A comparative study of surface acidity in the amorphous, high surface area solids, aluminium fluoride, magnesium fluoride and magnesium fluoride containing iron(III) or aluminium(III) fluorides

Nickkho-Amiry, M., Eltanany, G., Wuttke, S., Rudiger, S., Kemnitz, E. and Winfield, J. M. (2008) A comparative study of surface acidity in the amorphous, high surface area solids, aluminium fluoride, magnesium fluoride and magnesium fluoride containing iron(III) or aluminium(III) fluorides. Journal of Fluorine Chemistry, 129(5), pp. 366-375. (doi: 10.1016/j.jfluchem.2008.01.017)

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Abstract

The behaviour of the sol-gel prepared, amorphous solids, high surface area (HS) aluminium fluoride and magnesium fluoride in promoting room temperature dehydrochlorination of tert-butyl chloride (Bu'Cl), in their catalytic activity for the dismutation of chlorodifluoromethane and in the temperature programmed desorption of ammonia is similar, indicating that, unexpectedly, both solids exhibit significant surface Lewis acidity. Using a similar approach, it has been demonstrated that surface Lewis acidity in HS-MgF2 is enhanced by the incorporation of amorphous iron(Ill) fluoride and probably also by amorphous aluminium(III) fluoride. A second, unexpected feature is the substantial retention of anhydrous hydrogen chloride by all the solids, which is observed by the use of chlorine-36 labelling, when they are exposed at room temperature either to Bu'Cl or to HCl directly. The detailed behaviour of (HCl)-Cl-36 towards HS-AlF3 depends on the fluorinating agent, dichlorodifluoromethane or anhydrous hydrogen fluoride, which is used in the second stage of HS-AlF3 synthesis. This observation and the pattern of the results obtained overall lead to the proposal that strongly adsorbed HCl behaves as an unconventional Lewis base towards these solids. .

Item Type:Articles
Keywords:1,1,1-TRICHLOROETHANE ADSORPTION aluminium fluoride Aluminium(III) fluoride Ammonia CATALYTIC ACTIVITY CHLORIDE chlorine-36 CHLOROFLUORIDE ACF dehydrochlorination FLUORIDES FLUORINATED SURFACES GAMMA-ALUMINA HCL high surface area HYDROGEN HYDROGEN-CHLORIDE HYDROGEN-FLUORIDE IRON(III) lewis acid Lewis acidity LEWIS-BASE MAGNESIUM FLUORIDE METAL FLUORIDES ROOM-TEMPERATURE SOLIDS SURFACE SURFACE-AREA TEMPERATURE
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Winfield, Professor John
Authors: Nickkho-Amiry, M., Eltanany, G., Wuttke, S., Rudiger, S., Kemnitz, E., and Winfield, J. M.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Journal of Fluorine Chemistry
ISSN:0022-1139

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