METHOD OF DISTILLATION OF CRUDE PHTHALIC ANHYDRIDE Russian patent published in 2019 - IPC C07D307/89 

FIELD: chemistry.

SUBSTANCE: invention relates to production of phthalic anhydride (PA). In particular, it concerns a method for distillation of crude PA. According to disclosed invention crude PA is directed into rectification column, in which reflux ratio is maintained from 1 to 7, still residue in production phthalic anhydride (SRPA) is fed into an apparatus for separating PA therefrom, wherein the process is carried out at temperature of 240 to 300 °C and residual pressure 13–20 kPa. PA vapors from device for its separation from SRPA is directed to rectification column, from which commercial high-quality PA is separated (Hazen chromaticity up to 13 units).

EFFECT: proposed method makes it possible to considerably simplify process scheme of distillation of crude FA (exclude condenser and vacuum system) and to obtain all commercial phthalic anhydride of high quality.

1 cl, 2 ex, 2 dwg