Method for producing particle size-controllable pharmaceutical-grade vitamin U based on cross-flow filtration

The invention discloses a particle size-controllable pharmaceutical-grade vitamin U production method based on cross-flow filtration, and belongs to the technical field of medical vitamin U production. The method comprises the following steps: S1, carrying out pressurized reaction on methionine and chloromethane at 53-60 DEG C to obtain a reaction solution A; s2, decolorizing and removing impurities from the reaction liquid A through activated carbon to obtain a decolorized liquid B; s3, evaporating and concentrating the decolored solution B under reduced pressure to obtain a crude product C; s4, mixing and pulping the crude product C and methanol to obtain a mixed solution D; s5, performing cross-flow filtration treatment on the mixed solution D to obtain a mixed solution E and a mixed solution F; s6, the mixed solution E and the mixed solution F are subjected to low-temperature standing, centrifugation, vacuum drying and smashing respectively, and the pharmaceutical-grade vitamin U with different particle s