Effects of manganese oxide and sulphate on olefin selectivity of iron supported catalysts in the Fischer-Tropsch reaction

Abstract In agreement with previous studies, the addition of manganese compounds to iron or cobalt catalysts yields reproducible changes of catalytic properties. When iron catalysts were prepared from salt precursors, we generally observed a decrease of activity and an increase in light olefins selectivity, a maximum value being obtained for a Co (Fe)/Mn ≅ 1.0 bulk composition. Moreover, when there are small quantities of sulphate salt in iron or iron-manganese supported catalysts, we observed significant changes in catalytic properties, especially when activation temperature or reaction conditions favoured H 2 S formation. In the latter case, the promoter effect of the manganese compound on olefin selectivity was less pronounced, or even entirely nullified.