Effect of Pt doping on activity and stability of Ni/MgAl2O4 catalyst for steam reforming of methane at ambient and high pressure condition

Abstract

Effect of addition of Pt noble metal to Ni/MgAl2O4 catalyst for steam reforming of methane was studied at atmospheric pressure and at high pressure (10 bar). Pt loading of the catalyst was varied from 0.01 wt.% to 1.0 wt.%. Catalyst characterization studies showed that the degree of reduction of the catalyst increased from 44.9% for Ni/MgAl2O4 to 67.7% for the catalyst doped with 1.0 wt.% Pt, which was attributed to H2 spill over effect. With increasing Pt loading, the metal dispersion passed through a maxima and the highest dispersion of active metals was obtained with a Pt doping of 0.1 wt.%. Increase in Pt concentration had no effect on the concentration of NiAl2O4 that had already formed during calcination at 850 °C after nickel impregnation. Addition of Pt significantly increased the catalytic activity of Ni/MgAl2O4 for the steam reforming of methane at both reactor pressures. Comparison of Pt doped Ni/MgAl2O4 with Pt/MgAl2O4 showed that only lower loading of Pt produced a synergetic effect. The highest catalytic activity was obtained with 0.1 wt.% Pt doped Ni/MgAl2O4. Above this Pt loading the catalytic activity decreased. The highest activity of 0.1 wt.% Pt doped catalyst was credited to an increase in active metal dispersion, while the decrease in catalytic activity on further addition of Pt was attributed to agglomeration of active metals. High pressures decreased the conversion and stability of each Pt doped catalyst. However, at the same operating conditions there was a marginal increase in the catalyst stability due to Pt doping and the decline in catalyst activity with run time was lowest for 0.1 wt.% Pt doped Ni/MgAl2O4 catalyst.