Pushing activity and stability of LOHC dehydrogenation catalysts by strict LOHC quality protocols

Hydrogen storage and transportation using liquid organic hydrogen carrier (LOHC) systems is a promising way to make use of the existing infrastructure for fuels (tank farms, tank vehicles) for the ramp-up of a future hydrogen economy. For a cost-efficient implementation of LOHC-based technologies the stability of both the hydrogen carrier compounds and the applied hydrogenation/dehydrogenation catalysts is of critical relevance. Herein, we show that catalyst stability in the continuous dehydrogenation of the LOHC compound perhydro benzyltoluene (H12-BT) benefits strongly from a combination of catalyst material pretreatment (drying and reduction) and LOHC purification (removal of volatiles and selective adsorption of oxygenated impurities). This has been demonstrated by using a pellet string reactor with only 30 catalyst pellets (commercial Elemax D101, Clariant), in which only one pellet fills the cross-section of the reactor that is hardly wider than the diameter of the applied catalyst pellets. With this specific reactor the ratio of feed flow to catalyst mass is 20–60 times higher than in a typical technical dehydrogenation reactor allowing us to quantify detrimental effects of impurities on catalyst stability faster and more accurately. Our study demonstrates that all impurities leading to CO formation in the reactor have a significant negative influence on the catalyst stability. Removing such impurities from the catalyst and the LOHC feed enables almost stable dehydrogenation performance in the string reactor for 50 h time-on-stream.