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

摘要

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 froman analysis of TGanalysis data using an isoconversional method and a master-plot method. Primary thermal dissociation of SO_3H~+ 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 ℃ 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 SO_3H~+ was described by a phase boundary reaction (contracting volume, g(a) = 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.