Valorization of Spent Plastics for Hydrocarbon Production with Improved Economic Worth and Environmental Remediation: A Pre-degradation Approach

Study’s Excerpt/Novelty This study introduces an approach to addressing Nigeria's plastic waste problem by converting discarded low-density polyethylene (LDPE) sachets into valuable liquid fuel through pyrolysis. Utilizing a modified zeolite catalyst (ZSM-5) enhanced with nickel, the research demonstrated a high yield (≈72%) of liquid products rich in alkenes, which are essential for gasoline blending and chemical processes. The innovative dissolution of LDPE in toluene before degradation not only reduces viscosity for uniform heating but also presents a scalable solution to prevent pipeline blockages, showcasing the potential for continuous operation in plastic waste conversion. Full Abstract Amidst the world's energy crisis, our society faces a growing environmental dilemma as plastic junk winds up in landfills and bodies of water, infiltrating the food chain. In Nigeria, water packaged in transparent low-density polyethylene (LDPE) sachets is widely consumed by the populace and the sachets are discarded in large quantities. Waste LDPE was subjected to pyrolysis, which involves first dissolving it in toluene and then degrading it using a modified zeolite catalyst. ZSM-5 underwent modification with the addition of nickel using the hydrothermal technique. The catalyst and pure zeolite's elemental composition, surface area, crystal structure, and morphology were examined through Energy Dispersive X-ray (EDX) analysis, Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM), respectively. The liquid products were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Gas chromatography-mass spectrometry (GC-MS). The result showed a high yield of liquid products (≈72%) rich in alkene, a valuable gasoline blending stock that can be used as a feedstock for various chemical processes. The physicochemical parameters of the oil obtained via both thermal and catalytic cracking were also determined and it was observed that the product of the catalyzed process had better properties with some of the oil-fuel characteristics obtained fitting perfectly within the range of standard fuel. Dissolving the LDPE in toluene reduced its viscosity, allowing for easy handling and uniform heating within the reactor. Furthermore, the dissolution method before degrading could help prevent pipelines from getting stuck with melted plastic feed if plastic waste conversions through cracking are scaled up to continuous operations.