A Novel Ni/NiF ₂ -AlF ₃ Catalyst with Mild-Strength Lewis Acid Sites for Dehydrofluorination of 1, 1, 1, 2-Tetrafluoroethane to Synthesize Trifluoroethylene

A novel Ni/NiF ₂ -AlF ₃ catalyst was prepared by impregnation and following vapor hydrofluorination, and it was used to dehydrofluorination of tetrafluoroethane to trifluoroethylene. BET, SEM, XRD, XPS, NH ₃ -TPD and Py-IR techniques were employed to characterize the Ni/NiF ₂ -AlF ₃ catalysts. Based on the NH ₃ -TPD results, it was interestingly found that the strong acidic sites of Ni/NiF ₂ -AlF ₃ catalyst transformed into the mid-strength acidic sites with the increase of Ni loading, attributing to the roles of Ni on the catalyst surface. Compared with the NiF ₂ -AlF ₃ catalyst, the added Ni particles can improve the catalyst activity and stability for dehydrofluorination of 1, 1, 1, 2-tetrafluoroethane. The best performance was obtained at Al/Ni=2 over the Ni/NiF ₂ -AlF ₃ catalyst, with high trifluoroethylene selectivity(99%) and CF ₃ CFH ₂ conversion of 21.3%, after the reaction for 20 h on-time stream at 500 °C, which showed the better application possibility as a heterogeneous dehydrofluorination catalyst. It was suggested that catalytic performance was related with the mid-strength Lewis acidity on the catalyst surface. And the Ni/NiF ₂ -AlF ₃ catalyst (Al/Ni=2) possessed the good catalytic stability due to the mild-strength Lewis acid sites.