Risks from Hydrogen Carriers - Safety Characteristics of the LOHC System Toluene/Methylcyclohexane

Reversible liquid organic hydrogen carriers (LOHCs) seem to be a promising solution for the transportation of hydrogen. Since no pressure or cooling needs to be applied during the transport, it is considered easier, safer and cheaper compared to pressurized gas tanks or cryogenic hydrogen on long routes and is already applied in large quantities and long distances. One simple system is methylcyclohexane and toluene. Toluene gets shipped to countries with an excess of (preferably green) energy and is charged with hydrogen to form methylcyclohexane. This is then shipped back to the place with energy and/or hydrogen demand and split into hydrogen and toluene. For toluene, some safety characteristics are available, whereas methylcyclohexane is loosely analyzed, hence safety characteristics are the basis for an appropriate approach to tackle the hazards and for the risk assessment. This paper focuses on the safety characteristics of both substances, compares the differences and points out the crucial hazards of this system, especially if the same tanks for transportation are used.