Acetic Acid Ketonization over Fe₃O₄/SiO₂ for Pyrolysis Bio‐Oil Upgrading

<jats:title>Abstract</jats:title><jats:p>A family of silica‐supported, magnetite nanoparticle catalysts was synthesised and investigated for continuous‐flow acetic acid ketonisation as a model pyrolysis bio‐oil upgrading reaction. The physico‐chemical properties of Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub>/SiO<jats:sub>2</jats:sub> catalysts were characterised by using high‐resolution transmission electron microscopy, X‐ray absorption spectroscopy, X‐ray photo‐electron spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, thermogravimetric analysis and porosimetry. The acid site densities were inversely proportional to the Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> particle size, although the acid strength and Lewis character were size‐invariant, and correlated with the specific activity for the vapour‐phase acetic ketonisation to acetone. A constant activation energy (∼110 kJ mol<jats:sup>−1</jats:sup>), turnover frequency (∼13 h<jats:sup>−1</jats:sup>) and selectivity to acetone of 60 % were observed for ketonisation across the catalyst series, which implies that Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> is the principal active component of Red Mud waste.</jats:p>