Highly efficient alloyed NiCu/Nb2O5 catalyst for the hydrodeoxygenation of biofuel precursors into liquid alkanes

Abstract

Hydrodeoxygenation (HDO) is a crucial process for the synthesis of biofuels from renewable biomass. Here, several bimetallic Ni–M/Nb₂O₅ catalysts (M = Fe, Co, Cu) were synthesized and evaluated in the HDO of biofuel precursors (aldol adduct of furfural with acetone) to liquid alkane and it was found that Ni–Cu/Nb₂O₅ has the best performance (86.5% yield of octane and 5.1% yield of heptane). Various characterization techniques show that Ni–Cu alloy is formed over the Ni–Cu/Nb₂O₅ catalyst, which may have the main active metal sites. Moreover, the Ni–Cu alloy has more sites for the adsorption–activation of H₂, leading to the high activity. During the HDO process, the ring-opening of the intermediate butyl-tetrahydrofuran (BTHF) and the conversion of octanol are two rate-determining steps. The kinetic study confirms that the ring-opening of BTHF over Ni–Cu/Nb₂O₅ is more favorable than that over Ni/Nb₂O₅. More importantly, the Ni–Cu alloy significantly restrained the undesirable decarbonylation due to the weak adsorption of carbonyl, which was key for the efficient production of C_n alkanes. This work provides an in-depth understanding of the role of Ni–Cu alloys and new insights into the design of non-noble metal catalysts for the HDO of biofuel precursors.