Direct Oxyfluorination of Hydrocarbons on Metal Fluorides

A critical overview of the recent literature data and of our results on the oxyfluorination of C–H to C–F bond with metal fluorides is presented. Some important aspects that require further investigation, in order to obtain a better understanding of the reaction mechanism and to develop a general approach to catalysts design are discussed. In particular, the oxyfluorination of ethene, utilizing different metal fluorides, in pulse and continuous reactors, was studied. Obtained results indicated that the presence of mixed fluorides with a fluoroperovskite structure, such as AgCuF₃, led to improved reactant conversion and higher selectivity to vinyl fluoride, in comparison to the single metal fluorides. CO₂ is formed from secondary parallel reaction upon ethene oxidation, because of the presence of metal oxides in the catalysts. The difficulties met in the regeneration of the Ag° formed during oxyfluorination, addressed the search for new metal fluorides as starting materials for the synthesis of perovskite-like materials. Still, among the prepared mixtures only in the case of AgCuF₃ the formation of perovskite-like materials was evidenced by means of XRD; such behaviour is explained by means of the Goldschmidt factor t.