Acid-base properties of alumina prepared from a hydrated product of centrifugal thermal activation of hydrargillite (cta-product)

Summary

Acid-base properties of aluminas prepared by thermal treatment of a hydrated CTA-product at 600°C were studied. The CTA-oxides, representing γ-Al₂O₃, were shown to contain terminal and bridged OH-groups. The concentration of the terminal OH-groups in the CTA-oxides was found to exceed their concentration in γ-Al₂O₃ prepared by dehydration of the “precipitated” pseudoboehmite, whereas the concentration of the bridged OH-groups in the CTA-oxides was lower than that in γ-Al₂O₃ prepared from pseudoboehmite. The total concentration of the surface Lewis acid sites in CTA-oxides varies within the limits of 2.80-4.14 mmol/m² and is essentially above that in g-Al₂O₃ (2.25 mmol/m²). The distinctive feature of the CTA-oxides is that their surface contains strong Lewis acid sites with n_CO = 2220 and 2238 cm^-1. The total concentration of basic sites in the CTA-oxides is lower than that in g-Al₂O₃, however, in contrast to g-Al₂O₃,they contain strong basic sites with n_CDCl3 = 2200 cm^-1.