Continuous Dehydrogenation of Perhydro Benzyltoluene in a Three-phase Stirred Tank Slurry Reactor

Liquid organic hydrogen carriers (LOHCs) offer a promising solution for the safe and scalable storage and transportation of hydrogen. While efficient hydrogenation is less of a challenge, technical dehydrogenation poses multifold hurdles due to its endothermic nature, slow kinetics, and highly dynamic three-phase conditions. This study presents a continuous three-phase stirred tank slurry reactor to overcome these obstacles for the LOHC benzyltoluene, which is currently dehydrogenated technically using multiphase fixed-bed reactors. The slurry reactor was evaluated systematically by variation of stirrer speed, feed rate, and operation temperature to optimise continuous hydrogen release. Long-term testing using optimised operation conditions at technically relevant temperature and pressure levels demonstrated stable operation with efficient phase separation, sustained catalyst activity, and minimal LOHC degradation. Restart experiments showed that mechanical agitation effectively restores performance. However, repeated rapid on-off cycles are detrimental for operational stability. Overall, the reactor design successfully mitigates key limitations often associated with LOHC dehydrogenation, such as catalyst dewetting, heat management, and volumetric expansion due to hydrogen release, while enabling efficient and stable operation. In addition, continuous hydrogenation was demonstrated confirming the ability to operate in both charge and discharge mode, achieving a degree of hydrogenation of 99.8%. These findings contribute to the development of integrated LOHC systems for a flexible, low-carbon hydrogen infrastructure.