Fischer supports

Feltzin, et. al. (10) indicated that the initial step in the reaction was catalyst activation by the reaction of the tertiary amine with a co-catalyst to form a quaternary salt. Fischer supports the Feltzin mechanism because he reports that quaternary salts catalyze the reaction in much the same way as tertiary amines. Tanaka and Kakiuchi (8) also favor a catalyst activation. It can be concluded that the experts essentially agree that the mechanism consists of ... 

More information has appeared concerning the nature of the side reactions, such as acetoxylation, which occur when certain methylated aromatic hydrocarbons are treated with mixtures prepared from nitric acid and acetic anhydride. Blackstock, Fischer, Richards, Vaughan and Wright have provided excellent evidence in support of a suggested ( 5.3.5) addition-elimination route towards 3,4-dimethylphenyl acetate in the reaction of o-xylene. Two intermediates were isolated, both of which gave rise to 3,4-dimethylphenyl acetate in aqueous acidic media and when subjected to vapour phase chromatography. One was positively identified, by ultraviolet, infra-red, n.m.r., and mass spectrometric studies, as the compound (l). The other was less stable and less well identified, but could be (ll). 

The mechanism of the Fischer cyclization outlined in equation 7.1 has been supported by spectroscopic observation of various intermediates[4] and by isolation of examples of intermediates in specialized structures[5]. In particular, it has been possible to isolate enehydrazines under neutral conditions and to demonstrate their conversion to indoles under the influence of acid cata-lysts[6]. 

Fischer and Neumann have discussed the ultraviolet and fluorescence spectra of 199 and 200 and consider them to support the polyoxo forms shown. 

The 13C-NMR spectra of 4-7, 9-11 show a close similarity to the spectral data of analogous carbene complexes. The shift differences between the metal carbonyls of the silylene complexes and the related carbon compounds are only small. These results underline the close analogy between the silicon compounds 4-7, 9-11 and Fischer carbene complexes. This view is also supported by the IR spectral data. On the basis of an analysis of the force constants of the vco stretching vibration,... 

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]. 

Figure4.17. Mossbauer spectra give detailed information on the state of iron in a Ti02-supported iron catalyst after different treatments. Here reduction was in H2 at 675 K for 18 h, and FTS stands for Fischer-Tropsch synthesis. [Adapted from A.M. van der Kraan, R.C.H. Nonnekens, F. Stoop and J.W. Niemantsverdriet, Appl. Catal. 27 (1986) 285.]...

The decarbonylation of oxide-supported metal carbonyls yields gaseous products including not just CO, but also CO2, H2, and hydrocarbons [20]. The chemistry evidently involves the support surface and breaking of C - O bonds and has been thought to possibly leave C on the clusters [21]. The chemistry has been compared with that occurring in Fischer-Tropsch catalysis on metal surfaces [20] support hydroxyl groups are probably involved in the chemistry. 

USDA, Beltsville, MD for a sample of chondrillasterol and Helga D. Fischer and Joel Carpenter for technical assistance. Support for this work by the USDA-ARS Cooperative Agreement No. 58-7B30-2-399 is acknowledged. 

The polymers were converted to supported catalysts corresponding to homogeneous complexes of cobalt, rhodium and titanium. The cobalt catalyst exhibited no reactivity in a Fischer-Tropsch reaction, but was effective in promoting hydroformylation, as was a rhodium analog. A polymer bound titanocene catalyst maintained as much as a 40-fold activity over homogeneous titanocene in hydrogenations. The enhanced activity indicated better site isolation even without crosslinking. 

Pirola C, Bianchi CL, Michele AD, Diodati P, Boffito D, Ragaini V (2010) Ultrasound and microwave assisted synthesis of high loading Fe-supported Fischer-Tropsch catalysts. Ultrason Sonochem 17 610-616... 

Additional utilization of the water gas shift reaction also allows ethylene or methanol to be produced in a second synthesis step, which was developed around 1925 by Fischer and Tropsch [2], The catalyst for this heterogeneous process consists of Co-Th02-MgO mixtures supported on kieselgur. 

The induction of steric effects by the pore walls was first demonstrated with heterogeneous catalysts, prepared from metal carbonyl clusters such as Rh6(CO)16, Ru3(CO)12, or Ir4(CO)12, which were synthesized in situ after a cation exchange process under CO in the large pores of zeolites such as HY, NaY, or 13X.25,26 The zeolite-entrapped carbonyl clusters are stable towards oxidation-reduction cycles this is in sharp contrast to the behavior of the same clusters supported on non-porous inorganic oxides. At high temperatures these metal carbonyl clusters aggregate to small metal particles, whose size is restricted by the dimensions of the zeolitic framework. Moreover, for a number of reactions, the size of the pores controls the size of the products formed thus a higher selectivity to the lower hydrocarbons has been reported for the Fischer Tropsch reaction. 

Bezemer G.L., Bitter J.H., Kuipers H.P.C.E., Oosterbeek H., Holewijn J.E., Xu X., Kapteijn F., van Dillon A.J., and de Jong K.P. 2006. Cobalt particle size effects in the Fischer-Tropsch reaction studied with carbon nanofibre supported catalysts. J. Am. Chem. Soc. 128 3956-64. 

Jacobs G., Ji Y., Davis B.H., Cronauer D., Kropf J., and Marshall C.L. 2007. Fischer-Tropsch synthesis Temperature programmed EXAFS/XANES investigation of the influence of support type, cobalt loading and noble metal promoter addition to the reduction behaviour of cobalt oxide particles. Appl. Catal. A Gen. 333 179-91. 

Jacobs G., Das T.K., Zhang Y., Li J., Racoillet G., Davis B.H. 2002. Fischer-Tropsch synthesis Support, loading and promoter effects on the reducibility of cobalt catalysts. Appl. Catal. A Gen. 233 263-81. 

Storsaeter S., Totdal B., Walmsley J.C., Tanem B.S., and Holmen A. 2005. Characterisation of alumina-, silica- and titania-supported cobalt Fischer-Tropsch catalysts. 7. Catal. 236 139-52. 

Morales F., de Smit E., de Groot F.M.F., Visser T., and Weckhuysen B.M. 2007. Effects of manganese oxide promoter on the CO and H2 adsorption properties of titania-supported cobalt Fischer-Tropsch catalysts. J. Catal. 246 91-99. 

Zhang Y., Hanayama K., and Tsubaki N. 2006. The surface modification effects of silica support by organic solvents for Fischer-Tropsch synthesis catalysts. Catal. Commun. 7 251-54. 

Girardon J.-S., Quinet E., Constant-Griboval A., Chemavskii P.A., Gengembre L., and Khodakov A.Y. 2007. Cobalt dispersion, reducibility and surface sites in promoted silica-supported Fischer-Tropsch catalysts. J. Catal. 248 143-57. 

Ellis PR. and Bishop P.T. 2006. Supported cobalt catalysts for the Fischer-Tropsch synthesis. International Patent Application WO2006/136863. 

Carbon Nanomaterials as Supports for Fischer-Tropsch Catalysts... 

The potential of carbon nanomaterials for the Fischer-Tropsch synthesis was investigated by employing three different nanomaterials as catalyst supports. Herringbone (HB) and platelet (PL) type nanofibers as well as multiwalled (MW) nanotubes were examined in terms of stability, activity, and selectivity for Fischer-Tropsch synthesis (FTS). 

Concerning the Fischer-Tropsch synthesis, carbon nanomaterials have already been successfully employed as catalyst support media on a laboratory scale. The main attention in literature has been paid so far to subjects such as the comparison of functionalization techniques,9-11 the influence of promoters on the catalytic performance,1 12 and the investigations of metal particle size effects7,8 as well as of metal-support interactions.14,15 However, research was focused on one nanomaterial type only in each of these studies. Yu et al.16 compared the performance of two different kinds of nanofibers (herringbones and platelets) in the Fischer-Tropsch synthesis. A direct comparison between nanotubes and nanofibers as catalyst support media has not yet been an issue of discussion in Fischer-Tropsch investigations. In addition, a comparison with commercially used FT catalysts has up to now not been published. 

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