Silicon carbide foam composite containing cobalt as a highly selective and re-usable Fischer–Tropsch synthesis catalyst (original) (raw)
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Journal of Catalysis, 1988
A new method for preparation of high-specific-surface (60-400 mZ/g) Sic is described. This method consists of the attack of high-specific-surface activated carbon by SiO vapor generated by the high-temperature reaction of Si and SiOZ. The high specific surface is probably due both to the low temperature of the reaction between SiO and C and to the presence of a stable carbon skeleton. Before reaction, the carbon can be doped with different additives to improve the surface interaction between SIC and the impregnated active phase. The action of uranium doping is also shown. SEM, XRD, thermogravimetry, TPR, XPS, BET, and porosimetry have been used to characterize the supports and the catalysts. Test reactions (hydrodesulfurization by CoMo) are also reported.
Performing the best composition of supported Co/SiC catalyst for selective FTS diesel production
Fuel, 2012
For the first time, the design of an efficient Ca-promoted cobalt/SiC catalyst for selective FTS diesel production was studied. Optimization of a mCo-nCa/b-SiC catalyst composition for producing selective synthetic diesel via Fischer-Tropsch synthesis (FTS) was carried out for the first time by both Response Surface Methodology (RSM) based on characterization and parallel bench scale FTS experimentation. Based on statistical methodologies, basicity and cobalt particle size were found to be strongly and linearly influenced by the addition of calcium and cobalt loading, respectively. Degree of reduction resulted in a non-linear dependence on the amount of cobalt supported presenting a maximum value for the catalyst containing 14.0 wt.% Co in absence of promoter. Catalytic performance demonstrated that lower cobalt contents in presence of promoter shifted C þ 5 hydrocarbon product distribution toward a more selective diesel formulation. Hence, pondering those variables that afford a compromise between CO conversion and C þ 5 selectivity, a composition of 12.5 wt.% Co with 2.0 wt.% Ca was demonstrated to be the optimum for a selective diesel production.
Synthesis of high‐surface area mesoporous SiC with hierarchical porosity for use as catalyst support
Journal of the American Ceramic Society, 2020
Porous SiC with a hierarchical mesoporous structure is a promising material for high‐performance catalytic systems because of its high thermal conductivity, high chemical inertness at high temperature, and oxidation resistance. Attempts to produce high‐surface area hierarchical SiC have typically been made by using porous carbon as a template and reacting it with either Si or SiO2 at high temperature under inert atmosphere. Because the reaction mechanism with Si involves a carbon dissolution step, and the reaction with SiO2 is highly dependent on C‐SiO2 dispersion, the porous structure of the carbon template is not maintained, and the reaction yields nonporous SiC. In this work, mesoporous SiC has been synthesized using a novel hard‐template methodology. SiC was prepared from hierarchical (mesoporous) silica which served as a solid template. Carbon deposition was done by Carbon Vapor Deposition (CVD) using CH4 as carbon precursor, where different temperatures and reaction times were...
Titania-Decorated Silicon Carbide-Containing Cobalt Catalyst for Fischer–Tropsch Synthesis
ACS Catalysis, 2013
The metal−support interactions of titanium dioxide decorated silicon carbide (β-SiC)-supported cobalt catalyst for Fischer−Tropsch synthesis (FTS) were explored by a combination of energy-filtered transmission electron microscopy (EFTEM), 59 Co zero-field nuclear magnetic resonance ( 59 Co NMR), and other conventional characterization techniques. From the 2D elemental maps deduced by 2D EFTEM and 59 Co NMR analyses, it can be concluded that the nanoscale introduction of the TiO 2 into the β-SiC matrix significantly enhances the formation of small and mediumsized cobalt particles. The results revealed that the proper metal−support interaction between cobalt nanoparticles and TiO 2 led to the formation of smaller cobalt particles (<15 nm), which possess a large fraction of surface atoms and, thus, significantly contribute to the great enhancement of conversion and the reaction rate. The cobalt time yield of the catalyst after modification increased to 7.5 × 10 −5 mol CO g Co −1 s −1 at 230°C, whereas the C 5+ selectivity maintained a high level (>90%). In addition, the adequate meso-and macro-pores of the SiC-based support facilitated intimate contact between the reactants and active sites and also accelerated the evacuation of the intermediate products. It was also worth noting that a superior and stable FTS specific rate of 0.56 g C 5+ g catalyst −1 h −1 together with high C 5+ selectivity of 91% were obtained at common industrial content of 30 wt % cobalt.
Co–Ru/SiC impregnated with ethanol as an effective catalyst for the Fischer–Tropsch synthesis
Applied Catalysis A: General, 2012
Silicon carbide containing cobalt (30 wt.%) doped with 0.1 wt.% of ruthenium catalysts prepared by incipient wetness impregnation of cobalt nitrate with either ethanol or water were tested in the Fischer-Tropsch synthesis (FTS) in a fixed-bed configuration. The catalyst prepared with ethanol exhibits a higher FTS performance compared to the one prepared with water and especially at high reaction temperature, i.e. 230 • C. The FTS performance of the cobalt-based catalyst impregnated with ethanol further increases, under high temperature and high space velocity, to reach a steady state reaction rate of 0.54 g CH 2 g catalyst −1 h −1 , and a relatively high C 5+ selectivity of about 90%. In addition, the catalyst also exhibits a relatively high stability as a function of time on stream. 59 Co zero field NMR analysis has indicates that the proportion of cobalt atoms engaged in the small hcp cobalt particles (<8 nm) was higher for the ethanol impregnated catalyst and also to the more homogeneous dispersion of the ruthenium atoms within the cobalt network forming an alloy.
Ru/Al2O3 on Polymer-Derived SiC Foams as Structured Catalysts for CO2 Methanation
Catalysts
The catalytic methanation of CO2 via the strongly exothermic equilibrium Sabatier reaction requires the development of structured catalysts with enhanced mass- and heat-transfer features to limit hot-spot formation, avoid catalyst deactivation, and control process selectivity. In this work, we investigated the use of polymer-derived SiC open-cell foams as structured carriers onto which γ-Al2O3 was applied by either dip-coating or pore-filling methods; eventually, Ru was dispersed by impregnation. The formation of an undesired insulating SiO2 layer on the surface of the SiC struts was prevented by a pyrolysis treatment under an inert atmosphere at temperatures varying from 800 up to 1800 °C. SiC foam substrates and their corresponding structured catalysts were characterized by SEM, XRD, N2 physisorption, and compressive strength measurements, and their CO2 methanation activity was tested at atmospheric pressure in a fixed bed flow reactor operated in the temperature range from 200 to...