Oxidation of cyclohexanol and cyclohexene with triazenido complexes of chromium immobilized in biosorption FAU supports

• Fau supported Cr catalysts were prepared by biosorption of waste metal.
• Diphenyltriazene derivatives proved to be suitable coordination agents for CrFAU.
• CrFAU catalysts were successfully used in mild condition oxidation reactions.
• Cr leaching was effectively reduced by the immobilization procedure.

This work presents the recovery of biosorption supports as an alternative source of benign production of heterogeneous catalysts for oxidation reactions in mild conditions. Cr-containing FAU zeolite, in sodium form (NaY) and in proton form (HY), was recovered from biosorption studies and reused as support for the preparation of heterogeneous catalysts by the flexible ligand method, using 1,3-diphenyltriazene derivatives. Results showed that the ligand play an important role in the coordination of Cr inside the zeolite. The catalysts showed good activity for the oxidation of cyclohexanol, reaching a maximum of 63.5% conversion. Cr leaching was evaluated and it was found that the Cr–FAU supports lost some of the Cr into the reaction medium, whereas immobilization of Cr-complexes reduced the referred leaching. For the cyclohexene oxidation, a maximum 72.9% conversion was achieved with a HY zeolite-based catalyst.