Catalytic pyrolysis of mixed plastic wastes using commercial grade kaolin and Ukpor clay from Nigeria

The aim of this study is to convert mixed plastic waste into usable liquid fuel via pyrolysis technique using Ukpor clay as a low-cost catalyst and commercial grade kaolin. Waste plastic was catalytically degraded in a laboratory scale pyrolysis semi-batch reactor at a temperature of 400 °C, residence time of 45 min, and heating rate of 16 ˚C/min. The catalysts were characterized by XRF analysis while proximate analysis of the plastic feed carried out gave volatile materials content of 95.17 wt%, fixed carbon of 1.51 wt% and ash content of 2.6 wt%. Ukpor clay and kaolin were employed as catalysts in catalytic pyrolysis of the same feedstock for catalyst-to-plastic ratio of 1:1, 1:2, 1:3, and 1:4 and at the same operating parameters. Optimum yields were obtained at a catalyst-to-plastic ratio of 1:3 for both catalysts with a yield of 85.80, 3.58, and 10.62 wt% for Ukpor clay and 89.80, 6.33, and 3.87 wt% for kaolin for the liquid, gaseous, and solid products, respectively. The liquid products obtained for the catalytic cracking at optimum conditions were characterized for their suitability as fuel. The properties determined were density, viscosity, flash point, pour point, and calorific value. The results suggest that both catalysts produced liquid products, whose properties are comparable to conventional fuels (gasoline and diesel oil) with kaolin catalytic pyrolysis process producing higher liquid yield. GC-MS analysis found that most of the liquid oil produced a high aromatic content with some aliphatic and other hydrocarbon compounds, FTIR analysis of the liquid product from catalytic pyrolysis also shows that it contains hydrocarbons with different functional groups such as aromatics, olefins, carbonyl, amines, sulphides, and hydroxyl.