Rh-Ni/MgAl2O4 catalyst for steam reforming of methane: Effect of Rh doping, calcination temperature and its application on metal monoliths

Abstract

The effect of adding small amounts Rh noble metal to 15 wt.% Ni/MgAl2O4 catalyst were studied for the steam reforming of methane. For this purpose, two series of catalysts were prepared and then the most active catalyst from this study was selected for metal monolith application. Both series of catalysts were tested at ambient and high pressures conditions. The first series of catalyst was used to determine the optimum Rh concentration by varying the Rh concentration from 0.1 to 1.0 wt.%. It was found that an optimum concentration of 0.5 wt.% Rh showed the highest activity and stability. The second series of catalysts containing 0.5 wt.%Rh-15 wt.% Ni/MgAl2O4 was used to study the effect of calcination temperature on the activity and stability. Studies on the second series of catalysts showed that the catalyst prepared by sequential impregnation and calcined at lower temperatures (600 °C after each Ni and Rh impregnation) showed the highest activity and stability. Among the several changes in factors detected due to Rh doping, the increase in catalytic activity for the catalyst calcined at lower temperatures was mainly attributed to its higher degree of reduction and higher abundance of Ni-Rh active sites. The most active Rh-Ni/MgAl2O4 catalyst was washcoated on FeCralloy metal monoliths and the performance compared with a packed bed and Ni/MgAl2O4 washcoated metal monolith. A significant increase of 24% in methane conversion was observed for Rh-Ni/MgAl2O4 washcoated metal monolith in comparison to NiMgAl2O4 washcoated metal monolith.