CHARACTERIZATION OF COPPER OXIDES, IRON-OXIDES, AND ZINC COPPER FERRITE DESULFURIZATION SORBENTS BY X-RAY PHOTOELECTRON-SPECTROSCOPY AND SCANNING ELECTRON-MICROSCOPY

Characterization of copper oxides, iron oxides, and zinc copper ferrite desulfurization sorbents was performed by X-ray photoelectron spectroscopy and scanning electron microscopy/energy-dispersive spectroscopy at temperatures of 298 to 823 K. Analysis of copper oxides indicated that the satellite structure of the Cu2p region was absent in the Cu(I) state but was present in the Cu(II) state. Reduction of CuO at room temperature was observed when the ion gauge was placed close to the sample. The satellite structure was absent in all the copper oxides at 823 K in vacuum. Differentiation of the oxidation state of copper utilizing both Cu(L3M4,5M4,5) X-ray-induced Auger lines and Cu2p satellite structure, indicated that the copper in zinc copper ferrite was in the +1 oxidation state at 823 K. This + 1 state of copper was not significantly changed after exposure to H-2, CO, and H2O. There was an increase in Cu/Zn ratio and a decrease in Fe/Zn ratio on the surface of zinc copper ferrite at 823 K compared to that at room temperature. These conditions of copper offered the best sulfidation equilibrium for the zinc copper ferrite desulfurization sorbent. Analysis of iron oxides indicated that there was some reduction of both Fe2O3 and FeO at 823 K. The iron in zinc copper ferrite was similar to that of Fe2O3 at room temperature but there was some reduction of this Fe(III) state to Fe(II) at 823 K. This reduction was more enhanced in the presence of H2 and CO. Reduction to Fe(II) may not be desirable for the lifetime of the sorbent.