Liquid Phase Oxidation of Cyclohexene to Cyclohexenone over M (M = Co, Mn, Cr, Cu)/UiO-66-Sal Catalysts

A new type of catalyst by metal loaded on UiO-66-NH2 was prepared by modification of UiO-66-NH2 and post-synthesis with salicylaldehyde and impregnation by transition metals (Co, Mn, Cr, and Cu) to catalyze oxidation of cyclohexene in liquid phase at high pressure condition. The reactions were carried out in a high pressure batch reactor in the presence of tert-butyl hydroperoxide (TBHP) as oxidant in different temperature and pressure. Results showed high catalytic activity for oxidation of cyclohexene (100%) in the high pressure conditions. Maximum selectivity was achieved using Mn/UiO-66-Sal for 2-cyclohexen-1-one production (70%) at T = 50°C and P = 2.2 bar. Other products were 2-cyclohexen-1-ol and cyclohexene 3‑(tert-butyl) peroxide. Analysis of the products showed that the reaction pathway proceeds allylic mechanism instead of epoxidation pathway. Catalytic selectivity for 2-cyclohexen-1-one followed as Mn > Cr > Co ≈ Cu.