Device and process method for continuously preparing N-alkyl-1, 3-propane diamine

Abstract

The invention belongs to the technical field of fine chemical engineering, and particularly relates to a device and a process method for continuously preparing N-alkyl-1, 3-propane diamine. The device comprises a plate type microreactor, a delay reactor, a separator, a heat exchanger, a static mixer, a gas-liquid micromixer, a fixed bed reactor, a gas-liquid separator, a buffer tank and a gas mass flow controller. The method comprises the following steps: reacting an aliphatic amine solution with acrylonitrile sequentially through a plate type microreactor and a delay reactor to obtain a mixed reaction solution containing 3-alkylamino propionitrile, separating the mixed reaction solution through a separator to obtain 3-ethylamino propionitrile, mixing the 3-ethylamino propionitrile with an alkali aid solution through a static mixer, carrying out gas-liquid mixing on the 3-ethylamino propionitrile and hydrogen through a gas-liquid micromixer, and carrying out solid-liquid separation to obtain the 3-alkylamino propionitrile. And then carrying out continuous catalytic hydrogenation in a fixed bed reactor to generate N-alkyl-1, 3-propane diamine. The purposes of high heat transfer and mass transfer rate and accurate temperature control are achieved, and the product yield is greater than 99.2%.

Description

Technical Field

[0001] The present invention belongs to the technical field of fine chemical industry, and particularly relates to an apparatus and a process for continuously preparing N-alkyl-1,3-propanediamine. Background Art

[0002] N-alkyl-1,3-propanediamine belongs to lower aliphatic diamines and is an important organic chemical intermediate, which is widely used in the fields of medicine, feed, food, etc.

[0003] N-alkyl 1,3-propanediamine includes important intermediate similar reaction formula structures such as N-ethyl-1,3-propanediamine, N-methyl-1,3-propanediamine, and N,N-dimethyl-1,3-propanediamine. They all have active chemical properties. Due to the presence of lone electron pairs on the nitrogen atom, they have good nucleophilic ability and are relatively easy to react with electrophilic reagents, and can be used for the synthesis of downstream products.

[0004] Patent CN102260175B provides a method for synthesizing N-ethyl ethylenediamine by directly reacting chloroethane with ethylenediamine. After the chlorine atom in chloroethane replaces the amino hydrogen atom in ethylenediamine, the target product is formed. By the same mechanism, N-ethyl-1,3-propanediamine can also be directly synthesized according to the method of patent CN102260175B using 1,3-propanediamine, but this method is prone to generating multi-substituted by-products and is difficult to separate.

[0005] The synthesis method of N-alkyl-1,3-propanediamine can also adopt the acrylonitrile ammoniation reduction method. This method has wide raw material sources, simple synthesis methods, and is easy to prepare. However, in the batch preparation process, the feeding rate of acrylonitrile needs to be strictly controlled during the acrylonitrile ammoniation reaction stage. If the dropping is too fast, it will cause intense heat release and is prone to generating various by-products; during the hydrogenation reaction stage, there is an explosion risk during the supplementary addition of the skeletal catalyst. Therefore, the batch method for N-alkyl-1,3-propanediamine has problems such as low production efficiency, poor safety, and poor product selectivity.

[0006] In recent years, continuous processes for the amination of acrylonitrile have also been reported in relevant patents or literature. Patent CN112961061B provides a process for the continuous preparation of N,N-dimethyl-1,3-propanediamine. This method uses two fixed beds in series. With monomethylamine and acrylonitrile as raw materials, it first continuously passes through the first fixed bed reactor to react and generate the intermediate 3-methylaminopropionitrile. This intermediate then continuously enters the second fixed bed hydrogenation reactor for catalytic hydrogenation to produce N-methyl-1,3-propanediamine, with a yield of ≥99%. The process of this invention is simple, has less three wastes, is energy-saving and environmentally friendly, and has low costs, making it easy to industrialize. However, this continuous process also has some deficiencies. For example, in the first step of the reaction between monomethylamine and acrylonitrile in this process, an A-type or X-type molecular sieve (low silica-alumina ratio zeolite molecular sieve) is used as the catalyst, and the promoter is an inorganic base aqueous solution or an alcohol solution. During long-term continuous operation, the promoter alkali solution will corrode the molecular sieve, causing the framework of the A-type or X-type molecular sieve to collapse and the particles to pulverize, which easily clogs the backend separator equipment and filtration equipment, and is not conducive to continuous operation and production. In addition, to ensure the high selectivity of 3-methylaminopropionitrile in this continuous process, an excessive amount of monomethylamine raw material needs to enter the reaction system, resulting in relatively large energy and material consumption.

[0007] Therefore, an improved technical method is needed to address the deficiencies of the above-mentioned prior art. Summary of the Invention

[0008] Aiming at the problems of low production efficiency, poor safety, and poor product selectivity in the batch production of N-alkyl-1,3-propanediamine, the problem solved by the present invention is to provide a device and process method for the safe, efficient, and easy continuous preparation of N-alkyl-1,3-propanediamine.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] A device for the continuous preparation of N-ethyl-1,3-propanediamine, the device includes a plate microreactor 3, a delay reactor 4, a separator 5, a heat exchanger 6, a static mixer 7, a gas-liquid micro mixer 8, a fixed bed reactor 9, a gas-liquid separator 10, a buffer tank 13, and a gas mass flow controller 20;

[0011] Among them, the three inlets of the plate micro-reactor 3 are respectively connected to the fatty amine solution 1, acrylonitrile 2, and nitrogen gas cylinder 14. The outlet of the plate micro-reactor 3 is connected to the inlet of the delay reactor 4. The outlet of the delay reactor 4 is connected to the inlet of the separator 5. One outlet of the separator 5 is sequentially connected to the heat exchanger 6 and the buffer tank 13. The other outlet of the separator 5 is divided into two branches. One branch is emptied, and the other branch is connected to one inlet of the static mixer 7. The other inlet of the static mixer 7 is connected to the alkali assistant 11. The outlet of the static mixer 7 is connected to one inlet of the gas-liquid micro-mixer 8. After the alkali assistant and the product of the separator 5 are mixed in the static mixer 7, they flow into the gas-liquid micro-mixer 8. The other inlet of the gas-liquid micro-mixer 8 is connected to the hydrogen gas cylinder 12. The inlet of the fixed-bed reactor 9 is connected to the inlet of the gas-liquid micro-mixer 8. The outlet of the fixed-bed reactor 9 is connected to the inlet of the gas-liquid separator 10. The two outlets of the gas-liquid separator 10 are respectively the separated gas outlet and the liquid outlet.

[0012] Metering pumps are respectively installed on the pipelines between the ethylamine solution pipeline and the plate micro-reactor 3, between the acrylonitrile pipeline and the plate micro-reactor 3, between the buffer tank 13 and the plate micro-reactor 3, between the alkali assistant 11 and the static mixer 7, and between the separator 5 and the static mixer 7.

[0013] A gas mass flow controller 20 is installed on the pipeline between the hydrogen gas cylinder 12 and the gas-liquid micro-mixer 8.

[0014] A method for continuously preparing N-ethyl-1,3-propanediamine using the above device, in which the fatty amine solution and acrylonitrile react successively through the plate micro-reactor 3 and the delay reactor 4. The conversion rate of acrylonitrile is 100%. A mixed reaction solution containing 3-alkylaminopropionitrile, solvent, and a small amount of amine is obtained by reaction. The mixed reaction solution is separated by the separator 5. After the separated 3-ethylaminopropionitrile, solvent, and the alkali assistant solution are mixed in the static mixer 7, they are then subjected to gas-liquid mixing with hydrogen through the gas-liquid micro-mixer 8, and then continuously catalytically hydrogenated in the fixed-bed reactor 9 to generate N-alkyl-1,3-propanediamine. The yield of the hydrogenation product is higher than 98%.

[0015] Meanwhile, the amine vapor separated by the separator 5 is condensed by the heat exchanger 6 and received by the buffer tank 13, and then returned to the plate micro-reactor 3 for recycling.

[0016] The fatty amine solution is an alcohol solution or an aqueous solution of the amine.

[0017] The molar ratio of the fatty amine to acrylonitrile in the plate micro-reactor 3 is 1.05 - 1.5:1, preferably 1.1 - 1.2:1.

[0018] The residence time of the reaction solution in the plate microreactor 3 is 0.5 - 3.0 s, preferably 1.0 - 2.0 s; the reaction temperature is 30 - 90 °C, preferably 40 - 60 °C; the reaction pressure is 0.2 - 2.0 Mpa, preferably 0.3 - 1.0 Mpa.

[0019] The temperature of the delay reactor 4 is 50 - 100 °C, preferably 60 - 90 °C; the reaction pressure is 0.2 - 2.0 Mpa, preferably 0.3 - 1.0 Mpa; the residence time of the reaction solution in the delay reactor is 100 - 300 s, preferably 100 - 200 s.

[0020] The cooling temperature of the heat exchanger 6 is 1 - 5 °C.

[0021] The fixed bed hydrogenation reaction conditions are as follows: the reaction temperature is 40 - 120 °C, preferably 60 - 100 °C; the reaction pressure is 1.5 - 5.0 Mpa; the control speed is 1 - 10 h -1 , preferably 2.5 - 5 h -1 ; the gas - liquid volume ratio is 80 - 400:1, preferably 120 - 200:1.

[0022] The catalyst in the fixed bed reactor 9 is a Raney - Ni catalyst, the catalyst particle size is 1 - 3 mm, and the particle morphology is irregular granular.

[0023] The alkali promoter is one of sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia water, sodium methoxide; the concentration of the alkali promoter solution is 2 - 5%; the mass ratio of the alkali promoter to 3 - alkylaminopropionitrile is 0.2 - 1%, and the solvent is selected from methanol or aqueous solution.

[0024] The beneficial effects brought by the present invention are as follows:

[0025] 1. The present invention uses a plate microreactor with a relatively high specific surface area and a fine pore structure, achieving the purpose of high heat and mass transfer rates and precise temperature control. At the same time, it adopts the form of connecting the plate microreactor in series with the fixed bed reactor to avoid the high - temperature addition product N - alkyl - 1,3 - propanediamine from contacting with air and generating deteriorated by - products. At the same time, the addition reaction heat is effectively utilized in the hydrogenation stage, saving energy consumption, enabling the continuous preparation of N - alkyl - 1,3 - propanediamine from fatty amines and acrylonitrile, greatly improving the production efficiency, and the product yield is relatively high, with the yield greater than 99.2%.

[0026] 2. In the reaction process of the present invention, the excessive amine after the ammoxidation of raw material acrylonitrile can be recycled, and the molar ratio of fatty amine to acrylonitrile is always maintained at 1.1 - 1.2:1 during the reaction process, avoiding the generation of other by-products from fatty amine during the hydrogenation reaction, improving the hydrogenation selectivity of 3-alkylpropionitrile. Secondly, the recycling of amine can effectively reduce material loss and energy consumption, and improve the economy of the reaction process.

[0027] 3. The method for continuously preparing N-alkyl-1,3-propanediamine of the present invention improves production capacity, production process safety and stability. This process method is easy to realize continuous production, and is green, environmentally friendly, suitable for industrialization, and has high economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a process flow schematic diagram of the present invention. Among them, 1 - fatty amine solution, 2 - acrylonitrile, 3 - plate microreactor, 4 - delay reactor, 5 - separator, 6 - heat exchanger, 7 - static mixer, 8 - gas-liquid micromixer, 9 - fixed bed reactor, 10 - gas-liquid separator, 11 - alkali assistant, 12 - hydrogen cylinder, 13 - buffer tank, 14 - nitrogen gas cylinder, 15, 16, 17, 18, 19 - metering pumps, 20 - gas mass flow controller. DETAILED DESCRIPTION OF THE INVENTION

[0029] The technical features of the present invention will be further described below through examples. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, but are not limited to the examples.

[0030] The equipment, reagents, etc. used in the examples of the present invention are all prior arts and will not be elaborated.

[0031] Examples 1 to 4 are specific implementation schemes for continuously preparing N-ethyl-1,3-propanediamine. The reaction formula is as follows:

[0032]

[0033] Example 1

[0034] The fixed-bed reactor 9 is filled with the catalyst Raney-Ni. The catalyst particle size is 1-3 mm, and the particle morphology is irregular granular. Open the nitrogen cylinder 14 to purge the entire reaction system and discharge the air. Fill the plate micro-reactor 3 and the delay reactor 4 with nitrogen to a pressure of 0.3 MPa. Set the temperature of the plate micro-reactor 3 to 40 °C, the temperature of the delay reactor 4 to 60 °C, the temperature of the heat exchanger 6 to 1.0 °C, and the set temperature of the fixed-bed reactor 9 to 60 °C. Open the hydrogen cylinder 12 and adjust the pressure of the fixed-bed reactor 9 to 5.0 MPa. Set the hydrogen flow rate of the gas mass flow controller 20 according to the feed rate of the hydrogenation raw material (3-ethylaminopropionitrile) to maintain the gas-liquid volume ratio at 120:1. Start the ethylamine (70% aqueous ethylamine solution) metering pump 1 and the acrylonitrile (99%) metering pump 2, and feed according to the molar ratio of ethylamine to acrylonitrile of 1.1:1. The residence times of the reaction materials in the plate micro-reactor 3 and the delay reactor 4 are 1.0 s and 100 s respectively. The area normalization purity of the product 3-ethylaminopropionitrile obtained from the acrylonitrile ammoniation reaction is above 99.7%. After the reaction liquid is separated by the separator 5, a mixture of 3-ethylaminopropionitrile and the solvent is discharged from the bottom of the separator 5 and is transported by the metering pump 19 to the static mixer 7, where it is fully mixed with a 3% mass concentration sodium hydroxide aqueous solution (alkali promoter). The mass ratio of sodium hydroxide to 3-ethylaminopropionitrile is 0.2%. Then, it is gas-liquid mixed with hydrogen through the gas-liquid micro-mixer 8, and subsequently, 3-ethylaminopropionitrile is continuously catalytically hydrogenated to N-ethyl-1,3-propanediamine in the fixed-bed reactor 9. The hydrogenation reaction rate control is 5.0 h -1 , and the product N-ethyl-1,3-propanediamine prepared by continuous hydrogenation is separated and collected by the gas-liquid separator 10. The ethylamine vapor separated by the separator 5 is condensed by the heat exchanger 6 and received by the buffer tank 13, and then returned to the plate micro-reactor 3 for recycling. When the liquid level of the ethylamine to be condensed and recycled in the buffer tank is above 30%, adjust the flow rate of the ethylamine (70% aqueous ethylamine solution) metering pump 1 so that the molar ratio of ethylamine to acrylonitrile is 1:1. The experiment runs stably. Samples are taken at 12 h, 24 h, 36 h, 48 h, 60 h, and 72 h of the reaction for gas phase analysis. The conversion rate of acrylonitrile is 100%, and the yield of N-ethyl-1,3-propanediamine is above 99.2%.

[0035] The experimental operation data of Example 1 are shown in Table 1.

[0036] Table 1 Experimental data of Example 1 running for 72 h

[0037]

[0038] Example 2

[0039] The difference from Example 1 is that:

[0040] The plate micro-reactor 3 and the delay reactor 4 are filled with nitrogen to a pressure of 1.0 MPa. The temperature of the plate micro-reactor 3 is set at 60 °C, the temperature of the delay reactor 4 is set at 90 °C, the temperature of the heat exchanger 6 is set at 5 °C, and the set temperature of the fixed-bed reactor 9 is 100 °C. The pressure of the fixed-bed reactor 9 is 1.5 MPa, and the gas-liquid volume ratio is 200:1. Ethylamine (70% aqueous ethylamine solution) and acrylonitrile (99%) are fed in a molar ratio of 1.2:1. The residence times of the reaction materials in the plate micro-reactor 3 and the delay reactor 4 are 2.0 s and 200 s respectively. After the reaction liquid is separated by the separator 5, a mixture of 3-ethylaminopropionitrile and the solvent is discharged from the bottom of the separator 5 and is transported to the static mixer 7 by the metering pump 19, and is fully mixed with a 5% mass concentration aqueous sodium hydroxide solution (alkali assistant) in the static mixer 7. The mass ratio of sodium hydroxide to 3-ethylaminopropionitrile is 1.0%. Then it is gas-liquid mixed with hydrogen through the gas-liquid micro-mixer 8, and then 3-ethylaminopropionitrile is continuously catalytically hydrogenated to produce N-ethyl-1,3-propanediamine in the fixed-bed reactor 9 at a controlled rate of 2.5 h-1. The product of N-ethyl-1,3-propanediamine prepared by continuous hydrogenation is separated and collected by the gas-liquid separator 10. The ethylamine vapor separated by the separator 5 is condensed by the heat exchanger 6 and received by the buffer tank 13, and then returned to the plate micro-reactor 3 for recycling. When the liquid level of the ethylamine to be condensed and recycled in the buffer tank is above 30%, the flow rate of the ethylamine (70% aqueous ethylamine solution) metering pump 1 is adjusted so that the molar ratio of ethylamine to acrylonitrile is 1:1. The experiment runs stably, and samples are taken at 12 h, 24 h, 36 h, 48 h, 60 h, and 72 h of the reaction respectively for gas phase analysis. The conversion rate of acrylonitrile is 100%, and the yield of N-ethyl-1,3-propanediamine is above 99.3%.

[0041] The experimental operation data of Example 2 are shown in Table 2.

[0042] Table 2 Experimental data of Example 2 for 72 h operation

[0043]

[0044] Example 3

[0045] The difference from Example 1 is that:

[0046] The plate micro-reactor 3 and the delay reactor 4 are filled with nitrogen to a pressure of 0.5 MPa. The temperature of the plate micro-reactor 3 is set at 50 °C, the temperature of the delay reactor 4 is set at 80 °C, the temperature of the heat exchanger 6 is set at 1 °C, and the set temperature of the fixed-bed reactor 9 is 70 °C. The pressure of the fixed-bed reactor 9 is 2.0 MPa, and the gas-liquid volume ratio is 150:1. The metering pump 1 for ethylamine (70% aqueous ethylamine solution) and the metering pump 2 for acrylonitrile (99%) are fed in a molar ratio of 1.15:1. The residence times of the reaction materials in the plate micro-reactor 3 and the delay reactor 4 are 1.5 s and 150 s respectively. After the reaction liquid is separated by the separator 5, a mixture of 3-ethylaminopropionitrile and solvent is discharged from the bottom of the separator 5 and is transported by the metering pump 19 to the static mixer 7, where it is fully mixed with a 4% mass concentration aqueous sodium hydroxide solution (alkali assistant). The mass ratio of sodium hydroxide to 3-ethylaminopropionitrile is 0.5%. Then it is gas-liquid mixed with hydrogen through the gas-liquid micro-mixer 8, and then 3-ethylaminopropionitrile is continuously catalytically hydrogenated to produce N-ethyl-1,3-propanediamine in the fixed-bed reactor 9 at a control rate of 3.75 h-1. The product of N-ethyl-1,3-propanediamine prepared by continuous hydrogenation is separated by the gas-liquid separator 10 and collected. The ethylamine vapor separated by the separator 5 is condensed by the heat exchanger 6 and received by the buffer tank 13, and then returned to the plate micro-reactor 3 for recycling. When the liquid level of the ethylamine to be condensed and recycled in the buffer tank is above 30%, the flow rate of the metering pump 1 for ethylamine (70% aqueous ethylamine solution) is adjusted so that the molar ratio of ethylamine to acrylonitrile is 1:1. The experiment runs stably, and samples are taken at 12 h, 24 h, 36 h, 48 h, 60 h, and 72 h of the reaction respectively for gas phase analysis. The conversion rate of acrylonitrile is 100%, and the yield of N-ethyl-1,3-propanediamine is above 99.3%.

[0047] The experimental operation data of Example 3 are shown in Table 3.

[0048] Table 3 Experimental data of Example 3 running for 72 h

[0049]

[0050] Example 4

[0051] The difference from Example 1 is that:

[0052] The plate microreactor 3 and the delay reactor 4 are filled with nitrogen to a pressure of 0.8 MPa. The temperature of the plate microreactor 3 is set at 50 °C, the temperature of the delay reactor 4 is set at 70 °C, the temperature of the heat exchanger 6 is set at 1 °C, and the set temperature of the fixed bed reactor 9 is 90 °C. The pressure of the fixed bed reactor 9 is 3.0 MPa, and the gas-liquid volume ratio is 150:1. The metering pump 1 for ethylamine (70% aqueous ethylamine solution) and the metering pump 2 for acrylonitrile (99%) are fed in a molar ratio of 1.1:1. The residence times of the reaction materials in the plate microreactor 3 and the delay reactor 4 are 1.2 s and 120 s respectively. After the reaction liquid is separated by the separator 5, a mixture of 3-ethylaminopropionitrile and solvent is discharged from the bottom of the separator 5 and is transported by the metering pump 19 to the static mixer 7, where it is fully mixed with an aqueous sodium hydroxide solution (alkali assistant) with a mass concentration of 4% in the static mixer 7. The mass ratio of sodium hydroxide to 3-ethylaminopropionitrile is 1.0%. Then it is gas-liquid mixed with hydrogen through the gas-liquid micro mixer 8, and subsequently 3-ethylaminopropionitrile is continuously catalytically hydrogenated to produce N-ethyl-1,3-propanediamine in the fixed bed reactor 9 at a controlled rate of 3.0 h-1. The product of N-ethyl-1,3-propanediamine prepared by continuous hydrogenation is separated by the gas-liquid separator 10 and collected. The ethylamine vapor separated by the separator 5 is condensed by the heat exchanger 6 and received by the buffer tank 13, and then returned to the plate microreactor 3 for recycling. When the level of the ethylamine to be condensed and recycled in the buffer tank is above 30%, the flow rate of the metering pump 1 for ethylamine (70% aqueous ethylamine solution) is adjusted so that the molar ratio of ethylamine to acrylonitrile is 1:1. The experiment runs stably, and samples are taken at 12 h, 24 h, 36 h, 48 h, 60 h, and 72 h of the reaction respectively for gas phase analysis. The conversion rate of acrylonitrile is 100%, and the yield of N-ethyl-1,3-propanediamine is above 99.3%. The experimental operation data of Example 4 are shown in Table 4.

[0053] Table 4 Experimental data of Example 4 running for 72 h

[0054]

[0055] Example 5

[0056] Specific implementation scheme for continuously preparing N-methyl-1,3-propanediamine. The reaction formula is as follows:

[0057]

[0058] The fixed-bed reactor 9 is filled with the catalyst Raney-Ni. The catalyst particle size is 1-3 mm, and the particle morphology is irregular granular. Open the nitrogen cylinder 14 to purge the entire reaction system and discharge the air. Fill the plate micro-reactor 3 and the delay reactor 4 with nitrogen to a pressure of 0.5 MPa. Set the temperature of the plate micro-reactor 3 to 40 °C, the temperature of the delay reactor 4 to 60 °C, the temperature of the heat exchanger 6 to -10 °C, and the set temperature of the fixed-bed reactor 9 to 60 °C. Open the hydrogen cylinder 12 and adjust the pressure of the fixed-bed reactor 9 to 5.0 MPa. Set the hydrogen flow rate of the gas mass flow controller 20 according to the feed amount of the hydrogenation raw material, and maintain the gas-liquid volume ratio at 120:1. Start the metering pump 1 for the monomethylamine ethanol solution (40%) and the metering pump 2 for acrylonitrile (99%), and feed according to the molar ratio of monomethylamine to acrylonitrile of 1.1:1. The residence times of the reaction materials in the plate micro-reactor 3 and the delay reactor 4 are 1.0 s and 100 s respectively. The area normalization purity of the product 3-methylaminopropionitrile obtained from the acrylonitrile ammoniation reaction is above 99.8%. After the reaction liquid is separated by the separator 5, a mixture of 3-methylaminopropionitrile and the solvent is discharged from the bottom of the separator 5 and is transported by the metering pump 19 to the static mixer 7, where it is fully mixed with the 2% mass concentration sodium hydroxide aqueous solution (alkali assistant). The mass ratio of sodium hydroxide to 3-methylaminopropionitrile is 0.2%. Then it is gas-liquid mixed with hydrogen through the gas-liquid micro-mixer 8, and then 3-methylaminopropionitrile is continuously catalytically hydrogenated to N-methyl-1,3-propanediamine in the fixed-bed reactor 9. The hydrogenation reaction rate control is 5.0 h-1. The product N-methyl-1,3-propanediamine prepared by continuous hydrogenation is separated and collected by the gas-liquid separator 10. The monomethylamine vapor separated by the separator 5 is condensed by the heat exchanger 6 and received by the buffer tank 13, and then returned to the plate micro-reactor 3 for recycling. When the level of the monomethylamine solution to be condensed and recycled in the buffer tank is above 30%, adjust the flow rate of the metering pump 1 for the monomethylamine ethanol solution (40%) to make the molar ratio of monomethylamine to acrylonitrile 1:1. The experiment runs stably, and samples are taken at 12 h, 24 h, 36 h, 48 h, 60 h, and 72 h of the reaction for gas phase analysis. The conversion rate of acrylonitrile is 100%, and the yield of N-methyl-1,3-propanediamine is above 99.5%.

[0059] The experimental operation data of Example 5 are shown in Table 5.

[0060] Table 5 Experimental data of Example 5 running for 72 h

[0061]

[0062] Example 6

[0063] The specific implementation scheme for the continuous preparation of N-propyl-1,3-propanediamine, the reaction formula is as follows:

[0064]

[0065] The reactor 9 is filled with Raney-Ni catalyst. The catalyst particle size is 1-3 mm, and the particle morphology is irregular granular. Open the nitrogen cylinder 14 to purge the entire reaction system and discharge the air. Fill the plate micro-reactor 3 and the delay reactor 4 with nitrogen to a pressure of 0.5 MPa. Set the temperature of the plate micro-reactor 3 to 60 °C, the temperature of the delay reactor 4 to 80 °C, the temperature of the heat exchanger 6 to 10 °C, and the set temperature of the fixed-bed reactor 9 to 80 °C. Open the hydrogen cylinder 12 and adjust the pressure of the fixed-bed reactor 9 to 5.0 MPa. Set the hydrogen flow rate of the gas mass flow controller 20 according to the feed rate of the hydrogenation raw material, and maintain the gas-liquid volume ratio at 120:1. Start the monopropylamine (99%) metering pump 1 and the acrylonitrile (99%) metering pump 2, and feed according to the molar ratio of monopropylamine to acrylonitrile of 1.1:1. The residence times of the reaction materials in the plate micro-reactor 3 and the delay reactor 4 are 1.0 s and 100 s respectively. The area normalization purity of the product 3-propylaminopropionitrile obtained from the acrylonitrile ammoniation reaction is above 99.9%. After the reaction liquid is separated by the separator 5, a mixture of 3-propylaminopropionitrile and solvent is discharged from the bottom of the separator 5 and is transported by the metering pump 19 to the static mixer 7, where it is fully mixed with a 2% mass concentration sodium hydroxide aqueous solution (alkali assistant). The mass ratio of sodium hydroxide to 3-propylaminopropionitrile is 0.2%. Then it is gas-liquid mixed with hydrogen through the gas-liquid micro-mixer 8, and then 3-propylaminopropionitrile is continuously catalytically hydrogenated to N-propyl-1,3-propanediamine in the fixed-bed reactor 9. The hydrogenation reaction rate control is 5.0 h-1. The product N-propyl-1,3-propanediamine prepared by continuous hydrogenation is separated and collected by the gas-liquid separator 10. The propylamine vapor separated by the separator 5 is condensed by the heat exchanger 6 and received by the buffer tank 13, and then returned to the plate micro-reactor 3 for recycling. When the liquid level of the buffer tank for the condensed and recycled monopropylamine solution is above 30%, adjust the flow rate of the monopropylamine (99%) metering pump 1 so that the molar ratio of monopropylamine to acrylonitrile is 1:1. The experiment runs stably. Samples are taken at 12 h, 24 h, 36 h, 48 h, 60 h, and 72 h of the reaction for gas phase analysis. The conversion rate of acrylonitrile is 100%, and the yield of N-propyl-1,3-propanediamine is above 99.36%.

[0066] The experimental operation data of Example 6 are shown in Table 6.

[0067] Table 6 Experimental data of Example 6 running for 72 h

[0068]

[0069]

[0070] Comparative Example 1

[0071] The difference from Example 1 is as follows:

[0072] Always keep the metering pump 1 of ethylamine (70% aqueous ethylamine solution) and the metering pump 2 of acrylonitrile (99%) feeding in a molar ratio of 1:1, and other conditions are the same as those in Example 1. The experiment runs stably. Samples are taken at 12h, 24h, 36h, 48h, 60h, and 72h of the reaction respectively for gas phase analysis. The conversion rate of acrylonitrile is 100%, the area normalization of 3-ethylaminopropionitrile is 97.4%, and the yield of N-ethyl-1,3-propanediamine is above 95.8%.

[0073] The experimental operation data of Comparative Example 1 are shown in Table 7.

[0074] Table 7 Experimental data of Comparative Example 1 running for 72h

[0075]

[0076] Since the feeding ratio of ethylamine and acrylonitrile in Comparative Example 1 is 1:1, during the addition process of ethylamine and acrylonitrile, the product is prone to continue to add to form macromolecular tertiary amine by-products, reducing the selectivity of the addition main product 3-ethylaminopropionitrile. In addition, these tertiary amine by-products contain two cyano groups, and it is difficult to fully hydrogenate them to amino groups, hindering the contact between the reactants and the active site center, resulting in a decrease in the activity and selectivity of the catalyst.

[0077] In summary, the method of the present invention adopts the form of a tandem connection of a plate microreactor and a fixed bed reactor to continuously prepare N-alkyl-1,3-propanediamine from fatty amines and acrylonitrile, which has the advantages of high production efficiency and high yield of the target product; the plate microreactor has a high specific surface area and a fine pore structure, high heat and mass transfer rates, precise temperature control, and high selectivity for 3-alkylaminopropionitrile prepared by continuous ammoxidation of acrylonitrile, and the area normalization purity is above 99.7%; the excessive fatty amine after ammoxidation of acrylonitrile is recycled, and the excessive amine after ammoxidation of acrylonitrile is recycled, avoiding the generation of other by-products from the amine during the hydrogenation reaction, and improving the hydrogenation selectivity of 3-alkylpropionitrile; secondly, the recycling of the amine can effectively reduce material loss and energy consumption, and improve the economy of the reaction process; the method of continuously preparing N-alkyl-1,3-propanediamine of the present invention has the safety and economy in the production process, and this process method is easy to realize continuous production and industrialization, and has high economic benefits.

Claims

1. An apparatus for continuously preparing N-ethyl-1,3-propanediamine, characterized in that: The device includes a plate microreactor (3), a delay reactor (4), a separator (5), a heat exchanger (6), a static mixer (7), a gas-liquid micro mixer (8), a fixed-bed reactor (9), a gas-liquid separator (10), a buffer tank (13) and a gas mass flow controller (20); Among them, the three inlets of the plate microreactor (3) are respectively connected to the fatty amine solution (1), acrylonitrile (2), and nitrogen gas cylinder (14). The outlet of the plate microreactor (3) is connected to the inlet of the delay reactor (4). The outlet of the delay reactor (4) is connected to the inlet of the separator (5). One outlet of the separator (5) is sequentially connected to the heat exchanger (6) and the buffer tank (13). The other outlet of the separator (5) is divided into two branches. One branch is emptied, and the other branch is connected to one inlet of the static mixer (7). The other inlet of the static mixer (7) is connected to the alkali assistant (11). The outlet of the static mixer (7) is connected to one inlet of the gas-liquid micro mixer (8). The alkali assistant and the product of the separator (5) are mixed in the static mixer (7) and then flow into the gas-liquid micro mixer (8). The other inlet of the gas-liquid micro mixer (8) is connected to the hydrogen gas cylinder (12). The inlet of the fixed-bed reactor (9) is connected to the inlet of the gas-liquid micro mixer (8). The outlet of the fixed-bed reactor (9) is connected to the inlet of the gas-liquid separator (10). The two outlets of the gas-liquid separator (10) are respectively the separated gas outlet and the liquid outlet.

2. The apparatus for continuously preparing N-ethyl-1,3-propanediamine according to claim 1, characterized in that: Metering pumps are respectively provided on the pipelines between the ethylamine solution pipeline and the plate microreactor (3), between the acrylonitrile pipeline and the plate microreactor (3), between the buffer tank (13) and the plate microreactor (3), between the alkali assistant (11) and the static mixer (7), and between the separator (5) and the static mixer (7); A gas mass flow controller (20) is provided on the pipeline between the hydrogen gas cylinder (12) and the gas-liquid micro mixer (8).

3. A method for continuously preparing N-ethyl-1,3-propanediamine using the device according to claim 1, characterized in that: The fatty amine solution and acrylonitrile react successively through the plate microreactor (3) and the delay reactor (4) to obtain a mixed reaction solution containing 3-alkylaminopropionitrile. The mixed reaction solution is separated by the separator (5). The separated 3-ethylaminopropionitrile and the alkali assistant solution are mixed in the static mixer (7), and then gas-liquid mixed with hydrogen through the gas-liquid micro mixer (8), and then continuously catalytically hydrogenated in the fixed-bed reactor (9) to generate N-alkyl-1,3-propanediamine.

4. The method according to claim 3, characterized in that: The amine vapor separated by the separator (5) is condensed by the heat exchanger (6) and received by the buffer tank (13), and then returned to the plate microreactor (3) for recycling.

5. The method according to claim 3, characterized in that: The fatty amine solution is an alcohol solution or an aqueous solution of an amine; the molar ratio of the fatty amine to acrylonitrile in the plate microreactor (3) is 1.05 - 1.5:

1.

6. The method according to claim 3, characterized in that: The residence time of the reaction solution in the plate microreactor (3) is 0.5 - 3.0 s; the reaction temperature is 30 - 90 °C; the reaction pressure is 0.2 - 2.0 Mpa.

7. The method according to claim 3, characterized in that: The temperature of the delay reactor (4) is 50 - 100 °C; the reaction pressure is 0.2 - 2.0 Mpa; the residence time of the reaction liquid in the delay reactor is 100 - 300 s.

8. The method according to claim 3, wherein: The cooling temperature of the heat exchanger (6) is 1 - 5 °C.

9. The method according to claim 3, characterized in that: The fixed-bed hydrogenation reaction conditions are as follows: reaction temperature is 40 - 120 °C; reaction pressure is 1.5 - 5.0 Mpa; the rate control is 1 - 10 h -1 ; the gas-liquid volume ratio is 80 - 400:

1.

10. The method according to claim 3, wherein: The alkali promoter is one of sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia water, and sodium methoxide; the concentration of the alkali promoter solution is 2 - 5%; the mass ratio of the alkali promoter to 3-alkylaminopropionitrile is 0.2 - 1%.

Images