TG Studies on Chlorination Reactions of γ-Al₂O₃

Abstract

Kinetics of the reactions of γ-Al₂O₃ with COCl₂, CO+Cl₂ and CCl₄ was studied by performing anisothermal and isothermal TG measurements from room temperature up to 1123 K and at partial pressures up to 10⁵ Pa, using a Mettler semimicro recording balance coupled with a fused silica reactor designed specially for this purpose. From the anisothermal measurements performed at linear heating rate the temperature ranges of adsorption and of chemisorption and the starting temperatures of the reactions were determined. The isothermal weight loss curves could be well fitted by the first order kinetics at temperatures where chemical control was predominant and by the contracting cylinder model above these temperatures. The Langmuir-Hinshelwood rate expression could be used to describe the reaction rate vs reactive gas concentration. The apparent activation energies were calculated by the Arrhenius plots in temperature ranges where the reactions were controlled by the chemical kinetics. It is shown that the technique and the procedure developed enable to determine the characteristic kinetic parameters of the different phases of these reactions.