Advances in the development of novel cobalt Fischer-Tropsch catalysts for synthesis of long-chain hydrocarbons and clean fuels.

The influence of cobalt particle size in the range of 2.6-27 nm on the performance in Fischer-Tropsch synthesis has been investigated for the first time using well-defined catalysts based on an inert carbon nanofibers support material. X-ray absorption spectroscopy revealed that cobalt was metallic, even for small particle sizes, after the in situ reduction treatment, which is a prerequisite for catalytic operation and is difficult to achieve using traditional oxidic supports. The turnover frequency (TOF) for CO hydrogenation was independent of cobalt particle size for catalysts with sizes larger than 6 nm (1 bar) or 8 nm (35 bar), while both the selectivity and the activity changed for catalysts with smaller particles. At 35 bar, the TOF decreased from 23 x 10(-3) to 1.4 x 10(-3) s(-1), while the C5+ selectivity decreased from 85 to 51 wt % when the cobalt particle size was reduced from 16 to 2.6 nm. This demonstrates that the minimal required cobalt particle size for Fischer-Tropsch catalysis is larger (6-8 nm) than can be explained by classical structure sensitivity. Other explanations raised in the literature, such as formation of CoO or Co carbide species on small particles during catalytic testing, were not substantiated by experimental evidence from X-ray absorption spectroscopy. Interestingly, we found with EXAFS a decrease of the cobalt coordination number under reaction conditions, which points to reconstruction of the cobalt particles. It is argued that the cobalt particle size effects can be attributed to nonclassical structure sensitivity in combination with CO-induced surface reconstruction. The profound influences of particle size may be important for the design of new Fischer-Tropsch catalysts.

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Cobalt particle size effects in the fischer- : Tropsch reaction studied with carbon nanofiber supported catalysts

Recent advances in the science and technology of ultra low sulfur diesel (ULSD) production

Lower olefins are key building blocks for the manufacture of plastics, cosmetics, and drugs. Traditionally, olefins with two to four carbons are produced by steam cracking of crude oil-derived naphtha, but there is a pressing need for alternative feedstocks and processes in view of supply limitations and of environmental issues. Although the Fischer-Tropsch synthesis has long offered a means to convert coal, biomass, and natural gas into hydrocarbon derivatives through the intermediacy of synthesis gas (a mixture of molecular hydrogen and carbon monoxide), selectivity toward lower olefins tends to be low. We report on the conversion of synthesis gas to C(2) through C(4) olefins with selectivity up to 60 weight percent, using catalysts that constitute iron nanoparticles (promoted by sulfur plus sodium) homogeneously dispersed on weakly interactive α-alumina or carbon nanofiber supports.

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Supported Iron Nanoparticles as Catalysts for Sustainable Production of Lower Olefins

http://pubs.acs.org/doi/pdfplus/10.1021/cr500486u

Recent Developments in the Synthesis of Supported Catalysts

https://dspace.library.uu.nl/bitstream/handle/1874/14690/J.Catal.-v.Dillen-2003.pdf?sequence=1

Synthesis of supported catalysts by impregnation and drying using aqueous chelated metal complexes

Selective oxidation of hydrogen sulfide to elemental sulfur using iron oxide catalysts on various supports

Work is reviewed on the synthesis of supported metal and metal oxide catalysts using impregnation of an aqueous solution of chelated metal ions followed by drying. The nature of the aqueous solutions of chelated complexes is discussed first. Upon solvent evaporation a steep increase in viscosity is apparent, which inhibits redistribution of impregnated solution upon drying of the support bodies. Furthermore, a gel-like phase is formed that favors high dispersions of the active phase after full drying. Second, several examples are dealt with in some detail, in particular supported iron, nickel, and cobalt–molybdenum catalysts. Finally an overview is presented for metal and metal oxide precursors that can be suitably deposited upon support materials using chelated aqueous metal complex solutions.

/pdf/synthesis-of-supported-catalysts-by-impregnation-and-drying-2h7bicuw0u.pdf

Synthesis of Supported Catalysts by Impregnation and Drying Using Aqueous Chelated Metal Complexes

The kinetics of the selective oxidation of hydrogen sulfide to elemental sulfur have been studied. The Catalyst used consists of highly dispersed iron sulfate supported on silica. This catalyst shows both a high conversion of hydrogen sulfide and a high selectivity to sulfur. The kinetics indicate that the rate of the reoxidation of the catalyst mainly determines the activity of the catalyst for the selective oxidation of hydrogen sulfide. The resulting low surface coverage of active oxygen leads to a high selectivity to sulfur, because the low coverage strongly impedes the deep oxidation to sulfur dioxide. A high coverage of hydrogenated sulfur species is also necessary for obtaining high selectivities.

Selective Oxidation Of Hydrogen Sulfide To Elemental Sulfur On Supported Iron Sulfate Catalysts

In the SUPERCLAUS process H 2 S is converted to sulfur by selective catalytic oxidation with O 2 . It is shown that in the part of the silica supported iron oxide catalyst bed where no H 2 S is present, sulfur can be oxidized to sulfur dioxide, causing a sharp decrease in selectivity. This oxidation is shown to proceed already on the pure silica surface, which shows that no redox couple of the catalyst is needed to oxidize the sulfur to SO 2 . Addition of sodium to the silica support, turns out to be a possibility to inhibit this reaction, thus resulting in a catalyst exhibiting high selectivities over a much wider range of temperatures.

Robert Johan Andreas Maria Terörde

Papers

Synthesis of supported catalysts by impregnation and drying using aqueous chelated metal complexes

Selective oxidation of hydrogen sulfide to elemental sulfur using iron oxide catalysts on various supports

Synthesis of Supported Catalysts by Impregnation and Drying Using Aqueous Chelated Metal Complexes

Selective Oxidation Of Hydrogen Sulfide To Elemental Sulfur On Supported Iron Sulfate Catalysts

Selective Oxidation of Hydrogen Sulfdde on A Sodium Promoted Dion Oxide on Silica Catalyst