Understanding the synergistic mechanisms of co-pyrolysis of straw and polyethylene for high-quality pyrolysis oil

Abstract

The co-pyrolysis of straw and polyethylene (PE) enhances pyrolysis oil quality by reducing oxygenated compounds and increasing hydrocarbons. However, the synergistic mechanisms between straw's main components (cellulose, hemicellulose, and lignin) and PE are not well understood. This study investigated these interactions, revealing a two-stage reaction: cellulose and hemicellulose dominate the first stage, while PE and lignin dominate the second. Significant synergistic effects were observed at 550 °C during the co-pyrolysis of straw and PE, resulting in at least a 17.84 % increase in alkanes and a decrease in oxygenated compounds. Free radicals from PE facilitated the cleavage of carbonyl bonds and promoted deoxygenation, leading to more hydrocarbons. Hemicellulose inhibited ester conversion (ΔV_esters = −3.00 %), while lignin suppressed ketone and alcohol formation (ΔV_ketones = −12.14 %, ΔV_alcohols = −1.07 %). These findings align with straw-PE co-pyrolysis results, providing new insights into the synergistic mechanisms between lignocellulosic biomass and plastics.