(672f) Establishment of a Kinetic Model for the Dehydrogenation of Perhydro-Benzyltoluene: Insights from a Differential Reactor Study

New energy storage systems are essential for the transition to renewable energy. Hydrogen, with its high gravimetric storage density, is the key. However, the volumetric energy density of hydrogen at ambient conditions is remarkably low. Liquid Organic Hydrogen Carriers (LOHC) show promise for efficient storage at ambient conditions.

A LOHC system consists of at least one hydrogen-lean and one hydrogen-rich molecule. These molecules can reversibly store and release hydrogen. A promising LOHC system is benzyltoluene (H0-BT)/perhydrobenzyltoluene (H12-BT).

The hydrogenation and dehydrogenation of these molecules are heterogeneously catalysed reactions carried out in chemical reactors. A thorough understanding of the kinetics is essential for the design and optimisation of these reactors. The dehydrogenation of H12-BT is typically carried out at a pressure above the vapour pressure of the molecule. This means that H12-BT enters the reactor as a liquid. The first catalyst particle is therefore completely wetted with liquid H12-BT and the kinetics must describe the release of hydrogen from the liquid H12-BT. The released hydrogen causes the liquid H12-BT to evaporate at a pressure above the vapour pressure and the amount of wetted catalyst particles decreases with increasing reactor length. Under technically relevant conditions, complete evaporation of all LOHC molecules occurs in the first 50% of the reactor volume.

Therefore, in order to model a dehydrogenation reactor, the hydrogen release from evaporated H12-BT must also be described. The kinetic measurements are carried out in a pellet string tube reactor. This paper deals with the estimation of a kinetic approach for hydrogen release from liquid and evaporated H12-BT. In order to validate the quality of the kinetic models, comparative measurements were carried out in other reactors. In addition, the differences for the reactions of liquid and vaporised H12-BT have been evaluated and discussed.