Oxidation of Cyclohexene with H₂O₂ Catalyzed by Vanadium Based Polyoxometalates Doped Modified Clays as Green Catalysts

The catalytic performance of supported heteropolyacids in various liquid-solid and gas-solid heterogeneous reactions may be affected by the choice of support and/or the method of heteropolyacid deposition. Vanadium substituted polyphosphomolybdate with the Keggin structure H₄[PVMo₁₁O₄₀]· 13H₂O (PVMo) was dispersed throughout acid activated bentonite (clay from Hammam Boughrara, Maghnia, Algeria). A series of catalysts were prepared via modified impregnation. Modified preparation method employed ultrasonication as a means of the dispersion homogenization, followed by freeze-drying. The catalysts were characterized by the Brunauer-Emmett-Teller, the Fourier transform infrared, and ³¹P solid-state magic angle spinning-NMR spectroscopy. The catalytic performance of PVMo/Hmont was evaluated in the oxidation of cyclohexene. Intact Keggin anions were preserved on Hmont after deposition aided by ultrasonication. The obtained results showed that a better catalytic activity can be obtained with PVMo/bentonite (98% of conversion and 89% of cyclohexene oxide), by drop addition of H₂O₂, for 3 h.