A catalytic technique for the production of 2-nitro-4-methylsulfonylbenzoic acid

Abstract

This invention relates to a method for producing 2-nitro-4-methylsulfonylbenzoic acid from 2-nitro-4-methylsulfonyltoluene. The method involves using 2-nitro-4-methylsulfonyltoluene as a raw material and air (oxygen-enriched air or oxygen) as an oxidant in an acidic aqueous solution. A multi-component catalytic system composed of a metal oxygen-metal compound, metal ions, or rare earth ions, and a halogen is employed to form a gas-liquid-solid three-phase reaction, oxidizing 2-nitro-4-methylsulfonyltoluene to 2-nitro-4-methylsulfonylbenzoic acid. This invention overcomes the shortcomings of existing 2-nitro-4-methylsulfonylbenzoic acid production methods, such as large amounts of waste gas and wastewater generation, severe corrosion, low selectivity, and high production costs, thereby reducing environmental pollution and achieving clean production of 2-nitro-4-methylsulfonylbenzoic acid.

Description

Technical Field

[0001] This invention relates to a process for producing 2-nitro-4-methylsulfonylbenzoic acid. Background Technology

[0002] Corn is the world's highest-yielding crop, rich in protein, and can be used as a food source, as well as a raw material for vegetable oil, bio-fermentation, pharmaceuticals, chemicals, and livestock feed. Due to the dwindling oil resources, the demand for bioethanol is growing, sparking a global corn-growing boom. Currently, my country ranks second in both corn production and consumption, and corn production plays a vital role in my country's agricultural production and national economy. In recent years, about half of my country's cornfields have been affected by weeds to varying degrees, with severe weed infestations affecting approximately 10-20% of the area, resulting in a 20%-30% reduction in corn yield. Mesotrione, a highly efficient and environmentally friendly corn herbicide developed by Syngenta in the mid-1970s, is widely used worldwide due to its broad-spectrum weed control, high activity, strong miscibility, low toxicity, environmental friendliness, safety for subsequent crops, and flexible application. Therefore, producing mesotrione can not only eliminate weeds in my country's cornfields and increase corn yields but also generate foreign exchange through exports.

[0003] An important intermediate in the synthesis of mesotrione is 2-nitro-4-methylsulfonylbenzoic acid (NMSBA), also known as o-nitro-p-methylsulfonylbenzoic acid, 2-nitro-4-methylsulfonylbenzoic acid, or 4-methylsulfonyl-2-nitrobenzoic acid. Its English name is 2-Nitro-4-methylsulfonylbenzoic acid or O-nitro-p-methylsulfonyl benzoic acid, with the molecular formula C8H7NO6S and a molecular weight of 245.21. It is a white or pale yellow crystalline powder at room temperature. Due to the importance of 2-nitro-4-methylsulfonylbenzoic acid, various methods for its preparation have been proposed both domestically and internationally. However, the most studied method is the oxidation of 2-nitro-4-methylsulfonyltoluene (NMST) to produce 2-nitro-4-methylsulfonylbenzoic acid.

[0004] The oxidation of 2-nitro-4-methylsulfonyltoluene with nitric acid in a mixed acid solvent (sulfuric acid and nitric acid) to produce 2-nitro-4-methylsulfonylbenzoic acid is the only method used in industrial production.

[0005]

[0006] This method has been reported in many documents, such as US 5424481A, 1995-06-13; Hebei Chemical Industry, 2005, 5:49-50; Hubei Agricultural Sciences, 2012, 51(5):924-926; Zhejiang Chemical Industry, 2012, 43(1):12-14; Journal of Zhejiang University of Technology, 2009, 37(3):267-271; CN103073461A, 2013. However, the nitric acid oxidation method consumes a large amount of nitric acid, generates nitrogen oxides, causes pollution, discharges a large amount of acidic wastewater, severely corrodes equipment, has low selectivity for the target product, and is costly, which does not meet the requirements of green development.

[0007] Some literature (WO2004058698A1, 2004-07-15; WO2007099450A2, 2007-07-09; CN101503383A, 2009; CN102584650A, 2012; Asian Journal of Chemistry, 2015, 27(10):3559-3563) reports the preparation of 2-nitro-4-methylsulfonylbenzoic acid by oxidation of 2-nitro-4-methylsulfonyltoluene with hydrogen peroxide:

[0008]

[0009] The hydrogen peroxide oxidation method has problems such as large wastewater volume, low selectivity, high cost, and significant safety hazards, and there are no industrial application examples.

[0010] Literature (Fine Chemical Intermediates, 2005, 35(2): 50-53; CN101921215A, 2010) reported the oxidation of 2-nitro-4-methylsulfonyl toluene to produce 2-nitro-4-methylsulfonyl benzoic acid in sulfuric acid with potassium permanganate as catalyst, with a yield of up to 80%. The reaction conditions are mild, the operation is safe and simple, and the investment is low. However, dichromates are expensive, the production cost is high, and a large amount of acidic waste liquid containing chromium and manganese is generated, which causes serious pollution.

[0011] Air (oxygen) is a clean and inexpensive oxidant. However, due to the weak oxidizing power of molecular oxygen, the development of highly efficient catalysts is crucial for the successful development of air (oxygen) oxidation technology. Patent US5591890 proposes using acetic acid as a solvent, cobalt acetate as a catalyst, and acetaldehyde as a promoter to oxidize 2-nitro-4-methylsulfonyl toluene with air to produce 2-nitro-4-methylsulfonylbenzoic acid.

[0012]

[0013] Patent CN102329256A uses metalloporphyrin as a catalyst to oxidize 2-nitro-4-methylsulfonyltoluene to 2-nitro-4-methylsulfonylbenzoic acid in a 0.5–2.0 mol / L NaOH methanol solution with oxygen at 1.0–2.0 MPa. Literature (CN104844484A; J.Chem.Sci.2017,129(10):1-8) uses methanol as a solvent, oxygen as an oxidant, and iron-titanium cyanide as a catalyst, reacting at 55 °C and 2.0 MPa for 8 h to oxidize 2-nitro-4-methylsulfonyltoluene to 2-nitro-4-methylsulfonylbenzoic acid. From a safety and economic perspective, methanol has a low boiling point, high price, and is prone to condensation reactions and partial oxidation, making it a dangerous solvent for oxidation reactions. Metalloporphyrins are very similar in properties to metal phthalocyanines, are expensive, have poor stability, are prone to self-polymerization or partial oxidation, and are difficult to recycle. 2-Nitro-4-methylsulfonylbenzoic acid has high solubility in methanol, resulting in low selectivity and increased separation costs. Patent CN 104557640A proposes dissolving 2-nitro-4-methylsulfonyltoluene in acetic acid, using cobalt and manganese salts as catalysts, nitric oxide radicals (N-hydroxyphthalimide and its analogues) as initiators, acetaldehyde as a promoter, and oxygen as an oxidant, to oxidize 2-nitro-4-methylsulfonyltoluene to produce 2-nitro-4-methylsulfonylbenzoic acid at 200℃ and 3.0 MPa. The product yield can reach over 70%, but this method produces products with many impurities and is difficult to separate. Patent CN2016108171892 uses a multi-component catalytic system consisting of heteropolyacid, metal oxide, and halogen to oxidize 2-nitro-4-methylsulfonyl toluene in air to produce 2-nitro-4-methylsulfonyl benzoic acid. Due to the use of expensive heteropolyacid as a catalyst, the concentration is high, resulting in high catalyst costs. Moreover, the presence of heteropolyacid and other catalyst components in the product leads to a high content of inorganic salts, requiring refining to meet requirements and increasing production costs. Summary of the Invention

[0014] The purpose of this invention is to provide a method for producing 2-nitro-4-methylsulfonyl toluene by air oxidation.

[0015] The technical problem to be solved by this invention is to provide a method for producing 2-nitro-4-methylsulfonyl toluene from 2-nitro-4-methylsulfonyl toluene. The method uses 2-nitro-4-methylsulfonyl toluene as raw material, air (oxygen-enriched air or oxygen) as oxidant, and an acidic aqueous solution as solvent. Under the action of a multi-component catalytic system composed of metal oxygen-containing compounds, metal ions or rare earth ions, and halogens, a gas-liquid two-phase reaction system is formed, oxidizing 2-nitro-4-methylsulfonyl toluene to 2-nitro-4-methylsulfonyl benzoic acid. This reduces equipment corrosion, minimizes environmental pollution, and achieves green production of 2-nitro-4-methylsulfonyl benzoic acid.

[0016] The concept of this invention is as follows:

[0017] Given that 2-nitro-4-methylsulfonyl toluene has two strong electron-withdrawing groups, the oxidation of the methyl group is extremely difficult. Therefore, this invention proposes to use a multi-component catalytic system composed of metal oxygen-metal ions or rare earth ions-halides to enhance catalytic activity by utilizing the synergistic effect between multiple components. In an acidic aqueous solution, 2-nitro-4-methylsulfonyl toluene is oxidized to 2-nitro-4-methylsulfonyl benzoic acid using a gas containing molecular oxygen (air, oxygen-enriched air, or oxygen).

[0018] The metal oxygen-containing compounds used are high-valence acidic oxides, or their corresponding acids or salts, selected from vanadium pentoxide, vanadic acid, vanadate, metavanadic acid, metavanadate, niobium pentoxide, niobic acid, niobate, tungstic acid, tungstate, molybdate, molybdate, chromic acid, chromate, dichromate, manganic acid, manganate, etc.

[0019] The metal ions or rare earth ions used are selected from one of the elements: iron, cobalt, zirconium, nickel, zinc, hafnium, titanium, cerium, lanthanum, europium, yttrium, praseodymium, samarium, and neodymium. The metal ion or rare earth ion source is derived from compounds soluble in solvents, such as acetates, nitrates, chlorides, carbonates, sulfates, oxides, and hydroxides.

[0020] The halides used are selected from tetrahaloethane, dihaloethane, haloethane, hydrogen halides, potassium halides, etc., with tetrahaloethane being preferred. The halogens include fluorine, chlorine, bromine, and iodine.

[0021] This invention is implemented in two steps:

[0022] (1) Catalytic oxidation of 2-nitro-4-methylsulfonyl toluene: A certain amount of metal oxygen-containing compound, metal or rare earth compound, halogen compound and 2-nitro-4-methylsulfonyl toluene, acid and water are put into a reactor. Under the protection of pressurized nitrogen, the reactor temperature is raised to a predetermined value. Then, oxygen-containing gas is continuously introduced under high pressure to oxidize 2-nitro-4-methylsulfonyl toluene to 2-nitro-4-methylsulfonyl benzoic acid.

[0023] The present invention does not have any special requirements for the heterogeneous catalytic oxidation reactor of 2-nitro-4-methylsulfonyl toluene, and can be carried out in a conventional bubble reactor.

[0024] The concentration of metal oxygen-containing compounds in the solvent inside the reactor is 0.01% to 0.1% (mass), with the optimal value being 0.005% to 0.05% (mass).

[0025] The concentration of metal ions in the solvent inside the reactor is 0.003–0.1% (mass), with the optimal value being 0.005%–0.05% (mass).

[0026] The content of halides in the solvent in the reactor is 0.005% to 0.08% (mass), with the optimal value being 0.003% to 0.03% (mass).

[0027] The oxidation reaction is carried out at a pressure of 4 to 50 atmospheres, with the optimal value being 5 to 15 atmospheres.

[0028] The oxidation reaction can be carried out at temperatures ranging from 100℃ to 300℃, with the optimal range being 120℃ to 200℃.

[0029] The concentration of 2-nitro-4-methylsulfonyl toluene in the reactor feed solvent is 5% to 65% (mass), with the optimal value being 15% to 50% (mass).

[0030] The inlet gas of the reactor is air, pure oxygen, or oxygen-enriched air, with air being preferred.

[0031] The solvent in the reactor is an acidic aqueous solution with a pH of 0.5-4.5, with the optimal pH being 1.0-2.5. The acids used are nitric acid, hydrochloric acid, sulfuric acid, and C1-C6 aliphatic carboxylic acids.

[0032] (2) Crystallization and reaction liquid circulation of 2-nitro-4-methylsulfonylbenzoic acid: After the reaction is completed and the temperature is lowered, the solubility of 2-nitro-4-methylsulfonylbenzoic acid is low at low temperature. The pale yellow precipitate obtained by crystallization is high-purity 2-nitro-4-methylsulfonylbenzoic acid. Solid-liquid separation is achieved by filtration. The obtained filtrate is replenished with acid to the predetermined pH value, and then 2-nitro-4-methylsulfonyltoluene is added. The solution is then put back into the reactor for catalytic oxidation to produce 2-nitro-4-methylsulfonylbenzoic acid.

[0033] This invention uses molecular oxygen as the oxidant and an acidic aqueous solution as the solvent. Under the action of a multi-element gas-liquid catalytic system composed of metal oxygen-metal ions or rare earth ions-halides, 2-nitro-4-methylsulfonyl toluene is oxidized to 2-nitro-4-methylsulfonyl benzoic acid. Compared with the nitric acid oxidation method, the catalyst, solvent, and unreacted raw materials can be recycled, significantly reducing acidic wastewater emissions, eliminating nitrogen oxide pollution, avoiding the generation of polynitrate impurities, increasing the yield of 2-nitro-4-methylsulfonyl benzoic acid, and reducing production costs. Compared with other molecular oxygen oxidation methods, it has high conversion rate, selectivity, and product purity, and the product does not require purification. Detailed Implementation

[0034] The present invention will be further described below with reference to embodiments, but these embodiments are not intended to limit the scope of the invention.

[0035] Example 1

[0036] The experiment was conducted in a 1000 ml stirred reactor. 660 ml of dilute sulfuric acid solution (pH 1.5) and 200 g of 2-nitro-4-methylsulfonyl toluene were added, along with 0.3 g of potassium permanganate, 0.5 g of ferrous sulfate heptahydrate, and 0.6 g of potassium iodide. The reaction temperature was 170 °C, the pressure was 13 atm, and the air flow rate was 900 ml / min. -1 After the reaction started, liquid samples were taken every 15 minutes for analysis by liquid chromatography. After 90 minutes of reaction, the conversion rate of 2-nitro-4-methylsulfonyl toluene reached 96.8%, and the yield of 2-nitro-4-methylsulfonyl benzoic acid reached 94.2%.

[0037] The reaction solution was cooled to 5°C, and the precipitate was separated from the reaction solution by filtration. 214.1 g of pale yellow 2-nitro-4-methylsulfonylbenzoic acid was crystallized and precipitated.

[0038] The resulting filtrate was adjusted to pH 1.5 and volume 660 ml with dilute sulfuric acid. Then, 200 g of 2-nitro-4-methylsulfonyl toluene was added, and the mixture was returned to the aforementioned reactor. The reactor was then heated at 170 °C, 13 atm, and an air flow rate of 900 ml / min. -1 Under the specified conditions, the reaction was carried out for 90 min, and liquid chromatography analysis showed that the conversion rate of 2-nitro-4-methylsulfonyl toluene was 96.1% and the yield of 2-nitro-4-methylsulfonyl benzoic acid was 93.8%.

[0039] Example 2

[0040] The experiment was conducted in a 900 ml reactor. The gas and liquid phases flowed continuously and in parallel from bottom to top through the reactor. The liquid flow rate was 10 ml / min, and the air flow rate was 900 ml / min. The liquid feed consisted of 25% (by weight) 2-nitro-4-methylsulfonyl toluene, 0.035% (by weight) potassium permanganate, 0.059% (by weight) ferrous sulfate heptahydrate, and 0.071% (by weight) iodine, with the remainder being dilute sulfuric acid at pH 1.5. The reaction temperature was 170 °C, and the pressure was 13 atm. The liquid at the reactor outlet was analyzed by liquid chromatography. The conversion rate of 2-nitro-4-methylsulfonyl toluene was 97.1%, and the yield of 2-nitro-4-methylsulfonyl benzoic acid was 95.2%.

[0041] Example 3

[0042] The experiment was conducted in a 1000 ml stirred reactor. 660 ml of pH 2.0 hydrochloric acid aqueous solution, 200 g of 2-nitro-4-methylsulfonyl toluene, 0.2 g of sodium metavanadate, 0.3 g of cobalt acetate, and 0.5 g of tetrabromoethane were added. The reaction temperature was 160 °C, the pressure was 8.0 atm, and the air flow rate was 900 ml / min. -1After the reaction started, liquid samples were taken every 15 minutes for analysis by liquid chromatography. After 90 minutes of reaction, the conversion rate of 2-nitro-4-methylsulfonyl toluene reached 99.1%, and the yield of 2-nitro-4-methylsulfonyl benzoic acid reached 97.2%.

[0043] The reaction solution was cooled to 5°C, and the precipitate was separated from the reaction solution by filtration to obtain 221.1 g of pale yellow 2-nitro-4-methylsulfonylbenzoic acid.

[0044] The resulting filtrate was diluted with hydrochloric acid and water to a volume of 660 ml and a pH of 2.0. Then, 200 g of 2-nitro-4-methylsulfonyl toluene was added, and the mixture was returned to the aforementioned reactor. The reactor was then heated at 160 °C, a pressure of 8.0 atm, and an air flow rate of 900 ml / min. -1 Under the specified conditions, samples were analyzed by liquid chromatography. After 90 min of reaction, the conversion rate of 2-nitro-4-methylsulfonyl toluene was 98.7%, and the yield of 2-nitro-4-methylsulfonyl benzoic acid was 96.9%.

[0045] Example 4

[0046] The experiment was conducted in a 1000 ml stirred reactor. 630 ml of pH 1.0 dilute acetic acid solution, 240 g of 2-nitro-4-methylsulfonyl toluene, 0.3 g of sodium dichromate, 0.4 g of zirconium acetate, and 0.4 g of hydrogen bromide were added. The reaction temperature was 160 °C, the pressure was 11.0 atm, and the air flow rate was 900 ml / min. -1 After the reaction started, liquid samples were taken every 15 minutes for analysis by liquid chromatography. After 90 minutes of reaction, the conversion rate of 2-nitro-4-methylsulfonyl toluene reached 98.2%, and the yield of 2-nitro-4-methylsulfonyl benzoic acid reached 96.7%.

[0047] The reaction solution was cooled to 5°C, and the precipitate was separated from the reaction solution by filtration to obtain 264.0 g of pale yellow 2-nitro-4-methylsulfonylbenzoic acid.

[0048] Acetic acid and water were added to the obtained filtrate to a volume of 630 ml and a pH of 1.0. Then, 240 g of 2-nitro-4-methylsulfonyl toluene was added, and the mixture was returned to the aforementioned reactor. The reactor was then heated at 160 °C, a pressure of 11.0 atm, and an air flow rate of 900 ml / min. -1 Under the specified conditions, the reaction was carried out for 90 min, and liquid chromatography analysis showed that the conversion rate of 2-nitro-4-methylsulfonyl toluene was 97.8% and the yield of 2-nitro-4-methylsulfonyl benzoic acid was 96.1%.

[0049] Example 5

[0050] The experiment was conducted in a 1000 ml stirred reactor. 630 ml of pH 1.0 dilute propionic acid solution, 240 g of 2-nitro-4-methylsulfonyl toluene, 0.3 g of sodium tungstate, 0.4 g of cerium nitrate, and 0.4 g of hydrogen bromide were added. The reaction temperature was 160 °C, the pressure was 10.0 atm, and the air flow rate was 900 ml / min. -1 After the reaction started, liquid samples were taken every 15 minutes for analysis by liquid chromatography. After 90 minutes of reaction, the conversion rate of 2-nitro-4-methylsulfonyl toluene reached 97.5%, and the yield of 2-nitro-4-methylsulfonyl benzoic acid reached 96.0%.

[0051] The reaction solution was cooled to 5°C, and the precipitate was separated from the reaction solution by filtration to obtain 262.2 g of pale yellow 2-nitro-4-methylsulfonylbenzoic acid.

[0052] The resulting filtrate was added with propionic acid and water to a volume of 630 ml and a pH of 1.0. Then, 240 g of 2-nitro-4-methylsulfonyl toluene was added, and the mixture was returned to the aforementioned reactor. The reactor was then heated at 160 °C, a pressure of 10.0 atm, and an air flow rate of 900 ml / min. -1 Under the specified conditions, the reaction was carried out for 90 min, and liquid chromatography analysis showed that the conversion rate of 2-nitro-4-methylsulfonyl toluene was 97.9% and the yield of 2-nitro-4-methylsulfonyl benzoic acid was 96.1%.

[0053] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing 2-nitro-4-methylsulfonylbenzoic acid, characterized in that, in In a reactor at 4–50 atmospheres and 100–300°C, using 2-nitro-4-methylsulfonyl toluene as raw material, air, oxygen-enriched air, or oxygen as oxidant, and acidic aqueous solution as solvent, a gas-liquid two-phase reaction system is formed under the action of a multi-component catalytic system composed of oxygen-containing compounds, metal ions, or rare earth ions and halogens, oxidizing 2-nitro-4-methylsulfonyl toluene to 2-nitro-4-methylsulfonyl benzoic acid; The mass concentration of the oxygen-containing compound is 0.01% to 0.1%; The mass concentration of metal ions or rare earth ions in the solvent within the reactor is 0.003–0.1%. The halogen mass concentration in the solvent within the reactor is 0.005–0.08%; The solvent contains 5% to 65% by mass of 2-nitro-4-methylsulfonyltoluene. The inlet gas of the reactor contains 21% to 100% oxygen by volume; The reaction solvent is an acidic aqueous solution with a pH of 0.1-4.5; The metal ions or rare earth ions mentioned are selected from iron, cobalt, zirconium, and cerium. The metal ion or rare earth ion source is derived from metal compounds that are soluble in solvents, including acetates, nitrates, chlorides, carbonates, sulfates, oxides, or hydroxides. The oxygen-containing compounds in the reactor are selected from high-valence acidic oxides or their corresponding acids or salts: metavanadate, metavanadate, dichromate or permanganate; The halogen is selected from tetrahaloethane, dihaloethane, haloethane, hydrogen halide, and potassium halide.

2. The method as described in claim 1, characterized in that: The mass concentration of oxygen-containing compounds in the reactor is 0.005–0.05%.

3. The method as described in claim 1, characterized in that: The mass concentration of halides in the solvent within the reactor is 0.003% to 0.03%.

4. The method according to claim 1, wherein the mass concentration of metal ions or rare earth ions in the solvent in the reactor is 0.005% to 0.05%.

5. The method as described in claim 1, characterized in that, The reaction pressure is 5 to 15 atmospheres, and the reaction temperature is 120°C to 200°C.

6. The method as described in claim 1, characterized in that, The liquid feed into the reactor contains 15% to 50% by weight of 2-nitro-4-methylsulfonyl toluene, and the inlet gas of the reactor is air.

7. The method as described in claim 1, characterized in that: The pH value of the solvent in the 2-nitro-4-methylsulfonyl toluene oxidation reactor is 0.5-2.5.

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