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Mechanistic modeling of polymer pyrolysis: Investigation of intrinsic kinetics, reaction pathways, and structural heterogeneities.

机译：聚合物热解机理模型：内在动力学，反应途径和结构异质性研究。

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Resource recovery is a promising category of polymer recycling where polymeric waste is converted via thermal or chemical means to monomer and chemical feedstocks. Specifically, pyrolysis is an attractive method because of its simplicity and ability to handle a heterogeneous feedstock. Polymer pyrolysis is characterized by a complex free radical reaction network, which often yields a diverse product spectrum. While polymer pyrolysis has been studied for over 60 years, there are still questions about the kinetics and mechanisms of these reaction systems. We have utilized detailed mechanistic modeling to gain insight into the kinetics and mechanisms of polystyrene (PS), polyethylene (PE), and poly(styrene peroxide) (PSP) pyrolysis.;Mechanistic models based on the method of moments were developed to study PS and PE pyrolysis. Using the PS pyrolysis model, the possible reaction pathways for styrene dimer formation were examined. Net rate analysis demonstrated that the 7,3-hydrogen shift pathway was dominant for dimer formation, while the benzyl radical addition pathway became more competitive as temperature increased. Additionally, the PS pyrolysis model was used to determine an overall activation energy of 53.3 +/- 1.3 kcal mol-1, which was free of transport effects. The PE pyrolysis model was utilized to study the temporal evolution of the diverse product spectrum from PE decomposition. Net rate analysis was utilized to compare the general reaction pathways of product formation. Random scission was found to be dominant, while the backbiting pathway played a complementary role for product formation during PE pyrolysis.;The method of moments modeling framework was extended by developing an algorithm to track backbone triad concentrations within polymer pyrolysis models. The algorithm was validated using the PS pyrolysis model. A PSP pyrolysis model was constructed using this algorithm and was of manageable size, but because of the stiffness of the model equations, it could not be solved. To address this difficulty, a kinetic Monte Carlo model for PSP pyrolysis was constructed. The model was used to test the traditional mechanism for PSP pyrolysis. A new reaction pathway relying on successive hydrogen abstraction reactions was found to be viable for formation of the minor products of PSP pyrolysis.
机译：资源回收是聚合物回收的一个有前途的类别，其中聚合物废物通过热或化学方法转化为单体和化学原料。特别地，热解是一种有吸引力的方法，因为它的简单性和处理异质原料的能力。聚合物热解的特征在于复杂的自由基反应网络，该网络经常产生多样化的产物谱。尽管已经对聚合物热解技术进行了60多年的研究，但对于这些反应系统的动力学和机理仍然存在疑问。我们利用详细的机械模型来深入了解聚苯乙烯（PS），聚乙烯（PE）和聚（过氧化苯乙烯）（PSP）热解的动力学和机理。;基于矩量法的机械模型被开发来研究PS和PE热解。使用PS热解模型，研究了苯乙烯二聚体形成的可能反应途径。净速率分析表明，7,3-氢转移途径是二聚体形成的主要途径，而苄基添加途径随着温度的升高变得更具竞争性。此外，PS热解模型用于确定53.3 +/- 1.3 kcal mol-1的总活化能，该活化能没有传输效应。利用PE热解模型研究了PE分解产生的多种产物谱随时间的变化。净速率分析用于比较产物形成的一般反应途径。发现随机断裂占主导地位，而回位途径在PE热解过程中对产物形成起补充作用。;矩矩建模框架方法通过开发一种算法来跟踪聚合物热解模型中的骨架三联体浓度而得到扩展。使用PS热解模型验证了该算法。使用该算法构建了一个PSP热解模型，该模型具有可管理的大小，但是由于模型方程的刚性，无法解决。为了解决这个困难，建立了用于PSP热解的动力学Monte Carlo模型。该模型用于测试PSP热解的传统机理。发现依赖于连续的氢提取反应的新反应途径对于形成PSP热解的次要产物是可行的。

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