LOHCs

LOHCs, or liquid organic hydrogen carriers, are chemical compounds capable of storing and releasing hydrogen through reversible hydrogenation and dehydrogenation reactions in the liquid phase. In an LOHC cycle, a hydrogen-rich liquid is dehydrogenated to release hydrogen on demand, and the remaining carrier is hydrogenated again using supplied hydrogen to regenerate the stored form for reuse. This approach aims to enable safe, portable, and scalable hydrogen storage and transport using conventional liquid handling and distribution systems.

The most developed LOHC system is the methylcyclohexane/toluene pair. In this cycle, toluene is hydrogenated to methylcyclohexane using hydrogen, and methylcyclohexane is dehydrogenated to release hydrogen and return to toluene. Reactions typically occur with suitable catalysts at elevated temperatures and moderate pressures. The energy required for dehydrogenation and hydrogenation, catalyst performance, and heat management are central engineering considerations, as is the need to minimize impurities that can poison catalysts.

Beyond MCH/toluene, a range of other candidate LOHCs has been studied, including various aromatic and polycyclic hydrocarbons. Research focuses on identifying carriers with high hydrogen capacity, favorable kinetics, chemical stability, and compatibility with existing infrastructure. Catalyst development and process integration remain active areas to improve efficiency and reduce costs.

LOHC technology offers potential advantages for hydrogen storage and transport, including higher perceived safety and the ability to leverage established liquid-fuel logistics. Its deployment is currently mainly at the pilot and demonstration stage, with ongoing work aimed at overcoming energy penalties, catalyst durability, and system integration challenges.