2. Basic process principles

2.1 Process chemistry

PET can be prepared by reacting 1,2-ethanediol or monoethylene glycol (MEG) :

• either directly with terephthalic acid, the so-called direct esterification route;

• or with dimethyl ester or dimethyl terephthalate (DMT); this is the so-called ester interchange route.

These pathways are described in the following reaction schemes (with Ar = C ₆ H ₄ ).

• Interéchange-Voie ex-DMT

  $\begin{array}{ccc}{\text{H}}_3\text{C}—{\text{CO}}_2—\text{Ar}—{\text{CO}}_2—{\text{CH}}_3& +& 2{\text{HOCH}}_2{\text{CH}}_2\text{OH}\rightleftarrows \\ \text{DMT}& & \text{MEG}\end{array}$

  ...