Liquid‐phase oxidation of furfural catalyzed by magnetically separable metal oxide nanoparticles deposited on silica gel

Abstract

Oxidation of furfural (FF), a bio‐based platform chemical, was investigated using a range of iron‐, vanadium‐ and iron–zinc‐oxalates supported on silica gel (FeVOx@silica and FeZnOx@silica, respectively) as precursor for FeV@silica and FeZn@silica oxide catalysts and H ₂ O ₂ as a green oxidant. Furfural oxidation offers a route to valuable C ₄ diacids and lactones serve as monomers for biodegradable plastics, providing greener alternatives to petrochemicals. FeVOx@silica catalysts containing 5 wt% metal were synthesized following an oxalic‐acid‐assisted in situ impregnation/deposition method and calcined at 150–300 °C All catalysts developed magnetically recoverable properties owing to the presence of the iron oxide phases. Catalysts showed high activity in mild liquid‐phase FF oxidation (70 °C, 1 atm), achieving nearly complete substrate conversion within 3–4 h. Gas chromatography indicated the formation of two main products: maleic anhydride and 2‐furoic acid, with minor observed quantities of 2(5H)‐furanone. The addition of a small amount of formic acid (5 vol%), despite having little effect on FF conversion, notably impacted product ratios. Incorporating Zn cations into the Fe‐based catalyst (FeZn@silica) led to noticeable improvement of catalyst durability and suppression of the unproductive rapid decomposition of H ₂ O ₂ . FeZn catalyst calcined at 200 °C exhibited the highest product yield, whereas patterns obtained upon calcination below 150 °C and above 300 °C, despite furfural consumption (mineralization), produced much less detectable liquid products (suggesting Fenton‐like overoxidation and/or strong adsorption). This work demonstrates an effective green oxidation process for furfural under mild conditions using Earth‐abundant metal‐based catalysts.