Thermodynamics and kinetics of the preparation of anhydrous yttrium chloride

The thermodynamic and kinetic analysis of the preparation of yttrium chloride by ammonium chloride and yttrium oxide were performed. The preparation process was divided into chlorination (493 K–573 K) and decomposition (> 717 K) stages, leading to the derivation of corresponding thermodynamic results and kinetic models. The thermodynamic calculation showed that 3NH4Cl·YCl3 was formed at 497 K–573 K via solid–solid reaction. Then, 3NH4Cl·YCl3 decomposed directly into anhydrous YCl3 at above 740 K. The kinetics of the chlorination process was consistent with the solid–solid reaction model controlled by phase boundary reaction, with the activation energy being 76.93 ± 3.87 kJ/mol. The decomposition of 3NH4Cl·YCl3 fitted well with the solid decomposition model with phase boundary reaction as the control step. The activation energy of the decomposition process was 28.43 ± 4.49 kJ/mol. The apparent rate equations for the chlorination process and the decomposition process were developed:Chlorination process: dα/dt=9.7⋅107⋅exp⁡(−76.93/RT)⋅(1−α)0.6Decomposition process: dα/dt=528⋅exp⁡(−28.43/RT)⋅(1−α)0.5