New catalysts with dual-functionality for cyclohexane selective oxidation

Abstract

M-Co-TUD-1; a series of the new materials was prepared by applying one-step synthesis procedure based on sol-gel technique. The prepared materials contain 1wt% of cobalt ions and 5wt% of metal oxide (metal = Cr, Cu, Ti, Mn, Bi, V, or Sr) in the TUD-1 mesoporous material. The prepared materials were characterized by using XRD, DRS UV–vis, N2 sorption measurements, ICP elemental analysis, SEM, and HR-TEM. Characterization results showed that all the prepared materials contain isolated Co2+ ions and nanoparticles of Cr2O3, TiO2, MnO, V2O5 or bulky crystals of Bi2O3 and CuO incorporated in the silica matrix. The catalytic performance of the prepared materials was evaluated in liquid phase, free-solvent selective oxidation of cyclohexane to cyclohexanone and cyclohexanol by using TBHP as an oxidant at 70 °C. The prepared materials exhibited higher activity than either Co-TUD-1 or other M-TUD-1. More importantly, a very small concentration of the intermediate; cyclohexyl hydroperoxide (CHHP) was detected. In case of stability, Mn-Co-TUD-1 and Ti-Co-TUD-1 exhibited an excellent stability during the reaction. Moreover, Mn-Co-TUD-1 was successfully recycled up to 4 runs.