To produce PTA oxidation of Paraxylene accomplished in Acetic Acid in presence of metal catalyst like (Mn+2), Initially (CTA) crude Terephthalic Acid was obtained and then purified. Thats why its called Purified Terephthalic Acid. In manufacturing technology wise there would be change but general outline is same for all the technology providers. The reactions of importance are shown in the following chemical equations (the two moles of water formed by the selective oxidation of Paraxylene is not shown):

Purification of Crude Terephthalic Acid requires at least one chemical step in addition to the physical procedures (e.g. crystallization, washing).  One of the major impurities, 4-carboxybenzaldehyde (4-CBA), is quite difficult to remove by physical means but can be converted to para-toluic acid by catalytic hydrogenation in an aqueous solution as shown in the following equation:


The technology consists of the following major processing steps:

  • Paraxylene oxidation (CTA synthesis)
  • CTA crystallization
  • CTA centrifugation or filtration
  • CTA drying
  • CTA dissolution
  • Hydrogenation (CTA purification to PTA)
  • PTA crystallization and filtration
  • PTA centrifugation
  • PTA drying