In a 1000ml flask, add 450g chlorobenzene, 100g 2-chloro-5-methylpyridine, and 3g catalyst cobalt acetate under stirring, heat the system to 80℃, introduce oxygen, and control the oxygen flow rate at 0.4L/min. React under this condition for 4 hours. After the reaction, cool the system to room temperature, filter, and dry to obtain a mixture of 119g 6-chloronicotinic acid and cobalt acetate. Place those mentioned above mixed crude product in a 1000ml flask, add 600g of recrystallization solvent methanol, stir and heat to reflux; wait for the 6-chloronicotinic acid crude product to dissolve completely, keep warm for 5min, slowly cool the system to 5℃, precipitate a white product, maintain this internal temperature and continue stirring for 1 hour, filter, wash the filter cake once with a small amount of cooled methanol, and dry the obtained damp product at 80℃ for 4 hours to obtain 98.5g 6-chloronicotinic acid, purity 99.52% (HPLC), yield 79.7%.
