(219d) Desulfurization of Liquid Fuels by Adsorption for Fuel Cell Applications

Power generation by portable fuel cells require a source of hydrogen. Liquid fuels are a suitable source due to their availability and high hydrogen content. The major drawback to the use of liquid fuels in portable fuel cells as a source of hydrogen is their sulfur content. EPA regulations have lowered the sulfur level in the commercial fuels to 30 ppmw S for gasoline and 15 ppmw S for diesel, this makes them ideal fuel for fuel cells in transportation and portable applications but the sulfur level in the logistic fuels is still high 3,000 ppmw S for jet fuels (JP-8, JP-5) and 10,000 ppmw S for naval distillate (NATO F-76). The effective utilization of transportation fuels in fuel cell applications requires removal of refractory sulfur species (organosulfur compounds) to below 0.1 ppm. Low temperature fuel cells (e.g. PEM) require clean (essentially pure) hydrogen feed to prevent the poisoning of the anode catalyst. Even the more robust high temperature fuel cells (e.g., solid oxide fuel cells) are poisoned with low levels of sulfur contaminants. Sulfur removal is critical for fuel cells and adsorption is a promising technology for accomplishing such low levels of sulfur. TDA has developed a regenerable sorbent-based fuel desulfurization system that can easily integrate with any fuel cell fuel processor. TDA's adsorbent removes all of the refractory organic sulfur compounds from the fuel, which is still in the liquid phase and reduces the total fuel sulfur content to sub-ppm levels (e.g., less than 0.1 ppmw). For portable fuel cell applications TDA's adsorbent can be used in an expendable mode or in a centralized multi-bed regenerable desulfurization system. TDA has built a four-bed prototype liquid fuel desulfurization system, which will be tested with various liquid fuels. The test results from the prototype unit testing and the cyclic regeneration and stability data for TDA's SulfaTrap^TM ?D1 (TDA's liquid fuel desulfurization sorbent) will be discussed in this paper.