Study on thermal decomposition and oxidation kinetics of cation exchange resins using non-isothermal TG analysis

Abstract

Kinetics of two successive thermal decomposition reaction steps of cationic ion exchange resins and oxidation of the first thermal decomposition residue were investigated using a non-isothermal thermogravimetric analysis. Reaction mechanisms and kinetic parameters for three different reaction steps, which were identified from a FTIR gas analysis, were established from an analysis of TG analysis data using an isoconversional method and a master-plot method. Primary thermal dissociation of SO3H+ from divinylbenzene copolymer was well described by an Avrami–Erofeev type reaction (n = 2, g(α) = [−ln(1 − α)]1/2]), and its activation energy was determined to be 46.8 ± 2.8 kJ mol−1. Thermal decomposition of remaining polymeric materials at temperatures above 400 °C was described by one-dimensional diffusion (g(α) = α 2), and its activation energy was determined to be 49.1 ± 3.1 kJ mol−1. The oxidation of remaining polymeric materials after thermal dissociation of SO3H+ was described by a phase boundary reaction (contracting volume, g(α) = 1−(1 − α)1/3). The activation energy and the order of oxygen power dependency were determined to be 101.3 ± 13.4 and 1.05 ± 0.17 kJ mol−1, respectively.