ACIDITY AND BASICITY OF METAL-OXIDE SURFACES .2. DETERMINATION BY CATALYTIC DECOMPOSITION OF ISOPROPANOL

In Part I of this series (Auroux, A., and Gervasini, A., J. Phys. Chem. 94, 6317 (1990)) a microcalorimetric investigation on the acid-base character of a large series of metal oxides was reported. A study concerning the acid-base catalytic properties of the same series of oxides is now reported together with a comparison with the previous results. The decomposition of isopropanol has been chosen as a test reaction to study the acid-base character of the catalytic sites of the oxides. For each oxide employed as catalyst, the rate coefficients as well as the Arrhenius parameters for both the dehydration and the dehydrogenation of isopropanol were determined. A relationship was found between the strength of the acid sites microcalorimetrically evaluated and the activation energy of the dehydration reaction, while the activation energy of the dehydrogenation reaction was independent of the strength of the catalytic sites. On the basis of the dehydration reaction, sets of oxides can be classified in scales of acid strength.