A highly active bifunctional Ru–Pd catalyst for hydrogenation and dehydrogenation of liquid organic hydrogen carriers

Abstract

Hydrogen storage and release by liquid organic hydrogen carriers (LOHCs) are achieved by a reversible catalytic hydrogenation and dehydrogenation process. Generally, catalytic hydrogenation and catalytic dehydrogenation require different noble metal catalysts. In this paper, we report a bifunctional Ru–Pd/Al2O3 catalyst with excellent catalytic activity for both hydrogenation and dehydrogenation of LOHCs. All catalysts were prepared by a facile impregnation–hydrogen reduction method, and the catalytic activities were compared by catalytic hydrogenation of N-propylcarbazole and dehydrogenation of perhydro-N-propylcarbazole. The as-prepared Ru-Pd/Al2O3 catalyst exhibits excellent catalytic hydrogenation and dehydrogenation activity, selectivity, and stability. Particularly, the dehydrogenation activity of the Ru–Pd/Al2O3 catalyst is superior to that of the commercial Pd/Al2O3 catalyst, which proves that the positive synergistic effect between palladium and ruthenium nanoparticles enhanced the activity of the Ru–Pd/Al2O3 catalyst. No significant activity decrease was observed for the as-prepared catalysts after three cycles of N-propylcarbazole hydrogenation and three cycles of dehydrogenation. The bifunctional Ru–Pd catalyst has potential commercial applications in large-scale application of LOHC technology.