The invention aims to the field of
chemical engineering, and relates to a method for preparing L-
methionine. According to the method, acetylated
saponification liquid is used as production
raw material, acid is added into the
raw material, the pH is adjusted to be acidic, after reduced pressure
distillation, an
organic solvent is used for treatment, so that a solution containing D,L-acetyl
methionine is obtained, then the
organic solvent is removed to obtain D,L-acetyl
methionine crystals, and a resolution reaction is performed on the produced D,L-acetyl methionine crystals, so that the L-methionine is obtained; the technology does not need refined D,L-methionine, the soponification liquid for producing the D,L-methionine is used for performing an acetylated reaction, and therefore production cost is reduced; after the
acetylation, water is evaporated to
dryness, the
organic solvent is used for desalting, the yield of the D,L-acetyl methionine reaches 97-99%, and the purity of the D,L-acetyl methionine reaches above 96%; the enzymolysis speed of the D,L-acetyl methionine is higher than that of a traditional method, the obtained L-methionine is good in
crystal form and whiteness, the purity reaches above 99.5%, and the total yield of the L-methionine is improved to 78%; according to the technology, a circulation technology is integrated, the design is reasonable, and production cost is reduced.