Catalytic upcycling of polyolefins into refinery feedstock via hydrogenolysis using commercial heterogeneous catalysts

Date

2024-1

Author

Aydoğdu, Arzum Ceren

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Plastics are ubiquitous and versatile materials manufactured in tremendous quantities to meet the needs of modern life in various industries, including healthcare, electronics, automotive, packaging, and many others. Most of these plastics are discarded inadequately for recycling due to the insufficient infrastructure for waste management, which creates not only enormously large volumes of waste plastics but also an irreversible loss in their value. Recycling methods do exist; nevertheless, they are either unable to recover the intrinsic value of plastics or generate lower-value materials via downcycling. However, if polymers that are composed of many large macromolecules could undergo a chemical transformation or so-called “upcycling” process into value-added chemicals instead of being discarded as waste or downcycled into lower-quality plastics, the potential of plastics as an untapped resource of energy-rich hydrocarbons could be unlocked, and the gap in the circular economy of plastics could be closed. In this study, the catalytic transformation of polyolefins into refinery feedstock naphtha was examined with the aim of producing precursor molecules for polyolefin production. For this purpose, the activity of four different commercial catalysts (mordenite, cat-1, cat-2, and cat-3) on polyolefin hydrogenolysis reactions was investigated. The reaction parameters like temperature, polymer/catalyst ratio, and reaction duration were investigated. The resemblance of the resulting product to naphtha was explored using several chromatography techniques. After completing catalytic activity measurements, the best-performing catalyst was identified, which achieves 55% conversion of polyethylene into oil with a remarkable selectivity of 93.9% towards saturated hydrocarbons at 400°C and under 20 bar H2 for 5 hours of reaction time. Yet, the presence of olefins in the final oil was found to be higher than that in commercial naphtha, preventing direct substitution of the oil with naphtha. The results show that novel catalyst designs that can break the C-C bonds while saturating them with H2 and blocking the formation of the aromatic components could be required.

Subject Keywords

Polyolefins, Upcycling, Hydrogenolysis, Naphtha, Commercial catalyst

URI

https://hdl.handle.net/11511/108525

Collections

Graduate School of Natural and Applied Sciences, Thesis