Breakthrough Characteristics of Reformate Desulfurization Using ZnO Sorbents for Logistic Fuel Cell Power Systems

Sulfur breakthrough behaviors during reformate desulfurization were investigated using a novel ZnO-based sorbent with minimized mass transfer resistance. The presence of CO, CO 2, or water affected the breakthrough characteristics of H 2 S and carbonyl sulfide (COS). CO and CO 2 did not significantly affect the reaction between H 2 S and ZnO, but they reacted with H 2 S to form COS, which cannot be efficiently removed by ZnO. The mechanisms of COS formation via two different pathways were also investigated. CO reacted with H 2 S to form COS homogeneously; CO 2 reacted with H 2 S heterogeneously on the sulfide surface. COS formation by CO and CO 2 was suppressed by H 2 and water. Water also severely hindered the reaction between ZnO and H 2 S and significantly decreased H 2 S breakthrough time. At low water concentrations, sulfur breakthrough was determined by the homogeneous COS formation; at high water concentrations, it was controlled by H 2 S breakthrough. Capacity loss due to COS formation and adsorption of water was also observed. Novel sorbent and process designs are required to improve the desulfurization performance.