Gasoline like fuel from plastic waste pyrolysis and hydrotreatment

Abstract

Recycling of plastic waste is desirable to lower environmental pollution and fulfil the requirements of circular economy. Energetic utilization is another possibility, however, municipal solid waste containing plastics is usually combusted to generate heat and electricity. An attractive way of dealing with plastic waste is pyrolysis, which has the potential of producing liquid hydrocarbons suitable as a transportation fuel. The pyrolysis results of three plastics produced in the largest amount globally, namely polyethylene, polypropylene and polystyrene as well as their mixtures are presented. The experiments were performed in a laboratory scale batch reactor. The pyrolysis oils were further processed by distillation to provide gasoline and diesel like (distillation cuts at 210 and 350 °C) hydrocarbons. The gasoline fractions were analysed by GC-MS and the composition was compared with the EU gasoline standard. It was found that the oils from PE, PP and PS contain compounds present in standard gasoline. Mixing PS with PE and PP before the pyrolysis, or the oils afterward produces much closer results to standard requirements as PS pyrolysis generates mostly aromatic content. As standard maximizes the olefin content of gasoline to 18 Vol%, hydrogenation was also performed using Pd based catalyst. The hydrogenation process significantly reduced the number of double bonds resulting in low olefin content. Results show that the pyrolysis of plastic waste mixtures containing PE, PP and PS is a viable method to produce pyrolysis oil suitable for gasoline-like fuel extraction and further hydrogenation of the product can provide gasoline fuels with low olefin content.