Continuous dehydrogenation of perhydro benzyltoluene and perhydro dibenzyltoluene in a packed bed vertical tubular reactor - The role of LOHC evaporation

The benzyltoluene- and dibenzyltoluene-based liquid organic hydrogen carrier (LOHC) technology is approaching a level of maturity that enables its large-scale implementation for hydrogen storage and transport applications. To support this progress, our study investigates the continuous dehydrogenation of both LOHC systems in a packed bed tubular reactor equipped with high-resolution temperature measurement. Our experiments cover a wide range of reaction conditions resulting in various degrees of dehydrogenation (DoD). In particular, our study highlights the relevance of LOHC evaporation in the dehydrogenation reactor caused by the large amounts of hydrogen gas formed and consequently the low LOHC partial pressure in the reactor. Evaporation of the LOHC compounds is more pronounced for the benzyltoluene-than for dibenzyltoluene-based system. This leads to a shortening of the residence time in the reactor and less favourable heat transfer properties. Interestingly, these seemingly unfavourable properties of the benzyltoluene-based system are compensated by faster gas phase kinetics and lower convective heat removal from the reactor, resulting in very similar heat consumption values for both systems under continuous operating conditions.