Role of iron oxide in the promotion of Zn-Ti-based desulfurization sorbents during regeneration at middle temperatures

Zn-T1-based desulfurization sorbents promoted with iron oxide (Fe2O3) were prepared to improve the regeneration properties of ZnO-TiO2 (ZT) sorbent at middle temperatures in the range of 480-580 degreesC. 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 degreesC, while the regeneration rate of ZnS was very slow in the temperature range of 480-550 degreesC. 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 degreesC, while the zinc oxide sorbents separated from the spinel structure needed a temperature higher than 600 degreesC for regeneration. The original structures of the sorbents were determined depending on the initial pretreatment conditions, and the structures after regeneration were unchanged.