Monday, November 5, 2007 - 9:20 AM

Advanced Adsorbents For Ultra Deep Desulfurization Of Logistic Fuels Using Micro-Fiber Entrapped Particles

Sachin Nair1, Hongyun Yang2, and Tatarchuk Bruce2. (1) Center for Microfibrous Materials Manufacturing, Department of Chemical Engineering, Auburn University, 230 Ross Hall, Auburn, AL 36849, (2) Chemical Engineering, Auburn University, 230 Ross Hall, Auburn, AL 36849

Reformers providing hydrogen for fuel cell systems such as PEM stack requires feed streams having ultra low concentrations of sulfur. Conventional desulfurizing processes such as HDS that operate at extreme conditions sometimes are not effective in removing high molecular weight sulfur compounds. Adsorptive desulfurization at room temperature in the liquid phase offers an alternative solution, having several advantages such as operability at ambient conditions and the capacity to run multiple adsorption cycles. The minimum ancillary support systems required for such an adsorption configuration is preferred for portable reformers. Several new compositions consisting of a metal precursor as the primary active component supported on SiO2/Al2O3/TiO2 were prepared and tested for their effectiveness in removing sulfur compounds from jet fuel (JP5) with a total sulfur content of 1172 ppmw. Among the adsorbents, Ag supported on SiO2/Al2O3/TiO2 showed an exceptional capacity for sulfur removal. Several studies were performed to determine the optimum metal loading, pressure drop with respect to the particle size distribution, regenerability and multi-cycle performance. Ag loading on the TiO2 support between 2-6% by weight showed the highest sulfur capacity of 6mg/g of Ag/TiO2. Ten adsorption and regeneration cycles were performed on the composition after which the adsorbent retained 90% of the breakthrough sulfur capacity. The study showed that the composition can be regenerated in a flowing air stream at temperatures ranging between 170 and 500C. The concept of a polishing filter that is applied at the down stream of a packed bed to enhance adsorption capacity significantly has been successfully applied to gas phase systems. This work applies the same technology for desulfurization of liquid hydrocarbon streams. Particles of size (50-250m) were entrapped in a sinter-locked network of glass fiber media. The resulting media was loaded at the exit of the packed bed, a configuration known as a composite bed. At breakthrough sulfur concentration of 1 ppmw, the composite bed demonstrated a capacity of 0.7mgS/g compared to 0.23mgS/g for the packed bed. This three fold enhancement in capacity reduces the required bed depth consequently reducing heat requirements during regeneration and effectively improving duty cycle.