Enhancement of light hydrocarbon production from polypropylene waste by HZSM-11-catalyzed pyrolysis

Abstract

Herein, a mixture of real polypropylene (PP) waste was pyrolyzed with a HZSM-11 catalyst as a potential method to recover light hydrocarbons (C _≤ 12), the potential feedstock for value-added chemicals and fuels, from polyolefin plastic waste. Using the HZSM-11 in the PP waste mixture pyrolysis noticeably improved the yield of gas pyrolysate and oil in compensation for the yield of wax (i.e. hydrocarbons of C _> 20) and solid residue particularly at a higher temperature. In addition, the selectivity of C₃–C₁₂ in the PP-waste mixture-derived pyrolysate was markedly increased by the HZSM-11. The highest yield of light hydrocarbons was ≈40 wt% (per mass of the feedstock) achieved at 700 °C with the HZSM-11 catalyst. Despite 7.9 wt% coke deposition on the HZSM-11 after its use in the pyrolysis of the PP waste mixture, the catalyst could be reusable for at least three times after regeneration. The experimental results demonstrate that HZSM-11 has the potential for being a promising catalyst to valorize polyolefin waste into value-added chemicals.