The Ethanol-Ethyl Acetate System as a Biogenic Hydrogen Carrier

Liquid organic hydrogen carriers will likely be a key element of a future hydrogen economy by enabling the storage and transport of large quantities of hydrogen. Ethanol is a liquid organic hydrogen carrier that is readily available from biological resources, which undergoes a reversible reaction to yield hydrogen and ethyl acetate. The objective of the present study is to obtain a better understanding of the thermodynamic and environmental suitability of the ethanol-ethyl acetate cycle for hydrogen storage applications. The analysis covers three aspects: thermodynamics of the chemical reaction, energy balance of the process, and a first-order assessment of greenhouse gas emissions. Thermodynamics of the reaction are characterized by a standard Gibbs energy of reaction close to zero which allows the reaction to be shifted between hydrogenation and dehydrogenation within a moderate window of temperature and pressure conditions. The energy demand for dehydrogenation is comparatively small, resulting in an overall system efficiency of 88%. A life cycle greenhouse gas analysis over a 20-year storage system lifetime gives a carbon intensity of 7.0 kg-CO2eq/kg-H-2 delivered. These results indicate that the ethanol-ethyl acetate system has considerable promise as a hydrogen carrier and should be the subject of further research.

Automated summary

The ethanol-ethyl acetate cycle shows promise as a hydrogen carrier due to its thermodynamic and environmental feasibility. The cycle has high reaction efficiency, low energy demand for dehydrogenation, and low greenhouse gas emissions. Further research is needed to explore its potential for hydrogen storage applications.