Hydrogen activating cobalt

Since this reaction is reversible (20, 24), hydrogenation systems which have become poisoned (hydrogen-active cobaltous species entirely converted to inactive cobaltic species) may be reactivated autocata-lytically in the presence of molecular hydrogen (20, 22). 

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. 

Systematic assessment of alumina-supported cobalt-molybdenum nitride catalyst Relationship between nitriding conditions, innate properties and CO hydrogenation activity... 

Olefins react secondarily for isomerization and hydrogenation (on cobalt sites that are not active for chain growth lower scheme in Figure 9.15). There is a first reversible H-addition (at the alpha- or beta-C-atom of the double bond) to form an alkyl species, and a slow irreversible second H-addition to form the paraffin (lower scheme in Figure 9.15). Thus, double-bond shift and double-bond hydrogenation are interrelated by a common intermediate to produce olefins with internal double bonds or paraffins from the primary FT alpha-olefins. Experimental results1018 are presented in Figures 9.16 and 9.17. 

Reuel, R.C., and Bartholomew, C.H. 1984. Effects of support and dispersion on the carbon monoxide hydrogenation activity/selectivity properties of cobalt. J. Catal. 85 78-88. 

Wang, W.J., and Chen, Y.W. 1991. Influence of metal loading on the reducibility and hydrogenation activity of cobalt/alumina catalysts. Appl. Catal. A Gen. 77 223-33. 

C03O4, various Co species, and CoA O. The C00O/. particles were more readily reduced to metallic cobalt in H2 than the Co species were. After H2 reduction at 480°C, the CO hydrogenation activity in 10 atmospheres of 3H2 1C0 at 260°C for supported 5 wt % cobalt decreased as Co/Si02 > Co/Ti02 > C0/AI2O3 >... 

C0/K-AI2O3. The determination of the types of cobalt species present on each support and their reduction properties were used to explain the catalysts CO hydrogenation activities. 

Table I. CO Hydrogenation Activities and Selectivities of Cobalt Catalysts1 ...

The catalysts we examined in this study contained several cobalt species with different reduction properties. In this section, we will employ those findings to explain the observed CO hydrogenation activity ranking. The differences observed in catalyst selectivity will not be addressed in this paper. 

CO hydrogenation activity was found to depend on both the amount of available surface cobalt metal and the environment of the reduced cobalt. Factors influencing these cobalt properties included the type of support, the type of cobalt species present on a given support, and the presence of additives. Due to the interrelationship of these properties, a detailed examination of the activity and structure of each catalyst is needed in order to determine the importance of each factor for CO hydrogenation activity. 

The amount, type, and reducibility of the cobalt species detected on each catalyst was important in determining its CO hydrogenation activity. 

After the experimental demonstration by Orchin and associates (13) that under oxo conditions the catalytic form of the active catalyst is cobalt hydrotetracarbonyl [systematic name, hydrogen tetracarbonyl-cobaltate( —I)], HCo(CO)4, considerable effort has been devoted to the However, see below. 

F-T Catalysts The patent literature is replete with recipes for the production of F-T catalysts, with most formulations being based on iron, cobalt, or ruthenium, typically with the addition of some pro-moter(s). Nickel is sometimes listed as a F-T catalyst, but nickel has too much hydrogenation activity and produces mainly methane. In practice, because of the cost of ruthenium, commercial plants use either cobalt-based or iron-based catalysts. Cobalt is usually deposited on a refractory oxide support, such as alumina, silica, titania, or zirconia. Iron is typically not supported and may be prepared by precipitation. 

Keyser et al. studied Mn-Co F-T catalysts and found that, under industrial relevant conditions, the WGS activity of the catalysts increases with increasing Mn content, but decreases with increasing pressure. A lower olefin yield was also observed at high pressures. It was stated that structural changes in the cobalt spinel occur over a long period of time and are responsible for the increased hydrogenation activity and increased WGS activity. Mn seems in this... 

Cobalt was the first catalyst used in commercial applications of the oxo-synthesis. In order to stabilize the HCo(CO)4 catalyst, high pressures are necessary with a maximum n/i ratio of 80/20. In the Shell process,324,325,393 cobalt catalysts modified with alkylphosphines e.g. ( )3 ( 4 9) are more selective towards linear products but exhibit high hydrogenation activity and are therefore mainly used for the direct synthesis of long chain alcohols. 

Step 1 Formation of the Active Cobalt Carbonyl Catalyst. Many efforts have been made (2, 3, 4) to prepare carbonyl catalyst by treating metallic cobalt or cobalt compounds at high temperatures (150°-200°C) and pressures with carbon monoxide and hydrogen (Reactions 1 and 2). 

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