PROCESS FOR ISOLATING PROPYLENE GLYCOL DIESTERS IN THE PREPARATION OF PROPYLENE OXIDE

摘要

PROCESS FOR ISOLATING PROPYLENE GLYCOL DIESTERSIN THE PREPARATION OF PROPYLENE OXIDEABSTRACT OF THE DISCLOSUREProcess for isolating propylene glycol dicarboxylates in thepreparation of propylene oxide by reaction of propylene witha solution of percarboxylic acid in an organic solvent, theboiling point of which is lower than that of the carboxylicacid which corresponds to the percarboxylic acid used as theepoxidising agent, and higher than that of propylene oxide,separation, by distillation, of the reaction mixture whichessentially contains propylene oxide, the carboxylic acidcorresponding to the percarboxylic acid used as the epoxi-dising agent and one or more of the by-products propylene-glycol, propylene glycol monocarboxylate and propylene glycoldicarboxylate as well as propylene and the organic solvent,into a fraction containing propylene oxide and propylene anda fraction containing the carboxylic acid, the by-productsmentioned and the organic solvent and further separation ofthesefractions into the individual components by distillation.The fraction containing the carboxylic acid, one ore more ofthe by-products propylene glycol, propylene glycol monocarboxy-late and propylene glycol dicarboxylate, and the organic solventis distilled in a column at pressures of 1.5 to 6 bars and withan average residence time of 10 to 90 minutes in the sump.The organic solvent is removed as the top product and thecarboxylic acid and the corresponding propylene glycol di-carboxylate is obtained as the sump product. From the sumpproduct the propylene glycol dicarboxylate is isolated in amanner which is in itself known.-1-