Method for continuously preparing tribenuron-methyl

Abstract

The invention discloses a method for continuously preparing tribenuron-methyl, which comprises the following steps: carrying out phosgenation reaction on o-methyl formate benzenesulfonamide and triphosgene in a dynamic reactor and a tubular reactor to obtain o-methyl formate benzenesulfonyl isocyanate; and carrying out condensation reaction on o-methyl formate benzenesulfonyl isocyanate and 2-methyl-4-methylamino-6-methoxyl-s-triazine in a common reaction kettle to obtain tribenuron-methyl, wherein methyl formate benzenesulfonyl isocyanate and 2-methyl-4-methylamino-6-methoxyl-s-triazine are used as raw materials; the reaction temperature in the dynamic reactor is 100 to 150 DEG C, the reaction pressure is 0.1 to 0.5 MPa, and the reaction time is 30 to 100 minutes; the reaction temperature in the tubular reactor is 120 to 180 DEG C, the reaction pressure in the tubular reactor is 0.1 to 0.5 MPa, and the reaction time in the tubular reactor is 30 to 100 minutes. The phosgenation reaction is carried out by adopting the dynamic reactor and the tubular reactor, on one hand, continuous feeding and discharging can be carried out, so that materials in the reactors are less, the risk of the phosgenation reaction is greatly reduced, on the other hand, the reaction time is short, the risk of the phosgenation reaction is further reduced, and the method is more suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of herbicide preparation, and particularly relates to a method for continuously preparing bensulfuron-methyl. Background Art

[0002] Bensulfuron-methyl (common name: tribenuron-methyl) is a sulfonylurea herbicide for wheat fields developed by DuPont. Bensulfuron-methyl is an important wheat field broadleaf weed herbicide with high efficiency, broad spectrum, low toxicity and high selectivity. It is mainly used to control various annual broadleaf weeds, and has good effects on Artemisia selengensis, Shepherd's purse, Cardamine, Trichosanthes kirilowii, Chenopodium album, Amaranthus retroflexus, etc. It also has a certain control effect on Kochia scoparia, Chickweed, Polygonum aviculare, and Glechoma longituba.

[0003] At present, the conventional synthesis route of bensulfuron-methyl is to use methyl benzenesulfonamide as the starting material, firstly react with triphosgene [see Chinese patent documents CN102391194A, CN116514688A, CN116640099A] to obtain an isocyanate intermediate, and then react with 2-methyl-4-methylamino-6-methoxy-s-triazine to obtain bensulfuron-methyl.

[0004] The synthetic route is as follows: .

[0005] The existing phosgenation reaction is carried out in an ordinary reactor. Due to the poor solubility of methyl benzenesulfonamide, it needs a higher temperature to dissolve in xylene. When the intermittent phosgenation reaction is carried out at a higher temperature, phosgene leakage is inevitable, which not only poses a great safety hazard, but also causes a waste of raw materials. In addition, the phosgenation process is one of the hazardous chemical processes that are subject to key national supervision. The existing phosgenation reaction time is relatively long, which further increases the safety hazard. Summary of the invention

[0006] The object of the present invention is to solve the above problems and provide a method for continuously preparing bensulfuron-methyl with less reaction materials, shorter reaction time and higher reaction safety.

[0007] The technical solution for achieving the purpose of the present invention is: a method for continuously preparing bensulfuron-methyl, comprising the following steps: S1, methyl benzenesulfonamide and triphosgene are subjected to phosgenation reaction in a dynamic reactor and a tubular reactor to obtain methyl benzenesulfonyl isocyanate; S2, methyl o-formylbenzenesulfonyl isocyanate and 2-methyl-4-methylamino-6-methoxy-s-triazine are subjected to condensation reaction in a common reactor to obtain bensulfuron-methyl.

[0008] In the above step S1, the reaction temperature in the dynamic reactor is 100-150°C, preferably 130°C.

[0009] In the above step S1, the reaction pressure in the dynamic reactor is 0.1-0.5 MPa, preferably 0.3 MPa.

[0010] In the above step S1, the reaction time in the dynamic reactor is 30 to 100 minutes, preferably 50 minutes.

[0011] In the above step S1, the reaction temperature in the tubular reactor is 120-180°C, preferably 150°C.

[0012] In the above step S1, the reaction pressure in the dynamic reactor is 0.1-0.5 MPa, preferably 0.3 MPa.

[0013] In the above step S1, the reaction time in the dynamic reactor is 30 to 100 minutes, preferably 50 minutes.

[0014] In the above step S1, the phosgenation reaction is carried out in the presence of a catalyst; the catalyst is preferably n-butyl isocyanate.

[0015] In the above step S1, the phosgenation reaction is carried out in a first solvent; the first solvent is preferably xylene.

[0016] In the above step S2, the condensation reaction is carried out in a second solvent; the second solvent is preferably dichloromethane.

[0017] In the above step S2, the condensation reaction temperature is the reflux temperature, and the condensation reaction time is 1 to 2 hours.

[0018] The present invention has the positive effects: the present invention adopts a dynamic reactor and a tubular reactor to carry out the phosgenation reaction, which can continuously feed and discharge materials, thereby reducing the amount of materials in the reactor and greatly reducing the danger of the phosgenation reaction; on the other hand, the reaction time is also short, further reducing the danger of the phosgenation reaction, and is more suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a schematic diagram of a device for continuously preparing bensulfuron-methyl. DETAILED DESCRIPTION

[0020] The dynamic tubular reactor used in the present invention is a dynamic tubular reactor of Philip Chemical Engineering (Suichang) Co., Ltd. The material of its mixed reaction module is 316L and Hastelloy, the liquid holding capacity is 2000mL, and the liquid material feeding method of the dynamic tubular reactor is a plunger pump driven continuous feeding. The reactor itself includes a reaction unit, a pressure stabilizing heat exchange unit and a control unit. In the actual application process, it is also necessary to coordinate a material control system, a temperature control system, a gas control system and a material collection back pressure system.

[0021] (Example 1) The method for continuously preparing bensulfuron-methyl in this embodiment comprises the following steps: S1, methyl benzenesulfonamide and triphosgene are subjected to phosgenation reaction in a dynamic reactor and a tubular reactor to obtain methyl benzenesulfonyl isocyanate.

[0022] S11. At room temperature, add 652 g (2.2 mol) of triphosgene and 2716 g of xylene into glass kettle 1, stir to dissolve, and obtain a mixed solution.

[0023] S12. At room temperature, add 1400 g (6.5 mol) of methyl benzenesulfonamide, 336 g (3.38 mol) of n-butyl isocyanate and 5000 g of xylene into the glass kettle 2, stir and mix well to obtain a mixed suspension B.

[0024] S13, controlling the temperature of the dynamic reactor 3 at 130° C., and the temperature of the tubular reactor 4 at 150° C., and then introducing nitrogen to make the pressures in the dynamic reactor 3 and the tubular reactor 4 both 0.3 MPa.

[0025] S14, the mixed liquid A is pumped into the dynamic reactor 3 through the first plunger pump 11, and the feeding rate of the first plunger pump 11 is 13g / min; the mixed suspension B is pumped into the dynamic reactor 3 through the second plunger pump 21, and the feeding rate of the second plunger pump 21 is 26g / min; after the material reacts in the dynamic reactor 3 for 50min, it enters the tubular reactor 4 and continues to react for 50min.

[0026] S15. After the reaction is completed, the material is introduced into a distillation kettle 5 and distilled under reduced pressure (temperature of about 100°C, vacuum degree of more than -0.95MPa). The distilled xylene and n-butyl isocyanate are recovered and reused. The generated acidic hydrogen chloride gas is treated by a tail gas absorption system. The methyl benzenesulfonyl isocyanate in the distillation kettle 5 is cooled to below 40°C and set aside.

[0027] S2, methyl o-formylbenzenesulfonyl isocyanate and 2-methyl-4-methylamino-6-methoxy-s-triazine are subjected to condensation reaction in a common reactor to obtain bensulfuron-methyl.

[0028] The methyl benzenesulfonyl isocyanate obtained in step S1 was added to a common reaction kettle, and then 2500 g of dichloromethane and 1000 g (6.5 mol) of 2-methyl-4-methylamino-6-methoxy-s-triazine were added. The temperature was raised to reflux for reaction for 1 hour, and the reaction was monitored by HPLC until completion.

[0029] After the reaction, dichloromethane was distilled under reduced pressure at a temperature not exceeding 40°C. After the distillation, the temperature was lowered to below 10°C, methanol was added to the material, stirred for 20 min, filtered at about 10°C, rinsed with methanol, and dried below 45°C to obtain 2184 g of bensulfuron-methyl with a yield of 84.9% and a purity of 98.3% (HPLC).

[0030] (Example 2 to Example 3) The preparation methods of each embodiment are basically the same as that of embodiment 1, and the differences are shown in Table 1.

[0031] Table 1 Example 1 Example 2 Example 3 Dynamic reactor temperature 130℃ 110℃ 150℃ Dynamic reactor pressure 0.3MPa 0.2MPa 0.5MPa Dynamic reactor time 50min 70min 30min Tubular reactor temperature 150℃ 130℃ 180℃ Tubular reactor pressure 0.3MPa 0.2MPa 0.5MPa Tubular reactor time 50min 70min 30min weight 2184g 2168g 2202g Yield 84.9% 83.9% 85.6% purity 98.3% 98.5% 98.2%

Claims

1. A method for continuously preparing bensulfuron-methyl, comprising the following steps: S1, methyl benzenesulfonamide and triphosgene are subjected to phosgenation reaction in a dynamic reactor and a tubular reactor to obtain methyl benzenesulfonyl isocyanate; S2, methyl o-formylbenzenesulfonyl isocyanate and 2-methyl-4-methylamino-6-methoxy-s-triazine are subjected to condensation reaction in a common reactor to obtain bensulfuron-methyl.

2. The method for continuously preparing bensulfuron-methyl according to claim 1, characterized in that: In the above step S1, the reaction temperature in the dynamic reactor is 100-150° C., the reaction pressure is 0.1-0.5 MPa, and the reaction time is 30-100 min.

3. The method for continuously preparing bensulfuron-methyl according to claim 2, characterized in that: In the above step S1, the reaction temperature in the dynamic reactor is 130° C., the reaction pressure is 0.3 MPa, and the reaction time is 50 min.

4. The method for continuously preparing bensulfuron-methyl according to claim 1, characterized in that: In the above step S1, the reaction temperature in the tubular reactor is 120-180° C., the reaction pressure is 0.1-0.5 MPa, and the reaction time is 30-100 min.

5. The method for continuously preparing bensulfuron-methyl according to claim 4, characterized in that: In the above step S1, the reaction temperature in the tubular reactor is 150° C., the reaction pressure is 0.3 MPa, and the reaction time is 50 min.

6. The method for continuously preparing bensulfuron-methyl according to claim 1, characterized in that: In the above step S1, the phosgenation reaction is carried out in the presence of a catalyst; the catalyst is preferably n-butyl isocyanate.

7. The method for continuously preparing bensulfuron-methyl according to claim 1, characterized in that: In the above step S1, the phosgenation reaction is carried out in a first solvent; the first solvent is preferably xylene.

8. The method for continuously preparing bensulfuron-methyl according to claim 1, characterized in that: In the above step S2, the condensation reaction is carried out in a second solvent; the second solvent is preferably dichloromethane.

9. The method for continuously preparing bensulfuron-methyl according to claim 1, characterized in that: In the above step S2, the condensation reaction temperature is the reflux temperature, and the condensation reaction time is 1 to 2 hours.

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