X-RAY PHOTOELECTRON SPECTROSCOPIC STUDIES OF IRON-OXIDE CATALYSTS PREPARED FROM THE CALCINATION OF IRON SULFATES AT HIGH-TEMPERATURE

Surfaces of iron sulfates calcined at various temperatures ranging from 500 to 900 °C were examined by X-ray photoelectron spectroscopy and X-ray diffraction. The sulfates when calcined in air at 700 °C, showed the highest catalytic activity for the Friedel-Crafts benzylation, benzoylation, and isopropylation of toluene, and were found to have the following surface properties: (1) the iron sulfate completely decomposes to form α-Fe2O3 at temperatures from 675 to 700 °C. At higher temperatures, the crystalization proceeds rapidly, but any change in the chemical state of iron and oxygen ions on the surface due to the decomposition process can not be deteted. (2) A small amount of sulfur (0.15 wt%) remains as SO4 on the surface at temperatures greater than 700 °C after decomposition. The conclusion was confirmed by the benzylation with the differently sulfur-treated ferric oxide catalysts. © 1979.