Polypropylene Decomposition in Petroleum-based Solvents over Beta Zeolite toward Chemical Recycling

For the chemical recycling of waste plastics into chemical feedstocks, catalytic decomposition of polypropylene (PP) was conducted in hydrocarbon solvents over zeolite beta catalyst at 400 °C. Light Gas Oil (LGO) and Light Cycle Oil (LCO) from an oil refinery were used as solvents. Both LGO and LCO contained not only hydrocarbon but also basic compounds. The PP conversion significantly increased from 50.9 to 97.0 %, when PP was decomposed in LGO after removing basic compounds. However, the PP conversion in LCO remained low even after removing basic compounds. As LCO had a higher aromatic content compared to LGO, to assess the effect of aromatics in solvents, decomposition tests were conducted in model solvents, n-hexadecane, 1-methyl naphthalene, and tetralin. The results indicated that aromatics in solvents negatively influenced the PP conversion. Consequently, removing basic compounds was crucial when using such oils as solvents, and solvents with high contents of aliphatic, such as LGO, are suitable for the PP decomposition.