The invention relates to the technical field of synthesis of
chlorine-containing
pyridine intermediates, and discloses a preparation method of 3, 4, 5-trichloropyridine, which comprises the following steps: step 1, feeding: adding raw materials 2, 3, 4, 5-tetrachloropyridine, an acid-binding agent, a
solvent and a catalyst into a reaction kettle; 2, reaction preparation: sealing the reaction kettle, and replacing with
hydrogen to remove air; step 3, dechlorination reaction: heating to 60-150 DEG C, maintaining the pressure at 0.6-2.0 MPa, and reacting for 8-30 hours; 4, post-treatment: after the reaction is completed, cooling to
room temperature, and filtering reaction liquid to recover the catalyst; and 5, purification: distilling the filtrate to remove the
solvent, adding water, stirring, filtering to obtain a crude product, and recrystallizing to obtain the 3, 4, 5-trichloropyridine product. According to the invention, the dechlorination reaction is carried out in a
metal catalysis manner, the reaction steps are few, the used
reagent raw materials are fewer and milder, the danger in the reaction process is reduced, and the method is
safer; the reaction does not generate waste salt and is more environment-friendly; the catalyst can be recycled, so that the cost is reduced.