Browsing by Author "Griffiths, David M"

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Infrared Study of the Adsorption of [2H4]Acetic Acid on to Rutile
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (12), 1977) Griffiths, David M; Rochester, Colin H
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.
Infrared Study of the Adsorption of Hexafluoroacetone on to Rutile
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (12), 1977) Griffiths, David M; Rochester, Colin H
Infrared spectra have been recorded of hexafluoroacetone adsorbed on four samples of rutile which differed in their extents of dehydration by thermal activation or of reduction in hydrogen. Physically adsorbed hexafluoroacetone molecules interacted as hydrogen bond acceptors with surface hydroxyl groups, as electron donors with Ti4+ ions, and as electron acceptors with Ti3+ ions. Chemisorptive interactions involving surface hydroxyl groups or O2– ions led to the formation of trifluoroacetate ions and precursor species resembling salts of hexafluoropropan-2,2-diol. In general, reduction of rutile in hydrogen weakened adsorptive interactions involving H-bond donation or electron acceptance by the oxide surface. In contrast interactions involving electron donation or nucleophilic attack of hexafluoroacetone by hydroxyl groups or O2– ions were enhanced by reduction of the oxide in hydrogen.
Infrared Study of the Adsorption of Water on to the Surface of Rutile
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (10), 1977) Griffiths, David M; Rochester, Colin H.
Infrared spectra of the surface of three samples of rutile which had been (a) calcined in air at 723 K and heated in oxygen at 673 K, (b) calcined in air at 973 K and heated in oxygen at 673 K, and (c) calcined in air at 723 K and heated in hydrogen at 673 K have been recorded as a function of the extent of hydroxylation and hydration of the oxide surface. The adsorption and desorption characteristics of associatively adsorbed and chemisorbed water on rutile have been established in detail and are discussed primarily in terms of adsorptive interactions involving the {110}, {100} and {101} surface planes. Calcination of rutile at high temperature (973 K) enhanced the chemisorption of water on {110} planes at the expense of the associative adsorption of water on Ti4+ ion sites in the {100} and {101} planes. Mild reduction of rutile in hydrogen decreased the ability of the oxide to adsorb water molecularly. The effect of reduction was completely reversed by subsequent heat treatment of the oxide in oxygen.