1,4-Butanediol as a Hydrogen Carrier: Liquid- versus Gas-Phase Dehydrogenation

Abstract

Hydrogen storage is a key technology for enabling the decarbonization of future energy systems, but is subject to low volumetric density in the case of compressed hydrogen. Chemical conversion to a liquid hydrogen carrier can overcome this challenging issue. For example, the reversible reaction of 1,4-butanediol (BDO) to γ-butyrolactone releasing two moles of hydrogen could be an attractive option for storing and transporting hydrogen. Herein, the thermodynamics of both, the reaction and the process, are evaluated. An important question that should be answered is whether there is a difference in energy efficiency between this reaction being performed in the liquid and in the gas phase. The thermodynamic analysis showed that heat demand for evaporation from the liquid to the gas phase is a major drawback of gas-phase reactions even though the enthalpy of reaction is somewhat smaller in the gas than in the liquid phase. However, due to the vapor pressure of BDO, there is some evaporation occurring in the case of liquid-phase reactions at reaction temperatures required to release hydrogen. This evaporation reduces the energy benefits of the liquid-phase reaction. As a consequence, the round-trip efficiencies of both options (liquid-and gas-phase reaction) are similar (varying by <5%). This is an advantageous finding as it allows selection of reaction conditions (liquid-or gasphase reaction) solely based on catalytic considerations, without major restrictions due to concerns from process engineering.

Use of Biosourced Molecules as Liquid Organic Hydrogen Carriers (LOHC) and for Circular Storage

“…Onoda et al [60] proved that the Ir-catalyzed (homogeneous) hydrogenation/dehydrogenation of this system worked appropriately in terms of yield (up to 99% for the two reactions) and selectivity. Then, Mevawala et al proved in 2022 that this reaction can occur both in the liquid and gas phases in an equally efficient manner over a Copper Chromite heterogeneous catalyst [61]. Many other copper-based heterogeneous catalysts have been used for this dehydrocyclization reaction [62][63][64].…”

Potential Benefits, Challenges and Perspectives of Various Methods and Materials Used for Hydrogen Storage

“…Therefore, extensive research is conducted globally to develop effective technologies, processes, and materials to meet the requirements of the hydrogen storage system, including low enthalpy change, moderate operating conditions, quick kinetics, affordability, acceptance, and security. − Comprehensive reviews presenting the latest status of hydrogen storage materials and techniques and accentuating the enthusiasm surrounding the recent scientific advancements are highly necessitated. Hence, hydrogen storage technologies have been the subject of numerous reviews, and research is still ongoing to uncover new methods of hydrogen storage. − …”

Highly selective pressure-dependent (transfer) hydrogenative depolymerization of polybutylene succinate

“…17 Furthermore, while GBL formation from BDO is endothermic, the Gibbs free energy of the reaction becomes favorable at elevated temperatures. 18 We therefore hypothesized that a ruthenium complex capable of catalyzing hydrogenation and dehydrogenation reactions at elevated temperatures could selectively generate either GBL or BDO from PBS through fine tuning of reaction conditions (Scheme 1). Both GBL and BDO are industrially important molecules, 19 therefore routes to produce these from PBS would enable a new chemical recycling pathway for this polyester.…”