Deactivation due to sulfur poisoning and carbon deposition on Rh-Ni/Al2O3 catalyst during steam reforming of sulfur-doped n-hexadecane

Deactivation by sulfur poisoning and carbon deposition of steam reforming catalyst used for hydrogen production from diesel or jet fuel creates a significant barrier to commercialization of fuel cell technologies. Steam reforming of n-hexadecane on a rhodium/nickel catalyst supported on γ-alumina, a formulation previously proposed for steam reforming of logistic fuel, was used to study the deactivation mechanisms. The steam reforming activity was measured in terms of H2 yields and showed that the catalysts were stable in the absence of sulfur but deactivated over a period of 10 h when sulfur was present at high loading. Stability and activity were higher with higher amounts of Rh content when Ni was kept constant. TEM-EDS of used catalysts revealed preferential adsorption of sulfur on the surface of Ni crystallites; EDS and XRD analysis showed no bulk sulfide formation. Excessive carbon deposition was observed during steam reforming of sulfur-containing fuel. Blocking of reactant species on the surface of the catalyst due to the formation of aromatic/polymeric carbon on the support was also seen, although higher Rh content inhibited this phenomenon.

A mechanism of deactivation for steam reforming of sulfur-containing fuel on Rh-Ni/γ-alumina catalyst has been developed. Sulfur poisoning on nickel sites decreases the rate of steam reforming. Eventually, carbon deposition throughout the catalyst causes an accumulation of aromatic/polymeric carbon on the catalyst surface and loss of reforming activity.Figure optionsDownload as PowerPoint slide