Thermal Decomposition Kinetics of 2CsBr·LaBr3·10H2O

Abstract

A novel solid compound 2CsBr·LaBr₃·10H₂O was found, separated and tested during studying the phase equilibria of the ternary system of CsBr–LaBr₃–H₂O at 298.2 K and the thermal stability of the compound was studied by thermogravimetry and differential thermogravimetry. Three weight-loss phases were observed in the heating courses from room temperature to 400 °C in the inert atmosphere, in which 2, 5, 3 of water molecules were removed from the compound 2CsBr·LaBr₃·10H₂O in turn. By Kissinger and Ozawa methods, the activation energies of thermal decomposition at three weight-loss phases were obtained as 58.5213, 210.2401 and 149.6305 kJ mol^-1, respectively. Meanwhile, reaction orders of three thermal decomposition reactions were found with the values of 0.3574, 0.4761, 0.3209, respectively. Thermal decomposition kinetic equation of 2CsBr·LaBr₃·10H₂O at three weight-loss processes could be expressed as the following forms: da/dt = 42.3473·exp(-58521.3/RT)·(1-a)[-ln(1-a)]^-1.7979 for the 1st phase, da/dt = 1.5689 × 10²⁵ · exp(-210240.1/ RT)·(1-a)[-ln(1-a)]^-1.1004 for the 2nd phase and da/dt = 2.0189 × 10¹² · exp(-149630.6/RT)·(1-a)[-ln(1-a)]^-2.1163 for the 3rd phase.