Photocatalytic oxidation of selected gas-phase VOCs using UV light, TiO_2, and TiO₂/Pd

Heterogeneous photocatalytic oxidation systems using titanium dioxide (TiO₂) have been extensively studied for the removal of several volatile organic compounds (VOCs). The addition of noble metals such as palladium on TiO₂ may improve photocatalytic activity by increasing charge separation efficiency. In this work, palladium was impregnated on TiO₂ and the efficiency of the new catalyst was tested and compared with that of pure TiO₂. Pd was impregnated on TiO₂ by the reduction method, using NaBH₄, and was characterized by XRD, XPS, UV-Vis, and H₂ chemisorption. The photocatalytic tests were performed in an annular coated-wall reactor using octane, isooctane, n-hexane, and cyclohexane at inlet concentrations varying from 100 to 120 ppmv. Compared with pure TiO₂ film, the photocatalytic activity of TiO₂ impregnated with 1 wt% of palladium was improved. All the aforementioned analytical techniques confirmed the presence of Pd incorporated into the structure of TiO_2, and the conversion rates were studied in a broad range of residence times, yielding up to 90 % or higher rates in 40 s of residence time, thus underscoring the relevant contribution of the technology.