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Highlights: [•] Two 4000bbl/d demonstration scale projects using the MTFT technology are being successfully operated in China. [•] DFT studies on adsorption and reaction mechanisms on iron phases can provide guidance to development of F–T catalysts. [•] Kinetics based on theoretical and experimental results can be very important tools for F–T reactor and process development. [ABSTRACT FROM AUTHOR]

Abstract: The structural properties and iron–silica interaction of the precipitated iron catalysts incorporated with or without silica have been investigated by powder X-ray diffraction (XRD), Mössbauer spectroscopy, and temperature-programmed reduction (TPR) with H2 consumption quantitative analysis. The Fischer–Tropsch synthesis (FTS) performances of the catalysts were carried out in a slurry-phase continuously stirred tank reactor (CSTR). It was found that, for as-prepared samples, nano-particles of iron oxide mixtures (α- and/or γ-Fe2O3) formed on the silica-incorporated catalyst, whereas well-crystallized hematite (α-Fe2O3) is the only phase on the silica-free catalyst. After reduction in H2, the observed phase in the silica-free catalyst is α-Fe, whereas wüstite (Fe x O) and iron (II) silicate (Fe2SiO4) are the main phases in the silica-incorporated catalyst. In H2-TPR, the Fe3+ ions in the silica-incorporated catalyst are reduced to Fe (0) via Fe2+ ions as intermediate and the reduction extent of iron oxides obviously decreased comparing with the silica-free catalyst. The differences in structural properties and reduction behavior between the silica-free and the silica-incorporated catalysts may be due to the high dispersion effect of silica and the iron–silica interaction. The iron–silica interaction also decreases the FTS activity and improves the light hydrocarbon selectivity. [Copyright &y& Elsevier]

Abstract: A systematic study was undertaken to investigate the effects of Al2O3/SiO2 ratio on reduction, carburization and catalytic behavior of iron-based Fischer–Tropsch synthesis (FTS) catalysts promoted with potassium and copper. The catalysts were characterized by N2 physical adsorption, CO2 temperature-programmed desorption (TPD), H2 temperature-programmed reduction (TPR) and Mössbauer effect spectroscopy (MES). CO2-TPD indicated that Al2O3 binder has stronger acidity than SiO2 binder and weakens the surface basicity of the catalysts. H2-TPR profiles suggested that the lower Al2O3/SiO2 ratio promotes the reduction of Fe2O3→Fe3O4. With further increasing Al2O3/SiO2 ratio, the transformation of Fe2O3→Fe3O4 shifts to higher temperatures. The MES results showed that the increase of Al2O3/SiO2 ratio leads to the relatively large crystallite size of α-Fe2O3 and inhibits carburization of the catalyst. During reaction tests in a fixed bed reactor it was found that a maximum in catalyst activity is noted at the Al2O3/SiO2 ratio of 5/20 (weight basis). The selectivity to olefins shows a rapid decrease and the formations of methane and light hydrocarbons are promoted with increasing Al2O3/SiO2 ratio. The oxygenate selectivity in total products increases with increasing Al2O3/SiO2 ratio. [Copyright &y& Elsevier]