Production of Oil and Char by Intermediate Pyrolysis of Scrap Tyres: Influence on Yield and Product Characteristics

Scrap tyres represent a severe environmental problem that must be solved by developing technologies allowing the processing of high quantities of this residue. This work presents the results of pyrolysis oil and pyrolytic char production by intermediate pyrolysis of rubber recovered from scrap tyres. The influence of process variables such as particle size, temperature and reaction time on the characteristics of the products obtained was analysed. Maximal yields of 52.56 and 39.50 wt% of pyrolysis oil and pyrolytic char, respectively, were obtained, under operational conditions that favoured the production of pyrolysis oil. The products obtained were a pyrolytic char with a maximal surface area of 85.16 m /g and fixed carbon content of 78.55 wt%; and pyrolysis oil with a higher heating value of 42.94 MJ/kg, real density of 0.948 g/mL, viscosity 2.29×10 Pa s and acidity between 0.39 and 1.57 mg KOH/g. The highest total aromatics (benzene, toluene, xylenes and ethylbenzene) yield in pyrolysis oil was obtained at a temperature of 466°C and volumetric gas flow of 155 NmL/min. In addition, at these conditions, the pyrolysis oil having the maximum aromatic yield showed the lowest acidity. Nevertheless, it was observed that the highest pyrolysis oil yield does not necessarily lead to a higher yield of aromatics.