Infrared study of the adsorption of [2H4]acetic acid on to rutile

Abstract

Infrared spectroscopic studies are reported of the adsorption of [²H₄]acetic acid onto three samples of rutile which differed in their extents either of hydration or of reduction. Acetic acid was associatively adsorbed on Lewis acidic electron acceptor Ti⁴⁺ sites in the rutile surface: this mode of adsorption was prevented by the preadsorption of water or by reduction of rutile in hydrogen. Weakly adsorbed acetic acid dimers appeared on the surface of rutile which had been pretreated in oxygen but not on reduced rutile. Chemisorption of acetic acid generated water, surface deuteroxyl groups and [²H₃]acetate ions predominantly in a highly symmetrical bidentate chelate configuration. Both the presence of adsorbed water and prereduction of rutile in hydrogen hindered the chemisorption of acetic acid on rutile.