Abstract: Octafluoropropane or perfluoropropane is produced by introducing fluorine into an elongated inner zone surrounded by a porous member which is substantially resistant to fluorine corrosion and introducing a three carbon compound which is propane, a partially fluorinated propane, propene, a partially fluorinated propene, hexafluoropropene or mixtures thereof outside the porous member. When the porous member is metal, a perfluorinated diluent is used. When the porous member is fused alumina, conventional diluents such as nitrogen, or even no diluent may be employed.