Study of the reaction stages and kinetics of the europium oxide carbochlorination

Abstract

The europium oxide (Eu2O3(s)) chlorination reaction with sucrose carbon was studied by thermogravimetry between room temperature and 1223 K (950 °C). The nonisothermal thermogravimetry showed that the reaction consists of three stages, and their stoichiometries were studied. The product of the first stage was europium oxychloride, and it showed independence of the reaction kinetics with the carbon content. Subsequently, in the second stage, the EuOCl(s) was carbochlorinated with formation of EuCl3(l) and its evaporation is observed in the third stage. The analysis by Fourier transform infrared spectroscopy of gaseous species showed that the reaction at second stage occurs with the formation of CO2(g) and CO(g). Both reactants and products were analyzed by X-ray diffraction, scanning electron microscopy and wavelength-dispersive X-ray fluorescence spectroscopy. The influence of carbon content, total flow rate, sample initial mass, chlorine partial pressure, and temperature were evaluated. The second stage kinetics was analyzed, which showed an anomalous behavior caused by generation of chlorine radicals during interaction of Cl2(g) and carbon. It was found that the reaction rate at 933 K (660 °C) was proportional to a potential function of the chlorine partial pressure whose exponent is 0.56. The conversion curves were analyzed with the Avrami-Erofeev model and it was obtained an activation energy of 154 ± 5 kJ mol–1.