Micro-characteristics of solid–gas–liquid phase pyrolysis products of waste printed circuit board resin powder driven by multi-type spectral data

We have already carried out the research on the pyrolysis kinetics and pyrolysis process mechanism of waste circuit board resin powder. In this study, we focused on the physical and chemical properties of solid–gas–liquid phase products from the pyrolysis of resin powder. The pyrolysis process of WPCB at different heating rates was analyzed by thermogravimetric analyzer (TG), and the parameters were statistically analyzed. Scanning electron microscopy was employed to observe the micro-morphology of the pyrolytic solid products under the high-resolution demonstration conditions of 5 μm and 1 μm, mainly the combination morphology of pyrolytic carbon and glass fiber, and the combination energy spectrum analysis was used to detect the elements C, Si, Al and Ca as the main chemical components of the solid substances. In order to further understand the composition and distribution of functional groups in the pyrolysis residues, the absorption vibration peaks of pyrolysis carbon were determined by Fourier transform infrared spectroscopy (FTIR), and the attribution of different vibration peaks was interpreted. It was found that the key chemical substances were the substitutes of phenol, isopropyl phenol and bisphenol A. The chemical structure types and yield of liquid pyrolysis tar at pyrolysis temperature of 673.15 K were tested by gas chromatography–mass spectrometry (GC–MS). The major constituent of liquid-phase product was phenolic compounds, the total content of which is 74.63%. The composition of non-condensable gasses produced by WPCB under vacuum pyrolysis conditions was observed by GC–MS, mainly containing H 2 , CO 2 , CO and CH 4 . In addition, TG-FTIR was used to further observe the pyrolysis process of WPCB and to track the components of gasses escaping from the pyrolysis process, namely CO 2 , phenol and substituted phenol. However, TG-FTIR detected bromine in the gas, suggesting that HBr gas may exist. Therefore, when the pyrolysis gas is recycled as fuel gas, it is recommended to first perform the de-bromination treatment of the pyrolysis gas to avoid HBr escape.