(408b) Mechanistic Insights into Ethylene Vinyl Alcohol (EvOH) Pyrolysis Via Micro-Reactor System Coupled to a Two-Dimensional Gas Chromatography

Despite over 359 million tons of plastic waste generated annually, only 9% is recycled. A major challenge lies in complex, multilayer plastics that incorporate polymers like ethylene vinyl alcohol (EvOH), which is widely used in food packaging for its excellent oxygen barrier properties. Its oxygen-rich composition and coextrusion with polyethylene make separation and recycling particularly difficult. Pyrolysis offers a promising thermochemical route to recycle such materials without separation, producing oils that can serve as a feedstock for petrochemical production after necessary upgrading. However, the pyrolysis reaction mechanisms of EvOH remain poorly understood.

This study investigates the primary solid-to-gas phase reactions of EvOH under isothermal, reaction-controlled conditions. A Box Behnken Design (BBD) was employed to systematically assess the effects of pyrolysis temperature, carrier gas flow rate, and sample size. Additional experiments at boundary and extreme conditions were conducted to probe limitations. Experiments were performed using a micro-pyrolyzer coupled to two-dimensional chromatography with flame ionization and time-of-flight spectrometer detectors (Py–GC×GC–FID/TOF–MS). Principal Component Analysis (PCA) of pyrolysis product yields identified statistically significant differences as a function of temperature, with total yield increasing from 31.43±1.42 wt% at 400 °C to 53.04±0.98 wt% at 500 °C. Within the BBD range, carrier gas flow rate and sample size had no statistically significant effects, although extreme conditions resulted in notably different yields. To our knowledge, this is the first study to offer a detailed, high-resolution compositional analysis of EvOH pyrolysis products. The methodology and data presented in this work provide a foundation for the development of experimentally validated microkinetic models and support the advancement of scalable chemical recycling for oxygenated polymers.