VAp Catalyzed Oxidation of Furfural to Maleic Acid: Kinetic Studies

The catalytic conversion of biomass-derived furfural to maleic acid is a promising route to sustainable chemical production. In this study, vanadium-apatite (VAp) was synthesized and evaluated as a heterogeneous catalyst for the controlled oxidation of furfural using hydrogen peroxide in a γ-valerolactone–water medium. Comprehensive characterization (XPS, SEM, XRD) confirmed the incorporation of V5+ species within a stable apatite lattice possessing hierarchical porosity. Systematic variation of reaction parameters, including temperature, oxidant-to-substrate ratio, catalyst loading, and solvent composition, demonstrated that VAp effectively promotes furfural conversion under mild conditions. An optimized H2O2: furfural molar ratio of 7:1 afforded complete furfural conversion with selectivity (∼47%) toward maleic acid, while limiting deeper oxidation to other C4 acids. The catalyst retained high activity over four consecutive cycles with slight selectivity loss, indicating good structural stability. Kinetic analysis followed a Langmuir–Hinshelwood–Hougen–Watson (LHHW) model with competitive adsorption of reactants, and the calculated activation energy (37 kcal/mol) reflects the temperature dependence of the transformation. Overall, the study establishes VAp as a robust and reusable catalyst capable of enabling controlled oxidation of furfural to maleic acid within a green and scalable reaction system.