Synergistic catalytic co-pyrolysis of eucalyptus bark and polyethylene over natural clinoptilolite: Thermogravimetric and kinetic evidence

Catalytic co-pyrolysis is a promising strategy for thermochemical conversion of biomass and plastic wastes; however, the combined influence of hydrogen-rich polymers and natural zeolite catalysts on reaction kinetics remains poorly understood. This study investigated the effects of low-density polyethylene (LDPE) and natural clinoptilolite (CLIN) on the thermal degradation behavior, interactions, and apparent activation energies of eucalyptus bark (EB). Thermogravimetric analyses were performed under pyrolysis, catalytic pyrolysis, co-pyrolysis, and catalytic co-pyrolysis conditions at 10, 30, and 50 K min −1 . Interactions were evaluated using the deviation method, while apparent activation energies were determined using the Friedman and Kissinger–Akahira–Sunose (KAS) methods. Co-pyrolysis with LDPE produced composition- and heating-rate-dependent synergistic and inhibitory interactions and reduced the mean apparent activation energies in the lignin/LDPE-dominated region relative to pure LDPE. Clinoptilolite modified the kinetic behavior depending on blend composition and catalyst loading. Catalytic co-pyrolysis of the blend containing 50 wt% LDPE and 15 wt% CLIN exhibited particularly low mean apparent activation energies in Regions I and II, and the highest pyrolysis performance index among catalytic blends at 50 K min −1 . These findings support the potential application of low-cost natural zeolites in biomass–plastic co-pyrolysis.