Fabrication of Bimetal CuFe₂O₄ Oxide Redox-Active Nanocatalyst for Oxidation of Pinene to Renewable Aroma Oxygenates

This study report on the synthesis of spinel CuFe₂O₄ nanostructures by surfactant-assisted method. The catalysts were characterized by X-ray diffraction (XRD), laser Raman, transition electron microscope (TEM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), hydrogen temperature programmed reduction (H₂-TPR), and Brunauer-Teller-Emmett-Teller (BET) surface area techniques. CuFe₂O₄ was active for pinene oxidation using tertiary butyl hydroperoxide (TBHP) to pinene oxide, verbenol, and verbenone aroma oxygenates. Under optimized reaction conditions, the spinel CuFe₂O₄ catalyst could afford 80% pinene conversion at a combined verbenol/verbenone selectivity of 76% within the reaction time of 20 h. The changes in catalyst synthesis solvent composition ratios induced significantly varying redox, phases, and textural structure features, which resulted in various catalytic enhancement effect. Characterization results showed the spinel CuFe₂O₄ catalyst possessing less than 5 wt% impurity phases, Cu(OH)₂, and CuO to afford the best catalytic performance. The CuFe₂O₄ catalyst was recyclable to up to five reaction cycles without loss of its activity. The recyclability of the bimetal CuFe₂O₄ oxide catalyst was simply rendered by use of an external magnet to separate it from the liquid solution.