Catalytic properties of materials derived from iron-containing clays

Abstract

The catalytic activities of iron-containing fireclays reduced at 1020°C, determined using the Fischer-Tropsch hydrocarbon synthesis reaction in a wax-slurry reactor, are proportional to the intensity of an unusual singlet peak in the Mossbauer spectra of the reduced samples. This singlet peak is attributed to γ-Fe, a metastable high-temperature form which appears to be stabilized by the cubic host lattice resulting from kaolinite decomposition at ca. 980°C. The enhanced activity of γ-Fe is discussed in terms of steric factors related to the structure of this phase. The effects of different thermal pretreatments and additions of alkali promotors on the catalytic activity are also discussed.