Poly (4-styrenesulfonic acid): A recoverable and reusable catalyst for acid hydrolysis of polyethylene terephthalate

Poly (4-styrenesulfonic acid) (PSSA) was used as a recoverable acid catalyst for the hydrolysis of polyethylene terephthalate (PET) to terephthalic acid (TPA) and ethylene glycol (EG). The effect of catalyst concentration, time, and temperature on the depolymerization of PET and yield of TPA were determined with PSSA and H2SO4. The PSSA system exhibited faster hydrolysis kinetics than H2SO4 with a shorter induction period than those often observed for acid hydrolysis of PET. The activation energies for the hydrolysis of PET were 24.8 kJ mol−1 and 29.1 kJ mol−1 for 2 M PSSA and 2 M H2SO4, respectively. The hydrophobic backbone of PSSA improves surface wetting of the catalyst solution at the PET interface, resulting in a higher localized concentration of protons. Contact angle measurements indicated better surface wetting of PET films by the aqueous solutions of PSSA than H2SO4 at equal concentrations. Additionally, the reutilization and titration results indicated that PSSA maintained the activity after reuse for five reaction cycles.