Influence of catalyst bed temperature and properties of zeolite catalysts on pyrolysis-catalysis of a simulated mixed plastics sample for the production of upgraded fuels and chemicals

The pyrolysis-catalysis of a simulated mixture of plastics representing the plastic mixture found in municipal solid waste has been carried out to determine the influence of process conditions on the production of upgraded fuel oils and chemicals and gases. The catalysts used were spent zeolite from a fluid catalytic cracker (FCC), Y-zeolite and ZSM-5 zeolite. The addition of a catalyst to the process produced a marked increase in gas yield, with more gas (mainly C1–C4 hydrocarbons) being produced as the temperature of the catalyst was raised from 500 °C to 600 °C. The Si/Al ratio of the catalysts influenced the composition of other gases with the more basic catalysts producing more CO and the strongly acidic catalyst producing more H2. The yield of product oil decreased with the addition of the catalysts, but the oil was of significantly lower molecular weight range, containing a product slate of premium fuel range C5–C15 hydrocarbons. In addition, the content of aromatic compounds in the product oil was increased; for example, benzene and toluene accounted for more than 90% of the aromatic content of the oil from the strongly acidic Y-zeolite catalysts. A reaction scheme is proposed for the production of single-ring aromatic compounds via pyrolysis-catalysis of plastics.