Search

A series of α -MoO _3 -TiO _2 mixed oxides were prepared by calcining a mixture of the heteropolyacid H _3 PMo _12 O _40 and TiO _2 at temperatures ranging from 350 °C to 600 °C. The mixed oxides thus prepared were characterized and tested for the oxidation of cyclohexene by the oxidizing mixture H _2 O _2 /CO _2 . FTIR and XRD characterizations showed that the Keggin structure of H _3 PMo _12 O _40 was preserved for calcination temperatures below 400 °C. Above 450 °C, Keggin’s structure collapses. XRD analysis revealed that as the calcination temperature increased, more orthorhombic α -MoO _3 was formed. Analysis of the reaction mixture by GC-MS showed that oxidation by the H _2 O _2 /CO _2 mixture leads to 1,2-cyclohexanediol as the main product and to 2-cyclohexene-1-one and 2-cyclohexene-1-ol as minor products. Oxidation by H _2 O _2 /CO _2 mixture proved to be more effective than H _2 O _2 alone and CO _2 alone. The conversion (69.4%) and the 1,2-cyclohexanediol selectivity (93.2%) obtained over α -MoO _3 -TiO _2 mixed oxides, higher than that obtained with TiO _2 monoxide and α -MoO _3 monoxide, suggest a synergistic effect between TiO _2 and α -MoO _3 . This efficient and stable catalyst after reuse can be developed for the synthesis of diols.