engleski

Application of porous and nonporous materials based on transition metal oxides in oxidation reactions

Transition metal (TM) catalysts, based on molybdenum, vanadium, and tungsten, are known to be active and selective in oxidation processes. The starting research involved molecular catalysts (mononuclear and polynuclear coordination complexes and various supramolecular structures) to the supported ones (polyoxometalates attached to the Merrifield supports). Following green chemistry principles, all catalysts were tested in (ep)oxidation reactions. The emphasis is on minimal catalyst loading, no organic solvents added to the reaction mixture, and utilization of oxidants available in water solution. Further research interest is the preparation of materials containing copper metal centers and amino acid ligands, due to their versatile biological properties. The obtained materials were further tested both as conductors and catalysts. So far, the results have shown an interesting correlation between structure – conducting – catalytic properties. Recently, a new point of investigation has been opened: the preparation of oxide glasses and glass- ceramics. In the context of electrical/dielectric properties of glasses, there are still phenomena that have not been entirely resolved and are of great fundamental as well as technological importance. Glasses containing mobile alkali ions and transition metal oxides (TMO) such as WO3, Nb2O5, Fe2O3, V2O5, MoO3 are of significant prominence with mixed-ion polaron conductivity [1-9]. This transport is not simple as it involves mutual interactions between ions and polarons in these glasses. Nevertheless, it is especially attractive for applications as electrode materials for batteries, memory switching, and electrical threshold devices. The second phenomenon, the mixed glass- network former effect (MGFE), occurs in systems containing mobile alkali ions and two glass- network former oxides, namely traditional (SiO2, P2O5, GeO2, V2O5) and/or conditional one (WO3, Nb2O5, Fe2O3, MoO3) [9- 12]. Moreover, spontaneous or additional crystallization processes via controlled heat- treatments (HT) provides glass-ceramics that improve many glass properties, electrical properties in particular. Both effects highlight important role of structure for electrical transport in glass-(ceramics). Based on the above-mentioned, the catalytic testing with these materials containing various metal oxides open new directions in the development and application of the obtained materials. The tested samples (glass and glass ceramics) were prepared by mixing, melting and quenching Na2O-V2O5-P2O5-Nb2O5 in different molar ratios. Two different oxidizing agents were used: TBHP in decane and TBHP in water. The obtained catalytic results were correlated to the electric properties.

nanoporous materials, transition metal oxides, glass, glass-ceramics, catalysis

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