PERFORMANCE AND CHARACTERIZATION OF SUPPORTED IRON NANOCATALYST IN FISCHER-TROPSCH REACTION

Fischer-Tropsch synthesis (FTS) has received considerable attention as it offers alternative route to produce liquid fuels and chemicals from abundant energy sources other than crude oil such as natural gas, coal, and biomass. The objective of this work is to synthesize, characterize and study the performance of supported iron (Fe) nanocatalyst with Fe particle less than 30nm in Fischer-Tropsch synthesis. Supported Fe nanoparticles have been formulated using impregnation and precipitation methods. Fe nanoparticles loading (3, 6, 10, 15 wt %) were deposited on silica (SiO2) and alumina-silica (Al2O3-SiO2) supports. The effect of alkali promoters such as potassium (K) and copper (Cu) on the physicochemical properties of the catalyst has been investigated. The physicochemical properties of the catalysts were studied using N2 physical adsorption, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and H2 temperature-programmed reduction (TPR). The FTS performance of the synthesized catalysts was examined in a fixed-bed microreactor at atmospheric pressure and various reactant ratio (H2/CO), temperature, and space velocity. The size of Fe nanoparticle was affected by the Fe loading, synthesis technique, and the type of catalyst support. More uniformly distributed and smaller particle size was obtained at lower Fe loading. The 6%Fe/SiO2 synthesized via the impregnation method had Fe average particles size of 8.6±1.1 nm, as measured by TEM. It resulted in CO conversion of 54% and C5+ selectivity of 20% at 523K, 1.5H2/CO v/v ratio, and 3L/g-cat.h. Under the same reaction conditions, 6%Fe/SiO2 prepared by precipitation method with Fe average particles size of 12.8±4.2 nm resulted in CO conversion of 45% and C5+ selectivity of 8%. The CO conversion trend correlated to the size of Fe nanoparticles where the results show that catalysts with average particles size less than 9 nm yielded in CO conversion >50% as well as higher selectivity of C5+ and olefins, and lower selectivity for light hydrocarbons (C1-C4) compared of those of larger particles.