The effect of slow pyrolysis on the conversion of packaging waste plastics (PE and PP) into fuel

Packaging plastic waste consisting of low and high-density polyethylene and polypropylene were pyrolyzed in a lab scale semi-batch reactor at a very slow dynamic condition (1 °C min^-1). Gaseous and liquid products were collected at regular intervals starting from their inception during the degradation process. Detailed analysis was carried out to estimate the properties of plastic derive oil (PDO) obtained at different stages of the pyrolysis process. The pyrolysis temperature has a significant effect on the product compositions. The paraffin concentration increases with increasing pyrolysis temperatures. On the other hand, increased pyrolysis temperature decreases olefin concentration. Olefinic content in the PDO was found comparatively higher when PP was in the feed. Presence of polypropylene in the feed caused the production of PDOs with branch-chain hydrocarbon components with high isoparaffin index and research octane number (RON). The PDOs obtained (for all feed studied) at the early stages of the degradation process have light hydrocarbon liquid fractions belonging to light and middle distillates of petroleum (C₆ - C₂₀). The yield of both light and middle fractions decreased as the pyrolysis reactor temperature reached the maximum value (∼400 °C). Gas evolution pattern depends on both pyrolysis temperature and the feed composition. Propylene was found more dominating among other major components of gases like methane, ethane, ethylene, propane, n-butane, 1-butene, isobutylene and n-pentane etc.