High specific surface area metal fluorides as catalysts for the fluorination of 2-chloropyridine by HF

The catalytic fluorination of 2-chloropyridine into 2-fluoropyridine by Cl/F exchange in presence of HF and a metal fluoride as catalyst was investigated. Crystallized metal fluorides (BaF2, MgF2, CaF2, ZnF2, LaF3 and CeF3) with significant specific surface area between 65 and 125 m2 g−1 were prepared by thermal decomposition of corresponding metal trifluoroacetates at 350 °C under nitrogen. These solids were stable under fluorination operating conditions involved in the formation of 2-fluoropyridine. An important gain in activity for the catalytic fluorination of 2-chloropyridine was obtained with these metal fluorides compared to corresponding oxides used as catalyst. BaF2 and MgF2 were the most active catalysts for the fluorination of 2-chloropyridine. The higher activities are in relation with the weak or moderate strength of Lewis acidity of the active sites, measured by CO adsorption followed by IR spectroscopy.

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► Heterogeneous catalytic process with HF gas used to prepare 2-fluoropyridine.
► High specific surface area metal fluorides used as catalyst.
► Thermal decomposition of metal trifluoroacetates synthesis used to prepare metal fluoride catalysts.
► Fluorination of 2-chloropyridine involving unsatured metals as active sites with a weak or moderate Lewis acidity.