Ru-Ni/Al2O3 bimetallic catalysts with high catalytic activity for N-propylcarbazole hydrogenation

The catalytic hydrogenation of liquid organic hydrogen carriers (LOHCs) is one of the key steps towards large-scale applications. The use of a large amount of noble metals in hydrogenation factories would increase the total cost of the LOHC technology. The partial replacement of ruthenium by another transition metal, i.e., Ni is a potentially effective method. The synthesis and characterization of 5 wt% RuxNi5-x/Al2O3 (x = 0, 1, 2.5, 4, and 5) bimetallic catalysts and their catalytic performance for the hydrogenation of N-propylcarbazole are reported. All catalysts were prepared by a wet chemistry method using a rapid sodium borohydride reduction of the Ni2+ and Ru3+ precursors in alkaline solutions. The catalysts were characterized by TEM, XRD, XPS, nitrogen sorption, ICP-OES, H-2-TPD and CO adsorption. The as-prepared 5 wt% Ru2.5Ni2.5/Al2O3 exhibits the best catalytic activity compared to the as-prepared catalysts with the highest metal dispersion and minimum average particle size of 5.210 nm. The hydrogenation activation energy for 5 wt% Ru2.5Ni2.5/Al2O3 at 150-180 degrees C was estimated to be approximately 12.95 kJ mol(-1). No obvious degradation was observed after 5 cycles of hydrogenation for the 5 wt% Ru2.5Ni2.5/Al2O3 catalyst, indicating that the catalyst has applicable stability. The hydrogen spillover has been proved to occur more easily on the Ru-Ni clusters by theoretical calculations.