Green nitration device and nitration process

Abstract

The present application provides a kind of green nitrification device and nitrification process, methylbenzoic acid and nitric acid occur nitration in methylbenzoic acid nitration reaction unit, the first nitration reaction liquid obtained is separated after first solid-liquid separator and obtains first product and first liquid phase, first liquid phase is diluted and crystallized after water and is separated in second solid-liquid separator and obtains first product and second liquid phase, second liquid phase is temporarily stored in temporary storage tank and enters substitution aniline nitration reaction unit and occurs nitration with substitution aniline solution, the second nitration reaction liquid obtained is refined by first oil-water separator, product refining separation unit and is refined, and second product nitro-substituted aniline is obtained.The waste nitric acid after methylbenzoic acid nitration reaction is directly used for the nitration of substitution aniline without refining and impurity removal treatment, realizes the comprehensive utilization of waste nitric acid, also avoids substitution aniline salification link, process is simple, reduces resource waste, reduces security risk, realizes green production.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a green nitration device and nitration process. Background Technology

[0002] Nitration products of methylbenzoic acid (hereinafter referred to as substituted benzoic acid) are important intermediates for pharmaceuticals and other fine chemicals. During the production process, methylbenzoic acid is generally nitrated with excess nitric acid, which generates a large amount of waste nitric acid. The existing technology for treating waste nitric acid usually involves concentrating the waste nitric acid and then reusing it in the nitration reaction. This method has high production costs and poses safety hazards.

[0003] N-(1-Ethylpropyl)-2,6-dinitro-3,4-dimethylaniline (abbreviated as nitro-substituted aniline) belongs to the dinitroaniline class of herbicides and is a selective soil-sealing herbicide widely used in cotton, corn, rice, potatoes, soybeans, peanuts, and tobacco. Current processes use N-(1-Ethylpropyl)-3,4-dimethylaniline (abbreviated as substituted aniline) as a raw material, first reacting it with dilute acid to form a salt, and then subjecting it to a nitration reaction with concentrated acid to prepare nitro-substituted aniline, resulting in high production costs.

[0004] Therefore, there is an urgent need to develop a nitration device and nitration process that can reuse waste acid from benzoic acid to prepare nitro-substituted aniline. This would not only improve the utilization rate of nitric acid and reduce production costs, but also simplify the preparation process of nitro-substituted aniline, thus fundamentally achieving green and environmentally friendly practices. Summary of the Invention

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

[0006] This invention provides a green nitration device, comprising: a methylbenzoic 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 outlet of the methylbenzoic acid nitration reaction unit is connected to the inlet of the first solid-liquid separator. The first liquid phase outlet of the first solid-liquid separator is connected to the inlet of the crystallization kettle. The outlet of the crystallization kettle is connected to the inlet of the second solid-liquid separator. The second liquid phase outlet of the second solid-liquid separator is connected to the inlet of the temporary storage tank. The outlet of the temporary storage tank is connected to the acid inlet of the substituted aniline nitration reaction unit via a liquid feed pump. The outlet of the substituted aniline nitration reaction unit is connected to the inlet of the first oil-water separator. The oil outlet of the first oil-water separator is connected to the inlet of the product refining and separation unit.

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

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

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

[0011] Preferably, the nitration device further includes an acid conditioning unit, the outlet of which is connected to the inlet of the acid conditioning unit, and the acid conditioning unit consists of an acid conditioning kettle and a third solid-liquid separator connected in sequence.

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

[0013] This invention provides a green nitration process using the nitration apparatus described above, comprising the following steps:

[0014] S1: Methylbenzoic acid and nitric acid enter the methylbenzoic acid nitration reaction unit to undergo a nitration reaction to obtain the first nitration reaction solution;

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

[0016] S3: The first liquid phase enters the crystallization kettle, is diluted with water and crystallized, and is then transferred to the second solid-liquid separator. After separation by 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 a nitration reaction to obtain the second nitration reaction solution;

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

[0019] Preferably, in step S1, the concentration of nitric acid is 85-98%, the molar ratio of methylbenzoic acid to nitric acid is 1:(5-10), the reaction temperature is -30-0℃, and the reaction time is 1-30 min; in step S3, the concentration of nitric acid in the second liquid phase is 40-70%; in step S4, the reaction temperature is 60-80℃, the pressure is 0.1-0.3 MPa, the reaction time is 10-300 s, and the substituted aniline solution is a mixture of substituted aniline and dichloroethane with 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, in step S5, the oil phase separated by the first oil-water separator first enters the alkali adjustment unit before entering the product refining and separation unit. It is mixed with alkali solution to adjust the pH to 8-14. After mixing for 1-3 hours, the oil phase and water phase are separated. The separated oil phase enters the product refining and separation unit to obtain the product nitro-substituted aniline.

[0021] Preferably, the aqueous phase separated in 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 liquid phase are separated. The separated solid phase is combined with the first product separated in steps S2 and S3 to form the first product.

[0022] Preferably, the refining operation in step S5 involves mixing the oil phase separated by the first oil-water separator with hydrochloric acid and aminosulfonic acid to undergo a substitution reaction, and then washing, desolvating, and drying the oil phase after oil-water separation of the substitution reaction solution.

[0023] This invention provides a green nitration device, comprising a methylbenzoic acid nitration reaction unit and a substituted aniline nitration reaction unit. The outlet of the methylbenzoic acid nitration reaction unit is connected to the inlet of a first solid-liquid separator. The first liquid phase outlet of the first solid-liquid separator is connected to the inlet of a crystallization vessel. The outlet of the crystallization vessel is connected to the inlet of a second solid-liquid separator. The second liquid phase outlet of the second solid-liquid separator is connected to the inlet of a temporary storage tank. The outlet of the temporary storage tank is connected to the acid inlet of the substituted aniline nitration reaction unit via a liquid feed pump. The outlet of the substituted aniline nitration reaction unit is connected to the inlet of a first oil-water separator. The oil outlet of the first oil-water separator is connected to the inlet 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 vessel is also provided with a water inlet. The substituted aniline nitration reaction unit is also provided with a substituted aniline solution inlet.

[0024] In this invention, the methylbenzoic acid nitration reaction unit is provided with at least one methylbenzoic acid inlet and at least one nitric acid inlet for inputting methylbenzoic acid and nitric acid, respectively, and at least one outlet for outputting the first nitration reaction liquid. Preferably, the methylbenzoic acid feeding device is a screw feeder for conveying solid methylbenzoic acid into the methylbenzoic acid nitration reaction unit, and the nitric acid feeding device is a diaphragm pump or a centrifugal pump. The methylbenzoic acid reaction unit is selected from at least one dynamic tubular reactor, reaction vessel, or a dynamic tubular reactor and reaction vessel connected in series, enabling continuous production.

[0025] Specifically, the methyl benzoic acid reaction unit is selected from at least one dynamic tubular reactor connected in series or parallel, or at least one reactor connected in series or parallel, or at least one dynamic tubular reactor and at least one reactor connected in series. It can be one dynamic tubular reactor, two dynamic tubular reactors connected in series, two reactors connected in parallel, three reactors connected in series, or one dynamic tubular reactor and one reactor connected in series. The dynamic tubular reactor is a tubular reactor with a stirring shaft. Mass transfer is promoted by the stirring shaft being driven by a motor, and heat exchange is achieved through an external jacket. The reactor is a stirred vessel with a jacketed heat exchange and an overflow port.

[0026] In this invention, the substituted aniline nitration reaction unit is provided with at least one acid inlet and at least one substituted aniline solution inlet for inputting the second liquid phase and the substituted aniline solution, respectively. It also has at least one outlet for outputting the second nitration reaction liquid. The substituted aniline nitration reaction unit is selected from a microchannel reactor or a series-connected microchannel reactor and tubular reactor, which can achieve both continuous production and a one-step reaction to improve production efficiency.

[0027] Specifically, the nitration reaction unit for substituted aniline can be a microchannel reactor, or a microchannel reactor and a tubular reactor connected in series. The tubular reactor is selected from dynamic tubular reactors or static tubular reactors. The microchannel reactor is a plate reactor with reaction channels and heat exchange channels. The static tubular reactor is a tubular reactor with internal turbulence fins and an external jacketed heat exchange.

[0028] In this invention, the first solid-liquid separator is provided with an inlet, a first liquid phase outlet and a first solid phase outlet. The inlet of the first solid-liquid separator is connected to the outlet of the methyl benzoic acid nitration reaction unit through a pipeline for solid-liquid separation of the first nitration reaction liquid. The separated first product, replacing benzoic acid, is discharged from the first solid phase outlet, and the separated first liquid phase is discharged through the first liquid phase outlet.

[0029] In this invention, the second solid-liquid separator is provided with a feed inlet, a second solid phase outlet, and a second liquid phase outlet. The feed inlet of the second solid-liquid separator is connected to the discharge outlet of the crystallization vessel through a pipe, and is used to perform solid-liquid separation on the material flowing out of the crystallization vessel. The separated first product, replacing benzoic acid, is discharged from the second solid phase outlet, and the separated second liquid phase is discharged from the second liquid phase outlet.

[0030] Specifically, the first solid-liquid separator and the second solid-liquid separator are both selected from one of the following: top-suspended centrifuge, horizontal scraper centrifuge, three-legged centrifuge, and plate and frame filter press, with the horizontal scraper centrifuge being preferred.

[0031] In this invention, the crystallization vessel is equipped with a feed inlet, a water inlet, and a discharge outlet. The feed inlet of the crystallization vessel is connected to the first liquid phase outlet of the first solid-liquid separator. The crystallization vessel consists of a vessel 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 vessel through the feed pipe. Water enters the crystallization vessel from the water inlet. The stirring motor drives the stirring shaft and the U-shaped stirring paddle to rotate, diluting the nitric acid in the first liquid phase with water, reducing the solubility of the nitric acid in the first product, and causing the first product to precipitate from the nitric acid to form a slurry.

[0032] In this invention, the temporary storage tanks are designed in multiple parallel configurations for temporarily storing the second liquid phase, and the structure of the temporary storage tanks is preferably vertical. A liquid feed pump is connected via a pipeline from the bottom outlet of the temporary storage tank to the acid inlet of the substituted aniline nitration reaction unit, and is used to pump the second liquid phase in the temporary storage tank into the substituted aniline nitration reaction unit. The liquid feed pump is selected from centrifugal pumps, diaphragm pumps, or rotary pumps, with diaphragm pumps being preferred.

[0033] In this invention, a first oil-water separator is provided with an inlet, an oil outlet, and a water outlet. The inlet of the first oil-water separator is connected to the outlet of the substituted aniline nitration reaction unit, and is used to separate the oil and water from the second nitration reaction liquid from the substituted aniline nitration reaction unit. The aqueous 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 this invention, the nitration apparatus further includes an alkali conditioning unit. The oil outlet of the first oil-water separator is connected to the feed inlet of the alkali conditioning unit, and the oil outlet of the alkali conditioning unit is connected to the feed inlet of the product refining and separation unit. The alkali conditioning unit consists of an alkali conditioning kettle and a second oil-water separator connected in sequence.

[0035] This invention utilizes the second liquid phase separated by the second solid-liquid separator for the nitration of substituted aniline. When the second liquid phase contains a small amount of substituted benzoic acid in addition to nitric acid, after the nitration reaction between the second liquid phase and the substituted aniline produces 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. To obtain high-quality nitro-substituted aniline, in a preferred embodiment of this invention, an alkali adjustment unit is added to remove the substituted benzoic acid from the nitro-substituted aniline. The alkali adjustment unit consists 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 with alkali solution. After alkali adjustment, the first product, substituted benzoic acid, is converted into substituted benzoate and dissolved in the aqueous phase, while the nitro-substituted aniline remains dissolved in the oil phase. The second oil-water separator separates the substituted benzoate and nitro-substituted aniline by separating the oil and water phases. The alkali preparation vessel is preferably a jacketed heat exchange vessel. 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. The alkali solution is selected from sodium hydroxide solution, sodium bicarbonate solution or sodium carbonate solution, preferably sodium hydroxide solution.

[0036] In this invention, the nitration apparatus further includes an acidification unit. The outlet of the alkali-conditioning unit is connected to the inlet of the acidification unit. The acidification unit consists of an acidification vessel and a third solid-liquid separator connected in series. If the aqueous phase containing substituted benzoate separated by the alkali-conditioning unit is directly treated as wastewater, it will result in the waste of the first product, substituted benzoic acid. To improve the yield of the first product, substituted benzoic acid, in a preferred embodiment of this invention, the substituted benzoate in the aqueous phase is converted into substituted benzoic acid by adding an acidification unit, thus recovering the first product, substituted benzoic acid. The acidification unit consists of an acidification vessel and a third solid-liquid separator connected in series. The acidification vessel is preferably a jacketed heat exchanger. Acid is added to acidify the aqueous phase separated by the second oil-water separator. During the acidification process, the substituted benzoate dissolved in the aqueous phase reacts with the acid to generate substituted benzoic acid, which precipitates from the aqueous phase. The third solid-liquid separator is used to separate the material from the acidification vessel. After separating the aqueous phase, the recovered first product is obtained. The third solid-liquid separator is selected from a top-suspended centrifuge, a horizontal scraper centrifuge, a three-legged centrifuge, or a plate and frame filter press, preferably a horizontal scraper centrifuge. The acid solution is selected from dilute nitric acid, dilute hydrochloric acid, or dilute sulfuric acid, preferably dilute nitric acid.

[0037] In this 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 a combination of an oil-water separator and a two-stage washing and separation device connected in sequence, or a combination of a solid-liquid separator, an oil-water separator, and a two-stage washing and separation device connected in sequence, or a combination of an oil-water separator and a three-stage washing and separation device connected in sequence, or a combination of a solid-liquid separator, an oil-water separator, and a three-stage washing and separation device connected in sequence.

[0038] In addition to the second product nitro-substituted aniline, the second nitration reaction liquid obtained from the substituted aniline nitration reaction unit also contains 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 to refine and separate the oil phase separated by the first oil-water separator. 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 to refine and separate the oil phase separated by the second oil-water separator.

[0039] In this invention, the substitution reaction unit is the site where nitrite impurities are converted into nitro-substituted aniline. It is equipped 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, and at least one oil phase inlet for inputting the oil phase separated by a first oil-water separator or a second oil-water separator. It also has at least one outlet for outputting the substitution reaction liquid. The substitution reaction unit is selected from a dynamic tubular reactor or a reaction vessel with an overflow outlet, preferably a dynamic tubular reactor.

[0040] In embodiments of the present invention, the separation unit can be a combined oil-water separator and a two-stage washing and separation device connected in sequence. First, the substitution reaction liquid from the substitution reaction unit undergoes oil-water separation to remove the aqueous phase. The oil phase containing the second product, nitro-substituted aniline, is then subjected to two-stage washing and separation to remove impurities. The two-stage washing and separation can be, in sequence, alkaline washing and water washing. Alternatively, the separation unit can be a combined solid-liquid separator, an oil-water separator, and a two-stage washing and separation device connected in sequence. First, the substitution reaction liquid from the substitution reaction unit undergoes solid-liquid separation to remove unreacted aminosulfonic acid. The separated liquid phase then undergoes oil-water separation to remove the aqueous phase. The oil phase containing the second product, nitro-substituted aniline, is then subjected to two-stage washing and separation to remove impurities. The two-stage washing and separation can be, in sequence, alkaline washing and water washing. The separation unit can also be a combined oil-water separator and a three-stage washing and separation device connected in sequence. First, the substitution reaction liquid from the substitution reaction unit is subjected to oil-water separation to remove the aqueous phase. The oil phase containing the second product nitro-substituted aniline is then subjected to three-stage washing and separation to remove impurities from the oil phase. The three-stage washing and separation can be water washing, alkali washing, and water washing in sequence. Alternatively, the separation unit can be a combined solid-liquid separator, an oil-water separator, and a three-stage washing and separation device connected in sequence. First, the substitution reaction liquid from the substitution reaction unit is subjected to solid-liquid separation to remove unreacted aminosulfonic acid. The separated liquid phase is then subjected to oil-water separation to remove the aqueous phase. The oil phase containing the second product nitro-substituted aniline is then subjected to three-stage washing and separation to remove impurities from the oil phase. The three-stage washing and separation can be water washing, alkali washing, and water washing in sequence. The combined washing and separation device integrates oil-water separation and washing functions. It is equipped with a feed inlet, a washing reagent inlet, an oil phase outlet, and a water phase outlet. The combined washing and separation device has at least two stages; a two-stage device is a two-stage device connected in series, and a three-stage device is a three-stage device connected in series. More complex series or parallel combinations are also within the scope of this invention.

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

[0042] In this invention, the substituted aniline solution is a mixture of substituted aniline and dichloroethane prepared in a specific mass ratio. The dichloroethane evaporated in the distillation vessel of the product refining and separation unit is cooled and recovered, and then pumped separately to a mixing vessel along with the substituted aniline and fresh dichloroethane to prepare the substituted aniline solution. The preparation process is automatically controlled, and the mixing vessel is preferably a jacketed stirred vessel.

[0043] This invention also provides a green nitration process using the green nitration apparatus described above, comprising the following steps:

[0044] S1: Methylbenzoic acid and nitric acid enter the methylbenzoic acid nitration reaction unit to undergo a nitration reaction and obtain the first nitration reaction solution.

[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, then transferred to the second solid-liquid separator. After separation by 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.

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

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

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

[0050] This invention has discovered that the waste nitric acid obtained after separating the substituted benzoic acid product from the first nitration reaction solution 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 involves first forming a salt with dilute nitric acid and then nitrifying with concentrated nitric acid. However, the waste nitric acid produced after the nitration reaction of methyl benzoic acid and nitric acid can be directly used for the nitration reaction of substituted aniline without purification and impurity removal. This not only achieves efficient utilization of waste nitric acid but also does not affect the quality of the second product, nitro-substituted aniline. By using the one-step nitration method of waste nitric acid produced after the nitration reaction of methyl benzoic acid and nitric acid with substituted aniline, nitro-substituted aniline can be successfully produced. This avoids the equipment investment for waste nitric acid concentration and recovery, as well as the safety hazards of the concentration process, and achieves comprehensive utilization of nitric acid.

[0051] Toluene benzoic acid, a solid material, is conveyed to the nitration reaction unit via a screw feeder. Simultaneously, nitric acid is pumped into the nitration reaction unit via a liquid feed pump to react with the methylbenzoic acid, yielding a first nitration reaction solution containing the first product, substituted benzoic acid. In this solution, part of the first product precipitates as a solid, while the rest dissolves in the nitric acid. The first nitration reaction solution is then separated in a first solid-liquid separator to obtain a solid phase of the first product and a first liquid phase, primarily composed of nitric acid and substituted benzoic acid. The first liquid phase is added to a crystallization reactor and diluted with water to precipitate the first product, substituted benzoic acid. The crystallized material is then transferred to a second solid-liquid separator via a transfer pump. After separation in the second separator, the first product and a second liquid phase are obtained. The second liquid phase, primarily composed of nitric acid, is then piped into a temporary storage tank for later use in 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 a nitration reaction to obtain a second nitration reaction solution containing the second product, nitro-substituted aniline. Due to the participation of the solvent dichloroethane, the second nitration reaction solution presents an oil-water two-phase mixture, with the second product dissolved in the oil phase. The second nitration reaction solution enters the first oil-water separator for oil-water separation. 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 found that in step S1, the higher the concentration of nitric acid used for nitrifying methylbenzoic acid, the stronger the activity of the nitration reaction and the faster the nitration rate, but this may lead to an increase in by-products. Conversely, the lower the concentration of nitric acid, the weaker the activity of the nitration reaction and the slower the nitration rate. As a preferred option, the concentration of nitric acid is 85-98%, more preferably 88-95%, and even more preferably 90-93%. Since water is generated during the reaction of methylbenzoic acid and nitric acid, in order to avoid an excessive drop in the concentration of nitric acid and to ensure the conversion rate of methylbenzoic acid, as a preferred option, the molar ratio of methylbenzoic acid to nitric acid is 1:(5-10), more preferably 1:(6-9), and even more preferably 1:(7-8).

[0053] In step S1, when the concentration of nitric acid and the molar ratio of methylbenzoic acid to nitric acid are determined, a higher reaction temperature results in a shorter reaction time and higher production efficiency. However, excessively high temperatures lead to increased byproducts, making the reaction difficult to control and increasing safety risks. Conversely, a lower reaction temperature results in a longer reaction time. To improve product quality and ensure production efficiency, as a preferred option, this 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 the first product, substituted benzoic acid, is dissolved in the first liquid phase, this invention reduces the solubility of the first product in nitric acid by lowering the nitric acid concentration, thereby causing the first product to precipitate in the first liquid phase. After diluting the first liquid phase, the lower the nitric acid concentration, the lower the solubility of the first product in nitric acid, and the more of the first product originally dissolved in the first liquid phase precipitates. After separation, the amount of the first product remaining in the second liquid phase is less, and the impact on the quality of the second product, nitro-substituted aniline, is smaller. However, if the concentration of nitric acid is too low after dilution, it will reduce the reaction rate between the substituted aniline and nitric acid. In order to precipitate the first product as much as possible without affecting the nitration reaction between the second liquid phase and the substituted aniline in step S4, this 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 mixture of substituted aniline and dichloroethane. A higher mass ratio of substituted aniline to dichloroethane means less dichloroethane is used, a higher concentration of the substituted aniline solution, a higher reaction rate, and lower energy consumption for solvent recovery. However, heat is more likely to accumulate in the reaction system, and untimely heat exchange may lead to local overheating or runaway reaction. Conversely, a lower mass ratio of substituted aniline to dichloroethane means more dichloroethane is used, a lower concentration of the substituted aniline solution, and easier control of the reaction temperature. However, the cost of solvent recovery is higher. In this invention, the preferred mass ratio of substituted aniline to dichloroethane is 1:(1-3), more preferably 1:(1.5-2).

[0056] In step S4, the substituted aniline solution and the second liquid phase enter the substituted aniline nitration reaction unit simultaneously, where a nitration reaction occurs to obtain the second nitration reaction solution. A higher mass ratio of substituted aniline to the second liquid phase indicates a smaller amount of the second liquid phase (i.e., a smaller amount of nitric acid), resulting in a lower conversion rate of substituted aniline and a lower product yield. Conversely, a lower mass ratio of substituted aniline to the second liquid phase indicates a larger amount of the second liquid phase (i.e., a larger amount of nitric acid), leading to a more complete nitration reaction and a higher product yield. However, using excessive nitric acid results in nitric acid waste. To ensure the yield of the second product and fully utilize the waste nitric acid generated during the production of substituted benzoic acid, thus reducing resource waste, the mass ratio of substituted aniline to the second liquid phase in the nitration device controlled by this invention is 1:(2-4). A preferred embodiment is a mass ratio of substituted aniline to the second liquid phase of 1:(2-3).

[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℃, the pressure is 0.1-0.3MPa, and the reaction time is 10-300s. The pressure setting can promote the reaction rate of substituted aniline with the second liquid phase. More preferably, the reaction temperature is 65-70℃, the pressure is 0.2-0.25MPa, and the reaction time is 100-200s.

[0058] The second nitration reaction solution obtained in step S4 contains nitro-substituted aniline, N-(1-ethylpropyl)-N-nitroso-3,4-dimethyl-2,6-dinitroaniline (hereinafter referred to as nitroso), dichloroethane, nitric acid, and water. Both the nitro-substituted aniline and nitroso are dissolved in dichloroethane. In step S5, the second nitration reaction solution 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 dichloroethane is obtained. This oil phase enters the product refining and separation unit for refining to obtain the second product, nitro-substituted aniline.

[0059] Because the byproduct nitrite is highly toxic and can induce mutagenesis, the oil phase separated by the first oil-water separator is purified to convert nitrite into nitro-substituted aniline. The oil phase separated by the first oil-water separator, along with hydrochloric acid and aminosulfonic acid, enters the substitution reaction unit simultaneously. The nitrite mixes with the hydrochloric acid and aminosulfonic acid to undergo a substitution reaction, generating a substitution reaction solution containing nitro-substituted aniline. The substitution reaction solution presents two phases: an oil phase containing nitro-substituted aniline dissolved in dichloroethane, and an aqueous phase containing hydrochloric acid and aminosulfonic acid dissolved in water. When aminosulfonic acid is in excess, the substitution reaction solution presents three phases: a solid phase, an oil phase, and an aqueous phase. The solid phase contains unreacted aminosulfonic acid. The substitution reaction solution is separated in the separation unit, and the oil phase is collected and then washed. This can be done by sequential alkali washing followed by water washing, or sequential water washing followed by alkali washing and water washing. Alkali washing can use sodium hydroxide solution or sodium carbonate solution. After washing, the 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] 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 enters the alkali adjustment unit before entering the product refining and separation unit. In the alkali adjustment unit, the oil phase is mixed with alkali solution to adjust the pH to 8-14, and the mixing time is 1-3 hours. At this time, the substituted benzoic acid in the oil phase reacts with the alkali solution to form substituted benzoate, which dissolves in the aqueous phase, while the nitro-substituted aniline remains dissolved in the oil phase. The oil phase and aqueous phase are separated by the second oil-water separator in the alkali adjustment unit, thereby separating the substituted benzoic acid from the nitro-substituted aniline. The separated oil phase enters the product refining and separation unit to perform the operation in 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. To reduce alkali consumption 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] To improve the yield of the first product, substituted benzoic acid, in a preferred embodiment of the present invention, the aqueous phase separated by the second oil-water separator in the alkali adjustment unit enters the acid adjustment unit. In the acid adjustment vessel, it is mixed with dilute acid 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 acid-adjusted material enters the third solid-liquid separator in the acid adjustment unit to separate the solid and liquid phases. The separated solid phase is the recovered first product, which is combined with the first products separated in steps S2 and 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 1.5-2 hours.

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

[0063] (1) This invention uses the waste nitric acid after the nitration of methyl benzoic acid directly for the nitration reaction of aniline without purification and impurity removal. This eliminates the treatment method of waste nitric acid salt formation or concentration, 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. Furthermore, it avoids the high energy consumption and safety hazards of concentration, realizes the comprehensive utilization of waste nitric acid, obtains qualified nitro-substituted aniline, reduces the equipment investment for waste nitric acid treatment, lowers 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 to directly nitrate substituted aniline to produce nitro-substituted aniline in one step, avoiding the steps of salt formation, separation of salt formation reaction liquid, recovery of dilute nitric acid and extraction of aniline salt in dilute nitric acid. The process is simple, easy to operate, has a high conversion rate, reduces resource waste and lowers safety hazards. Attached Figure Description

[0065] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0066] Figure 1 This is a schematic diagram of the nitration apparatus for nitro-substituted aniline used in Embodiment 1 of the present invention;

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

[0068] Figure 3 This is a schematic diagram of the nitration apparatus for nitro-substituted aniline used in Embodiment 3 of the present invention;

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

[0070] Explanation of reference numerals in the attached figures:

[0071] A-Methylbenzoic acid nitration unit, 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 and separation unit, 91-Substitution reaction unit, 92-Separation unit, 93-Distillation kettle, 94-Dryer, 10-Alkali conditioning unit, 101-Alkali conditioning kettle, 102-Second oil-water separator, 11-Acid conditioning unit, 111-Acid conditioning kettle, 112-Third solid-liquid separator. Detailed Implementation

[0072] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0073] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product identical or similar to the present invention derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art falls within the protection scope of the present invention. Unless otherwise expressly specified or limited, the connection method between units or devices should be interpreted broadly. For example, it can be a direct pipeline connection, or a pipeline connection through conventional conveying, metering, control, and temporary storage equipment such as pumping equipment, metering equipment, valves, fittings, and intermediate tanks; it can be a fixed connection or a detachable connection. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0074] In this invention, the various components of the production apparatus, such as dynamic tubular reactor, tubular reactor, microchannel reactor, solid-liquid separator, reaction vessel, temporary storage tank, oil-water separator, washing and separation combined equipment, distillation vessel, dryer, etc., can all be purchased from the market, but the entire apparatus cannot be purchased from the market and is not known to those skilled in the art.

[0075] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0076] Example 1

[0077] This embodiment provides a green nitration device, the structural schematic diagram of which is shown below. Figure 1 As shown, it includes a methylbenzoic acid nitration unit 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 methylbenzoic acid nitration unit A consists of a methylbenzoic 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 methylbenzoic acid nitration unit A, the inlet of the methylbenzoic acid nitration unit A is the inlet of the methylbenzoic acid nitration reaction unit 1. The outlet of the methylbenzoic acid nitration reaction unit 1 is connected to the inlet of the first solid-liquid separator 2. The first liquid phase outlet of the first solid-liquid separator 2 is connected to the inlet of the crystallization vessel 3. The crystallization vessel 3 is also equipped with a water inlet. The outlet of the crystallization vessel 3 is connected to the inlet of the second solid-liquid separator 4. The second liquid phase outlet of the second solid-liquid separator 4 is connected to the temporary storage... The inlet of tank 5 is connected to the outlet of the temporary storage tank 5. The outlet of the methyl benzoic acid nitration unit A is connected to the acid inlet of the substituted aniline nitration reaction unit 7 through the liquid feed pump 6. The substituted aniline nitration reaction unit 7 is also provided with a substituted aniline solution inlet. The outlet of the substituted aniline nitration reaction unit 7 is connected to the inlet of the first oil-water separator 8. The oil outlet of the first oil-water separator 8 is connected to the inlet of the product refining and separation unit 9.

[0079] Example 2

[0080] This embodiment provides a green nitration device, the structural schematic diagram of which is shown below. Figure 1 and Figure 2 As shown in the diagram, the structural schematic of the product refining and separation unit 9 is as follows: Figure 2 As shown, the product refining and separation unit 9 consists of a substitution reaction unit 91, a separation unit 92, a distillation kettle 93, and a dryer 94.

[0081] Based on Example 1, the inlet of the product refining and separation unit 9 is the oil phase inlet of the replacement reaction unit 91. The replacement reaction unit 91 is also provided with a hydrochloric acid inlet and an aminosulfonic acid inlet. The outlet of the replacement reaction unit 91 is connected to the inlet of the separation unit 92. The outlet of the separation unit 92 is connected to the inlet of the distillation kettle 93. The outlet of the distillation kettle 93 is connected to the inlet of the dryer 94. The outlet of the dryer 94 is the outlet of the product refining and separation unit 9.

[0082] Example 3

[0083] This embodiment provides a green nitration device, the structural schematic diagram of which is shown below. Figure 3 As shown, the difference from Embodiment 2 is that this embodiment also includes an alkali adjustment unit 10, which consists of an alkali adjustment kettle 101 and a second oil-water separator 102.

[0084] Based on Example 2, the oil outlet of the first oil-water separator 8 is connected to the feed inlet of the alkali adjustment vessel 101, the discharge outlet of the alkali adjustment vessel 101 is connected to the feed inlet of the second oil-water separator 102, and the oil outlet of the second oil-water separator 102 is connected to the feed inlet of the product refining and separation unit 9.

[0085] Example 4

[0086] This embodiment provides a green nitration device, the structural schematic diagram of which is shown below. Figure 4 As shown, the difference from Embodiment 3 is that this embodiment also includes an acid-adjusting unit 11, which consists of an acid-adjusting kettle 111 and a third solid-liquid separator 112.

[0087] Based on Example 3, the outlet of the second oil-water separator 102 is connected to the inlet of the acid-adjusting vessel 111, and the outlet of the acid-adjusting vessel 111 is connected to the inlet 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. The methylbenzoic 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 combined device connected in sequence.

[0090] m-Toluic acid and 98% nitric acid were introduced into the methylbenzoic acid nitration reaction unit 1 from the inlet of a two-stage series dynamic tubular reactor at flow rates of 13.62 g / min and 32.15 g / min, respectively. The molar ratio of m-methylbenzoic acid to nitric acid was 1:5. The reaction temperature was controlled at 0℃, and the reaction residence time was 1 min. After the reaction stabilized, the first nitration reaction liquid was collected from the outlet of the two-stage series dynamic tubular reactor. The collection was continued for 20 min, and the conversion rate of m-methylbenzoic acid in the first nitration reaction liquid was tested to be 99.7%. The collected first nitration reaction liquid was separated into the first product and the first liquid phase by the first solid-liquid separator 2. The separated first liquid phase entered the crystallization kettle 3 and was diluted with 0.71 kg of water. The diluted first liquid phase was separated into the first product and the second liquid phase by the second solid-liquid separator 4. The second liquid phase was temporarily stored in the temporary storage tank 5. At this time, the nitric acid concentration in the second liquid phase was 40%. The first product separated twice was collected, dried, and the total mass of benzoic acid replaced was 3.55 kg, with a yield of 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 dichloroethane in the substituted aniline solution is 1:3. The reaction temperature is controlled at 60℃, the reaction system pressure is 0.1 MPa, and the reaction residence time is 300 s. The second nitration reaction liquid, generated from the complete participation of the second liquid phase in the nitration reaction of the substituted aniline, 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. The oil phase separated from the first oil-water separator 8 directly enters the dynamic tubular reactor. Simultaneously, aminosulfonic acid and 31% hydrochloric acid enter the device from the inlet end of the dynamic tubular reactor at flow rates of 2.41 g / min and 5.85 g / min, respectively, to undergo a substitution reaction. The reaction temperature is 100℃, and the reaction continues until the nitrite content is below 0.02%. The substitution reaction liquid is collected from the outlet end of the dynamic tubular reactor. All the oil phase separated by the first oil-water separator 8 participates in the substitution reaction. The conversion rate of substituted aniline in the reaction liquid is detected to be 99.6%, and the product selectivity is 99.96%. The collected substitution reaction liquid enters a combined oil-water separator and a two-stage washing and separation device connected in sequence. The oil phase obtained after oil-water separation is washed with alkali and water, and then enters the distillation kettle 93 for distillation to recover the organic solvent dichloroethane. The heavy components in the distillation kettle 93 enter the dryer 94 for drying. The total mass of the dried nitro-substituted aniline is 9.25 kg, with a yield of 99.3%.

[0092] Example 6

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

[0094] p-Toluic acid and 93% nitric acid were introduced into the methylbenzoic acid nitration reaction unit 1 from the inlet of the primary dynamic tubular reactor at flow rates of 13.62 g / min and 47.43 g / min, respectively. The molar ratio of p-methylbenzoic acid to nitric acid was 1:7. The reaction temperature was controlled at -10℃, and the reaction residence time was 15 min. After the reaction stabilized, the first nitration reaction liquid was collected from the outlet of the primary dynamic tubular reactor and collected continuously for 20 min. The conversion rate of p-methylbenzoic acid in the first nitration reaction liquid was detected to be 99.8%. The collected first nitration reaction liquid was separated into the first product and the first liquid phase by the first solid-liquid separator 2. The separated first liquid phase entered the crystallization kettle 3 and was diluted with 0.52 kg of water. The diluted first liquid phase was separated into the first product and the second liquid phase by the second solid-liquid separator 4. The second liquid phase was temporarily stored in the temporary storage tank 5. At this time, the nitric acid concentration in the second liquid phase was 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 series-connected two-stage microchannel reactor at flow rates of 77.38 g / min and 69.64 g / min, respectively. The mass ratio of substituted aniline to the second liquid phase is 1:2.7, and the mass ratio of substituted aniline to dichloroethane in the substituted aniline solution is 1:2. The reaction temperature is controlled at 70℃, the reaction system pressure is 0.17 MPa, and the reaction residence time is 150 s. The second liquid phase participates entirely in the nitration reaction of the substituted aniline, producing a second nitration. The reaction solution enters the first oil-water separator 8, where the oil and water phases are separated. The oil phase separated from the first oil-water separator 8 enters the alkali adjustment tank 101, where the pH is adjusted to 9 with sodium hydroxide solution. After stirring and mixing for 2.5 hours, it is transferred to the second oil-water separator 102 for further oil-water separation. The aqueous phase separated from the second oil-water separator 102 enters the acid adjustment tank 111, where the pH is adjusted to 0 with dilute nitric acid. After stirring and mixing for 1 hour, it is separated by the third solid-liquid separator 112 to obtain the recovered first product. The total mass of the first product after the three separations is collected, dried, and the yield is 3.6 kg, with a yield of 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. At the same time, 54.98g of aminosulfonic acid and 127g of 31% hydrochloric acid are added. The substitution reaction takes place at a reaction temperature of 100℃ until the nitrite content is below 0.02%. The substitution reaction liquid is collected from the outlet of the reactor. The conversion rate of substituted aniline in the reaction liquid is 99.9%, and the selectivity of the product is 99.98%.

[0097] The above-mentioned substitution reaction solution enters a solid-liquid separator, an oil-water separator, and a three-stage washing and separation combined device 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, alkali, and water again before entering the distillation kettle 93 for distillation to recover the organic solvent dichloroethane. The heavy components in the distillation kettle 93 are dried by the dryer 94. The total mass of the dried nitro-substituted aniline is 7.55 kg, with a yield of 99.5%.

[0098] Example 7

[0099] This embodiment provides a green nitration process, using the green nitration device provided in Example 3. The methyl benzoic acid reaction unit is selected from a single-stage 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 reaction vessel, and the separation unit 92 is an oil-water separator and a three-stage washing and separation combined device connected in sequence.

[0100] o-Toluic acid and 95% nitric acid were introduced into the methylbenzoic acid nitration reaction unit 1 from the inlet of the primary dynamic tubular reactor at flow rates of 13.62 g / min and 39.8 g / min, respectively. The molar ratio of o-methylbenzoic acid to nitric acid was 1:6. The reaction temperature was controlled at -5℃, and the reaction residence time was 10 min. After the reaction stabilized, the first nitration reaction liquid was collected from the outlet of the primary dynamic tubular reactor and collected continuously for 20 min. The conversion rate of o-methylbenzoic acid in the first nitration reaction liquid was measured to be 99.6%. The collected first nitration reaction liquid was separated into the first product and the first liquid phase by the first solid-liquid separator 2. The separated first liquid phase entered the crystallization kettle 3 and was diluted with 0.55 kg of water. The diluted first liquid phase was then separated into the first product and the second liquid phase by the second solid-liquid separator 4. The second liquid phase was temporarily stored in the temporary storage tank 5. At this time, the nitric acid concentration in the second liquid phase was 50%. The total mass of the first product after the two separations was collected, dried, and the yield was 3.51 kg, with a yield of 97%.

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

[0102] The above-mentioned substitution reaction solution enters a combined oil-water separator and a three-stage washing and separation device connected in sequence. After oil-water separation, the oil phase obtained is washed with water, alkali, and then washed with water again before entering 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 dried nitro-substituted aniline is 7.74 kg, with a yield of 99.4%.

[0103] Example 8

[0104] This embodiment provides a green nitration process, using the green nitration device provided in Example 4. The methyl benzoic acid reaction unit is selected from a dynamic tubular reactor and a reaction vessel 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 reaction vessel, and the separation unit 92 is a solid-liquid separator, an oil-water separator, and a two-stage washing and separation combined device connected in sequence.

[0105] m-Toluic acid and 90% nitric acid were introduced into the methylbenzoic acid nitration reaction unit 1 from the inlet of the dynamic tubular reactor at flow rates of 13.62 g / min and 56.01 g / min, respectively. The molar ratio of m-methylbenzoic acid to nitric acid was 1:8. The reaction temperature was controlled at -15℃, and the reaction residence time was 20 min. After the reaction stabilized, the first nitration reaction liquid was collected from the outlet of the reactor and collected continuously for 20 min. The conversion rate of m-methylbenzoic acid in the first nitration reaction liquid was tested to be 99.6%. The collected first nitration reaction liquid was separated into the first product and the first liquid phase by the first solid-liquid separator 2. The separated first liquid phase entered the crystallization kettle 3 and was diluted with 0.44 kg of water. The diluted first liquid phase was separated into the first product and the second liquid phase by the second solid-liquid separator 4. The second liquid phase was temporarily stored in the temporary storage tank 5. At this time, the nitric acid concentration in the second liquid phase was 60%.

[0106] The substituted aniline solution and the second liquid phase with a nitric acid concentration of 60% in the temporary storage tank 5 are introduced into 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, and the mass ratio of substituted aniline to dichloroethane in the substituted aniline solution is 1:1.8. The reaction temperature is controlled at 73℃, the reaction system pressure is 0.2 MPa, and the reaction residence time is 100 s. The second nitration reaction liquid produced by the complete participation of the second liquid phase in the nitration reaction of the substituted aniline enters... The first oil-water separator 8 separates the oil and water phases. The oil phase separated from the first oil-water separator 8 enters the alkali adjustment tank 101, where the pH value is adjusted to 10 with sodium hydroxide solution. After stirring and mixing for 2 hours, it is transferred to the second oil-water separator 102 for further oil-water separation. The water phase separated from the second oil-water separator 102 enters the acid adjustment tank 111, where the pH value is adjusted to 1 with dilute nitric acid. After stirring and mixing for 1.5 hours, it is separated by the third solid-liquid separator 112 to obtain the recovered first product. The total mass of the first product after the three separations is collected, dried, and is 3.59 kg, with a yield of 99.2%.

[0107] All the oil phase separated from the second oil-water separator 102 enters the reactor, and 61.17g of aminosulfonic acid and 139.1g of 31% hydrochloric acid are added at the same time. The substitution reaction occurs at a reaction temperature of 100℃ until the nitrite content is below 0.02%. The substitution reaction liquid is collected from the outlet of the reactor. The conversion rate of substituted aniline in the reaction liquid is 99.8%, and the product selectivity is 99.96%.

[0108] The above-mentioned substitution reaction solution enters a solid-liquid separator, an oil-water separator, and a two-stage washing and separation combined device 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 the distillation kettle 93 for distillation to recover the organic solvent dichloroethane. The heavy components in the distillation kettle 93 enter the dryer 94 for drying. The total mass of the dried nitro-substituted aniline is 7.34 kg, with a yield of 99.4%.

[0109] Example 9

[0110] This embodiment provides a green nitration process, using the green nitration device provided in Example 4. 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 combined device connected in series.

[0111] p-Toluic acid and 85% nitric acid were introduced into the methylbenzoic acid nitration reaction unit 1 from the inlet of a three-stage series reactor at flow rates of 13.62 g / min and 74.13 g / min, respectively. The molar ratio of p-methylbenzoic acid to nitric acid was 1:10. The reaction temperature was controlled at -30℃, and the reaction residence time was 30 min. After the reaction stabilized, the first nitration reaction liquid was collected from the outlet of the three-stage series reactor for 20 min. The conversion rate of p-methylbenzoic acid in the first nitration reaction liquid was measured to be 99.6%. The collected first nitration reaction liquid was separated into the first product and the first liquid phase by the first solid-liquid separator 2. The separated first liquid phase entered the crystallization kettle 3 and was diluted with 0.23 kg of water. The diluted first liquid phase was then separated into the first product and the second liquid phase by the second solid-liquid separator 4. The second liquid phase was temporarily stored in the temporary storage tank 5, at which time the nitric acid concentration in the second liquid phase was 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 series-connected two-stage microchannel reactor at flow rates of 42.32 g / min and 84.64 g / min, respectively. The mass ratio of substituted aniline to the second liquid phase is 1:4, and the mass ratio of substituted aniline to dichloroethane in the substituted aniline solution is 1:1. The reaction temperature is controlled at 80℃, the reaction system pressure is 0.3 MPa, and the reaction residence time is 10 s. The second liquid phase participates entirely in the nitration reaction of the substituted aniline, generating a second nitration reaction. The liquid enters the first oil-water separator 8, where the oil and water phases are separated. The oil phase separated from the first oil-water separator 8 enters the alkali adjustment tank 101, where the pH value is adjusted to 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 tank 111, where the pH value is adjusted to 3 with dilute nitric acid. After stirring and mixing for 3 hours, it is separated by the third solid-liquid separator 112 to obtain the recovered first product. The total mass of the first product after the three separations is collected, dried, and the yield is 3.59 kg, with a recovery rate of 99.0%.

[0113] All the oil phase separated from the second oil-water separator 102 enters the reactor, and 64.43g of aminosulfonic acid and 156.3g of 31% hydrochloric acid are added at the same time. The substitution reaction occurs at a reaction temperature of 100℃ until the nitrite content is below 0.02%. The substitution reaction liquid is collected from the outlet of the reactor. The conversion rate of substituted aniline in the reaction liquid is 99.6%, and the product selectivity is 99.96%.

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

[0115] Example 10

[0116] This embodiment provides a green nitration process, using the green nitration device provided in Example 4. 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 combined 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. The molar ratio of o-toluic acid to nitric acid was 1:9. The reaction temperature was controlled at -20℃, and the reaction was continued until the remaining o-toluic acid was less than 0.2%. The first nitration reaction liquid was collected from the outlet of the reactor. The conversion rate of o-toluic acid in the first nitration reaction liquid was tested and found to be 99.8%. The collected first nitration reaction liquid was separated into the first product and the first liquid phase by the first solid-liquid separator 2. The separated first liquid phase entered the crystallization reactor 3, where 0.35 kg of water was added for dilution. The diluted first liquid phase was then separated into the first product and the second liquid phase by the second solid-liquid separator 4. The second liquid phase was temporarily stored in the temporary storage tank 5, at which time the concentration of nitric acid 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 are introduced into the substituted aniline nitration reaction unit 7 from the inlet ends of the microchannel reactor and the static tubular reactor connected in series, respectively, at flow rates of 57.33 g / min and 80.27 g / min. The mass ratio of substituted aniline to the second liquid phase is 1:3.5, and the mass ratio of substituted aniline to dichloroethane in the substituted aniline solution is 1:1.5. The reaction temperature is controlled at 77℃, the reaction system pressure is 0.25 MPa, and the reaction residence time is 60 s. All of the second liquid phase participates in the nitration reaction of the substituted aniline. The second nitration reaction liquid enters the first oil-water separator 8, where the oil and water phases are separated. The oil phase separated from the first oil-water separator 8 enters the alkali adjustment tank 101, where the pH value is adjusted to 12 with sodium hydroxide solution. After stirring and mixing for 1.5 hours, it is transferred to the second oil-water separator 102 for further separation. The aqueous phase separated from the second oil-water separator 102 enters the acid adjustment tank 111, where the pH value is adjusted to 2 with dilute nitric acid. After stirring and mixing for 2 hours, it is separated by the third solid-liquid separator 112 to obtain the recovered first product. The total mass of the first product after the three separations is collected, dried, and the yield is 3.59 kg, with a yield of 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. At the same time, 62.85g of aminosulfonic acid and 141.1g of 31% hydrochloric acid are added. The substitution reaction takes place at a reaction temperature of 100℃ 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 substituted aniline in the reaction liquid is 99.6%, and the selectivity of the product is 99.97%.

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

[0121] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily 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 this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

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

2. The green nitration device according to claim 1, characterized in that, The nitration device also includes an alkali conditioning unit (10), the oil outlet of the first oil-water separator (8) is connected to the feed inlet of the alkali conditioning unit (10), and the oil outlet of the alkali conditioning unit (10) is connected to the feed inlet of the product refining and separation unit (9).

3. The green nitration device according to claim 2, characterized in that, The alkali adjustment unit (10) consists of an alkali adjustment kettle (101) and a second oil-water separator (102) connected in sequence.

4. A green nitration device according to claim 2, characterized in that, The nitration device also includes an acid conditioning unit (11), the outlet of the alkali conditioning unit (10) is connected to the inlet of the acid conditioning unit (11), and the acid conditioning unit (11) consists of an acid conditioning kettle (111) and a third solid-liquid separator (112) connected in sequence.

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

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

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

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

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

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

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