Cobalt catalysts catalytic properties

Iglesia, E., Soled, S. L., Baumgartner, J. E., and Reyes, S. C. 1995. Synthesis and catalytic properties of eggshell cobalt catalysts for the Fischer-Tropsch synthesis. J. Catal. 153 108-22. 

Das, T.K., Jacobs, G., Patterson, P.M., Conner, W.A., Li, J., and Davis, B.H. 2003. Fischer-Tropsch synthesis Characterization and catalytic properties of rhenium promoted cobalt alumina catalysts. Fuel 82 805-15. 

T. K. Das, G. Jacobs, P. M. Patterson, W. A. Conner, J. Li and B. H. Davis, Fischer-Tropsch synthesis characterization and catalytic properties of rhenium promoted cobalt alumina catalysts, Fuel, 2003, 82, 805-815. 

J. Li and B. H. Davis, Effect of water on the catalytic properties of supported cobalt Fischer-Tropsch catalysts, Stud. Surf. Sci. Catal., 2004, 147, 307-312. 

The oxidation of propene to acrolein has been one of the most studied selective oxidation reaction. The catalysts used are usually pure bismuth molybdates owing to the fact that these phases are present in industrial catalysts and that they exhibit rather good catalytic properties (1). However the industrial catalysts also contain bivalent cation molybdates like cobalt, iron and nickel molybdates, the presence of which improves both the activity and the selectivity of the catdysts (2,3). This improvement of performances for a mixture of phases with respect to each phase component, designated synergy effect, has recently been attributed to a support effect of the bivalent cation molybdate on the bismuth molybdate (4) or to a synergy effect due to remote control (5) or to more or less strong interaction between phases (6). However, this was proposed only in view of kinetic data obtained on a prepared supported catalyst. 

Fischer-Tropsch synthesis making use of cobalt-based catalysts is a hotly persued scientific topic in the catalysis community since it offers an interesting and economically viable route for the conversion of e.g. natural gas to sulphur-free diesel fuels. As a result, major oil companies have recently announced to implement this technology and major investments are under way to build large Fischer-Tropsch plants based on cobalt-based catalysts in e.g. Qatar. Promoters have shown to be crucial to alter the catalytic properties of these catalyst systems in a positive way. For this reason, almost every chemical element of the periodic table has been evaluated in the open literature for its potential beneficial effects on the activity, selectivity and stability of supported cobalt nanoparticles. 

The solvent is a sine qua non of a homogeneous catalyst system. Solvent properties are indeed very important in determining the activity, selectivity, and stability of a catalyst. Solvent stability is also essential, if the catalytic system as a whole is to be stable. As described above, several solvents have been employed in studies of cobalt-catalyzed CO reduction. Keim et al. (39) noted a substantial difference in activity and selectivity between catalyst solutions in toluene and W-methylpyrrolidone (Table I). Most of the information in this area again comes from the work of Feder and Rathke (36). Listed in Table IV are their results showing changes in the activity of the cobalt catalyst corresponding to changes in solvent polarity. The rates... 

Recently, the cobalt(II)-tetrasulfonatophthalocyanine system was reinvestigated for its catalytic activity while intercalated into a Mg5Al2 -layered double hydroxide. The intercalate exhibited catalytic properties in the activation of atmospheric dioxygen for the oxidation of a thiolate to a disulfide (97a) and for the oxidation of 2,6-di-tert-butylbenzene to (nearly exclusively) the 2,6,2, 6 -tetra-tert-butyldiphe-noquinone (97b). In marked contrast to the results reported for the homogeneous catalyst, this intercalated catalyst remained active for... 

On the other hand, it is known that catalyst support exerts a great influence on the catalytic properties of the metallic particles deposited on it during the carbon dioxide reforming of methane. So for a given metal, catalytic activities can be changed [5], product selectivities modified [6] and carbon deposition resistivity altered [7]. Also the addition of certain promoters can improve the catalytic behavior of a given supported metal catalyst. In particular we have shown the benefit of the MgO addition to cobalt catalyst [ 8, 9]. 

Haga, F, Nakajima, T., Miya, H., and Mishima, S. Catalytic properties of supported cobalt catalysts for steam reforming of ethanol. Catalysis Letters, 1997, 48 (3), 223. 

Enache, D.I., Roy-Auberger, M., and Revel, R. Differences in the characteristics and catalytic properties of cobalt-based Fischer-Tropsch catalysts supported on zirconia and alumina. Applied Catalysis. A, General, 2004, 268, 51. 

The Transition Metal Sulfides are a group of solids which form the basis for an extremely useful class of industrial hydrotreating and hydroprocessing catalysts. Solid state chemistry plays an important role in understanding and controlling the catalytic properties of these sulfide catalysts. This report discusses the preparation of sulfide catalysts, the role of disorder and anisotropy in governing catalytic properties, and the role of structure in the promotion of molybdenum disulfide by cobalt. 

In order to elucidate the reasons for the dependence of the catalytic properties of these samples on their preparation method, we studied the acid surface properties of cobalt- and chromium-modified Zr02 catalysts by ammonia thermoprogrammed desorption and IR-spectroscopy. Our results again indicated that the activity of these catalysts in the SCR of NOx by hydrocarbons is a function both of the surface acidity and content of the active metal. The acid site concentration of the starting Zr02 samples prepared by various methods is significant (0.13 and 0.23 mmol/g) but these samples are inactive, while 10% CriOilZtOi prepared by the sol-gel method displays considerable activity in the reaction studied with lower surface acidity. The acid site concentration of the sample with the same composition prepared by the precipitation method is reduced by a factor of 2.5 and, thus, this catalyst has much lower activity in the selective catalytic reduction. 

It has been established from these studies that the different catalytic properties of transition metal oxides (chromium, cobalt) on zirconium dioxide are attributed to their different acidic properties determined by TPDA and IR-spectroscopy. The most active catalyst is characterized by strong acidic Bronsted centers. The cobalt oxide deposited by precipitation on the zirconium-containing pentasils has a considerable oxidative activity in the reaction N0+02 N02, and for SCR-activity the definite surface acidity is necessary for methane activation. Among the binary systems, 10% CoO/(65% H-Zeolite - 35% Z1O2)... 

It is well known that addition of base metal oxides can enhance the catalytic properties of noble metals. Addition of CeOa in three-way catalysts has improved the performance by the ability to store oxygen, promote the water-gas-shift reaction, stabilise the alumina support, suppress strong Rh-ALOa interactions and promote noble metal dispersion [4-5]. Beside the precious metals, oxides of the first row of transition metals are generally active as oxidation catalysts. By promoting Pt and Pd with cobalt oxide it has recently been shown that the activity for oxidation of CO and propene is significantly increased [6-10]. 

The mono- and bimetallic substituted MCM-41 catalysts with cobalt, vanadium or lanthanum have been prepared by direct synthesis or impregnation and characterized by various techniques, such as XRD, N2 adsorption-desorption, SEM, TEM and TGA. The catalytic activity in the selective oxidation of styrene with H2O2 has been evaluated. Adsorption of benzene and ammonia on the mono- and bimetallic mesoporous molecular sieves with cobalt and vanadium has been studied by IR spectroscopy and the results have been correlated with their catalytic properties and the characteristics of the structure. Co-incorporated catalysts prepared by direct synthesis show to be very active and selective. 

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