Polypropylene to transportation fuel grade hydrocarbons over γ-alumina catalyst

•Polypropylene is converted to transportation-grade fuels in high yields (88 wt.%).•Response surface methodology was employed to optimize the process.•Mild conditions were employed and achieved high activity.•Catalyst was reusable and stable in subsequent recycles. Catalytic upgrading of plastics to valuable fuels and chemicals is an attractive route to valorize waste plastics. Herein, catalytic pyrolysis of polypropylene was performed over γ-Al2O3 as a heterogeneous catalyst to produce fuel-grade hydrocarbons. The use of an inexpensive γ-Al2O3 catalyst and mild reaction conditions led to high liquid yield selectively in gasoline-range hydrocarbons which stands out from most of the work reported in the literature for polypropylene pyrolysis. The reaction conditions of pyrolysis were optimized by the Box-Behnken Design approach utilizing the response surface methodology. The highest liquid yield of 88.1 wt.% was obtained at 470 °C temperature, with 2 wt.% of catalysts and 5 h reaction time. The amount of solid carbon was insignificant (0.7 wt.%) and the gas yield was 11.2 wt.%. The γ-Al2O3 showed high efficiency and stability for converting polypropylene to liquid fuels. The catalyst was highly stable, reusable, and showed similar catalytic activity for 3 recycles. These features and the highly selective conversion of PP to gasoline range fuels are crucial for large-scale applications. The GC–MS analysis revealed that the liquid fuel produced mostly contained C8 to C15 hydrocarbons encompassing mostly gasoline and a small fraction of diesel fuel and higher hydrocarbons. The GC–MS data was also supported by SimDist analysis, which exhibited the boiling point ranging from 100 °C to 260 °C for the liquid fuel product. The reaction temperature and time had a significant impact on the liquid yield. The higher temperature favored the formation of the gaseous product of C1-C3 hydrocarbons. The NMR analysis showed that the liquid products mostly contained the highest amount of paraffins followed by olefins and a small fraction of aromatics. The presence of mild acidity in the γ-Al2O3 catalyst and optimum reaction condition provides favorable conditions to produce the highest yield of transportation fuel grade hydrocarbons without over-cracking into gases. [Display omitted]