Depolymerization of PET into terephthalic acid in neutral media catalyzed by the ZSM-5 acidic catalyst

Reprocessing of waste plastic has been extensively studied. Herein, a facile and efficient method for solving the plastic recycling crisis was developed using micro-wave assisted hydrolysis of poly(ethylene terephthalate) (PET) into terephthalic acid (TPA). Previously developed acid or base catalysts are soluble in reaction media and difficult to separate after the reaction. ZSM-5 based zeolites, which are simply recoverable and facilely re-generable catalysts with Brønsted and Lewis acidic sites, were used herein as an acidic catalyst for the PET hydrolysis reaction. Controlling the Brønsted and Lewis acidic site concentration in the ZSM-5 zeolite by changing the Si/Al ratio of the zeolite framework and counter ion species was applied. The reaction kinetics and activation energy of the PET hydrolysis reaction in the presence of the developed catalyst were studied and compared with catalyst-free conditions. Based on this investigation, the correlation between Brønsted and Lewis acidic sites in ZSM-5-based catalysts and PET depolymerization yield was identified.