Gas phase preparation method of 1, 1, 1, 2, 3, 4, 4, 4-octafluoro-2-butene

The invention discloses a gas phase preparation method of 1, 1, 1, 2, 3, 4, 4, 4-octafluoro-2-butene, and the preparation method comprises the following steps: in the presence of a fluorination catalyst, 2, 3-dichloro-1, 1, 1, 4, 4, 4-hexafluoro-2-butene and anhydrous hydrogen fluoride are subjected to fluorine-chlorine exchange reaction to obtain 1, 1, 1, 2, 3, 4, 4, 4-octafluoro-2-butene, the fluorination catalyst comprises a main catalyst, a cocatalyst and a carrier, the active metal of the main catalyst is selected from at least one of chromium, aluminum or magnesium; the auxiliary metal of the cocatalyst is selected from at least one of zinc, manganese, copper, iron, indium, lanthanum, gallium, zirconium, cerium, nickel, cobalt, magnesium or potassium; the carrier is selected from at least one of activated carbon, aluminum oxide, zirconium dioxide, magnesium oxide, magnesium fluoride, silicon carbide, carbon nanotubes or graphene. The method has the advantages of simple process, high catalytic activity,