COMPARATIVE-STUDY OF THE EFFECTS OF SODIUM IMPURITY AND AMORPHIZATION ON THE LEWIS ACIDITY OF GAMMA-ALUMINA

IR experiments involving carbon monoxide and pyridine adsorption as probe molecules showed that introduction of very small amounts of sodium (300 ppm Na2O) decreased the number and the strength of the strongest Lewis acid sites. It also decreased the catalytic activity of alumina towards isopropanol dehydration used as a test reaction. The effect is comparable to that of amorphisation. It was found that the number of affected sites is one order more than the quantity of Na+ cations introduced. A tentative model was proposed and results were explained involving inductive effects.