Composition of oils derived from the batch pyrolysis of tyres

A nitrogen purged static-bed batch reactor was used to pyrolyse 3 kg batches of shredded scrap tyres at temperatures between 450 and 600 degrees C. The oils were trapped in a series of condensers and the derived gases analysed off-line by packed column gas chromatography. The oil yield was found to decrease with increasing final pyrolysis temperature and the yield of product gases increased. The fuel properties of the condensed oil including, calorific values, ultimate analyses, flash point, moisture content, fluorine and chlorine contents were determined. The concentration of polycyclic aromatic hydrocarbons (PAH) and lighter aromatic hydrocarbons were determined. The results showed that the derived tyre oils had fuel properties similar to those of a light petroleum fuel oil. The influence of pyrolysis temperature showed an increase in the aromatic content of the oils with increasing temperature, with a consequent decrease in aliphatic content. The total PAH content of the oils were found to increase from 1.5 to 3.5 wt.% of the total oil as the pyrolysis temperature was increased from 450 to 600 degrees C. Biologically active compounds such as methylfluorenes, tri- and tetra-methylphenanthrenes and chrysene were identified in significant concentrations. The results of gas analysis supported a Diels-Alder mechanism of alkane dehydrogenation to alkenes, followed by cyclisation and aromatisation. Limonene was identified as a major component of the oils, representing 3.1 wt.% at 450 degrees C falling to 2.5 wt.% total oil at 600 degrees C. Significant quantities of light aromatics such as benzene, toluene, xylene and styrene were also found. (C) 1998 Elsevier Science B.V.