Solar energy and biowaste conversion into H2 on CuOx/TiO2 nanocomposites

The possibility to recover H2 from waste organic streams in biorefineries using photocatalytic approaches is an attractive option to enhance process sustainability and produce valuable energy products [1]. In recent years an intense research activity has been made on this topic, but mainly focused on the use of TiO2 doped with noble metals under slurry conditions. Here we report on the synthesis and characterization of low cost CuOx/TiO2 nanocomposites and their photocatalytic evaluation in process of H2 production by selective photo-dehydrogenation of dilute aqueous solutions of ethanol. The methods of sample preparation allowed to maximize the dispersion of Cu nanoparticles on TiO2 surface, improving their photocatalytic performances in H2 production [2]. CuOx/TiO2 materials were tested in liquid phase as a powder suspended in a typical slurry-type reactor and in gas phase as a thin film using a novel reactor design. The aim of this contribution is to better understand analogies and differences between gas and liquid phase operations, which are of great importance for a better engineering design of the photochemical process, as well as in practical and fundamental perspectives for an actual industrial implementation. The potential advantages of operating in gas phase with respect to the traditional slurry photochemical reactors are the following: i) minimization of scattering phenomena, ii) good pattern of irradiation, iii) ability to transfer the power coming from sunlight to a conductive substrate, iv) easier scale-up, (v) elimination of problems associated to metal-leaching and (vi) easier product recovery [3]. Results showed that gas phase operation allowed a higher H2 productivity with respect to liquid phase, and especially a higher selectivity (about 92-93 %) to acetaldehyde. It is remarked that the route of photo-dehydrogenation of ethanol to H2 and acetaldehyde has an economic value about 3.0-3.5 times higher than the alternative route of photoreforming to produce H2. References C. Ampelli, R. Passalacqua, S. Perathoner, G. Centi, P. Fornasiero, Preprints of Symposia – American Chemical Society, Division of Fuel Chemistry, 2010, 55 (2), 273-274. T. Montini, V. Gombac, L. Sordelli, J. J. Delgado, X. Chen, G. Adami, P. Fornasiero, ChemCatChem, 2011, 3, 574-577. C. Ampelli, C. Genovese, R. Passalacqua, S. Perathoner, G. Centi, Theoretical Foundations of Chemical Engineering, 2012, 46 (6), 651-657.