Differential utilization of the surface of aluminum oxide in the production of complex and mixed catalysts
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The method of adsorption of nickel carbonyl on aluminum oxide, followed by decomposition, can be used for the production of Ni/Al2O3 catalysts, the activity of which per gram of the catalyst in the hydrogenation of CO2 is somewhat greater than that of samples obtained by the usual methods of impregnation or coprecipitation. Repeated adsorption with blocking permits a substantial increase in the activity.
In an investigation of the dependence of the catalytic activity on the nickel content, the existence of a lower concentration threshold was detected, the absolute value of which depends on the method of preparation of the catalyst and the properties of the initial aluminum oxide. Evidently this phenomenon is due to the different strength of the chemisorption bond to the surface and to difference in the sizes of the nickel crystallites.
For the investigated catalysts the specific catalytic activity of Ni in the region of nickel concentrations above the critical threshold retains approximate constancy, while the activation energy changes appreciably in the region of very low and comparatively high concentrations. A substantial influence on the catalytic activity is exerted by the nature of the surface inhomogeneity of the initial aluminum oxide.
KeywordsNickel Activation Energy Catalytic Activity Chemisorption Critical Threshold
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