Gas-Phase Sulfur Sorbent
The sorbent for gas phase sulfur removal is made of transition metal (such as copper, silver, iron, etc.) promoted ZnO supported on silica particles (60-80 mesh). Due to the support and active phase structure as well as the dopant, intra-particle mas transfer and lattice diffusion become extremely fast even at low temperatures (i.e. room temperature). As a result, the sorbent has high ZnO utilization and high sulfur capacity. For the same reason, the sorbent can be regenerated at lower temperatures and used for multiple cycles.
During regeneration, no special media such as inert gas or reducing agents are required. Air or an air-steam mixture can easily recover sulfur removal capacity. Most commercial sulfur sorbents require a regeneration of temperature of 600°C, with regeneration efficiencies less than that of IntraMicron's sorbents. The sorbent developed by IntraMicron can regenerate at 550°C because of its highly porous structure. After the first regeneration cycle, its sulfur capacity drops to 80% of the original capacity, but this capacity is stable for at least 50 high-temperature regeneration cycles. Low temperature regenration is also feasible. Although sorbent capacity recovery is less effective at lower temperatures, most of the sorbents capacity can still be recovered at temperatures exceeding 300°C. The balanced desulfurization performance and the ease of operation make this sorbent a superior candidate for applications in mobile fuel cell systems in terms of reduced reactor weight and volume, low cost, process convenience, and ease of integration. This sorbent is especially suited to dusulfurization applications for PEM fuel cells and solid oxide fuel cells, even during cold startup.