Stability and Activity of Rhodium Promoted Nickel-Based Catalysts in Dry Reforming of Methane

The rhodium oxide (Rh₂O₃) doping effect on the activity and stability of nickel catalysts supported over yttria-stabilized zirconia was examined in dry reforming of methane (DRM) by using a tubular reactor, operated at 800 °C. The catalysts were characterized by using several techniques including nitrogen physisorption, X-ray diffraction, transmission electron microscopy, H₂-temperature programmed reduction, CO₂-temperature programmed Desorption, and temperature gravimetric analysis (TGA). The morphology of Ni-YZr was not affected by the addition of Rh₂O₃. However, it facilitated the activation of the catalysts and reduced the catalyst's surface basicity. The addition of 4.0 wt.% Rh₂O₃ gave the optimum conversions of CH₄ and CO₂ of ~89% and ~92%, respectively. Furthermore, the incorporation of Rh₂O₃, in the range of 0.0-4.0 wt.% loading, enhanced DRM and decreased the impact of reverse water gas shift, as inferred by the thermodynamics analysis. TGA revealed that the addition of Rh₂O₃ diminished the carbon formation on the spent catalysts, and hence, boosted the stability, owing to the potential of rhodium for carbon oxidation through gasification reactions. The 4.0 wt.% Rh₂O₃ loading gave a 12.5% weight loss of carbon. The TEM images displayed filamentous carbon, confirming the TGA results.