Catalytic transformation of levulinic acid into γ-valerolactone with photoelectrocatalytic hydrogen using a novel one-unit set-up: Optimization of the preparation procedure of ruthenium-based catalyst

[Display omitted] •TiO2 nanotubes and Ru sites for in-situ H2 production and levulinic acid conversion.•Novel set-up consisting of one unit and two catalysts.•Hydrogen from photoelectrocatalytic water splitting for biomass valorization.•Dispersed Ru metallic sites on cheap alumina to optimize the catalytic performance. The growing demand of energy and the increase in the greenhouse gases emissions has caused the search for new renewable energy sources, such as biomass, to replace fossil fuels. Thus, there are different compounds, i.e. γ-valerolactone (GVL), which can be obtained from different biomass-derived substrates such as levulinic acid (LA). In the present work, the catalytic hydrogenation of levulinic acid to γ-valerolactone has been studied, using as a hydrogen source that obtained by photoelectrocatalytic water splitting. The use of the photoelectrocatalytic hydrogen has been conducted in two ways: i) one set-up in two steps involving a cell for hydrogen production and a reactor for the LA to GVL transformation or ii) a novel set-up consisting of just one unit in which hydrogen formation and LA hydrogenation take place simultaneously. The photoelectrocatalyst used for the water to hydrogen reaction is a TiO2 nanostructure synthesized by electrochemical anodization, whereas several catalysts based on ruthenium have been studied for the LA hydrogenation. Optimization in the synthesis procedure of ruthenium catalysts supported on gamma-alumina has allowed high yields to GVL at low reaction temperature (30 °C). The most efficient ruthenium catalyst presenting high proportion of surface metallic ruthenium and high dispersion on the support was that synthesized by a simple precipitation method. Finally, the use of the novel one-unit set-up makes possible not only achieving high GVL yields but also the recyclability of the catalyst with just a scarce loss in productivity, conversely to what happens using the traditional hydrogenation with pressurized hydrogen.