Catalyst cobalt/alumina

Nakamura, J., Tanaka, K., and Toyoshima, 1.1987. Reactivity of deposited carbon on cobalt-alumina catalyst. J. Catal. 108 55-62. 

Chin, R.L., and Hercules, D.M. 1982. Surface spectroscopic characterization of cobalt-alumina catalysts. J. Phys. Chem. 86 360-67. 

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. 

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. 

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. 

The additional comparison on Fig. 29 shows that in the coprecipitated cobalt-alumina catalyst the cobalt is altered when the catalyst is reduced in hydrogen. The change is noted in the high energy region of the spectrum. This change is receiving additional study. 

Fra. 29. Spectra of cobalt-molybdena-alumina catalyst and related compositions, C oMo04, and a coprecipitated cobalt alumina catalyst (all three samples were calcined in air) also spectrum of cobalt-alumina catalyst reduced in hydrogen. 

Reduction. Hydrogenation of aromatic amines leads to formation of cydoalkjiamines, dicycloalkylamines, or both, depending on the reaction conditions and the type of catalyst used. Hydrogenation of aniline in the liquid phase at 25 MPa (250 atm) over a cobalt—alumina catalyst at 140°C yields cyclohexylamine [108-91-8] in 80% yield (45). Dicyclohexylamine is produced when aniline is hydrogenated in the vapor phase over a... 

Kinetic expressions similar to that of Equation 3 and similar activation energies have been reported for methanation over a cobalt-alumina catalyst (4) and for Fischer-Tropsch reaction over a cobalt-thoria catalyst (5). This similarity, despite appreciably different product distributions in the three cases, argues for a common rate-controlling step in the mechanisms. 

A number of studies have strongly suggested an effect of H2O is the oxidation of cobalt clusters for cobalt alumina catalysts, including the use of gravimetric techniques, TPD, pulse adsorption, and XPS [10-12], For the 25%Co/Al203 catalyst, the reversible effect of H2O may be due to a surface reoxidation process. The increase in CO2 selectivity (Table 9) suggests inereased WGS activity, as discussed in previous cases, potentially caused by a... 

Batista et al. performed ethanol steam reforming over cobalt/alumina and cobalt/ silica catalysts containing 8 and 18wt.% cobalt [201]. Even with a reaction temperature of400 °C, 70% conversion could be achieved. Methane was the main by-product, ethylene was only formed over samples containing 8 wt.% cobalt. Then a bed of an iron oxide/chromium oxide water-gas shift catalyst was switched behind the cobalt/ silica catalyst. The carbon monoxide was converted as expected, but also less methane was found in the product [202]. Even less carbon monoxide was formed when both catalysts were mixed. Sahoo et al. varied the cobalt content of the cobalt/alumina catalyst from 10 to 20 wt.%. The highest activity was determined for the sample containing 15 wt.% cobalt [203]. 

After reduction at 400°C, the XANES spectram (Fig. lb) displayed an intense white line, indicating a high average oxidation degree of cobalt indeed, linear fitting using a eombination of Co and CoO spectra indicated only an amount of 22% ( 3%) of metallic cobalt in the sample. This value was eorroborated by simulation of the EXAFS spectrum. In contrast to cobalt alumina catalysts, almost complete cobalt reduction to metallic phase was observed by XANES in all earbon nanotube supported samples. 

The conversion of CO to CO2 can be conducted in two different ways. In the first, gases leaving the gas scmbber are heated to 260°C and passed over a cobalt—molybdenum catalyst. These catalysts typically contain 3—4% cobalt(II) oxide [1307-96-6] CoO 13—15% molybdenum oxide [1313-27-5] MoO and 76—80% alumina, JSifDy and are offered as 3-mm extmsions, SV about 1000 h . On these catalysts any COS and CS2 are converted to H2S. Operating temperatures are 260—450°C. The gases leaving this shift converter are then scmbbed with a solvent as in the desulfurization step. After the first removal of the acid gases, a second shift step reduces the CO content in the gas to 0.25—0.4%, on a dry gas basis. The catalyst for this step is usually Cu—Zn, which may be protected by a layer of ZnO. 

Fig. 2.12. Changes in the Mo 3d XPS spectrum from a cobalt-molybdenium-alumina catalyst during successive reduction treatments in hydrogen at 500 °C [2.41]. (a) air-fired catalyst, (b) reduction time 15 min, (c) 50 min, (d) 60 min,...

Effect of Catalyst The catalysts used in hydrotreating are molybdena on alumina, cobalt molybdate on alumina, nickel molybdate on alumina or nickel tungstate. Which catalyst is used depends on the particular application. Cobalt molybdate catalyst is generally used when sulfur removal is the primary interest. The nickel catalysts find application in the treating of cracked stocks for olefin or aromatic saturation. One preferred application for molybdena catalyst is sweetening, (removal of mercaptans). The molybdena on alumina catalyst is also preferred for reducing the carbon residue of heating oils. 

The molybdenum on alumina catalyst was also tested for activity with and without arsenic. Although this catlyst has a much lower intrinsic activity for HDS, the results in Figure 4 show that 3.6% arsenic almost completely deactivates the catalyst. The small amount of activity remaining is that expected for AI2O3 alone. Thus arsenic also deactivates catalysts without cobalt promoters. 

Meunier, F.C., Zuzaniuk, V., Breen, J.P. et al. (2000) Mechanistic differences in the selective reduction of NO by propene over cobalt and silver-promoted alumina catalysts A kinetic and in situ DRIFTS study, Catal. Today, 59, 287. 

Minaev, V. Z. Zaidman, N. M. Spirina, G. A., et al., Effect of Pore Structure of Alumina-Cobalt-Molybdenum Catalyst on Activity and Stability in Hydrodesulfurization of Heavy Feedstocks. Chemistry and Technology of Fuels and Oils, 1975. 11(6) pp. 436-39. 

Synthesis of High Surface Area Cobalt-on-Alumina Catalysts by Modification with Organic Compounds... 

Cobalt-on-alumina catalysts with increased dispersion and catalytic activity are prepared by addition of mannitol to the cobalt nitrate solution prior to impregnation. Thermogravimetric analysis (TGA) and in situ visible microscopy of the impregnation solution show that the organic compound reacts with cobalt nitrate, forming a foam. The foam forms because significant amounts of gas are released through a viscous liquid. The structure of the foam is retained in the final calcined product. It is this effect that is responsible for the increased dispersion. 

Sarellas A., Niakolas D., Bourikas K., Vakros J., and Kordulis C. 2006. The influence of the preparation method and the Co loading on the structure and activity of cobalt oxide/y-alumina catalysts for NO reduction by propene. J. Colloid. Interf. Sci. 295 165-72. 

Ataloglou T., Vakros J., Bourikas K., Fountzoula C., Kordulis C., and Lycourghiotis A. 2005. Influence of the preparation method on the structure-activity of cobalt oxide catalysts supported on alumina for complete benzene oxidation. Appl. Catal. B Environ. 57 299-312. 

Agrawal, P. K., Katzer, J. R., and Manogue, W. H. 1981. Methanation over transition metal catalysts. II. Carbon deactivation of cobalt/alumina in sulfur-free studies. J. Catal. 69 312-26. 

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