Purified Terephthalic Acid From p-Xylene by Hydrolysis of Dimethyl Terephthalate

This review presents a process design for a facility to manufacture 550 million lb/yr (249,000 t/yr) of purified terephthalic acid (PTA) from p-xylene by the hydrolysis of dimethyl terephthalate (DMT). We compare the economics for this PTA/DMT process with updated economics for the conventional PTA production method—bromine-catalyzed p-xylene oxidation. In the process reviewed here, DMT is produced from p-xylene by successive oxidations and esterifications with methanol, the so-called Witten-Katzschmann Process of the former Dynamit Nobel. The resulting high-purity DMT is then hydrolyzed to PTA. H�ls, Dynamit Nobel's successor, licenses technology similar to that presented here. H�ls refers to its process as the H�ls PTA/DMT Process.

The H�ls process requires a larger capital investment and has higher capital-related costs, but has lower variable costs. Total fixed capital and plant cash costs are somewhat higher for the H�ls process than for the conventional process, but cash costs are somewhat lower. The net production costs are lower for the H�ls process than for the conventional process.