A preparation method of 1,4-butanediamine

Abstract

The present invention relates to the technical field of organic synthesis, and in particular to a preparation method of 1,4-butylene diamine, wherein the preparation method is: S1, adipic acid is heated and melted, and adipic acid in a molten state and ammonia are subjected to an aminating reaction; S2, after the aminating reaction is terminated, the temperature is raised to carry out a dehydration reaction, and byproduct water and unreacted ammonia enter a recovery device through a condensing system, and a dehydration reaction obtains adipic acid diamine; S3, after the dehydration reaction is terminated, a hypohalite aqueous solution and an alkali are added, and the reaction is heated to react, and after the reaction is terminated, 1,4-butylene diamine products are obtained by post-processing purification. The preparation method of 1,4-butylene diamine of the present invention has good selectivity, and the obtained 1,4-butylene diamine has a purity of more than 99.5%, and a yield of more than 90%. The preparation method of the present invention is simple to operate, and the raw material price is cheap, the reaction conditions are mild, the risk factor is small, and it is convenient for industrialized production.

Description

Technical Field

[0001] The invention relates to a method for preparing 1,4-butanediamine, and belongs to the technical field of organic synthesis. Background Art

[0002] 1,4-Butanediamine, also known as putrescine or 1,4-diaminobutane, is a colorless crystal or colorless to slightly yellow liquid at room temperature with a strong pungent odor. It is an important organic synthesis intermediate and biochemical precursor, and is widely used in medicine, nylon plastics, pesticides and biological fields. With the continuous advancement of science and technology, the demand for downstream products of 1,4-butanediamine has increased year by year. It is of great significance to study the preparation method of green, efficient and highly selective 1,4-butanediamine.

[0003] The preparation methods of 1,4-butanediamine include biological method and chemical method. The biological method has the disadvantages of harsh microbial culture conditions, expensive enzymes, low production efficiency, etc., which makes it difficult to carry out industrial production. Therefore, the industrial production of 1,4-butanediamine mainly relies on chemical methods. The existing chemical methods include succinonitrile method, 1,4-butanediol method, succinic acid method, etc.

[0004] The most common chemical synthesis method is the catalytic hydrogenation of succinonitrile. The method disclosed in the patent application with publication number CN1745059A is: a catalytic hydrogenation method of succinonitrile in the presence of a Raney-type catalyst in contact with a hydroxide and rinsed and an amine. The reaction pressure is 20 MPa, the risk factor is relatively high, and the hydrogenation catalyst treatment process is cumbersome.

[0005] The patent application with publication number CN103502199A provides a phosphorus donor ligand ruthenium catalyst, which can be used for alcohol amination reaction of 1,4-butanediol and ammonia while removing water, but the product selectivity is only 35-40%, and the catalyst used is expensive.

[0006] The patent application with publication number CN114539070A discloses a method for preparing 1,4-butanediamine from 1,4-butanediic acid, wherein 1,4-butanediic acid is used as the initial raw material, and first, 1,4-butanediic acid and methanol undergo esterification reaction under an acid catalyst to generate dimethyl succinate, and dimethyl succinate undergoes catalytic hydrogenation reaction to generate 1,4-butanediol, and 1,4-butanediol and ammonia undergo hydroamination under the condition of a reductive amination catalyst to generate 1,4-butanediamine. The process operation steps are cumbersome, the preparation process of the reductive amination catalyst is complicated, the hydroamination reaction pressure is 5~20MPa, the hydroamination reaction temperature is 140~200℃, and the risk factor is relatively high. Summary of the invention

[0007] The invention aims at the deficiencies in the prior art and provides a method for preparing 1,4-butanediamine. The method is simple to operate, can obtain a high-yield, high-purity product, has low raw material prices, mild reaction conditions, low risk factors, and is convenient for industrial production.

[0008] The technical solution of the present invention to solve the above technical problems is as follows: a method for preparing 1,4-butanediamine, the preparation method comprising:

[0009] S1, heating and melting adipic acid, and reacting the molten adipic acid with ammonia for an amination reaction;

[0010] S2. After the amination reaction is completed, the temperature is raised to carry out a dehydration reaction to obtain adipic acid diamide;

[0011] S3. After the dehydration reaction is completed, a hypohalite aqueous solution and a base are added and heated to react. After the reaction is completed, 1,4-butanediamine product is obtained through post-treatment and purification.

[0012] Furthermore, in step S1, in an inert gas environment, the adipic acid is melted by heating to 160-180° C., and ammonia is introduced to maintain the pressure at 160-180° C. to react.

[0013] Furthermore, the introduction pressure of the ammonia gas is 0.8-1.2 MPa, and the amination reaction time is 1-3 h.

[0014] Furthermore, in step S2, the dehydration reaction temperature is 210-230° C., and the dehydration reaction time is 4-8 h.

[0015] Furthermore, in step S3, the heating temperature is 60-100° C. and the reaction time is 2-6 h.

[0016] Furthermore, in step S3, the hypohalite is at least one of sodium hypochlorite, sodium hypobromite, potassium hypochlorite and potassium hypobromite.

[0017] Furthermore, the base is at least one of sodium hydroxide and potassium hydroxide.

[0018] Furthermore, in step S3, the mass concentration of the hypohalite aqueous solution is ≥10%.

[0019] Furthermore, the amount of the hypohalite is 2 to 4 times the molar amount of adipic acid, and the amount of the base is 4 to 8 times the molar amount of adipic acid.

[0020] Furthermore, in step S3, after the reaction is completed, atmospheric distillation is performed to collect the fraction between 158-160° C., which is the 1,4-butanediamine.

[0021] The beneficial effects of the present invention are:

[0022] (1) The preparation method of the present invention uses cheap adipic acid as the initial raw material and does not require the use of expensive catalysts, thereby solving the problem of high production cost of 1,4-butanediamine.

[0023] (2) The preparation method of the present invention has mild reaction conditions, simple operation, easy control, low risk factor, and is convenient for industrial production.

[0024] (3) The method for preparing 1,4-butanediamine of the present invention has high selectivity. The purity of the prepared 1,4-butanediamine is above 99.5% and the yield is above 90%. DETAILED DESCRIPTION

[0025] The specific implementation of the present invention is described in detail below. The present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used are only for describing specific embodiments and are not intended to limit the present invention.

[0027] A method for preparing 1,4-butanediamine, the preparation method comprising:

[0028] S1, heating and melting adipic acid, and reacting the molten adipic acid with ammonia for an amination reaction;

[0029] S2. After the amination reaction is completed, the temperature is raised to carry out a dehydration reaction to obtain adipic acid diamide;

[0030] S3. After the dehydration reaction is completed, a hypohalite aqueous solution and a base are added and heated to react. After the reaction is completed, 1,4-butanediamine product is obtained through post-treatment and purification.

[0031] Specifically, the specific operation of step S1 is to add adipic acid into a reactor, evacuate the reactor and introduce nitrogen repeatedly for more than 5 times to protect the adipic acid in an inert gas, then heat the reactor to 160-180° C. to melt the adipic acid, and introduce sufficient ammonia to carry out an amination reaction.

[0032] Specifically, the ammonia gas introduction pressure is 0.8-1.2 MPa, and the amination reaction time is 1-3 h.

[0033] More specifically, during the actual production and preparation, when the reaction of step S1 is carried out, ammonia gas of a certain pressure is introduced into the reactor, and the pressure in the reactor is observed by a pressure gauge. When the pressure in the reactor remains unchanged, it can be determined that the amination reaction is complete.

[0034] Specifically, in step S2, the dehydration reaction temperature is 210-230° C., and the dehydration reaction time is 4-8 hours.

[0035] More specifically, in step S2, when the temperature is raised to carry out the dehydration reaction, during the reaction, the by-product water and unreacted ammonia in the system enter the recovery device through the condensation system.

[0036] Specifically, in step S3, the heating temperature is 60-100° C. and the reaction time is 2-6 hours.

[0037] Specifically, in step S3, the hypohalite is at least one of sodium hypochlorite, sodium hypobromite, potassium hypochlorite and potassium hypobromite.

[0038] Specifically, the base is at least one of sodium hydroxide and potassium hydroxide.

[0039] Specifically, in step S3, the mass concentration of the hypohalite aqueous solution is ≥10%.

[0040] Specifically, the amount of the hypohalite is 2 to 4 times the molar amount of adipic acid, and the amount of the base is 4 to 8 times the molar amount of adipic acid.

[0041] Specifically, in step S3, after the reaction is completed, atmospheric distillation is performed to collect the fraction between 158-160° C., which is the 1,4-butanediamine.

[0042] Taking the hypochlorite in step S3 as sodium hypochlorite and the alkali as sodium hydroxide as an example, the principle of the preparation method of 1,4-butanediamine is as follows:

[0043] .

[0044] Example 1

[0045] A method for preparing 1,4-butanediamine is as follows:

[0046] (1) Weigh 1 mol of adipic acid and add it to a reactor. Evacuate the reactor and introduce nitrogen for more than 5 times to protect the adipic acid in an inert gas. Then, heat the reactor to 170° C. to melt the adipic acid. Then introduce sufficient ammonia to carry out an amination reaction. The pressure is 1.0 MPa and the amination reaction time is 2 h.

[0047] (2) After the amination reaction is completed, the temperature is raised to 230°C for dehydration reaction and kept at this temperature for 6 hours. The by-product water and unreacted ammonia enter the recovery device through the condensation system. After the heat preservation is completed, adipic acid diamide is obtained;

[0048] (3) After the dehydration reaction is completed, add 993 g of sodium hypochlorite aqueous solution (mass concentration 15%, containing 2 mol of sodium hypochlorite) and 4 mol of sodium hydroxide, raise the temperature to 80°C, and keep the temperature for 4 hours;

[0049] (4) After the reaction is completed, atmospheric distillation is performed to collect the fraction between 158 and 160° C., which is the 1,4-butanediamine with a GC purity of 99.7% and a yield of 94%.

[0050] Example 2

[0051] A method for preparing 1,4-butanediamine is as follows:

[0052] (1) Weigh 1 mol of adipic acid and add it to a reactor. Evacuate the reactor and introduce nitrogen for more than 5 times to protect the adipic acid in an inert gas. Then, heat the reactor to 180° C. to melt the adipic acid. Then introduce sufficient ammonia to carry out an amination reaction. The pressure is 1.2 MPa and the amination reaction time is 1 h.

[0053] (2) After the amination reaction is completed, the temperature is raised to 210°C for dehydration reaction and kept at this temperature for 8 hours. The by-product water and unreacted ammonia enter the recovery device through the condensation system. After the heat preservation is completed, adipic acid diamide is obtained;

[0054] (3) After the dehydration reaction is completed, add 1904 g of sodium hypobromite aqueous solution (mass concentration 25%, containing 4 mol of sodium hypobromite) and 6 mol of sodium hydroxide, raise the temperature to 100 ° C, and keep the temperature for 2 hours;

[0055] (4) After the reaction is completed, atmospheric distillation is performed to collect the fraction between 158 and 160° C., which is the 1,4-butanediamine with a GC purity of 99.8% and a yield of 93%.

[0056] Example 3

[0057] A method for preparing 1,4-butanediamine is as follows:

[0058] (1) Weigh 1 mol of adipic acid and add it to a reactor. Evacuate the reactor and introduce nitrogen for more than 5 times to protect the adipic acid in an inert gas. Then, heat the reactor to 160° C. to melt the adipic acid. Then introduce sufficient ammonia to carry out an amination reaction. The pressure is 1.0 MPa and the amination reaction time is 3 h.

[0059] (2) After the amination reaction is completed, the temperature is raised to 230°C for dehydration reaction and kept at this temperature for 4 hours. The by-product water and unreacted ammonia enter the recovery device through the condensation system. After the heat preservation is completed, adipic acid diamide is obtained;

[0060] (3) After the dehydration reaction is completed, add 1811 g of potassium hypochlorite aqueous solution (mass concentration 10%, containing 2 mol of potassium hypochlorite) and 8 mol of potassium hydroxide, raise the temperature to 60°C, and keep the temperature for 6 hours;

[0061] (4) After the reaction is completed, atmospheric distillation is performed to collect the fraction between 158 and 160° C., which is the 1,4-butanediamine with a GC purity of 99.7% and a yield of 95%.

[0062] Example 4

[0063] A method for preparing 1,4-butanediamine is as follows:

[0064] (1) Weigh 1 mol of adipic acid and add it to a reactor. Evacuate the reactor and introduce nitrogen for more than 5 times to protect the adipic acid in an inert gas. Then, heat the reactor to 170° C. to melt the adipic acid. Then introduce sufficient ammonia to carry out an amination reaction. The pressure is 1.0 MPa and the amination reaction time is 2 h.

[0065] (2) After the amination reaction is completed, the temperature is raised to 220°C for dehydration reaction and kept at this temperature for 4 hours. The by-product water and unreacted ammonia enter the recovery device through the condensation system. After the heat preservation is completed, adipic acid diamide is obtained;

[0066] (3) After the dehydration reaction is completed, add 2025g of potassium hypobromite aqueous solution (mass concentration 20%, containing 3 mol of potassium hypobromite) and 6 mol of potassium hydroxide, raise the temperature to 60°C, and keep the temperature for 6 hours;

[0067] (4) After the reaction is completed, atmospheric distillation is performed to collect the fraction between 158 and 160° C., which is the 1,4-butanediamine with a GC purity of 99.6% and a yield of 94%.

[0068] Example 5

[0069] A method for preparing 1,4-butanediamine is as follows:

[0070] (1) Weigh 1 mol of adipic acid and add it to a reactor. Evacuate the reactor and introduce nitrogen for more than 5 times to protect the adipic acid in an inert gas. Then, heat the reactor to 160° C. to melt the adipic acid. Then introduce sufficient ammonia to carry out an amination reaction. The pressure is 1.0 MPa and the amination reaction time is 3 h.

[0071] (2) After the amination reaction is completed, the temperature is raised to 220°C for dehydration reaction and kept at this temperature for 4 hours. The by-product water and unreacted ammonia enter the recovery device through the condensation system. After the heat preservation is completed, adipic acid diamide is obtained;

[0072] (3) After the dehydration reaction is completed, add 1811 g of potassium hypochlorite aqueous solution (mass concentration 15%, potassium hypochlorite 3 mol) and 8 mol of potassium hydroxide, raise the temperature to 60 ° C, and keep the temperature for 6 hours;

[0073] (4) After the reaction is completed, atmospheric distillation is performed to collect the fraction between 158 and 160° C., which is the 1,4-butanediamine with a GC purity of 99.8% and a yield of 94%.

[0074] Example 6

[0075] A method for preparing 1,4-butanediamine is as follows:

[0076] (1) Weigh 1 mol of adipic acid and add it to a reactor. Evacuate the reactor and introduce nitrogen for more than 5 times to protect the adipic acid in an inert gas. Then, heat the reactor to 180° C. to melt the adipic acid. Then introduce sufficient ammonia to carry out an amination reaction. The pressure is 0.8 MPa and the amination reaction time is 2 h.

[0077] (2) After the amination reaction is completed, the temperature is raised to 230°C for dehydration reaction and kept at this temperature for 5 hours. The by-product water and unreacted ammonia enter the recovery device through the condensation system. After the heat preservation is completed, adipic acid diamide is obtained;

[0078] (3) After the dehydration reaction is completed, add 993g of sodium hypochlorite aqueous solution (mass concentration 15%, containing 2 mol of sodium hypochlorite) and 5 mol of sodium hydroxide, raise the temperature to 90°C, and keep the temperature for 3 hours;

[0079] (4) After the reaction is completed, atmospheric distillation is performed to collect the fraction between 158 and 160° C., which is the 1,4-butanediamine with a GC purity of 99.7% and a yield of 95%.

[0080] Comparative Example 1

[0081] 1,4-butanediamine was prepared by the same method as in Example 1, except that, in this comparative example 1, the amount of sodium hypochlorite was reduced. The specific preparation process is as follows:

[0082] (1) Weigh 1 mol of adipic acid and add it to a reactor. Evacuate the reactor and introduce nitrogen for more than 5 times to protect the adipic acid in an inert gas. Then, heat the reactor to 170° C. to melt the adipic acid. Then introduce sufficient ammonia to carry out an amination reaction. The pressure is 1.0 MPa and the amination reaction time is 2 h.

[0083] (2) After the amination reaction is completed, the temperature is raised to 230°C for dehydration reaction and kept at this temperature for 6 hours. The by-product water and unreacted ammonia enter the recovery device through the condensation system. After the heat preservation is completed, adipic acid diamide is obtained;

[0084] (3) After the dehydration reaction is completed, add 496 g of sodium hypochlorite aqueous solution (mass concentration 15%, containing 1 mol of sodium hypochlorite) and 4 mol of sodium hydroxide, raise the temperature to 80°C, and keep the temperature for 4 hours;

[0085] (4) After the reaction is completed, atmospheric distillation is performed to collect the fraction between 158 and 160° C., which is the 1,4-butanediamine with a GC purity of 99.6% and a yield of 62%.

[0086] Comparative Example 2

[0087] 1,4-butanediamine was prepared by the same method as in Example 1, except that, in Comparative Example 2, the amount of sodium hydroxide was reduced. The specific preparation process is as follows:

[0088] (1) Weigh 1 mol of adipic acid and add it to a reactor. Evacuate the reactor and introduce nitrogen for more than 5 times to protect the adipic acid in an inert gas. Then, heat the reactor to 170° C. to melt the adipic acid. Then introduce sufficient ammonia to carry out an amination reaction. The pressure is 1.0 MPa and the amination reaction time is 2 h.

[0089] (2) After the amination reaction is completed, the temperature is raised to 230°C for dehydration reaction and kept at this temperature for 6 hours. The by-product water and unreacted ammonia enter the recovery device through the condensation system. After the heat preservation is completed, adipic acid diamide is obtained;

[0090] (3) After the dehydration reaction is completed, add 993 g of sodium hypochlorite aqueous solution (mass concentration 15%, containing 2 mol of sodium hypochlorite) and 2 mol of sodium hydroxide, raise the temperature to 80°C, and keep the temperature for 4 hours;

[0091] (4) After the reaction is completed, atmospheric distillation is performed to collect the fraction between 158 and 160° C., which is the 1,4-butanediamine with a GC purity of 99.7% and a yield of 74%.

[0092] Comparative Example 3

[0093] 1,4-butanediamine was prepared by the same method as in Example 1, except that, in Comparative Example 3, the concentration of the sodium hypochlorite aqueous solution was reduced. The specific preparation process was as follows:

[0094] (1) Weigh 1 mol of adipic acid and add it to a reactor. Evacuate the reactor and introduce nitrogen for more than 5 times to protect the adipic acid in an inert gas. Then, heat the reactor to 170° C. to melt the adipic acid. Then introduce sufficient ammonia to carry out an amination reaction. The pressure is 1.0 MPa and the amination reaction time is 2 h.

[0095] (2) After the amination reaction is completed, the temperature is raised to 230°C for dehydration reaction and kept at this temperature for 6 hours. The by-product water and unreacted ammonia enter the recovery device through the condensation system. After the heat preservation is completed, adipic acid diamide is obtained;

[0096] (3) After the dehydration reaction is completed, add 2979g of sodium hypochlorite aqueous solution (mass concentration 5%, containing 2 mol of sodium hypochlorite) and 4 mol of sodium hydroxide, raise the temperature to 80°C, and keep the temperature for 4 hours;

[0097] (4) After the reaction is completed, atmospheric distillation is performed to collect the fraction between 158 and 160° C., which is the 1,4-butanediamine with a GC purity of 99.6% and a yield of 76%.

[0098] Comparative Example 4

[0099] 1,4-butanediamine was prepared by the same method as in Example 1, except that, in this comparative example 4, the reaction temperature of step S1 was increased. The specific preparation process is as follows:

[0100] (1) Weigh 1 mol of adipic acid and add it to a reactor. Evacuate the reactor and introduce nitrogen for more than 5 times to protect the adipic acid in an inert gas. Then, heat the reactor to 200° C. to melt the adipic acid. Then introduce sufficient ammonia to carry out an amination reaction. The pressure is 1.0 MPa and the amination reaction time is 2 h.

[0101] (2) After the amination reaction is completed, the temperature is raised to 230°C for dehydration reaction and kept at this temperature for 6 hours. The by-product water and unreacted ammonia enter the recovery device through the condensation system. After the heat preservation is completed, adipic acid diamide is obtained;

[0102] (3) After the dehydration reaction is completed, add 993 g of sodium hypochlorite aqueous solution (mass concentration 15%, containing 2 mol of sodium hypochlorite) and 4 mol of sodium hydroxide, raise the temperature to 80°C, and keep the temperature for 4 hours;

[0103] (4) After the reaction is completed, atmospheric distillation is performed to collect the fraction between 158 and 160° C., which is the 1,4-butanediamine with a GC purity of 99.7% and a yield of 82%.

[0104] Comparative Example 5

[0105] 1,4-butanediamine was prepared by the same method as in Example 1, except that, in this comparative example 5, the reaction temperature of step S2 was increased. The specific preparation process is as follows:

[0106] (1) Weigh 1 mol of adipic acid and add it to a reactor. Evacuate the reactor and introduce nitrogen for more than 5 times to protect the adipic acid in an inert gas. Then, heat the reactor to 170° C. to melt the adipic acid. Then introduce sufficient ammonia to carry out an amination reaction. The pressure is 1.0 MPa and the amination reaction time is 2 h.

[0107] (2) After the amination reaction is completed, the temperature is raised to 240°C for dehydration reaction and kept at this temperature for 6 hours. The by-product water and unreacted ammonia enter the recovery device through the condensation system. After the heat preservation is completed, adipic acid diamide is obtained;

[0108] (3) After the dehydration reaction is completed, add 993 g of sodium hypochlorite aqueous solution (mass concentration 15%, containing 2 mol of sodium hypochlorite) and 4 mol of sodium hydroxide, raise the temperature to 80°C, and keep the temperature for 4 hours;

[0109] (4) After the reaction is completed, atmospheric distillation is performed to collect the fraction between 158 and 160° C., which is the 1,4-butanediamine with a GC purity of 99.7% and a yield of 80%.

[0110] Comparative Example 6

[0111] 1,4-butanediamine was prepared by the same method as in Example 1, except that, in this comparative example 6, the reaction temperature of step S2 was lowered. The specific preparation process is as follows:

[0112] (1) Weigh 1 mol of adipic acid and add it to a reactor. Evacuate the reactor and introduce nitrogen for more than 5 times to protect the adipic acid in an inert gas. Then, heat the reactor to 170° C. to melt the adipic acid. Then introduce sufficient ammonia to carry out an amination reaction. The pressure is 1.0 MPa and the amination reaction time is 2 h.

[0113] (2) After the amination reaction is completed, the temperature is raised to 200°C for dehydration reaction and kept at this temperature for 6 hours. The by-product water and unreacted ammonia enter the recovery device through the condensation system. After the heat preservation is completed, adipic acid diamide is obtained;

[0114] (3) After the dehydration reaction is completed, add 993 g of sodium hypochlorite aqueous solution (mass concentration 15%, containing 2 mol of sodium hypochlorite) and 4 mol of sodium hydroxide, raise the temperature to 80°C, and keep the temperature for 4 hours;

[0115] (4) After the reaction is completed, atmospheric distillation is performed to collect the fraction between 158 and 160° C., which is the 1,4-butanediamine with a GC purity of 99.7% and a yield of 75%.

[0116] From the above examples 1 to 6, it can be seen that the method of the present invention has good selectivity for preparing 1,4-butanediamine, the purity of the target product is above 99.5%, and the yield is above 90%. The preparation method of the present invention uses cheap adipic acid as the initial raw material and does not use expensive catalysts, thereby solving the problem of high production cost of 1,4-butanediamine. The preparation method of the present invention has mild reaction conditions, simple operation, easy control, low risk factor, and is convenient for industrial production.

[0117] From the comparison of the results of Comparative Example 1 and Example 1, it can be seen that: when the amount of sodium hypochlorite is reduced, the product yield of 1,4-butanediamine is significantly reduced (because the post-treatment purification adopts atmospheric distillation, which does not affect the selectivity of the product 1,4-butanediamine, the product purity can still be maintained at a high state, but the product yield is significantly reduced), because the reduction in the amount of sodium hypochlorite will lead to insufficient raw materials in step S3, incomplete reaction, and ultimately lead to a decrease in the yield of the target product.

[0118] From the comparison of the results of Comparative Example 2 and Example 1, it can be seen that when the amount of sodium hydroxide is reduced, the product yield of 1,4-butanediamine is significantly reduced, because reducing the amount of alkali will lead to insufficient raw materials in step S3 and incomplete reaction, which ultimately leads to a decrease in the yield of the target product.

[0119] From the comparison of the results of Comparative Example 3 and Example 1, it can be seen that if the concentration of the sodium hypochlorite aqueous solution is reduced, the product yield of 1,4-butanediamine will also decrease significantly, because reducing the concentration of the sodium hypochlorite aqueous solution will lead to a low concentration of hypochlorite ions in the step S3 reaction system, incomplete reaction, and ultimately a decrease in the yield of the target product.

[0120] From the comparison of the results of Comparative Example 4 and Example 1, it can be seen that if the reaction temperature of step S1 is increased, the product yield of 1,4-butanediamine will also decrease significantly, because increasing the reaction temperature of step S1 will cause the reaction product to be deaminated again, which is not conducive to the progress of the amination reaction, and ultimately leads to a decrease in the yield of the target product. Therefore, the reaction temperature defined in the present invention is more conducive to obtaining a high-yield 1,4-butanediamine product.

[0121] From the comparison of the results of Comparative Example 5 and Example 1, it can be seen that if the reaction temperature of step S2 is increased, the product yield of 1,4-butanediamine will also decrease significantly, because increasing the reaction temperature of step S2 will lead to excessive dehydration reaction and generate the by-product adiponitrile, which will ultimately lead to a decrease in the yield of the target product.

[0122] From the comparison of the results of Comparative Example 6 and Example 1, it can be seen that if the reaction temperature of step S2 is lowered, the product yield of 1,4-butanediamine will also decrease significantly, because lowering the reaction temperature of step S2 will lead to incomplete dehydration reaction, which will ultimately lead to a decrease in the yield of the target product. Therefore, the reaction temperature defined in the present invention is more conducive to obtaining a high-yield 1,4-butanediamine product.

[0123] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0124] For those skilled in the art, several modifications and improvements may be made without departing from the concept of the present invention, all of which belong to the protection scope of the present invention. The protection scope of the present invention shall be based on the attached claims.

Claims

1. A method for preparing 1,4-butanediamine, characterized in that: The preparation method is: S1. In an inert gas environment, heat to 160-180° C. to melt adipic acid, introduce ammonia gas at 160-180° C. and maintain pressure for reaction, wherein the amination reaction time is 1-3 hours, and the molten adipic acid reacts with sufficient ammonia gas for amination reaction; the ammonia gas introduction pressure is 0.8-1.2 MPa; S2. After the amination reaction is completed, the temperature is raised to carry out a dehydration reaction to obtain adipic acid diamide; the dehydration reaction temperature is 210-230° C., and the dehydration reaction time is 4-8 hours; S3, after the dehydration reaction is completed, add a hypohalite aqueous solution and a base, heat to react, and after the reaction is completed, perform post-treatment and purification to obtain a 1,4-butanediamine product; The mass concentration of the hypohalite aqueous solution is ≥10%, the amount of the hypohalite used is 2 to 4 times the molar amount of adipic acid, and the amount of the alkali used is 4 to 8 times the molar amount of adipic acid.

2. The method for preparing 1,4-butanediamine according to claim 1, characterized in that: In step S3, the heating temperature is 60-100° C. and the reaction time is 2-6 h.

3. The method for preparing 1,4-butanediamine according to claim 1, characterized in that: In step S3, the hypohalite is at least one of sodium hypochlorite, sodium hypobromite, potassium hypochlorite and potassium hypobromite.

4. The method for preparing 1,4-butanediamine according to claim 1, characterized in that: The alkali is at least one of sodium hydroxide and potassium hydroxide.

5. The method for preparing 1,4-butanediamine according to claim 1, characterized in that: In step S3, after the reaction is completed, atmospheric distillation is performed to collect the fraction between 158° C. and 160° C., which is the 1,4-butanediamine.