Catalyst cobalt-oxide

Cobalt and compounds SPA Cobalt oxide Catalysts Eibres Paint Paper and pulp processing Tungsten carbide binder... 

In both processes the CO can be converted to CO2 by passing the gases and steam over an iron oxide or cobalt oxide catalyst at 400°C, thereby generating more hydrogen ... 

Cobalt and compounds SPA Cobalt oxide Catalysts Fibres... 

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. 

A total of206 mg [119] of commercial Cu/Zn catalyst from SiidChemie (G-66MR) ground to the nanometer range was coated into the channel system at 5 pm thickness to promote the steam reforming reaction. A cobalt oxide catalyst was prepared by impregnating the corundum layer (see above) with cobalt nitrate and calcining at 350 °C for 2 h 434 mg [119] of the CoO catalyst were applied for the combustion reaction (see Section 2.5). 

Cobalt oxide (C03O4) catalysts are being used in some nitric acid plants as an alternative to platinum-rhodium (Pt-Rh). They generate less N2O, cost less and have a longer campaign life than Pt-Rh gauzes. (A paper in 2000 reported a conversion rate of ammonia to nitrous oxide as low as 0.5% over cobalt oxide catalyst)222. 

However cobalt oxide does have some drawbacks. Lower ammonia conversion efficiencies have been reported - as low as 88% to 92% in a high pressure plant compared with a typical value between 94% and 95% for Pt-Rh gauzes. The optimum operating temperature is 70 to 80°C lower than for Pt-Rh gauzes, and this could result in difficulties with the steam balance in a revamped plant. Cobalt oxide catalysts also suffer from reversible deactivation due to the reduction ofCo304 to CoO in the upper parts of the catalyst bed222. 

Our recent studies of cobalt oxides catalyst deposited on y-alumina indicate unexpected activity of C0-O/AI2O3 in oxidative cracking of n-butane at low temperature. High yield of olefins 30% (mostly ethylene and propylene) was reached at 550°C and WHSV - 4.5h" [8]. Furthermore varying of oxygen concentration affects olefins distribution. Such essential features of cobalt oxide catalyst render it interesting as a base for catalyst development. 

In Figure 5, however, it is seen that the pre-treatment atmosphere has a significant effect on the low temperature activity of Pd/Co/AbOa. The effect of catalyst pre-treatment is most pronounced for the cobalt oxide catalyst promoted with Pd or Pt (see Table 2). In lean reactant gas, pre-reduced Pd/Co/AbOs has light-off temperatures at 169°C and 177°C for CO and HC, respectively, whereas the light-off temperatures over the same catalyst, but pre-oxidised, are 246°C for both CO and HC. A clear effect of pre-reduction is also seen for Pt/Ce/Ab03, whereas no obvious effect of the pre-treatment atmosphere on the oxidation activities for CO or HC is seen for Pd/Ce/AbOs. 

B. Chen, C. Bai, R. Cook, J. Wright, C. Wang. Gold/cobalt oxide catalysts for oxidative destruction of dichloromethane. Catalysis Today, 30 15-20,1996. 

Figure 6. The addition of a promoter (P) to ANL s cobalt/oxide catalyst improves its WGS activity at temperatures below 350°C to give it higher activity than commercial iron-chrome (Fe-Cr). GHSV = 30,000 hr, "High CO" reformate...

Products of incomplete combustion have been shown to increase as the catalyst deactivates. Agarwal et al. report that the oxidation of a mixed stream of trichloroethylene and C5-C9 hydrocarbons over a chromia alumina catalyst produced CO equal to 32% of the total CO + CO2 with fresh catalyst. With a deactivated catalyst, CO had risen to 54% of the total carbon oxides produced. Pope et al. report products of incomplete combustion for the oxidation of 1,1,1-trichloroethane over a cobalt oxide catalyst. The cause of the catalyst deactivation has not been established, but both Agarwal et al. and Michalowiczl reference evidence of carbonaceous deposits on the catalyst after oxidation of halogenated hydrocarbons. ESCA studies by Hucknall et al. O have always shown a carbon residue on palladium alumina catalysts in addition to adsorbed halogen. 

N. Bahlawane, Kinetics of methane combustion over CVD-made cobalt oxide catalysts Appl. Catal. B-Environ., 2006, in press. 

Table 1 Surface areas of oxide supports and catalytic activities of supported cobalt oxide catalysts for methane combustion ...

For certain reactions that involve one reactant, the rate is independent of the concentration of the reactant over a wide range of concentrations. For example, the decomposition of hypochlorite on a cobalt oxide catalyst behaves this way. The reaction is... 

The cobalt oxide catalyst forms when a solution containing Co is added to the solution containing OCl . It is likely that some of the cobalt is also oxidized to Co, so we wiU write the catalyst as C02O3, even though it is probably a mixture of CoO and C02O3. 

Fig. 11. TPR profiles of the carbon nanofibers supported cobalt oxide catalysts.

Figure 7 shows clearly the positive effect of the addition of cobalt oxide to a Pt catalyst on the NO conversion. It was found earlier that when the coverage of NO is high, more NjO is formed than at low NO coverage (4, 11). Nj is formed when the surface of the catalyst is covered with much N. Hence, at a lower CO/NO ratio, more NjO formation can be expected. Reaction 5 is favored at lower temperatures (4, 11, 21, 22). This explains why the temperatures of NO conversion are lower for CO NO = 1 2.5. Figure 7a shows a maximum around 300°C for the CoO catalyst. This has also been found for the NO/H2 reaction over the same catalyst. The maximum corresponds to the maximum in N2O formation. Hence, most likely, the maximum in conversion observed for the CO/NO reaction around 300°C is also caused by N2O formation. Thus it seems that the main reaction product over the oxidized cobalt oxide catalyst is N2O. 

Approaches for the synthesis of adipic acid are shown in Figure 2.12. The basic raw materials are benzene, cyclohexane, phenol, acrylates, and butadiene. The principal commercial processes are based on the oxidation of cyclohexane, which usually proceeds in two stages. The first step entails oxidation with air, yielding either a mixture of cyclohexanone and cyclohex-anol (process 1, Figure 2.12) or predominantly cyclohexanol (process 2, Figure 2.12). These reaction products are oxidized in the second stage with nitric acid to adipic acid. Process 1 employs a soluble cobalt oxidation catalyst [133], reaction temperatures in the range of 150 160°C, pressures between 800 and 1000 kPa, and catalyst concentrations of 0.3-3 ppm. At conversions of 5-10%, the selectivity with respect to the cyclohexanone yclohexanol mixture is about 70 80 mol %, with an alcohol/ketone ratio of about 2 1. In process 2 the oxidation is carried out in the presence of boric acid or its anhydride. This results in mixtures particularly... 

The discovery of hydroformylation by Otto Roelen was made while investigating the influence of alkenes on the Fischer-Tropsch reaction using a heterogeneous cobalt oxide catalyst supported on silica. Later it was concluded that hydroformylation is actually a homogeneous process catalyzed by ECo(CO) formed in situ. Many metals catalyze hydroformylation, but the most active catalysts contain cobalt, rhodium, palladium, and platinum as the central metal. The discussion in this chapter centers on the most utilized catalysts ECo(CO), ECo(CO)3PR3, ERh(CO)3(PR3)j, and HRhfCOljfdiphosphine). 

Reuse et al. [16] combined endothermic methanol steam reforming with exothermic methanol combustion in a plate heat exchanger reactor, which was composed of a stack of 40 foils (Figure 24.5). Each foil carried 34 S-shaped channels. Cu/ZnO catalyst from Siid-Chemie (G-66MR) was coated into the channel system for the steam reforming reaction. Cobalt oxide catalyst served for the combustion reaction. The reactor was operated in co-current mode. The steam reformer was operated at a S/C ratio of 1.2. At reaction temperatures between 250 and 260 °C, more than 95% conversion and more than 95% carbon dioxide selectivity were achieved. 

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