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Pyrolysis of scrap tyres is a promising technology to recover valuable materials such as pyrolysis liquids, carbon black and steel. Pyrolysis liquids are complex mixtures of organic compounds and may represent a valuable source for chemicals. And because pyrolysis liquids are complex mixtures, high resolution analytical methods are required to accurately characterize these liquids. In this study comprehensive gas chromatography mass spectrometry (GC×GC-MS) using a reversed column setup (polar×apolar) was used for the analysis of a pyrolysis liquid. The tyre pyrolysis liquid analyzed was obtained from a process which places whole tyres onto molten zinc (460–480 °C) providing direct heat transfer and hence rapid pyrolysis.
The results show, that the pyrolysis liquid is a complex mixture of acyclic and cyclic, aliphatic, unsaturated and aromatic hydrocarbons and several heteroatomic compounds. Compared to a normal column setup (apolar×polar), the reversed column setup separates structurally similar acyclic and cyclic hydrocarbon compounds with different degree of unsaturation better. A quantification was performed for a set of 40 compounds. A qualitative and quantitative evaluation of the compounds found, that the composition of the pyrolysis liquid is typical for tyre pyrolysis liquids. Nevertheless, comparably high amounts of limonene of 6.6 % (w/w) and low amounts of monocyclic aromatic compounds were found. This is attributed to the very high heating rate of this process due to the direct heat contact of the tyres with molten zinc.