Catalytic pyrolysis of waste plastic from electrical and electronic equipment

Plastic waste collected from waste electrical and electronic equipment (WEEE) was pyrolysed in the presence of zeolite catalysts to produce a gasoline range aromatic oil. The plastic was from equipment containing cathode ray tubes (CRTs) and also plastic waste from refrigeration equipment. In addition, for comparison the main plastics contained in the WEEE, in the form of high impact polystyrene (HIPS) and acrylonitrile-butadiene-styrene (ABS) were also pyrolysed in the presence of the zeolite catalysts. Two zeolite catalysts; Y zeolite and ZSM-5 were used. Catalytic pyrolysis took place in a two stage fixed bed, batch reactor with the plastic pyrolysed in the first stage and the evolved pyrolysis gases catalysed in the second stage reactor. The quantity of oil produced from uncatalysed pyrolysis of plastics from CRTs and refrigerators was more than 80 wt%. The gases consisted of hydrogen, methane and C<inf>2</inf>-C<inf>4</inf> hydrocarbons. When the zeolite catalysts were introduced there was a decrease of between 5 and 10 wt% in oil yield and a corresponding increase in gas yield. The composition of the oils derived from the uncatalysed pyrolysis of WEEE plastics were mainly aromatic with high concentrations of styrene, derived from the HIPS and ABS present in the plastic waste. Addition of the zeolite ZSM-5 and Y zeolite to the pyrolysis process resulted in significant concentrations of benzene, toluene and ethylbenzene in the product oil but reduced concentrations of styrene. The oils from both thermal and catalysed pyrolysis also contained significant concentrations of polycyclic aromatic hydrocarbons for example, naphthalene, phenanthrene and pyrene.