Enhancing properties of bio-oil produced from plastic waste: A case study utilized plastic waste from Dar-es-Salaam dump sites

Abstract

This study investigated the potential of producing and upgrading bio-oil from plastic waste through a catalytic pyrolysis process. Plastic waste samples composed of polystyrene, polyethylene, and low-density polyethylene, shredded to sizes of 1.5–2.5 mm and blended in a ratio of 50/25/25, respectively, were pyrolyzed in a fluidized bed reactor at optimal conditions of 560–650 °C, a heating rate of 15 °C/min, and N2 gas flow rate of 100 ml/min in the presence of zeolite catalysts. The produced bio-oil was treated with fossil diesel, calcium hydroxide, and sodium sulfate to enhance its properties. The results showed that bio-oil production was increased to 65 wt. %, while char was reduced to 3.5 wt. %. Treatment with 20 wt. % diesel reduced bio-oil kinematic viscosity by 58% and improved stability from 20% to 50%. The addition of 16 g calcium hydroxide reduced the bio-oil acidity by 51% from a pH of 3.2–4.85. Furthermore, the bio-oil moisture content was reduced from 10 to 5.2 wt. % through the addition of 10 g of sodium sulfate, while the lower heating value was improved to 39.0 MJ/kg. Therefore, the catalytic pyrolysis of plastic waste in a fluidized bed reactor, and the various treatments performed on the generated bio-oil proved to be an effective technique to enhance the economic value of plastic waste and its environmental management at large.