Catalytic Conversion of Thermal Decomposition Products of Halogen Containing Polymers Studied by Pyrolysis-GC-MS

Feedstock recycling of plastics wastes by pyrolysis is adequate for obtaining valuable oil. However, thermal decomposition products of the halogen containing components of the plastics are contaminating the pyrolysis oil. In this work, pyrolysis-gas chromatography-mass spectrometry combined with online catalytic conversion has been applied to study the activity of Na-zeolite catalysts for dehalogenation of chloro- and bromo-hydrocarbons in pyrolysis oil of poly(vinylbenzyl chloride), polychloroprene, polychlorostyrene and polybromostyrene. GC-MS analysis of the products helped to recognize catalytic reactions of halogenated alkyl, alkenyl and aromatic hydrocarbons over three sodium zeolites, two of faujasite (X and Y) and one of beta structure. It was concluded that chlorine is completely eliminated from alkyl and alkenyl chloride compounds over all the three investigated zeolites. However, chlorine and bromine substituent of aromatic rings split off only partially: 6, 15 and 17% dechlorination and 14, 31 and 29% debromination of chloro- and bromobenzenes have been observed over X, Y and β zeolite, respectively.