Innovative structured VOx/TiO2 photocatalysts supported on phosphors for the selective photocatalytic oxidation of ethanol to acetaldehyde

Abstract

In this work, an innovative and effective formulation of photocatalysts is presented. The highly selective photocatalysts at 5wt% of nominal V2O5 on TiO2 for the photoconversion of ethanol to acetaldehyde was supported on the surface of commercial ZnS based phosphors (ZSP), on the base of the evidence that the addition of these phosphors, physical mixed with the photocatalysts, as light carriers inside a gas-solid fluidized bed photoreactor resulted in a significantly improved photoefficiency. Structured vanadia-titania catalysts in the form of micropellets were successfully synthesised by sol–gel method on the UV activated luminescent phosphors microparticles. The catalysts were investigated by TG-MS analyses, Raman and UV–vis spectroscopy, X-ray diffraction, as well as adsorption of N2 at −196°C.A progressive increase of the amount on titania on the phosphors was realized to get the well dispersed nanoparticles of TiO2 on ZSP surface, able to absorb the UV light needed by the photoreaction in the proximity of light source. The residual UV light can penetrate up to the phosphors core, leading to their excitation and emission of further radiation at 440nm useful to proceed the photoreaction in darker zones. The performances of structured VOx/TiO2/ZSP have been compared to physical mixtures of VOx/TiO2 catalyst with phosphors in the partial photooxidation of ethanol to acetaldehyde with the gas-solid fluidized bed photoreactor at high illumination efficiency. The ethanol consumption rate increased linearly with the ethanol initial concentration and at given alcohol concentration, its value was significantly higher on VOx/TiO2/ZSP with respect to the case in which the photocatalyst was only mixed with them. The results underlined as the higher capture of the structured photocatalyst, due to the additional light harvesting of support, gives enhanced activity in the selective oxidation of ethanol to acetaldehyde already dramatically improved by the innovative use of light emitting phosphorescent particles.