Chemical Equilibria in Formic Acid/Amine-CO2 Cycles under Isochoric Conditions using a Ruthenium(II) 1,2-Bis(diphenylphosphino)ethane Catalyst

The equilibrium position in formic acid/amine–CO2 systems has been examined as a function of pressure and tem- perature under isochoric conditions. The homogeneous ruthe- nium(II)-1,2-bis(diphenylphosphino)ethane catalyst was active in both reactions, that is, in formic acid cleavage producing pure hydrogen and CO2, as well as in carbon dioxide hydroge- nation under basic conditions. High yields of formic acid dehy- drogenation into H2 and CO2 are favored by low gas pressures and/or high temperatures, and H2 uptake is possible at elevat- ed H2–CO2 pressures. These results take us one step closer to the realization of a practical H2 storage–discharge device.