基于铁基载氧体的聚乙烯化学链解聚机理及过程

Mechanism and Process of Chemical Looping Depolymerization of Polyethylene Based on Iron-Based Oxygen Carriers

为了探索聚乙烯(PE)在铁基载氧体作用下的化学链解聚机理及过程,首先利用热重分析仪研究不同升温速率下PE在Fe_(2)O_(3)作用下化学链解聚的反应特性;其次从化学反应动力学的角度解析PE化学链解聚过程,采用等转化率法对PE体系的活化能进行了计算和分析;最后采用反应分子动力学方法开展了PE的化学链解聚模拟,在微观原子尺度上分析和阐释了解聚的过程和机制。结果表明:化学链解聚过程中质量损失由PE和Fe_(2)O_(3)共同贡献,Fe_(2)O_(3)释放的晶格氧促进了反应的进行;PE发生化学链解聚反应后主要产物以CO_(2)为主,而非化学链过程产物主要由一系列碳数为8~26的正构烷烃和正构烯烃组成;铁基载氧体作用的化学链过程中PE解聚的平均活化能为116.88 kJ/mol,远低于其常规热裂解的活化能。PE在化学链过程中的裂解属于典型的无规裂解,总体遵循自由基链反应理论。

To explore the mechanism and process of chemical looping depolymerization of polyethylene(PE)under the action of iron-based oxygen carrier,the reaction characteristics of chemical looping depolymerization of PE under the action of Fe_(2)O_(3)at different heating rates were firstly studied using thermogravimetric analyzer.Then the process of chemical looping depolymerization of PE was analyzed from the perspective of chemical reaction kinetics,and the activation energy of PE system was calculated and analyzed by the equal conversion method.Finally,the simulation of chemical looping depolymerization of PE was carried out by the reactive molecular dynamics method,and the process and mechanism of depolymerization were analyzed and interpreted at the microscopic atomic scale.The results show that mass loss during chemical looping depolymerization is jointly contributed by PE and Fe_(2)O_(3),and the lattice oxygen released by Fe_(2)O_(3)has promoted the reaction;the main product from the chemical looping depolymerization reaction of PE is carbon dioxide,and the product not arising from the chemical looping process is mainly composed of a series of n-alkanes and n-alkenes with carbon number ranging from 8 to 26;the average activation energy of PE depolymerization during the chemical looping process under the action of iron-based oxygen carrier is 116.88 kJ/mol,much lower than the activation energy from conventional thermal cleavage of PE.The cleavage of PE in the chemical looping process is a typical random cleavage,which generally follows the theory of free radical chain reaction.