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.
"Cobalt-based catalysts are widely investigated for the syngas which derivative from natural gas with high H 2 /CO ratio. Meanwhile, iron-based catalyst is attractive due to their high FTS activity for the low H 2 /CO ratio as well as their water–gas shift reactivity , and also due to their low cost . In order to improve the performance of the catalyst many attempts have focused on the addition of chemicals such as promoters, supports, and many other additives. "
[Show abstract][Hide abstract] 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 07/2011; 11(7). DOI:10.3923/jas.2011.1150.1156
"The former results in the formation of silica layer on the surface of magnetic particles via hydrolysis of TEOS, while the latter controls the size of the silica shell based on concentration of surfactants in the reactor. Generally, core/shell type M@SiO 2 or M@M x O y magnetic nanoparticles can be obtained by a forced reduction of M x O y or M-organo-ligands to M. Examples include the synthesis of Fe or Fe-alloy@SiO 2    , Co@SiO 2 , Fe@SnO 2 , and M@Fe 3 O 4    using a 10-h reduction in a mixed gas containing H 2 at high temperatures. In this reduction method, the use of high purity H 2 gas may cause a serious safety problem. "
[Show abstract][Hide abstract] ABSTRACT: Core/shell type nanoparticles with an average diameter of 11 nm were synthesized by coating Fe3O4 core in an alkyl alcohol (octanol) with amorphous silica shell. The synthesized nanoparticles were calcined under various conditions to produce different types of core/shell particles. The particles were characterized by using various experimental techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectrometry (EDS), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and vibration sample magnetometer (VSM). The results suggest that the composition of the three samples (uncalcined, calcined at 200–600 °C for 5 h and 15 h) are Ox-Fe3O4@SiO2, Fe3O4/Fe@SiO2 and γ-Fe2O3/Fe@SiO2, respectively. The saturation magnetization of the particles calcined for 5 h was found to be higher than those of the other particles. It is noted that the formation of metal iron inside the particles during calcination is responsible for the enhanced magnetic property.
Colloids and Surfaces A Physicochemical and Engineering Aspects 02/2007; 293(1-293):278-285. DOI:10.1016/j.colsurfa.2006.07.044 · 2.75 Impact Factor
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