Abstract
The influence of oxygen on the concentration of perylene cation radicals on the surface of alumina (measured by means of ESR) has been traced. By means of perylene adsorption in the presence and in the absence of molecular oxygen, the acidic (acceptor) properties of a series of A1 20 3NaOH catalysts has been investigated. The Benesi method [ J. Phys. Chem. 61, 970 (1957)] was used to estimate the distribution of the acidic centers strength of examined catalysts. With an increasing amount of sodium ions, the acidic properties of alumina decrease. The maximal amount of the strongest centers Ho ⩽ −13.1 for pure alumina and alumina containing 0.1 mmol NaOH g −1 Al 20 3 equal 2.0 mmol g −1 was obtained. For some catalysts, relationship have been found between the acidic properties and perylene adsorption ( n-butylamine titration in the presence of perylene as an indicator). It has been established that the acidity of alumina centers which causes the perylene conversion is in the range of −3.0 ⩾ Ho ⩾ −5.6 or higher. By applying the relation of Aalbersberg to the perylene adsorption data we have proposed a mechanism of monopositive ion formation.
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