Promoting effect of Ru on Ni/Mg(Al)O catalysts in DSS-like operation of CH4 steam reforming

Effects of Ru addition on the activity and the sustainability of Ni/Mg(Al)O catalysts were investigated in the daily start-up and shutdown (DSS) operation of the steam reforming of CH4. Mg-2.5(Ni-0.5)-Al hydrotalcite was prepared by coprecipitation and calcined to form Mg-2.5(Al,Ni-0.5)O periclase. When the powders of the periclase were dipped in an aqueous solution of Ru(III) nitrate, the hydrotalcite was reconstituted on the surface of Mg-2.5(Al,Ni-0.5)O particles, resulting in the formation of highly dispersed Ru/Ni bimetal supported catalysts after the calcination, followed by the reduction. The addition of Ru on Ni caused a decrease in the reduction temperature of Ni and an increase in the amount of H, uptake on the Ni over the catalyst. Formation of Ru-Ni alloy or strong interaction between Ru and Ni was also suggested. When Ru-Ni-0.5/Mg-2.5(Al)O catalysts were tested in the DSS-like operation under steam purging, the deactivation due to the oxidation of Ni metal by steam was effectively suppressed by hydrogen spillover. Moreover, only 0.05 wt% of Ru loading was enough to effectively suppress the deactivation during the DSS-like operation. (c) 2006 Elsevier B.V. All rights reserved.