An FT-IR study of the chlorination of γ-alumina surfaces

Surface chlorination of two aluminas (Degussa and Condea; S-BET = 100 m(2) g(-1)) has been realized either by reaction of CHCl3 on an alumina pellet inside the IR cell or by flowing HCl(g) on alumina powder for one hour outside the IR cell. The FT-IR analysis of the chlorinated samples showed that the bands assigned to OH groups, specially in the range of higher wavenumbers (3800-3700 cm(-1)), are sensitive to the presence of chlorine on the surface taking the place of the more basic surface OH groups by substitution reaction. The nature of the additive products influenced the bands in the 1600-1200 cm(-1) region. The evolution of surfaces rehydratation showed that the chlorinated aluminas are more stable than the raw ones with respect to the presence of H2O on the surface. The hydrolysis modified the surfaces of both raw Al2O3, whereas the surfaces of the chlorinated aluminas were restored after thermal treatment at 870K. (C) 1998 Published by Elsevier Science Limited.