Thermodynamic and kinetic analysis of waste plastic pyrolysis: Synergistic effects and sustainability perspectives

Prathwiraj Meena, Rohidas Bhoi
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Abstract

In this study, low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), waste mixed plastics (WMPs) and WMPs with spent fluid catalytic cracking (sFCC) catalyst (WMPs/ sFCC) were investigated to simulate real-life pyrolysis and catalytic pyrolysis of waste plastics using Thermogravimetric analysis (TGA). TGA was performed under different heating rates i.e., 5, 10, 15 and 20 ˚C/min) in an inert nitrogen atmosphere. The pyrolysis kinetics are assessed using three model-free methods, Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Starink, as well as two model-fitting methods, Coats–Redfern (CR) and Criado methods (master plots). The results showed that the WMPs exhibited a positive synergetic effect among the different types of plastics, leading to a notable reduction in degradation temperature and required activation energy. Moreover, adding sFCC catalysts significantly lowered the initial pyrolysis temperature (approximately 47 ˚C) of WMPs compared to direct pyrolysis. Moreover, the average activation energy of WMPs decreased by approximately 13.41 kJ/mole with the inclusion of the sFCC catalyst. The thermodynamic properties such ΔH, ΔG and ΔS suggested that the process was endothermic, non-spontaneous and decreased in randomness during pyrolysis. This study promotes sustainability through a circular economy to convert waste into wealth. These findings offer valuable theoretical insights for reducing energy consumption in plastic pyrolysis and expanding the applications of sFCC catalyst.
废塑料热解的热力学和动力学分析:协同效应和可持续性观点
本研究以低密度聚乙烯(LDPE)、聚丙烯(PP)、聚苯乙烯(PS)、废混合塑料(WMPs)和含废流体催化裂化(sFCC)催化剂(WMPs/ sFCC)为研究对象,采用热重分析法(TGA)模拟废塑料的真实热解和催化热解。在惰性氮气氛中,分别在5、10、15和20℃/min的升温速率下进行热重分析。采用Flynn-Wall-Ozawa (FWO)、Kissinger-Akahira-Sunose (KAS)和Starink三种无模型方法以及Coats-Redfern (CR)和Criado两种模型拟合方法(主图)对热解动力学进行了评估。结果表明,wmp在不同类型的塑料之间表现出积极的协同效应,导致降解温度和所需活化能显著降低。此外,与直接热解相比,sFCC催化剂的加入显著降低了wmp的初始热解温度(约47℃)。此外,sFCC催化剂的加入使wmp的平均活化能降低了约13.41 kJ/mol。ΔH‡、ΔG‡和ΔS‡等热力学性质表明该过程为吸热过程,非自发过程,且热解过程的随机性降低。这项研究通过循环经济将废物转化为财富来促进可持续发展。这些研究结果为降低塑料热解过程的能耗和扩大sFCC催化剂的应用提供了有价值的理论见解。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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