SYNERGISTIC ENHANCEMENT OF AROMATIC COMPOUNDS VIA CO-PYROLYSIS OF POLYURETHANE WASTE AND COCONUT SHELLS
Abstract
This study investigates the enhancement of pyrolytic oil quality and fuel properties from polyurethane (PU) waste through co-pyrolysis with coconut shells (CS), chosen for their abundance, high calorific value, and low ash content. PU and CS were co-pyrolyzed at different ratios (4:1, 3:1, and 2:1), alongside pyrolysis of the pure materials for comparison. Thermal properties of the feedstocks, prepared in the same proportions as the actual pyrolysis systems, were characterized and used to construct decomposition models via the Criado plot method. Co-pyrolysis (PUCS) produced liquid yields (30.2–35.5 wt%) lower than theoretical values (40.4–42.6 wt%), indicating secondary decomposition reactions that converted condensable vapors into gases, likely promoted by PU–CS interactions. GC/MS analysis revealed that co-pyrolysis significantly enhanced the selectivity toward aromatic compounds (74.9–79.7%) through synergistic effects, facilitated by deoxygenation, hydrogen transfer, and Diels–Alder reactions. The highest aromatic compounds selectivity was observed at a PU:CS ratio of 3:1 (PUCS_3,1), indicating the strongest synergistic effect at this ratio. Moreover, the co-pyrolysis reduced the oxygen content of the pyrolytic oils attributed to higher degree of deoxygenation. Therefore, reduced oxygen content and increased aromatic carbon contributed to higher heating values (HHVs), demonstrating that PU–CS co-pyrolysis can yield improved-quality fuels from mixed waste and biomass feedstocks.
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