Influence of Calcination Temperatures on the Desulfurization Performance of Fe Supported Activated Carbons Treated by HNO3

Fe supported on activated carbons treated by HNO3 (Fe/NAC) was prepared using the incipient wetness method with ultrasonic-assisted oscillation and calcined at different temperatures. The physical and chemical properties were studied using FTIR, XPS, XRD and H-2-TPR, and SO2 removal ability of Fe/NAC was also evaluated at a fixed bed. The results showed that alpha-Fe2O3 and small Fe3O4 coexist in Fe/NAC-500, while catalysts calcined at 700 degrees C only possess Fe3O4. Fe3O4 with small Fe2SiO4 is observed for Fe/NAC-900, but Fe2SiO4 and Fe-0 are detected in Fe/NAC-1000, indicating that the interactions between Fe precursor and activated carbons are very complex, and C atoms may take part in the reduction of iron oxides. The relative content of C-C and C-O decreases first and then increases when calcination temperatures increase from 500 to 1000 degrees C, but that of C=O and O=C-OH has a contrary trend, suggesting that calcination temperatures influence the formation of functional groups. Fe/NAC-900 shows the best activity and has a sulfur capacity of 322 mg/g, which is related closely to O=C-OH and good crystallinity of Fe3O4. Fe3O4 is the main active phase in the SO2 removal process. After desulfurization, O=C-OH, alpha-Fe2O3, Fe3O4, and Fe-0 disappear, and Fe-2(SO4)(3) is observed, leading to the decrease of SO2 removal ability.