Iron foam catalysts for forming olefins via Fischer–Tropsch synthesis

Abstract

Despite major advances in the direct formation of light olefins (C₂–C₄) by Fischer–Tropsch synthesis (FTS), understanding the actions of promoters and iron carbides remains a difficult endeavor, since the observed results are impacted by an extensive range of complexity and unpredictabilities. In this study, macroporous iron foam (Fe foam) was used as a precursor for the FTS catalyst. The purpose was to reduce the effects of diffusion rate and heat transfer as well as to minimize the influence of promoters on the coverage of active sites. The iron foam was further promoted with sodium (Na), cesium (Cs), rubidium (Rb), and potassium permanganate (KMnO₄) to annotate the role of iron carbides in the production of light olefins during FTS. Based on the results of various characterization, such as XRD, XPS, H₂-TPR, SEM, Mössbauer spectroscopy and HR-TEM, it was found that the KMn/Fe foam catalyst with the maximum content of the active carbide phase (θ-Fe₃C) resulted in the highest light olefin and all olefin selectivity (48.0% and 78.4%) and O/P ratio (14.4 for light olefins) among all catalysts in the current study.