Thermal and catalytic pyrolysis of waste plastic heavy distillate into diesel-like product

Abstract

This study explored the catalytic upgrading of heavy distillate (HD) from plastic industries into diesel-like fuel using kaolin as a catalyst. A modified brick electric furnace was employed as a heating source for batch reactor and a central composite design response surface methodology utilized for experimentation during both thermal and catalytic pyrolysis. The results showed that kaolin significantly enhanced oil yields, achieving 73.28 wt % at 400 °C with 5 % catalyst loading and 150 min reaction time, and 70.13 wt % at 400 °C with 15 % catalyst loading and 150 min reaction time whereas, thermal pyrolysis yielded 63.63 wt % at 400 °C and 18.88 wt % at 350 °C. The catalytic process modified the functional groups, increasing paraffin and olefin yields, and shifting the carbon range towards diesel-like organics (C6-C23). The resulting diesel-like products exhibited improved properties, with distinct differences observed between those produced with and without kaolin catalyst. Without catalyst, the products had a density of 779 kg/m³, viscosity of 2.63 cSt, and calorific value of 46.62 MJ/kg and that obtained with kaolin catalyst had a density of 788 kg/m³, viscosity of 2.88 cSt, and calorific value of 47.23 MJ/kg, comparable to commercial diesel. Elemental analysis revealed increased carbon content from 77.21 wt % in HD to 83.24 wt % without catalyst and 84.83 wt % with catalyst, accompanied by decreased hydrogen, nitrogen, sulfur, and oxygen contents. The study demonstrates the potential of kaolin-catalyzed pyrolysis for converting heavy distillate into valuable diesel-like fuel. Further research on process optimization, desulfurization, and dehalogenation is recommended to improve the diesel fuel quality. Hence, this study contributes to the development of sustainable waste management and renewable energy solutions.