Ultra-small Mo2N on SBA-15 as a highly efficient promoter of low-loading Pd for catalytic hydrogenation

Abstract

Decreasing Pd usage whilst maintaining a superior performance is promising, but remains a challenge in the catalytic field. Herein, we have demonstrated the highly efficient promotion of Mo₂N with a reduced amount of Pd for the liquid-phase hydrogenation reaction. The Mo₂N (2–3 nm) was uniformly anchored onto mesoporous SBA-15 by using PMo₁₂ as the Mo source. The small size and good dispersion of Mo₂N is favourable for allowing their effective contact with post-loading Pd. This good contact is conducive to developing a synergistic catalyst, which was verified by studying the liquid-phase hydrogenation of p-nitrophenol (PNP) to p-aminophenol (PAP) with NaBH₄ as the H source. The conversion ability of PNP to PAP on 1 wt% Pd–Mo₂N/SBA-15 was vastly superior to 1 wt% Pd/SBA-15 and even better than 20 wt% Pd/SBA-15. The low-Pd, highly efficient catalysis is ascribed to the transfer of the electrons from Mo₂N to Pd for the easy activation of H. The synergy can be affected by the type of support used. SBA-15 is superior to SiO₂ and the other supports, which could be related to the large surface area and the plentiful number of pores on SBA-15, which is favourable to the dispersion of Pd and Mo₂N, and the transfer/diffusion of the reactants. In particular, a highly efficient catalyst can be achieved at an even more reduced Pd loading (0.05 wt%). The current method describes the design of a highly efficient catalyst for the hydrogenation reaction using low amounts of noble metals.