Effect of calcination temperature and fluorination treatment on NiF2-AlF3 catalysts for dehydrofluorination of 1, 1, 1, 2-tetrafluoroethane to synthesize trifluoroethylene

Abstract

High-performance NiF2-AlF3 fluoride catalysts for the catalytic dehydrofluorination of 1, 1, 1, 2-tetrafluoroethane (CF3CH2F) were prepared by impregnation and fluorination methods. The effect of calcination temperature and vapor-phase fluorination on the properties of NiF2-AlF3 catalysts were investigated by BET, SEM, XRD, UV-DRS, Raman, IR, TG and XPS. By increasing the calcination temperature, the NiO species diffused from the surface into the inside bulk phase of the alumina support and the inverse spinel NiAl2O4 was formed at a calcination temperature up to 600 °C. Vapor-phase fluorination can improve the stability of the catalytic dehydrofluorination. The unfluorinated NiAl2O4 affected the surface area and acidity of NiF2-AlF3 catalyst. The acid sites of catalysts were investigated by py-IR, disclosing that the affinity of Lewis acid sites toward activity of catalysts. In addition, it was found that the weak and medium Lewis acid sites derived from NiF2-AlF3 complex phase are active centers for catalyzing dehydrofluorination of CF3CH2F to trifluoroethylene (CF2=CHF). The highest activity was obtained over a fluorinated catalyst calcined at 500 °C, with a reaction rate of 2.13 mmol min−1 gcat.−1 and a trifluoroethylene selectivity of 99%, highlighting a good prospect for the commercial application.