(57f) Hydrothermal Process of the Ocean-Bound Plastic Waste into Value-Added Aromatic Chemicals

Plastics are robust and versatile and thus have wide applications in several fields. However, the improper disposal of plastics, which are persistence in the environment, has made plastics waste a global issue. Particularly, recovering the plastic waste from the ocean is very costly. Conventional plastic recycling methods (e.g., mechanical recycling) are challenged by their inferior efficiency, possible emissions of hazardous compounds, and little tolerance of contaminants. Currently, most mechanically recycled plastics are downcycled. To address this problem, in this study, an hydrothermal processes (HTP) was developed to convert the ocean-bound plastic waste (OPW), which are generally wet and has contaminants, into useful products under supercritical water. Based on the degradation temperature of the OPW feedstock (425℃), HTP tests were carried out at 425-475℃ and 23MPa with reaction times of 0.5−6 h. It was found that above 78 wt% of OPW could be converted into oil products by the increased temperature (≥450℃) or elevated reaction times (≥2h). Different amounts of polypropylene mixed with OPW were found to reduce the severity of reaction parameters required for aromatics production. The fuel fractions of the oil phase within different boiling ranges were determined by TGA analysis. Over 60% of the oil can be used as naphtha (with the boiling point range of 25℃-200℃). The chemical composition of the oil products will be analyzed by Fourier-transform infrared spectroscopy (FT-IR) and gas chromatography–mass spectrometry (GC-MS). Integrated with elemental analysis of the oil products, a reaction mechanism will be proposed. Results from this study would contribute to the development of an efficient advanced recycling method for ocean plastic waste.