Effect of Holmium Oxide Loading on Nickel Catalyst Supported on Yttria-Stabilized Zirconia in Methane Dry Reforming.

The carbon dioxide reforming of methane has attracted attention from researchers owing to its possibility of both mitigating the hazards of reactants and producing useful chemical intermediates. In this framework, the activity of the nickel-based catalysts, supported by yttria-stabilized zirconia and promoted with holmium oxide (HoO), was assessed in carbon dioxide reforming of methane at 800 °C. The catalysts were characterized by N-physisorption, H temperature-programmed reduction, temperature-programmed desorption of CO, X-ray diffraction, scanning electron microscopy (SEM) together with energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) techniques. The effect of holmium oxide weight percent loading (0.0, 1.0, 2.0, 3,0, 4.0, and 5.0 wt %) was examined owing to its impact on the developed catalysts. The optimum loading of HoO was found to be 4.0 wt %, where the methane and carbon dioxide conversions were 85 and 91%, respectively. The nitrogen adsorption-desorption isotherms specified the mesoporous aspect of the catalysts, while the SEM images displayed a morphology of agglomerated, porous particles. The TEM images of the spent catalyst displayed the formation of multiwalled carbon nanotubes. TGA of the 4.0 wt % of HoO catalyst, experimented over 7-hour time-on-stream, displayed little weight loss (<14.0 wt %) owing to carbon formation, indicating the good resistance of the catalyst to carbon accumulation due to the enhancing ability of HoO and its adjustment of the support.