Comparison of Antioxidants to Increase the Oxidation Stability of Pyrolysis Oils of Three Plastics Using Iodine Value

Abstract

Pyrolysis is an excellent method for recovering mixed and contaminated plastics that are no longer recyclable. Special attention must be paid to the stability of the fuel to avoid the formation of undesirable products. This can be achieved by additives such as antioxidants. In this study, high-density polyethylene, polypropylene, and polystyrene plastic waste are slowly pyrolyzed to a maximum of 470 degrees Celsius. A gasoline fraction (0–190 °C) and a diesel fraction (190–320 °C) are then obtained from these. Three antioxidants are added to these fractions: pyrocatechol, phenol, and freshly produced algal pyrolysis oil; the latter is described in the literature as containing particularly high levels of antioxidants. The oxidation stability of these mixtures and the change in the iodine number over time are measured using a newer method than the commonly used method of Wijs. Phenol improves the oxidation stability best, followed successively by algae pyrolysis oil and pyrocatechol. The oxidation stability of the gasoline fraction of the polypropylene pyrolysis oil with phenol is 49% higher than that of the same fraction without antioxidants.