Simple and recyclable ionic liquid based system for the selective decomposition of formic acid to hydrogen and carbon dioxide

Abstract

Exploitation of hydrogen as an energy carrier requires the development of systems for its storage and delivery. Formic acid has been proposed as valuable hydrogen carrier compound, due to its relatively high hydrogen content (53 g L⁻¹), the latter being easily and cleanly released in catalytic reactions under mild conditions (HCOOH → H₂ + CO₂). Ionic liquids are interesting solvents for homogeneous catalyzed formic acid decomposition systems as their extremely low volatility avoids solvent contamination of the produced hydrogen stream. In this paper an outstandingly simple, robust and active catalyst system is presented, namely RuCl₃ dissolved in 1-ethyl-2,3-dimethylimidazolium acetate (RuCl₃/[EMMIM][OAc]). This system proved to be fully recyclable over 10 times. Turnover frequencies (TOF) of 150 h⁻¹ and 850 h⁻¹ were obtained at 80 °C and 120 °C, respectively.