Pyrolysis characteristics of waste printed circuit boards and distribution pattern of their valuable liquid products

Abstract

Pyrolysis is a promising technology to treat waste printed circuit boards (WPCBs) with significant advantages of full source utilization, high separation efficiency and scarce pollutant emissions. In this work, TG and DTG analyses were performed to determine pyrolysis characteristics. The kinetic analysis adopting the Starink Kissinger-Akahira-Sunose (SKAS) model was conducted to confirm the apparent activation energy (E_α). Pyrolysis products were collected using a lab-scale pyrolyzer. GC-MS analysis coupled with MS-DIAL data processing was applied to clarify the distribution pattern of valuable liquid products. The results indicated that the main thermal decomposition of WPCBs occurred within the temperature range of 157–664 °C, with E_α ranging from 80.70 to 279.46 kJ/mol. During pyrolysis, the WPCBs were converted into three kinds of products, in which solid and gas products could be applied in the field of materials and energy. The composition of WPCBs oil products was complicated and sensitive to the pyrolysis temperature. The largest proportion of valuable liquid products (82.94%) was obtained at 600 °C, containing 52.87% monocyclic aromatic phenols, 4.39% polycyclic aromatic phenols, 3.07% brominated phenols, and 22.61% hydrocarbons, respectively. These valuable liquid products would be an attractive alternative as raw materials for the synthesis of phenolic resins and the production of petrochemicals.

Keywords

waste printed circuit boards / pyrolysis characteristics / kinetic analysis / valuable liquid products

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