Large heterogeneity of Brønsted acid sites in ASA and USY zeolites: evidencing a third acidic component.

Based on experimental infrared spectra of CO adsorbed on both amorphous silica-aluminas (ASA) and ultra stable Y zeolites (USY), an additional A(0) band related to high Brønsted acidic sites is evidenced. This result allows us to refine our previous assignments of the complicated and broad massifs in the nu(OH) and nu(CO) regions.