NOVELTY - Fuel cell system (10) comprises catalytic reactor having sulfur oxidation catalyst including Group-VIII noble metal and iron; where reactor is configured to contact sulfur-containing hydrocarbon fuel and oxidant to form sulfur oxides; and iron concentration in catalyst is about (0.5-40 wt.%); and adsorbent fluidly disposed between catalytic reactor and fuel cell, to adsorb sulfur oxides, where catalytic reactor and adsorbent are operative to remove sulfur-containing compounds from sulfur-containing hydrocarbon fuel prior to supplying hydrocarbon fuel to fuel cell.    USE - In fuel cell systems, as desulfurization systems to remove or reduce sulfur content from a hydrocarbon fuel for use in other systems and processes.    ADVANTAGE - The use of catalysts such as platinum with high combustion activity facilitates operation at lower temperatures and reduces the size of catalytic reactor. As platinum is very expensive, hence it is desired to use only limited amounts of platinum in commercial applications, to reduce component cost. Where desulfurization system is employed in conjunction with fuel cell system, the desulfurization system has high degree of thermal and mechanical integration with the fuel cell system. The desulfurization system removes sulfur (e.g. sulfur-containing compounds) from the fuel and thus reduces or prevents damage to reformer and/or fuel cell stack. The iron concentration in sulfur oxidation catalyst is selected to provide greater desulfurization of sulfur-containing hydrocarbon fuel than that provided by catalysts having platinum as the only active metal.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) desulfurization system (16) comprising sulfur oxide trap connected and disposed downstream of catalytic reactor, where sulfur oxide trap is configured to capture sulfur oxides from feed stream; and    (2) method of operating fuel cell system involves supplying sulfur-containing hydrocarbon fuel and oxidant to catalytic reactor; contacting sulfur-containing hydrocarbon fuel and oxidant with sulfur oxidation catalyst; oxidizing sulfur-containing compounds in hydrocarbon fuel using oxidant and sulfur oxidation catalyst; capturing sulfur oxides using sulfur oxide trap; and providing desulfurized fuel to component of fuel cell system.    DESCRIPTION OF DRAWING(S) - The figure shows schematic diagram of fuel cell system.    Fuel cell system (10)    Fuel cell stack (12)    Reformer (14)    Desulfurization system (16)    Electrical load (18)    Electrical power lines (20)