Selective HCOOH dehydrogenation for hydrogen production in water catalyzed by Ru-­-sulfonated phosphines

In the last years, the ever-increasing energy demand and the emerging problems connected to the dwindling of fossil fuels resources as well as their negative impact on the environment, have determined a growing interest in the development of alternative methods for energy production. In this context, hydrogen is considered to be a promising candidate as energy vector in combination with fuel cells technology. Among small organic compounds, HCOOH (Formic Acid, FA), which contains 4.4% of H2, is receiving attention as H2 chemical reservoirs and good materials for H2 storage. Selective catalytic dehydrogenation of FA produces H2 and CO2 avoiding CO formation, a poison for some fuel cells. These reactions can be run in water, the most abundant and safe solvent, by choice of convenient water-soluble ligands such as sulfonated phosphines. In this work, the stabilizing effect of different monodentate and bidentate sulfonated phosphines was studied for water-phase FA dehydrogenation using in situ catalytic systems based on RuCl3 x 3H2O and the dimer [Ru(?6-C6H6)Cl2]2 as metal precursors. Both Ru(III) and Ru(II) systems, tested under different reaction conditions, proved to be efficient giving high conversions at 90 °C. Furthermore, some of these systems exhibited high stability allowing for several runs in recycling experiments. Preliminary mechanistic details will be also discussed.