Gasoline and diesel-like fuel production by continuous catalytic pyrolysis of waste polyethylene and polypropylene mixtures over USY zeolite

Catalytic degradation of polypropylene (PP), polyethylene (PE) and their mixtures with different proportions (20: 80, 50: 50, and 80: 20) using USY zeolite, was studied in a continuous pilot plant at 500 degrees C, with a plastic/catalyst ratio of 10:1. The liquid fraction derived from the catalytic pyrolysis of PP and that of PE was dominated by a (C-5-C-7) hydrocarbons fraction, while the gaseous products for both materials were dominated by C-3 and C-4. Based on the Gas chromatography analysis and the distillation curves, no synergetic effect was observed for different mixture compositions. As pyrolysis products of PP and PE cover a wide range of hydrocarbons, a separation into different fractions was suggested before using them as fuels. The separation temperatures were optimized and it was found that 160 degrees C is the temperature at which the boiling point distribution and physical properties of light fraction of both PP and PE products can be compatible with gasoline fuel norms, and 220 degrees C is the temperature at which heavy fractions are compatible with diesel fuel norms. Since there is no interaction between plastics during reaction, the oil derivate from a 50%-50% mixture of PP-PE has been separated at the same temperatures and its characteristics lie between that of PP and PE. Despite that the obtained gasoline-like fraction, which represents 49% of the total oil of the 50%-50% mixture of PP-PE has a very low content in aromatics, it presents a relatively high octane number (RON = 89.8). While the diesel-like fraction which represents 20% of the total oil has a cetane number of 45.1. Finally, from 1 kg of PP for example, having an energy content of 46.4 MJ, 34.3 MJ of liquid and 8.8 MJ of gas were produced. The gasoline like phase has an energy content of 18 MJ, the intermediate phase possesses an energetic content of 10.7 MJ while the diesel-like phase having an energy content of 6.7 MJ, could generate an electrical energy of 0.53 kWh.