Sublimation of ZrCl4 is important for the production of nuclear grade metallic Zr in Kroll's process. The sublimation kinetics of ZrCl 4 was investigated by thermogravimetric analysis under both isothermal and non-isothermal conditions. The sublimation rate of ZrCl 4 increased with increasing temperature under isothermal conditions. ZrCl4 sublimation was confirmed to be a zero-order process under isothermal conditions, whereas it was first-order kinetics under non-isothermal conditions. The activation energy of ZrCl4 sublimation under isothermal conditions was 21.7 kJ mol-1. The activation energy for non-isothermal sublimation was 101.4 kJ mol-1 and 108.1 kJ mol -1 with the Kissinger method and Flynn-Wall-Ozawa method, respectively. These non-isothermal activation energies were very close to the heat of sublimation (103.3 kJ mol-1). Sublimation occurs by two elementary steps: surface reaction and desorption. Therefore, the overall activation energy of ZrCl4 sublimation is 104.8 (±3.4) kJ mol-1. The activation energy of the surface reaction and desorption steps are proposed to be 83.1 kJ mol-1 and 21.7 kJ mol-1, respectively.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics