FT-IR studies of internal, external and extraframework sites of FER, MFI, BEA and MOR type protonic zeolite materials

FT-IR studies of the adsorption of nitriles show that the external surface of H-FER, H-MFI, and H-MOR carries terminal silanols and strong Lewis sites. Terminal silanols present wide heterogeneity with respect their Brønsted acidity also in relation to the zeolite structure. Bridging Si-(OH)-Al exist at the internal channel surface only of H-FER and H-MFI and are stronger Brønsted acids than the external terminal silanols. The distinction of the bridging Si-(OH)-Al sites located in the different channels of H-BEA and H-MOR can be obtained. Extraframework material can be located both at the internal channel surface and at the external surtface of H-MFI and H-BEA.