Attrition properties of precipitated iron Fischer–Tropsch catalysts
ABSTRACT While precipitated iron catalysts provide optimal activity and selectivity for Fischer–Tropsch (F–T) synthesis with coal-derived synthesis gas, their attrition resistance under reaction conditions has been questioned. It is well known that iron oxides undergo phase transformations during activation and reaction, leading to changes in volume, which are a primary cause of catalyst break up (‘chemical attrition’). In this paper we report on attrition properties of precipitated Fe catalysts under both inert and reactive conditions in a stirred tank slurry reactor (STSR). Our results show that after 364 h of testing in the STSR, the particle size reduction due to fracture and erosion was moderate. The observed increase in fraction of particles smaller than 10 μm was small (7.8%). Catalytic performance was excellent, yielding low methane and high C5+ selectivities of 2.6 and 82.5%, respectively, at 78.5% single pass conversion. We conclude therefore that iron catalysts used in this study have adequate attrition resistance and desirable F–T activity and selectivity for use in conversion of coal-derived syngas to liquid fuels in the slurry bubble column reactor.
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ABSTRACT: Iron-based catalyst is the most common catalyst for Fischer-Tropsch Synthesis (FTS), which is a process to synthesize transportation fuel and chemicals feedstock from the syngas. The effect of synthesis technique, iron loading and catalyst supports on the physicochemical properties of iron-based catalyst was investigated. Impregnation and precipitation methods were used to synthesize the supported iron-based nanocatalysts containing various iron loadings. Silica and alumina silica were used as catalyst supports to modify the catalyst properties in producing well defined phases. The supported iron nanocatalysts were characterized using N<SUB>2</SUB> physical adsorption, Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM) and Temperature-Programmed Reduction (TPR). For the catalysts prepared via impregnation method, the surface area remained at 23 m<SUP>2</SUP> g<SUP>-1</SUP> for catalyst containing different iron loading. However, for those prepared via the precipitation method, the surface area of the catalyst increased with increasing iron loading. Precipitation method resulted in highly agglomerated iron nanoparticles. The 6% Fe SiO<SUB>2</SUB> nanocatalyst prepared via impregnation method resulted in relatively small and uniform dispersion of iron nanoparticles. However, bimodal distribution was observed for the 10 and 15% Fe SiO<SUB>2</SUB>. Similar trend was observed when Al<SUB>2</SUB>O<SUB>3</SUB>-SiO<SUB>2</SUB> was used as a catalyst support. H<SUB>2</SUB>-TPR profiles for Fe SiO<SUB>2</SUB> nanocatalysts synthesized via impregnation showed two reduction stages while those prepared using precipitation method resulted in three reduction peaks. The TPR peak positions remained the same for various iron loadings.Journal of Applied Sciences. 01/2011;