School of Chemical Engineering, Northwest University, International Science & Technology Cooperation Base of MOST for Clean Utilization of Hydrocarbon Resources, Chemical Engineering Research Center of the Ministry of Education for Advanced Use Technology of Shanbei Energy, Shaanxi Research Center of Engineering Technology for Clean Coal Conversion, Collaborative Innovation Center for Development of Energy and Chemical Industry in Northern Shaanxi, Xi'an 710069, Shaanxi, China.
School of Science, Xijing University, Xi'an Key Laboratory of Advanced Photo-electronics Materials and Energy Conversion Device, Xi'an 710123, Shaanxi, China.
Waste Manag. 2022 Jul 15;149:134-145. doi: 10.1016/j.wasman.2022.06.008. Epub 2022 Jun 18.
The pyrolysis treatment of waste printed circuit boards (WPCBs) shows great potential for sustainable treatment and hazard reduction. In this work, based on thermogravimetry (TG), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), and density functional theory (DFT), the thermal weight loss, product distribution, and kinetics of WPCBs pyrolysis were studied by single-step and multi-step pyrolysis at fast (600 °C/min) and slow (10 °C/min) heating rates. The heating rates of TG and Py-GC/MS were the same for each group of experiments. In addition, the bond dissociation energy (BDE) of WPCBs polymer monomers was calculated by DFT method. Compared with slow pyrolysis, the final weight loss of fast pyrolysis is reduced by 0.76 wt%. The kinetic analysis indicates that the activation energies of main pyrolysis stages range from 98.29 kJ/mol to 177.59 kJ/mol. The volatile products of fast pyrolysis are mainly phenols and aromatics. With the increase of multi-step pyrolysis temperature, the order of the escaping volatiles is phenols, hydrocarbyl phenols, aromatics, and benzene (or diphenyl phenol). The pyrolysis residue of WPCBs may contains phenolics and polymers. Based on the free radical reactions, the mechanism and reaction pathways of WPCBs pyrolysis were deduced by the DFT. Moreover, a large amount of benzene is produced by pyrolysis, and its formation mechanism was elaborated.
废旧印刷电路板 (WPCBs) 的热解处理显示出可持续处理和降低危害的巨大潜力。在这项工作中，基于热重分析 (TG)、热解-气相色谱/质谱联用 (Py-GC/MS) 和密度泛函理论 (DFT)，通过单步和多步热解，在快速 (600°C/min) 和缓慢 (10°C/min) 加热速率下研究了 WPCBs 的热失重、产物分布和动力学。每组实验的 TG 和 Py-GC/MS 的加热速率相同。此外，通过 DFT 方法计算了 WPCBs 聚合物单体的键离解能 (BDE)。与慢速热解相比，快速热解的最终失重减少了 0.76 wt%。动力学分析表明，主要热解阶段的活化能范围为 98.29 kJ/mol 至 177.59 kJ/mol。快速热解的挥发性产物主要是酚类和芳烃。随着多步热解温度的升高，挥发性物质逸出的顺序是酚类、烃基酚类、芳烃类和苯（或二苯基酚）。WPCBs 的热解残渣可能含有酚类和聚合物。基于自由基反应，通过 DFT 推断了 WPCBs 热解的机理和反应途径。此外，热解会产生大量的苯，详细阐述了其形成机制。
