REDUCTION OXIDATION OF A HIGH LOADING IRON-OXIDE CATALYST

The reduction/oxidation of a high loading iron catalyst supported on γ-Al203 has been studied using dynamic X-ray diffraction (DXRD). In situ determination of changes in the lattice parameters as magnetite was reduced to iron indicated that aluminum was unevenly incorporated into the matrix of the supported iron oxide particles, leading to a form of metal-support interaction and manifested by reduction rates which are much slower than for unsupported magnetite. These results are corroborated in subsequent oxidation experiments by the fact that CO, oxidation rates of supported iron are much higher than for unsupported iron and the Fe203 phase formed in the former at 673 K is γ-Fe203 as opposed to α-Fe203 in the latter. The rate data are modeled and the results are shown to be consistent with the conclusion of nonuniform Al incorporation as well as with previous work on the oxidation of unsupported iron. The incorporation of AI in this Fe/Al203 catalyst is consistent with previous observations related to the form of metal-support interactions in Ni/Al2O3 and in Fe/SiO2. © 1991.