A process for continuously synthesizing N-ethylethylenediamine

Abstract

The present invention belongs to the field of chemical technology, and relates to a process for continuously synthesizing N-ethylethylenediamine using ethyl chloride and ethylenediamine as raw materials. A microchannel continuous flow circulation feeding method is adopted to continuously synthesize N-ethylethylenediamine by alkyl halide ammonolysis, and after synthesis, it is purified and separated by distillation to obtain high-yield, high-purity N-ethylethylenediamine; and ethylenediamine is separated and recycled at the same time. After the reaction liquid of the present invention flows out, it is circulated and fed in a microchannel continuous phase as a third strand to avoid the chain reaction of N-ethylethylenediamine and ethyl chloride, and improve the reaction yield. The product and the raw material are separated and purified by means of vacuum distillation and rectification, and ethylenediamine is recycled and applied. The advantage of the present invention is that the generation of by-products can be avoided by microchannel continuation, mass transfer is enhanced, and reaction yield is improved, and the post-processing process can reduce energy consumption and cost.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry and relates to a process for continuously synthesizing N-ethylethylenediamine by taking ethyl chloride and ethylenediamine as raw materials. Background Art

[0002] N-ethylethylenediamine (NEED) is mainly used to produce low-toxic, high-efficiency, broad-spectrum antibiotics such as oxypiperazine penicillin, cefoperazone, cefoperazone and other pharmaceutical intermediates. It is also widely used in the synthesis of pesticides and surfactants. The continuous growth in the demand for cephalosporins has also greatly stimulated the growth in the demand for its important intermediate N-ethylethylenediamine. At present, the main methods for synthesizing N-ethylethylenediamine are aminoethyl sulfate method, ethanolamine method, acetic acid method, haloalkyl ammonolysis method, ethanol method and acrylonitrile method. Relatively speaking, haloalkyl ammonolysis method has the characteristics of simple and easy-to-obtain raw materials, mild reaction conditions, less environmental pollution and suitability for industrial-scale production. It has been widely studied and used as an industrial synthesis route for N-ethylethylenediamine.

[0003] The ammonolysis of alkyl halides mainly involves passing alkyl halides into 2-5 times the molar amount of ethylenediamine, adding an aqueous solution of NaOH to the reaction solution after the reaction, and then separating the organic phase from the aqueous phase. Then, the mixed phase of water and ethylenediamine in the organic phase is separated by azeotropic distillation. Finally, n-heptane is distilled off, and a qualified product N-ethylethylenediamine is obtained. In recent years, various domestic research institutes and production units have improved this synthesis process. In 2012, Xu Lufeng and others added ethylenediamine, methanol, and sodium methoxide to a high-pressure reactor, pressed in ethyl chloride, and heated to 40°C, with a pressure of 0.2 MPa, and kept warm for 4 hours. After the reaction was completed and sodium chloride was removed by filtration, the filtrate was distilled, and the 128-130°C fraction was collected to obtain the target product N-ethylethylenediamine.

[0004] Wei Wenlong et al. dripped ethyl bromide into ethylenediamine at 25°C, the molar ratio of ethylenediamine to ethyl bromide was 5:1, the dripping time was 40 min, and the temperature was kept for 2 h after the dripping was completed. After the reaction was completed, NaOH was added to the reaction solution and the stirring was continued for 30 min. Then the organic layer was separated, the water layer was extracted with cyclohexane, the organic layer and the extract phase were collected, the cyclohexane was recovered by atmospheric distillation, and the fractions of 128~130°C were collected by distillation. The product yield reached 64.6%. Chen Xiangjun et al. improved the post-treatment method. First, ethyl bromide was dripped into ethylenediamine, stirred at room temperature for 3 hours, then heated to 40 degrees for reaction for 3 hours, and then refluxed for 2 hours. After the reaction was completed, hydrochloric acid was added and distilled under reduced pressure at 70°C. The distillate after distillation was mainly N-ethylethylenediamine, and the components >106°C, i.e., N-ethylethylenediamine containing water, were collected by distillation. Then, benzene is used for azeotropic dehydration, and powdered NaOH is added for dehydration. After separation of the organic phase, fractionation is performed, and the fraction at 128-132° C. is collected to obtain N-ethylethylenediamine. The disadvantage of the above two schemes is that it is difficult to separate water from ethylenediamine. It is difficult to separate ethylenediamine and water by means of atmospheric distillation, and a third component needs to be added for distillation, which consumes a lot of energy and is not conducive to production.

[0005] The ammonolysis reaction of alkyl halides requires the use of an excess of ethylenediamine to avoid the formation of disubstituted by-products. However, >20% of disubstituted by-products are still generated during the reaction, thus requiring a preparation method with fewer by-products and that is safe and environmentally friendly. Summary of the invention

[0006] The object of the present invention is to provide a process for continuously synthesizing N-ethylethylenediamine in view of the deficiency of the current chloroalkane ammonolysis method for synthesizing N-ethylethylenediamine.

[0007] To achieve the above purpose, the present invention adopts the following technical solution:

[0008] A process for continuously synthesizing N-ethylethylenediamine comprises the following steps: adopting a microchannel continuous flow circulation feeding method to continuously synthesize N-ethylethylenediamine by a haloalkyl ammonolysis method; purifying and separating the N-ethylethylenediamine by a distillation method after the synthesis to obtain high-yield and high-purity N-ethylethylenediamine; and separating the ethylenediamine for recycling.

[0009] The microchannel continuous flow reaction device used in the microchannel continuous flow circulation includes a microreactor, a delayed pipeline reactor, a storage tank and a back pressure valve which are sequentially connected through pipelines; a diverting three-way valve is arranged on the pipeline between the delayed pipeline reactor and the storage tank, and the circulating material and the outflowing material form a circulation path through the diverting three-way valve.

[0010] The reactor is connected in a cross shape by a dispersion channel and a continuous phase reaction channel; one end of the continuous phase reaction channel is a circulating liquid inlet (103) connected to a storage tank through a pipeline, and the other end is a reactor outlet (104) connected to a time-delay pipeline reactor through a pipeline; both ends of the dispersion channel are feed channels (105, 106) for raw materials ethyl chloride and ethylenediamine, respectively, and the two feed channels are connected to the dispersion phase inlet pipeline (101, 102) respectively; the ethyl chloride dispersion phase inlet pipeline is sequentially connected to a high-pressure buffer tank and an ethyl chloride storage tank through a pipeline.

[0011] The inlet and outlet channels of the microchannel reactor are 1.5 mm in size, the inner diameter of the dispersion hole is 0.2 mm, and the number of dispersion tube bundles depends on the flow rate. The inner diameter of the delay pipe is 2 mm, and the wall thickness is 1 mm.

[0012] An ethyl chloride high-pressure buffer tank is arranged behind the ethyl chloride storage tank, and the ethyl chloride liquid in the buffer tank is pumped into the microreactor simultaneously with the feed pump and ethylenediamine. A gas cylinder pressure reducing gauge and a mass flow controller are arranged between the ethyl chloride storage tank and the buffer tank to adjust the pressure and flow.

[0013] Specifically:

[0014] Ethyl chloride and excess anhydrous ethylenediamine are pumped into the microchannel reactor from the ethyl chloride high-pressure buffer tank through two dispersed phase inlet pipelines (101, 102) for alkylation reaction by a feed pump. The reaction product liquid flows out from the reactor outlet (104) through the pipeline and enters the delayed pipeline reactor in sequence. The reaction product liquid is then circulated to the reactor to react with the raw material by controlling the circulation ratio of the reaction product liquid through the diversion three-way valve. The circulated reaction product liquid enters the storage tank and then returns to the microreactor through the circulating liquid inlet (103) of the microreactor to mix with the raw material until the ethyl chloride is completely consumed to obtain a mixed solution containing N-ethylethylenediamine and ethylenediamine;

[0015] (2) separating and purifying the raw material ethylenediamine, the product N-ethylethylenediamine and the disubstituted and polysubstituted by-products by means of vacuum distillation and rectification of the mixed solution of N-ethylethylenediamine and ethylenediamine obtained above; thereby obtaining high-yield and high-purity N-ethylethylenediamine;

[0016] (3) Add alkali to the ethylenediamine hydrochloride and N-ethylethylenediamine hydrochloride obtained in the process of vacuum distillation to treat them, so as to obtain ethylenediamine of qualified quality, which is directly combined with the ethylenediamine obtained after the vacuum distillation and rectification purification.

[0017] In the step (1), an ethyl chloride high-pressure buffer tank is provided behind the ethyl chloride storage tank, and the ethyl chloride liquid in the buffer tank is pumped into the microreactor simultaneously with ethylenediamine using a feed pump; a gas cylinder pressure reducing gauge and a mass flow controller are provided between the ethyl chloride storage tank and the buffer tank to adjust the pressure and flow; the ethyl chloride output pressure during the reaction process is 0.05-0.1 MPa; the reaction temperature of the haloalkyl ammonolysis of ethylenediamine and ethyl chloride is 30-40° C.; the molar ratio of ethylenediamine to ethyl chloride is 3:1-2.5:1; and the circulation ratio of the returned reaction liquid circulation process is 8-10:1.

[0018] In the step (2), the vacuum distillation and rectification are to first separate ethylenediamine, N-ethylethylenediamine and by-products by vacuum distillation, and then add an azeotropic agent into the system for rectification to separate ethylenediamine, and then rectify to achieve purification and separation of N-ethylethylenediamine and by-products.

[0019] From the above, it can be seen that in the vacuum distillation step of the separation and purification process, the distillate is ethylenediamine, N-ethylethylenediamine, disubstituted by-products and polysubstituted by-products, and the bottom liquid is 90-95% ethylenediamine hydrochloride and 5-10% N-ethylethylenediamine hydrochloride.

[0020] The distillation step of the separation and purification process separates ethylenediamine, N-ethylethylenediamine, disubstituted by-products and polysubstituted by-products. An azeotropic agent is added and azeotropic distillation is used to first separate ethylenediamine, and then the azeotropic agent is separated. The azeotropic agent can be recycled. Finally, the product and by-products are separated by ordinary distillation.

[0021] The temperature of the reduced pressure distillation is 80-100°C, and the vacuum pressure of the reduced pressure distillation is 0.095-0.1Mpa;

[0022] The distillation tower has 30-40 plates and a temperature of 128-130°C.

[0023] A two-phase liquid separator is provided at the top discharge port of the distillation tower. The liquid separator is first filled with an azeotropic agent. As the distillation process occurs, the heavy component ethylenediamine is discharged from the lower discharge port, and the azeotropic agent flows back into the tower from above.

[0024] The azeotropic agent is n-heptane and cyclohexane, and the amount of the azeotropic agent added is about 1 / 3 of the volume of the distilled liquid; the tower top temperatures of ethylenediamine and n-heptane, ethylenediamine, n-heptane and cyclohexane are 86-98° C. and 74-80° C. respectively.

[0025] Adding a base in an equal molar amount to ethyl chloride to the ethylenediamine hydrochloride and N-ethylethylenediamine hydrochloride in the process of vacuum distillation to treat them, to obtain qualified ethylenediamine that can be applied, and 5-10% of N-ethylethylenediamine is recycled together with the ethylenediamine; wherein the base is a methanol solution containing 30% sodium methoxide (i.e., 30% sodium methoxide + 70% methanol) or an aqueous solution of sodium hydroxide.

[0026] The method for recovering ethylenediamine from sodium methoxide comprises the following steps: firstly, using a 30% methanol solution of sodium methoxide in an equimolar amount to hydrogen chloride to neutralize hydrogen chloride, separating the sodium chloride waste residue generated in the neutralization process from the reaction solution by filtering, firstly using atmospheric distillation to remove most of the methanol from the separated ethylenediamine-methanol mixed solution, and then using rectification to remove all the methanol, and finally obtaining ethylenediamine containing a small amount of N-ethylethylenediamine, thereby completing the application experiment.

[0027] The methanol recovered from the atmospheric distillation and rectification process can be used to repeatedly wash the filtered sodium chloride waste residue to remove the ethylenediamine in the waste residue until the washing liquid is neutral. The washing times are 2-3 times.

[0028] The sodium hydroxide recovery method is to use sodium hydroxide as a neutralizing agent to recover ethylenediamine, first add a sodium hydroxide aqueous solution with a molar amount of 50% of hydrogen chloride to complete the neutralization reaction. The oil phase and the aqueous phase are obtained by preliminary filtration and phase separation, the aqueous phase is a sodium chloride aqueous solution, and the oil phase is a mixed solution of ethylenediamine containing water and sodium chloride. Sodium hydroxide solid is gradually added to the obtained oil phase to saturation, the moisture therein is adsorbed and the dissolved sodium chloride is precipitated, and the filtration phase separation process is continued. The obtained aqueous phase is applied to the neutralization process, and the obtained oil phase is collected by vacuum distillation to distill out components, the components contain water and ethylenediamine, and finally toluene is used as the entrainer of azeotropic distillation to remove water, and the ethylenediamine containing a small amount of N-ethylethylenediamine of qualified quality is obtained.

[0029] Among them, the sodium hydroxide solution obtained by secondary filtration during the sodium hydroxide recovery process can be used as a neutralizing agent to complete the neutralization reaction and complete the application process.

[0030] Among them, the azeotropic temperature of toluene and water is 84-104°C, and toluene and water can be separated by phase separation; the azeotropic temperature of toluene and ethylenediamine is 104-116°C, and the extracted mixed liquid is used as the azeotropic agent for the next distillation.

[0031] The water content of the ethylenediamine recovered by the two recovery methods shall not be higher than 2%, and the methanol content shall not be higher than 5%, otherwise the ethylenediamine application process will be affected.

[0032] Beneficial effects of the present invention:

[0033] The present invention provides an alkylation synthesis process, a separation and purification process of products and raw materials, and an ethylenediamine recovery and utilization process; wherein the alkylation synthesis process adopts continuous microchannel circulation feeding to synthesize N-ethylethylenediamine. On the one hand, the microreactor can increase the mass transfer of the reaction, avoid back mixing, and avoid the generation of disubstituted by-products; on the other hand, the reaction liquid circulation feeding can also improve the selectivity of the reaction; specifically:

[0034] 1. The alkylation process of the present invention adopts a microchannel continuous circulation feeding method to increase mass transfer, avoid back mixing, avoid the formation of by-products, improve the reaction yield, reduce the difficulty of post-treatment, reduce energy consumption, reduce the amount of three wastes, and save costs.

[0035] 2. The N-ethylethylenediamine synthesis process of the present invention is clear, comprehensive and systematic, including an alkylation reaction process, a product and raw material separation and purification process, and an ethylenediamine recovery and utilization process, and is a green and environmentally friendly process suitable for industrialization.

[0036] 3. In the alkylation process and the vacuum distillation process, the present invention does not add solvents and acid aqueous solution substances, which reduces the difficulty of separation in the refining process; at the same time, the combination of vacuum distillation and azeotropic distillation, on the one hand, reduces the energy consumption of separating raw materials and products, and on the other hand, also provides convenient conditions for the ethylenediamine recovery process.

[0037] 4. The present invention uses sodium methoxide and sodium hydroxide to recover ethylenediamine in the recovery process, and determines the quality requirements of the raw material liquid in the recovery process of ethylenediamine. Finally, the ethylenediamine recovery experiment is completed, and the results are similar to those of fresh ethylenediamine. At the same time, the systematic recovery of ethylenediamine greatly reduces the cost of raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The figure is a simplified process flow diagram of the alkylation reaction of the present invention.

[0039] Figure 2 for Figure 1 Schematic diagram of the microreactor structure.

[0040] Figure 3 for Figure 2 Cross section of the dispersion channel of the microreactor.

[0041] Among them, 1 is a microreactor, two dispersed phase inlet pipelines (101, 102), a continuous phase inlet pipeline (103), a reactor outlet pipeline (104) and two dispersed channels (105, 106), 2 is an ethyl chloride storage tank, 3 is a high-pressure buffer tank, 4 is a first constant flow pump, 5 is a second constant flow pump, 6 is a third constant flow pump, 7 is a time-delay reactor, 8 is a diversion three-way valve, and 9 is a storage tank. DETAILED DESCRIPTION

[0042] Compared with the reported process, the full-process process of synthesizing N-ethylethylenediamine of the present invention has a simple process flow and low energy consumption, and ensures product quality while having a high conversion rate; the whole process is systematic and safe, and provides a solid reference basis for the industrialization process.

[0043] The present invention includes a microchannel continuous alkylation synthesis process for synthesizing N-ethylethylenediamine, separation and purification of products and raw materials, and recovery and application of ethylenediamine; wherein, the microchannel continuous synthesis of N-ethylethylenediamine can enhance mass transfer, improve reaction yield, reduce the difficulty of post-treatment, reduce energy consumption, reduce the amount of three wastes, and save costs. Since the excess of ethylenediamine is large, and ethylenediamine and N-ethylethylenediamine have similar boiling points and a relative volatility close to 1, distillation requires a very high number of plates, and the energy consumption is too high. A method of first separating ethylenediamine hydrochloride by vacuum distillation and then separating ethylenediamine by azeotropic distillation is adopted to reduce costs and save energy consumption to the greatest extent. Finally, ethylenediamine hydrochloride is neutralized into ethylenediamine, and the application is completed, thereby realizing a full-process efficient and environmentally friendly technical solution for the synthesis, post-treatment and application of N-ethylethylenediamine.

[0044] Example 1

[0045] like Figure 1-3 As shown, the microchannel continuous flow reaction device used in the microchannel continuous flow circulation includes a microreactor, a delayed pipeline reactor, a storage tank and a back pressure valve which are sequentially connected through pipelines; a diverter three-way valve is arranged on the pipeline between the delayed pipeline reactor and the storage tank, and the circulating material and the outflowing material form a circulation path through the diverter three-way valve.

[0046] The reactor is connected in a cross shape by a dispersion channel and a continuous phase reaction channel; one end of the continuous phase reaction channel is a circulating liquid inlet (103) connected to a storage tank through a pipeline, and the other end is a reactor outlet (104) connected to a time-delay pipeline reactor through a pipeline; both ends of the dispersion channel are feed channels (105, 106) for raw materials ethyl chloride and ethylenediamine, respectively, and the two feed channels are connected to the dispersion phase inlet pipeline (101, 102) respectively; the ethyl chloride dispersion phase inlet pipeline is sequentially connected to a high-pressure buffer tank and an ethyl chloride storage tank through a pipeline.

[0047] A feed pump is arranged on each of the above-mentioned inlet pipelines.

[0048] Example 2

[0049] (1) Alkylation reaction process: Using the device of the embodiment, the ethyl chloride storage tank is connected to the high-pressure buffer tank through a pipeline, and the ethyl chloride liquid is pumped into the microchannel reactor through the first horizontal flow pump and the ethylenediamine is pumped into the microchannel reactor through the two dispersed phase inlet pipelines (101, 102) through the second horizontal flow pump.

[0050] By controlling the feed flow rate, the molar ratio of ethylenediamine to ethyl chloride is adjusted to 3:1, and the feed mass ratio of ethyl chloride to ethylenediamine is 0.36:1. The alkylation reaction is carried out at a reaction temperature of 40°C. The reaction product liquid flows out from the reactor outlet (104) through the pipeline and enters the delayed pipeline reactor in sequence. Then, the reaction product liquid is divided into a circulating material and an outflowing material according to a certain circulation ratio through a diverting three-way valve. The circulating material enters a storage tank and then returns to the microreactor through the circulating liquid inlet (103) of the microreactor to mix with the raw material. The circulation ratio of the returned reaction liquid is controlled to be 9:1 until all the ethyl chloride is consumed. The outflowing material is detected by gas chromatography: the purity of N-ethylethylenediamine is 92.1%, and the purity of the two disubstituted by-products is 2.5% and 5.4% respectively (ethylenediamine accounts for about 52.03% in the reaction liquid).

[0051] (2) Separation and purification process of products and raw materials:

[0052] ① Vacuum distillation process: The reaction liquid obtained from the alkylation process is transferred to the oil bath heating device. First, the oil bath temperature is set to 70-80℃, and the vacuum device is turned on at the same time. The vacuum degree is 0.095-0.1Mpa. When the oil bath temperature rises to 58℃, distillate begins to be distilled out of the condenser outlet. As the temperature rises, the liquid discharge rate gradually increases. Vacuum distillation is carried out under 80℃ oil bath for 1h, and the distillate production rate slows down. The oil bath temperature is raised to 110℃, and the residual amine that is not bound by acid is evaporated as much as possible, and the distillate is collected. According to the results of gas phase analysis, the content of ethylenediamine in the distillate is 28.9%, the content of N-ethylethylenediamine is 64.8%, and the contents of the two disubstituted by-products are 1.8% and 4.5%, respectively. The bottom liquid is the bound acid ethylenediamine and a small amount of N-ethylethylenediamine, of which the content of ethylenediamine is 94.1% and the content of N-ethylethylenediamine is 5.9%.

[0053] ② Azeotropic distillation process: The distillate obtained after the vacuum distillation is mixed with the entrainer n-heptane, wherein the volume ratio of the distillate to the entrainer is 3:1. The components are separated and purified by distillation, and ethylenediamine is separated by azeotropic distillation. N-ethylethylenediamine is separated by conventional distillation. Specifically, n-heptane and ethylenediamine are azeotropic at 86-98°C. According to the phenomenon that n-heptane and ethylenediamine are immiscible, ethylenediamine is separated from the lower layer, and the light component n-heptane flows back into the tower. When all ethylenediamine is removed, n-heptane is continuously extracted by distillation at a temperature of about 98°C. Subsequently, the product N-ethylethylenediamine is extracted at a top temperature of 128-130°C of the distillation tower. After gas phase detection, the purity of the distilled ethylenediamine is 99.3%, and the purity of the product N-ethylethylenediamine is 99.5%. After calculation, the yield of a single batch of products is 87.3%.

[0054] (3) Ethylene diamine recovery and application process: Add 360g of methanol solution containing 30% sodium methoxide to the bottom liquid obtained in the vacuum distillation process for neutralization, stir at room temperature and filter to remove solid sodium chloride, and use methanol to wash the filter cake 3 times. Collect the filtrate and washing liquid, first distill to remove methanol under normal pressure under 85℃ water bath heating, and then use ordinary distillation to remove methanol. Use a distillation tower with about 20 plates to separate the methanol component with a top temperature of 65℃. The proportion of methanol removed in the two steps is about 74% and 26%. According to gas chromatography detection, the content of ethylenediamine in the recovered liquid is 93.9%, N-ethylethylenediamine is 5.6%, and the content of methanol is 0.5%, and the recovery rate of ethylenediamine is 98%.

[0055] Example 3

[0056] The alkylation reaction process and the separation and purification process of the product and the raw material are the same as those in Example 2. In the process of ethylenediamine recovery and application, this embodiment uses sodium hydroxide as a neutralizing agent to remove hydrogen chloride. First, 160 g of 50% sodium hydroxide aqueous solution is added to the bottom liquid obtained in the vacuum distillation process, stirred at room temperature for 1 hour, and then filtered at room temperature to remove the generated sodium chloride, and then the water phase and the oil phase are preliminarily separated. 80 g of sodium hydroxide solid is added to the oil phase for dry water treatment, stirred for 30 minutes, filtered and subjected to phase separation. The obtained water phase is used as a neutralizing agent to apply the neutralization process, and the obtained oil phase is heated in an oil bath at 100°C and distilled under reduced pressure at a vacuum degree of 0.095-0.1 Mpa to collect the distillate components, which contain water and ethylenediamine. Finally, toluene is used as an azeotropic agent for azeotropic distillation to remove water, and toluene and water are collected at 84-104°C. Toluene and water can be separated by phase separation; toluene and ethylenediamine are collected at 104-116°C, and the obtained mixed liquid is used as an azeotropic agent for the next distillation, and ethylenediamine is collected at 116°C. A mixed liquid with an N-ethylethylenediamine content of 6.5% and an ethylenediamine content of 93.5% is obtained, and the recovery rate of ethylenediamine is 91.7%.

[0057] Example 4

[0058] (1) Alkylation reaction process: Using the device of the embodiment, the ethyl chloride storage tank is connected to the high-pressure buffer tank through a pipeline, and the ethyl chloride liquid is pumped into the microchannel reactor through the first horizontal flow pump and the ethylenediamine is pumped into the microchannel reactor through the two dispersed phase inlet pipelines (101, 102) through the second horizontal flow pump.

[0059] By controlling the feed flow rate, the molar ratio of ethylenediamine to ethyl chloride is adjusted to 3:1, and the feed mass ratio of ethyl chloride to ethylenediamine is 0.36:1. The alkylation reaction is carried out at a reaction temperature of 10°C. The reaction product liquid flows out from the reactor outlet (104) through the pipeline and enters the delayed pipeline reactor in sequence. Then, the reaction product liquid is divided into a circulating material and an outflowing material according to a certain circulation ratio through a diverting three-way valve. The circulating material enters the storage tank, and the circulating material entering the storage tank returns to the microreactor through the circulating liquid inlet (103) of the microreactor to mix with the raw material. The circulation ratio of the returned reaction liquid is controlled to be 12:1 until the ethyl chloride is completely consumed. The outflowing material is detected by gas chromatography: the purity of N-ethylethylenediamine is 93.0%, and the purity of the two disubstituted by-products is 2.1% and 4.9% respectively (ethylenediamine accounts for about 54.4% in the reaction liquid).

[0060] Example 5

[0061] (1) Alkylation reaction process: Using the device of the embodiment, the ethyl chloride storage tank is connected to the high-pressure buffer tank through a pipeline, and the ethyl chloride liquid is pumped into the microchannel reactor through the first horizontal flow pump and the ethylenediamine (ethylenediamine content is 93.9%) recovered in Example 2 is pumped into the microchannel reactor through the two dispersed phase inlet pipelines (101, 102) through the second horizontal flow pump.

[0062] By controlling the feed flow rate, the molar ratio of ethylenediamine to ethyl chloride is adjusted to 3:1, and the feed mass ratio of ethyl chloride to ethylenediamine is 0.34:1. The alkylation reaction is carried out at a reaction temperature of 40°C. The reaction product liquid flows out from the reactor outlet (104) through the pipeline and enters the delayed pipeline reactor in sequence. Then, the reaction product liquid is divided into a circulating material and an outflowing material according to a certain circulation ratio through a diverting three-way valve. The circulating material enters the storage tank. The circulating material entering the storage tank returns to the microreactor through the pipeline through the circulating liquid inlet (103) of the microreactor and is mixed with the raw material. The circulation ratio of the returned reaction liquid is controlled to be 9:1 until the ethyl chloride is completely consumed. The outflowing material is detected by gas chromatography: the purity of N-ethylethylenediamine is 91.7%, and the purity of the two disubstituted byproducts is 2.7% and 5.6% respectively (ethylenediamine accounts for about 51.6% in the reaction liquid).

[0063] (2) Separation and purification process of products and raw materials:

[0064] 1. Vacuum distillation process: The same as the process in Example 2, the obtained alkylation reaction liquid is poured into a vacuum distillation apparatus, and the unbound acid amine is distilled out. According to the gas phase analysis results, the content of ethylenediamine in the distillate is 28%, the content of N-ethylethylenediamine is 65.2%, and the contents of the two disubstituted by-products are 2.1% and 4.7%, respectively. The bottom liquid is the bound acid ethylenediamine and a small amount of N-ethylethylenediamine, wherein the content of ethylenediamine is 93.4%, and the content of N-ethylethylenediamine is 6.6%.

[0065] ② Azeotropic distillation process: The distillate obtained after the reduced pressure distillation is mixed with the azeotropic agent n-heptane, and the mixing volume ratio is 3:1. The components are separated and purified by distillation, and ethylenediamine is separated by azeotropic distillation. N-ethylethylenediamine is separated by conventional distillation. Specifically, n-heptane and ethylenediamine are azeotropic at 86-98°C. According to the phenomenon that n-heptane and ethylenediamine are not miscible, ethylenediamine is separated from the lower layer, and the light component n-heptane flows back into the tower. When all ethylenediamine is removed, n-heptane is continuously extracted by distillation at a temperature of about 98°C. Subsequently, the product N-ethylethylenediamine is extracted at a top temperature of 128-130°C of the distillation tower. After gas phase detection, the purity of the distilled ethylenediamine is 99.3%, and the purity of the product N-ethylethylenediamine is 99.5%. After calculation, the yield of a single batch of products is 86.8%.

[0066] Example 6

[0067] (1) Alkylation reaction process: Using the device of the embodiment, the ethyl chloride storage tank is connected to the high-pressure buffer tank through a pipeline, and the ethyl chloride liquid is pumped into the microchannel reactor through the first horizontal flow pump and the ethylenediamine (ethylenediamine content is 93.5%) recovered in Example 3 is pumped into the microchannel reactor through the two dispersed phase inlet pipelines (101, 102) through the second horizontal flow pump.

[0068] By controlling the feed flow rate, the molar ratio of ethylenediamine to ethyl chloride is adjusted to 3:1, and the feed mass ratio of ethyl chloride to ethylenediamine is 0.34:1. The alkylation reaction is carried out at a reaction temperature of 40°C. The reaction product liquid flows out from the reactor outlet (104) through the pipeline and enters the delayed pipeline reactor in sequence. Then, the reaction product liquid is divided into a circulating material and an outflowing material according to a certain circulation ratio through a diverting three-way valve. The circulating material enters the storage tank. The circulating material entering the storage tank returns to the microreactor through the pipeline through the circulating liquid inlet (103) of the microreactor and is mixed with the raw material. The circulation ratio of the returned reaction liquid is controlled to be 9:1 until the ethyl chloride is completely consumed. The outflowing material is detected by gas chromatography: the purity of N-ethylethylenediamine is 91.1%, and the purity of the two disubstituted by-products is 2.9% and 6.0% respectively (ethylenediamine accounts for about 52.9% in the reaction liquid).

[0069] (2) Separation and purification process of products and raw materials:

[0070] 1. Vacuum distillation process: same as the process in Example 2, pour the obtained alkylation reaction liquid into the vacuum distillation apparatus, steam out the unbound acid amine, and collect the distillate. According to the gas phase analysis result, the content of ethylenediamine in the distillate is 28.5%, the content of N-ethylethylenediamine is 65.0%, and the contents of two disubstituted by-products are 2.2% and 4.3% respectively. The bottom liquid is the bound acid ethylenediamine and a small amount of N-ethylethylenediamine, wherein the content of ethylenediamine is 94.1%, and the content of N-ethylethylenediamine is 5.9%.

[0071] ② Azeotropic distillation process: The distillate after vacuum distillation is mixed with the azeotropic agent n-heptane, and the mixing volume ratio is 3:1. The components are separated and purified by distillation, and ethylenediamine is separated by azeotropic distillation. N-ethylethylenediamine is separated by conventional distillation. Specifically, n-heptane and ethylenediamine are azeotropic at 86-98°C. According to the phenomenon that n-heptane and ethylenediamine are immiscible, ethylenediamine is separated from the lower layer, and the light component n-heptane flows back into the tower. When all ethylenediamine is removed, n-heptane is continuously extracted by distillation at a temperature of about 98°C. Subsequently, the product N-ethylethylenediamine is extracted at a top temperature of 128-130°C in the distillation tower. After gas phase detection, the purity of the distilled ethylenediamine is 99.4%, and the purity of the product N-ethylethylenediamine is 99.5%. After calculation, the yield of a single batch of products is 87.0%.

[0072] Comparative Example

[0073] First, add 360g of ethylenediamine to the reactor, and use a water bath heating device to adjust the raw material liquid to 40°C. Use a pressure regulating valve and a mass flow controller to adjust the ethyl chloride flowing out of the ethyl chloride storage tank. And pass the ethyl chloride liquid into the reactor through a feed pump, control a certain feed rate, ensure that the feed time is 1h, adjust the reaction molar ratio of ethylenediamine: ethyl chloride to 3:1, and pass a total of 130g of ethyl chloride. Then keep warm and stir at 40°C for 30min to complete the reaction of unconverted ethyl chloride. The gas chromatography detection shows that the conversion rate of ethyl chloride is 100%, the purity of N-ethylethylenediamine in the product is 83.6%, and the purity of the two disubstituted by-products is 5.5% and 10.9%, respectively. After post-treatment, the yield of a single batch of products is 74.5%.

Claims

1. A process for continuously synthesizing N-ethylethylenediamine, characterized in that: The N-ethylethylenediamine is synthesized by continuous ammonolysis of alkyl halides by microchannel continuous flow circulation feeding method, and after synthesis, it is purified and separated by vacuum distillation and rectification to obtain N-ethylethylenediamine; at the same time, the ethylenediamine is separated and recycled; The microchannel continuous flow reaction device used in the microchannel continuous flow circulation comprises a microreactor, a time-delay pipeline reactor, a storage tank and a back pressure valve which are sequentially connected through pipelines; a diverting three-way valve is arranged on the pipeline between the time-delay pipeline reactor and the storage tank, and the circulating material and the outflowing material form a circulation path through the diverting three-way valve; The microreactor is connected in a cross shape by a dispersion channel and a continuous phase reaction channel; one end of the continuous phase reaction channel is a circulating liquid inlet connected to a storage tank through a pipeline, and the other end is a microreactor outlet connected to a time-delay pipeline reactor through a pipeline; the two ends of the dispersion channel are respectively feed channels for raw materials ethyl chloride and ethylenediamine, and the two feed channels are respectively connected to the dispersion phase inlet pipeline; the ethyl chloride dispersed phase inlet pipeline is sequentially connected to a high-pressure buffer tank and an ethyl chloride storage tank through a pipeline; The specific process is: (1) Ethyl chloride and excess anhydrous ethylenediamine are pumped into a microreactor through two dispersed phase inlet pipelines by a feed pump to perform an alkylation reaction. The reaction liquid flows out from the outlet of the microreactor through the pipeline and enters the delayed pipeline reactor in sequence. The reaction liquid is then circulated to the microreactor to react with the raw material by controlling the circulation ratio of the reaction liquid through a diversion three-way valve. The circulated reaction liquid enters a storage tank and then returns to the microreactor through the circulating liquid inlet of the microreactor to mix with the raw material until the ethyl chloride is completely consumed, thereby obtaining a mixed solution containing N-ethylethylenediamine and ethylenediamine; (2) separating and purifying the raw material ethylenediamine, the product N-ethylethylenediamine, and the disubstituted and polysubstituted by-products by using vacuum distillation and rectification to obtain the N-ethylethylenediamine; (3) adding alkali to the ethylenediamine hydrochloride and N-ethylethylenediamine hydrochloride obtained in the process of vacuum distillation to obtain ethylenediamine, and combining the ethylenediamine obtained after the vacuum distillation and rectification purification to directly use the mixture; In the step (2), the vacuum distillation and rectification are to first separate ethylenediamine, N-ethylethylenediamine and by-products by vacuum distillation, and then add an azeotropic agent into the system for rectification to separate ethylenediamine, and then rectify to achieve purification and separation of N-ethylethylenediamine and by-products.

2. The process for continuously synthesizing N-ethylethylenediamine according to claim 1, characterized in that: In the step (1), an ethyl chloride high-pressure buffer tank is provided behind the ethyl chloride storage tank, and the ethyl chloride liquid in the buffer tank is pumped into the microreactor simultaneously with ethylenediamine using a feed pump; a gas cylinder pressure reducing gauge and a mass flow controller are provided between the ethyl chloride storage tank and the buffer tank to adjust the pressure and flow; the ethyl chloride output pressure during the reaction process is 0.05-0.1 MPa; the reaction temperature of the haloalkyl ammonolysis of ethylenediamine and ethyl chloride is 30-40° C.; the molar ratio of ethylenediamine to ethyl chloride is 3:1-2.5:1; and the circulation ratio of the returned reaction liquid circulation process is 8-10:

1.

3. The process for continuously synthesizing N-ethylethylenediamine according to claim 1, characterized in that: The temperature of the reduced pressure distillation is 80-100°C, and the vacuum pressure of the reduced pressure distillation is 0.095-0.1Mpa; the number of the distillation plates is 30-40, and the temperature is 128-130°C.

4. The process for continuously synthesizing N-ethylethylenediamine according to claim 3, characterized in that: The azeotropic agent is n-heptane or cyclohexane, and the amount of the azeotropic agent added is 1 / 3 of the volume of the distilled liquid; the top temperature of the tower where ethylenediamine and n-heptane are distilled is 86-98°C, and the top temperature of the tower where ethylenediamine and cyclohexane are distilled is 74-80°C.

5. The process for continuously synthesizing N-ethylethylenediamine according to claim 1, characterized in that: Add a base in an amount equal to the molar amount of ethyl chloride to the ethylenediamine hydrochloride and N-ethylethylenediamine hydrochloride in the process of vacuum distillation to treat them, so as to obtain qualified ethylenediamine that can be applied, and 5-10% of N-ethylethylenediamine is recycled together with the ethylenediamine; wherein the base is a methanol solution containing 30% sodium methoxide or a sodium hydroxide aqueous solution.

Images