Desulfurization of hot reformate gas, which is produced by catalytic partial oxidation (CPOX) or autothermal reforming of heavy fuels, such as JP-8, is required prior to using the gas in a solid oxide fuel cell (SOFC). This requires development of sorbent materials with favorable sulfidation equilibria, good kinetics, and high structural stability and regenerability at the SOFC operating temperature (650-800oC) to avoid heat exchanger penalties. Sorbent performance stability in cyclic operation of sulfidation and regeneration at such high temperatures imposes major constraints on the choice of suitable materials. Cerium and lanthanum oxide-based materials have been developed in our lab as high-temperature regenerable sorbents for the removal of H2S upstream of the SOFC anode.1,2 A major finding of our research is that H2S can be reversibly adsorbed onto the cerium and lanthanum oxide surfaces at temperatures as high as 800 oC, on both fresh or pre-sulfided sorbents. The adsorption and desorption processes are very fast; thus, removal of H2S to sub parts per million levels is achieved at very short (millisecond) contact times. Any type of sulfur-free gas, including water vapor, can be used to regenerate the sorbent surface. Preferably, the anode off-gas stream is used to sweep the desorbed H2S to a burner1. Detailed studies of cyclic sorbent sulfidation/regeneration under different operating conditions will be presented. H2S-TPD results suggest that reversible H2S adsorption/desorption would be possible with lanthana, ceria and their mixtures at temperatures as low as 350 oC. Therefore, this type of sorbent and desulfurization method may be used for polishing reformate gas streams for any use, including low-temperature PEM fuel cells. H2S adsorption uptakes and kinetics of adsorption will be reported in this presentation. . References 1 M. Flytzani-Stephanopoulos; M Sakbodin; Z. Wang, Science 2006, in press
2. Z. Wang ; M. Flytzani-Stephanopoulos, Energy and Fuels, 2005, 19 (5), 2089 ¨C2097