KINETICS OF CHLORINATION OF NIOBIUM PENTOXIDE BY CARBON-TETRACHLORIDE

Kinetics of the chlorination of Nb2O powder by CCl4 vapor in mixture w ith N-2 in a static bed in the temperature range of 698 to 853 K were carried out at different partial pressures of CCl4 (pCCl(4)), varying from 0.10 to 0.75 atm. The fraction of Nb2O5 chlorinated R at pCCl(4) of 0.6 atm in the temperature range of 698 to 773 K was found to be pr oportional to time t, and the activation energy E is calculated to be 112 kJ/mole. Results on the effect of pCCl(4) (0.4, 0.6, and 0.75 atm) at 723 K suggest that the rate v (R/min) is proportional to p(CCl4)(1 .5). However, at p(CCl4) of 0.2 atm, R is not linear with t, rather, R (1/2) is linear with t. Based on these results, two mechanisms, one at low p(CCl4) (0.2 atm) and another at higher p(CCl4) values, in the te mperature range of 698 to 773 K have been suggested. Similar studies i n the higher temperature range (793 to 853 K), where P-CCl4 values, R is found to be directly proportional to t. At two higher p(CCl4) (0.4 and 0.6 atm), v is proportional to p(CCl4), whereas at two lower p(CCl 4) (0.1 and 0.2 atm) it is proportional to p(CCl4)(0.5). The E values obtained in the temperature range of 793 to 853 K at P-CCl4 of 0.6 and 0.2 atm are found to be 57 and 115 kJ/mole, respectively. In this hig her temperature range, two different reaction mechanisms have been pro posed.