An effect of promoters such as calcium, aluminium, and potassium oxides and also addition of chromium and manganese on the structure of cobalt catalysts was examined. Studies of the catalytic ammonia decomposition over the cobalt catalysts are presented. The studies of the ammonia decomposition were carried out for various ammonia-hydrogen mixtures in which ammonia concentration varied in the range from 10% to 100%. Co(0) catalyst, promoted by oxides of aluminium, calcium, and potassium, showed the highest activity in the ammonia decomposition reaction. Contrary to expectations, it was found that chromium and manganese addition into the catalysts decreased their activity.
Activity of cobalt and iron catalysts in ammonia synthesis was determined under a pressure of 10 MPa and at the temperature range of 673-823 K, in a sixchannel integral steel reactor. The catalytic ammonia decomposition was studied in a differential reactor under the atmosphere of low concentration of ammonia (\6%) in the temperature range of 673-823 K under atmospheric pressure. The determined values of the activation energy for the ammonia synthesis reaction over cobalt and iron catalysts are 268 and 180 kJ/mol, respectively, whilst for the ammonia decomposition reaction they are equal to 111 and 138 kJ/mol. The cobalt catalyst showed lower activity than a commercial iron catalyst in ammonia synthesis reaction. The cobalt catalyst turned out to be more effective in ammonia decomposition reaction than the iron one.
The effect of an alkali treatment (potassium hydroxide) on the properties of a commercial activated carbon has been studied. The aim of the treatment was to improve the adsorption properties of the material toward carbon dioxide. In the result of the treatment, silica contained in the raw carbon was removed and the density of the material increased. The changes in the surface chemistry were observed as well. The treatment of the activated carbon with KOH resulted in a complete removal of carboxy and lactone groups and a decrease of the general content of the acidic groups (more significant than that of basic groups). Simultaneously, the surface concentration of hydroxyl groups increased. The alkali treatment of activated carbon resulted in an increase of carbon dioxide uptake of 14% (measured using a volumetric method at 0 C). The adsorption of carbon dioxide on activated carbon has a mixed (physicochemical) character and that two types of adsorption sites are present at the surface. The adsorption energy varies roughly from 25 to 60 kJ/mol.
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