Dehydration of Acetic Acid by Axeotropic Distillation in the Production of an Aromatic Acid

摘要

In a process for preparing an aromatic dicarboxylic acid such as terephthalic acid by liquid phase oxidation of its precursor (e.g. p-xylene), an overhead stream 10 comprising an aqueous aliphatic carboxylic acid is added to the column 12 ). / RTI The azeotropic distillation may be carried out using a reflux of the azeotrope additive (22) with little or no azeotropic additive and adjusting the passage of the azeotrope additive to obtain a base product (34) containing a predetermined amount of residual water. Any aromatic dicarboxylic acid precursor present in the overhead stream is separated from the aliphatic dicarboxylic acid by removal at position 24 near the entry point of the feed 10 introduced into the column. The amount of water in the bottom product 34 can be controlled by the adjustment of the separate water feed 76 to the lower region of the azeotropic distillation column. In addition, an adjustment of the reflux rate (via line 22) may be used to control the water content in the bottom product and to maintain column operation upon loss of feed to the column.