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Determination of olefins in pyrolysis oils from waste plastics and tires is crucial for optimizing the pyrolysis process and especially for the further advanced valorization of these oils in terms of the circular economy. Identifying olefins, even using high-resolution techniques like GC×GC, is challenging without TOF-MS, which allows modification of the ionization step. Currently, the only method for determining olefins in plastic pyrolysis oils is GC-VUV, recently standardized as ASTM D8519. However, TOF-MS and VUV are not affordable instruments for many research teams working on plastics recycling. This paper introduces a simple method for the selective micro-scale adsorption of olefins over AgNO3/SiO2, followed by the GC×GC-FID analysis. Olefins are determined indirectly from the loss of chromatographic area in respective hydrocarbon groups before and after removal. Only 50 μL sample and 15 min of sample separation are needed. Our method was extensively validated and provides a reliable determination of olefin content in a wide range of pyrolysis oils from plastics and tires and their products after mild hydrotreatment. It is affordable to all researchers and industrial companies working on plastics recycling by thermochemical processes as it does not require an MS detector. 

The conversion of waste plastics and tires via pyrolysis to pyrolysis oil represents one of the most promising ways of chemical recycling. Determining aromatics in pyrolysis oils from these feedstocks is crucial for their utilization as both petrochemicals and fuels. In this study, we compared three standard methods commonly available in refinery laboratories (ASTM D1319 − FIA, EN12916 − HPLC-RI, ASTM D8396 − GC × GC-FID) for analyzing aromatic content across a wide range of waste plastic pyrolysis oils, their middle distillate fractions, and hydrotreated products. Using model compounds, we explained most of the observed differences in aromatic content determined by these methods. HPLC-RI and FIA resulted in significant errors. For instance, the FIA reports some dienes and heterocompounds as aromatics. The results from HPLC-RI showed that monoaromatics are overestimated, while polyaromatics are underestimated. Among the tested methods, GC × GC-FID provided the most reliable results.