Catalytic performance of hydrotalcite-like-compound-derived Ni-metal alloy catalyst for toluene reforming with gasoline engine exhaust model gas as reforming agent

Abstract

Reforming of toluene with model exhaust gas was carried out as Reformed EGR of gasoline engine mainly at 773 K with Ni-M/Mg/Al (Ni 12 wt%, M = Fe, Co, Cu) prepared from corresponding hydrotalcite-like compounds. Ni-Fe/Mg/Al (Fe/Ni = 0.1–0.5) showed clearly higher performance than Ni/Mg/Al in terms of activity, coke-deposition resistance and stability. In contrast, Ni-M/Mg/Al (M/Ni = 0.25, M = Co, Cu) showed similar behaviors to Ni/Mg/Al. The optimum Fe/Ni ratio was 0.25 from toluene conversion and the suppression of benzene formation. Ni-Fe/Mg/Al (Fe/Ni = 0.25) showed high coke-deposition resistance at any position of the catalyst bed, indicating that both substrate decomposition and CO disproportionation were suppressed. The coke amount was not increased even at low temperature (773 K) or higher toluene partial pressure (toluene/H2O/N2/CO2 = 0.5–1.2/11.8/71.2/11.8, molar ratio), but the activity gradually decreased under such conditions. The Ni-Fe alloy nanoparticles in the reduced Ni-Fe/Mg/Al were almost unchanged during the reaction. The deactivated catalyst was regenerated successfully by the treatment under N2 at 873 K, catalytic use at 973 K or re-reduction. These results suggest that the deactivation was caused by carbonaceous species which can be removed easily even by N2 treatment, rather than by graphite-like coke that is difficult to be eliminated via such simple treatment.