(491g) Sulfur Tolerance of Precious Metals Supported on Ceria-Zirconia Catalyst Supports

Ceria-zirconia (CZO) solid solutions impregnated with precious metals are important catalysts because of their oxygen storage capacity, thermal stability and catalytic activity. CZO impregnated with various precious metals (rhodium, platinum, ruthenium, iridium and palladium) at 2% by wt. were synthesized and tested for sulphur tolerance using ppm levels of hydrogen disulfide under water gas shift reaction conditions. Different characterization techniques like X-ray Diffraction, Chemisorption, X-ray Photoelectron Spectroscopy (XPS), and Temperature Programmed Reduction (TPR) were used to characterize the samples exposed to sulfur containing feed streams. Thermodynamic equilibrium calculations were performed to confirm the possible sulphide phases of ceria, zirconia and precious metals under the experimental conditions. The sulfur in the feedstream has adverse effects on the activity of catalyst materials used for a variety of reactions such as water gas shift reactions, steam reforming reactions and the automotive emission control.