Chlorination of Lanthanum Oxide

Abstract

The reactive system La2O3(s)−Cl2(g) was studied in thetemperature range 260−950 °C. The reaction course was followed bythermogravimetry, and the solids involved were characterized by X-raydiffraction, scanning electron microscopy, and energy dispersive spectros-copy. The results showed that the reaction leads to the formation of solidLaOCl, and for temperatures above 850oC, the lanthanum oxychloride ischlorinated, producing LaCl3(l). The formation of the oxychlorideprogresses through a nucleation and growth mechanism, and the kinetic analysi showed that at temperatures below 325 °C the system is under chemical control. The influence of diffusive processes on the kinetics of production of LaOCl was evaluated by studying the effect of the reactive gas flow rate, the mass of the sample, and the chlorine diffusion through the boundary layer surrounding the solid sample. The conversion curves were analyzed and fitted according to the Johnson−Mehl−Avrami description, and the reaction order with respect to thechlorine partial pressure was obtained by varying this partial pressure between 10 and 70 kPa. The rate equation was obtained, which includes the influence of the temperature, chlorine partial pressure, and reaction degree.