691a Supported Silver Based Adsorbents for Deep Desulfurization of Hydrocarbon Fuels for Fuel Cell Applications

Sachin Nair, Center for Microfibrous Materials Manufacturing, Department of Chemical Engineering, Auburn University, 212 Ross Hall, Auburn, AL 36849 and Bruce Tatarchuk, Chemical Engineering, Auburn University, 230 Ross Hall, Auburn, AL 36849.

Low sulfur fuels are essential to the operation of catalytic systems such as fuel reformers as well as fuel cells. Among the several techniques demonstrated for sulfur removal, adsorptive treatment of fuels in the liquid phase provides several advantages over conventional technology such as hydrodesulfurization. Adsorptive systems require lesser ancilliary units, operate at ambient conditions and are capable of multi-cycle operation. They are thus suitable for stationary as well as mobile power generation applications. Supported silver adsorbents demonstrate high capacity for sulfur in liquid hydrocarbon fuels. The Ag/TiO2/SiO2 composition was used to study the desulfurization of JP5 fuel with a total sulfur concentration of 1172 ppmw. Sulfur content was monitored using both a gas chromatograph equipped with a pulsed flame photometric detector as well as a total sulfur analyzer. The saturation sulfur capacity varied between 6 and 10mg/g. Regeneration was demonstrated for 10 cycles using air as the stripping medium while retaining 95% of the sulfur capacity. It was observed that the composition had low capacity for aromatics demonstrating superior selectivity towards sulfur compared to molecular sieve based compositions. The effects of competitive adsorption were determined from the breakthrough characteristics and concentrations of various sulfur species in the fuel output. Better resolution on breakthrough behavior was obtained using model fuels with a few representative sulfur species. The effect of operating conditions such as temperature, fuel flow conditions and bed dimensions were studied. Desulfurization performance on conventional fuels such as diesel, gasoline and JP8 was also observed. Regeneration conditions were optimized using TGA-Mass spectroscopy. This study directs optimization efforts to improve desulfurization efficiency as well as multi-cycle performance of silver based adsorbents.