Green synthesis method of 2-nitro-4-methylsulfonylbenzoic acid

Abstract

The invention discloses a green synthesis method of 2-nitro-4-methylsulfonylbenzoic acid, which comprises the following steps: by taking 2-nitro-4-methylsulfonyltoluene as a raw material, adding water, oxygen and nitric acid, heating to a reaction temperature, reacting, supplementing a proper amount of oxygen in the reaction process, cooling after the reaction is finished, filtering reactants, and collecting filtrate for the next circulation, thereby obtaining the 2-nitro-4-methylsulfonylbenzoic acid. 2-nitro-4-methylsulfonylbenzoic acid can be obtained only by washing the filter cake, and the target product 2-nitro-4-methylsulfonylbenzoic acid can be obtained by drying the washed filter cake in a drying oven for several days. The method is simple to operate, single nitric acid is adopted for reaction, while sulfuric acid and a heavy metal catalyst need to be used for preparing 2-nitro-4-methylsulfonylbenzoic acid through a traditional nitric acid oxidation reaction, the operation is dangerous and complex, and pollution gas is easily generated; a small amount of nitric acid is supplemented into the filtrate after the reaction can be directly used for next oxidation, so that generation of a large amount of acidic wastewater is avoided.

Description

(I) Technical field

[0001] The invention belongs to the field of chemical raw material preparation, and specifically relates to a green synthesis method of 2-nitro-4-methylsulfonylbenzoic acid. (II) Background technology

[0002] 2-Nitro-4-methylsulfonylbenzoic acid (CAS No.: 110964-79-9) is a carboxylic acid derivative. It is a white or light yellow crystalline powder at room temperature. It is soluble in organic solvents such as ethanol, dichloromethane and ether, and slightly soluble in water. This product is an important intermediate for the synthesis of mesotrione, which is an excellent herbicide and has been widely used worldwide. In addition, 2-nitro-4-methylsulfonylbenzoic acid is also widely used in dyes, medicines and other industries. Its structural formula is:

[0003]

[0004] At present, the industry mainly prepares 2-nitro-4-methylsulfonylbenzoic acid by oxidizing 2-nitro-4-methylsulfonyltoluene, and chemical reagents such as nitric acid, potassium dichromate, sodium hypochlorite and potassium permanganate are usually selected as oxidants. The current nitric acid oxidation method mainly adds 2-nitro-4-methylsulfonyltoluene, catalyst V2O5, and sulfuric acid with a mass fraction of 70% into a reaction flask, and after stirring evenly, air is introduced into the reaction solution, and the temperature is raised to 145°C, and 65% nitric acid is slowly added dropwise within a few hours. After the dropwise addition is completed, the reaction is continued for several hours, and the reaction ends, and the reaction is cooled to room temperature, and an appropriate amount of water is added, stirred, filtered, and the solid is washed with a small amount of dilute hydrochloric acid, and a white solid product is obtained by drying. However, the method uses a heavy metal catalyst, which can cause environmental pollution, and the reaction system is not easy to recycle, and harmful tail gas can also be produced to cause environmental pollution, and the operation is relatively complicated and not easy for industrial production.

[0005] In summary, the problems of the traditional method for preparing 2-nitro-4-methylsulfonylbenzoic acid by oxidation of 2-nitro-4-methylsulfonyltoluene are: 1) heavy metal catalysts are used; 2) the reaction system is difficult to recycle and the amount of waste liquid is large; 3) a large amount of waste gas is generated, causing environmental problems; 4) the operation is complicated and there are major safety hazards. (III) Summary of the invention

[0006] The purpose of the present invention is to provide a green synthesis method of 2-nitro-4-methylsulfonylbenzoic acid in view of the shortcomings of the traditional nitric acid oxidation process, thereby avoiding the problems of releasing harmful gases after the oxidation is completed, and using catalysts such as sulfuric acid and vanadium pentoxide during the oxidation process, and complicated operation.

[0007] The technical solution adopted by the present invention is:

[0008] The present invention uses 2-nitro-4-methylsulfonyltoluene as a raw material, adds water, oxygen, and nitric acid to the reaction temperature for reaction, supplements an appropriate amount of oxygen during the reaction, cools after the reaction is completed, filters the reactant, collects the filtrate for the next cycle, and only needs to wash the filter cake to obtain 2-nitro-4-methylsulfonylbenzoic acid, and places the washed filter cake in an oven for drying for several days to obtain the target product 2-nitro-4-methylsulfonylbenzoic acid. The above method is simple to operate and uses a single nitric acid for reaction, while the traditional nitric acid oxidation reaction to prepare 2-nitro-4-methylsulfonylbenzoic acid requires the use of sulfuric acid and a heavy metal catalyst, and the operation is dangerous and complicated and easily generates polluting gases; the filtrate after the reaction is completed can be directly used for the next oxidation by adding a small amount of nitric acid to avoid the generation of a large amount of acidic wastewater.

[0009] The specific scheme of the present invention is as follows:

[0010] 2-nitro-4-methylsulfonyltoluene, nitric acid, water and oxygen are added into an autoclave at a pressure of 1-6 MPa. The autoclave is reacted at 150-210° C. for 4-10 hours. Oxygen is continuously added during the reaction. After the reaction is completed, the autoclave is cooled naturally and filtered. The filter cake is washed and dried to obtain white powder 2-nitro-4-methylsulfonylbenzoic acid. The filtrate is nitric acid. After analyzing the purity of the nitric acid, an appropriate amount of concentrated nitric acid is added to reach the concentration required for the reaction and then used for recycling.

[0011] Preferably, the molar ratio of 2-nitro-4-methylsulfonyltoluene to nitric acid in the scheme is 1:1-5, preferably 1:2-4.

[0012] Preferably, the reaction temperature is 180 to 120°C.

[0013] Preferably, the reaction time is 6 to 8 hours.

[0014] Preferably, the mass concentration of nitric acid is 10% to 50%, preferably 20% to 30%.

[0015] The specific principles of the present invention are as follows:

[0016] The raw material 2-nitro-4-methylsulfonyltoluene and nitric acid react at a desired temperature, and 2-nitro-4-methylsulfonyltoluene is oxidized to obtain the product 2-nitro-4-methylsulfonylbenzoic acid. The nitric acid is reduced to obtain nitrogen dioxide (NO2) and nitric oxide (NO) and water.

[0017]

[0018] Three molecules of nitrogen dioxide can react with water to produce two molecules of nitric acid and one molecule of nitric oxide. Nitric oxide is poorly soluble in water, but it can react quickly with oxygen to produce nitrogen dioxide.

[0019] 3NO2+H2O=2HNO3+NO (2

[0020] 2NO+O2=2NO2 (3)

[0021] Reaction (2) × 4 + reaction (3) × 3 to get the total reaction of nitrogen oxides and oxygen

[0022] 6NO2+2NO+4H2O+3O2=8HNO3 (4)

[0023] Reaction (1) × 2 + reaction (4) gives the following overall reaction:

[0024]

[0025] Based on the above principle, the present invention continuously supplements pure oxygen in the system as the reaction proceeds, so that it is always kept in excess in the system. Therefore, the nitrogen dioxide generated by the reaction is quickly absorbed by water, and the nitric oxide generated is quickly oxidized to generate nitrogen dioxide in the presence of excess oxygen, and then absorbed by water, so that nitrogen oxides are continuously consumed, so that there is no waste gas such as nitrogen oxides in the gas phase of the reaction system, and the concentration of nitric acid remains basically unchanged.

[0026] The catalytic cycle reaction is more clearly shown as follows:

[0027]

[0028] In general, nitric acid plays the role of a catalyst, and the overall reaction process is that 2-nitro-4-methylsulfonyltoluene reacts with pure oxygen under the catalysis of nitric acid to obtain 2-nitro-4-methylsulfonylbenzoic acid and water. The reaction process is as follows:

[0029] Beneficial effects of the present invention:

[0030] The invention uses 2-nitro-4-methylsulfonyltoluene as a raw material, adds water, nitric acid and oxygen, continuously supplements oxygen during the reaction process to ensure that the oxygen in the kettle is always excessive, cools the reaction after completion, filters, obtains nitric acid filtrate, collects the filtrate for the next reaction, rinses the filter cake with water until a white powder is obtained, and dries the filter cake to obtain white powder 2-nitro-4-methylsulfonylbenzoic acid. Compared with the traditional 2-nitro-4-methylsulfonylbenzoic acid production process, the invention provides a relatively low cost, relatively friendly environment, and relatively simple operation. The traditional nitric acid oxidation method requires concentrated sulfuric acid and a heavy metal catalyst, drips 65% nitric acid at high temperature, and simultaneously generates a large amount of nitrogen oxide (NOx) gas, which is dangerous to operate and difficult to control, and is not easy to industrialize.

[0031] Compared with the traditional nitric acid oxidation process, the present invention reduces the waste gas generation in the reaction process, simplifies the operation, the filtrate can be recycled, no waste water is generated, no heavy metals or precious metals are involved in the catalysis, has good environmental protection and low cost. (IV) Description of the drawings

[0032] Table 1 shows the average peak areas of 2-nitro-4-methylsulfonylbenzoic acid standard solutions at different concentrations;

[0033] Figure 1 This is the HPLC chart of 2-nitro-4-methylsulfonyltoluene;

[0034] Figure 2 HPLC chart of 2-nitro-4-methylsulfonylbenzoic acid standard;

[0035] Figure 3 is the HPLC chart of oxidation products;

[0036] Figure 4 It is the external standard curve diagram of 2-nitro-4-methylsulfonylbenzoic acid;

[0037] Figure 5 The filtrate is recycled;

[0038] Figure 6 It is the crude product obtained by filtration after the reaction is completed;

[0039] Figure 7 The crude product is washed, filtered and dried to obtain the target product 2-nitro-4-methylsulfonylbenzoic acid;

[0040] Figure 8 is the H NMR spectrum of the target product 2-nitro-4-methylsulfonylbenzoic acid;

[0041] Fig. 9 This is the mass spectrum of the target product 2-nitro-4-methylsulfonylbenzoic acid. (V) Specific implementation methods

[0042] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0043] Example 1

[0044] 6.52 g of 2-nitro-4-methylsulfonyltoluene and 37.24 g of dilute nitric acid with a mass concentration of 20% were added to an autoclave, and oxygen was charged to a system pressure of 1.0 MPa and then vented. The system pressure was maintained at 1.0 MPa after oxygen replacement three times. The temperature was then slowly raised to 180° C. During the reaction, the pressure dropped, and oxygen was continuously added to maintain the system pressure at 4.4 MPa. After reacting for 6 hours, the temperature was lowered, and the obtained solid-liquid mixture was filtered. The filtrate was recovered for the next reaction feeding. The filter cake was washed and dried to obtain a 2-nitro-4-methylsulfonylbenzoic acid solid weighing 7.39 g. The solid product was subjected to liquid chromatography analysis and the purity was 99.2%, with a yield of 98.7%.

[0045] Example 2

[0046] 6.52 g of 2-nitro-4-methylsulfonyltoluene and 37.24 g of dilute nitric acid with a mass concentration of 20% were added to an autoclave, and oxygen was added to the system pressure to 1.0 MPa, then the autoclave was vented. After replacing the system pressure with oxygen three times, the system pressure was maintained at 1.0 MPa. The autoclave was then slowly heated to 150° C. The pressure dropped during the reaction, and oxygen was continuously added to maintain the system pressure at 2.0 MPa. The reaction was cooled after 6 hours, and the resulting solid-liquid mixture was filtered. The filtrate was recovered for the next reaction. The filter cake was washed and dried to obtain a 2-nitro-4-methylsulfonylbenzoic acid solid weighing 7.35 g. The solid product was subjected to liquid chromatography analysis and the purity was 93.7%, with a yield of 92.7%.

[0047] Example 3

[0048] 6.52 g of 2-nitro-4-methylsulfonyltoluene and 37.24 g of dilute nitric acid with a mass concentration of 20% were added to an autoclave, and oxygen was added to the system pressure to 1.0 MPa, then the autoclave was vented. After replacing the system pressure with oxygen three times, the system pressure was maintained at 1.0 MPa. The autoclave was then slowly heated to 210° C. The pressure dropped during the reaction, and oxygen was continuously added to maintain the system pressure at 6.0 MPa. The reaction was cooled after 6 hours, and the resulting solid-liquid mixture was filtered. The filtrate was recovered for the next reaction. The filter cake was washed and dried to obtain a 2-nitro-4-methylsulfonylbenzoic acid solid weighing 7.38 g. The solid product was subjected to liquid chromatography analysis and the purity was 99.6%, with a yield of 99.0%.

[0049] Example 4

[0050] 6.52 g of 2-nitro-4-methylsulfonyltoluene and 37.24 g of dilute nitric acid with a mass concentration of 20% were added to an autoclave, and oxygen was added to the system pressure to 1.0 MPa, then the autoclave was vented. After replacing the system pressure with oxygen three times, the system pressure was maintained at 1.0 MPa. The autoclave was then slowly heated to 180° C. The pressure dropped during the reaction, and oxygen was continuously added to maintain the system pressure at 4.0 MPa. The reaction was cooled after 4 hours, and the resulting solid-liquid mixture was filtered. The filtrate was recovered for the next reaction. The filter cake was washed and dried to obtain a 2-nitro-4-methylsulfonylbenzoic acid solid weighing 7.37 g. The solid product was subjected to liquid chromatography analysis and the purity was 98.5%, with a yield of 97.7%.

[0051] Example 5

[0052] 6.52 g of 2-nitro-4-methylsulfonyltoluene and 37.24 g of dilute nitric acid with a mass concentration of 20% were added to an autoclave, and oxygen was charged to a system pressure of 1.0 MPa and then vented. The system pressure was maintained at 1.0 MPa after oxygen replacement three times. The temperature was then slowly raised to 180° C. During the reaction, the pressure dropped, and oxygen was continuously added to maintain the system pressure at 4.8 MPa. After reacting for 10 hours, the temperature was lowered, and the obtained solid-liquid mixture was filtered. The filtrate was recovered for the next reaction feeding. The filter cake was washed and dried to obtain a 2-nitro-4-methylsulfonylbenzoic acid solid weighing 7.38 g. The solid product was subjected to liquid chromatography analysis and the purity was 99.5%, with a yield of 98.9%.

[0053] Example 6

[0054] 6.52 g of 2-nitro-4-methylsulfonyltoluene and 19.0 g of dilute nitric acid with a mass concentration of 50% were added to an autoclave, and oxygen was added to the system pressure to 1.0 MPa, then the autoclave was vented. After replacing the system pressure with oxygen three times, the system pressure was maintained at 1.0 MPa. The autoclave was then slowly heated to 180° C. The pressure dropped during the reaction, and oxygen was continuously added to maintain the system pressure at 5.3 MPa. The autoclave was cooled after reacting for 6 hours, and the obtained solid-liquid mixture was filtered. The filtrate was recovered for the next reaction. The filter cake was washed and dried to obtain a 2-nitro-4-methylsulfonylbenzoic acid solid weighing 7.36 g. The solid product was subjected to liquid chromatography analysis and the purity was 98.5%, with a yield of 97.6%.

[0055] Example 7

[0056] 10.87 g of 2-nitro-4-methylsulfonyltoluene and 18.98 g of dilute nitric acid with a mass concentration of 17.0% were added to an autoclave, and oxygen was added to the system pressure to 1.0 MPa, then the autoclave was vented. After replacing the system pressure with oxygen three times, the system pressure was maintained at 1.0 MPa. The autoclave was then slowly heated to 180° C. The pressure dropped during the reaction, and oxygen was continuously added to maintain the system pressure at 5.0 MPa. The autoclave was cooled after reacting for 6 hours, and the obtained solid-liquid mixture was filtered. The filtrate was recovered for the next reaction. The filter cake was washed and dried to obtain a 2-nitro-4-methylsulfonylbenzoic acid solid weighing 11.72 g. The solid product was subjected to liquid chromatography analysis and the purity was 92.3%, with a yield of 87.3%.

[0057] Example 8

[0058] 10.87 g of 2-nitro-4-methylsulfonyltoluene and 41.04 g of dilute nitric acid with a mass concentration of 30.0% were added to an autoclave, and oxygen was added to the system pressure to 1.0 MPa, then the autoclave was vented. After replacing the system pressure with oxygen three times, the system pressure was maintained at 1.0 MPa. The autoclave was then slowly heated to 180° C. The pressure dropped during the reaction, and oxygen was continuously added to maintain the system pressure at 6.0 MPa. The reaction was cooled after 6 hours, and the obtained solid-liquid mixture was filtered. The filtrate was recovered for the next reaction. The filter cake was washed and dried to obtain a 2-nitro-4-methylsulfonylbenzoic acid solid weighing 12.33 g. The solid product was subjected to liquid chromatography analysis and the purity was 99.6%, with a yield of 99.2%.

[0059] Example 9

[0060] 4.31 g of 2-nitro-4-methylsulfonyltoluene and 50.41 g of dilute nitric acid with a mass concentration of 10.0% were added to an autoclave, and oxygen was added to the system pressure to 1.0 MPa, then the autoclave was vented. After replacing the system pressure with oxygen three times, the system pressure was maintained at 1.0 MPa. The autoclave was then slowly heated to 180° C. The pressure dropped during the reaction, and oxygen was continuously added to maintain the system pressure at 5.0 MPa. The autoclave was cooled after reacting for 6 hours, and the obtained solid-liquid mixture was filtered. The filtrate was recovered for the next reaction. The filter cake was washed and dried to obtain a 2-nitro-4-methylsulfonylbenzoic acid solid weighing 4.12 g. The solid product was subjected to liquid chromatography analysis and the purity was 91.2%, with a yield of 76.5%.

[0061] Example 10 Analysis Method of Product 2-Nitro-4-Methylsulfonylbenzoic Acid

[0062] (1) Preparation of 2-nitro-4-methylsulfonylbenzoic acid standard solution

[0063] Accurately weigh 0.05g of 2-nitro-4-methylsulfonylbenzoic acid standard sample on an analytical balance and add it to a 50mL volumetric flask. Take a small amount of chromatographic methanol to dissolve it by ultrasonication, then add chromatographic methanol to the scale line, shake well and set aside. Take 6 25mL volumetric flasks and use a pipette to accurately draw 6 different volumes (1.25mL, 2.50mL, 3.75mL, 5.00mL, 6.25mL, 7.50mL) of 2-nitro-4-methylsulfonylbenzoic acid standard solution into the corresponding volumetric flasks, add chromatographic methanol to the scale line, and prepare a series of concentration samples (0.05mg / mL, 0.10mg / mL, 0.15mg / mL, 0.20mg / mL, 0.25mg / mL, 0.30mg / mL), shake well and set aside;

[0064] (2) Drawing of the standard curve of 2-nitro-4-methylsulfonylbenzoic acid

[0065] Take six different concentrations (0.05 mg / mL, 0.10 mg / mL, 0.15 mg / mL, 0.20 mg / mL, 0.25 mg / mL, 0.30 mg / mL) of 2-nitro-4-methylsulfonylbenzoic acid samples, accurately inject equal volume of each concentration three times to get the average value (Table 1), and fit the standard curve according to the average value of each concentration ( Figure 4 ).

[0066] (3) Liquid chromatography analysis parameters

[0067] The 2-nitro-4-methylsulfonylbenzoic acid product was analyzed using a liquid chromatography instrument, the liquid chromatography instrument model was Agilent HPLC-1260 Infinity, the chromatographic column was C18, the particle size was 5 μm, the inner length was 4.6 mm, the column length was 250 mm, the detection wavelength was 254 nm, the column temperature was 40° C., the flow rate was 1 ml / min, the feed volume was 0.02 ml, the analysis time was 15 minutes, and the mobile phase ratio was: V (methanol): V (0.8% acetic acid aqueous solution) = 45:55. The peak area obtained by each liquid chromatography was calculated according to the standard curve ( Figure 4 ) can be used to calculate the purity of the sample analyzed.

[0068] Example 11 Filtrate Application

[0069] The filtrate of Example 1 and concentrated nitric acid with a mass concentration of 65% were used to prepare dilute nitric acid with a mass concentration of 20%. 6.52 g of 2-nitro-4-methylsulfonyltoluene and 37.24 g of the above-prepared 20% dilute nitric acid were added to the autoclave. The other operating methods were the same as those in Example 1. 2-nitro-4-methylsulfonylbenzoic acid solid was obtained, weighing 7.43 g. The solid product was subjected to liquid chromatography analysis and the purity was 99.1%, and the yield was 99.1%. The recycled filtrate was Figure 5As shown, after the oxidation reaction is completed, the crude product obtained by filtration is as follows Figure 6 As shown, the crude product is washed, filtered, and dried to obtain the target product 2-nitro-4-methylsulfonylbenzoic acid as shown in Figure 7 The obtained product 2-nitro-4-methylsulfonylbenzoic acid was detected by nuclear magnetic resonance hydrogen spectrum, as shown in Figure 8 As shown, the analysis of the H NMR spectrum is as follows: 1 H NMR (400MHz, Methanol-d4) δ8.51 (d, J = 1.7 Hz, 1H), 8.33 (dd, J = 8.0, 1.7 Hz, 1H), 8.09 (d, J = 8.0 Hz, 1H), 3.26 (s, 3H). The obtained product 2-nitro-4-methylsulfonylbenzoic acid was analyzed by mass spectrometry. Fig. 9 As shown, TOF (ESI) m / s calcd for C8H6NO6S+(M+H)+244, found 244. The above structural characterization shows that the obtained compound is the target product 2-nitro-4-methylsulfonylbenzoic acid.

[0070] Table 1: Average peak areas of 2-nitro-4-methylsulfonylbenzoic acid standard solutions at different concentrations

[0071]

Claims

1. A green synthesis method of 2-nitro-4-methylsulfonylbenzoic acid, characterized in that: 2-nitro-4-methylsulfonyltoluene is used as a raw material, in the presence of nitric acid, pure oxygen is used as an oxidant, and the reaction is carried out at a reaction temperature of 150-210° C. for 4-10 hours, and then 2-nitro-4-methylsulfonylbenzoic acid is obtained by filtering and washing.

2. The green synthesis method of 2-nitro-4-methylsulfonylbenzoic acid according to claim 1, characterized in that: The molar ratio of 2-nitro-4-methylsulfonyltoluene to nitric acid is 1:1-5.

3. The green synthesis method of 2-nitro-4-methylsulfonylbenzoic acid according to claim 2, characterized in that: The molar ratio of 2-nitro-4-methylsulfonyltoluene to nitric acid is 1:2-4.

4. The green synthesis method of 2-nitro-4-methylsulfonylbenzoic acid according to claim 1, characterized in that: The mass concentration of the nitric acid is 10% to 50%.

5. The green synthesis method of 2-nitro-4-methylsulfonylbenzoic acid according to claim 4, characterized in that: The mass concentration of the nitric acid is 20%-30%.

6. The green synthesis method of 2-nitro-4-methylsulfonylbenzoic acid according to claim 1, characterized in that: The reaction conditions are: pressure of 1-6 MPa, reaction time of 4-10 hours, and reaction temperature of 150-210°C.

7. The green synthesis method of 2-nitro-4-methylsulfonylbenzoic acid according to claim 6, characterized in that: The reaction time is 6 to 8 hours.

8. The green synthesis method of 2-nitro-4-methylsulfonylbenzoic acid according to claim 6, characterized in that: The reaction temperature is 180-200°C.

9. The green synthesis method of 2-nitro-4-methylsulfonylbenzoic acid according to claim 1, characterized in that: After the reaction is completed, the filtrate from the mother liquor is filtered and recycled after adding nitric acid.

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