Generation behavior of tar from ABS, PC, and PE during pyrolysis and steam gasification by mass spectrometry

Gasification is attracting attention as a method of chemically recycling waste plastics. However, gasification generates tar, which consists primarily of polycyclic aromatic hydrocarbons (PAHs), as a byproduct. Our study aims to elucidate the steam gasification behavior of tars from acrylonitrile butadiene styrene (ABS), polycarbonate (PC), and polyethylene (PE) plastics in a batch furnace using mass spectrometry. The tar fraction varies depending on the type of plastic. The plastics tars from ABS, PC, and PE include mainly nitrogen-containing hetero-PAHs, oxygen-containing hetero-PAHs, and PAHs, respectively, reflecting their chemical structures. The formation of PAHs can be explained by the incorporation of C2 or/and C2H2 units, i.e., the 24/26 rule. The tars are found to be degraded by the addition of steam as the reaction temperature increases. Principal component analysis (PCA) indicates that the first principal component of these data, which accounts for 72% of the variance, can be attributed to the differences between the three types of plastics. A combination of time-of-flight mass spectrometry analysis and PCA enables successful discrimination of the tar components generated under gasification conditions.