Aluminum magnesium carbonatePreparation background and overview of 5-nitro-2,3-dichloropyridine
5-Nitro-2,3-dichloropyridine is an important fine chemical intermediate and is widely used in the fields of medicine and pesticides. 2,3-Dichloropyridine is a key intermediate of the new insecticide chlorantraniliprole. Suitable for resistance management and comprehensive pest control; broad spectrum, high efficiency, low toxicity, low residue, and environmentally friendly are the development directions of new pesticides in the 21st century; the various excellent characteristics of chlorantraniliprole indicate that it will become a traditional insecticide An important substitute for pesticides, this type of pesticide will play an important role in the agricultural field, and it is estimated that it may reach 300 million US dollars at its peak; although chlorantraniliprole has different synthesis routes, they are all based on 5- Nitro-2,3-dichloropyridine is used as a raw material. Since there is no mature industrial production process, there is no large-scale production at home and abroad. As a result, 5-nitro-2,3-dichloropyridine is expensive and has greatly increased the price. Chlorantraniliprole production costs.
5-nitro-2,3-dichloropyridine
Preparation of 5-nitro-2,3-dichloropyridine
(1) Chlorination reaction process: Continuously add the catalyst FeCl3 and 2,6-dichloropyridine into the dissolving kettle, and after mixing, overflow to the chlorination kettle for chlorination. The 5-nitro-2,6-dichloropyridine with FeCl3 dissolved in it overflows in the order of chlorination kettles A-D, and chlorine gas flows in the reverse order of chlorination kettles D-A to perform the chlorination reaction. The temperature is 195°C, and the chlorine gas is not excessive during the reaction. ; The reacted chlorinated material (5-nitro-dichloropyridine and 5-nitro-trichloropyridine liquid) liquid material enters rough distillation, and the distillate enters the rectification tower for distillation and separation, and the front fraction 5- Nitro-dichloropyridine is returned to the chlorination kettle, and the final distillate is 5-nitro-2,3,6-trichloropyridine. The crude distillation residue and rectification residue are tar, which are treated as solid waste of methylpyridine; chlorine The chemical exhaust gas undergoes two-stage falling film absorption and two-stage alkali absorption to produce hydrochloric acid and sodium hypochlorite as by-products, and is then emptied through a 30m-high exhaust stack outside the workshop.
(2) Hydrogenation reaction process: Put 5-nitro-2,3,6-trichloropyridine, ethanol, triethylamine and catalyst into the reaction kettle, turn on stirring and jacketed hot water, and heat up to reaction Temperature, the reaction temperature is 30-50°C, and the pressure is 0-0.5mpa; replace the air in the kettle with nitrogen, open the hydrogen valve, and pass in hydrogen until the end of the reaction is reached, close the hydrogen valve, and stop passing hydrogen;
(3) Filtration: Replace the hydrogen in the reaction kettle of step (2) with nitrogen, turn on the bottom pump of the kettle, filter the material, use the filter cake as a catalyst, wash it with a small amount of toluene and then wash it with a small amount of water, and apply it to the next batch Catalyst, the filtrate is transferred to the ethanol recovery kettle;
(4) Ethanol recovery: Turn on the jacket steam and stirring of the ethanol recovery kettle, turn on the cooling water of the condenser, and recover ethanol at normal pressure. After there is no flow in the condenser, turn off the jacket steam and add cleaning water and toluene to the kettle. , keep warm and stir for 30 minutes, stop stirring, let stand for 30 minutes, start stratification, put the lower water layer into the triethylamine recovery kettle, and the upper toluene layer into the extraction kettle;
(5) Triethylamine recovery: The water layer enters the triethylamine recovery kettle, adds alkali aqueous solution to neutralize it to neutrality, separates the oil layer, separates the lower oil layer and goes to the 3-pyridine distillation kettle; open the triethylamine recovery kettle clip Jacket steam and stir, turn on the cooling water of the condenser, recover triethylamine under normal pressure, wait until there is no flow in the condenser, turn off the jacket steam, cool, and send the residual liquid to the wastewater station;
(6) Extraction: Add concentrated hydrochloric acid to the extraction kettle three times for extraction, stir for 30 minutes, let stand for 30 minutes, then separate the liquids, collect the lower hydrochloric acid layer and remove the water from the precipitation kettle;
(7) Toluene recovery: The upper toluene layer enters the toluene recovery kettle, adds alkali aqueous solution to neutralize it to neutrality, separates the water layer and goes to the wastewater station, turns on the steam and stirring of the jacket of the toluene recovery kettle, turns on the cooling water of the condenser, Recover toluene under normal pressure. After there is no flow in the condenser, close the jacket steam, cool the residual liquid, add recovered ethanol, stir evenly, cool to normal temperature, and transfer to the hydrogenation kettle;
(8) Water separation centrifugation: The extracted hydrochloric acid layer enters the water separation kettle, adds water, stirs for 30 minutes, and then suction filtration. The filter cake is the product, namely 5-nitro-2,3-dichloropyridine, which is passed through the centrifuge. After high-speed centrifugal dehydration, it is naturally dried and packaged.
Preparation and purification method of 5-nitro-2,3-dichloropyridine
1). Add 100g of crude 5-nitro-2,3-dichloropyridine into the reaction kettle (the crude product contains 95wt% of 2,3-dichloropyridine and the rest is 2,3,6-trichloro Pyridine), that is, the crude product contains 0.64 mol 5-nitro-2,3-dichloropyridine; add 80 ml of 36.5 wt% concentrated hydrochloric acid (0.96 mol HCl), heat to 80°C with stirring, react for 30 minutes, and separate the liquids while hot. An oil phase and an aqueous phase are obtained.
2), take the water phase obtained in step 1), first add about 90ml of alkali solution (30wt% sodium hydroxide solution) until the pH is 10;
Then heat to boiling, perform steam distillation, collect fractions (100-103°C fractions), stop distillation when no more solids precipitate after the fractions cool to room temperature. The fraction was filtered, and the filter cake was vacuum dried at 30°C to a constant weight to obtain 90g of refined 5-nitro-2,3-dichloropyridine, with a recovery rate of 94.3% and a purity of 99.5wt%.
