Catalytic pyrolysis of Brachychiton seeds in a fixed-bed reactor for the production of high-quality bio-oil.

As a key thermochemical conversion technique, pyrolysis transforms biomass into valuable products, representing a promising strategy for the sustainable valorization of biomass. The pyrolysis of Brachychiton seeds was investigated in a fixed-bed reactor at 300–550 °C, with particle sizes ranging from <315 to 1600 µm, and a heating rate of 5 °C/min, in the absence of inert gas. The catalytic effect of 1% Al₂O₃ was examined and compared with that of CaO, ZrO(NO₃)₂, Fe₂O₃, and non-catalytic conditions under the same operating parameters. The highest bio-oil yield (62.88%) was obtained with Al₂O₃. ATR-IR analysis revealed that both temperature and catalyst type influenced the intensity of functional groups. Elemental analysis showed that Al₂O₃ and Fe₂O₃ increased carbon content (up to 64.74% with Al₂O₃) and reduced oxygen, whereas CaO and ZrO(NO₃)₂ increased oxygen content. Fe₂O₃ promoted higher hydrogen content (16.06%). The calorific value peaked at 42.39 MJ/kg with Al₂O₃ at 350 °C. GC-MS analysis indicated that Al₂O₃, CaO, and ZrO(NO₃)₂ markedly reduced fatty acids (from 62.84% to 31.27%, 29.77%, and 47.6%, respectively), while Fe₂O₃ increased them (72.89%). Hydrocarbon content was significantly enhanced with Al₂O₃ (15.67% to 39.1%) but decreased with the other catalysts.