52 results about "Nitrobenzoic acid" patented technology

A curcumin nanococrystal composition including curcumin, a coformer, and a stabilizer. The coformer may include at least one of 3,5-dinitrobenzoicacid, gentisic acid, phloroglucinol, 4,4-bipyridine, tartaric acid, citric acid, and gallic acid. The curcumin nanococrystal composition has a particle size less than 10 nm, and the curcumin has a water-solubility between 5 mg / ml and 20 mg / ml.

This invention provides a method for preparing and applying a highly insecticidal diamide compound, relating to the chemical and pesticide fields. The method includes: reacting 2-fluoro-3-nitrobenzoic acid with thionyl chloride (a chlorinating agent) and dimethylformamide (a catalyst) to obtain compound A; condensing compound A with 2-trifluoromethyl-4-heptafluoroisopropyl-6-bromoaniline amide to obtain compound B; reducing compound B to obtain compound C; and, during the reaction under a hydrogen atmosphere, determining the reaction temperature and hydrogen flow rate in each hydrogenation reaction zone based on the concentration of compound B; reacting compound C with paraformaldehyde to obtain compound D; chlorinating 3-chloro-4-fluorobenzoic acid with thionyl chloride (a chlorinating agent) and dimethylformamide (a catalyst) to obtain compound E; and amide condensing compound E with compound D to obtain the novel diamide compound of this invention. The diamide compound of this invention exhibits excellent insecticidal effects when used in pesticide compositions.

This invention belongs to the field of environmental chemistry and relates to a method for quantitatively analyzing the concentrations of cystine and cysteine ​​in a mixed solution. Based on the theoretical characteristics of the reaction between the disulfide bond in cystine, a representative amino acid, and the thiol group in cysteine, and persulfate, this invention expands the detection capability of the traditional 5,5-dithio-bis-(2-nitrobenzoic acid) (DTNB), providing support for the quantitative analysis of cystine and cysteine ​​concentrations and the study of their transformation processes.

The invention discloses a soybean meal quality evaluation method based on protein oxidation, which comprises the following steps: sampling a soybean meal sample, determining the protein carbonyl content of the soybean meal by adopting a 2, 4-dinitrophenylhydrazine (DNPH) method and / or determining the protein carbonyl content of the soybean meal by adopting 5, 4-dinitrophenylhydrazine (DNPH) method. According to the method, the content of free sulfydryl in the soybean meal protein is measured by a 5, 5 '-dithio-2-nitrobenzoic acid (DTNB) method, the oxidation degree of the soybean meal protein is evaluated, the quality of the soybean meal is graded and evaluated, and the evaluation result can be verified by adopting the in-vitro digestibility of the protein. The evaluation method disclosed by the invention is simple and convenient to operate and high in result repeatability, can effectively evaluate the quality of the soybean meal, and can be applied to quality control, storage management and feed formula optimization of the soybean meal.

This utility model relates to the field of nitrobenzoic acid storage technology, and more particularly to a p-nitrobenzoic acid storage tank, including a tank body and a tank cover detachably connected to the upper end of the tank body, as well as a screw and a drive mechanism. One end of the screw is rotatably connected to the inside of the tank body, and a scraping element for scraping the inner wall of the tank body is threadedly connected to the screw. The scraping element is slidably connected to the inner wall of the tank body. The drive mechanism is located on the tank cover and is used to drive the screw to rotate, thereby scraping the inner wall of the tank body by the scraping element. In this utility model, when the tank cover is connected to the tank body, the drive mechanism drives the screw to rotate, and the screw rotation simultaneously drives the scraping element to slide up and down on the inner wall of the tank body, dynamically scraping off the material adhering to the inner wall of the tank body. At this time, the cleaning process in the closed state of the tank body can reduce the damage caused by manual cleaning of the inner wall of the tank body.

The invention relates to the technical field of organic synthesis, in particular to a method for preparing 4-nitro-N-phenylbenzamide by a one-pot process, which comprises the following steps: under the protection of inert gas, adding an inert solvent, p-nitrobenzoic acid and a composite catalyst into a reactor, and heating to dissolve, the composite catalyst comprising NFM and TPPO; slowly adding thionyl chloride into a reaction system for acylation reaction; then slowly adding aniline into the reaction system to carry out condensation reaction; and after the reaction is finished, carrying out post-treatment to obtain the 4-nitro-N-phenylbenzamide. According to the method, one-pot reaction can be realized, and high-risk intermediates do not need to be separated. In the composite catalyst, NFM efficiently catalyzes acylating chlorination, and TPPO stabilizes an acyl chloride intermediate and promotes condensation, so that the reaction is performed efficiently, stably and highly selectively, and the product is high in yield and purity. And the catalyst is easy to recycle, and the process is green, safe, economical and suitable for industrial production.

This invention relates to the field of lithium-ion battery technology, and in particular to a positive electrode lithium replenishment agent, its preparation method, and a positive electrode sheet, comprising lithium-rich lithium iron phosphate and lithium nitrobenzene. The positive electrode lithium replenishment agent provided by this invention uses LFO as the main lithium source and combines it with lithium nitrobenzene to form a protective layer in situ on the surface of lithium-rich lithium iron phosphate particles, reducing interfacial side reactions and gas generation, achieving efficient active lithium compensation, and thus improving the overall performance of the battery.

The application provides a preparation method of bumetanide, taking p-chlorobenzoic acid as a starting material, performing chlorosulfonation, nitration, and ammonolysis to obtain a key intermediate of 3-(N-(tert-butyl) sulfamoyl)-4-chloro-5-nitrobenzoic acid, then performing phenoxylation, nitro reduction, n-butylation, and tert-butyl removal, and finally obtaining the bumetanide. Compared with the synthesis process of the prior art, the method has less side reactions, low cost, high yield, high safety, and is beneficial to industrial production.

This invention belongs to the field of organic chemical synthesis technology, specifically relating to a method for synthesizing 2-fluoro-3-aminobenzoic acid, an important chemical intermediate. Specifically, o-nitroaniline is condensed with hydrated trichloroacetaldehyde and hydroxylamine hydrochloride to obtain 2-(hydroxyimino)-N-(2-nitrophenyl)acetamide; the resulting product undergoes an intramolecular Beckmann rearrangement to generate 7-nitroindigo; 7-nitroindigo undergoes Bayer-Villedge oxidation to generate 2-amino-3-nitrobenzoic acid; 2-amino-3-nitrobenzoic acid undergoes diazotization and halogenation reactions to generate 2-fluoro-3-nitrobenzoic acid or 2-chloro-3-nitrobenzoic acid; 2-fluoro-3-nitrobenzoic acid can be further reduced by nitro to obtain 2-fluoro-3-aminobenzoic acid; or, 2-chloro-3-nitrobenzoic acid can be esterified to obtain 2-chloro-3-nitrobenzoic acid ester, which can then be fluorinated, saponified, and reduced to obtain 2-fluoro-3-aminobenzoic acid. The raw materials of this invention are low in cost and readily available, and the entire reaction route has specific regioselectivity, making it suitable for industrial production.

The application relates to the technical field of organic synthesis, in particular to a method for preparing 4-nitro-N-phenyl benzamide through one-pot reaction, and the preparation method is as follows: under the protection of inert gas, inert solvent, p-nitrobenzoic acid and a composite catalyst are added into a reactor and heated and dissolved, wherein the composite catalyst comprises NFM and TPPO; a small amount of thionyl chloride is slowly added into the reaction system to perform acylation reaction; then, aniline is slowly added into the reaction system to perform condensation reaction; after the reaction is completed, 4-nitro-N-phenyl benzamide is obtained through post-treatment. The method can realize one-pot reaction, and a high-risk intermediate does not need to be separated. NFM in the composite catalyst can efficiently catalyze acyl chloride, TPPO can stabilize the acyl chloride intermediate and promote condensation, so that the reaction is efficiently, stably and highly selectively performed, the product has high yield and high purity. Moreover, the catalyst is easy to recycle and use, the process is green, safe and economical, and is suitable for industrial production.

The invention belongs to the technical field of nano materials, and discloses a preparation method of a high-stability strong-chlorine-resistance MOF-based seawater electrolysis catalyst. The preparation method comprises the following steps: (1) treating product substrate foamed nickel; (2) preparing a synthetic material from ferric salt, nickel salt, p-toluic acid, p-nitrobenzoic acid, water, ethanol and N, N-dimethylformamide; and (3) synthesizing the final nitro functionalized NiFe-MOF-PNBA (at) NF through a hydrothermal method. When the electrocatalytic material is applied to an alkaline real seawater oxygen evolution reaction, the catalytic performance is better, and higher operation stability can be kept under high current density. In addition, the prepared catalyst also shows excellent electrolytic stability, and the stability can be maintained for more than 4000 hours under the current density of 1.5 A / cm < 2 >.

The application discloses a preparation method of 2-acetylamino-4-[(2-hydroxyethyl)sulfonyl]benzoic acid. The 2-acetylamino-4-[(2-hydroxyethyl)sulfonyl]benzoic acid is prepared from 4-fluoro-2-nitrobenzoic acid methyl ester as a starting material through aromatic nucleophilic substitution reaction, nitro reduction reaction, ester hydrolysis reaction, amino acylation reaction, thioether oxidation reaction and the like. The method has the advantages of mild reaction condition, high yield, low cost, easy availability of raw materials, and the like. The synthesis process meets the requirements of green chemistry, the synthesis route is innovative, the reaction post-treatment is simple, and the product is easy to purify.

The utility model relates to the technical field of p-nitrobenzoic acid production, in particular to a p-nitrobenzoic acid production filtering device which comprises a sealable suction filtration container, the interior of the suction filtration container is divided into a filtering cavity located on the upper portion and a liquid storage cavity located on the lower portion, and a filtering layer is arranged in the filtering cavity. The suction filtration container is further connected with a vacuum pump through an exhaust pipe, the vacuum pump is used for forming a negative pressure environment in the suction filtration container, the pulse type negative pressure adjusting assembly comprises a first electromagnetic valve, a controller and a timer, the first electromagnetic valve is arranged on the exhaust pipe, and the controller is electrically connected with the first electromagnetic valve. According to the utility model, the pulse type negative pressure adjusting component is used for exhausting air, and the air is fed when the air exhausting is stopped, so that periodic negative pressure and positive pressure alternately act on the filter cake, periodic strain is generated in the filter cake, a compact layer on the surface of the filter cake generates microcracks due to repeated stress, and the filtrate permeability is improved.

The present application relates to the technical field of p-nitrobenzoic acid production, and discloses an automatic feeding device for p-nitrobenzoic acid production, which comprises a storage tank, a quantitative discharging assembly and a material conveying assembly; the bottom of the storage tank is provided with a discharging port; the quantitative discharging assembly comprises a butterfly valve one, a butterfly valve two, a quantitative pipe and a weighing sensor, the upper and lower ends of the butterfly valve one are fixedly connected with the discharging port and the quantitative pipe respectively, the quantitative pipe is fixedly connected with the butterfly valve two, and the weighing sensor is arranged on the upper surface of the butterfly plate two in the butterfly valve two and used for weighing the material in the quantitative pipe; the material conveying assembly comprises a nitrogen source, a feeding pipe and a discharging pipe, the two ends of the feeding pipe are fixedly connected with the nitrogen source and the discharging pipe respectively, the top of the feeding pipe is provided with a feeding pipe, and the side of the discharging pipe is provided with an air flow disturbance assembly, which is used for blowing the material in the discharging pipe to adjust the discharging speed and state of the material. The present application can more accurately and stably quantitatively discharge the material, and improves the product quality.

The present invention relates to a process for preparing p-nitrobenzoic acid-2-ethyl hexylester comprising reacting p-nitrobenzoic acid, wherein an excess of 2-ethylhexanol acts as solvent and no additional solvent is added, or p-nitrobenzoic acid and 2-ethylhexanol are provided in equimolar amounts and no additional solvent is added, or 2-ethylhexanol is provided in substoichiometric amounts and no additional solvent is added. Further, the present invention relates to the p-nitrobenzoic acid-2-ethyl hexylester obtained by the process and having high purity and optimum product properties.

The invention relates to the technical field of nitrobenzoic acid production, and discloses an automatic feeding device for p-nitrobenzoic acid production, which comprises a storage tank, a quantitative discharging assembly and a conveying assembly, a discharge hole is formed in the bottom of the storage tank; the quantitative discharging assembly comprises a first butterfly valve, a second butterfly valve, a quantitative pipe and a weighing sensor, the upper end and the lower end of the first butterfly valve are fixedly connected with the discharging port and the quantitative pipe respectively, the quantitative pipe is fixedly connected with the second butterfly valve, and the weighing sensor is arranged on the upper surface of a second butterfly plate in the second butterfly valve and used for weighing materials in the quantitative pipe; the material conveying assembly comprises a nitrogen source, a material conveying pipe and a discharging pipe, the two ends of the material conveying pipe are fixedly connected with the nitrogen source and the discharging pipe correspondingly, a feeding pipe is arranged at the top of the material conveying pipe, and an airflow disturbance assembly is arranged on one side of the discharging pipe and used for blowing air to materials in the discharging pipe so as to adjust the discharging speed and state of the materials. According to the quantitative discharging device, materials can be quantified and discharged more accurately and stably, and the product quality is improved.

The invention discloses sound-absorbing anti-electromagnetic wave glass and a preparation method thereof, and relates to the technical field of glass. The preparation method comprises the following steps: firstly, enabling 4-amino-2-ethoxy-5-nitrobenzoic acid, sodium nitrite, 2-tert-butyl-4-aminophenol and 2-amino-5-chlorobenzaldehyde to react to prepare an anti-ultraviolet agent, absorbing ultraviolet light energy by utilizing opening and closing of a chelate ring structure, and converting the ultraviolet light energy into heat energy to be released, so that the glass has an anti-ultraviolet effect; then preparing an anti-electromagnetic wave layer from the aminated indium tin oxide fibers, an anti-ultraviolet agent, pyromellitic dianhydride and 5-aminothiophene-2-formaldehyde, and enabling the glass to have an anti-electromagnetic wave effect through a multi-level electromagnetic loss structure and intensifying multiple reflection of electromagnetic waves; and compounding the anti-electromagnetic wave layer, the polyvinyl butyral film and the two layers of toughened glass to prepare the sound-absorbing anti-electromagnetic wave glass. The glass prepared by the invention has anti-electromagnetic wave and anti-ultraviolet effects.

The invention provides an aluminum electrolytic capacitor and a preparation method and application thereof. The aluminum electrolytic capacitor comprises a shell with an opening and a core, a guide pin is arranged on the core, a rubber plug is arranged at the opening of the shell, the core penetrates through the rubber plug and is accommodated in the shell, and a sleeve is arranged outside the shell; the core comprises a cathode aluminum foil, an anode aluminum foil, inner-layer electrolytic paper and outer-layer electrolytic paper; the guide pins comprise a cathode guide pin and an anode guide pin; the cathode aluminum foil is provided with a cathode guide pin, the anode aluminum foil is provided with an anode guide pin, and the inner-layer electrolytic paper and the outer-layer electrolytic paper are coated with electrolyte; the electrolyte comprises the following components in percentage by weight: 60%-70% of ethylene glycol, 20%-30% of gamma-butyrolactone, 1%-5% of dimethylformamide, 5%-10% of ammonium adipate, 3%-5% of ammonium sebacate, 1%-2% of boric acid, 0.5%-1% of ammonium dihydrogen phosphate, 0.1%-0.3% of nitrobenzoic acid, 0.05%-0.1% of ammonium molybdate, 0.2%-0.5% of polyvinylpyrrolidone and 0.05%-0.1% of hydroquinone; the aluminum electrolytic capacitor can still work normally for a long time at the ultralow temperature of 450V and the temperature of-55 DEG C, the low-temperature capacity attenuation at the temperature of-55 DEG C can be as low as-14.50%, and the low-temperature impedance ratio at the temperature of-55 DEG C can reach 1.28.

This utility model relates to the field of p-nitrobenzoic acid production technology, and in particular to a device for quantitatively dispensing raw materials for p-nitrobenzoic acid production. The device includes a mixed acid solution reactor, a nitration reactor, a staged cooling assembly, and a control mechanism. The mixed acid solution reactor is used to prepare a mixed acid solution of sulfuric acid and nitric acid. The nitration reactor is used to react the cooled mixed acid solution with toluene. The staged cooling assembly is connected between the output end of the mixed acid solution reactor and the input end of the nitration reactor, and is used to cool the mixed acid solution that needs to be quantitatively added to the nitration reactor. The control mechanism includes a controller and a temperature sensor. This utility model uses the staged cooling assembly to cool the mixed acid solution that needs to be quantitatively added to the nitration reactor in small batches, effectively avoiding the problem of cooling lag caused by large quantities of mixed acid solution and long cooling paths, and ensuring the temperature uniformity of the mixed acid solution.

The present invention relates to a novel nitration process of 2-chloro-4-fluorobenzoic acid or alkyl 2-chloro-4-fluorobenzoate, using oleum and nitric acid, to obtain 2-chloro-4-fluoro-5-nitrobenzoic acid or alkyl 2-chloro-4-fluoro-5-nitrobenzoates; purifying the crude reaction product; and recovering 2-chloro-4-fluoro-5-nitrobenzoic acid or alkyl 2-chloro-4-fluoro-5-nitrobenzoates in an essentially pure form, which can be used in the synthesis of the herbicide saflufenacil.

An amide-containing aromatic diamine has the following structural formula: where Ar is a group with an aromatic ring structure. The preparation method includes the following steps: (1) mixing and reacting components including aromatic diamine, p-nitrobenzoic acid, alkyl phosphoric anhydride and polar aprotic organic solvent; (2) adding carboxylic acid and halogen-free quaternary ammonium salt to the product obtained in step (1) to obtain a mixed solution, which is placed in the cathode cell of an H-type electrolytic cell; the anode cell and the cathode cell are separated by a Nafion membrane; adding the same polar aprotic organic solvent and halogen-free organic electrolyte as the cathode cell to the anode cell of the H-type electrolytic cell, and adding a metal ion-free reducing agent; and conducting the reaction by electrolysis; (3) purifying the cathode reaction solution obtained in step (2) by post-treatment to obtain the amide-containing aromatic diamine. The yield, purity and whiteness of the amide-containing aromatic diamine are higher.

The invention belongs to the technical field of antitumor drug development, and particularly relates to a novel 4-aniline quinazoline derivative, a synthesis method and a drug for treating cancer. According to the invention, 2-amino-4-nitrobenzoic acid is used as an initial raw material, and a series of novel 4-aniline quinazoline derivatives containing cinnamic acid are synthesized through multi-step reactions such as trifluoroacetylation, ring closing, chlorination, aromatic amine substitution, reduction and cinnamic acylation. In-vitro antitumor activity research shows that part of the compounds show remarkable inhibitory activity on multiple tumor cells such as MDA-MB-231, A549 and SMMC-7721, can induce cell apoptosis and inhibit cell migration, and shows excellent antitumor drug development prospects. In addition, the structure-function relationship of the series of compounds is further deeply studied, and reference significance is provided for further development and research of novel antitumor drugs.

The application provides a pharmaceutical preparation containing oxyburocaine hydrochloride and a preparation method of the pharmaceutical preparation, and steps of the method comprise the following steps: adding N,N-dimethylformamide and an alkaline accelerator to 3-hydroxy-4-nitrobenzoic acid methyl ester to obtain 3-butoxy-4-nitrobenzoic acid; adding toluene and the alkaline accelerator to the 3-butoxy-4-nitrobenzoic acid, and adding 2-diethylamino chloroethane hydrochloride to obtain 3-butoxy-4-nitrobenzoic acid-2-(diethylamino) ethyl ester hydrochloride; continuously adding toluene, the alkaline accelerator and a palladium-carbon catalyst to obtain crude oxyburocaine, and cooling, crystallization, filtration and drying of the crude oxyburocaine to obtain oxyburocaine hydrochloride; adding a buffer aqueous phase and a clathrate agent to the oxyburocaine hydrochloride to obtain the pharmaceutical preparation containing oxyburocaine hydrochloride. The buffer aqueous phase, the clathrate agent, pH and osmotic pressure adjustment, filtration, sterile filling and low-temperature curing are combined to improve the irritability and stability of the oxyburocaine hydrochloride preparation.

The invention discloses a synthesis method of 5-nitro-2-chloro-4-fluoro-N-(N-isopropyl-N-methylsulfonyl) benzamide, and the synthesis method comprises the following steps: firstly, synthesizing 5-nitro-2-chloro-4-fluoro-N-(N-isopropyl-N-methylsulfonyl) benzamide; according to the method, 2-chloro-4-fluoro-5-nitrobenzoic acid and N-methyl-N-isopropyl sulfonyl diamine are used as raw materials, diethylamino sulfur trifluoride (DAST) / trifluoroacetic anhydride (TFAA) is directly added into an organic solvent to serve as a compound condensation reagent for an amide condensation reaction, after the reaction is finished, a product can be separated out through crystallization, mother liquor is evaporated, and the solvent is recycled. Alkali does not need to be added, reaction conditions are mild (0-50 DEG C), by-products are volatile substances, the solvent recovery rate is larger than or equal to 90%, the product yield is larger than or equal to 70%, the purity is larger than or equal to 97%, operation is easy, the method is suitable for industrial amplification, and remarkable economic and environmental benefits are achieved.

The following invention relates to an improved oxidation process whereby 1-methyl-4-(methylsulfonyl)-2-nitrobenzene (NMST) is oxidized to 4-(methylsulfonyl)-2-nitrobenzoic acid (NMSBA).

The invention provides a preparation method of L-gamma-glutamyl-3-carboxyl-4-nitroaniline ammonium salt. The preparation method comprises the following steps: (1) mixing 5-amino-2-nitrobenzoic acid and an alkylating reagent for reaction to obtain an intermediate 1; (2) mixing and reacting the intermediate 1 with Boc-L-glutamic acid-1-tert-butyl ester and a condensing agent to obtain an intermediate 2; (3) mixing the intermediate 2 with a hydrolysis reagent for reaction to obtain an intermediate 3; and (4) mixing the intermediate 3 with alkali to react, so as to obtain the L-gamma-glutamyl-3-carboxyl-4-nitroaniline ammonium salt. According to the preparation process of the L-gamma-glutamyl-3-carboxyl-4-nitroaniline ammonium salt, the steps of esterification, condensation, deprotection and salification are sequentially performed, the reaction conditions are mild, side reactions are few, industrial amplification production of high-purity products is easier to realize, and a safe, efficient and green new way is provided for stable supply of Glupa-C.

The invention discloses a method for synthesizing a topramezone-ethyl intermediate, which comprises the following steps: 1) carrying out substitution reaction on 2, 6-dichlorotoluene by ethylene glycol monomethyl ether; 2) reacting substituted chlorobenzene with magnesium to generate a Grignard reagent, and then reacting with carbon dioxide to obtain benzoic acid; (3) carrying out halogenation or nitration reaction on the substituted benzoic acid derivative to generate a 4-halogenated benzoic acid analogue or a 4-nitrobenzoic acid analogue; 4) reacting the analogue with methyl mercaptan to generate 4-methylthiobenzoic acid; and 5) carrying out oxidation reaction on the 4-methylthio benzoic acid derivative to obtain TP-1. The raw materials are simple and easy to obtain, the reaction operation is simple and convenient, a noble metal catalyst and high-pressure reaction equipment are not needed, and the method is green, environment-friendly and suitable for commercial large-scale production and has huge large-scale production potential.

The invention belongs to the technical field of organic synthesis, and particularly relates to a preparation device and method of m-nitrobenzonitrile. Comprising the following steps: step S10: acylating chlorination reaction: taking m-nitrobenzoic acid as a raw material, and reacting the m-nitrobenzoic acid with thionyl chloride in a preparation device of a constant temperature device under the catalysis of a nitrogen-containing organic matter to generate m-nitrobenzoyl chloride; step S20, amidation reaction: enabling the m-nitrobenzoyl chloride obtained in the step S10 to react with ammonia gas to generate m-nitrobenzamide; and step S30: dehydration reaction: dehydrating and filtering the m-nitrobenzamide obtained in the step S20 and thionyl chloride in a negative pressure filtering device in the presence of a nitrogen-containing organic matter to obtain the m-nitrobenzonitrile. According to the scheme, the problems of long preparation time and low yield of the m-nitrobenzonitrile are solved.

The invention discloses a production system and a production method of medicinal p-aminobenzoic acid. The production system comprises a filter column, a hydrogenation reaction kettle, a catalyst filter, a tubular hydrogenation reactor, a fine filter and a crystallization kettle, the production method comprises the following steps: pumping p-nitrobenzoic acid and a solvent into a hydrogenation reaction kettle through a filter column, and reacting until 3-5% of raw materials are left; then pressing out the material from the hydrogenation reaction kettle, enabling the material to enter a tubular hydrogenation reactor through a catalyst filter for continuous reaction until the material is completely reacted, finally filtering the liquid material through a micro-filter, and enabling the liquid material to enter a crystallization kettle for crystallization. On one hand, a small amount of residual colored impurities, heavy metal impurities and insoluble tiny foreign matters in raw materials are removed by adopting a multi-effect filter column, and on the other hand, hydrogenation reaction is carried out by adopting a manner of connecting a kettle type reactor and a tubular reactor in series; the content of intermediate-state impurities in nitro reduction and the content of impurities in side reactions such as decarboxylation and polymerization can be effectively reduced, and finally para aminobenzoic acid meeting the medicinal-grade requirement can be obtained.

The invention relates to a synthesis method of 2-amino-5-chloro-N, 3-dimethyl benzamide, which comprises the following steps: hydrogenation reaction: adding 3-methyl-2-nitrobenzoic acid, palladium on carbon, methanol, nitrogen and hydrogen for replacement; filtering to remove palladium and carbon, adding activated carbon into filtrate for decoloration, concentrating under reduced pressure, crystallizing, filtering and drying; cyclization reaction: adding 3-methyl-2-nitrobenzoic acid, dichloromethane, oxalyl chloride and aluminum trichloride, reacting, separating liquid, removing a water phase, concentrating an organic phase under reduced pressure, cooling, crystallizing, filtering and drying to obtain 2-amino-5-chloro-N, 3-dimethylbenzamide; 2-amino-5-chloro-N, 3-dimethylbenzamide, ethanol, a catalyst PIDA and CuCl2 are sequentially added, nitrogen displacement and stirring heating are carried out, a reaction is carried out for 12 h, a 10% sodium bicarbonate aqueous solution is dropwise added until the pH value is 6.0-6.5, the temperature is reduced to the room temperature, and filtering and drying are carried out; and ring-opening reaction: adding 6-chloro-3-methyl itaconic anhydride and purified water, replacing with nitrogen, cooling, adding 40% methylamine aqueous solution, heating, sampling, detecting reaction, cooling, crystallizing, filtering and drying.