The Measurement of Surface Excess Oxygen of Nickel Oxide Catalysts by Reduction with Hydrazine

Abstract

Abstract The method for the determination of the surface excess oxygen of oxides has been provided by using aqueous hydrazine solution as a reducing reagent and applied to several pure and lithium doped nickel oxide catalysts, calcined at various temperatures from 350 to 900°C. Two different kinds of procedures, i. e., titration of the amount of hydrazine consumed and volumetric measurement of gaseous nitrogen evolved, have been employed. A satisfactory agreement is obtained between both methods, which affirms that the following reaction is taking place. N2H4+2O(S)→N2+2H2O The amount of the surface excess oxygen decreases monotonously with increasing calcination temperature and also with increasing concentration of the lithium oxide additives. From comparison of these results with those due to acidic chloride and iodide methods, most of the excess oxygen is concluded to exist on the surface of the oxides and, furthermore, a certain distribution in the oxidation power of the excess oxygen is suggested to exist.