Dimethyl phosphite purification method

The invention discloses a dimethyl phosphite purification method. The method comprises the following steps: 1, adding methanol and phosphorus trichloride into a reaction kettle according to a molar ratio of (3-3.2):(1-1.1), mixing the methanol and the phosphorus trichloride, and carrying out an esterification reaction to obtain crude dimethyl phosphite; 2, adding pure water to the crude dimethyl phosphite, heating the pure water and the crude dimethyl phosphite to 80 DEG C, introducing ammonia gas after the crude dimethyl phosphite solid is completely dissolved, stirring the obtained solution, and stopping the introduction of the ammonia gas when the pH value of the solution is 7.0; 3, sending a material obtained in step 2 into a rectifying tower having 32 trays, and completely distilling the dimethyl phosphite at 150 DEG C under 0.3-0.5 kpa; and 4, decolorizing the distilled dimethyl phosphite obtained in step 3 by using active carbon, and filtering the decolorized dimethyl phosphite to obtain highly pure di