Effect of additives on the reduction behaviour and CO 2 catalytic decomposition of nanocrystallite Fe 2 O 3

Abstract

Compacts of pure Fe₂O₃ mixed with 5 wt-%MgO, CuO, SiO₂ or TiO₂ separately, were sintered at 500°C for 1 h and then isothermally reduced with H₂ at 500°C to metallic iron. The oxygen weight loss resulting from Fe₂O₃–Fe reduction steps were continuously recorded as a function of time. X-ray analyses, reflected light microscope and scanning electron microscope were used to characterise the fired and reduced compacts. The influence of MgO, CuO, SiO₂ and TiO₂ on the reduction and CO₂ catalytic decomposition behaviour of Fe₂O₃ was intensively studied. The reduction was correlated to the microstructure of the reduced samples. The results obtained showed that doping of Fe₂O₃ with these fluxing oxides decreases the reduction of Fe₂O₃ at 500°C. This was attributed to formation of entrapped lower oxide relics, which hindered gaseous diffusion. On the other hand, for the CO₂ catalytic decomposition process, it was found that the rate of reoxidation of samples reduced from pure Fe₂O₃ is higher than those samples obtained from Fe₂O₃ doped with CuO, MgO, TiO₂ and SiO₂ at the initial stage, whereas at the final stages, the rate of reoxidation of reduced pure Fe₂O₃ is less than that for reduced Fe₂O₃ doped with CuO, MgO, TiO₂ and SiO₂.