Volumetric and infrared studies of carbon monoxide adsorption on silica-supported iron catalysts characterised by thermogravimetric analysis and X-ray diffraction

Abstract

The reduction of iron(III) nitrate dispersed on silica has been investigated as a function of reduction temperature by t.g.a., X.r.d, total CO uptakes and infrared spectra of adsorbed CO. There was no evidence for iron–silica interactions. Increased extent of reduction favoured enhanced dissociative and associative adsorption of CO but raising the reduction temperature above ca. 650 K favoured subsequent dissociative adsorption of CO at the expense of adsorbed CO detectable by infrared spectroscopy. Well reduced iron particles were susceptible to rapid contamination by traces of oxygen and complete poisoning (for CO adsorption) by excess oxygen. Enhanced uptake of CO by K₂O-promoted Fe–SiO₂ exhibited a maximum at 0.5% K₂O loading. Addition of Al₂O₃ also promoted CO adsorption but the effects of K₂O and Al₂O₃ in doubly promoted catalyst were not additive.