Energy Valorization of Brachychiton populneus Seeds Through Catalytic Pyrolysis: Effects of Single-Component, Binary, and Ternary Catalytic Systems

This study examined the thermal conversion of Brachychiton populneus seeds using Al2O3, CaO, Fe2O3, and a zirconyl nitrate hydrate precursor (ZrO(NO3)2·xH2O), in single-component, binary, and ternary catalytic systems. Experiments were conducted at 400 °C, a heating rate of 5 °C min−1, and a biomass particle size of 315–630 µm, without continuous inert-gas purging. The initial reactor atmosphere therefore contained residual air. Under the non-catalytic condition, without additives, the recovered condensate and solid yields were 39.00 and 47.26 wt.% respectively; the remaining 13.74 wt.% was an apparent fraction calculated by difference rather than a directly measured gas yield. Among the single-component systems, Al2O3 gave the highest total condensed-liquid yield (62.88 ± 1.89 wt.%), whereas Fe2O3 produced the liquid product with the highest calculated higher heating value (HHV, 41.46 ± 1.24 MJ kg–1). Binary and ternary catalytic systems produced responses that differed from a selected additive reference based on single-component experiments at a higher individual-component loading. These deviations are descriptive and do not establish catalytic synergy. Fourier-transform infrared spectroscopy with attenuated total reflectance (ATR-FTIR) and gas chromatography–mass spectrometry (GC–MS) indicated differences among the recovered liquids. The results identify formulation-dependent changes in product recovery under the investigated non-purged conditions, while the effects of residual oxygen, precursor transformation, and individual-component loading effects require further evaluation.