Catalytic Pyrolysis of Post-Consumer Polypropylene over a Regenerated FCC Catalyst Under Moderate Vacuum: Gasoline- and Diesel-Range Fuels with a Low Aromatic Content

Post-consumer polypropylene (PP) waste is a growing environmental liability in developing economies with limited recycling infrastructure. This study presents an integrated kinetic-to-reactor approach for the catalytic pyrolysis of three compositionally distinct post-consumer PP streams, combining a moderate vacuum (0.45 bar absolute) with a regenerated fluid catalytic cracking (FCC) catalyst to produce diesel-range fuel while valorising two industrial waste streams. The activation energies derived from thermogravimetric analysis (β = 30 °C min−1, N2) using the Coats–Redfern method were 178.3 kJ mol−1 for the near-pure isotactic PP feedstock, consistent with random chain scission, and 209.2 and 351.9 kJ mol−1 for the UV-stabilised and PP/HDPE streams, respectively, reflecting the feedstock composition; the DTG profile informed the selection of 450 °C as the reactor set point. At the best condition within the studied domain (Cat/PP = 0.03 g g−1, 2 h, 450 °C), the regenerated FCC catalyst achieved 75.10 wt% liquid yield, a 50% improvement over thermal pyrolysis, with a low aromatic content of 1.69 area%,attributed primarily to the moderate acidity of the regenerated catalyst, versus the 10–25 wt% typical of atmospheric zeolitic pyrolysis. Vacuum distillation yielded a diesel fraction that mainly complies with the ASTM D975 Grade 2-D S15 parameters (cetane index 68.92, sulphur 14.1 ppm) without hydrotreatment, demonstrating a technically viable waste-to-fuel pathway where post-consumer polyolefins and refinery FCC by-products are simultaneously abundant.