Abstract In this research, the production of tellurium hexafluoride through the fluorination reaction of tellurium by fluorine in the gas phase was investigated in two sections experimental and theoretical. TeF6 is one of the most preva‎lent hexafluoride compounds with important industrial and significant applications. In the first study, the production of hexafluoride tellurium by the fluoridation reaction of tellurium metal was investigated. The comprehensive studies were performed on the various synthesis methods of tellurium hexafluoride through the review of scientific articles and patents. After analyzing various synthetic methods and selecting the best method, the laboratory activities were started in cooperation with Isfahan Nuclear Fuel Company (Sooreh) and the Fuel Cycle Research Institute of the Nuclear Science and Technology Research Institute (Atomic Energy Organization of Iran). The production of tellurium hexafluoride was performed by fluorination of tellurium powder in a designed laboratory system. Then, suitable conditions for the production reaction of tellurium hexafluoride such as temperature, pressure, time of fluorination, catalyst effect and amount of reactant were investigated. In these experiments; a temperature of 150 °C, time of fluorination 75 min, and pressure of 3 bar were obtained as suitable conditions for the production of TeF in a fixed bed reactor. Also, with the addition of calcium fluoride catalyst (CaF2) in these reactions; the reactivity of tellurium powder with fluorine gas increased, which is due to the opening of pores in the reactant powder in the reactor vessel and increasing the contact area of tellurium with fluorine gas. After each production of tellurium hexafluoride; qualitative and quantitative identifications of the product were performed using FT-IR spectroscopy and hydrolysis of the TeF6 in the presence of KOH or H2O and determination of Te by atomic absorption. In the second study, a theoretical study (kinetic and thermodynamic) was conducted on several proposed reaction mechanism pathways associated with the formation of TeF6 in gas phase (Te(s) + 3F2(g)  TeF6(g)). The favorable energetic pathway is initiated by the homolytic breaking of the bond of F2 molecules and the formation of [TeF]• and F• species. The reaction between these two species leads to TeF2 as an intermediate. Utilizing excess F2 (g) in the reaction, the heterolytic cleavage of F2 bond in the presence of TeF2 leads to the formation of ionic species including [TeF3]+ and F-, which react with each other to produce TeF4. The reaction of TeF4 with excess F2 (g) leads to the formation of TeF6. The optimized structures of the reactants (REs), transition states (TSs), intermediates (IMs), and products (PRs) were determined for each pathway. In the production of tellurium hexafluoride process, the reaction [TeF3]+ with F2 gas is the slowest reaction step (k = 15.71 × 10-33 m3/mol.s) and it is selected as the rate-determining step. Also in this study, the effect of temperature on the speed of the obtained reactions in the production mechanism of TeF6 was investigated. As the reaction temperature increased from 25 to 150 °C, the reaction rate increased significantly. All calculations were performed at the density functional theory (DFT) employing the M06-2X functional.

حسن حدادزاده، جواد كريمي ثابت

حسين فرّخ پور، محمّدرضا قاسمي

شهرام تنگستاني نژاد، فاطمه داور، كيومرث اسكندري، مجتبي باقرزاده