Influence of Zirconia Phase on the Performance of Ni/ZrO2 for Carbon Dioxide Reforming of Methane

The influence of crystal phase of zirconia on the performance of Ni/ZrO2 catalysts for dry reforming of methane was investigated. Ni/ZrO2 catalysts were prepared by incipient wetness impregnation method with 5% Ni loading, using amorphous, monoclinic, and tetragonal ZrO2 as supports. The catalysts were characterized by N-2 adsorption desorption, X-ray diffraction (XRD), temperature-programmed reduction with hydrogen (H-2-TPR), temperature-programmed oxidation with O-2 and hydrogenation (O-2-TPO/TPH), temperature programmed oxidation with CO2 (CO2-TPO) and transmission electron microscopy (TEM). Ni nanoparticles supported on amorphous ZrO2 (Ni/am-ZrO2) exhibited higher activity and better stability, which was suggested to be closely associated with the higher Ni dispersion due to the presence of mesoporous amorphous ZrO2. In contrast, Ni/t-ZrO2 and Ni/m-ZrO2 suffered a continuous decline of activity during 50 h of TOS, related to the sintering of Ni and carbon deposition. Additionally, it was found that both Ni particle size and the crystal phase of zirconia strongly influenced the nature of deposited carbon. The coke deposited on Ni/t-ZrO2 displayed the highest formation rate and the lowest activity towards O-2 and CO2, while significant deactivation was observed on Ni/m-ZrO2 owing to the encapsulating carbon. The stability of catalysts was significantly influenced by the carbon morphology.