A process for the preparation of a butanediamine

Abstract

The application discloses a preparation method of butanediamine, which comprises the following steps: synthesizing cyanopropyl aldehyde by adopting synthesis gas and acrylonitrile, and then performing ammoniation hydrogenation on the cyanopropyl aldehyde to produce 1,3-butanediamine and 1,4-butanediamine in a combined manner. According to the synthesis route, the total yield of the product butanediamine is greater than or equal to 95%, and compared with the hydrocyanic acid method, the ammoniation hydrogenation catalyst has the advantages of low single consumption and low total production cost of the product.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic synthesis, and particularly relates to a preparation method of butanediamine. BACKGROUND

[0002] Common butanediamines include 1,3-butanediamine and 1,4-butanediamine, wherein 1,4-butanediamine is mainly used for nylon, dye and drug manufacturing. In particular, nylon 46 prepared from 1,4-butanediamine has a melting point as high as 300 DEG C, which is 40-80 DEG C higher than that of nylon 66 and nylon 6, and has excellent high-temperature resistance and is widely used in high-temperature resistant materials. 1,3-Butanediamine is mainly used for epoxy curing agent and chain extender, and has high reactivity and is often used in combination with N,N-dimethylcyclohexylamine, pentamethyldiethylenetriamine and the like.

[0003] Existing preparation methods of 1,4-butanediamine mainly include chemical synthesis method and biological synthesis method, wherein the chemical synthesis method includes 1,4-butanedinitrile method, 1,4-butanediol method and 1,4-butandioic acid method. The most common chemical synthesis method of butanediamine is butanedinitrile catalytic hydrogenation method, that is, propylene nitrile (ACN) is added with hydrogen cyanide (HCN) to synthesize butanedinitrile, and then butanedinitrile is hydrogenated under the action of a catalyst to obtain 1,4-butanediamine. The biggest problem of this method is that HCN, which is highly toxic, is used, and the process has a large risk coefficient. In addition, the main difficulty lies in controlling the residual HCN in the addition reaction crude product. The residual HCN will poison the hydrogenation catalyst, causing the reaction efficiency to decrease and the catalyst consumption to increase. Therefore, the addition reaction crude product needs to be washed with alkali and purified to control the purity of butanedinitrile, and the process is also relatively complex. CN112341339A discloses a method for preparing 1,4-butanediamine by using 1,4-butanediol as raw material, first dehydrogenating and cyclizing to obtain gamma-butyrolactone, further ammoniating to obtain gamma-butyrolactam, then ring-opening by ammonolysis to obtain 4-aminobutyronitrile, and finally hydrogenating to obtain 1,4-butanediamine. CN114539070A discloses a method for preparing 1,4-butanediamine from 1,4-butandioic acid. First, butandioic acid is esterified with methanol to obtain butandioic acid methyl ester, then hydrogenation is carried out to obtain 1,4-butanediol, and finally, a hydrogenation reaction is carried out to obtain 1,4-butanediamine. The above process flow is complex, the raw material cost is high, the product yield is low, and the economic efficiency is poor.

[0004] Another method is biosynthesis method, including ornithine method, arginine method, glucose method, etc. CN101010433A discloses a method for producing 1,4-butanediamine by improving the activity of ornithine decarboxylase in microorganisms using ornithine as raw material. CN112921022A discloses a method for producing 1,4-butanediamine by fermentation of Escherichia coli after genetic reconstruction using arginine as raw material. CN113061562A discloses a method for producing 1,4-butanediamine by fermentation of recombinant Corynebacterium crenatum using glucose as raw material. The above-mentioned methods are still complex, have many by-products, and the product is difficult to separate. In addition, the production cost is high due to the poor tolerance of the engineering enzyme and the low production efficiency.

[0005] In summary, there is a need to develop a new process to solve the above problems. SUMMARY

[0006] In view of the problems of using toxic substances, poisoning hydrogenation catalysts, and low yield of 1,3-butanediamine in the existing synthesis route, the present application provides a synthesis method of butanediamine.

[0007] The present application discloses a method for producing butanediamine by using acrylonitrile as raw material and adopting hydroformylation and hydrogenation ammination technology, which can avoid using toxic substances, reduce the consumption of hydrogenation catalysts, and efficiently co-produce 1,3-butanediamine and 1,4-butanediamine with a comprehensive yield of ≥95%.

[0008] The technical scheme adopted is as follows:

[0009] A preparation method of butanediamine, comprising the following steps:

[0010] (1) synthesizing cyano propanal by using acrylonitrile and synthesis gas as raw materials under the action of catalyst 1;

[0011] (2) co-producing 1,3-butanediamine and 1,4-butanediamine by catalytic ammoniation hydrogenation in the presence of catalyst 2, additive 1, additive 2, and solvent by using cyano propanal, liquid ammonia, and hydrogen as raw materials.

[0012] In one specific embodiment, the catalyst 1 of step (1) is a Rh-based catalyst, which can be one or more of Rh(acac)3, RhCl(PPh3)3, Rh(acac)(CO)2, and HRh(CO)(PPh3)3, preferably Rh(acac)(CO)2 and / or HRh(CO)(PPh3)3. The phosphine ligand is tripyrrolidinophosphine, and the molar ratio of the ligand to Rh can be 5-20:1, preferably 10-15:1.

[0013] In a specific embodiment, the Rh catalyst is used in an amount of 10-200 ppm of acrylonitrile, preferably in an amount of 50-80 ppm.

[0014] In a specific embodiment, the H2 / CO molar ratio in the synthesis gas is 1-10:1, preferably 3-6:1.

[0015] In a specific embodiment, the reaction temperature in step (1) is 80-150°C, preferably 100-120°C, and the reaction pressure is 2-5 MPa, preferably 3-4 MPa. The reaction is a batch reaction, and the reaction time is 1-5 h.

[0016] In a specific embodiment, the cyanopropionaldehyde in step (1) is recovered by extracting the reaction solution.

[0017] In a specific embodiment, the catalyst 2 for the amination hydrogenation reaction in step (2) is a supported Ni catalyst, which can be prepared by an impregnation method. The supported Ni catalyst comprises active metal Ni, a modified metal, and a metal oxide carrier. The modified metal can be one or more of Pd, Pt, Co, and Ag, preferably Pd and / or Pt. The metal oxide carrier can be one or more of alumina, zirconia, magnesia, and niobia, preferably zirconia.

[0018] Preferably, in the supported Ni catalyst, the content of Ni is 10-30 wt%, preferably 15-20 wt%; the content of the modified metal is 1-5 wt%, preferably 2-3 wt%; and the rest is the metal oxide carrier.

[0019] In a specific embodiment, the adjuvant 1 is one or more of zinc phosphide, copper phosphide, and aluminum phosphide, preferably zinc phosphide.

[0020] In a specific embodiment, the adjuvant 2 can be an inorganic adjuvant such as LiOH, NaOH, and KOH, or an organic adjuvant such as TMAH, preferably adjuvant 2 is LiOH and / or NaOH.

[0021] In a specific embodiment, the solvent in step (2) can be aprotic solvents such as DMF, THF, dioxane, and toluene, preferably the solvent is DMF and / or THF.

[0022] In a specific embodiment, the amount of catalyst 2 used in step (2) is 5-30 wt% of the cyanopropionaldehyde, preferably 10-20 wt%.

[0023] In a specific embodiment, the amount of the auxiliary agent 1 used in step (2) is 10-40 wt% of the catalyst 2, preferably 20-30 wt%.

[0024] In a specific embodiment, the amount of the auxiliary agent 2 used in step (2) is 1-10 wt% of the catalyst 2, preferably 1-5 wt%.

[0025] In a specific embodiment, the amount of the solvent used in step (2) is 100-300 wt% of cyanopropyl aldehyde, preferably 100-200 wt%.

[0026] In a specific embodiment, the amination hydrogenation reaction in step (2) is carried out in a semi-batch mode, with the solvent and liquid ammonia as the bottom layer, the molar ratio of liquid ammonia to cyanopropyl aldehyde being 1-10:1, preferably 2-5:1, and the space velocity of cyanopropyl aldehyde being 1-3 g / g cat. / h.

[0027] In a specific embodiment, the reaction temperature in step (2) is 80-130°C, preferably 90-120°C; and the pressure is 1-10 MPa, preferably 5-8 MPa.

[0028] In a specific embodiment, the total yield of the butanediamines, 1,3-butanediamine and 1,4-butanediamine synthesized by the above steps is ≥95%.

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] 1) The present application uses hydroformylation reaction in step (1), which avoids the use of the highly toxic raw material hydrocyanic acid, is conducive to improving the service life of the hydrogenation catalyst in step (2), and further reduces the cost; on the other hand, the intermediate synthesized in step (1) can simultaneously coproduce 1,3-butanediamine and 1,4-butanediamine, and the product selectivity is relatively flexible.

[0031] 2) In the amination hydrogenation reaction in step (2) of the present application, the mother liquor of step (1) is directly used as the raw material, which avoids the neutralization and purification steps in the traditional hydrocyanic acid method, and further improves the economy.

[0032] 3) The catalyst of the present application can effectively improve the selectivity of the target product butanediamine due to the synergy and directional catalysis between metals. In addition, since the aldehyde group amination hydrogenation reaction is faster than the cyano hydrogenation, the intermediate aminobutyronitrile is easily formed, and the aminobutyronile is prone to intramolecular addition to generate part of the azacycle byproduct. The addition of the additive 1 phosphide has strong electron-withdrawing properties, which can quench the electrons of the intermediate amino group, reducing the generation of part of the pyrrolidine byproduct. The addition of the additive 2 can reduce the deamination reaction between butanediamine to generate the byproduct secondary amine N-aminobutyl butanediamine. Therefore, under the conditions of the catalyst and the additive of the present application, the yield of butanediamine can be effectively improved, and the total yield is ≥ 95%. DETAILED DESCRIPTION

[0033] In order to better understand the technical solutions of the present application, the following examples will further illustrate the method provided by the present application, but the present application is not limited to the listed examples, and any other known changes within the scope of the claims of the present application should also be included.

[0034] The present application will be further explained and described by more specific examples below, but do not constitute any limitation.

[0035] The main raw materials used in the following examples or comparative examples are as follows, and other ordinary commercially available raw materials are used unless otherwise specified:

[0036] Rh(acac)3, RhCl(PPh3)3, Rh(acac)(CO)2, HRh(CO)(PPh3)3, tripyrrolidine phosphine, purchased from Beijing Inokai Technology Co., Ltd.

[0037] The reaction liquid composition in the following examples was analyzed by gas chromatography under the following conditions: Agilent DB-5 chromatographic column, injection port temperature 280°C, FID detector temperature 300°C, column flow rate 1.5 ml / min, hydrogen flow rate 30 ml / min, air flow rate 400 ml / min, and the program temperature was raised to 80°C at 5°C / min, then to 280°C at 15°C / min, and maintained for 10 min.

[0038] Example 1

[0039] Step 1 : Rh(acac)(CO)2(0.097 mmol), tripyrrolidinophosphine ligand 0.972 mmol, 200 g acrylonitrile were charged into a reactor, the reactor was replaced with synthesis gas (H2 / CO=6) for three times, then the reactor was stirred at 1000 rpm, heated to 100 °C, and then synthesis gas was introduced to a total pressure of 3.0 MPa. The reaction was carried out for 2 h under the above conditions, and the pressure was kept constant during the reaction. After the reaction was completed, the reaction mother liquor was cooled, the catalyst was extracted with water, and the sample was analyzed by GC. The conversion of acrylonitrile was 99.7%, the yield of n-cyanopropanal was 63.6%, and the yield of iso-cyanopropanal was 35.1%.

[0040] Step 2: 1# catalyst was prepared by impregnation method, wherein the content of Ni was 20 wt%, the content of Pd was 1 wt%, and the rest was alumina carrier. 20 g of 1# catalyst, 4 g of zinc phosphide, 0.4 g of NaOH, and 200 g of THF were added to the reactor, the reactor was replaced with nitrogen for three times, then 204.8 g of liquid ammonia was added to the reactor, heated to 100 °C, and then 200 g of step 1 mother liquor was added to the reactor at a space velocity of 2 g / g cat / h by a laminar pump, while hydrogen was introduced, the total pressure of the system was kept at 3 MPa, and the reaction was carried out at a temperature of 100 °C. After the feeding was completed, it was extended for 1 h, then cooled, depressurized and deammoniated, and the sample was analyzed. The conversion of cyanopropanal was 99.9%, the yield of 1,3-butanediamine was 34.7%, the yield of 1,4-butanediamine was 63.2%, the total yield of butanediamine was 97.9%, the content of pyrrolidine was 0.1 wt%, and the content of N-aminobutylbutanediamine was 0.1 wt%.

[0041] Example 2

[0042] Step 1 : RhCl(PPh3)3(0.389 mmol), tripyrrolidinophosphine ligand 1.944 mmol, 200 g acrylonitrile were charged into a reactor, the reactor was replaced with synthesis gas (H2 / CO=3) for three times, then the reactor was stirred at 1000 rpm, heated to 150 °C, and then synthesis gas was introduced to a total pressure of 2.0 MPa. The reaction was carried out for 1 h under the above conditions, and the pressure was kept constant during the reaction. After the reaction was completed, the reaction mother liquor was cooled, the catalyst was extracted with water, and the sample was analyzed by GC. The conversion of acrylonitrile was 99.9%, the yield of n-cyanopropanal was 57.8%, and the yield of iso-cyanopropanal was 39.3%.

[0043] Step 2: 2# catalyst was prepared by impregnation method, in which the content of Ni was 10wt%, the content of Pt was 5wt%, and the rest was zirconia carrier. 60g 2# catalyst, 6g copper phosphide, 3g KOH, 400g dioxane were added into the reaction kettle, the reaction kettle was replaced with nitrogen for three times, then 409.6g liquid ammonia was added into the kettle, the temperature was increased to 80℃, 200g step 1 mother liquor was added into the kettle at a speed of 3g / g cat / h by means of a laminar flow pump, hydrogen was passed through, the total pressure of the system was maintained at 10MPa, the temperature was 80℃, and the reaction was carried out, after the feeding was completed, it was prolonged for 1h, then the temperature was decreased, the pressure was released, and the ammonia was discharged, sampling analysis was conducted, the conversion rate of cyanoacetaldehyde was 100%, the yield of 1,3-diaminobutane was 38.9%, the yield of 1,4-diaminobutane was 57.3%, the total yield of butanediamine was 96.2%, the content of pyrrolidine was 0.2wt%, and the content of N-aminobutylbutanediamine was 0.2wt%.

[0044] Example 3

[0045] Step 1: HRh(CO)(PPh3)3(0.019mmol), tripyrrolidine phosphine ligand 0.388mmol, 200g acrylonitrile were added into the reaction kettle, the reaction kettle was replaced with synthetic gas (H2 / CO=1) for three times, stirring was carried out at a speed of 1000rpm, heating was carried out to increase the temperature to 120℃, synthetic gas was passed in until the total pressure was 5.0MPa, the reaction was carried out under the condition for 5h, and the pressure was maintained constant during the reaction. After the reaction was completed, the reaction mother liquor was cooled, the catalyst was extracted with water, and sampling was conducted for GC analysis, the conversion rate of acrylonitrile was 99.8%, the yield of n-cyanoacetaldehyde was 62.7%, and the yield of iso-cyanoacetaldehyde was 35.3%.

[0046] Step 2: 3# catalyst was prepared by impregnation method, in which the content of Ni was 15wt%, the content of Ag was 3wt%, and the rest was niobia carrier. 40g 3# catalyst, 16g aluminum phosphide, 0.4g TMAH, 600g DMF were added into the reaction kettle, the reaction kettle was replaced with nitrogen for three times, then 81.9g liquid ammonia was added into the kettle, the temperature was increased to 90℃, 200g step 1 mother liquor was added into the kettle at a speed of 2.5g / g cat / h by means of a laminar flow pump, hydrogen was passed through, the total pressure of the system was maintained at 8MPa, the temperature was 90℃, and the reaction was carried out, after the feeding was completed, it was prolonged for 1h, then the temperature was decreased, the pressure was released, and the ammonia was discharged, sampling analysis was conducted, the conversion rate of cyanoacetaldehyde was 99.8%, the yield of 1,3-diaminobutane was 34.4%, the yield of 1,4-diaminobutane was 62.1%, the total yield of butanediamine was 96.5%, the content of pyrrolidine was 0.2wt%, and the content of N-aminobutylbutanediamine was 0.3wt%.

[0047] Example 4

[0048] Step 1: Rh(acac)3(0.155 mmol), tri-pyrrolidine phosphine ligand 2.332 mmol, 200 g of acrylonitrile were charged into a reactor, the reactor was purged with synthesis gas (H2 / CO = 10) for three times, then the reactor was stirred at 1000 rpm, and heated to 80 °C, synthesis gas was introduced to reach a total pressure of 4.0 MPa, and the reaction was carried out for 3 h under the above conditions, and the pressure was kept constant during the reaction. After the reaction was completed, the reaction mother liquor was cooled, the catalyst was extracted with water, and the sample was analyzed by GC. The conversion of acrylonitrile was 100%, the yield of n-cyanopropanal was 54.3%, and the yield of iso-cyanopropanal was 42.4%.

[0049] Step 2: 4# catalyst was prepared by impregnation method, wherein the content of Ni was 30 wt%, the content of Co was 2 wt%, and the rest was magnesia carrier. 10 g of 4# catalyst, 3 g of copper phosphide, 1 g of LiOH, and 400 g of toluene were added to the reactor, the reactor was purged with nitrogen for three times, then 41.0 g of liquid ammonia was added to the reactor, the temperature was raised to 130 °C, 200 g of step 1 mother liquor was added to the reactor at a space velocity of 1 g / g cat / h by means of a laminar pump, and hydrogen was introduced, the total pressure of the system was kept at 5 MPa, the temperature was kept at 130 °C, and the reaction was carried out. After the feeding was completed, it was prolonged for 1 h, then the temperature was lowered, the pressure was released, and the ammonia was released, and the sample was analyzed. The conversion of cyanopropanal was 99.4%, the yield of 1,3-butanediamine was 41.8%, the yield of 1,4-butanediamine was 53.5%, the total yield of butanediamine was 95.3%, the content of pyrrolidine was 0.2 wt%, and the content of N-aminobutylbutanediamine was 0.1 wt%.

[0050] Example 5

[0051] Step 1: Rh(acac)(CO)2(0.126 mmol), tri-pyrrolidine phosphine ligand 1.263 mmol, 200 g of acrylonitrile were charged into a reactor, the reactor was purged with synthesis gas (H2 / CO = 4) for three times, then the reactor was stirred at 1000 rpm, and heated to 110 °C, synthesis gas was introduced to reach a total pressure of 3.0 MPa, and the reaction was carried out for 2 h under the above conditions, and the pressure was kept constant during the reaction. After the reaction was completed, the reaction mother liquor was cooled, the catalyst was extracted with water, and the sample was analyzed by GC. The conversion of acrylonitrile was 100%, the yield of n-cyanopropanal was 67.4%, and the yield of iso-cyanopropanal was 31.7%.

[0052] Step 2: 5# catalyst was prepared by impregnation method, in which the content of Ni was 20wt%, the content of Pd was 2.5wt%, and the rest was zirconia carrier. 30g 5# catalyst, 7.5g zinc phosphide, 0.9g NaOH, 300g THF were added into the reaction kettle, after the reaction kettle was replaced three times with nitrogen, 122.9g liquid ammonia was added into the kettle, the temperature was raised to 110°C, 200g step 1 mother liquor was added into the kettle at a space velocity of 2g / g cat / h by means of a laminar flow pump, while hydrogen was passed through, the total pressure of the system was maintained at 7MPa, the temperature was maintained at 110°C, and the reaction was carried out, after the feeding was completed, 1h was prolonged, then the temperature was lowered, the pressure was released, and ammonia was discharged, sampling analysis was carried out, the conversion rate of cyanopropyl aldehyde was 100%, the yield of 1,3-butanediamine was 31.5%, the yield of 1,4-butanediamine was 67.1%, the total yield of butanediamine was 98.6%, the content of pyrrolidine was 0.1wt%, and the content of N-aminobutylbutanediamine was 0.1wt%.

[0053] Comparative Example 1 (compared with Example 5, without adding the additive zinc phosphide)

[0054] Step 2: 5# catalyst was prepared by impregnation method, in which the content of Ni was 20wt%, the content of Pd was 2.5wt%, and the rest was zirconia carrier. 30g 5# catalyst, 0.9g NaOH, 300g THF were added into the reaction kettle, after the reaction kettle was replaced three times with nitrogen, 122.9g liquid ammonia was added into the kettle, the temperature was raised to 110°C, 200g step 1 mother liquor was added into the kettle at a space velocity of 2g / g cat / h by means of a laminar flow pump, while hydrogen was passed through, the total pressure of the system was maintained at 7MPa, the temperature was maintained at 110°C, and the reaction was carried out, after the feeding was completed, 1h was prolonged, then the temperature was lowered, the pressure was released, and ammonia was discharged, sampling analysis was carried out, the conversion rate of cyanopropyl aldehyde was 100%, the yield of 1,3-butanediamine was 29.7%, the yield of 1,4-butanediamine was 63.8%, the total yield of butanediamine was 93.5%, the content of pyrrolidine was 2.3wt%, and the content of N-aminobutylbutanediamine was 0.8wt%.

[0055] Comparative Example 2 (compared with Example 5, without adding the additive NaOH)

[0056] Step 2: 5# catalyst was prepared by impregnation method, in which the content of Ni was 20wt%, the content of Pd was 2.5wt%, and the rest was zirconia carrier. 30g 5# catalyst, 7.5g zinc phosphide, 300g THF were added into the reaction kettle, the reaction kettle was replaced with nitrogen three times, then 122.9g liquid ammonia was added into the kettle, the temperature was raised to 110°C, 200g mother liquor of step 1 in example 5 was added into the kettle at a speed of 2g / g cat / h by means of a laminar pump, hydrogen was passed through, the total pressure of the system was maintained at 7MPa, the temperature was maintained at 110°C, the reaction was carried out, after the feeding was completed, it was prolonged for 1h, then the temperature and pressure were reduced, ammonia was released, sampling analysis was conducted, the conversion rate of cyano propanal was 100%, the yield of 1,3-butanediamine was 30.2%, the yield of 1,4-butanediamine was 64.4%, the total yield of butanediamine was 94.6%, the content of pyrrolidine was 0.1wt%, and the content of N-aminobutyl butanediamine was 3.4wt%.

Claims

1. A method for preparing butylenediamine, comprising the following steps: (1) synthesizing cyano propanal from acrylonitrile and synthesis gas under the action of catalyst 1; (2) catalytically ammoniating and hydrogenating to co-produce 2-methyl-1,3- propanediamine and 1,4-butylenediamine from cyano propanal, liquid ammonia and hydrogen in the presence of catalyst 2, additive 1, additive 2 and a solvent; The catalyst 1 of step (1) comprises a Rh compound and a ligand tripyrrolidinophosphine; In step (2), the catalyst 2 is a supported Ni catalyst, which comprises active metal Ni, modified metal, metal oxide carrier; The additive 1 is one or more of zinc phosphide, copper phosphide and aluminum phosphide; The additive 2 is one or more of LiOH, NaOH, KOH and TMAH; The H2 / CO molar ratio in the synthesis gas is 1-10.

2. The method of claim 1, wherein, The Rh compound is one or more of Rh(acac)3, RhCl(PPh3)3, Rh(acac)(CO)2 and HRh(CO)(PPh3)3; the molar ratio of the ligand to Rh is 5-20:

1.

3. The method of claim 2, wherein, The molar ratio of the ligand to Rh is 10-15:

1.

4. The method of claim 1, wherein, The modified metal is one or more of Pd, Pt, Co and Ag; the metal oxide carrier is one or more of alumina, zirconia, magnesia and niobia.

5. The method of claim 1, wherein, In the catalyst 2, the content of Ni is 10-30 wt%; the content of modified metal is 1-5 wt%; and the rest is the metal oxide carrier.

6. The method of claim 1, wherein, In the catalyst 2, the content of Ni is 15-20 wt%; the content of modified metal is 2-3 wt%; and the rest is the metal oxide carrier.

7. The method of claim 1, wherein, The amount of the additive 1 is 10-40 wt% of the catalyst 2.

8. The method of claim 1, wherein, The amount of the additive 1 is 20-30 wt% of the catalyst 2.

9. The method of claim 1, wherein, The amount of the additive 2 is 1-10 wt% of the catalyst 2.

10. The method of claim 1, wherein, The amount of the additive 2 is 1-5 wt% of the catalyst 2.

11. The method of claim 1, wherein, The ammoniation and hydrogenation reaction of step (2) is carried out in a semi-batch mode, with the solvent and liquid ammonia being laid at the bottom, the molar ratio of liquid ammonia to cyano propanal being 1-10:1, and the cyano propanal feed space velocity being 1-3 g / g cat. / h.

12. The method of claim 11, wherein, The molar ratio of liquid ammonia to cyano propanal is 2-5:

1.

13. The method of claim 1, wherein, The reaction temperature of step (2) is 80-130℃; and the pressure is 1-10 MPa.