; the ammonia water discharged from the primary absorption tower 8 returns to the mixer 1 to participate in the reaction.

[0032] (3) crude distillation: the evaporation mother liquor obtained in step (2) is crudely distilled in a crude distillation kettle 13, wherein the crude distillation conditions are: distillation temperature of 155-175°C, and distillation time of 30-70min; distillation is carried out in a distillation kettle 14, when the distillation pressure reaches 10Pa-200Pa and the distillation temperature reaches 90-100°C, the reflux ratio is set to 20:5, and the by-product 1,3-diamino-2-propanol is produced; when the temperature reaches 100-110°C, the reflux ratio is set to 20:1, and the by-product 2-amino-1,2-propanediol is produced; when the temperature reaches 110-130°C, the reflux ratio is set to 10:8, and the by-product 1,3-diamino-2-propanol is produced. The product 3-amino-1,2-propanediol is produced. When the temperature reaches 131-135°C, the production is stopped and the kettle residue is discharged. The production capacity of the product 3-amino-1,2-propanediol is 96kg / h, the purity is 99.5%, and the yield is 70%. The purity of the by-product 2-amino-1,3-propanediol is 99.5%, and the yield is 11.2%. The purity of the by-product 1,3-diamino-2-propanol (DAP) is 99.3%, and the yield is 15.9%. The yield of the product 3-amino-1,2-propanediol is guaranteed while producing high-value 2-amino-1,3-propanediol and 1,3-diamino-2-propanol (DAP).

[0033] Example 2: Figure 1 As shown, a method for continuously producing 3-amino-1,2-propanediol comprises the following steps in sequence:

[0034] (1) Ammonolysis reaction: hydrogen is introduced into a fixed-bed tubular reactor containing a palladium-carbon catalyst until the reactor pressure reaches 5 MPa, the reactor jacket heating system is turned on, the temperature is raised to 75°C, an ammonia water feed pump with a concentration of 40%-60% is turned on, the ammonia water feed flow rate is adjusted to 1 m³ / h, the hydrogen gas inlet regulating valve group is turned on, the hydrogen gas inlet flow rate is adjusted to 2.0 L / min, the glycerol feed pump is turned on, the glycerol feed flow rate is adjusted to 100 L / h, and the glycerol and ammonia water are mixed in the mixer 1 and then enter the primary fixed-bed tubular reactor 2 for reaction, and then continue to enter the secondary fixed-bed tubular reactor 3 for reaction, and the temperature of the secondary fixed-bed tubular reactor 3 is controlled to be 85°C for reaction to obtain a reaction mixture;

[0035] (2) Evaporation recovery: the reaction mixture obtained in step (1) is passed through a pressure reducing device 4 to reduce its pressure to 0.4 MPa, and then continuously heated and evaporated to obtain an evaporation mother liquor;

[0036] The specific evaporation process is as follows:

[0037] a. Send the decompressed reaction mixture to a primary falling film evaporator 5 for heating and evaporation at a temperature of 110-120° C. for an evaporation time of 10-30 min to obtain a primary concentrated liquid and a mixed gas A;

[0038] b. Send the primary concentrated liquid in step a to the secondary thin film evaporator 6 for heating and evaporation at a heating temperature of 120-130° C. for an evaporation time of 20-30 min to obtain an evaporation mother liquid and a mixed gas B.

[0039] Among them, after the mixed gas A in step a is condensed by the first condenser 7, the non-condensable gas passes through the primary absorption tower 8, the secondary absorption tower 9 and the tertiary absorption tower 10 in sequence to absorb ammonia. After the mixed gas B in step b is condensed by the second condenser 11, the non-condensable gas passes through the secondary absorption tower 9 and the tertiary absorption tower 10 in sequence to absorb ammonia. The hydrogen discharged from the tertiary absorption tower 10 is compressed by the compressor 12 and then returned to the mixer 1. The ammonia water discharged from the tertiary absorption tower 10 and the condensed water discharged from the second condenser 11 are sprayed down from the upper part of the secondary absorption tower 9 as absorption liquid; the ammonia water discharged from the secondary absorption tower 9 and the condensed water discharged from the first condenser 7 are sprayed down from the upper part of the primary absorption tower 8 as absorption liquid; the ammonia water discharged from the primary absorption tower 8 returns to the mixer 1 to participate in the reaction.

[0040] (3) crude distillation: the evaporation mother liquor obtained in step (2) is crudely distilled in a crude distillation kettle 13, wherein the crude distillation conditions are: distillation temperature of 155-175°C, and distillation time of 30-70min; distillation is carried out in a distillation kettle 14, when the distillation pressure reaches 10Pa-200Pa and the distillation temperature reaches 90-100°C, the reflux ratio is set to 20:5, and the by-product 1,3-diamino-2-propanol is produced; when the temperature reaches 100-110°C, the reflux ratio is set to 20:1, and the by-product 2-amino-1,2-propanediol is produced; when the temperature reaches 110-130°C, the reflux ratio is set to 10:8, and the by-product 1,3-diamino-2-propanol is produced. The product 3-amino-1,2-propanediol is produced. When the temperature reaches 131-135°C, the production is stopped and the kettle residue is discharged. The production capacity of the product 3-amino-1,2-propanediol is 93kg / h, the purity is 99.5%, and the yield is 69%. The purity of the by-product 2-amino-1,3-propanediol is 99.3%, and the yield is 11.7%. The purity of the by-product 1,3-diamino-2-propanol (DAP) is 99.2%, and the yield is 16.5%. The yield of the product 3-amino-1,2-propanediol is guaranteed while producing high-value 2-amino-1,3-propanediol and 1,3-diamino-2-propanol (DAP).

[0041] Example 3: Figure 1 As shown, a method for continuously producing 3-amino-1,2-propanediol comprises the following steps in sequence:

[0042] (1) Ammonolysis reaction: hydrogen is introduced into a fixed bed tubular reactor containing a palladium carbon catalyst until the reactor pressure reaches 5 MPa, the reactor jacket heating system is turned on, the temperature is raised to 80°C, an ammonia water feed pump with a concentration of 40%-60% is turned on, the ammonia water feed flow rate is adjusted to 1.5 m³ / h, the hydrogen gas inlet regulating valve group is turned on, the hydrogen gas inlet flow rate is adjusted to 1.0 L / min, the glycerol feed pump is turned on, the glycerol feed flow rate is adjusted to 100 L / h, and the glycerol and ammonia water are mixed in the mixer 1 and then enter the primary fixed bed tubular reactor 2 for reaction, and then continue to enter the secondary fixed bed tubular reactor 3 for reaction, and the temperature of the secondary fixed bed tubular reactor 3 is controlled to be 90°C for reaction to obtain a reaction mixture;

[0043] (2) Evaporation recovery: the reaction mixture obtained in step (1) is passed through a pressure reducing device 4 to reduce its pressure to 0.4 MPa, and then continuously heated and evaporated to obtain an evaporation mother liquor;

[0044] The specific evaporation process is as follows:

[0045] a. Send the decompressed reaction mixture to a primary falling film evaporator 5 for heating and evaporation at a temperature of 110-120° C. for an evaporation time of 10-30 min to obtain a primary concentrated liquid and a mixed gas A;

[0046] b. Send the primary concentrated liquid in step a to the secondary thin film evaporator 6 for heating and evaporation at a heating temperature of 120-130° C. for an evaporation time of 20-30 min to obtain an evaporation mother liquid and a mixed gas B.

[0047] Among them, after the mixed gas A in step a is condensed by the first condenser 7, the non-condensable gas passes through the primary absorption tower 8, the secondary absorption tower 9 and the tertiary absorption tower 10 in sequence to absorb ammonia. After the mixed gas B in step b is condensed by the second condenser 11, the non-condensable gas passes through the secondary absorption tower 9 and the tertiary absorption tower 10 in sequence to absorb ammonia. The hydrogen discharged from the tertiary absorption tower 10 is compressed by the compressor 12 and then returned to the mixer 1. The ammonia water discharged from the tertiary absorption tower 10 and the condensed water discharged from the second condenser 11 are sprayed down from the upper part of the secondary absorption tower 9 as absorption liquid; the ammonia water discharged from the secondary absorption tower 9 and the condensed water discharged from the first condenser 7 are sprayed down from the upper part of the primary absorption tower 8 as absorption liquid; the ammonia water discharged from the primary absorption tower 8 returns to the mixer 1 to participate in the reaction.

[0048] (3) Rough distillation: The evaporation mother liquor obtained in step (2) is crudely distilled in a crude distillation kettle 13 in turn, wherein the crude distillation conditions are: distillation temperature of 155-175°C, and distillation time of 30-70 min; distillation is carried out in a distillation kettle 14, when the distillation pressure reaches 10Pa-200Pa and the distillation temperature reaches 90-100°C, the reflux ratio is set to 20:5, and the by-product 1,3-diamino-2-propanol is produced; when the temperature reaches 100-110°C, the reflux ratio is set to 20:1, and the by-product 2-amino-1,2-propanediol is produced; when the temperature reaches 110-130°C, the reflux ratio is set to 10:8, and the product 3 is produced. -amino-1,2-propanediol. When the temperature reaches 131-135℃, the extraction is stopped and the kettle residue is discharged. The production capacity of the product 3-amino-1,2-propanediol is 105kg / h, the purity is 99.5%, and the yield is 83%. The purity of the by-product 2-amino-1,3-propanediol recovered by crude distillation and rectification is 99.6%, and the yield is 6.2%. The purity of the by-product 1,3-diamino-2-propanol (DAP) is 99.1%, and the yield is 8.7%. The yield of the product 3-amino-1,2-propanediol is guaranteed while producing high-value 2-amino-1,3-propanediol and 1,3-diamino-2-propanol (DAP).

[0049] The method for synthesizing 3-amino-1,2-propylene glycol using a continuous reaction device disclosed in the prior art CN104130140B produces 300 kg of by-product amino alcohol when producing 1 ton of 3-amino-1,2-propylene glycol, and the selling price of amino alcohol is 0.9 yuan / kg; the production of 1 ton of 3-amino-1,2-propylene glycol in Example 1 of the present invention produces 15.8 kg of by-product 2-amino-1,3-propylene glycol and 22.2 kg of by-product 1,3-diamino-2-propanol (DAP), and 2-amino-1,3-propylene glycol is 15.8 kg of by-product 2-amino-1,3-propylene glycol and 22.2 kg of by-product 1,3-diamino-2-propanol (DAP). The selling price of diol is 180 yuan / kg, and the selling price of 1,3-diamino-2-propanol (DAP) is 1200 yuan / kg; therefore, Example 1 of the present invention produces 1 ton of 3-amino-1,2-propanediol, and the income of by-products is 29484 yuan, while the income of by-products in the prior art is only 900 yuan. Furthermore, the method of the present invention produces high-value 2-amino-1,3-propanediol and 1,3-diamino-2-propanol (DAP) as by-products while synthesizing 3-amino-1,2-propanediol, without low-value by-products, and has good overall economic benefits.

[0050] The above are preferred embodiments of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for continuously producing 3-amino-1,2-propanediol, characterized in that: It includes the following steps in sequence: (1) Ammonolysis reaction: Ammonia water with a concentration of 40%-60%, glycerol and hydrogen are mixed in a mixer at a molar ratio of 15-20:1:4-6, and then continuously sent to a fixed bed tubular reactor to react under the action of a palladium carbon catalyst at a reaction temperature of 70-90°C and a reaction pressure of 5-7MPa to obtain a reaction mixture; (2) Evaporation recovery: the reaction mixture obtained in step (1) is subjected to a pressure reducing device to reduce its pressure to 0.35-0.45 MPa, and then continuously heated and evaporated at a heating temperature of 110-130° C. for a continuous heating and evaporation time of 30-60 min to obtain an evaporation mother liquor; (3) crude distillation: crude distillation and distillation of the evaporated mother liquor obtained in step (2) to obtain by-product 1,3-diamino-2-propanol, by-product 2-amino-1,2-propanediol and product 3-amino-1,2-propanediol.

2. The method for continuous production of 3-amino-1,2-propanediol according to claim 1, characterized in that: In step (2), the specific evaporation process is as follows: a. Send the decompressed reaction mixture to a primary falling film evaporator for heating and evaporation at a temperature of 110-120°C and an evaporation time of 10-30 min to obtain a primary concentrated liquid and a mixed gas A; b. Send the primary concentrated liquid in step a to a secondary thin film evaporator for heating and evaporation at a heating temperature of 120-130° C. for an evaporation time of 20-30 min to obtain the evaporation mother liquid and mixed gas B.

3. The method for continuous production of 3-amino-1,2-propanediol according to claim 2, characterized in that: After the mixed gas A in step a is condensed by the first condenser, the non-condensable gas passes through the primary absorption tower, the secondary absorption tower and the tertiary absorption tower in sequence to absorb ammonia. After the mixed gas B in step b is condensed by the second condenser, the non-condensable gas passes through the secondary absorption tower and the tertiary absorption tower in sequence to absorb ammonia. The hydrogen discharged from the tertiary absorption tower is compressed by the compressor and then returned to the mixer.

4. The method for continuous production of 3-amino-1,2-propanediol according to claim 3, characterized in that: The ammonia water discharged from the tertiary absorption tower and the condensed water discharged from the second condenser are sprayed down from the top of the secondary absorption tower as absorption liquid; the ammonia water discharged from the secondary absorption tower and the condensed water discharged from the first condenser are sprayed down from the top of the primary absorption tower as absorption liquid; the ammonia water discharged from the primary absorption tower returns to the mixer to participate in the reaction.

5. The method for continuous production of 3-amino-1,2-propanediol according to claim 1, characterized in that: The crude distillation conditions in step (3) are: distillation temperature is 155-175°C, and distillation time is 30-70min.

6. The method for continuous production of 3-amino-1,2-propanediol according to claim 1, characterized in that: The distillation process in step (3) is as follows: when the distillation pressure reaches 10Pa-200Pa and the distillation temperature reaches 90-100°C, the reflux ratio is set to 20:5, and the by-product 1,3-diamino-2-propanol is produced; when the temperature reaches 100-110°C, the reflux ratio is set to 20:1, and the by-product 2-amino-1,2-propanediol is produced; when the temperature reaches 110-130°C, the reflux ratio is set to 10:8, and the product 3-amino-1,2-propanediol is produced. When the temperature reaches 131-135°C, the production is stopped and the kettle residue is discharged.

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