Effects of la addition to Ni/Al₂O₃ catalysts on rates and carbon deposition during steam reforming of n-dodecane

Steam reforming of n-dodecane on La-Ni/γ-Al₂O₃ catalysts was investigated at a relatively low temperature (773 K) to elucidate the catalytic behavior at the inlet of a practical reformer. The addition of lanthanum to the Ni/γ-Al₂O₃ formulation completely suppressed carbon deposition, which otherwise occurs to a significant extent on unmodified Ni/γ-Al₂O₃. Modification with La also enhanced the initial turnover rates of hydrogen formation. The La-Ni/γ-Al₂O₃ catalysts, however, deactivated with increased time-on-stream at a high steam-to-carbon ratio of 3.5, because of oxidation of the active Ni metal. Reduction at 873 K almost fully regenerated the catalytic activity, indicating that the deactivation was not primarily a result of sintering or carbon deposition, but was due to the oxidation of active Ni metal.