Patent ID: 6639104
Filing Date: 2003-10-28
Classification: C07C

Abstract:
A process for the preparation of purified terephthalic acid which comprises:a. introducing a liquid slurry containing crystallized terephthalic acid with impurities into a high pressure rotary filter; b. filtering said slurry and collecting at least some of the solid portion; c. washing the solid portion with additional amounts of water and collecting the washed solid portion in a collection zone under pressure of from 1.0 to 10.0 bar; d. passing the collected washed solid portion from the collection zone to a letdown zone, wherein the letdown zone is at a pressure at least 0.01 bar less than the collection zone; e. sealing a connection between the letdown zone and the collection zone, such that a change of pressure in the letdown zone will not effect the pressure in the collection zone; f. reducing the pressure of the letdown zone; g. removing the washed solid portion from the letdown zone; and h. increasing the pressure of the letdown zone to 0.01 to 0.3 bar less than the pressure of the collection zone so that it may accept additional washed solid material from the high pressure rotary filter.