Batch Hydrothermal liquefaction of end-of-life plastic and oil characterization

Abstract

Finding a proper way to manage the enormous amount of waste plastic that is globally produced, is one of the main environmental challenges of our times. Among the different types of chemical recycling, Hydrothermal Liquefaction (HTL) appears as a potential method for the treatment of plastic waste mixes, for sustainable production of biocrude or chemicals with high added value. In this work hydrothermal liquefaction reactions were carried out on a polymeric residue, obtained from an industrial plastic waste collection and recycling process. The residue has a heterogeneous composition consisting not only of polymers but also paper and metals. Two batch experiments were performed in a stainless-steel Parr autoclave at 340 °C, investigating a residence times of 5 hours and the use of an alkaline catalyst (NaOH). The oils obtained from the reactions, as well as the aqueous phases, have been analysed by different analytical techniques such as: FT-IR spectroscopy, GC-MS, GC-FID, IC. The operating conditions used in this work, allowed the degradation of cellulose and polymers with reactive sites for hydrolysis such as PET, nylon and PVAc, while polyolefins (PE, PP) were not attacked. The use of a basic catalyst favoured a greater hydrolysis rate.