Investigation of the Pyrolytic Degradation of Ion Exchange Resins by Means of Foil Pulse Pyrolysis Coupled with Gas Chromatography/Mass Spectrometry

Cationic (LEWATIT S100) and anionic ion exchangers (LEWATIT M500MB) were thermally decomposed in amounts of 15-60 μg in a foil pulse pyrolyzer. The gaseous products were gas-chromatographically separated and identified by mass spectrometry. Cationic resins release mainly sulfur dioxide and benzene at temperatures up to 500°C. At higher temperatures, degradation products like ethylbenzene, styrene, hydrogen sulfide, benzene, and toluene are increasingly observed. Their ratio strongly depends on the applied temperatures. After fractionated pyrolysis of a single sample with rising temperatures, mainly benzene, hydrogen sulfide, and carbon disulfide are produced at 1000°C, leaving behind a residue of pyrolysis coke. Anionic resins generate mainly trimethylamine and methyl chloride up to 400°C. With rising temperatures, the formation of styrene, p-methylstyrene, and p-ethylstyrene dominates. Pyrolysis of anionic resins ends at about 900°C without leaving behind significant amounts of residue. Kinetic data for several of the observed degradation reactions were calculated.