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Catalytic stepwise pyrolysis for dechlorination and chemical recycling of PVC-containing mixed plastic wastes: Influence of temperature, heating rate, and catalyst
Science of the Total Environment ( IF 8.2 ) Pub Date : 2023-11-10 , DOI: 10.1016/j.scitotenv.2023.168344 Yanjun Hu 1 , Mingzhe Li 2 , Nan Zhou 2 , Hao Yuan 2 , Qianqian Guo 2 , Long Jiao 2 , Zengyi Ma 3
Science of the Total Environment ( IF 8.2 ) Pub Date : 2023-11-10 , DOI: 10.1016/j.scitotenv.2023.168344 Yanjun Hu 1 , Mingzhe Li 2 , Nan Zhou 2 , Hao Yuan 2 , Qianqian Guo 2 , Long Jiao 2 , Zengyi Ma 3
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The viability of pyrolysis technology for chemical recycling of plastics is challenged by the presence of PVC in real-world mixed plastic wastes. This study aims to investigate catalytic stepwise pyrolysis as a pretreatment step to remove chlorine from PVC-containing plastic wastes prior to further processing. TG-FTIR and Py-GCMS analysis as well as experiments on a lab-scale pyrolysis system were conducted to study the influence of key processing parameters on the pretreatment including temperature, heating rate, and catalysts. Py-GCMS results indicated 300 °C to be the best pretreatment temperature in terms of balancing Cl removal and avoidance of organochloride formation. Metal oxides, i.e., CaO and FeO, mainly acted as adsorbents of HCl gases with little cracking effect, and their adsorption effects are positively correlated with alkalinity. ZSM-5 catalysts promoted the release of HCl, and the dechlorination effect was more pronounced with ZSM-5 of higher acidity. In contrast, in the lab-scale pyrolysis system, 350 °C pretreatment achieved the highest HCl generation ratio, i.e., 43.60 %. The addition of zeolite catalyst significantly reduced the content of organochloride in the pyrolysis oil in contrast to the performance of metal oxides, but also absorbed most HCl instead of promoting HCl release as in Py-GCMS tests. Mass balance analyses revealed that the majority of chlorine was retained in the solid residues following the catalytic stepwise pyrolysis process, with the notable exception of FeO. ZSM-5(25) catalyst combined with 350 °C pretreatment temperature and 550 °C final pyrolysis achieved the lowest chlorine content in the pyrolysis oil, i.e., 20 ppm, among different process conditions.
中文翻译：
含 PVC 混合塑料废物的催化分步热解脱氯和化学回收：温度、加热速率和催化剂的影响
现实世界的混合塑料废物中存在 PVC，这对塑料化学回收热解技术的可行性提出了挑战。本研究旨在研究催化逐步热解作为预处理步骤，在进一步加工之前去除含 PVC 塑料废物中的氯。通过TG-FTIR和Py-GCMS分析以及实验室规模的热解系统实验，研究了温度、加热速率和催化剂等关键工艺参数对预处理的影响。Py-GCMS 结果表明，就平衡 Cl 去除和避免有机氯化物形成而言，300 °C 是最佳预处理温度。金属氧化物CaO和FeO主要作为HCl气体的吸附剂，裂解作用较小，其吸附效果与碱度正相关。ZSM-5催化剂促进了HCl的释放，且ZSM-5酸度越高，脱氯效果越明显。相比之下，在实验室规模的热解系统中，350℃预处理实现了最高的HCl生成率，即43.60%。与金属氧化物的性能相比，沸石催化剂的添加显着降低了热解油中有机氯化物的含量，但也吸收了大部分HCl，而不是像Py-GCMS测试中那样促进HCl释放。质量平衡分析表明，在催化逐步热解过程后，大部分氯保留在固体残留物中，但 Fe3O 除外。ZSM-5(25)催化剂结合350℃预处理温度和550℃最终热解，实现了不同工艺条件下热解油中最低的氯含量，即20ppm。
更新日期：2023-11-10
中文翻译：
含 PVC 混合塑料废物的催化分步热解脱氯和化学回收：温度、加热速率和催化剂的影响
现实世界的混合塑料废物中存在 PVC，这对塑料化学回收热解技术的可行性提出了挑战。本研究旨在研究催化逐步热解作为预处理步骤，在进一步加工之前去除含 PVC 塑料废物中的氯。通过TG-FTIR和Py-GCMS分析以及实验室规模的热解系统实验，研究了温度、加热速率和催化剂等关键工艺参数对预处理的影响。Py-GCMS 结果表明，就平衡 Cl 去除和避免有机氯化物形成而言，300 °C 是最佳预处理温度。金属氧化物CaO和FeO主要作为HCl气体的吸附剂，裂解作用较小，其吸附效果与碱度正相关。ZSM-5催化剂促进了HCl的释放，且ZSM-5酸度越高，脱氯效果越明显。相比之下，在实验室规模的热解系统中，350℃预处理实现了最高的HCl生成率，即43.60%。与金属氧化物的性能相比，沸石催化剂的添加显着降低了热解油中有机氯化物的含量，但也吸收了大部分HCl，而不是像Py-GCMS测试中那样促进HCl释放。质量平衡分析表明，在催化逐步热解过程后，大部分氯保留在固体残留物中，但 Fe3O 除外。ZSM-5(25)催化剂结合350℃预处理温度和550℃最终热解，实现了不同工艺条件下热解油中最低的氯含量，即20ppm。
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