Role of Iron Oxide in the Promotion of Zn−Ti-Based Desulfurization Sorbents during Regeneration at Middle Temperatures

Zn−Ti-based desulfurization sorbents promoted with iron oxide (Fe 2 O 3 ) were prepared to improve the regeneration properties of ZnO−TiO 2 (ZT) sorbent at middle temperatures in the range of 480−580 °C. Their sulfur-removing capacities and regeneration properties were measured in a fixed-bed reactor during multiple cycles at middle temperatures. The sulfides formed during sulfidation were defined as ZnS and FeS from X-ray diffraction. FeS was quickly converted to an oxide phase during regeneration even at 480 °C, while the regeneration rate of ZnS was very slow in the temperature range of 480−550 °C. The excellent regeneration properties of the new sorbents (ZTF) are explained by the formation of a spinel structure between the iron oxide and zinc oxide, even at low-temperature treatment. In addition, heat released from the exothermic reaction of iron sulfide with oxygen at low regeneration temperatures also plays a role. The zinc sulfides produced from the spinel structure during sulfidation were easily regenerated even at 480 °C, while the zinc oxide sorbents separated from the spinel structure needed a temperature higher than 600 °C for regeneration. The original structures of the sorbents were determined depending on the initial pretreatment conditions, and the structures after regeneration were unchanged.