CN116621712A - Continuous nitration preparation method of 2-amino-4-nitrotoluene microreactor - Google Patents
Continuous nitration preparation method of 2-amino-4-nitrotoluene microreactor Download PDFInfo
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- 238000006396 nitration reaction Methods 0.000 title claims abstract description 29
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- DSBIJCMXAIKKKI-UHFFFAOYSA-N 5-nitro-o-toluidine Chemical compound CC1=CC=C([N+]([O-])=O)C=C1N DSBIJCMXAIKKKI-UHFFFAOYSA-N 0.000 title claims abstract description 19
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 49
- 238000006243 chemical reaction Methods 0.000 claims abstract description 42
- RNVCVTLRINQCPJ-UHFFFAOYSA-N o-toluidine Chemical compound CC1=CC=CC=C1N RNVCVTLRINQCPJ-UHFFFAOYSA-N 0.000 claims abstract description 40
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 37
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 29
- 239000002253 acid Substances 0.000 claims abstract description 28
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 21
- 239000000463 material Substances 0.000 claims abstract description 17
- RNWVKJZITPOKMO-UHFFFAOYSA-N 2-methylaniline;sulfuric acid Chemical compound OS(O)(=O)=O.CC1=CC=CC=C1N RNWVKJZITPOKMO-UHFFFAOYSA-N 0.000 claims abstract description 15
- 238000001914 filtration Methods 0.000 claims abstract description 14
- 238000001556 precipitation Methods 0.000 claims abstract description 11
- 238000006386 neutralization reaction Methods 0.000 claims abstract description 9
- 238000002347 injection Methods 0.000 claims abstract description 8
- 239000007924 injection Substances 0.000 claims abstract description 8
- 230000003472 neutralizing effect Effects 0.000 claims abstract description 8
- 230000001546 nitrifying effect Effects 0.000 claims abstract description 8
- 239000007787 solid Substances 0.000 claims abstract description 5
- 239000003513 alkali Substances 0.000 claims abstract description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 14
- 239000007789 gas Substances 0.000 claims description 12
- 239000007788 liquid Substances 0.000 claims description 12
- 150000003839 salts Chemical class 0.000 claims description 10
- 230000015572 biosynthetic process Effects 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 6
- 239000003570 air Substances 0.000 claims description 3
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 239000001569 carbon dioxide Substances 0.000 claims description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 abstract description 3
- 238000000926 separation method Methods 0.000 abstract description 2
- 230000007935 neutral effect Effects 0.000 abstract 1
- 239000000047 product Substances 0.000 description 22
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 12
- 230000001276 controlling effect Effects 0.000 description 10
- 238000003756 stirring Methods 0.000 description 10
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 9
- WFDIJRYMOXRFFG-UHFFFAOYSA-N Acetic anhydride Chemical compound CC(=O)OC(C)=O WFDIJRYMOXRFFG-UHFFFAOYSA-N 0.000 description 9
- 238000004519 manufacturing process Methods 0.000 description 6
- 229910000029 sodium carbonate Inorganic materials 0.000 description 6
- 238000000034 method Methods 0.000 description 5
- 229960000583 acetic acid Drugs 0.000 description 4
- 239000002585 base Substances 0.000 description 4
- 239000003153 chemical reaction reagent Substances 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- 239000011521 glass Substances 0.000 description 4
- 230000002035 prolonged effect Effects 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 239000012362 glacial acetic acid Substances 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 239000011344 liquid material Substances 0.000 description 3
- ODUCDPQEXGNKDN-UHFFFAOYSA-N nitroxyl Chemical compound O=N ODUCDPQEXGNKDN-UHFFFAOYSA-N 0.000 description 3
- 238000007086 side reaction Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000036632 reaction speed Effects 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- FFRBMBIXVSCUFS-UHFFFAOYSA-N 2,4-dinitro-1-naphthol Chemical compound C1=CC=C2C(O)=C([N+]([O-])=O)C=C([N+]([O-])=O)C2=C1 FFRBMBIXVSCUFS-UHFFFAOYSA-N 0.000 description 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- 229920006052 Chinlon® Polymers 0.000 description 1
- 229920000297 Rayon Polymers 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- GPFIZJURHXINSQ-UHFFFAOYSA-N acetic acid;nitric acid Chemical compound CC(O)=O.O[N+]([O-])=O GPFIZJURHXINSQ-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000000987 azo dye Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 238000004043 dyeing Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 239000012065 filter cake Substances 0.000 description 1
- 239000012847 fine chemical Substances 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 230000005802 health problem Effects 0.000 description 1
- 239000005457 ice water Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000012860 organic pigment Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
- C07C209/68—Preparation of compounds containing amino groups bound to a carbon skeleton from amines, by reactions not involving amino groups, e.g. reduction of unsaturated amines, aromatisation, or substitution of the carbon skeleton
- C07C209/76—Preparation of compounds containing amino groups bound to a carbon skeleton from amines, by reactions not involving amino groups, e.g. reduction of unsaturated amines, aromatisation, or substitution of the carbon skeleton by nitration
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
- C07C209/68—Preparation of compounds containing amino groups bound to a carbon skeleton from amines, by reactions not involving amino groups, e.g. reduction of unsaturated amines, aromatisation, or substitution of the carbon skeleton
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention discloses a continuous nitration preparation method of a 2-amino-4-nitrotoluene microreactor, which comprises the following steps of: dripping o-toluidine into concentrated sulfuric acid, adding water, controlling the temperature to be 0-35 ℃ and reacting to obtain o-toluidine sulfate; preparing mixed acid: adding 98% concentrated sulfuric acid into 50-75% industrial nitric acid in batches, and controlling the temperature to be 0-35 ℃; nitrifying: respectively controlling the o-toluidine sulfate and mixed acid to enter a micro-channel reactor through a sample injection pump, and simultaneously introducing gas, wherein the nitration temperature is controlled to be 0-35 ℃, and the total residence time is 0.5-10 min; treating the tail end of the micro-channel with water to precipitate solids, and filtering to obtain water precipitation material; and (3) neutralization: adding the water separation material into water, neutralizing to be neutral by alkali, and filtering to obtain a product; the invention uses 50-75% nitric acid to replace fuming nitric acid, shortens the reaction time and reduces the dangerous coefficient of the reaction while ensuring the conversion rate; the size of the micro-channel reactor is changed, and the productivity can be improved at the same time.
Description
Technical Field
The invention particularly relates to a continuous nitration preparation method of a 2-amino-4-nitrotoluene microreactor.
Background
2-amino-4-nitrotoluene (scarlet group G) is a golden yellow crystalline solid, belongs to an important composition of insoluble azo dyes, is mainly used for dyeing silk, viscose and chinlon fabrics, and can be used as an organic pigment intermediate. At present, the preparation method mainly adopts o-toluidine as a raw material, and the product is obtained through sulfuric acid salification, mixed acid nitration, sodium carbonate neutralization and centrifugal separation.
The traditional intermittent production method uses o-toluidine as raw material, uses 98% sulfuric acid and a small amount of waste sulfuric acid with concentration higher than 50% to form salt, uses 98% concentrated sulfuric acid and 98% fuming nitric acid to prepare mixed acid as nitration reagent, makes nitration reaction at-5-0 ℃, then uses liquid ammonia (or sodium carbonate) to neutralize, and then makes centrifugal filtration to obtain the product (CN 106278908A). The traditional method has the problems of long reaction time, high risk coefficient, poor selectivity, environmental pollution and the like.
The micro-reaction continuous flow technology can realize intrinsic safety and is gradually used in the field of fine chemical product production due to high mass and heat transfer efficiency, easily controlled temperature, less side reaction and low liquid holdup. In the currently applied patent, the preparation of the scarlet base G by utilizing the micro-reaction continuous flow technology has two technical routes: firstly, acetic anhydride or glacial acetic acid is used for salifying with o-toluidine, acetate is obtained through distillation and concentration, then nitration reaction is carried out on acetic anhydride or glacial acetic acid and o-toluidine and acetic acid-nitric acid mixed acid (acetic acid and nitric acid mixture) in a micro-channel, obtained nitration liquid is dissolved in ice water, crystallized and filtered, and finally, a filter cake is acidified, dissolved, crystallized and filtered again to obtain products (CN 114478262A and CN 109942434A). The technical route has complex procedures, long reaction period and high cost, and the used acetic anhydride or glacial acetic acid can cause workshop occupational health problems due to pungent smell. The second technical route is to change the nitration reaction in a batch reactor in the conventional production method into a continuous flow reaction in a microchannel (CN 113121360 a).
The traditional intermittent production realizes mixed mass transfer by stirring with stirring paddles, and has low mass transfer coefficient and poor mixing effect; in order to improve the reaction efficiency, 98% concentrated sulfuric acid and 98% fuming nitric acid are used for preparing mixed acid as a nitrifying reagent so as to maintain higher concentration of nitroxyl positive ions, thereby improving the reaction speed. Meanwhile, the reaction is a strong exothermic reaction, and for safety, the feed liquid in the kettle must be maintained at a low temperature of-5 ℃ so as to remove the reaction heat, but the lower system temperature increases the viscosity of a sulfuric acid system, weakens the mass transfer dispersion effect, and further reduces the reaction speed, so that the reaction time is up to 6-8 hours, and the whole process is low-efficiency and has the safety risk of losing temperature.
The prior art CN113121360A discloses a preparation method of a scarlet base G, which comprises the steps of reacting o-toluidine with sulfuric acid to obtain a first product, respectively conveying fuming nitric acid to a micro-channel reactor to react to obtain a second product, and reacting with sodium carbonate to neutrality to obtain the scarlet base G. The 98% fuming nitric acid is adopted as the nitrifying reagent, the concentration of nitroxyl positive ions is high, and the high specific area provided by the microchannel reactor is added, so that the reaction is completed in a very short time, the problem of hot spot concentration is very easy to cause, a strong heat exchange system is required to remove heat in time, and the energy consumption is huge; meanwhile, the hot spot concentration also causes side reactions to increase and the selectivity to be poor; in addition, the transient reaction is completed at the front end of the micro-channel, so that the rear end of the micro-channel reactor cannot function, and equipment waste is caused. In addition, the currently used micro-channel has smaller pipe diameter, the general inner diameter is 300-1000 um, and the productivity is limited.
The diameter of the pipeline is inversely proportional to the heat exchange coefficient and the specific surface area of the system, and if the pipe diameter is increased to improve the productivity, the specific surface area and the heat exchange coefficient are reduced. This can lead to two consequences: firstly, the mixing efficiency of the liquid-liquid heterogeneous reaction is greatly reduced, the reaction selectivity is also reduced, the byproducts are increased, and the yield is reduced. Secondly, the concentration of nitroxyl positive ions in a system taking 98% fuming nitric acid as a nitrifying reagent is high, the reaction rate is high, if the pipe diameter is increased for improving the productivity, the raw material input quantity is increased, the problem of accumulation of pipeline heat caused by hot spot concentration is necessarily solved, and higher requirements are put on a heat exchange system, otherwise, the heat loss can occur, so that potential safety hazard is brought. If for safety reasonsThe concentration of nitric acid is reduced, which tends to cause NO 2+ The concentration is reduced, the conversion rate is low, the reaction is incomplete, and the yield is affected. If the conversion rate is to be increased, the reaction residence time is greatly prolonged, so that the equipment cost is greatly increased, and the production efficiency is reduced due to the prolonged residence time.
When the micro-channel reactor is used for preparing 2-amino-4-nitrotoluene (scarlet base G), how to reduce the concentration of nitric acid to increase the safety and simultaneously consider the conversion rate and the production efficiency is a technical problem to be solved urgently.
Disclosure of Invention
The invention aims to provide a continuous nitration preparation method of a 2-amino-4-nitrotoluene microreactor, which adopts 50-75% industrial nitric acid to replace 98% fuming nitric acid, so that the retention time is not prolonged, the conversion rate is ensured, and the danger coefficient of the reaction is reduced.
In order to achieve the above purpose, the following technical scheme is adopted:
the continuous nitration preparation method of the 2-amino-4-nitrotoluene microreactor comprises the following steps:
(1) Salt formation: dripping o-toluidine into concentrated sulfuric acid, adding water, controlling the temperature to be 0-35 ℃ and reacting to obtain o-toluidine sulfate;
(2) Preparing mixed acid: adding 98% concentrated sulfuric acid into 50-75% industrial nitric acid in batches, and controlling the temperature to be 0-35 ℃;
(3) Nitrifying: respectively controlling the o-toluidine sulfate and mixed acid to enter a micro-channel reactor through a sample injection pump, and simultaneously introducing gas, wherein the nitration temperature is controlled to be 0-35 ℃, and the total residence time is 0.5-10 min; treating the tail end of the micro-channel with water to precipitate solids, and filtering to obtain water precipitation material;
(4) And (3) neutralization: adding the water precipitation material into water, neutralizing with alkali to neutrality, and filtering to obtain the product.
According to the scheme, the molar ratio of the concentrated sulfuric acid to the o-toluidine in the step (1) is (4-10): 1.
According to the scheme, the molar ratio of the concentrated sulfuric acid to the water in the step (1) is (4-10): 1.
According to the scheme, the molar ratio of 98% concentrated sulfuric acid to 50-75% nitric acid in the step (2) is (0.3-1.0): 1.
According to the scheme, in the step (3), the o-toluidine sulfate and the mixed acid are mixed according to the volume ratio of (5-7): 1 into the microchannel reactor.
According to the above scheme, the gas in the step (3) comprises any one of air, carbon dioxide, nitrogen and argon.
According to the scheme, the gas is introduced into the step (3) to control the gas-liquid volume ratio (10-1000) in the reaction system to be 1.
According to the scheme, the inner diameter range of the micro-channel reactor in the step (3) is 0.3-4 mm.
The synthetic route of the chemical reaction of the invention is as follows:
compared with the prior art, the invention has the following beneficial effects:
(1) 50-75% of nitric acid is used for replacing 98% of fuming nitric acid in the traditional process, so that the raw material cost is reduced.
(2) The reaction is mild and controllable, and the side reaction is reduced.
(3) The system temperature is raised to more than 10 ℃ from about-5 ℃ in the traditional process, so that the energy consumption is reduced.
(4) The safety of the reaction is greatly improved while the residence time is not prolonged and the conversion rate is ensured.
(5) The system adopts a micro-channel with the inner diameter ranging from 0.3 to 4mm, and compared with the traditional micro-reactor, the flux is enlarged, and the productivity is improved by one order of magnitude.
Drawings
Fig. 1: typical preparation process flow diagrams of the 2-amino-4-nitrotoluene are shown in the specification.
Fig. 2: liquid chromatogram of the product of example 1.
Detailed Description
The following examples further illustrate the technical aspects of the present invention, but are not intended to limit the scope of the present invention.
The specific embodiment provides a continuous nitration preparation method of a 2-amino-4-nitrotoluene microreactor, which comprises the following steps:
(1) Salt formation: dripping o-toluidine into concentrated sulfuric acid, adding water, controlling the temperature to be 0-35 ℃ and reacting to obtain o-toluidine sulfate;
(2) Preparing mixed acid: adding 98% concentrated sulfuric acid into 50-75% industrial nitric acid in batches, and controlling the temperature to be 0-35 ℃;
(3) Nitrifying: respectively controlling the o-toluidine sulfate and mixed acid to enter a micro-channel reactor through a sample injection pump, and simultaneously introducing gas, wherein the nitration temperature is controlled to be 0-35 ℃, and the total residence time is 0.5-10 min; treating the tail end of the micro-channel with water to precipitate solids, and filtering to obtain water precipitation material;
(4) And (3) neutralization: adding the water precipitation material into water, neutralizing with alkali to neutrality, and filtering to obtain the product.
Specifically, the molar ratio of the concentrated sulfuric acid to the o-toluidine in the step (1) is (4-10): 1. The molar ratio of the concentrated sulfuric acid to the water is (4-10): 1.
Specifically, the molar ratio of 98% concentrated sulfuric acid to 50-75% nitric acid in the step (2) is (0.3-1.0): 1.
Specifically, in the step (3), the o-toluidine sulfate and the mixed acid are mixed according to the volume ratio of (5-7): 1 into the microchannel reactor. The gas comprises any one of air, carbon dioxide, nitrogen and argon. The gas is introduced to control the gas-liquid volume ratio (10-1000) in the reaction system to be 1.
Specifically, the micro-channel inner diameter range of the micro-channel reactor in the step (3) is 0.3-4 mm.
A typical preparation process flow diagram of the 2-amino-4-nitrotoluene is shown in the accompanying figure 1, a A, B storage tank is respectively provided with salt forming materials and mixed acid, and two materials are respectively conveyed to a reactor through two pumps; the gas is regulated to set flow rate through a gas flowmeter and then enters a salt forming pipeline. The temperature and pressure of the whole system are monitored by a built-in temperature and pressure sensor. The two materials enter the micro-channel reactor at the T-shaped tee joint to carry out nitration reaction. Introducing the tail end material of the reaction tube into water, filtering, and sampling for liquid phase analysis and detection.
Example 1
(1) Salt formation: adding 98% concentrated sulfuric acid into a three-mouth glass bottle with stirring according to the molar ratio of the concentrated sulfuric acid to the o-toluidine of 5:1, controlling the temperature in the bottle at 25 ℃, and dripping the o-toluidine into the three-mouth bottle for about 1 h. Then adding water according to the molar ratio of concentrated sulfuric acid to water of 4:1, stirring for 5min, and discharging.
(2) Preparing mixed acid: the concentrated sulfuric acid was added to the nitric acid in portions in a molar ratio of 98% concentrated sulfuric acid to 68% nitric acid of 0.6:1, the temperature being controlled at 20 ℃.
(3) Nitration reaction: according to the volume ratio of the o-methylaniline sulfate to the mixed acid of 5:1, the mixed acid is input into a micro-channel system through a sample injection pump, and the nitrogen amount is 200 times of the total volume of the liquid. The gas-liquid materials are converged by a tee joint and then enter a reaction tube, wherein the inner diameter of the reaction tube is 1mm, the wall thickness is 0.5mm, and the length is 10m. The temperature was set at 10 ℃. The reaction residence time was 1min.
(4) And (3) neutralization: and (3) dripping the prepared sodium carbonate solution (the mass concentration is 30%) into a water precipitation material, neutralizing to pH=7, and filtering to obtain a product. The product yield was 85.7%, the product purity was 98.26% and the space-time yield was: 8kg/cm 3 H. The liquid chromatogram of the product obtained in this example is shown in FIG. 2.
Example 2
(1) Salt formation: adding 98% concentrated sulfuric acid into a three-mouth glass bottle with stirring according to the molar ratio of the concentrated sulfuric acid to the o-toluidine of 4:1, controlling the temperature in the bottle at 25 ℃, and dripping the o-toluidine into the three-mouth bottle for about 1 h. Then adding water according to the molar ratio of the concentrated sulfuric acid to the water of 6:1, stirring for 5min, and discharging.
(2) Preparing mixed acid: the concentrated sulfuric acid was added to the nitric acid in portions in a molar ratio of 98% concentrated sulfuric acid to 60% nitric acid of 0.5:1, the temperature being controlled at 20 ℃.
(3) Nitration reaction: according to the volume ratio of the o-methylaniline sulfate to the mixed acid of 6:1, the mixed acid is input into a micro-channel system through a sample injection pump, and the nitrogen amount is 100 times of the total volume of the liquid. The gas-liquid materials are converged by a tee joint and then enter a reaction tube, wherein the inner diameter of the reaction tube is 3mm, the wall thickness is 0.5mm, and the length is 15m. The temperature was set at 20℃and the reaction residence time was 2min.
(4) And (3) neutralization: will beAnd (3) dripping the prepared pure alkaline water (the mass concentration is 30%) into a water precipitation material, neutralizing to pH=7, and filtering to obtain a product. The product yield was 82.6%, the product purity was 98.13% and the space-time yield was: 11kg/cm 3 .h
Example 3
(1) Salt formation: adding 98% concentrated sulfuric acid into a three-mouth glass bottle with stirring according to the molar ratio of the concentrated sulfuric acid to the o-toluidine of 6:1, controlling the temperature in the bottle at 25 ℃, and dripping the o-toluidine into the three-mouth bottle for about 1 h. Then adding water according to the molar ratio of concentrated sulfuric acid to water of 5:1, stirring for 5min, and discharging.
(2) Preparing mixed acid: the concentrated sulfuric acid was added to the nitric acid in portions in a molar ratio of 98% concentrated sulfuric acid to 55% nitric acid of 0.5:1, the temperature being controlled at 20 ℃.
(3) Nitration reaction: according to the volume ratio of the o-methylaniline sulfate to the mixed acid of 7:1, the mixed acid is input into a micro-channel system through a sample injection pump, and the nitrogen amount is 100 times of the total volume of the liquid. The gas-liquid materials are converged by a tee joint and then enter a reaction tube, wherein the inner diameter of the reaction tube is 3mm, the wall thickness is 0.5mm, and the length is 15m. The temperature was set at 20℃and the reaction residence time was 2min.
(4) And (3) neutralization: and (3) dripping the prepared sodium carbonate solution (the mass concentration is 30%) into a water precipitation material, neutralizing to pH=7, and filtering to obtain a product. The product yield was 78.6%, the product purity was 97.6% and the space-time yield was: 9kg/cm 3 .h
Comparative example 1
Example 1 was repeated, but without the introduction of gas, the specific operation was as follows.
(1) Salt formation: adding 98% concentrated sulfuric acid into a three-mouth glass bottle with stirring according to the molar ratio of the concentrated sulfuric acid to the o-toluidine of 5:1, controlling the temperature in the bottle at 25 ℃, and dripping the o-toluidine into the three-mouth bottle for about 1 h. Then adding water according to the molar ratio of concentrated sulfuric acid to water of 4:1, stirring for 5min, and discharging.
(2) Preparing mixed acid: the concentrated sulfuric acid was added to the nitric acid in portions in a molar ratio of 98% concentrated sulfuric acid to 68% nitric acid of 0.6:1, the temperature being controlled at 20 ℃.
(3) Nitration reaction: according to the volume ratio of the o-methylaniline sulfate to the mixed acid of 5:1, the mixed acid is input into a micro-channel system through a sample injection pump, and nitrogen is not introduced into the system. The materials are converged by the tee joint and then enter the reaction tube, wherein the inner diameter of the reaction tube is 1mm, the wall thickness is 0.5mm, and the length is 10m. The temperature was set at 10 ℃. The reaction residence time was 1min.
(4) And (3) neutralization: and (3) dripping the prepared sodium carbonate solution (the mass concentration is 30%) into a water precipitation material, neutralizing to pH=7, and filtering to obtain a product. The product yield was 58.7%, the product purity was 86.36% and the space-time yield was: 6kg/cm 3 .h。
Claims (8)
- The continuous nitration preparation method of the 2-amino-4-nitrotoluene microreactor is characterized by comprising the following steps of:(1) Salt formation: dripping o-toluidine into concentrated sulfuric acid, adding water, controlling the temperature to be 0-35 ℃ and reacting to obtain o-toluidine sulfate;(2) Preparing mixed acid: adding 98% concentrated sulfuric acid into 50-75% industrial nitric acid in batches, and controlling the temperature to be 0-35 ℃;(3) Nitrifying: respectively controlling the o-toluidine sulfate and mixed acid to enter a micro-channel reactor through a sample injection pump, and simultaneously introducing gas, wherein the nitration temperature is controlled to be 0-35 ℃, and the total residence time is 0.5-10 min; treating the tail end of the micro-channel with water to precipitate solids, and filtering to obtain water precipitation material;(4) And (3) neutralization: adding the water precipitation material into water, neutralizing with alkali to neutrality, and filtering to obtain the product.
- 2. The continuous nitration preparation method of 2-amino-4-nitrotoluene microreactor according to claim 1, wherein in the step (1), the molar ratio of concentrated sulfuric acid to o-toluidine is (4-10): 1.
- 3. The continuous nitration preparation process of 2-amino-4-nitrotoluene microreactor according to claim 1, wherein in step (1) the molar ratio of concentrated sulfuric acid to water is (4-10): 1.
- 4. The continuous nitration preparation method of 2-amino-4-nitrotoluene microreactor according to claim 1, wherein in the step (2), the molar ratio of 98% concentrated sulfuric acid to 50-75% nitric acid is (0.3-1.0): 1.
- 5. The continuous nitration preparation method of 2-amino-4-nitrotoluene microreactor of claim 1, wherein in step (3), o-toluidine sulfate and mixed acid are mixed according to a volume ratio of (5-7): 1 into the microchannel reactor.
- 6. The continuous nitrifying preparation method of 2-amino-4-nitrotoluene microreactor according to claim 1, characterized in that said gas in step (3) comprises any one of air, carbon dioxide, nitrogen and argon.
- 7. The continuous nitration preparation method of 2-amino-4-nitrotoluene microreactor of claim 1, wherein the gas is introduced into the reaction system in step (3) to control the gas-liquid volume ratio (10-1000): 1.
- 8. The continuous nitration preparation method of 2-amino-4-nitrotoluene microreactor according to claim 1, wherein the microchannel reactor in step (3) has an inner diameter of the microchannel in the range of 0.3 to 4mm.
Priority Applications (1)
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