Reduction of iron-bearing lunar minerals for the production of oxygen

Abstract

The kinetics and mechanism of the reduction of simulants of the iron-bearing lunar minerals olivine ((Fe,Mg)₂SiO₄), pyroxene ((Fe,Mg,Ca)SiO₃), and ilmenite (FeTiO₃) are investigated, extending previous work with ilmenite. Fayalite is reduced by H₂ at 1070 K to 1480 K. A layer of mixed silica glass and iron forms around an unreacted core. Reaction kinetics are influenced by permeation of hydrogen through this layer and a reaction step involving dissociated hydrogen. Reaction mechanisms are independent of Mg content. Augite, hypersthene and hedenbergite are reduced in H₂ at the same temperatures. The products are iron metal and lower iron silicates mixed throughout the mineral. Activation energy rises with calcium content. Ilmenite and fayalite are reduced with carbon deposited on partially reduced minerals via the CO disproportionation reaction. Reduction with carbon is rapid, showing the carbothermal reduction of lunar minerals is possible.