Infrared studies on the acidity of metal impregnated ZSM-5

Abstract The Bronsted and Lewis acidity of ZSM-5 supported catalysts containing iron or cobalt is investigated by the characterization of chemisorbed pyridine with infrared spectroscopy. The impregnation of cobalt or iron from aqueous or acetone solutions of metal nitrates causes a redistribution of the relative number of Bronsted and Lewis acid sites in the ZSM-5. This redistribution is postulated to be the result of ion-exchange of cobalt or iron ions for acidic protons within the channels of the ZSM-5. Preparing iron on ZSM-5 by physically mixing Fe 2 O 3 with the ZSM-5 causes no acidity redistribution and hence no ion-exchange.