Study on the Oxidizing Reaction of CaCl₂in the Presence of SiO₂during Heating in Air and Water Vapor

Abstract

The several experiments were made on the oxidation of CaCl₂mixed with SiO₂which is considered to be one of the basic reaction. The pellets of CaCl₂mixed with various amount of SiO₂were oxidized using the air or water vapor in the temperature range of 650°C-1, 100°C, and the rate and mechanism of reaction were studied by the continuous analysis of Cl₂or HCl gas produced during the experimental run.
We found that the oxidizing reaction begin at 550°C in the presence of water vaporand 680°C in air, and the rate of reaction was controlled by the chemical reaction. However, the rate process was affected by the amount of mixed CaCl₂at the temperature above m. p.of CaCl₂, and the rate of reaction was controlled by diffusion in the presence of large amount of CaCl₂.
The activation energy of reaction was about 12.9kcal in air and about 8.8kcal in water vapor for liquid CaCl₂ (about 19.5kcal for solid state). The oxidizing reaction was accelerated about 5 times in the presence of water vapor than the air under the same condition.
The rate was found to be directly proportional to the oxygen and water vapor pressure over the chemically controlled to the 3/2nd power of the gas pressure over the diffusion controlled. Throughout these studies, the compound of CaO·SiO₂was formed, and CaCl₂was discussed to act as the mineralizer for the formation of compound.