Abstract: A process for the preparation of purified terephthalic acid which comprises first introducing a liquid slurry containing crystalized terephthalic acid with impurities into a high pressure rotary filter, then filtering the slurry with the high pressure rotary filter and collecting at least some of the solid portion. The filter typically consists of a case, pressurized at process pressure, and a drum covered by a filtering device such as, for example, a cloth or equivalent filtering device, pressurized at a pressure suitably lower than the case. The drum is ideally divided into three zones: first zone, where the mother liquor is removed; second zone, where the solid is washed; third zone, where the excess of washing liquor is removed and the solid is discharged. The solid portion is washed, onto the filter drum, with additional amounts of water. The washed solid portion is then transferred to a letdown zone, which is at a pressure less than the zone in which the solid portion was collected.

Abstract: The subject is a class of catalyzers to be used in the stage of polycondensation of the synthesis of poly(ethylene terephtalate), consisting of metal and non-metal derivatives in composition with sulfonic acids mixed with titanium compounds so that the final polymer contains a sulfur quantity of 5-60 ppm and a quantity of metals between 2 and 100 ppm.