Trace ultrafine Ru nanoparticles on Ni/Al hydrotalcite-derived oxides supports as extremely active catalysts for N-ethylcarbazole hydrogenation

Liquid organic hydrogen carriers (LOHCs) is a promising hydrogen storage technology and has become a hot issue. However, there is still a shortage of LOHCs hydrogenation catalysts that can balance cost and catalytic performance. In this work, a series of Ni/Al hydrotalcite-derived oxides (LDOs) were prepared with different Ni/Al ratios and preparation methods, on which trace ultrafine Ru nanoparticles (0.5 wt%, 1 wt%, 1.5 wt%) were supported. The activities were investigated for the hydrogenation of N-ethylcarbazole (NEC), one of the most promising liquid organic hydrogen carriers. Characterizations including XRD, XPS, SEM, TEM and H₂-TPR indicate the composition of Ni/Al-LDOs and reveal three kinds of Ni/Al interactions existed in Ni/Al-LDOs. The influences of Ni-Al interactions on the size of Ru NPs supported on Ni/Al-LDOs and on the NEC hydrogenation activity were also explored. The results show that 1.5 wt% Ru-Ni₁Al₂-LDO₃₀₀ has the best catalytic performance for NEC hydrogenation, with which can achieve up to 5.5 wt% hydrogen absorption at 150℃ and 8 MPa for 12 min, and the yield of 12H-NEC can reach 100 % for 60 min. In other words, the catalytic performance of 1.5 wt% Ru supported catalyst is superior to 5 wt% Ru/Al₂O₃ catalyst commonly used for NEC hydrogenation. This work provides a new idea for preparing catalysts with low cost and high performance by tuning the structure of Ni/Al-LDO supports and the size of Ru NPs.