Method for continuously preparing long-chain fatty primary amine by adopting microchannel reactor

Abstract

The invention discloses a method for preparing long-chain fatty primary amine, which comprises the following steps of: conveying halogen, sodium hydroxide and long-chain fatty amide slurry which are mixed and fully reacted at low temperature into a micro-channel reactor, and initiating partial vaporization of a solvent to form gas-liquid Taylor flow through rapid overheating of reaction liquid; after the reaction is finished, rapidly cooling through a cooling section, entering a continuous extractor, carrying out continuous liquid-liquid separation on an effluent mixed solution, and distilling an organic phase to obtain a high-purity long-chain fatty primary amine product. The method can effectively solve the problems of many side reactions, poor selectivity, tedious steps, low production efficiency and the like in the existing kettle type process, significantly improves the yield and selectivity of the target product, reduces the treatment cost of three wastes, and has the advantages of simple operation, efficient reaction, intrinsic safety and the like.

Description

Technical Field

[0001] The invention belongs to the field of microchannel continuous reaction, and particularly relates to a method for continuously preparing long-chain fatty primary amines by using a microchannel reactor. Background Art

[0002] Long-chain fatty primary amines are widely used in organic chemical synthesis such as pesticides, medicines, detergents, and polymers. For example, 1-octylamine can be used as a surfactant and in the synthesis of chemicals such as N-octylpyrrolidone; 1-decylamine can be used as a liquid detergent, foaming agent, and lubricant; 1,8-octanediamine is a comonomer for the synthesis of high-performance polymers and can also be used to prepare the fungicide biguanide trioctylbenzenesulfonate.

[0003] At present, the preparation of long-chain fatty amines is usually obtained by catalytic hydrogenation of the corresponding fatty nitriles under high temperature and high pressure (Chem. Sci., 2018, 9(45), 8553). There are great safety risks in the production process, and the requirements for reaction equipment and hydrogenation catalysts are high. In addition, the product is prone to contain a small amount of impurities with similar boiling points that are difficult to remove.

[0004] The Hofmann rearrangement reaction is an effective method for preparing aromatic or fatty primary amines and is widely used in the synthesis of fine chemicals. The reaction usually involves the reaction of a hypohalite, a base and a primary amide, and through an isocyanate intermediate, a primary amine with one less carbon than the raw material is formed. The reagents used in the above classical Hofmann rearrangement reaction conditions are cheap and are widely used in industry. For short-chain fatty amines (with a carbon number less than 6), they usually have a high yield (>80%). However, in the preparation process of long-chain fatty primary amines (with a carbon number of 7 to 22), due to the strong hydrophobic effect of long-chain alkanes, the intermediate isocyanate is difficult to hydrolyze and is very easy to react with the product amine to form high-boiling impurities such as semicarbazide, resulting in poor selectivity. As the carbon chain increases, the product yield continues to decrease (Chem. Lett. 1984, 13 (5), 713; J. Org. Chem. 1958, 23 (12), 2029). Therefore, the application of the Hofmann rearrangement reaction in the preparation of long-chain fatty primary amines is limited.

[0005] The present invention proposes a new Hofmann rearrangement reaction process for preparing long-chain fatty primary amines based on micro-reaction continuous technology. The process effectively inhibits side reactions, improves production efficiency and reaction yield, and has high industrial application value by means of high-temperature rapid reaction and formation of gas-liquid Taylor flow in microchannels. Summary of the invention

[0006] In view of the shortcomings in the art, the present invention provides a method for preparing long-chain fatty primary amines using micro-reaction continuous technology, aiming to solve a series of problems in the existing production process using the Hofmann rearrangement reaction, such as low production efficiency, serious side reactions and obvious amplification effect, and improve production efficiency and reaction selectivity. The specific technical scheme is as follows:

[0007] A method for continuously preparing long-chain fatty primary amines using a microchannel reactor comprises the following steps:

[0008] (1) adding halogen to a slurry consisting of sodium hydroxide, amide and water in a temperature-controlled reactor with stirring, and obtaining a substantially clear slurry after sufficient reaction as feed liquid A;

[0009] (2) introducing feed liquid A into a microchannel reactor for reaction to obtain reaction liquid B;

[0010] (3) After the reaction liquid B passes through the cooling section, it enters the continuous extractor and is mixed with the extractant;

[0011] (4) The mixed liquid flowing out of the extractor enters a continuous liquid-liquid phase separator, and the obtained organic phase is distilled to obtain the product long-chain fatty primary amine.

[0012] In the present invention, the amide is a product in which one or more H of a long-chain aliphatic hydrocarbon is replaced by -CONH2, and the number of carbon atoms of the long-chain aliphatic hydrocarbon is 7 to 22, and is preferably a long-chain alkane.

[0013] The long-chain fatty primary amine has 7 to 22 carbon atoms, preferably 8 to 11, and 1 to 3 functional amino groups, preferably 1 to 2. The carbon number of the amide is the sum of the carbon number of the long-chain fatty primary amine and the functional amino groups.

[0014] Preferably, the amide may be nonylamide, sebacic acid amide or dodecylamide;

[0015] The long-chain fatty primary amine is n-octylamine, octanediamine or n-undecylamine.

[0016] In step (1), the halogen is one of chlorine gas or liquid bromine; the molar ratio of the acylamino group (-CONH2) contained in the amide to the halogen and sodium hydroxide is 1: (1.0-1.5): (4.0-6.0); and the amount of water used is (10-30) times the mass of the amide.

[0017] In step (1), the temperature inside the temperature-controlled reactor is controlled at (-10 to 10)°C, and the reaction time is 1 to 5 hours.

[0018] In step (1), the solid content of the liquid A is less than 5%.

[0019] In step (2), the characteristic dimension of the channel of the microchannel reactor is 0.5 to 10 mm, preferably 0.5 to 5.0 mm, and more preferably 0.5 to 1.0 mm.

[0020] In step (2), the reaction temperature of the microchannel reactor is 90-180°C, preferably 90-150°C, and more preferably 100-120°C; the reaction pressure is 0.1-1.0 MPa (absolute pressure), preferably 0.1-0.5 MPa, and the reaction pressure is adjusted by a back pressure valve; the residence time of the feed liquid A in the microchannel reactor is 0.5-30 min, preferably 6-18 min, and the flow type is gas-liquid Taylor flow.

[0021] In step (3), the extractant is at least one of a water-insoluble organic solvent such as benzene, toluene, dichloromethane, dichloroethane, n-hexane, cyclohexane, petroleum ether, etc.; and the mass ratio of the extractant to the reaction solution B is 1 to 5:1.

[0022] The concept and technical route of the present invention are: 1. Taking advantage of the high heat and mass transfer efficiency of the microchannel reactor, the reaction liquid is rapidly heated up, and the hydrolysis rate of the intermediate product isocyanate is accelerated; 2. Through high-temperature reaction (90-150°C) under controlled pressure, part of the solvent in the reaction fluid is vaporized, and the reaction fluid is converted into a gas-liquid Taylor flow, so as to cut the front and rear reaction liquids, effectively suppress the back-mixing phenomenon, and reduce the side reaction of isocyanate and the product. 3. Through timely, rapid and continuous extraction, the series side reaction of the product in the aqueous solution after the reaction is completed is effectively reduced.

[0023] On the basis of the above concept and technical route, for the designed micro-reaction continuous system, the present invention further optimizes and controls the corresponding flow rate, reaction temperature, reaction pressure, residence time in the micro-reactor, extractant equivalent, etc. to achieve better reaction efficiency, product yield and selectivity.

[0024] Compared with the prior art, the present invention has the following advantages and outstanding technical effects:

[0025] (1) The introduction of microchannel reactors enables rapid initiation and quenching of reactions, with precise and controllable reaction time, effectively improving reaction selectivity;

[0026] (2) The high mass and heat transfer efficiency of microchannel reactors can avoid runaway reactions caused by violent heat release, and the amplification effect is small.

[0027] (3) The reaction fluid is made to form a gas-liquid Taylor flow under high temperature and pressure control conditions in the microchannel, which effectively suppresses the fluid back-mixing phenomenon in the pipeline and reduces the formation of the main by-product semicarbazide;

[0028] (4) After the reaction is completed, the extractant is used promptly to continuously and quickly extract and separate the phases, thereby reducing the subsequent cascade side reactions of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a process flow chart for continuously preparing long-chain fatty primary amines using a microchannel reactor. Specific implementation methods

[0030] The present invention provides a method for continuously preparing long-chain fatty primary amines by using a microchannel reactor. The present invention is further described below in conjunction with embodiments.

[0031] Example 1

[0032] 30g nonanamide, 900g water and 38g sodium hydroxide were added to a three-necked flask with mechanical stirring in sequence, and the temperature was controlled by a cold trap. 31g bromine was slowly added, and the amide gradually dissolved. The internal temperature was controlled at 5-10°C. After the drop was completed, the temperature was continued to be controlled and stirred for 2 hours. The reaction liquid was basically clear and stored at 0-5°C as feed liquid A. A diaphragm pump was used to pump it into a microchannel reactor (Hastelloy, channel size 0.5mm) at a flow rate of 15g / min. The reaction temperature was 100°C, the reaction pressure was 0.1MPa, and the residence time was 10min. At this time, part of the water in the microchannel was vaporized, and the reaction fluid was a gas-liquid Taylor flow. After the reaction liquid flowing out of the microchannel reactor was cooled to room temperature in the cooling section, it was mixed with toluene in a continuous extractor, and the toluene flow rate was 30g / min. Then the two-phase mixed liquid entered the continuous phase separation device, the organic phase was collected, and then 22g of the product n-octylamine was obtained by distillation. The purity was 99.2% and the reaction yield was 88.9% as measured by gas chromatography.

[0033] Example 2

[0034] 30g nonanamide, 900g water and 38g sodium hydroxide were added to a three-necked flask with mechanical stirring in sequence, and the temperature was controlled by a cold trap. 31g bromine was slowly added, and the amide gradually dissolved. The internal temperature was controlled at 5-10°C. After the drop was completed, the temperature was continued to be controlled and stirred for 2 hours. The reaction liquid was basically clear and stored at 0-5°C as feed liquid A. A diaphragm pump was used to pump it into a microchannel reactor (Hastelloy, channel size 0.5mm) at a flow rate of 15g / min. The reaction temperature was 120°C, the reaction pressure was 0.2MPa, and the residence time was 6min. At this time, part of the water in the microchannel was vaporized, and the reaction fluid was a gas-liquid Taylor flow. After the reaction liquid flowing out of the microchannel reactor was cooled to room temperature in the cooling section, it was mixed with toluene in a continuous extractor, and the toluene flow rate was 30g / min. Then the two-phase mixed liquid entered the continuous phase separation device, the organic phase was collected, and then 23.2g of the product n-octylamine was obtained by distillation. The purity was 99.0% and the reaction yield was 93.5% as measured by gas chromatography.

[0035] Example 3

[0036] 30g nonylamide, 900g water and 38g sodium hydroxide were added to a three-necked flask with mechanical stirring in sequence, and the temperature was controlled by a cold trap. 31g bromine was slowly added, and the amide gradually dissolved. The internal temperature was controlled at 5-10°C. After the drop was completed, the temperature was continued to be controlled and stirred for 2 hours. The reaction solution was basically clear and stored at 0-5°C as feed liquid A. A diaphragm pump was used to pump it into a microchannel reactor (Hastelloy, channel size 0.5mm) at a flow rate of 15g / min. The reaction temperature was 120°C, the reaction pressure was 0.5MPa, and the residence time was 6min. No bubbles were generated in the microchannel at this time. After the reaction liquid flowing out of the microchannel reactor was cooled to room temperature in the cooling section, it was mixed with toluene in a continuous extractor, and the toluene flow rate was 30g / min. Subsequently, the two-phase mixed liquid entered a continuous phase separation device, the organic phase was collected, and then 18.9g of the product n-octylamine was obtained by distillation. The purity was 98.5% and the reaction yield was 75.8% as measured by gas chromatography.

[0037] Example 4

[0038] 38g of sebacic acid amide, 1140g of water and 76g of sodium hydroxide were added to a three-necked flask with mechanical stirring in sequence, and the temperature was controlled by a cold trap. 62g of bromine was slowly added, and the amide gradually dissolved, and the internal temperature was controlled at 5-10°C. After the drop was completed, the temperature was continued to be controlled and stirred for 3 hours. The reaction liquid was basically clear and stored at 0-5°C as feed liquid A. A diaphragm pump was used to pump it into a microchannel reactor (Hastelloy alloy, channel size 0.5mm) at a flow rate of 15g / min, the reaction temperature was 120°C, the reaction pressure was 0.2MPa, and the residence time was 10min. At this time, part of the water in the microchannel was vaporized, and the reaction fluid was a gas-liquid Taylor flow. After the reaction liquid flowing out of the microchannel reactor was cooled to room temperature through a cooling section, it was mixed with toluene in a continuous extractor, and the toluene flow rate was 30g / min. Subsequently, the two-phase mixed liquid entered a continuous phase separation device, the organic phase was collected, and then 25.6g of the product octanediamine was obtained by distillation. The purity was 99.2% and the reaction yield was 92.7% as measured by gas chromatography.

[0039] Example 5

[0040] 38g of dodecylamide, 1140g of water and 38g of sodium hydroxide were added to a three-necked flask with mechanical stirring in sequence, and the temperature was controlled by a cold trap. 31g of bromine was slowly added, and the amide gradually dissolved, and the internal temperature was controlled at 5-10°C. After the drop was completed, the temperature was continued to be controlled and stirred for 2 hours. The reaction liquid was basically clear and stored at 0-5°C as feed liquid A. A diaphragm pump was used to pump it into a microchannel reactor (Hastelloy alloy, channel size 0.5mm) at a flow rate of 15g / min, the reaction temperature was 120°C, the reaction pressure was 0.2MPa, and the residence time was 10min. At this time, part of the water in the microchannel was vaporized, and the reaction fluid was a gas-liquid Taylor flow. After the reaction liquid flowing out of the microchannel reactor was cooled to room temperature through a cooling section, it was mixed with toluene in a continuous extractor, and the toluene flow rate was 30g / min. Subsequently, the two-phase mixed liquid entered a continuous phase separation device, the organic phase was collected, and then 29.3g of the product n-undecylamine was obtained by distillation. The purity was 99.4% and the reaction yield was 89.5% as measured by gas chromatography.

[0041] Example 6

[0042] 30g nonanamide, 900g water and 38g sodium hydroxide were added to a three-necked flask with mechanical stirring in sequence, the temperature was controlled by a cold trap, and about 16g chlorine was slowly introduced, the amide gradually dissolved, and the internal temperature was controlled at 5-10°C. After the drop was completed, the temperature was continued to be controlled and stirred for 2 hours, and the reaction liquid was basically clear, as feed liquid A, and stored at 0-5°C. A diaphragm pump was used to pump it into a microchannel reactor (Hastelloy, channel size 0.5mm) at a flow rate of 15g / min, the reaction temperature was 120°C, the reaction pressure was 0.2MPa, and the residence time was 6min. At this time, part of the water in the microchannel was vaporized, and the reaction fluid was a gas-liquid Taylor flow. After the reaction liquid flowing out of the microchannel reactor was cooled to room temperature through the cooling section, it was mixed with toluene in a continuous extractor, and the toluene flow rate was 30g / min. Then the two-phase mixed liquid entered the continuous phase separation device, the organic phase was collected, and then the product n-octylamine 20.2g was obtained by distillation. The purity was 99.0% and the reaction yield was 81.4% as measured by gas chromatography.

[0043] Example 7

[0044] 30g nonanamide, 900g water and 38g sodium hydroxide were added to a three-necked flask with mechanical stirring in sequence, and the temperature was controlled by a cold trap. 31g bromine was slowly added, and the amide gradually dissolved. The internal temperature was controlled at 5-10°C. After the drop was completed, the temperature was continued to be controlled and stirred for 2 hours. The reaction liquid was basically clear and stored at 0-5°C as feed liquid A. A diaphragm pump was used to pump it into a microchannel reactor (Hastelloy, channel size 0.5mm) at a flow rate of 5g / min. The reaction temperature was 120°C, the reaction pressure was 0.2MPa, and the residence time was 18min. At this time, part of the water in the microchannel was vaporized, and the reaction fluid was a gas-liquid Taylor flow. After the reaction liquid flowing out of the microchannel reactor was cooled to room temperature in the cooling section, it was mixed with toluene in a continuous extractor, and the toluene flow rate was 10g / min. Then the two-phase mixed liquid entered the continuous phase separation device, the organic phase was collected, and then the product n-octylamine 21.1g was obtained by distillation. The purity was 99.0% and the reaction yield was 85.1% as measured by gas chromatography.

[0045] Comparative Example 1

[0046] Add 30g nonanamide, 900g water and 38g sodium hydroxide to a three-necked flask with mechanical stirring in sequence, control the temperature with a cold trap, slowly add 31g bromine, the amide gradually dissolves, and control the internal temperature at 5-10°C. After the addition, continue to control the temperature and stir for 2 hours, and the reaction liquid is basically clear. Put the three-necked flask in a 50°C water bath, keep warm and stir for 30 minutes, at this time the reaction liquid is completely clear, then increase the water bath temperature to 80°C, continue to keep warm and stir for 1h, and stop the reaction. Cool to room temperature, extract with 2000g toluene in three batches, combine the organic phases for rectification, and obtain 15.2g of product n-octylamine. The purity is 98.7% as measured by gas chromatography, and the reaction yield is 61.2%.

[0047] Comparative Example 2

[0048] Add 30g nonanamide, 900g water and 38g sodium hydroxide to a three-necked flask with mechanical stirring in sequence, control the temperature with a cold trap, slowly add 31g bromine, the amide gradually dissolves, and control the internal temperature at 5-10°C. After the addition, continue to control the temperature and stir for 2 hours, and the reaction liquid is basically clear. Install a condenser reflux tube, put the three-necked flask into a 120°C oil bath, stir at normal pressure for 60 minutes, and stop the reaction. Cool to room temperature, extract with 2000g toluene in three batches, combine the organic phases for distillation, and obtain 12.7g of product n-octylamine. The purity is 96.7% as measured by gas chromatography, and the reaction yield is 50.2%.

Claims

1. A method for continuously preparing long-chain fatty primary amines using a microchannel reactor, characterized in that: The following steps are involved: (1) adding halogen to a slurry consisting of sodium hydroxide, amide and water in a temperature-controlled reactor with stirring, and obtaining a feed liquid A after sufficient reaction; (2) introducing feed liquid A into a microchannel reactor for reaction to obtain reaction liquid B; (3) After the reaction liquid B passes through the cooling section, it enters the continuous extractor and is mixed with the extractant; (4) The mixed liquid flowing out of the extractor enters a continuous liquid-liquid phase separator, and the obtained organic phase is distilled to obtain the product long-chain fatty primary amine.

2. The method according to claim 1, characterized in that The long-chain fatty primary amine contains 7 to 22 carbon atoms and 1 to 3 functional amino groups.

3. The method according to claim 1, characterized in that The amide is nonylamide, sebacic acid amide or dodecylamide; The long-chain fatty primary amine is n-octylamine, octanediamine or n-undecylamine.

4. The method according to claim 1, characterized in that In step (1), the halogen is one of chlorine gas or liquid bromine; the molar ratio of the acylamino group contained in the amide to the halogen and sodium hydroxide is 1:(1.0-1.5):(4.0-6.0); and the amount of water used is (10-30) times the mass of the amide.

5. The method according to claim 1, characterized in that In step (1), the temperature inside the temperature-controlled reactor is controlled at (-10 to 10)°C, and the reaction time is 1 to 5 hours.

6. The method according to claim 1, characterized in that In step (1), the solid content of the liquid A is less than 5%.

7. The method according to claim 1, characterized in that In step (2), the characteristic dimension of the channel of the microchannel reactor is 0.5 to 10 mm.

8. The method according to claim 1, characterized in that In step (2), the reaction temperature of the microchannel reactor is 90-180° C., and the reaction pressure is 0.1-1.0 MPa (absolute pressure); the residence time of the feed liquid A in the microchannel reactor is 0.5-30 min, and the flow type is gas-liquid Taylor flow.

9. The method according to claim 1, characterized in that In step (3), the extractant is a water-insoluble organic solvent, preferably at least one of benzene, toluene, dichloromethane, dichloroethane, n-hexane, cyclohexane, and petroleum ether; and the mass ratio of the extractant to the reaction solution B is 1 to 5:1.

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