SEPARATING METHOD OF PROPYLENE GLYCOL DIESTER

1491661 Isolation of propylene glycol diesters BAYER AG and DEUTSCHE GOLDUND SILBER-SCHEIDEANSTALT 28 April 1976 [30 April 1975] 17180/76 Heading C2C The invention comprises a process for isolating a propylene glycol dicarboxylate from the reaction mixture produced in the preparation of propylene oxide by reaction of propylene with a solution of a percarboxylic acid in an organic solvent, the boiling point of which is lower than that of the carboxylic acid which corresponds to the percarboxylic acid, and higher than that of propylene oxide, and which mixture comprises propylene oxide, the carboxylic acid corresponding to the percarboxylic acid, one or more of the by-products propylene glycol, propylene glycol monocarboxylate and propylene glycol dicarboxylate, any unreacted propylene and organic solvent, the said process comprising separating the reaction mixture by distillation into a first fraction containing propylene oxide and propylene and a second fraction containing the carboxylic acid, one or more of the by-products and organic solvent, distilling the second fraction in a column at a pressure of from 1À5 to 6 bars with an average residence time in the sump sufficient to produce a sump product which comprises the carboxylic acid and the corresponding propylene glycol dicarboxylate, the organic solvent being removed as the top product, and separating the propylene glycol dicarboxylate from the sump product.