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 eco-nomically viable systems for selective glucose oxidation, providing insights for rational catalyst design in sustainable carbohydrate valorization.