The catalytic dehydrofluorination of CF3CH3 was studied over various metal phosphate catalysts in a fixed-bed reactor. The Mg2P2O7 catalyst exhibited the moderate activity and high selectivity of CF2CH2, and it is the most suitable catalyst for the dehydrofluorination of CF3CH3. Deactivation did not take place during the 100 h reaction over the Mg2P2O7 catalyst, and XRD patterns of the catalyst were unchanged after 100 h reaction. However, small amounts of F- ions were present on the surface of the catalyst from results of XPS. The active sites for CF2CH2 formation are weak acid sites of the catalysts, and carbon deposition and/or polymerization take place on strong acid sites. Results of CF3CH3-TPD indicated that the dehydrofluorination proceeds through a +CF2CH3 carbonium-ion mechanism over Mg2P2O7 catalyst, and the rate-determining step is the cleavage of the C-F bond. 1998 Elsevier Science B.V.