(491f) Hot Reformate Gas Desulfurization Using Regenerable Cerium and Lanthanum Oxide Sorbents
AIChE Annual Meeting
2006
2006 Annual Meeting
Catalysis and Reaction Engineering Division
Catalytic Hydrogen Generation for Fuel Cell Applications II
Thursday, November 16, 2006 - 10:18am to 10:39am
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
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