The dimerization reaction of tetrafluoroethylene (CF₂=CF₂, TFE) was carried out to produce octafluorocyclobutane (C₄F₈, RC318). In order to control the reaction temperature for an exothermic dimerization of TFC, the fluidized bed reactor was employed with steam. RC318 was mainly produced with a little amount of by-products such as Hexafluoropropylene (CF₃CF=CF₂), Trifluoroethylene (CF₂=CHF, TrFE), Pentafluoroethylene (CHF₂CF₃, R125), Chlorotrifluoropentane (CF₂=CFCl, CTFE). The conversion of TFE and the selectivity of RC318 were greatly affected by the temperature and the contact time. The selectivity of HFP in the dimerization of TFE greatly increased by feeding steam in a fluidized bed reactor. It was found that the formation of solid polymer was minimized in a fluidized bed reactor system.