KINETICS OF CHLORINATION AND CARBOCHLORINATION OF VANADIUM PENTOXIDE

Kinetics of chlorination of V2O5 with Cl-2-air, Cl-2-N-2, and Cl-2-CO-N-2 gas mixtures have been studied by nonisothermal and isothermal thermogravimetric measurements. In the temperature range of 500 degrees C to 570 degrees C, the chlorination of V2O5 with Cl-2-N-2 gas mixture is characterized by an apparent activation energy of about 235 kJ/mole. This could be attributed to chemical reaction. Between 570 degrees C and 650 degrees C, the apparent activation energy is equal to 77 kJ/mole, indicating that the overall reaction rate is controlled by chemical reaction and pore diffusion. The reaction order with respect to chlorine is 0.78. The apparent activation energy of the carbochlorination of V2O4 by Cl2CO-N-2 mixture is about 100 kJ/mole in the temperature range of 400 degrees C to 620 degrees C. In this case, the chemical reaction is the limiting step. At temperatures higher than 620 degrees C, an anomaly is observed in the Arrhenius plot, probably due to thermal decomposition of COCl2 formed in situ and/or transformation of the vanadium oxide physical state. The maximum reaction rate is obtained by using a Cl-2-CO-N-2 gas mixture having a Cl-2/CO volume ratio equal to about 1.