Esterification and Transesterification
topic
TPA route: direct esterification of TPA with EG at 240–260°C produces bis(2-hydroxyethyl) terephthalate (BHET) monomer with water by-product. DMT route: transesterification of DMT with EG at 150–220°C with methanol evolution, catalysed by Mn or Zn acetate. Both routes yield BHET as precursor for polycondensation.
Role
The choice between TPA and DMT routes affects catalyst system, by-product handling, reaction control, and monomer purity, all critical for achieving target molecular weight and fibre quality.