Method for preparing pyroxasulfone through continuous oxidation by using fixed bed catalyst

Abstract

The invention provides a method for preparing pyroxasulfone through continuous oxidation by using a fixed bed catalyst, which comprises the following steps: respectively pumping a compound of formula I and hydrogen peroxide into a fixed bed catalyst reactor for reaction, and purifying the reaction liquid after the reaction is completed to obtain pyroxasulfone. The fixed bed catalyst reactor internally comprises a tungsten-containing catalyst loaded by a nano titanium silicalite molecular sieve, the mass content of the nano titanium silicalite molecular sieve is 25%-50%, and the mass content of the tungsten-containing catalyst is 50%-75%. The fixed bed catalyst reactor is used, the reuse efficiency is high, and the catalyst cost is greatly reduced. The amount of hydrogen peroxide used for oxidation is only the theoretically required amount, no hydrogen peroxide is left after the reaction, and the risk of the oxidation reaction is greatly reduced. The method is simple in purification treatment, high in reaction yield and low in three-waste yield.

Description

Technical Field

[0001] The invention belongs to the technical field of herbicides, and specifically relates to a method for preparing pyraclostrobin by continuous oxidation using a fixed bed catalyst. Background Art

[0002] Pyroxasulfone is an isoxazole herbicide with the chemical name of 3-[5-(difluoromethoxy)-1-methyl-3-(trifluoromethyl)pyrazol-4-ylmethylsulfonyl]-4,5-dihydro-5,5-dimethyl-1,2-isoxazole, molecular formula of C12H14F5N3O4S, molecular weight of 391.32, and CAS registration number of 447399-55-5. Pyroxasulfone is mainly used as a pre-emergence sealing agent, mainly to kill broad-leaved grasses of the Poaceae family, and has many advantages: it is applicable to a wide range of crops, such as wheat, corn, peanuts, rice, soybeans, cotton, etc.; it is safe for the environment and for the current and next crops; and its effective period can reach about 28 days. Its structure is as follows: .

[0003] At present, the synthesis of sulfonepyraclostrobin mainly adopts a kettle reaction process. For example, the international patent US20120264947 discloses a synthesis method: using sodium tungstate dihydrate as a catalyst, oxidizing formula I at room temperature for 16 hours under hydrogen peroxide and acetic acid to obtain formula II. The shortcomings of this method are: (1) the overall reaction yield is low, about 30% to 35%; (2) hydrogen peroxide reacts with acetic acid to form peracetic acid, which increases the risk of the reaction system. At the same time, the post-treatment of excess peracetic acid is difficult and costly. Chinese patent CN118255757A provides a continuous synthesis method for sulfonepyraclostrobin: 57% acetonitrile solvent of intermediate I, 14% sodium tungstate solution and 30% hydrogen peroxide solution are kept in a reactor at 50-60°C for 180 minutes to obtain formula II, with a purity of 99.7% and a yield of 93.6%. The shortcomings of this method are: (1) there is an excess of hydrogen peroxide in the reaction system, and sodium sulfite is used to quench the reaction, which increases the types of by-product salts in the reaction system; (2) the purification process is complicated, and after quenching the hydrogen peroxide, continuous separation, water washing, concentration and crystallization, pulping purification and drying are required to obtain a qualified product. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing sulfonepyraclostrobin by continuous oxidation using a fixed bed catalyst, so as to solve the problems of high reaction risk, complex purification process and difficulty in catalyst recovery in the existing process, and to be more suitable for industrial production.

[0005] Technical Solutions A method for preparing sulfonepyraclostrobin by continuous oxidation using a fixed bed catalyst, the reaction formula is as follows, the compound of formula I and hydrogen peroxide are pumped into a fixed bed catalyst reactor for reaction, and the reaction liquid after the reaction is purified to obtain sulfonepyraclostrobin, the reaction formula is as follows, .

[0006] Before the reaction, the compound of formula I is dissolved in a solvent, and the solvent includes a C1-C3 alcohol solution.

[0007] The injection concentration of the hydrogen peroxide is 15% to 50%.

[0008] The molar ratio of the compound of formula I to hydrogen peroxide is 1:2-3.

[0009] The fixed bed catalyst reactor comprises a nano titanium silicon molecular sieve carrier and a tungsten-containing catalyst, wherein the mass content of the nano titanium silicon molecular sieve is 90% to 99.5%, and the mass content of the tungsten-containing catalyst is 0.5% to 10%.

[0010] The tungsten-containing catalyst is selected from tetrabutylammonium decatungstate.

[0011] In the technical scheme of the present invention, the preparation method of the tungsten-containing catalyst loaded with nano-titanium silicon molecular sieve is to add water to the tungsten-containing catalyst and stir evenly, then add the titanium silicon molecular sieve, stir and mix evenly, spin dry or evaporate the water, and then calcine at 400-600°C to obtain the product.

[0012] Tungsten catalysts can be used as both acidic and oxidative catalysts, and are widely used in the fields of fine chemicals and environmental protection. Because of its unique acidity, which is stronger than that of general solid acid catalysts such as SiO2-Al2O3 and molecular sieves, and its special solubility, it can be used as both a homogeneous catalyst and a heterogeneous catalyst. It has high activity and selectivity, good reproducibility, no corrosion to equipment, and simple post-processing. Tetrabutylammonium decatungstate is a type of tungsten catalyst. It has low solubility in water, but can be dissolved in alcohols and esters. In an organic solvent system, it is convenient for the catalyst to be separated, recovered and reused, and the catalytic activity remains unchanged after multiple uses.

[0013] The reaction residence time in the fixed bed catalyst reactor is 15-30 minutes, the reaction temperature is 50-60° C. and the reaction system pressure is 0.1 MPa-1.0 MPa.

[0014] The purification process includes cooling, filtering and drying.

[0015] Technical Effects Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses a fixed bed catalyst reactor, which has high reuse efficiency and greatly reduces the catalyst cost.

[0016] (2) The hydrogen peroxide used in the oxidation process of the present invention is only the theoretically required amount, and no hydrogen peroxide remains after the reaction, thereby greatly reducing the risk of the oxidation reaction.

[0017] (3) The purification process of the present invention is simple, the reaction yield is high, and the output of three wastes is small. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is described clearly and completely. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0019] Example 1 Preparation of 0.5% tetrabutylammonium decatungstate fixed bed catalyst reactor: Weigh 10.5g tetrabutylammonium decatungstate, add 100g water, stir at room temperature for 30min, add 150g TS-1, stir for 60min, transfer to a crucible, evaporate water at 80℃, calcine the sample at 400℃ for 180min, and obtain the target catalyst, which is sieved and filled into a fixed bed reactor. Pump a 16wt% methanol solution of formula I and 30wt% hydrogen peroxide into the fixed bed catalyst reactor, respectively, wherein the flow rate of the 16wt% methanol solution of formula I is 2mL / min, and the flow rate of the 30wt% hydrogen peroxide is 0.139mL / min, react at 55℃, residence time is 18.7min, system back pressure is 0.4MPa, after cooling, filter, dry the upper solid to obtain sulfone pyrazoline, the yield is 80%, and the liquid phase purity is 87%. The filtrate was subjected to reduced pressure distillation to remove methanol, and the tungsten catalyst tetrabutylammonium decatungstate was precipitated in water, filtered, and dried to obtain tetrabutylammonium decatungstate. Repeat the preparation steps of 0.5% tetrabutylammonium decatungstate fixed bed catalyst, and the catalytic activity remained unchanged after more than four times, with a yield of 78% and a liquid phase purity of 86%; the catalyst recovery rate was about 80%.

[0020] Example 2 The fixed bed catalyst reactor is prepared in the same manner as in Example 1, wherein a 16wt% methanol solution of Formula I and 35wt% hydrogen peroxide are pumped into the fixed bed catalyst reactor simultaneously, wherein the flow rate of the 16wt% methanol solution of Formula I is 2mL / min, and the flow rate of the 35wt% hydrogen peroxide is 0.119mL / min, and the reaction is carried out at 60°C, the residence time is 26min, and the system back pressure is 0.8MPa. After cooling, the reaction is carried out, and the upper solid is dried to obtain sulfonepyrazoline, with a yield of 89.0% and a liquid phase purity of 99.0%. After the 0.5% tetrabutylammonium decatungstate fixed bed catalyst reactor is reused four times, the average yield of sulfonepyrazoline is about 91.0%, the average liquid phase purity is 98.0%, and the catalyst recovery rate is about 88%.

[0021] Example 3 Preparation of 1% tetrabutylammonium decatungstate fixed bed catalyst reactor: Weigh 21g tetrabutylammonium decatungstate, add 100g water, stir at room temperature for 30min, add 150g TS-1, stir for 60min, transfer to a crucible, evaporate water at 80℃, calcine the sample at 400℃ for 180min, and obtain the target catalyst. After sieving, fill it into a fixed bed reactor, pump 16wt% methanol solution of formula I and 30wt% hydrogen peroxide into the fixed bed catalyst reactor, wherein the flow rate of 16wt% methanol solution of formula I is 2mL / min, and the flow rate of 30wt% hydrogen peroxide is 0.139mL / min, react at 55℃, residence time is 18.7min, system back pressure is 0.4MPa, filter after cooling, dry the upper solid to obtain sulfone pyrazoline, the yield is 94%, and the liquid phase purity is 99%. After the 1% tetrabutylammonium decatungstate fixed bed catalyst reactor was reused four times, the average yield of sulfonepyraclostrobin was about 97%, the average liquid phase purity was greater than 98%; and the catalyst recovery rate was about 83%. Comparative Example 1 Preparation of 5% tungsten oxide fixed bed catalyst reactor: Weigh 9.5g tungsten oxide, add 100g water, stir at room temperature for 30min, add 150g TS-1, stir for 60min, transfer to a crucible, evaporate water at 80℃, calcine the sample at 400℃ for 180min, and obtain the target catalyst. After sieving, fill it into a fixed bed reactor, pump a 16wt% methanol solution of formula I and 30wt% hydrogen peroxide into the fixed bed catalyst reactor, wherein the flow rate of the 16wt% methanol solution of formula I is 2mL / min, and the flow rate of the 30wt% hydrogen peroxide is 0.139mL / min, react at 55℃, residence time is 18.7min, system back pressure is 0.4MPa, filter after cooling, dry the upper solid to obtain sulfone pyrazoline, the yield is 43%, and the liquid phase purity is greater than 98%. The filtrate was distilled under reduced pressure to remove methanol, 30 g of ethyl acetate was added to the mother liquor, filtered, and the solid was dried to obtain tungsten oxide. The preparation steps of 50% tungsten oxide fixed bed catalyst were repeated four times, and the yield of sulfonepyraclostrobin was 46%, the liquid phase purity was greater than 98%, and the recovery rate of tungsten oxide was about 94%.

[0022] Comparative Example 2 Preparation of 7.5% sodium tungstate fixed bed catalyst reactor: weigh 20.1g sodium tungstate dihydrate, add 100g water, stir at room temperature for 30min, add 150g TS-1, stir for 60min, transfer to a crucible, evaporate water at 80℃, calcine the sample at 400℃ for 180min, and obtain the target catalyst. After sieving, fill it into a fixed bed reactor, and pump a 16wt% methanol solution of formula I and 35wt% hydrogen peroxide into the fixed bed catalyst reactor at the same time, wherein the flow rate of the 16wt% methanol solution of formula I is 2mL / min, and the flow rate of the 35wt% hydrogen peroxide is 0.119mL / min, react at 60℃, residence time is 26min, and the system back pressure is 0.8MPa. After cooling, filter, dry the upper solid to obtain sulfone pyrazoline, with a yield of 91% and a liquid phase purity greater than 98%. The filtrate was subjected to reduced pressure distillation to remove methanol to obtain a sodium tungstate aqueous solution, which was evaporated and crystallized to obtain a sodium tungstate solid. The previous sodium tungstate fixed bed catalyst preparation steps were repeated. After three uses, the catalytic activity decreased, the sulfone pyrazoline yield was 93%, the liquid phase purity was 78%, and the sodium tungstate catalyst recovery rate was about 64%.

Claims

1. A method for preparing sulfonepyraclostrobin by continuous oxidation using a fixed bed catalyst, characterized in that: The compound of formula I and hydrogen peroxide are pumped into a fixed bed catalyst reactor for reaction. After the reaction, the reaction liquid is purified to obtain sulfonepyraclostrobin. The reaction formula is as follows: 。 2. The method according to claim 1, characterized in that The compound of formula I is dissolved in a solvent, and the solvent includes a C1-C3 alcohol solution.

3. The method according to claim 2, characterized in that The injection concentration of hydrogen peroxide is 15%~50%.

4. The method according to claim 3, characterized in that The molar ratio of formula I to hydrogen peroxide is 1:2-3.

5. The method according to claim 1, characterized in that The fixed bed catalyst reactor comprises a tungsten-containing catalyst supported by a nano-titanium silicon molecular sieve, wherein the mass content of the nano-titanium silicon molecular sieve is 90% to 99.5%, and the mass content of the tungsten-containing catalyst is 0.5% to 10%.

6. The method according to claim 5, characterized in that The tungsten-containing catalyst is tetrabutylammonium decatungstate.

7. The method according to claim 1, characterized in that The reaction residence time in the fixed bed catalyst reactor is 15-30 minutes; the reaction temperature is 50-60°C.

8. The method according to claim 1, characterized in that The reaction system pressure is 0.1MPa~1.0MPa.

9. The method according to claim 1, characterized in that: The purification process includes cooling, filtering and drying.

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