Journal of Chemical and Engineering Data, Vol.54, No.3, 726-729, 2009
Solid-Liquid and Liquid-Vapor Equilibria in the Zr(Hf)Cl-4-KAlCl4 Systems: A Basis for the Extractive Distillation Separation of Zirconium and Hafnium Tetrachlorides
The relative volatility alpha(HfCl4/ZrCl4) in molten potassium chloroaluminate, KAICl(4), has been determined using equilibrium Rayleigh vaporization from mixtures containing a 36 % mass fraction of ZrCl4 + 1.4 % HfCl4. At these component concentrations and at a temperature near 450 degrees C, the ZrCl4 + HfCl4 vapor pressure over the melt is close to atmospheric pressure. According to preliminary results, alpha(HfCl4/ZrCl4) approximate to 1.29 +/- 0.04. The ZrCl4-KAlCl4 and HfCl4-KAlCl4 systems have been studied by visual thermal analysis. The results confirm that they are simple binary eutectic systems. According to our data, the eutectic temperature in the ZrCl4-KAlCl4 System is 519 K, and the eutectic is located at a ZrCl4 mole fraction of 0.08. The HfCl4-KAlCl4 system has a eutectic at an HfCl4 Mole fraction of 0.171 with a melting point of 507.5 K.