Fluorinated chromia conversion

It will be apparent from the topics described in the sections above that fluorinated chromia has subtleties that are not completely understood and in some catalytic systems have so far been described incompletely. Some factors are clear however. The surface properties depend crucially on the extent of surface prefluorination. Although many laboratory studies have employed CFC or better HFC reagents, such surfaces are normally lightly fluorinated only, and in the case of CFCs will inevitably contain surface chloride species that complicate interpretation of the catalysis. For large-scale applications, anhydrous HF is the prefluorination (and fluorination) reagent of choice. The process is slow and, even at the surface level, is probably never complete. This is beneficial, since complete conversion to a chromium(in) fluoride layer, it is generally agreed, would result in a catalyst whose activity was very low or which was inactive. 

The addition of chromia and magnesia to ahimina enhances conversion of CFC-12 even at a tenq)erature of 275°C conq>ared to the other catalysts in the CMA coprecipitated catalyst. And high selectivity towards fluorine rich conqx>und CFC-13 is maintained at all temperatures. The constant high conversions beyond 375°C on more active catalysts i.e. on CMA, CA-I, CA-C indicate the possibility of occurrence the... 

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