Surface Characterisation of V2O5/TiO2 Catalytic System

Catalytic ozonation with vanadium oxide-doped TiO2 nanoparticles for the removal of di-2-ethylhexyl phthalate

Among various plastic additives, di-2-ethylhexyl phthalate (DEHP) has been a great concern due to its high leaching potential and harmful effects on both human and the ecosystem. For the effective oxidation and mineralization of DEHP by ozone in the existing TiO₂ catalytic processes, the heterogeneous catalyst, vanadium oxide (V₂O₅)-incorporated TiO₂ (V₂O₅/TiO₂), was synthesized. The generation of hydroxyl radicals was promoted by cyclic redox reactions of vanadium atoms in V₂O₅/TiO₂ via the increase of surface oxygen vacancies by the replacement of V⁵⁺ species in the lattice of TiO₂. The catalytic ozonation in the presence of V₂O₅/TiO₂ exhibited the significantly higher degradation of DEHP with the pseudo-second-order kinetic constant of 1.7 × 10⁵ mM^-1min^-1 and the removal efficiency of 58.7% after 60 s in 2 mg/L of ozone. The degradation of DEHP was initiated by the shortening of the alkyl-side chain followed by the opening of esterified benzene moieties.

TiO₂ photoanode structure with gradations in V concentration for dye-sensitized solar cells

V-TiO₂(GC) photoanode film with graduated structure was prepared in a dye-sensitized solar cell work electrode by layer-by-layer method using TiO₂ precursor with gradations in V concentration on the indium tin oxide transparent conducting glass from substrate to surface. The effects of the gradient in V concentration on the structures and properties of TiO₂ photoanode film were discussed. The structure of the gradient V concentration has remarkable influence on the final performance of the DSSCs and I-V characteristic measurement indicates an enhanced efficiency by 31% as compared to pure TiO₂ nanoparticles film samples due to abundant solar light, fast injection and transmission velocity and the slowdown recombination of photoexcited electrons, simultaneously.

Development of silica/vanadia/titania catalysts for removal of elemental mercury from coal-combustion flue gas

SiO2/V2O5/TiO2 catalysts were synthesized for removing elemental mercury (Hg0) from simulated coal-combustion flue gas. Experiments were carried out in fixed-bed reactors using both pellet and powder catalysts. In contrast to the SiO2-TiO2 composites developed in previous studies, the V2O5 based catalysts do not need ultraviolet light activation and have higher Hg0 oxidation efficiencies. For Hg0 removal by SiO2-V2O5 catalysts, the optimal V2O5 loading was found between 5 and 8%, which may correspond to a maximum coverage of polymeric vanadates on the catalyst surface. Hg0 oxidation follows an Eley-Rideal mechanism where HCI, NO, and NO2 are first adsorbed on the V2O5 active sites and then react with gas-phase Hg0. HCI, NO, and NO2 promote Hg oxidation, while SO2 has an insignificant effect and water vapor inhibits Hgo oxidation. The SiO2-TiO2-V2O5 catalysts exhibit greater Hg0 oxidation efficiencies than SiO2-V2O5, may be because the V-O-Ti bonds are more active than the V-O-Si bonds. This superior oxidation capability is advantageous to power plants equipped with wet-scrubbers where oxidized Hg can be easily captured. The findings in this work revealed the importance of optimizing the composition and microstructures of SCR (selective catalytic reduction) catalysts for Hg0 oxidation in coal-combustion flue gas.

Comparison of a VO x -TiO2 and a VO x /SbO y -TiO2 Industrial Catalyst in the Oxidative Scission of Methyl Ethyl Ketone and 2-Butanol to Acetic Acid

The oxidative scission of methyl ethyl ketone and 2-butanol on a VO x -TiO2 and a VO x /SbO y -TiO2 catalyst was studied in the temperature range of 120 to 280°C in the presence of water vapour. The catalytic performance of the two catalysts was investigated by variation of reaction temperature and contact time, and the catalysts were characterized by BET, XRD, XPS, TPR-H2, TPD-NH3, and temperature programmed desorption of lattice oxygen (TPD-O2). The investigations indicate that the addition of Sb2O3 to VO x -TiO2 favours the selective formation of acetic acid and depresses total oxidation to CO x in the catalytic oxidation of methyl ethyl ketone and 2-butanol due to changes in the redox properties of the VO x -TiO2 system. Moreover, the higher acidity of the VO x -TiO2 catalyst favours the dehydration of 2-butanol to n-butenes.