Insight into co-pyrolysis interactions of Pingshuo coal and high-density polyethylene via in-situ Py-TOF-MS and EPR

Abstract

In-situ detection on primary volatiles interactions and stable radical evolution behaviors during co-pyrolysis of Pingshuo coal (PC) and high-density polyethylene (HDPE) were systematically investigated via a novel in-situ pyrolysis time-of-flight mass spectrometry (in-situ Py-TOF-MS) combined with electron paramagnetic resonance (EPR) spectroscopy. TG results demonstrated that the mixing ratio 7:3 for PC/HDPE has the better positive interaction performances. Accordingly, in-situ Py-TOF-MS results revealed that more short-chain alkenes such as butene and heptadiene are formed in co-pyrolysis, and the addition of HDPE remarkably enhances the transfer of hydrogen (H) to react with the phenoxy group from PC to form diphenol. According to the EPR analysis, HDPE has a remarkable effect on the stable radical concentration (Ng) in PC pyrolysis residue, especially for oxygen (O)-centered and C-centered radicals. Meanwhile, higher temperature is favorable to the generation of O-centered radicals in PC/HDPE (7:3) pyrolysis residue, its radical concentration increases from 3.42 × 1018 to 20.85 × 1018 spins/g. Furthermore, the peak of CO bond exists at a higher temperature, which is consistent with the changes of O-centered radical concentration, and this result can provide effective supplements for understanding the stable radical interactions.