Thermochemical recycling of plastic via steam cracking into light olefins will become the main route for reduction of the escalating plastic waste crisis in the coming decade. A thorough understanding of the chemistry of this unconventional feedstock in a steam cracking reactor is first necessary to enable a safe and economically viable operation. The feedstock, plastic pyrolysis oil, contains a mix of hydrocarbons and heteroatomic compounds containing O, N, S, Cl and Br. These compounds originate from organic residues, additives and contamination with PVC among others. Aside from oxygen compounds, the decomposition of these heteroatomic compounds is not well known, especially when they react in the presence of a complex hydrocarbon matrix. In this project, a comprehensive kinetic model will be developed to unravel the chemistry of plastic pyrolysis oil and, in the longer term, enable process and real-time optimization and feedstock selection. A detailed compositional analysis of the plastic waste pyrolysis oil will be the basis for kinetic modeling work. Models for heteroatomic model compounds will be constructed based on parameters obtained from ab initio calculations. A comprehensive kinetic model will be developed based on these model compounds and well-founded hypotheses for model size reduction. Finally, the complete model will be validated with experimental studies. This will result in optimization of thermochemical plastic recycling towards industrial application.