Effects of Hydrothermal Conditions of ZrO2 on Catalyst Properties and Catalytic Performances of Ni/ZrO2 in the Partial Oxidation of Methane

Abstract

ZrO2 was prepared via the hydrothermal method and used as the support of nickel catalysts in the partial oxidation of methane to syngas. The hydrothermal conditions (such as hydrothermal temperature, hydrothermal time, and the concentration of NaOH used) necessary for ZrO2 preparation were investigated and optimized. The physicochemical properties of ZrO2 supports and Ni/ZrO2 catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption, temperature-programmed reduction (TPR), and thermogravimetric analysis (TGA). The results showed that low hydrothermal temperatures, short hydrothermal time, and low concentrations of NaOH benefited the formation of tetragonal ZrO2. Elevating the hydrothermal temperature (from 160 °C to 200 °C), prolonging the hydrothermal time (from 6 h to 48 h), or increasing the concentration of NaOH (from 5 wt % to 40 wt %) would lead to the disappearance of tetragonal ZrO2 and an increase in the degree of monoclinic ZrO2 crystallization. The Ni/ZrO2 catalysts with ZrO2 prepared with high NaOH concentration or with ZrO2 prepared at long hydrothermal times possessed excellent catalytic activities and resistance to carbon formation. Whereas the Ni/ZrO2 catalysts with ZrO2 prepared with low NaOH concentration or with ZrO2 prepared at short hydrothermal time deactivated soon because of carbon deposition.