Li Chao, Zhang Chenting, Gholizadeh Mortaza, Hu Xun
School of Material Science and Engineering, University of Jinan, Jinan, 250022, PR China.
Faculty of Chemical and Petroleum Engineering, University of Tabriz, Tabriz, Iran.
J Hazard Mater. 2020 Nov 15;399:123075. doi: 10.1016/j.jhazmat.2020.123075. Epub 2020 May 30.
Polyethylene is a major contributor of plastic waste, which can be converted into liquid fuel via catalytic pyrolysis. In this study, the pyrolysis of light or heavy density polyethylene (LDPE and HDPE) and their mixture with the biochar produced from gasification of poplar wood as catalyst was investigated. The results showed that, during the co-pyrolysis of LDPE and HDPE in absence or presence of biochar catalyst, cross-interaction of reaction intermediates originated from the degradation of LDPE and HDPE substantially promoted the formation of gaseous products and the evolution of heavy organics with π-conjugated structures in the tar. During the pyrolysis of HDPE, more heavy tar while less wax was produced, while it was contrary during the pyrolysis of LDPE. In the catalytic pyrolysis of LDPE, the volatiles could be effectively cracked over the biochar catalyst, forming more gases, while in the catalytic pyrolysis of HDPE, instead of catalyzing the cracking of the heavy components, the biochar catalyzed the polymerisation reactions. The properties of the biochar catalyst in terms of crystallinity, surface functionality, and internal structures also changed remarkably due to the transfer of oxygen-containing species from the polyethylene to biochar and the interaction of biochar with volatiles in the pyrolysis.
聚乙烯是塑料垃圾的主要来源，可通过催化热解转化为液体燃料。本研究考察了低密度或高密度聚乙烯（LDPE和HDPE）及其与杨树气化产生的生物炭作为催化剂的混合物的热解过程。结果表明，在有无生物炭催化剂存在的情况下，LDPE和HDPE共热解过程中，源自LDPE和HDPE降解的反应中间体的交叉相互作用显著促进了气态产物的形成以及焦油中具有π共轭结构的重质有机物的析出。HDPE热解过程中产生的重质焦油较多而蜡较少，而LDPE热解时情况则相反。在LDPE的催化热解中，挥发物可在生物炭催化剂上有效裂解，生成更多气体，而在HDPE的催化热解中，生物炭并未催化重质组分的裂解，而是催化了聚合反应。由于热解过程中含氧物种从聚乙烯转移至生物炭以及生物炭与挥发物的相互作用，生物炭催化剂在结晶度、表面官能团和内部结构方面的性质也发生了显著变化。
