Preparation, Characterization, and Catalytic Performance of Metal-Based Heterogeneous Catalysts for Glucose Oxidation to Gluconic Acid

The development of non-noble metal catalysts provides a cost-effective and sustainable route for glucose oxidation to gluconic acid. In this study, a series of catalysts based on inexpensive transition metals (Cr, Cu, Ni, Fe) and/or Au were synthesized using siliceous supports (SiO2 and MCM-41) and systematically evaluated. The aim was to partially or fully replace noble metals with lower-cost alternatives, while maintaining high catalytic performance. Comprehensive characterization—including ICP-AES for composition, N2 adsorption–desorption for porosity, XRD for structure, H2-TPR for reducibility, and NH3-TPD for acidity—was conducted to establish structure–property relationships. Among the tested catalysts, Ni- and Fe-based systems exhibited superior stability, with NiO/SiO2 achieving gluconic acid yields comparable to Au. The bimetallic Au–Ni/SiO2 catalyst displayed enhanced metal–support interactions and minimal leaching (<2%), while Au–Fe/SiO2 improved selectivity, yielding up to 23% gluconic acid, surpassing 5Fe/SiO2 (18%) and 0.3Au/SiO2 (15%), albeit with lower stability. These results highlight the potential of low-cost transition-metal and bimetallic catalysts as efficient and economically viable systems for selective glucose oxidation, providing insights for rational catalyst design in sustainable carbohydrate valorization.