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PublicationApplied Catalysis B: Environmental

Behaviour of TiO2-SiMgOx hybrid composites on the solar photocatalytic degradation of polluted air

Authors:Silvia Suárez Gil, R. Portela, M.D. Hernández-Alonso , Benigno Sánchez
Groups of research:Spectroscopy and industrial catalysis
The photocatalytic performance of TiO2-SiMgOx ceramic plates for trichloroethylene abatement in gas phase has been evaluated under sun irradiance conditions. A continuous flow Pyrex glass reactor fixed on the focus of a Compound Parabolic Collector has been used. The performance of the hybrid photocatalyst has been evaluated as the variation of the TCE conversion and reaction product formation with the solar irradiance at different total gas flow, TCE concentration, and water vapour content. SiMgOx not only provides adsorbent properties to the photocatalyst, but it also allows the effective use of the material during low solar irradiance conditions. The adsorption-desorption phenomena play a pivotal role in the behaviour of the system. Thus, TCE conversion curves present two different branches when the sun irradiance increases (sunrise) or decreases (sunset). CO2, COCl2 and DCAC were the most relevant product detected. Meanwhile CO2 concentration was insensitive to the branch analysed, COCl2 or DCAC were not indicating the ability of these compound to be adsorbed on the composite. An increase of the UV irradiation at total TCE conversion promotes the CO2 selectivity. The excess of energy arriving to the reactor favours the direct reaction pathway to produce CO2. The photonic efficiency, calculated as a function of the rate for CO2 formation, decreases linearly with the solar irradiance up to around 2 mW cm-2, where becomes independent. For decontamination systems high TCE conversion is pursuit and then high solar irradiance values are required, in spite of lower photonic efficiency values. The present photocatalyts configuration, with only 17% of the reactor volume filled with the photoactive material, allows total TCE conversion for 150 ppm and 1 L min-1 in a wide sun irradiance window from 2-4 mW cm-2. The incorporation of water vapour lead to an increase of the CO2 selectivity keeping the TCE conversion around 90%, although significant amounts of COCl2 were observed.
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