Fluidised bed pyrolysis and catalytic pyrolysis of scrap tyres.

Pyrolysis of scrap tyres was undertaken in a semi-continuous fluidised bed reactor in relation to the temperature of the fluidised bed. Subsequently, a fixed bed of Zeolite catalyst was placed in the freeboard of the reactor. The catalyst temperature was held constant at 500 degrees C and the influence of the temperature of the fluidised bed over the same temperature range as the uncatalysed pyrolysis examined. Two Zeolite catalysts were examined, a Y-type Zeolite catalyst and Zeolite ZSM-5 catalyst of differing pore size and surface activity. The main aim of the work was to examine the production of certain single ring aromatic compounds in the derived pyrolysis oil which are known to be of commercial value. The oils were therefore analysed in detail to determine the concentration of benzene, toluene, xylenes and limonene. In addition, detailed analyses of the derived gases under pyrolysis and catalytic pyrolysis conditions were determined. The influence of the temperature of pyrolysis was to increase the yield of benzene, toluene and xylenes but decrease the yield of limonene. In the presence of the catalyst, the yield of oil was reduced with a consequent increase in the gas yield. Benzene, toluene and xylenes present in the oils showed a significant increase in the presence of both of the catalysts. The two catalysts used, although of differing surface acidities and selective pore sizes, produced similar concentrations of benzene, toluene, xylene and limonene.