Fischer—Tropsch synthesis modified

Successful applications of the oxygen-modified CNFs are reported on immobilization of metal complexes ]95], incorporation of small Rh particles [96], supported Pt and Ru CNFs by adsorption and homogeneous deposition precipitation ]97, 98], Co CNFs for Fischer-Tropsch synthesis ]99], and Pt CNFs for PEM fuel cells [100]. 

Xiong H., Zhang Y., Liew K., and Li J. 2005. Catalytic performance of zirconium modified Co/A1203 for Fischer-Tropsch synthesis. J. Mol. Catal. A Chem. 231 145-51. 

Mochizuki T., Hara T., Koizumi N., and Yamada M. 2007. Surface structure and Fischer-Tropsch synthesis activity of highly active Co/Si02 catalysts prepared from the impregnating solution modified with some chelating agents. Appl. Catal. A Gen. 317 97-104. 

Nurunnabi, M., Murata, K., Okabe, K., Inaba, M., and Takahara, 1.2008. Performance and characterization of Ru/A1203 and Ru/Si02 catalysts modified with Mn for Fischer-Tropsch synthesis. Appl. Catal. A Gen. 340 203-11. 

In commercial Fischer-Tropsch synthesis, catalyst performance is modified by support and promoter interaction22 to control segregation and stabilize dispersion. 

Change in Fischer-Tropsch synthesis. In the 1990s the Kellogg Fe-HTFT synthesis section was decommissioned and additional Fe-LTFT synthesis capacity was added with the introduction of a slurry bed reactor.35 This modified the syncrude feed to the refinery to Fe-LTFT only. This was accompanied by a significant change in the product slate being produced. 

A new mechanism to interpret alkene formation in Fischer-Tropsch synthesis has been presented 499-501 There is a general agreement that hydrocarbon formation proceeds according to the modified carbene mechanism. Specifically, CO decomposes to form surface carbide and then undergoes hydrogenation to form surface methine (=CH), methylene (=CH2), methyl and, finally, methane. Linear hydrocarbons are formed in a stepwise polymerization of methylene species. When chain growth is terminated by p-hydride elimination [Eq. (3.61)], 1-alkenes may be formed,502 which is also called the alkyl mechanism ... 

The synthesis of hydrocarbons from and CO is strongly exothermic. The Hydrocol process mentioned in Section I is a modified Fischer-Tropsch synthesis, using powdered iron catalyst in a dense-phase fluidized bed. In spite of elaborate scale-up based on intensive research, many problems arose in commercial plants, and the operation was terminated in 1957 for economic reasons (Z5). 

Examples of supports modifying the properties of transition metal oxides have also appeared in the literature. Recent work points to iron oxide phases as important species in Fischer-Tropsch synthesis (3 ). Iron oxide supported on SiO2 (4 ) and TiO ( ) resist reduction under conditions in which bulk iron oxide easily reduces. Thus supported iron oxide catalysts are potentially interesting Fischer-Tropsch catalysts. The extensive studies on ethylene polymerization catalysts suggests that chromium (VI) species exist on a SiOp surface at temperatures above which bulk chromic anhydride (CrOg) decomposes ( ). 

Support modification has been reported earlier in the open literature [5,6,7,8,9]. Zirconia modification of silica supports was used to prevent the formation of unreducible cobalt-silicates [5]. Zr, Ce, Hf, or U modification of titania supports was reported to prevent the formation of cobalt-titanates during regeneration [6]. To increase the porosity of titania supports, they were modified with small amounts of binders, e.g. silica, alumina or zirconia [7]. Lanthanum oxide promotion of alumina was reported to be beneficial for improved production of products with higher boiling points [8], and zirconia modification of alumina supports was carried out to decrease the interaction of cobalt with alumina [9]. All these modified supports were either used for fixed bed cobalt based Fischer-Tropsch synthesis catalysts or they were used for slurry phase cobalt catalysts, but not tested under realistic Fischer-Tropsch synthesis conditions in large scale slurry bed reactors. 

The support geometry is important with respect to Fischer-Tropsch synthesis performance (i.e. activity and selectivity) of the resultant catalyst based thereon. The modified alumina support after silica modification did indeed produce a catalyst with the desired Fischer-Tropsch synthesis characteristics [4]. 

From Table 1, it can be concluded that silicon modification of alumina did not have any substantial effect on the Fischer-Tropsch synthesis activity nor did it substantially influence the selectivity of the silica modified catalyst B. 

The silica modified supported cobalt catalyst. Catalyst B, were tested in a Pilot Plant slurry bubble column reactor under realistic Fischer-Tropsch synthesis conditions and it... 

It was demonstrated that the production of clean waxy products (i.e. free of any cobalt contamination) during large scale slurry phase Fischer-Tropsch synthesis runs, was successfully effected with cobalt catalysts that were prepared on modified supports (i.e. supports displaying inhibited dissolution behaviour in aqueous environments). As an example, the silicon modification of alumina supports was discussed in detail. 

Iron-ruthenium bimetallic catalysts have also received considerable attention as interesting catalysts in Fischer-Tropsch synthesis [115,116]. It has been reported that the Fe-Ru alloy system results in catalysts that are more stable than monometallic iron catalysts [117], and that the hydrocarbon product distribution in CO hydrogenation can easily be modified when changing the relative proportions of the two metals [118]. 

Direct oxidation of methane (natural gas) with tonnage oxygen of about 95 per cent purity is assuming increasing importance in connection with the production of hydrogen-carbon monoxide synthesis gas, raw material for the American modified Fischer-Tropsch synthesis of liquid fuels and chemicals. ... 

Cobalt-containing alumina supported catalysts modified by a second metal have been parallel tested in the Fischer-Tropsch synthesis under pilot conditions. It has been observed that promotion of alumina supported Cocontaining catalysts by certain amounts of Pt leads to an increase in the formation of high molecular-weight hard hydrocarbons, so-called ceresins (77%). Also, it has been found that ceresin formation is strongly dependent on process conditions (pressure, temperature and space velocity). By parallel testing, the catalyst composition and process conditions for the selective production of ceresins from synthesis-gas have been determined and optimised. The physico-chemical properties have been studied by X-Ray, TEM, IR-spectroscopic, TPR and other methods. The synthesised catalysts are highly effective and stable. 

In terms of hydrogenation, the Sabatier-Senderens reduction has been extensively modified, as shown by the Fischer-Tropsch Synthesis (or process), the Adkins Catalyst, and Raney-Nickel Catalyst. In addition, the silica black-supported nickel catalyst, and nickel-based complex reducing agents (Nic, e.g. NaH-RONa-Ni(OAc)2), have also been developed, the latter is a heterogeneous hydrogenation catalyst that works at atmospheric pressure. 

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