Kinetic Study of Europium Oxide Chlorination

The kinetics of europium oxide (Eu2O3) chlorination using gaseous chlorine as a chlorination agent was studied between 523 K and 1223 K (250 A degrees C and 950 A degrees C). The relative mass change during the chlorination reaction was continuously monitored using a high resolution thermogravimetric system. The starting temperature for the reaction of Eu2O3(s) with chlorine was determined at about 523 K (250 A degrees C) with the formation of solid europium oxychloride (EuOCl). For temperatures above 1123 K (850 A degrees C), the EuOCl(s) is chlorinated producing EuCl3(l). The influence of gaseous flow rate, sample mass, chlorine partial pressure, and temperature on the reaction rate was analyzed. The results showed that for 673 K (400 A degrees C) and temperatures below, the system is under chemical control. Concerning the influence of chlorine partial pressure, it was determined that pressures greater than 50 kPa do not modify the kinetic regime. For the experiment at 673 K (400 A degrees C), it was found that the chlorination rate was proportional to a potential function of the partial pressure of chlorine whose exponent is 0.54. The conversion curves were analyzed with the Johnson-Mehl-Avrami description. Intrinsic activation energy of 115 kJ mol(-1) was obtained for the temperature range of 573 K to 673 K (300 A degrees C to 400 A degrees C). Finally, a global rate equation that includes these parameters was developed.