Interaction of Ni(II,III) and sol-gel derived ZrO2 in Ni/ZrO2 catalyst system

Abstract

NiO/ZrO2 catalyst has a selectivity for producing higher hydrocarbons, whereas NiO on classical supports gives rise to methanation of CO + H2 mixture. In this study, tetragonal and monoclinic ZrO2 gel carriers have been synthesized using sol-gel method. The interaction of nickel ions with a sol-gel derived catalyst support has been investigated using FTIR, DTA, and XPS. It is found that the nickel ions diffuses into the ZrO2 continuously over 400 to 600 °C for both tetragonal and monoclinic ZrO2, and forms a thermodynamically stable Ni/ZrO2 solid solution at elevated calcination temperatures. Higher nickel surface contents are observed in tetragonal ZrO2. In addition to Ni2+, Ni3+ ions are also detected in Ni/ZrO2 system. Cation ratio of Ni2+/Ni3+ peaks at 700°C in the tetragonal ZrO2. In the monoclinic case, the ratio remains constant at different elevated temperatures. The diffusion activation energy for Ni(II,III) on both tetragonal and monoclinic in ZrO2 is 0.40 eV.