废弃PVC塑料热解过程多尺度反应动力学特性研究

Multiscale thermogravimetric kinetics of waste polyvinyl chloride plastics

以废弃聚氯乙烯(PVC)塑料为研究对象,采用3种不同尺度研究方法(整体尺度、失重阶段尺度和重叠复杂反应反卷积尺度)探究其多步热降解反应动力学特性;采用Fraser-Suzuki函数对微分热失重(DTG)曲线进行反卷积分峰;采用3种无模型方法[微分法:Friedman法;积分法:Kissinger-Akahira-Sunose(KAS)法和Ozawa-Flynn-Wall(OFW)法]求解其反应动力学方程;采用Masterplots理论获得对应反应机理函数。结果表明,PVC塑料的热解由于其多步骤重叠反应特性,不适宜采用整体法或失重阶段法求解其动力学参数;反卷积法结果表明PVC热解过程包含3个拟反应,其表观活化能(E_(α))(KAS法)分别为128.01、182.34、246.49 kJ/mol,指前因子(lnA)分别为19.85、26.99、33.27 s^(-1),拟反应1、3符合Avrami-Erofeev反应机理模型,拟反应2符合Prout-Trompkins反应机理模型;本文研究结果可以为混合废弃塑料清洁高效热解技术的开发和应用提供理论基础。

Waste poly(vinyl chloride)(PVC)plastic was pyrolyzed to investigate its multi-steps thermal degradation reac-tion kinetic properties.The kinetic parameters were characterized in three different-scale methods,including the integrated method,weight-loss stage method,and overlapping complex reaction-deconvolution method.The overlapped reactions were separated by peak-fitting of the differential thermogravimetric curves using Fraser-Suzuki deconvolution function.Three model-free methods,including the Friedman’s differential method,Kissinger-Akahira-Sunose’s integral method,and Ozawa-Flynn-Wall’s integral method,were adopted to simplify the kinetics model and estimate the kinetic triplets.The master plots theory was used to obtain the most suitable mechanism model.The results indicated that the integrated method or weight-loss stage method was not appropriate to the determination of the kinetic characteristics of PVC pyroly-sis due to the complex overlapping multi-step reactions.The results from the deconvolution method showed that the ap-parent activation energy of the separated three pseudo reactions based on the KAS method were 128.01,182.34,and 246.49 kJ/mol,associated with the corresponding pre-exponential factors of 19.84,26.99,and 33.26 s^(-1),respectively.The pseudo reactions 1 and 3 accorded with Avrami-Erofeev mechanism model,whereas the pseudo reaction 2 complied with the Prout-Trompkins mechanism model.The results obtained from this work could be used as a theoretical basis for the development and application of clean and efficient waste plastics pyrolysis technology.