Towards solvothermal upcycling of mixed plastic wastes: Depolymerization pathways of waste plastics in sub- and supercritical toluene
Towards solvothermal upcycling of mixed plastic wastes: Depolymerization pathways of waste plastics in sub- and supercritical toluene
复制标题
混合塑料废物的溶剂热升级回收：废塑料在亚临界和超临界甲苯中的解聚途径
DOI：
10.1016/j.ecmx.2021.100158
复制
发表时间：
2022
影响因子：
--
通讯作者：
Toufiq Reza, M.
中科院分区：
文献类型：
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作者：
Saha, Nepu;Banivaheb, Soudeh;Toufiq Reza, M.
溶剂热液化(STL)是一种用亚临界和超临界溶剂处理废旧原料的热化学转化过程。这项研究的主要目标是调查以甲苯为溶剂的一步STL如何降解难以回收的废塑料(#5-#7)。将三种不同的塑料废物，即聚丙烯(#5)、聚苯乙烯(#6)和聚氨酯(#7)及其相等的混合物(按重量计，在这里也称为混合塑料废物)在7℃、350℃和400℃的压力炸弹中用甲苯在300、350和400℃下进行溶剂热液化3、6和9小时，以确定温度和时间的影响。从固体残渣中分离出液体产物，并进一步分析了STL转化率、元素分析的元素组成变化、热重分析仪(TGA)的沸点分布、质子核磁共振(1HNMR)的化学键变化以及气相色谱-质谱仪(GCMS)的降解产物。结果表明，STL转化率随反应温度的升高和反应时间的延长而增加。从元素分析可以预测，原油的较高热值在30~45万焦耳/公斤之间。沸点分布表明，低碳烃(C8-C20)的产率从300℃时的约10%显著增加到400℃时的80%。另外，产物分布表明，芳香度随停留时间的增加而增加，主要产物为苯和类苯乙烯产物。总体而言，观察到混合塑料废物对降解产物具有协同效应。
Solvothermal liquefaction (STL) is a thermochemical conversion process, where a waste feedstock is treated with sub-and supercritical solvents. The key objective of the study was to investigate how a one-step STL using toluene as a solvent can degrade hard-to-recycle waste plastics (#5–#7). Three different plastic wastes namely, polypropylene (#5), polystyrene (#6), and polyurethane (#7), and their equal mixture (by weight, also referred here as mixed plastic wastes) were solvothermally liquefied by toluene in a 7 mL pressure bomb at 300, 350, and 400 °C for 3, 6, and 9 h in order to determine the effect of temperature and time, respectively. The liquid products were separated from the solid residue and further analyzed in terms of the STL conversion, change in elemental compositions via ultimate analysis, boiling point distribution via thermogravimetric analyzer (TGA), alteration of chemical bonds via proton nuclear magnetic resonance spectroscopy (1H NMR), and degradation products via gas chromatography mass spectroscopy (GCMS). The results showed that the STL conversion increase with the increase of reaction temperature and time. From the elemental analysis, it can be predicted that the higher heating values of the crude products are between 30 and 45 MJ/kg. Boiling point distribution showed that the production of lower hydrocarbon (C8–C20) increased significantly from about 10% at 300 °C to 80% at 400 °C. Additionally, product distribution showed that the aromaticity increased with the increase of residence time where the main products are benzene and styrene like products. Overall, it was observed that mixed plastic wastes have a synergistic effect on the degradation products.