Hydrogen Loading and Release Potential of the LOHC System Benzyltoluene/Perhydro Benzyltoluene over S–Pt/TiO2 Catalyst

Abstract

Platinum on oxide catalysts are established for the loading and unloading of liquid organic hydrogen carriers (LOHCs). These catalysts have been optimized so far to provide high reaction rates and consequently high power densities in the loading and unloading reactor units. However, high temperatures are required for catalytic dehydrogenation (hydrogen release), which can result in low energy efficiency. Another challenge is to avoid the formation of the undesired side product methylfluorene. In this work, the optimized S–Pt/TiO₂ catalyst was successfully applied in the hydrogenation and dehydrogenation of the commercially attractive LOHC system benzyltoluene/perhydro benzyltoluene (H0-BT/H12-BT). Methylfluorene was not detected using S–Pt/TiO₂, while utilizing the S–Pt/Al₂O₃ state-of-the-art catalyst caused methylfluorene formation. The S–Pt/TiO₂ catalyst combines the prevention of this side reaction with a competitive hydrogen release rate. Hence, the application of S–Pt/TiO₂ in the LOHC cycle was further studied. It was shown that the catalytic hydrogen release can be accelerated by increasing the temperature, but low reaction temperatures are desired to increase the energy efficiency of the process by enabling heat integration between the hydrogen release and waste heat generation from energetic hydrogen use cases. Accordingly, the potential for low-temperature hydrogen release at reduced pressure was demonstrated by a systematic investigation of pressure influence. With pressure reduction, the hydrogen release productivity continuously increased. Finally, the hydrogenation and dehydrogenation productivity obtained in this work was compared to results reported in the literature to demonstrate the implementation potential of the optimized S–Pt/TiO₂ catalyst.