Insight into co-pyrolysis interaction of Pingshuo coal and low-density polyethylene under varied mixing configurations via in-situ Py-TOF-MS

Abstract

The real-time detection of volatiles is crucial for exploring co-pyrolysis mechanisms. In this study, the co-pyrolysis interaction mechanism of Pingshuo coal (PC) and low-density polyethylene (LDPE) with three varied mixing configurations was explored based on the product distribution and stable radicals in char by using in-situ pyrolysis time-of-flight mass spectrometry with vacuum ultraviolet photoionization as well as electron paramagnetic resonance. Total ion currents results show that mixing configurations have an obvious impact on the release of volatiles. In the coal-LDPE test, the volatiles from coal promotes the cracking of long-chain branches in LDPE, resulting in high alkenes content. Meanwhile, the LDPE melts delay the release of coal volatiles causing a higher peak temperature of 478 °C. As for the LDPE-coal configuration, the LDPE volatiles has a better hydrogen-donor effect, which can interact with volatiles and char from coal pyrolysis to facilitate the formation of aromatics and phenols. Comparatively, coal/LDPE configuration prompts the molten LDPE to coat coal particles and exhibits poor synergies between coal and LDPE. In addition, LDPE-coal char has higher spin concentrations of C-, and O-centered radicals, indicating that the released ·H radicals from LDPE pyrolysis can well interact with char and unreleased volatiles in coal.