Journal Archive Collections

Permanent URI for this communityhttp://localhost:4000/handle/123456789/16937

Browse

Has files: YesSubject: search.filters.subject.Hydroxyl Groups

Search Results

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Characterization of the Hydroxyls in Offretitc Zeolite
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (07), 1978) Mirodatos, Claude; Abou-Kais, Antoine; Vedrine, Jacques C.; Barthomeuf, Denise
    It is shown that three structural hydroxyl groups are generated in offretite upon cation exchange. The 3660 cm–1 OH groups are either not acidic or only slightly so and are probably located in the inaccessible hexagonal prism (O6H). The 3610 and 3550 cm–1 hydroxyls are acidic. Their strength increases at low cation content. The 3610 cm–1 groups are mainly located in the channel (O5H) while the low frequency groups are suggested to be in the cancrinite cage (O2H or O4H).
  • No Thumbnail Available
    Item
    Hydrogen Bond Strengths and Acidities of Hydroxyl Groups on Silica-Alumina Surfaces and in Molecules in Solution
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (11), 1974) Rouxhet, Paul G.; Sempels, Raymond E.
    The properties of hydroxyl groups on mixed silica–alumina gels (0–50 % Al2O3) have been studied by adsorbing weak H bond accepting molecules onto the gels and recording the OH stretching infrared band. Additional measurements on silica gel and compilation of numerous literature data have shown that frequency shift measurements, or series of ΔvOH measurements condensed into BHW (Bellamy, Hallam and Williams) slopes, provide a reliable estimate of the OH acidity. The resulting scale is independent of the atom to which the hydroxyl is attached; it may be used for surfaces of solids as well as for solutions. The results obtained for silica–alumina show that two distinct populations of hydroxyl groups are present. Hydroxyl groups of type 1 are identical with those present on the surface of silica. The spectra show the presence of hydroxyl groups of a second type, the proportion of which increases as the Al content of the gel rises; their acidity corresponds to a pKa between –4 and –8 and they are presumably the sites responsible for the protonation observed upon adsorption of pyridine or ammonia.