Preparation, characterization, and activity of fluorinated aluminas for halogen exchange
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Fluorinated aluminas with α-AlF3 contents up to 90+% were prepared by treatment with the fluoroalkanes CHF3 or C2HF5at 773 K. XPS results suggest that nearly complete fluorination of the surface occurs even at low extents of bulk fluorination. Neither γ-Al2O3 nor α-AlF3 exhibits significant activity for reaction of CHF3 following adsorption at 300 K and subsequent temperature-programmed desorption. In contrast, partially fluorinated aluminas strongly adsorb CHF3, CHClF2, and CHCl2F. TPD experiments indicate that all three C1-HCFCs desorb from partially fluorinated alumina above 500 K; all react to liberate H F and CO2, and the chlorine-containing species undergo fluorine-for-chlorine exchange to produce CHF3. These results suggest that halogen-exchange reactions of HCFCs can be carried out with materials resembling conventional fluorination Catalysts. © 1989.
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