Effect of preparation method of Ce_0.8Gd_0.2O_1.9 supports on sulfur tolerance of supported-platinum catalysts for steam reforming of iso-octane

The fluorite-type Ce_0.8Gd_0.2O₁₀₉(CGO) oxide supports were synthesized by citric acid sol-gel, hexamethylenetetramine coprecipitation and oxalic acid coprecipitation, respectively. The Pt/CGO catalysts were prepared by highly dispersing Pt onto the pore surfaces of the as-made CGO supports using incipient wetness impregnation. Sulfur tolerance of the catalysts was tested in steam reforming of isooctane at 750°C and a WHSV (isooctane) of 1.0 h^-1 with a steam/C molar ratio of 3, with thiophene as sulfur source. It was found that the preparation method of CGO oxide supports influenced sulfur tolerance of the catalysts. The catalyst which using the support that was synthesized by citric acid sol-gel method exhibited the best sulfur tolerance. This catalyst maintained its activity and selectivity in the entire 100 h test with 300 μg·g^-1 sulfur. In contrast, the catalysts which using the supports that were synthesized by oxalic acid coprecipitation and hexamethylenetetramine coprecipitation, both lost their activity slowly to -90% and -82%, because of their poorer thermal stability and weaker interaction between Pt and CGO oxide at their interface. It was also found that the sulfur tolerance of the catalysts was not correlated with their oxygen storage capacity (OSC). In addition, three catalysts all showed good resistance to carbon deposition in the steam reforming of isooctane with 300 μg·g^-1 sulfur.