Self-regenerative activity of Ni/Mg(Al)O catalysts with trace Ru during daily start-up and shut-down operation of CH4 steam reforming

Ni/Mg(Al)O catalysts doped with trace Ru showed self-regenerative activity during a daily start-up and shut-down (DSS) operation of steam reforming of methane. Formation of RuNi alloy on the surface of fine Ni metal particles on the catalysts was strongly suggested by EXAFS and TPR measurements. The Ni/Mg(Al)O catalyst was passivated by the oxidative incorporation of Ni0 to Ni2+ in Mg(Ni,Al)O periclase, and trace Ru assisted the regeneration of Ni metal from the Ni2+ by hydrogen spillover. Even notably sintered Ni metal particles on the Ni/Mg(Al)O catalyst by steaming were rapidly redispersed, resulting in the revelation of the high and stable activity during the DSS operation. The self-regeneration of the RuNi/Mg(Al)O catalysts can be achieved by the continuous rebirth of active Ni metal species assisted cooperatively by both Ni2+ → Ni0 reduction by hydrogen-spillover via trace Ru metal or RuNi alloy and reversible reduction–oxidation between Ni0 and Ni2+ in Mg(Ni,Al)O periclase.