Closed-loop recycling of polyethylene to ethylene and propylene via a kinetic decoupling–recoupling strategy

Abstract

Conversion of polyethylene (PE) into ethylene and propylene will enable closed-loop recycling of plastics. Conventional catalytic cracking of PE is restricted by kinetic entanglement between the formation of main products and by-products, limiting ethylene and propylene yields to less than 25%. Here we address this challenge with a kinetic decoupling–recoupling (KDRC) strategy, achieving yields of ethylene and propylene up to 79% from PE conversion using a tandem reactor with dual zeolite catalysts. Reaction kinetics analysis, synchrotron-based vacuum ultraviolet photoionization mass spectrometry and in situ neutron powder diffraction reveal that KDRC decouples kinetics of PE cracking to intermediates (butenes and pentenes) in the first stage and synchronizes this process with dimerization–β-scission reactions in the second stage. This synchronization minimizes by-products and enhances ethylene and propylene production substantially. Combined with high catalytic stability, this KDRC strategy represents a robust pathway to combating plastic pollution via a circular economy. This study introduces a kinetic decoupling–recoupling strategy to overcome kinetic limitations in plastic recycling. A tandem catalytic reactor, utilizing zeolite catalysts, converts polyethylene into ethylene and propylene with yields of up to 79%, offering a promising pathway toward efficient closed-loop recycling of polyolefins.