Reaction Equilibria in the Hydrogen Loading and Release of the LOHC System Benzyltoluene/Perhydro Benzyltoluene

Liquid organic hydrogen carriers (LOHCs) can store and transport hydrogen by chemical bonding. Benzyltoluene (H0-BT) is an attractive LOHC that can take up 12 H per carrier molecule. The chemical equilibrium favors hydrogenation at lower temperatures and higher pressures. In this work, we study hydrogenation kinetics at 125-200 degrees C and 0.3-30 bar H2. We perform ab initio calculations of all isomers of H0-BT and its (partially) hydrogenated forms to compute chemical equilibrium compositions. Despite hydrogenation being exothermic, full hydrogenation is thermodynamically possible almost up to the boiling temperature of the LOHC. Based on the obtained results, the tradeoff between the degree of hydrogenation and reducing the operating temperature is discussed.