Effects of Potassium Loading over Iron–Silica Interaction, Phase Evolution and Catalytic Behavior of Precipitated Iron-Based Catalysts for Fischer-Tropsch Synthesis

Potassium (K) promoter and its loading contents were shown to have remarkable effects on the Fe–O–Si interaction of precipitated Fe/Cu/K/SiO2 catalysts for low-temperature Fischer-Tropsch synthesis (FTS). With increase in K content from 2.3% (100 g Fe based) up 7% calcined precursors, was weakened, as reflected by ATR/FTIR, H2-TPR XPS investigations. XRD results confirmed that diffraction peak intensity (510) facet ?-Fe5C2 phase strengthened with increasing loading, which indicates crystallite size increased either during syngas reduction/carburization procedure or after FTS reaction. H2-TPH indicated more reactive surface carbon (alpha-carbon) obtained over higher samples pre-carburized syngas. Raman spectra illustrated a greater proportion graphitic accumulated spent loading. At same time, ATR-FTIR, Mössbauer (MES) characterization showed relatively level bulk Fayalite (Fe2SiO4) species observed discernibly lowest sample (2.3 K%) this work. The catalytic evaluation CO conversion, CO2 selectivity O/P (C2–C4) ratio progressively whereas monotonic decline both conversion highest c.a. 280 h TOS.