Selective and Sequential Catalytic Chemical Depolymerization and Upcycling of Mixed Plastics

Area of Science:

• Polymer Chemistry
• Sustainable Materials
• Chemical Engineering

Background:

• Chemical recycling to monomer (CRM) is key for polymer circular economies.
• Processing mixed plastics via CRM is challenging due to unselective depolymerization, requiring costly pre-sorting or post-purification.
• Current methods lack selectivity, hindering efficient mixed plastic waste management.

Purpose of the Study:

• To develop a selective chemical depolymerization method for mixed common polymers.
• To utilize inexpensive and readily available dual catalysts for efficient polymer breakdown.
• To explore the upcycling potential of polymers into value-added monomers.

Main Methods:

• Employed common metal salt/organobase dual catalysts for depolymerization.
• Investigated selective and sequential depolymerization of poly(lactic acid) (PLA), bisphenol A polycarbonate (BPA-PC), and polyethylene terephthalate (PET) mixtures.
• Utilized alternative nucleophiles to explore monomer upcycling.

Main Results:

• Achieved selective chemical depolymerization of three common polymers (PLA, BPA-PC, PET) using dual catalysts.
• Demonstrated successful sequential depolymerization of polymer mixtures by judicious catalyst and condition selection.
• Explored the potential for upcycling polymers into higher-value monomers.

Conclusions:

• Developed a simple and selective CRM technique for mixed plastics using cost-effective catalysts.
• The selective depolymerization method reduces the need for pre-sorting or extensive purification, lowering waste processing costs.
• This approach offers a viable pathway for efficient polymer recycling and potential upcycling, advancing circular economy principles.