Cobalt on kieselguhr

For more selective hydrogenations, supported 5—10 wt % palladium on activated carbon is preferred for reductions in which ring hydrogenation is not wanted. Mild conditions, a neutral solvent, and a stoichiometric amount of hydrogen are used to avoid ring hydrogenation. There are also appHcations for 35—40 wt % cobalt on kieselguhr, copper chromite (nonpromoted or promoted with barium), 5—10 wt % platinum on activated carbon, platinum (IV) oxide (Adams catalyst), and rhenium heptasulfide. Alcohol yields can sometimes be increased by the use of nonpolar (nonacidic) solvents and small amounts of bases, such as tertiary amines, which act as catalyst inhibitors. 

Supported palladium, zirconium-promoted cobalt on kieselguhr, or nickel on kieselguhr can be used under relatively mild conditions to effect reduction of the nitrile function without hydrogenating the ring. 

Since cobalt on kieselguhr in one of the original Fischer-Tropsch catalysts (1-9), it appeared attractive to investigate the catalytic activity of cobalt complexes immobilized on polystyrene. Although there are many supported cobalt-based Fischer-Tropsch catalysts known (see, for example, references 18-21), no polystyrene-bound systems had been reported. During the course of our work 18% (22,60,61) and 20% (23) crosslinked analogs of CpCo(C0)2 were shown to exhibit limited catalytic activity but no CO reduction. A preliminary disclosure of our work has appeared (2)4). 

Figure 3. A Fischer-Tropsch catalyst containing 39 wt% cobalt on kieselguhr was heated at 210 °C at normal pressure with H2/CH2N2 (left) and H2/CO (right). The C4-fraction was separated according to the isomers (see text). The data are reported in [19 a] relating to the study of R, Pettit and co-workers.

Ethanedithiol has been prepared from ethylene dichloride or ethylene dibromide and alcoholic potassium hydrosulfide from ethylene dibromide and alcoholic sodium hydrosulfide from ethylene dichloride or ethylene dibromide and alcoholic sodium hydrosulfide under pressure from ethylene dibromide and thiourea and by the catalytic hydrogenation with cobalt trisulfide or nickel-on-kieselguhr of the mixture resulting from the reaction of ethylene and sulfur. The present method is a modification of one described by Mathias. ... 

Fischer-Tropsch A process for converting synthesis gas (a mixture of carbon monoxide and hydrogen) to liquid fuels. Modified versions were known as the Synol and Synthol processes. The process is operated under pressure at 200 to 350°C, over a catalyst. Several different catalyst systems have been used at different periods, notably iron-zinc oxide, nickel-thoria on kieselguhr, cobalt-thoria on kieselguhr, and cemented iron oxide. The main products are C5 to Cn aliphatic hydrocarbons the aromatics content can be varied by varying the process conditions. 

Additional data on the effect of varying space velocity in the range of 0.24 to 2.16 1. 2Hj+lCO/g. cobalt, operating at 10-atmospheres pressure and using a cobalt-thoria-kieselguhr catalyst, are given by Fischer and... 

The role of M0O3 as a promoter has been explained as a moderator for benzene oxidation. Bhattacharya and Venkataraman studied a variety of vanadium oxide-based catalysts. They concluded that, under their conditions, the best yields of MA were obtained using the composition V2O5 (1-2.3) Mo03 (1.0), supported on kieselguhr, with 5% cobalt oxide as a promoter. 

Hydrogenation. Hydrogenation is one of the oldest and most widely used appHcations for supported catalysts, and much has been written in this field (55—57). Metals useflil in hydrogenation include cobalt, copper, nickel, palladium, platinum, rhenium, rhodium, mthenium, and silver, and there are numerous catalysts available for various specific appHcations. Most hydrogenation catalysts rely on extremely fine dispersions of the active metal on activated carbon, alumina, siHca-alumina, 2eoHtes, kieselguhr, or inert salts, such as barium sulfate. 

FIGURE 9.18 Influence of pressure on reaction rate, olefin content in the C3 fraction, and methane selectivity with cobalt as the catalyst for FT synthesis. Catalyst 100Co-18Th02-100 Si02 (Kieselguhr), H2/CO = 1.8, 175°C. 

Historical Development and Future Perspectives The Fischer-Tropsch process dates back to the early 1920s when Franz Fischer and Hans Tropsch demonstrated the conversion of synthesis gas into a mixture of higher hydrocarbons, with cobalt and iron as a catalyst [35, 36], Some 20 years earlier, Sabatier had already discovered the reaction from synthesis gas to methane catalyzed by nickel [37]. The FTS played an important role in the Second World War, as it supplied Germany and Japan with synthetic fuel. The plants used mainly cobalt catalysts supported on a silica support called kieselguhr and promoted by magnesia and thoria. 

The first promising catalyst was introduced by 1931 and contained a high proportion of nickel oxide supported on a mixture of thoria and kieselguhr. The convention widely used at the time was to describe composition as 100 parts nickel, 18 parts thoria, 100 parts kieselguhr. Catalysts made with cobalt rather than nickel were more effective but could not be considered eommercially at that time because cobalt was not available in suffieiently large quantities. The same problem had, of course, faced Haber and Boseh in the replaeement of osmium by iron oxide for the ammonia synthesis eatalyst. 

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