Kinetics of tetrachloromethane fluorination by hydrogen fluoride in the presence of antimony pentachloride

Contradictory information concerning the kinetics of tetrachloromethane fluorination by anhydrous hydrogen fluoride in the presence of antimony pentachloride has been explained. The present studies were performed using a stainless steel autoclave. The exchange of the first chlorine atom was carried out in the temperature range of 35-95 °C, with the molar ratio of HF/CCl₄ varied within the range of 1.2-1.7 and at a constant molar ratio of SbCl₅/Cl₂ equal to 1.9. The degree of conversion of CCl₄ to CCl₃F and the reaction rate constant as a function of temperature fit to an Arrhenius straight line. The Arrhenius constants (pre-exponential factor) and the activation energy were determined. Studies concerning the exchange of the second chlorine atom, i.e. the conversion of CCl₃F to CCl₂F₂ have been performed. The results of kinetic investigations were created in the same way. Based on these results it was found that the Arrhenius equation is fulfilled also in the second stage of the fluorination. The same slope of the straight lines confirms that the fluorination stages proceed according to the same mechanism with the same activation energy but with different pre-exponential factors.Several kinetic problems associated with the performance of the reactor can be solved on the basis of the equations derived. However, knowledge of CCl₄ conversion as a function of time, temperature, catalyst concentration and the type of the reaction is required for this purpose. Such calculations enable the selection of the optimal process parameters.