Chemical characterization of mixed plastic pyrolysis oils relevant for cracker reintegration by advanced two-dimensional gas chromatography

Pyrolysis oils are the crucial link between waste and chemicals in plastic recycling via pyrolysis. Oils from mixed plastic waste pyrolysis are complex mixtures of organic compounds typically containing impurities of nitrogen, oxygen, and chlorine. Therefore, their characterization is challenging. This study presents a tailored two-dimensional gas chromatography method supporting in-depth analysis of the chemical composition. It covers a boiling range from the naphtha cut to the middle distillate. These fractions represent the preferred feedstocks to be substituted by plastic pyrolysis oils in the future. The oil characterization is complemented by elemental analyses, nuclear magnetic resonance spectroscopy, and simulated distillation. The enhanced separation by two-dimensional chromatography results in significantly higher resolution than conventional one-dimensional methods. The most relevant oil compounds can be clustered, distinguished, and quantified based on compound grouping. Depending on the boiling range of the pyrolysis oils, 77 wt% to 96 wt% of the sample composition can be elucidated. Detecting main heteroatom-containing species such as benzoic acid, ε-caprolactam, acetophenone, and various aromatic nitriles provides detailed information for further pyrolysis oil utilization. ... mehrThe combination of the developed method with common analyses offers an advanced approach to evaluate the reintegration of contaminated mixed plastics oils into existing petrochemical value chains.