Plastic waste pyrolysis and its integration into steam cracking: from model systems to real waste

The growing accumulation of plastic waste represents a major environmental challenge, as conventional recycling routes are limited by the heterogeneity of waste streams and result in inefficient material recovery. Among advanced recycling technologies, pyrolysis offers a promising pathway to convert mixed plastic waste into liquid hydrocarbons that may partially replace fossil naphtha in petrochemical processes. This doctoral research evaluates the feasibility of integrating plastic waste pyrolysis into steam cracking for light olefin production, contributing to the closure of the plastic carbon loop. The thesis is structured to address the complexity of plastic waste and its potential valorization. The first part contextualizes the study, reviewing market trends, regulatory frameworks, and the composition of mixed post-consumer plastics, and introduces the fundamentals of pyrolysis, including reactor configurations, operating conditions, and product characteristics relevant for downstream processing. Subsequent chapters focus on different classes of plastics, including halogenated and oxygenated polymers, and examine their behavior during pyrolysis. The approach combines experimental studies on model systems and real waste mixtures with chemical reasoning to evaluate how feed characteristics influence oil composition and suitability for steam cracking. The final part employs multivariate statistical analysis and predictive modeling to correlate feedstock properties with steam cracking performance, specifically evaluating the co-feeding of pyrolysis oils with fossil naphtha and their impact on light olefin yields and product distribution.