Steam reforming of methane over alumina supported nickel
catalysts: Influence of calcination temperature, gold doping and sulfur addition

Abstract

Alumina supported nickel and gold-doped nickel catalysts have been investigated for their use as hydrocarbon steam reforming catalysts. The influence of calcination temperature during preparation has been investigated using a variety of techniques including X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), BET surface area analysis, scanning electron microscopy (SEM) and temperature-programmed reduction (TPR). It has been shown that the nickel phases present and their subsequent reducibility are strongly dependent upon the calcination temperature during preparation. As the calcination temperature is increased nickel aluminate (NiAl2O4) is formed and nickel oxide–support interactions increase. The addition of gold to the catalyst increases nickel oxide support interactions, lowering the sample reducibility and increasing formation of NiAl2O4 at lower calcination temperatures.

The calcination temperature significantly influences the steam methane reforming characteristics under both stoichiometric and methane-rich reaction conditions and the presence of unreduced NiAl2O4 significantly alters catalytic activity. Under the reaction conditions employed, the presence of gold provides no long-term benefit towards catalyst performance, resulting in a reduced reforming activity, especially at lower reaction temperatures, and in certain cases an increase in carbon laydown. Sulfur addition to the reaction mixture results in catalyst poisoning and in some cases complete deactivation, particularly at low reaction temperatures. However, sulfur addition does significantly increase resistance to carbon deposition. The addition of sulfur to the reaction mixtures and gold-doping of catalysts provides an increase in carbon resistance, whilst significantly reducing the rate of sulfur poisoning and increasing catalyst lifetime.
This research discusses the influence of calcination temperature on steam methane reforming activity, catalyst resistance towards carbon formation and sulfur tolerance under variable reforming conditions over alumina supported nickel and gold-doped alumina supported nickel catalysts.