Novel vanadium-chromium-bentonite green catalysts for cyclohexene epoxidation

• Bentonite-type clay from Maghnia (Algeria) is valorized as green catalyst.
• The clay structure is modified by acid activation and impregnation with transition metals.
• Chromium and vanadium enhanced redox properties and increased Lewis and Brønsted acidity.
• Vanadium oxides constitute appropriate redox centers for cyclohexene epoxidation.

The aim of this work is the valorization of bentonite-type clay from Maghnia (Algeria) as green catalyst for the production of added value fine chemicals. The modification of the clay structure by acid activation and impregnation of transition metals, such as chromium and vanadium, enhanced redox properties and increased Lewis and Brønsted acidity. Various samples of vanadia supported on chromium-containing acid-activated bentonite, were prepared and characterized by diffuse-reflectance UV–vis spectroscopy, surface acidity followed by FT-IR, X-ray diffraction, nitrogen adsorption–desorption isotherms and scanning electron microscopy (SEM) coupled with EDX. The catalysts prepared were studied in the cyclohexene epoxidation, using tert-butyl hydroperoxide as oxidant. The influences of vanadium content, catalyst weight, reaction temperature and oxidant amount on the evolution of the epoxidation reaction were checked. The experimental results showed an interesting catalytic activity of 43% and a selectivity towards epoxide of about 71%, when TBHP was used as oxidant and heptane as solvent.