Characterisation of Precipitates from Spent Tyre Pyrolysis Oil and Its Distillates after Accelerated Ageing

This paper reports an experimental investigation into the characteristics of the precipitates from spent tyre pyrolysis oil and its distillates after accelerated ageing. The spent tyre pyrolysis oil contains various reactive compounds, making the oil unstable and thus hindering its practical use. In this study, the raw spent tyre pyrolysis oil was obtained from an industrial scale retort. The raw pyrolysis oil was further distilled into three fractions, namely, a light off-cut, a medium fraction, and a heavy residue, using a packed-bed distillation column. The raw pyrolysis oil and the three distilled fractions were then subjected to accelerated aging at 95 °C in the presence of O2 for 16 hours. The respective precipitates formed after the ageing were collected and dried, and their characteristics were analysed using thermogravimetric analysis (TGA), proton nuclear magnetic resonance (1H-NMR), Fourier transform infrared spectroscopy (FTIR) and a gas chromatograph-mass spectrometer (GC-MS). It was found that the heavy residue fraction had the highest amount of precipitates, followed by the raw oil, medium fraction and the light off-cut, suggesting the unstable, reactive compounds were more concentrated in the heavy residue than in the two other fractions. All precipitates were heavier than their corresponding parent samples, indicating the occurrence of oxidation and/or polymerisation reactions during ageing. The precipitates had distinctively different characteristics as compared with their parent liquid samples.