Effect of Zn on performance of Ni/SiO₂ for hydrodeoxygenation of anisole

Herein, SiO₂ supported metallic Ni (Ni/SiO₂) and bimetallic Ni-Zn (Ni_xZn/SiO₂) (x represents the Ni/Zn atomic ratio) catalysts were prepared by the incipient wetness impregnation method and their activities were tested in vapor phase hydrodeoxygenation (HDO) of anisole under 0.1 MPa. The characterization results show that Ni-Zn alloy forms in Ni_xZn/SiO₂ after reduction at 550 °C, and a suitable Ni/Zn atomic ratio (30) leads to smaller alloy particle size and consequently more H₂ adsorption amount than others. In the HDO reaction, the formation of Ni-Zn alloy facilitates the direct deoxygenation pathway and suppresses CO methanation and C−C bond hydrogenolysis, which is ascribed to the isolation effect of the Ni atoms by the oxophilic Zn ones. Ni₃₀Zn/SiO₂ gives not only higher anisole conversion but also higher selectivity to benzene than Ni/SiO₂. Therefore, the introduction of a suitable amount of oxophilic Zn in Ni/SiO₂ promotes the HDO of anisole to benzene. Finally, we propose that the Ni₃₀Zn/SiO₂ deactivation is related to the oxidation of Ni-Zn alloy and carbon deposition on the catalyst surface.