Fischer-Tropsch synthesis on supported iron catalysts prepared from iron(III) chloride

Iron/alumina and iron/silica catalysts for the Fischer-Tropsch (FT) reaction were prepared by impregnation with aqueous iron (III) chloride solution. The effects of pretreatments on the phase changes and catalytic properties were investigated. Different pretreatment conditions have large effects on phase changes of iron/silica owing to weak interactions between the metal and the support. The strong metal-support interactions in the iron/alumina system lead to the formation of FeAlO3 and hence make the reduction to metallic Fe0 more difficult. A significant amount of residual Cl− ions existing on vacuum-dried catalysts will decrease the rate of carbon monoxide hydrogenation and shift the product distribution to long-chain hydrocarbons. This evidence indicates that the carburization ability of catalysts is enhanced by Cl− ions, which can be reflected by temperature-programmed decarburization carried out on used catalysts. The existence of residual Cl− ions is also responsible for the suppression of carbon dioxide production in the FT reaction by inhibiting the water-gas shift reaction.