Green nitration device and nitration process

Abstract

According to the green nitration device and the nitration process, methyl benzoic acid and nitric acid are subjected to nitration reaction in a methyl benzoic acid nitration reaction unit, and obtained first nitration reaction liquid is separated by a first solid-liquid separator to obtain a first product and a first liquid phase; the first liquid phase is diluted and crystallized by water and then is separated in a second solid-liquid separator to obtain a first product and a second liquid phase, and the second liquid phase temporarily stored in a temporary storage tank and a substituted aniline solution enter a substituted aniline nitration reaction unit to be subjected to nitration reaction; and refining the obtained second nitration reaction liquid through a first oil-water separator and a product refining and separating unit to obtain a second product nitro-substituted aniline. According to the method, the waste nitric acid obtained after nitration reaction of methyl benzoic acid is directly used for nitration reaction of substituted aniline without refining and impurity removal treatment, comprehensive utilization of the waste nitric acid is achieved, links such as salification of substituted aniline are avoided, the process is simple, resource waste is reduced, potential safety hazards are reduced, and green production is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and in particular relates to a green nitrification device and a nitrification process. Background Art

[0002] The nitration product of methyl benzoic acid (referred to as substituted benzoic acid) is an important intermediate for fine chemicals such as medicines. During the production process, methyl benzoic acid is generally nitrated with excess nitric acid, thereby generating a large amount of waste nitric acid. The method for treating waste nitric acid in the prior art is usually to concentrate the waste nitric acid and then apply it to the nitration reaction. This method has high production costs and potential safety hazards.

[0003] N-(1-ethylpropyl)-2,6-dinitro-3,4-dimethylaniline (referred to as nitro-substituted aniline) belongs to the dinitroaniline herbicide and is a selective soil-sealing herbicide widely used in cotton, corn, rice, potato, soybean, peanut and tobacco. The existing process uses N-(1-ethylpropyl)-3,4-dimethylaniline (referred to as substituted aniline) as a raw material, first reacts with dilute acid to form a salt and then reacts with concentrated acid to nitrate to prepare nitro-substituted aniline, and the production cost is high.

[0004] Therefore, it is urgent to develop a nitration device and a nitration process that can reuse the waste acid of substituted benzoic acid in the preparation of nitro-substituted aniline, which can not only improve the utilization rate of nitric acid and reduce production costs, but also simplify the preparation process of nitro-substituted aniline, thereby fundamentally achieving green environmental protection. Summary of the invention

[0005] The purpose of the present invention is to provide a green nitration device and a nitration process. The nitration process of the present invention has high nitric acid utilization rate, low equipment investment, high safety and is green and environmentally friendly.

[0006] The present invention provides a green nitration device, comprising: a methyl benzoic acid nitration reaction unit, a first solid-liquid separator, a crystallization kettle, a second solid-liquid separator, a temporary storage tank, a liquid feed pump, a substituted aniline nitration reaction unit, a first oil-water separator and a product refining and separation unit;

[0007] The discharge port of the methyl benzoic acid nitration reaction unit is connected to the feed port of the first solid-liquid separator, the first liquid phase outlet of the first solid-liquid separator is connected to the feed port of the crystallization kettle, the discharge port of the crystallization kettle is connected to the feed port of the second solid-liquid separator, the second liquid phase outlet of the second solid-liquid separator is connected to the feed port of the temporary storage tank, the discharge port of the temporary storage tank is connected to the acid inlet of the substituted aniline nitration reaction unit through a liquid feed pump, the discharge port of the substituted aniline nitration reaction unit is connected to the feed port of the first oil-water separator, and the oil outlet of the first oil-water separator is connected to the feed port of the product refining and separation unit;

[0008] The methyl benzoic acid nitration reaction unit is provided with a methyl benzoic acid inlet and a nitric acid inlet, the crystallization kettle is also provided with a water inlet, and the substituted aniline nitration reaction unit is also provided with a substituted aniline solution inlet.

[0009] Preferably, the nitrification device further comprises an alkali adjustment unit, the oil outlet of the first oil-water separator is connected to the feed inlet of the alkali adjustment unit, and the oil outlet of the alkali adjustment unit is connected to the feed inlet of the product refining and separation unit.

[0010] Preferably, the alkali adjustment unit is a alkali adjustment kettle and a second oil-water separator connected in sequence.

[0011] Preferably, the nitration device further comprises an acid adjustment unit, the water outlet of the alkali adjustment unit is connected to the feed inlet of the acid adjustment unit, and the acid adjustment unit comprises an acid adjustment kettle and a third solid-liquid separator connected in sequence.

[0012] Preferably, the product refining and separation unit comprises a substitution reaction unit, a separation unit, a distillation kettle, and a dryer; the separation unit is an oil-water separator and a two-stage washing and separation two-in-one device connected in sequence, or a solid-liquid separator, an oil-water separator and a two-stage washing and separation two-in-one device connected in sequence, or an oil-water separator and a three-stage washing and separation two-in-one device connected in sequence, or a solid-liquid separator, an oil-water separator and a three-stage washing and separation two-in-one device connected in sequence.

[0013] The present invention provides a green nitration process, using the nitration device described above, comprising the following steps:

[0014] S1: methyl benzoic acid and nitric acid enter into a methyl benzoic acid nitration reaction unit to undergo a nitration reaction to obtain a first nitration reaction liquid;

[0015] S2: The first nitration reaction liquid enters the first solid-liquid separator for separation to obtain a first product and a first liquid phase;

[0016] S3: The first liquid phase enters the crystallization kettle, is diluted with water and crystallized, and then transferred to the second solid-liquid separator. After separation in the second solid-liquid separator, the first product and the second liquid phase are obtained. The second liquid phase enters the temporary storage tank through a pipeline for temporary storage;

[0017] S4: the substituted aniline solution and the second liquid phase enter the substituted aniline nitration reaction unit to undergo nitration reaction to obtain a second nitration reaction solution;

[0018] S5: The second nitration reaction liquid enters the first oil-water separator for oil-water separation, and the separated oil phase enters the product refining and separation unit for refining operation to obtain the second product nitro-substituted aniline.

[0019] Preferably, the concentration of nitric acid in step S1 is 85-98%, the molar ratio of methyl benzoic acid to nitric acid is 1:(5-10), the reaction temperature is -30-0°C, and the reaction time is 1-30 min. The concentration of nitric acid in the second liquid phase in step S3 is 40-70%, the reaction temperature in step S4 is 60-80°C, the pressure is 0.1-0.3 MPa, and the reaction time is 10-300 s. The substituted aniline solution is a mixed solution of substituted aniline and dichloroethane in a mass ratio of 1:(1-3), and the mass ratio of substituted aniline to the second liquid phase is 1:(2-4).

[0020] Preferably, the oil phase separated by the first oil-water separator in step S5 first enters the alkali adjustment unit before entering the product refining and separation unit, and is mixed with alkali solution to adjust the pH to 8-14. After mixing for 1-3 hours, the oil phase and the water phase are separated, and the separated oil phase enters the product refining and separation unit for separation to obtain the product nitro-substituted aniline.

[0021] Preferably, the aqueous phase separated by the alkali adjustment unit enters the acid adjustment unit, is mixed with dilute acid to adjust the pH to 0-3, and after mixing for 1-3 hours, the solid phase and the liquid phase are separated, and the separated solid phase is combined with the first product separated in step S2 and step S3 to form the first product.

[0022] Preferably, the refining operation in step S5 is to mix the oil phase separated by the first oil-water separator with hydrochloric acid and aminosulfonic acid to undergo a substitution reaction, and the oil phase of the substitution reaction liquid after oil-water separation is washed, desolventized and dried.

[0023] The invention provides a green nitration device, comprising a methylbenzoic acid nitration reaction unit and a substituted aniline nitration reaction unit, wherein a discharge port of the methylbenzoic acid nitration reaction unit is connected to a feed port of a first solid-liquid separator, a first liquid phase outlet of the first solid-liquid separator is connected to a feed port of a crystallization kettle, the discharge port of the crystallization kettle is connected to a feed port of a second solid-liquid separator, a second liquid phase outlet of the second solid-liquid separator is connected to a feed port of a temporary storage tank, the discharge port of the temporary storage tank is connected to an acid inlet of the substituted aniline nitration reaction unit through a liquid feed pump, the discharge port of the substituted aniline nitration reaction unit is connected to a feed port of a first oil-water separator, an oil outlet of the first oil-water separator is connected to a feed port of a product refining and separation unit, the methylbenzoic acid nitration reaction unit is provided with a methylbenzoic acid inlet and a nitric acid inlet, the crystallization kettle is further provided with a water inlet, and the substituted aniline nitration reaction unit is further provided with a substituted aniline solution inlet.

[0024] In the present invention, the methylbenzoic acid nitration reaction unit is provided with at least one methylbenzoic acid inlet and at least one nitric acid inlet, which are used to input methylbenzoic acid and nitric acid respectively, and at least one outlet is also provided for outputting the first nitration reaction liquid. Preferably, the methylbenzoic acid feeding device adopts a screw feeder for conveying solid methylbenzoic acid into the methylbenzoic acid nitration reaction unit, and the nitric acid feeding device selects a diaphragm pump or a centrifugal pump. The methylbenzoic acid reaction unit is selected from at least one primary dynamic tubular reactor, a reactor, or a dynamic tubular reactor and a reactor connected in series, and continuous production can be achieved.

[0025] Specifically, the methyl benzoic acid reaction unit is selected from at least one dynamic tubular reactor connected in series or in parallel, or at least one reactor connected in series or in parallel, or at least one dynamic tubular reactor connected in series and at least one reactor, which can be one dynamic tubular reactor, two dynamic tubular reactors connected in series, two reactors connected in parallel, three reactors connected in series, one dynamic tubular reactor connected in series and one reactor. The dynamic tubular reactor is a tubular reactor with a stirring shaft, which is driven by a motor to rotate the stirring shaft to promote mass transfer, and heat exchange is performed through an outer jacket. The reactor is a stirred kettle with a jacket for heat exchange, and is provided with an overflow port.

[0026] In the present invention, the substituted aniline nitration reaction unit is provided with at least one acid inlet and at least one substituted aniline solution inlet, which are used to input the second liquid phase and the substituted aniline solution respectively, and at least one outlet is provided for outputting the second nitration reaction liquid. The substituted aniline nitration reaction unit is selected from a microchannel reactor or a microchannel reactor and a tubular reactor connected in series, which can realize continuous production and improve production efficiency by realizing one-step reaction.

[0027] Specifically, the substituted aniline nitration reaction unit can be a microchannel reactor, or a microchannel reactor and a tubular reactor connected in series. The tubular reactor is selected from a dynamic tubular reactor or a static tubular reactor. The microchannel reactor is a plate-type reactor having a reaction channel and a heat exchange channel. The static tubular reactor is a tubular reactor with internal turbulent fins and an external jacket for heat exchange.

[0028] In the present invention, the first solid-liquid separator is provided with an inlet, a first liquid phase outlet and a first solid phase outlet. The feed inlet of the first solid-liquid separator is connected to the discharge port of the methyl benzoic acid nitration reaction unit through a pipeline, so as to perform solid-liquid separation on the first nitration reaction liquid. The separated first product replaces benzoic acid and is discharged from the first solid phase outlet, and the separated first liquid phase is discharged through the first liquid phase outlet.

[0029] In the present invention, the second solid-liquid separator is provided with a feed port, a second solid phase outlet, and a second liquid phase outlet. The feed port of the second solid-liquid separator is connected to the discharge port of the crystallization kettle through a pipeline, and is used for solid-liquid separation of the material flowing out of the crystallization kettle. The separated first product substituted benzoic acid is discharged from the second solid phase outlet, and the separated second liquid phase is discharged through the second liquid phase outlet.

[0030] Specifically, the first solid-liquid separator and the second solid-liquid separator are both selected from one of a top-suspended centrifuge, a horizontal scraper centrifuge, a tripod centrifuge, and a plate and frame filter press, preferably a horizontal scraper centrifuge.

[0031] In the present invention, the crystallization kettle is provided with a feed inlet, a water inlet, and a discharge port, and the feed inlet of the crystallization kettle is connected to the first liquid phase outlet of the first solid-liquid separator. The crystallization kettle is composed of a kettle body, a feed pipe, a discharge pipe, a jacket, a stirring motor, a stirring shaft, a U-shaped stirring paddle, and a scraper. The first liquid phase separated from the first solid-liquid separator flows into the crystallization kettle through the feed pipe, and water enters the crystallization kettle from the water inlet of the crystallization kettle. The stirring motor drives the stirring shaft and the U-shaped stirring paddle to rotate, and the nitric acid in the first liquid phase is diluted with water to reduce the solubility of nitric acid in the first product, so that the first product is precipitated from the nitric acid to form a slurry.

[0032] In the present invention, the temporary storage tank is designed in multiple groups in parallel, which is used for temporarily storing the second liquid phase, and the temporary storage tank structure is preferably vertical. The liquid feed pump is connected to the bottom outlet of the temporary storage tank and the acid inlet of the substituted aniline nitration reaction unit through a pipeline, which is used to pump the second liquid phase in the temporary storage tank into the substituted aniline nitration reaction unit, and the liquid feed pump is selected from a centrifugal pump, a diaphragm pump or a rotary pump, preferably a diaphragm pump.

[0033] In the present invention, the first oil-water separator is provided with a feed inlet, an oil outlet, and a water outlet. The feed inlet of the first oil-water separator is connected to the outlet of the substituted aniline nitration reaction unit, and is used to separate oil and water from the second nitration reaction liquid from the substituted aniline nitration reaction unit, and the water phase leaves the first oil-water separator through the water outlet, and the oil phase leaves the first oil-water separator through the oil outlet. The first oil-water separator is selected from a centrifugal oil-water separator with a hydrophobic membrane or a static phase separation tank, preferably a centrifugal oil-water separator with a hydrophobic membrane.

[0034] In the present invention, the nitrification device also includes an alkali adjustment unit, the oil outlet of the first oil-water separator is connected to the feed port of the alkali adjustment unit, the oil outlet of the alkali adjustment unit is connected to the feed port of the product refining and separation unit, and the alkali adjustment unit is a alkali adjustment kettle and a second oil-water separator connected in sequence.

[0035] The present invention uses the second liquid phase separated by the second solid-liquid separator for nitration of substituted aniline. When a small amount of substituted benzoic acid is dissolved in the second liquid phase in addition to nitric acid, after the second liquid phase undergoes nitration reaction with the substituted aniline to generate nitro-substituted aniline, the substituted benzoic acid will coexist with the nitro-substituted aniline in the oil phase, affecting the quality of the nitro-substituted aniline. In order to obtain high-quality nitro-substituted aniline, as a preferred embodiment of the present invention, the substituted benzoic acid in the nitro-substituted aniline is removed by adding an alkali adjustment unit. The alkali adjustment unit is composed of an alkali adjustment kettle and a second oil-water separator. The alkali adjustment kettle adjusts the oil phase separated by the first oil-water separator by alkali liquid. After the alkali adjustment, the first product substituted benzoic acid is converted into a substituted benzoate and dissolved in the water phase, while the nitro-substituted aniline is still dissolved in the oil phase. The second oil-water separator separates the oil and water phases to separate the substituted benzoate and the nitro-substituted aniline. The alkali adjustment kettle is preferably a reactor with a jacket heat exchanger, the second oil-water separator is selected from a centrifugal oil-water separator or a static phase separation tank, preferably a centrifugal oil-water separator, and the alkali solution is selected from sodium hydroxide solution, sodium bicarbonate solution or sodium carbonate solution, preferably sodium hydroxide solution.

[0036] In the present invention, the nitration device also includes an acid adjustment unit, the water outlet of the alkali adjustment unit is connected to the feed port of the acid adjustment unit, and the acid adjustment unit is an acid adjustment kettle and a third solid-liquid separator connected in sequence. If the aqueous phase separated by the alkali adjustment unit and containing substituted benzoate is directly treated as wastewater, it will cause waste of the first product substituted benzoic acid. In order to improve the yield of the first product substituted benzoic acid, in a preferred embodiment of the present invention, by adding an acid adjustment unit, the substituted benzoate in the aqueous phase is converted into substituted benzoic acid, and the first product substituted benzoic acid is recovered. The acid adjustment unit is an acid adjustment kettle and a third solid-liquid separator connected in series, and the acid adjustment kettle is preferably a reactor with a jacket heat exchanger. The aqueous phase separated from the second oil-water separator is acidified by adding acid. During the acid adjustment process, the substituted benzoate dissolved in the aqueous phase reacts with the acid to generate substituted benzoic acid, which is precipitated from the aqueous phase. The third solid-liquid separator is used to separate the material from the acid adjustment kettle, and the recovered first product is obtained after separating the aqueous phase. The third solid-liquid separator is selected from a top-suspended centrifuge, a horizontal scraper centrifuge, a tripod centrifuge or a plate and frame filter press, preferably a horizontal scraper centrifuge, and the acid solution is selected from dilute nitric acid, dilute hydrochloric acid or dilute sulfuric acid, preferably dilute nitric acid.

[0037] In the present invention, the product refining and separation unit includes a substitution reaction unit, a separation unit, a distillation kettle, and a dryer. The separation unit is an oil-water separator and a two-stage washing and separation two-in-one device connected in sequence, or a solid-liquid separator, an oil-water separator and a two-stage washing and separation two-in-one device connected in sequence, or an oil-water separator and a three-stage washing and separation two-in-one device connected in sequence, or a solid-liquid separator, an oil-water separator and a three-stage washing and separation two-in-one device connected in sequence.

[0038] The second nitration reaction liquid obtained from the substituted aniline nitration reaction unit contains not only the second product nitro-substituted aniline but also a small amount of nitrite impurities. In order to obtain high-quality nitro-substituted aniline, in an embodiment of the present invention, the oil phase inlet of the substitution reaction unit in the product refining and separation unit is directly connected to the oil outlet of the first oil-water separator, and the oil phase separated by the first oil-water separator is refined and separated. Preferably, the oil phase inlet of the substitution reaction unit in the product refining and separation unit is connected to the oil outlet of the second oil-water separator in the alkali adjustment unit, and the oil phase separated by the second oil-water separator is refined and separated.

[0039] In the present invention, the substitution reaction unit is a place for converting nitrous impurities into nitro-substituted aniline, and is provided with at least three inlets, at least one hydrochloric acid inlet for inputting hydrochloric acid, at least one aminosulfonic acid inlet for inputting aminosulfonic acid, at least one oil phase inlet for inputting the oil phase separated by the first oil-water separator or the oil phase separated by the second oil-water separator, and at least one outlet for outputting the substitution reaction liquid. The substitution reaction unit is selected from a dynamic tubular reactor or a reactor provided with an overflow port, preferably a dynamic tubular reactor.

[0040] In an embodiment of the present invention, the separation unit can be a two-in-one device of an oil-water separator and a two-stage washing separation connected in sequence. First, the substitution reaction liquid from the substitution reaction unit is subjected to oil-water separation, the water phase is separated and removed, and the oil phase containing the second product nitro-substituted aniline is subjected to two-stage washing separation to remove impurities in the oil phase. The two-stage washing separation can be alkali washing and water washing in sequence; the separation unit can also be a solid-liquid separator, an oil-water separator and a two-stage washing separation two-in-one device connected in sequence. First, the substitution reaction liquid from the substitution reaction unit is subjected to solid-liquid separation to remove aminosulfonic acid that does not participate in the reaction, and the separated liquid phase is subjected to oil-water separation to separate and remove the water phase. The oil phase containing the second product nitro-substituted aniline is subjected to two-stage washing separation to remove impurities in the oil phase. The two-stage washing separation can be alkali washing and water washing in sequence. Washing; the separation unit can also be an oil-water separator and a three-stage washing separation two-in-one device connected in sequence. First, the substitution reaction liquid from the substitution reaction unit is subjected to oil-water separation, the water phase is separated and removed, and the oil phase containing the second product nitro-substituted aniline is subjected to three-stage washing separation to remove impurities in the oil phase. The three-stage washing separation can be water washing, alkali washing, and water washing in sequence; the separation unit can also be a solid-liquid separator, an oil-water separator and a three-stage washing separation two-in-one device connected in sequence. First, the substitution reaction liquid from the substitution reaction unit is subjected to solid-liquid separation to remove aminosulfonic acid that does not participate in the reaction, and the separated liquid phase is subjected to oil-water separation to separate and remove the water phase. The oil phase containing the second product nitro-substituted aniline is subjected to three-stage washing separation to remove impurities in the oil phase. The three-stage washing separation can be water washing, alkali washing, and water washing in sequence. The washing and separation two-in-one device is a device integrating oil-water separation and washing functions, and is provided with a feed inlet, a washing agent inlet, an oil phase outlet, and a water phase outlet. The washing and separation two-in-one device has at least two stages, and the two-stage washing and separation two-in-one device is a two-stage washing and separation two-in-one device connected in series, and the three-stage washing and separation two-in-one device is a three-stage washing and separation two-in-one device connected in series. On this basis, more complex series or parallel combinations should also be within the scope of the present invention.

[0041] In the present invention, the oil phase outlet of the last stage washing and separation two-in-one device in the separation unit is connected to the inlet of the distillation kettle, and the concentrated liquid outlet of the distillation kettle is connected to the inlet of the dryer. The distillation kettle and the dryer are used for desolventizing and drying the product respectively. The oil phase from the separation unit enters the distillation kettle for distillation and solvent removal, and then is dried by the dryer to obtain the second product nitro-substituted aniline. The distillation kettle is selected from a conventional stirring kettle with a condenser, and the dryer is selected from a disc dryer, a rake dryer, a vacuum dryer, a drum dryer, a belt dryer, and a film dryer.

[0042] In the present invention, the substituted aniline solution is a mixed solution of substituted aniline and ethylene dichloride prepared in a mass ratio, and the ethylene dichloride evaporated from the distillation kettle in the product refining and separation unit is cooled and recovered and then pumped to the batching kettle together with the substituted aniline and fresh ethylene dichloride to prepare the substituted aniline solution. The preparation process is automatically controlled, and the batching kettle is preferably a stirred kettle with a jacket.

[0043] The present invention also provides a green nitration process, using the green nitration device described above, comprising the following steps:

[0044] S1: Toluic acid and nitric acid enter the toluic acid nitration reaction unit to undergo nitration reaction to obtain a first nitration reaction liquid.

[0045] S2: The first nitration reaction liquid enters the first solid-liquid separator for separation to obtain the first product and the first liquid phase.

[0046] S3: The first liquid phase enters the crystallization kettle, is diluted with water and crystallized, and then transferred to the second solid-liquid separator. After separation in the second solid-liquid separator, the first product and the second liquid phase are obtained. The second liquid phase enters the temporary storage tank through the pipeline for temporary storage.

[0047] S4: the substituted aniline solution and the second liquid phase enter the substituted aniline nitration reaction unit to undergo nitration reaction to obtain a second nitration reaction solution.

[0048] S5: The second nitration reaction liquid enters the first oil-water separator for oil-water separation, and the separated oil phase enters the product refining and separation unit for refining operation to obtain the second product nitro-substituted aniline.

[0049] Specifically, the methyl benzoic acid is selected from one of m-methyl benzoic acid, p-methyl benzoic acid and o-methyl benzoic acid.

[0050] The present invention has been found through research that the waste nitric acid obtained after separating the product substituted benzoic acid from the first nitration reaction liquid of methyl benzoic acid and nitric acid still has good nitration ability within a certain concentration range, the nitration process of nitro-substituted aniline usually adopts a process of first forming a salt with dilute nitric acid and then nitrifying with concentrated nitric acid, and the waste nitric acid generated after the nitration reaction of methyl benzoic acid and nitric acid can be directly used for the nitration reaction of substituted aniline without being refined and impurity-removing treatment, which can not only realize the efficient utilization of the waste nitric acid, but also will not affect the quality of the second product nitro-substituted aniline. The waste nitric acid generated after the nitration reaction of methyl benzoic acid and nitric acid and the substituted aniline are used for one-step nitration to smoothly produce nitro-substituted aniline, avoiding the equipment investment for concentrating and recovering the waste nitric acid, and also avoiding the safety hazards in the concentration process, thereby realizing the comprehensive utilization of nitric acid.

[0051] Methylbenzoic acid is a solid material, which is transported to the methylbenzoic acid nitration reaction unit by a screw feeder. At the same time, nitric acid is pumped into the methylbenzoic acid nitration reaction unit by a liquid feed pump to react with methylbenzoic acid to obtain a first nitration reaction liquid containing the first product, substituted benzoic acid. In the first nitration reaction liquid, part of the first product is precipitated in the form of a solid, and part of the first product is dissolved in nitric acid. The first nitration reaction liquid enters the first solid-liquid separator for separation to obtain a solid phase first product and a first liquid phase whose main components are nitric acid and substituted benzoic acid. The first liquid phase is added to a crystallization kettle and diluted with water to precipitate the first product, substituted benzoic acid. The material after crystallization is transferred to the second solid-liquid separator by a material transfer pump. After separation by the second solid-liquid separator, the first product and the second liquid phase are obtained. At this time, the main component of the second liquid phase is nitric acid. The second liquid phase enters a temporary storage tank through a pipeline for temporary storage in preparation for the nitration reaction of substituted aniline. The substituted aniline solution and the second liquid phase from the temporary storage tank enter the substituted aniline nitration reaction unit to undergo nitration reaction to obtain a second nitration reaction liquid containing the second product nitro-substituted aniline. Due to the participation of the solvent ethylene dichloride, the second nitration reaction liquid presents an oil-water two-phase, and the second product is dissolved in the oil phase. The second nitration reaction liquid enters the first oil-water separator for oil-water separation, and the separated oil phase enters the product refining separation unit for refining to obtain the second product nitro-substituted aniline.

[0052] The present invention has been found through research that in step S1, the higher the concentration of nitric acid used for nitrification of methylbenzoic acid, the stronger the activity of the nitration reaction, the faster the nitration reaction rate, but may cause an increase in by-products; on the contrary, the lower the concentration of nitric acid, the weaker the activity of the nitration reaction, and the slower the nitration reaction rate. As a preferred solution, the concentration of nitric acid is selected from 85 to 98%, and further preferably, the concentration of nitric acid is 88 to 95%, and more preferably, the concentration of nitric acid is 90 to 93%. Because water is generated during the reaction of methylbenzoic acid and nitric acid, in order to avoid excessive reduction in the concentration of nitric acid and ensure the conversion rate of methylbenzoic acid, as a preferred solution, the molar ratio of methylbenzoic acid to nitric acid is 1: (5 to 10), and further preferably, the molar ratio of methylbenzoic acid to nitric acid is 1: (6 to 9), and more preferably, the molar ratio of methylbenzoic acid to nitric acid is 1: (7 to 8).

[0053] In step S1, when the nitric acid concentration and the molar ratio of methylbenzoic acid to nitric acid are determined, the higher the reaction temperature, the shorter the reaction time, and the higher the production efficiency. However, if the temperature is too high, the by-products increase, the reaction is difficult to control, and the safety risk increases. On the contrary, the lower the reaction temperature, the longer the reaction time. In order to improve product quality and ensure production efficiency, as a preferred solution, the present invention selects a reaction temperature of -30 to 0°C and a reaction time of 1 to 30 minutes. More preferably, the reaction temperature is -20 to 10°C and the reaction time is 10 to 20 minutes.

[0054] Since part of the first product, substituted benzoic acid, is dissolved in the first liquid phase, the present invention reduces the solubility of the first product in nitric acid by reducing the concentration of nitric acid, thereby allowing the first product to precipitate in the first liquid phase. After diluting the first liquid phase, the lower the concentration of nitric acid, the smaller the solubility of the first product in nitric acid, the more the first product originally dissolved in the first liquid phase is precipitated, the less the first product remaining in the second liquid phase after separation, and the smaller the impact on the quality of the second product, nitro-substituted aniline. However, if the concentration of nitric acid after dilution is too low, the reaction rate of substituted aniline and nitric acid will be reduced. In order to precipitate the first product as much as possible without affecting the nitration reaction of the second liquid phase and substituted aniline in step S4, the present invention selects the concentration of nitric acid in the second liquid phase in step S3 to be 40-70%, preferably 50-60%.

[0055] In step S4, the substituted aniline solution is a mixed solution of substituted aniline and ethylene dichloride. The higher the mass ratio of substituted aniline to ethylene dichloride, the less ethylene dichloride is used. The higher the concentration of the substituted aniline solution, the higher the reaction rate, and the lower the energy consumption of recovering the solvent. However, the heat in the reaction system is more likely to accumulate, and untimely heat exchange may lead to local overheating or runaway reaction. On the contrary, the lower the mass ratio of substituted aniline to ethylene dichloride, the more ethylene dichloride is used. The lower the concentration of the substituted aniline solution, the easier it is to control the reaction temperature, but the cost of recovering the solvent is higher. In the present invention, it is preferred that the mass ratio of substituted aniline to ethylene dichloride is 1: (1 to 3), and more preferably 1: (1.5 to 2).

[0056] In step S4, the substituted aniline solution and the second liquid phase simultaneously enter the substituted aniline nitration reaction unit, and a nitration reaction occurs in the substituted aniline nitration reaction unit to obtain a second nitration reaction solution. The higher the mass ratio of substituted aniline to the second liquid phase, the less the amount of the second liquid phase, that is, the less the amount of nitric acid, the lower the conversion rate of substituted aniline, and the lower the product yield; the lower the mass ratio of substituted aniline to the second liquid phase, the more the amount of the second liquid phase, that is, the more the amount of nitric acid, the more complete the nitration reaction, and the higher the product yield, but the use of excessive nitric acid will cause waste of nitric acid. In order to ensure the yield of the second product, make full use of the waste nitric acid generated in the production process of substituted benzoic acid, and reduce resource waste, the mass ratio of substituted aniline to the second liquid phase in the nitration device controlled by the present invention is 1: (2 to 4), and as a preferred embodiment, the mass ratio of substituted aniline to the second liquid phase is 1: (2 to 3).

[0057] In step S4, in order to further ensure the conversion rate of substituted aniline and improve the purity of nitro-substituted aniline, as a preferred technical solution, the reaction temperature is 60-80°C, the pressure is 0.1-0.3 MPa, and the reaction time is 10-300 s. The setting of the pressure can promote the reaction rate of the substituted aniline and the second liquid phase. More preferably, the reaction temperature is 65-70°C, the pressure is 0.2-0.25 MPa, and the reaction time is 100-200 s.

[0058] The second nitration reaction liquid obtained in step S4 contains nitro-substituted aniline, N-(1-ethylpropyl)-N-nitroso-3,4-dimethyl-2,6-dinitroaniline (nitroso for short), ethylene dichloride, nitric acid, and water. Both nitro-substituted aniline and nitroso are dissolved in ethylene dichloride. In step S5, the second nitration reaction liquid enters the first oil-water separator for oil-water separation. After separation by the first oil-water separator, an oil phase containing nitro-substituted aniline, nitroso, and ethylene dichloride is obtained. The oil phase enters the product refining and separation unit for refining operation to obtain the second product nitro-substituted aniline.

[0059] Since the by-product nitrite is highly toxic and induces mutation, the oil phase separated by the first oil-water separator is refined to convert nitrite into nitro-substituted aniline. The oil phase separated by the first oil-water separator enters the substitution reaction unit simultaneously with hydrochloric acid and aminosulfonic acid. Nitrite is mixed with hydrochloric acid and aminosulfonic acid to undergo substitution reaction to generate a substitution reaction liquid containing nitro-substituted aniline. The substitution reaction liquid presents two phases of oil and water. The oil phase is nitro-substituted aniline dissolved in dichloroethane, and the water phase is hydrochloric acid and aminosulfonic acid dissolved in water. When the aminosulfonic acid is excessive, the substitution reaction liquid presents three phases of solid phase, oil phase and water phase. The solid phase is aminosulfonic acid that does not participate in the reaction. The substitution reaction liquid is separated in the separation unit, and the oil phase is collected and then washed. It can be washed with alkali and water in sequence, or washed with water, alkali and water in sequence. Sodium hydroxide solution or sodium carbonate solution can be used for alkali washing. The washed oil phase is distilled in a distillation kettle to remove the solvent dichloroethane, and then dried in a dryer to obtain the second product nitro-substituted aniline.

[0060] In order to improve the quality of nitro-substituted aniline, in a preferred embodiment of the present invention, the oil phase separated by the first oil-water separator in step S5 first enters the alkali adjustment unit before entering the product refining and separation unit, and is mixed with alkali solution in the alkali adjustment kettle of the alkali adjustment unit to adjust the pH to 8-14, and the mixing and stirring time is 1-3 hours. At this time, the substituted benzoic acid in the oil phase reacts with the alkali solution to generate substituted benzoate dissolved in the water phase, while the nitro-substituted aniline is still dissolved in the oil phase. The oil phase and the water phase are separated by the second oil-water separator of the alkali adjustment unit, so as to separate the substituted benzoic acid in the nitro-substituted aniline, and the separated oil phase enters the product refining and separation unit to perform the operation of step S5 to obtain high-purity nitro-substituted aniline. The alkali solution is selected from sodium hydroxide solution, sodium bicarbonate solution or sodium carbonate solution. In order to reduce the consumption of alkali solution and ensure that the substituted benzoic acid in the oil phase separated by the first oil-water separator is completely converted into substituted benzoate, more preferably, the pH is 9-10 and the mixing time is 1.5-2 hours.

[0061] In order to improve the yield of the first product, substituted benzoic acid, in a preferred embodiment of the present invention, the water phase separated by the second oil-water separator in the alkali adjustment unit enters the acid adjustment unit, and is mixed with dilute acid in the acid adjustment kettle to adjust the pH to 0-3. After mixing for 1-3 hours, the substituted benzoate reacts with the acid to generate substituted benzoic acid which precipitates from the dilute acid. The material after acid adjustment enters the third solid-liquid separator of the acid adjustment unit to separate the solid phase and the liquid phase. The separated solid phase is the recovered first product, which is combined with the first product separated in step S2 and step S3 to calculate the yield of the first product. The dilute acid is selected from dilute nitric acid, dilute hydrochloric acid or dilute sulfuric acid, preferably dilute nitric acid. As a preferred embodiment, the pH of the acid adjustment process is 1-2, and the mixing time is 1.5-2h.

[0062] The technical solution provided by the embodiment of the present invention has the following advantages compared with the prior art:

[0063] (1) The present invention uses the waste nitric acid after the nitration reaction of methyl benzoic acid directly for the nitration reaction of substituted aniline without refining and impurity removal treatment, abandons the treatment method of waste nitric acid to form salt or concentrate, avoids the generation of a large amount of waste salt, and also avoids the decomposition loss of waste nitric acid and the generation of waste gas during the concentration process, and avoids the high energy consumption and safety hazards of concentration, realizes the comprehensive utilization of waste nitric acid, obtains qualified product nitro-substituted aniline, reduces the equipment investment for waste nitric acid treatment, reduces production costs, reduces environmental pollution, and realizes green production.

[0064] (2) The present invention uses waste nitric acid after the nitration reaction of methyl benzoic acid and substituted aniline to directly nitrate in one step to produce nitro-substituted aniline, avoiding the steps of salt formation, separation of salt reaction liquid, recovery of dilute nitric acid and extraction of aniline salt in dilute nitric acid. The process is simple, the operation is easy, the conversion rate is high, the waste of resources is reduced, and the safety hazard is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0066] Figure 1 This is a schematic diagram of the structure of the nitro-substituted aniline nitration device used in Example 1 of the present invention;

[0067] Figure 2 This is a schematic diagram of the structure of the product refining and separation unit used in Example 2 of the present invention;

[0068] Figure 3 This is a schematic diagram of the structure of the nitro-substituted aniline nitration device used in Example 3 of the present invention;

[0069] Figure 4 This is a schematic diagram of the structure of the nitro-substituted aniline nitration device used in Example 4 of the present invention.

[0070] Description of reference numerals:

[0071] A-methylbenzoic acid nitration device, 1-methylbenzoic acid nitration reaction unit, 2-first solid-liquid separator, 3-crystallization kettle, 4-second solid-liquid separator, 5-temporary storage tank, 6-liquid feed pump, 7-substituted aniline nitration reaction unit, 8-first oil-water separator, 9-product refining separation unit, 91-substitution reaction unit, 92-separation unit, 93-distillation kettle, 94-dryer, 10-alkali adjustment unit, 101-alkali adjustment kettle, 102-second oil-water separator, 11-acid adjustment unit, 111-acid adjustment kettle, 112-third solid-liquid separator. DETAILED DESCRIPTION

[0072] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0073] The following examples are provided to better further understand the present invention, but are not limited to the best implementation mode described, and do not constitute a limitation on the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the enlightenment of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention. Unless otherwise clearly specified or limited, the connection mode between each unit or device should be understood in a broad sense. For example, it can be direct pipeline connection, or it can be connected through pipelines connected to conventional transportation, metering, control, and temporary storage equipment such as pumping equipment, metering equipment, valve fittings, and intermediate tanks. It can be fixed connection or detachable connection. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0074] In the present invention, various components of the production device, such as a dynamic tubular reactor, a tubular reactor, a microchannel reactor, a solid-liquid separator, a reaction kettle, a temporary storage tank, an oil-water separator, a washing and separation two-in-one device, a distillation kettle, a dryer, etc. can all be commercially available on the market, but the entire device cannot be commercially available on the market and is not known to those skilled in the art.

[0075] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0076] Example 1

[0077] This embodiment provides a green nitrification device, and its structural schematic diagram is as follows Figure 1 As shown, it includes a methyl benzoic acid nitration device A; a liquid feed pump 6; a substituted aniline nitration reaction unit 7; a first oil-water separator 8; and a product refining and separation unit 9. The methyl benzoic acid nitration device A is composed of a methyl benzoic acid nitration reaction unit 1, a first solid-liquid separator 2, a crystallization kettle 3, a second solid-liquid separator 4, and a temporary storage tank 5.

[0078] In the methyl benzoic acid nitration device A, the feed port of the methyl benzoic acid nitration device A is the feed port of the methyl benzoic acid nitration reaction unit 1, the discharge port of the methyl benzoic acid nitration reaction unit 1 is connected to the feed port of the first solid-liquid separator 2, the first liquid phase outlet of the first solid-liquid separator 2 is connected to the feed port of the crystallization kettle 3, the crystallization kettle 3 is also provided with a water inlet, the discharge port of the crystallization kettle 3 is connected to the feed port of the second solid-liquid separator 4, and the second liquid phase outlet of the second solid-liquid separator 4 is connected to the temporary storage The feed port of the methyl benzoic acid nitration device A is connected to the feed port of the temporary storage tank 5, the discharge port of the methyl benzoic acid nitration device A is connected to the acid inlet of the substituted aniline nitration reaction unit 7 through a liquid feed pump 6, the substituted aniline nitration reaction unit 7 is also provided with a substituted aniline solution inlet, the discharge port of the substituted aniline nitration reaction unit 7 is connected to the feed port of the first oil-water separator 8, and the oil outlet of the first oil-water separator 8 is connected to the feed port of the product refining and separation unit 9.

[0079] Example 2

[0080] This embodiment provides a green nitrification device, and its structural schematic diagram is as follows Figure 1 and Figure 2 As shown, the structural diagram of the product refining and separation unit 9 is as follows Figure 2 As shown, the product purification and separation unit 9 is composed of a substitution reaction unit 91 , a separation unit 92 , a distillation kettle 93 , and a dryer 94 .

[0081] On the basis of Example 1, the feed port of the product refining and separation unit 9 is the oil phase inlet of the substitution reaction unit 91, and the substitution reaction unit 91 is also provided with a hydrochloric acid inlet and an aminosulfonic acid inlet. The discharge port of the substitution reaction unit 91 is connected to the feed port of the separation unit 92, and the discharge port of the separation unit 92 is connected to the feed port of the distillation kettle 93, and the discharge port of the distillation kettle 93 is connected to the feed port of the dryer 94, and the discharge port of the dryer 94 is the discharge port of the product refining and separation unit 9.

[0082] Example 3

[0083] This embodiment provides a green nitrification device, and its structural schematic diagram is as follows Figure 3 As shown, the difference from Example 2 is that this embodiment is further provided with an alkali adjustment unit 10 , wherein the alkali adjustment unit 10 is composed of an alkali adjustment kettle 101 and a second oil-water separator 102 .

[0084] On the basis of Example 2, the oil outlet of the first oil-water separator 8 is connected to the feed port of the alkali adjustment kettle 101, the feed port of the alkali adjustment kettle 101 is connected to the feed port of the second oil-water separator 102, and the oil outlet of the second oil-water separator 102 is connected to the feed port of the product refining and separation unit 9.

[0085] Example 4

[0086] This embodiment provides a green nitrification device, and its structural schematic diagram is as follows Figure 4 As shown, the difference from Example 3 is that this embodiment is further provided with an acid conditioning unit 11 , wherein the acid conditioning unit 11 is composed of an acid conditioning kettle 111 and a third solid-liquid separator 112 .

[0087] On the basis of Example 3, the water outlet of the second oil-water separator 102 is connected to the feed port of the acid regulating kettle 111 , and the discharge port of the acid regulating kettle 111 is connected to the feed port of the third solid-liquid separator 112 .

[0088] Example 5

[0089] This embodiment provides a green nitration process, using the green nitration device provided in Example 2, wherein the methyl benzoic acid nitration reaction unit 1 is selected from a two-stage series dynamic tubular reactor, the substituted aniline nitration reaction unit 7 is selected from a microchannel reactor, the substitution reaction unit 91 is selected from a dynamic tubular reactor, and the separation unit 92 is an oil-water separator and a two-stage washing and separation two-in-one device connected in sequence.

[0090] Meta-methylbenzoic acid and 98% nitric acid enter the methylbenzoic acid nitration reaction unit 1 from the inlet of the two-stage series dynamic tubular reactor at flow rates of 13.62g / min and 32.15g / min, respectively, wherein the molar ratio of meta-methylbenzoic acid to nitric acid is 1:5, the reaction temperature is controlled to be 0°C, the reaction residence time is 1min, and after the reaction is stable, the first nitration reaction liquid is collected from the outlet of the two-stage series dynamic tubular reactor, and the collection is continuously collected for 20min. After testing, the conversion rate of methylbenzoic acid in the first nitration reaction liquid is 99.7%. The collected first nitration reaction liquid is separated into the first product and the first liquid phase by the first solid-liquid separator 2, and the separated first liquid phase enters the crystallization kettle 3, and 0.71kg of water is added for dilution. The diluted first liquid phase is separated into the first product and the second liquid phase by the second solid-liquid separator 4, and the second liquid phase enters the temporary storage tank 5 for temporary storage. At this time, the nitric acid concentration in the second liquid phase is 40%, and the first product separated twice is collected. After drying, the total mass of substituted benzoic acid is 3.55kg, and the yield is 98%.

[0091] The substituted aniline solution and the second liquid phase with a nitric acid concentration of 40% in the temporary storage tank 5 enter the substituted aniline nitration reaction unit 7 from the inlet end of the microchannel reactor at flow rates of 126.74 g / min and 63.37 g / min, respectively. The mass ratio of substituted aniline to the second liquid phase is 1:2, and the mass ratio of substituted aniline to ethylene dichloride in the substituted aniline solution is 1:3. The reaction temperature is controlled to be 60° C., the pressure of the reaction system is 0.1 MPa, and the reaction residence time is 300 s. The second liquid phase fully participates in the nitration reaction of the substituted aniline. The second nitration reaction liquid generated enters the first oil-water separator 8 from the outlet of the microchannel reactor. , the oil and water phases are continuously separated by the first oil-water separator 8, and the oil phase continuously separated by the first oil-water separator 8 directly enters the dynamic tubular reactor, and at the same time, aminosulfonic acid and 31% hydrochloric acid enter the device from the inlet of the dynamic tubular reactor at flow rates of 2.41g / min and 5.85g / min respectively to undergo substitution reaction, the reaction temperature is 100°C, and the reaction is carried out until nitrite is less than 0.02%, and the substitution reaction liquid is collected from the outlet of the dynamic tubular reactor, and the oil phase separated by the first oil-water separator 8 is completely involved in the substitution reaction. The conversion rate of substituted aniline in the reaction liquid is 99.6%, and the selectivity of the product is 99.96%. The collected substitution reaction liquid enters the oil-water separator and the two-stage washing and separation two-in-one device connected in sequence, and the oil phase obtained after oil-water separation enters the distillation kettle 93 after alkali washing and water washing to distill and recover the organic solvent dichloroethane, and the heavy components in the distillation kettle 93 enter the dryer 94 for drying, and the total mass of the nitro-substituted aniline after drying is 9.25kg, and the yield is 99.3%.

[0092] Example 6

[0093] This embodiment provides a green nitration process, using the green nitration device provided in Example 4, wherein the methyl benzoic acid nitration reaction unit 1 is selected from a primary dynamic tubular reactor, the substituted aniline nitration reaction unit 7 is selected from a secondary microchannel reactor connected in series, the substitution reaction unit 91 is selected from a reactor, and the separation unit 92 is a solid-liquid separator, an oil-water separator and a three-stage washing separation two-in-one device connected in sequence.

[0094] p-Toluic acid and 93% nitric acid enter the methyl benzoic acid nitration reaction unit 1 from the inlet of the first-stage dynamic tubular reactor at flow rates of 13.62 g / min and 47.43 g / min, respectively, wherein the molar ratio of p-toluic acid to nitric acid is 1:7, the reaction temperature is controlled to be -10°C, the reaction residence time is 15 min, and after the reaction is stable, the first nitration reaction liquid is collected from the outlet of the first-stage dynamic tubular reactor, and the collection is continuously collected for 20 min. The conversion rate of p-toluic acid in the first nitration reaction liquid is tested to be 99.8%. The collected first nitration reaction liquid is separated into the first product and the first liquid phase by the first solid-liquid separator 2, and the separated first liquid phase enters the crystallization kettle 3, and 0.52 kg of water is added for dilution. The diluted first liquid phase is separated into the first product and the second liquid phase by the second solid-liquid separator 4, and the second liquid phase enters the temporary storage tank 5 for temporary storage, and the nitric acid concentration in the second liquid phase is 55%.

[0095] The substituted aniline solution and the second liquid phase with a nitric acid concentration of 55% in the temporary storage tank 5 enter the substituted aniline nitration reaction unit 7 from the inlet end of the two-stage microchannel reactor connected in series at flow rates of 77.38 g / min and 69.64 g / min, respectively, wherein the mass ratio of the substituted aniline to the second liquid phase is 1:2.7, the mass ratio of the substituted aniline to the ethylene dichloride in the substituted aniline solution is 1:2, the reaction temperature is controlled to be 70° C., the pressure of the reaction system is 0.17 MPa, the reaction residence time is 150 s, and the second liquid phase is fully involved in the nitration reaction of the substituted aniline to produce the second nitration The reaction liquid enters the first oil-water separator 8, and the oil and water phases are separated by the first oil-water separator 8. The oil phase separated from the first oil-water separator 8 enters the alkali adjustment kettle 101, and the pH value is adjusted to 9 by sodium hydroxide solution. After stirring and mixing for 2.5 hours, it is transferred to the second oil-water separator 102 for oil-water separation. The water phase separated from the second oil-water separator 102 enters the acid adjustment kettle 111, and the pH value is adjusted to 0 by dilute nitric acid. After stirring and mixing for 1 hour, it is separated and recovered by the third solid-liquid separator 112 to obtain the first product. The total mass of the first product separated three times is 3.6 kg after drying, and the yield is 99.3%.

[0096] The oil phase separated from the second oil-water separator 102 is all fed into the reactor of the substitution reaction unit 91, and 54.98 g of aminosulfonic acid and 127 g of 31% hydrochloric acid are added at the same time. The substitution reaction takes place at a reaction temperature of 100° C. until the nitrite content is less than 0.02%. The substitution reaction liquid is collected from the outlet of the reactor. The conversion rate of the substituted aniline in the reaction liquid is found to be 99.9%, and the selectivity of the product is 99.98%.

[0097] The above-mentioned substitution reaction liquid enters a solid-liquid separator, an oil-water separator and a three-stage washing and separation two-in-one device which are connected in sequence. The liquid phase obtained after solid-liquid separation is separated into water and oil phases by the oil-water separator. The obtained oil phase is washed with water, washed with alkali and washed with water, and then enters a distillation kettle 93 to distill and recover the organic solvent dichloroethane. The heavy components in the distillation kettle 93 are dried by a dryer 94. The total mass of the nitro-substituted aniline after drying is 7.55 kg, and the yield is 99.5%.

[0098] Example 7

[0099] This embodiment provides a green nitration process, using the green nitration device provided in Example 3, wherein the methyl benzoic acid reaction unit is selected from a primary dynamic tubular reactor, the substituted aniline nitration reaction unit 7 is selected from a microchannel reactor and a dynamic tubular reactor connected in series, the substitution reaction unit 91 is selected from a reactor, and the separation unit 92 is an oil-water separator and a three-stage washing and separation two-in-one device connected in sequence.

[0100] o-Toluic acid and 95% nitric acid enter the methyl benzoic acid nitration reaction unit 1 from the inlet of the first-level dynamic tubular reactor at flow rates of 13.62g / min and 39.8g / min, respectively, wherein the molar ratio of o-toluic acid to nitric acid is 1:6, the reaction temperature is controlled to be -5°C, the reaction residence time is 10min, and after the reaction is stable, the first nitration reaction liquid is collected from the outlet of the first-level dynamic tubular reactor, and the collection is continuously collected for 20min. The conversion rate of o-toluic acid in the first nitration reaction liquid is 99.6% after detection. The collected first nitration reaction liquid is separated into the first product and the first liquid phase by the first solid-liquid separator 2, and the separated first liquid phase enters the crystallization kettle 3, and 0.55kg of water is added for dilution. The diluted first liquid phase is separated into the first product and the second liquid phase by the second solid-liquid separator 4, and the second liquid phase enters the temporary storage tank 5 for temporary storage. At this time, the concentration of nitric acid in the second liquid phase is 50%, and the total mass of the first product separated twice after drying is 3.51kg, and the yield is 97%.

[0101] The substituted aniline solution and the second liquid phase with a nitric acid concentration of 50% in the temporary storage tank 5 enter the substituted aniline nitration reaction unit 7 from the inlet ends of the microchannel reactor and the dynamic tubular reactor connected in series at flow rates of 92.68 g / min and 63.55 g / min, respectively, wherein the mass ratio of the substituted aniline to the second liquid phase is 1:2.4, the mass ratio of the substituted aniline to dichloroethane in the substituted aniline solution is 1:2.5, the reaction temperature is controlled to be 65° C., the pressure of the reaction system is 0.14 MPa, and the reaction stays The time is 200s, and the second liquid phase is completely involved in the nitration reaction of the substituted aniline. The second nitration reaction liquid produced enters the first oil-water separator 8, and the oil and water phases are separated by the first oil-water separator 8. The oil phase separated from the first oil-water separator 8 enters the alkali adjustment kettle 101, and the pH value is adjusted to 8 by sodium hydroxide solution. After stirring and mixing for 3 hours, it is transferred to the second oil-water separator 102 for oil-water separation. The oil phase separated from the second oil-water separator 102 is completely entered into the reactor, and 48.38g of aminosulfonic acid and 114.1g of 31% hydrochloric acid are added at the same time. The substitution reaction occurs at a reaction temperature of 100°C, and the reaction is carried out until the nitrite is less than 0.02%. The substitution reaction liquid is collected from the outlet of the reactor. The conversion rate of the substituted aniline in the reaction liquid is 99.7% and the selectivity of the product is 99.97%.

[0102] The above-mentioned substitution reaction liquid enters an oil-water separator and a three-stage washing and separation two-in-one device which are connected in sequence. The oil phase obtained after oil-water separation is washed with water, washed with alkali, and washed with water, and then enters a distillation kettle 93 for distillation to recover the organic solvent dichloroethane. The heavy components in the distillation kettle 93 enter a dryer 94 for drying. The total mass of the nitro-substituted aniline after drying is 7.74 kg, and the yield is 99.4%.

[0103] Example 8

[0104] This embodiment provides a green nitration process, using the green nitration device provided in Example 4, wherein the methyl benzoic acid reaction unit is selected from a dynamic tubular reactor and a reactor connected in series, the substituted aniline nitration reaction unit 7 is selected from a microchannel reactor, the substitution reaction unit 91 is selected from a reactor, and the separation unit 92 is a solid-liquid separator, an oil-water separator and a two-stage washing separation two-in-one device connected in sequence.

[0105] Meta-methylbenzoic acid and 90% nitric acid enter the methylbenzoic acid nitration reaction unit 1 from the inlet of the dynamic tubular reactor at flow rates of 13.62g / min and 56.01g / min, respectively. The molar ratio of meta-methylbenzoic acid to nitric acid is 1:8, the reaction temperature is controlled to be -15°C, the reaction residence time is 20min, and after the reaction is stable, the first nitration reaction liquid is collected from the outlet of the reactor, and the collection is continuously collected for 20min. The conversion rate of methylbenzoic acid in the first nitration reaction liquid is 99.6%. The collected first nitration reaction liquid is separated into the first product and the first liquid phase by the first solid-liquid separator 2, and the separated first liquid phase enters the crystallization kettle 3, and 0.44kg of water is added for dilution. The diluted first liquid phase is separated into the first product and the second liquid phase by the second solid-liquid separator 4, and the second liquid phase enters the temporary storage tank 5 for temporary storage. At this time, the nitric acid concentration in the second liquid phase is 60%.

[0106] The substituted aniline solution and the second liquid phase with a nitric acid concentration of 60% in the temporary storage tank 5 enter the substituted aniline nitration reaction unit 7 from the inlet end of the microchannel reactor at flow rates of 70.3 g / min and 75.32 g / min, respectively. The mass ratio of substituted aniline to the second liquid phase is 1:3, the mass ratio of substituted aniline to dichloroethane in the substituted aniline solution is 1:1.8, the reaction temperature is controlled to be 73°C, the pressure of the reaction system is 0.2 MPa, the reaction residence time is 100 s, and the second liquid phase is fully involved in the nitration reaction of the substituted aniline to produce the second nitration reaction liquid entering The first oil-water separator 8 is used to separate the oil and water phases. The oil phase separated from the first oil-water separator 8 enters the alkali adjustment kettle 101, is adjusted to a pH value of 10 with sodium hydroxide solution, and is stirred and mixed for 2 hours before being transferred to the second oil-water separator 102 for oil-water separation. The water phase separated from the second oil-water separator 102 enters the acid adjustment kettle 111, is adjusted to a pH value of 1 with dilute nitric acid, and is stirred and mixed for 1.5 hours before being separated and recovered by the third solid-liquid separator 112 to obtain the first product. The total mass of the first product separated three times after drying is 3.59 kg, and the yield is 99.2%.

[0107] The oil phase separated from the second oil-water separator 102 is all fed into a reactor, and 61.17 g of aminosulfonic acid and 139.1 g of 31% hydrochloric acid are added simultaneously. A substitution reaction takes place at a reaction temperature of 100° C. until the nitrite content is less than 0.02%. The substitution reaction liquid is collected from the outlet of the reactor. The conversion rate of the substituted aniline in the reaction liquid is found to be 99.8%, and the selectivity of the product is 99.96%.

[0108] The above-mentioned substitution reaction liquid enters a solid-liquid separator, an oil-water separator and a two-stage washing and separation two-in-one device which are connected in sequence. The liquid phase obtained after solid-liquid separation is separated into water and oil phases by the oil-water separator. The obtained oil phase is washed with alkali and water and then enters a distillation kettle 93 to distill and recover the organic solvent dichloroethane. The heavy components in the distillation kettle 93 enter a dryer 94 for drying. The total mass of the nitro-substituted aniline after drying is 7.34 kg, and the yield is 99.4%.

[0109] Example 9

[0110] This embodiment provides a green nitration process, using the green nitration device provided in Example 4, wherein the methyl benzoic acid reaction unit is selected from a three-stage reactor connected in series, the substituted aniline nitration reaction unit 7 is selected from a two-stage microchannel reactor connected in series, the substitution reaction unit 91 is selected from a reactor, and the separation unit 92 is an oil-water separator and a two-stage washing and separation two-in-one device connected in sequence.

[0111] p-Toluic acid and 85% nitric acid enter the methyl benzoic acid nitration reaction unit 1 from the inlet of the three-stage series reactor at flow rates of 13.62g / min and 74.13g / min, respectively, wherein the molar ratio of p-toluic acid to nitric acid is 1:10, the reaction temperature is controlled to be -30°C, the reaction residence time is 30min, and after the reaction is stable, the first nitration reaction liquid is collected from the outlet of the three-stage series reactor, and the collection is continuously collected for 20min. The conversion rate of p-toluic acid in the first nitration reaction liquid is 99.6% after detection. The collected first nitration reaction liquid is separated into the first product and the first liquid phase by the first solid-liquid separator 2, and the separated first liquid phase enters the crystallization reactor 3, and 0.23kg of water is added for dilution. The diluted first liquid phase is separated into the first product and the second liquid phase by the second solid-liquid separator 4, and the second liquid phase enters the temporary storage tank 5 for temporary storage, and the nitric acid concentration in the second liquid phase is 70%.

[0112] The substituted aniline solution and the second liquid phase with a nitric acid concentration of 70% in the temporary storage tank 5 enter the substituted aniline nitration reaction unit 7 from the inlet end of the two-stage microchannel reactor connected in series at flow rates of 42.32 g / min and 84.64 g / min, respectively, wherein the mass ratio of the substituted aniline to the second liquid phase is 1:4, the mass ratio of the substituted aniline to the ethylene dichloride in the substituted aniline solution is 1:1, the reaction temperature is controlled to be 80°C, the pressure of the reaction system is 0.3 MPa, the reaction residence time is 10 s, and the second liquid phase fully participates in the second nitration reaction generated by the nitration reaction of the substituted aniline The liquid enters the first oil-water separator 8, and the oil and water phases are separated by the first oil-water separator 8. The oil phase separated from the first oil-water separator 8 enters the alkali adjustment kettle 101, and is adjusted to a pH value of 14 with sodium hydroxide solution. After stirring and mixing for 1 hour, it is transferred to the second oil-water separator 102 for oil-water separation. The water phase separated from the second oil-water separator 102 enters the acid adjustment kettle 111, and is adjusted to a pH value of 3 with dilute nitric acid. After stirring and mixing for 3 hours, it is separated and recovered by the third solid-liquid separator 112 to obtain the first product. The total mass of the first product separated three times is 3.59 kg after drying, and the yield is 99.0%.

[0113] The oil phase separated from the second oil-water separator 102 is all fed into a reactor, and 64.43 g of aminosulfonic acid and 156.3 g of 31% hydrochloric acid are added simultaneously. A substitution reaction takes place at a reaction temperature of 100° C. until the nitrite content is less than 0.02%. The substitution reaction liquid is collected from the outlet of the reactor. The conversion rate of the substituted aniline in the reaction liquid is found to be 99.6%, and the selectivity of the product is 99.96%.

[0114] The above-mentioned substitution reaction liquid enters an oil-water separator and a two-stage washing and separation two-in-one device which are connected in sequence. The oil phase obtained after oil-water separation is washed with alkali and water and then enters a distillation kettle 93 for distillation to recover the organic solvent dichloroethane. The heavy components in the distillation kettle 93 enter a dryer 94 for drying. The total mass of the nitro-substituted aniline after drying is 6.17 kg, and the yield is 99.2%.

[0115] Example 10

[0116] This embodiment provides a green nitration process, using the green nitration device provided in Example 4, wherein the methyl benzoic acid reaction unit is selected from a primary reactor, the substituted aniline nitration reaction unit 7 is selected from a microchannel reactor and a static tubular reactor connected in series, the substitution reaction unit 91 is selected from a reactor, and the separation unit 92 is an oil-water separator and a two-stage washing and separation two-in-one device connected in sequence.

[0117] 0.27 kg of o-toluic acid was added to the reactor, and 1.29 kg of 88% nitric acid was added dropwise while stirring, wherein the molar ratio of o-toluic acid to nitric acid was 1:9, the reaction temperature was controlled to be -20°C, and the o-toluic acid remained less than 0.2%. The first nitration reaction liquid was collected from the outlet of the reactor, and the conversion rate of o-toluic acid in the first nitration reaction liquid was 99.8% after detection. The collected first nitration reaction liquid was separated into the first product and the first liquid phase by the first solid-liquid separator 2, and the separated first liquid phase entered the crystallization kettle 3, and 0.35 kg of water was added for dilution. The diluted first liquid phase was separated into the first product and the second liquid phase by the second solid-liquid separator 4, and the second liquid phase entered the temporary storage tank 5 for temporary storage, and the nitric acid concentration in the second liquid phase was 65%.

[0118] The substituted aniline solution and the second liquid phase with a nitric acid concentration of 65% in the temporary storage tank 5 enter the substituted aniline nitration reaction unit 7 from the inlet ends of the microchannel reactor and the static tubular reactor connected in series at flow rates of 57.33 g / min and 80.27 g / min, respectively, wherein the mass ratio of the substituted aniline to the second liquid phase is 1:3.5, the mass ratio of the substituted aniline to dichloroethane in the substituted aniline solution is 1:1.5, the reaction temperature is controlled to be 77° C., the pressure of the reaction system is 0.25 MPa, the reaction residence time is 60 s, and the second liquid phase is fully involved in the nitration reaction of the substituted aniline to produce The second nitration reaction liquid enters the first oil-water separator 8, and the oil and water phases are separated by the first oil-water separator 8. The oil phase separated from the first oil-water separator 8 enters the alkali adjustment kettle 101, and is adjusted to a pH value of 12 with sodium hydroxide solution. After stirring and mixing for 1.5 hours, it is transferred to the second oil-water separator 102 for separation. The water phase separated from the second oil-water separator 102 enters the acid adjustment kettle 111, and is adjusted to a pH value of 2 with dilute nitric acid. After stirring and mixing for 2 hours, it is separated and recovered by the third solid-liquid separator 112 to obtain the first product. The total mass of the first product separated three times is 3.59 kg after drying, and the yield is 99.1%.

[0119] The oil phase separated from the second oil-water separator 102 is all fed into the reactor of the substitution reaction unit 91, and 62.85 g of aminosulfonic acid and 141.1 g of 31% hydrochloric acid are added at the same time. The substitution reaction takes place at a reaction temperature of 100° C. until the residual nitrite is less than 0.02%. The substitution reaction liquid is collected from the outlet of the reactor. The conversion rate of the substituted aniline in the reaction liquid is tested to be 99.6%, and the selectivity of the product is 99.97%.

[0120] The above-mentioned substitution reaction liquid enters an oil-water separator and a two-stage washing and separation two-in-one device which are connected in sequence. The oil phase obtained after oil-water separation is washed with alkali and water and then enters a distillation kettle 93 for distillation to recover the organic solvent dichloroethane. The heavy components in the distillation kettle 93 enter a dryer 94 for drying. The total mass of the nitro-substituted aniline after drying is 6.7 kg, and the yield is 99.3%.

[0121] The above description is only a specific embodiment of the present disclosure, so that those skilled in the art can understand or implement the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to the embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A green nitrification device, characterized in that: include: A methylbenzoic acid nitration reaction unit (1), a first solid-liquid separator (2), a crystallization kettle (3), a second solid-liquid separator (4), a temporary storage tank (5), a liquid feed pump (6), a substituted aniline nitration reaction unit (7), a first oil-water separator (8) and a product refining and separation unit (9); The discharge port of the methyl benzoic acid nitration reaction unit (1) is connected to the feed port of the first solid-liquid separator (2), the first liquid phase outlet of the first solid-liquid separator (2) is connected to the feed port of the crystallization kettle (3), the discharge port of the crystallization kettle (3) is connected to the feed port of the second solid-liquid separator (4), the second liquid phase outlet of the second solid-liquid separator (4) is connected to the feed port of the temporary storage tank (5), the discharge port of the temporary storage tank (5) is connected to the acid inlet of the substituted aniline nitration reaction unit (7) through a liquid feed pump (6), the discharge port of the substituted aniline nitration reaction unit (7) is connected to the feed port of the first oil-water separator (8), and the oil outlet of the first oil-water separator (8) is connected to the feed port of the product refining and separation unit (9); The methylbenzoic acid nitration reaction unit (1) is provided with a methylbenzoic acid inlet and a nitric acid inlet, the crystallization kettle (3) is also provided with a water inlet, and the substituted aniline nitration reaction unit (7) is also provided with a substituted aniline solution inlet.

2. A green nitrification device according to claim 1, characterized in that: The nitrification device further comprises an alkali adjustment unit (10), the oil outlet of the first oil-water separator (8) is connected to the feed inlet of the alkali adjustment unit (10), and the oil outlet of the alkali adjustment unit (10) is connected to the feed inlet of the product refining and separation unit (9).

3. A green nitrification device according to claim 2, characterized in that: The alkali adjustment unit (10) comprises an alkali adjustment kettle (101) and a second oil-water separator (102) which are connected in sequence.

4. A green nitrification device according to claim 2, characterized in that: The nitration device further comprises an acid adjustment unit (11), the water outlet of the alkali adjustment unit (10) is connected to the feed inlet of the acid adjustment unit (11), and the acid adjustment unit (11) comprises an acid adjustment kettle (111) and a third solid-liquid separator (112) which are connected in sequence.

5. A green nitrification device according to claim 1, characterized in that: The product refining and separation unit (9) comprises a substitution reaction unit (91), a separation unit (92), a distillation kettle (93), and a dryer (94); the separation unit (92) is an oil-water separator and a two-stage washing and separation two-in-one device connected in sequence, or a solid-liquid separator, an oil-water separator and a two-stage washing and separation two-in-one device connected in sequence, or an oil-water separator and a three-stage washing and separation two-in-one device connected in sequence, or a solid-liquid separator, an oil-water separator and a three-stage washing and separation two-in-one device connected in sequence.

6. A green nitration process, characterized in that: Using the nitrification device according to any one of claims 1 to 5, comprising the following steps: S1: methyl benzoic acid and nitric acid enter the methyl benzoic acid nitration reaction unit (1) to undergo nitration reaction to obtain a first nitration reaction liquid; S2: The first nitration reaction liquid enters the first solid-liquid separator (2) for separation to obtain a first product and a first liquid phase; S3: The first liquid phase enters the crystallization kettle (3) and is diluted with water for crystallization before being transferred to the second solid-liquid separator (4). After separation in the second solid-liquid separator (4), the first product and the second liquid phase are obtained. The second liquid phase enters the temporary storage tank (5) through a pipeline for temporary storage; S4: the substituted aniline solution and the second liquid phase enter the substituted aniline nitration reaction unit (7) to undergo nitration reaction to obtain a second nitration reaction solution; S5: The second nitration reaction liquid enters the first oil-water separator (8) for oil-water separation, and the separated oil phase enters the product refining and separation unit (9) for refining operation to obtain the second product nitro-substituted aniline.

7. A green nitration process according to claim 6, characterized in that: The concentration of nitric acid in step S1 is 85-98%, the molar ratio of methyl benzoic acid to nitric acid is 1:(5-10), the reaction temperature is -30-0°C, and the reaction time is 1-30 minutes. The concentration of nitric acid in the second liquid phase in step S3 is 40-70%, the reaction temperature in step S4 is 60-80°C, the pressure is 0.1-0.3 MPa, and the reaction time is 10-300 seconds. The substituted aniline solution is a mixed solution of substituted aniline and dichloroethane in a mass ratio of 1:(1-3), and the mass ratio of substituted aniline to the second liquid phase is 1:(2-4).

8. A green nitration process according to claim 6, characterized in that: The oil phase separated by the first oil-water separator (8) in step S5 first enters the alkali adjustment unit (10) before entering the product refining and separation unit (9), and is mixed with alkali solution to adjust the pH to 8-14. After mixing for 1-3 hours, the oil phase and the water phase are separated, and the separated oil phase enters the product refining and separation unit (9) to separate and obtain the product nitro-substituted aniline.

9. A green nitration process according to claim 8, characterized in that: The aqueous phase separated by the alkali adjustment unit (10) enters the acid adjustment unit (11), is mixed with dilute acid to adjust the pH to 0-3, and after mixing for 1-3 hours, the solid phase and the liquid phase are separated, and the separated solid phase is combined with the first product separated in step S2 and step S3 to form the first product.

10. A green nitration process according to claim 6, characterized in that: The refining operation in step S5 is to mix the oil phase separated by the first oil-water separator (8) with hydrochloric acid and aminosulfonic acid to undergo a substitution reaction, and the oil phase of the substitution reaction liquid after oil-water separation is washed, desolventized and dried.

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