Термодинамический анализ хлорирования оксида алюминия

Abstract

Thermodynamic analysis of aluminum oxide chlorination is of theoretical and practical interest and is performed for the main possible reactions of interaction with chlorine. The process is possible only in the direction of decreasing (decreasing) the Gibbs energy (∆G). The condition ∆G0 determines the principal possibility of carrying out the process under specified conditions and is determined only by the initial and final state of the system. The calculated values of the Gibbs energy and the equilibrium constant in the temperature range 400 – 1000 K show that in the presence of a reducing agent, the equilibrium of reactions is shifted towards the formation of aluminum chloride. It was found that the changes in the Gibbs energy of chlorination reactions of polymorphic modifications of Al2O3 increases in the series: γ-Al2O3, Al2O3 am., δ-Al2O3, α-Al2O3. It is possible to effectively assess the basic laws of obtaining anhydrous aluminum chloride in the reacting system by evaluating the change in the ratio of the initial components. Thermodynamic analysis of Al – O – C – Cl and Al – O – C – Cl – Si – Na systems with different component ratios was performed. The latter system is a rough alumina containing sodium aluminosilicate. It is shown that the 100 % yield of the target products with the full use of chlorine corresponds to the stoichiometry of their chemical interaction. The possibility of selective chlorination of Al2O3 and SiCl4 has been determined. As calculations have shown, sodium oxide is completely converted into chloride, which makes it possible to use the residue from chlorination to obtain aluminum-silicon alloys without sodium impurities.