One-pot synthesis Of Cu/ZnO/ZnAl2O4 catalysts and their catalytic performance in glycerol hydrogenolysis

Abstract

In this work, a series of Cu/ZnO/ZnAl₂O₄ catalysts with different metal molar fractions (Cu : Zn : Al) were successfully prepared using a one-pot method via the evaporation-induced self-assembly (EISA) of Pluronic P123 and the corresponding metal precursors. The catalysts were characterized using N₂ adsorption, H₂ temperature-programmed reduction (H₂-TPR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectra (XPS). The catalytic properties of the resulting Cu/ZnO/ZnAl₂O₄ with different molar fractions of metals were investigated for the selective hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO). It was observed that the ZnAl₂O₄ support exerts a strong positive effect on the catalytic activity of the copper-based catalysts, and the presence of ZnO further improves the catalytic activity of the Cu/ZnAl₂O₄ catalysts. The Cu/ZnO/ZnAl₂O₄ catalyst (Cu₁₀Zn₃₀Al₆₀, Cu/Zn/Al molar ratio is 10 : 30 : 60), which was the best catalyst, exhibited the highest yield (79%) of 1,2-PDO with 85.8% glycerol conversion and 92.1% 1,2-PDO selectivity at 180 °C reaction temperature in 80 wt% glycerol aqueous solution over 10 h reaction time. The high catalytic activity was attributed to the presence of the ZnAl₂O₄ support, the strong interaction between ZnO and Cu nanoparticles and the small particle size of ZnO and Cu. Moreover, the Cu/ZnO/ZnAl₂O₄ catalysts exhibited higher stability than Cu/ZnO and Cu/ZnO/Al₂O₃ catalysts prepared by a co-precipitation method during consecutive cycling experiments, which is due to the high chemical and thermal stability of crystalline ZnAl₂O₄ under harsh reaction conditions.