Reaction Network and Kinetics Model for Neutral Hydrolysis of Poly(ethylene terephthalate)

Area of Science:

• Polymer Chemistry
• Chemical Kinetics
• Materials Science

Background:

• Poly-(ethylene terephthalate) (PET) is a widely used polymer facing recycling challenges.
• Hydrolytic depolymerization offers a potential pathway for PET chemical recycling.
• Understanding the kinetics and byproducts of PET hydrolysis is crucial for process optimization.

Purpose of the Study:

• To develop a comprehensive reaction network and kinetic model for PET hydrolytic depolymerization in neutral water.
• To accurately predict product yields, including terephthalic acid (TPA), under various conditions.
• To investigate the influence of temperature and time on PET hydrolysis and TPA formation.

Main Methods:

• Development of a seven-pathway reaction network model.
• Inclusion of autocatalysis by TPA and formation of various byproducts.
• Parameter estimation using literature data across a wide range of temperatures (170-570 °C) and times (15 s to 25 h).
• Model validation against experimental product concentrations.

Main Results:

• The model accurately fits experimental data with a mean absolute error of 0.023 M.
• It successfully predicts product yields from multiple published studies.
• The highest predicted TPA yield is 94% at 450 °C after 20 s, limited by TPA decomposition and equilibrium reactions.

Conclusions:

• The developed kinetic model provides a robust framework for understanding PET hydrolytic depolymerization.
• The model highlights the potential for high TPA yields, a valuable monomer for PET re-synthesis.
• Further optimization is needed to overcome limitations imposed by byproduct formation and decomposition pathways for achieving 100% TPA yields.