Effect of the Ni/Cu ratio on the composition and catalytic properties of nickel-copper alloy in anisole hydrodeoxygenation

The activity of NiCu-SiO₂ catalysts with a metal content of 90% and different Ni/Cu ratios has been investigated in the hydrodeoxygenation of anisole, a model compound of bio-oil, at 280°C and 6 MPa. A homogeneous phase composition of the active component has been synthesized by the co-decomposition of nickel and copper nitrates followed by the introduction of SiO₂ as a stabilizer. The resulting catalysts have been characterized by temperature-programmed reduction, X-ray powder diffraction, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy combined with energy-dispersive microanalysis. The bulk and surface composition of active-component particles has been determined by XPS and X-ray diffraction. In all of the catalysts containing 15–85 wt % Ni, there are two types of solid solutions. One has a constant composition, Cu_0.95Ni_0.05, which is independent of the Ni/Cu ratio in the catalyst; in the other, the nickel stoichiometry increases with an increasing Ni content of the active component. A correlation has been established between the Ni/Cu ratio and the rate constants of the reaction examined and between the Ni/Cu ratio and the degree of hydrodeoxygenation for all samples. The most active catalyst is Ni85Cu5-SiO₂.