Surface Properties of Impregnated Mixed Oxide Catalysts

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Abstract
The results of a comparative study of nickel oxide‐alumina and nickel oxide‐silica alumina catalysts in the light of the characteristics of the support systems alumina and silica‐alumina are presented. The impregnation of NiO does not produce any significant change in the textural characteristics like surface area and pore volume of the support oxides. However the deposited nickel oxide leads to the modification of the surface acidity determined by Hammett indicators. In the case of parent oxides the ammonia adsorption is strong (from heat of adsorption measurement) for alumina and silica‐alumina, though for the former it is slightly stronger at comparable surface coverages. But the adsorption of ammonia on NiOAl2O3 is weak while it is strong on NiO/SiO2Al2O3 at the same comparable surface coverages. The reduction in acidity is reflected in the poor dehydration and absence of skeletal isomerisation on NiO impregnated catalysts.