Alkali cations and direct reduction of wustite

Abstract

THERE are few reports^1,2 on the direct reduction of wustite by carbon according to an autocatalytic mechanism, and none deal with its quantitative analysis in terms of any kinetic model. Eck³ has postulated that this mode of reduction is indicative of the increased role of processes such as diffusion and nucleation in the solid state, relative to the gasification of carbon by the Boudouard reaction—generally regarded as the rate-controlling step in the reduction⁴. We describe here a quantitative analysis of autocatalytic reduction in terms of the Prout–Tompkins⁵ mechanism for the growth of a product phase in the lattice of the unreacted phase. We derive a rate constant characterising the growth of the metallic phase and use it to evaluate the catalytic effects of small admixtures of alkali salts (ref. 6 summarises the literature on catalysed reduction).