Published October 2018
Purified terephthalic acid (PTA), one of the largest-volume commodity chemicals, is predominantly used for producing saturated polyesters, mainly polyethylene terephthalate (PET) and related polymer products such as fibers, resins, thin films, bottles, etc. A small portion of terephthalic acid is used in the production of semi-aromatic and aromatic polyamides and intermediate chemicals such as cyclohexanedimethanol, terephthaloyl chloride, liquid crystal polymer, etc.
Usually, PTA is produced in a two-stage process. In the first stage, crude terephthalic acid (CTA) is produced by liquid-phase oxidation of para-xylene (p-xylene) in acetic acid medium in the presence of a cobalt acetate and manganese acetate catalyst with hydrogen bromide as a source of bromine promotor. Typically, CTA contains impurities such as 4-carboxybenzaldehyde (4-CBA), p-tolualdehyde, benzoic acid, and p-toluic acid, which are responsible for changing the color of the final product. In the second stage, CTA produced by the oxidation reaction is then purified through hydrogenation. Purification of CTA typically requires at least one chemical transformation (e.g., hydrogenation) in addition to a physical procedures such as crystallization, filtration, and drying to produce the final PTA product. Purification of PTA is necessary to achieve high-purity and high-value product.
PTA production is a conventional technology. The most commercial route for PTA production is catalytic liquid-phase oxidation of feedstock p-xylene. S&P Global has previously covered various licensor technologies for the production of PTA. PEP Reviews 2017-01, CNPC (China National Petroleum Corporation) Millionton PTA Process (April 2017) and 2015-11, BP New Generation Process for Polymer-Grade Terephthalic Acid Production (December 2015) provide technoeconomic evaluations (capital investment cost and production cost) of the China National Petroleum Corporation (CNPC) and BP PTA processes. PEP Reports 9 (February 1966) through 9F (August 2005) present detailed process analyses and production economics assessments of most of the PTA process technologies.
This report examines three technologies and presents a comparative technoeconomic evaluation, along with an overall picture of their respective carbon footprints and preliminary economics for all of the processes. All three processes are conceptually designed to use liquid-phase oxidation of p-xylene to derive PTA. The three technologies presented and compared in economic terms in this report are:
- The PTA P7 technology licensed by INVISTA Performance Technologies (IPT)
- The PTA technology with high yield and low solvent, licensed by Mitsubishi
- The COMPRESS™ PTA process by Dow-Davy (Johnson Matthey)
This report also presents the current status of the PTA industry, including global and regional demand and supply, producers, and technology licensors.