Thermodynamics and kinetics of the thermal decomposition of cupric chloride in its hydrolysis reaction

The hydrolysis of copper(II) chloride is the water splitting process in the copper–chlorine thermochemical hydrogen production cycle. In this paper, a simultaneous differential scanning calorimetry and thermogravimetric analysis (DSC/TG) technique is used to determine the transitional temperature and kinetics of the thermal decomposition of CuCl2. Thermodynamic analysis is performed on the decomposition reaction for a comparison with the thermogravimetric analysis results. The CuCl2 decomposition temperature obtained from thermogravimetric experiments is found to be higher than that predicted from the thermodynamic analysis. This broadens the available operating temperature range of the CuCl2 hydrolysis step for the Cu–Cl cycle. It is also found that the decomposition product CuCl may completely evaporate if the temperature is higher than its melting point, so the CuCl2 hydrolysis reaction should be operated below the melting point of CuCl (430 °C) to avoid the undesirable CuCl and Cl2 byproducts. A preliminary correlation is proposed in this paper for the decomposition kinetics in terms of the extent of converting CuCl2 to CuCl and Cl2.