Highly Efficient and Recyclable Chromium(III)-Immobilized Mesoporous Al@MCM-41 Catalysts for the Oxidation of 1-Hexanol to Hexanoic Acid: Mechanism Study and Performance

In this study, chromium(III)- and iron(III)-immobilized mesoporous Al@MCM-41 (Si/Al = 20) catalysts were prepared using direct hydrothermal and wet impregnation approaches. The catalysts were characterized by XRD, FT-IR, BET, SEM, EDX spectroscopy, XRF, and STEM, confirming the successful incorporation of chromium and iron species into the ordered mesoporous framework. X-ray diffraction analysis confirmed that the hexagonal mesostructure was preserved in all catalysts. The catalytic performance was further evaluated in the oxidation of 1-hexanol using hydrogen peroxide as a green oxidant under atmospheric pressure at 30 °C during 8 h. Compared to iron(III), chromium(III) incorporation into the Al@MCM-41 material improves both its conversion and selectivity towards hexanoic acid, regardless of the synthesis strategy employed. Particularly, the Cr@Al@MCM-41 catalyst has demonstrated high activity (96%) and exceptional selectivity (87%) towards hexanoic acid, positioning it as an outstanding candidate for alcohol oxidation processes. The Cr@Al@MCM-41 catalyst demonstrated excellent recyclability, maintaining consistent conversion over three reuse cycles without significant loss in activity. These results demonstrate that the synthesized Cr@Al@MCM-41 catalyst exhibits outstanding catalytic efficiency and robust durability, making it a promising catalyst for many oxidation applications.