A method for preparing 2,6-diaminopyridine, which is characterized in that the preparation method comprises: heating sodium amide, an organic solvent and a phase transfer catalyst to 140-220°C to keep warm, adding pyridine dropwise within 0.5-3 hours, Carry out Chichibabin reaction for 3-10 hours, the reaction is complete, cool down to 50-100°C, add water to carry out hydrolysis reaction at 30-100°C, cool, crystallize at 5-40°C, and filter to obtain the 2,6-diaminopyridine , the phase transfer catalyst is C6～C9 aromatic amine or C2～C6 fatty alcohol amine or a mixture of both, and the described organic solvent is C8～C12 chain hydrocarbon or aromatic hydrocarbon or diphenyl ether, so The substance ratio of the sodium amide and pyridine is 2.0～4.0:1.0, the substance ratio of the phase transfer catalyst and pyridine is 0.5～3.0:1.0, and the quality of the organic solvent is 1% of the pyridine mass. ～4 times, the quality of the water is 3～10 times of the quality of pyridine.
The organic solvent and phase transfer catalyst can be recycled.
The phase transfer catalyst is C6-C9 aromatic amine and/or C2-C6 fatty alcohol amine, that is, C6-C9 aromatic amine, such as aniline, N,N-dimethylaniline, p-methylaniline, O-methylaniline, 2,4,6-trimethylaniline, etc., can also be C2～C6 fatty alcohol amines, such as ethanolamine, propanolamine, butanolamine, diethanolamine, triethanolamine, etc., or C6 A mixture of ~C9 aromatic amine and C2~C6 fatty alcohol amine, C6~C9 aromatic amine and C6~C9 aromatic amine or C2~C6 fatty alcohol amine and C2~C6 fatty alcohol amine; the said The organic solvent is C8～C12 chain hydrocarbon or aromatic hydrocarbon or diphenyl ether, such as nonane, decane, dodecane, decahydronaphthalene, tetrahydronaphthalene, diphenyl ether, etc.; the sodium amide and pyridine The molar ratio of the substance is 2.0～4.0:1.0, preferably 2.5～3.0:1.0, the molar ratio of the phase transfer catalyst and pyridine is 0.5～3.0:1.0, preferably 0.5～1.0:1.0; The quality of the organic solvent is 1 to 4 times of the quality of pyridine, preferably 1.5 to 2.5 times; the quality of the water is 3 to 10 times of the quality of pyridine, preferably 5.0 to 7.0 times. The time for adding pyridine is preferably 1 to 2 hours; the Chichibabin reaction time is preferably 3 to 6 hours, and the reaction temperature is preferably 150 to 180°C; the hydrolysis reaction temperature is preferably 50 to 80°C; the crystallization temperature is 5 to 40°C , preferably 18-28°C.
