聚乙烯热解制备二氧化硅表面碳涂层的机理研究  

Mechanism study of polyethylene pyrolysis for preparation of carbon-coated silica surface

作　　者：牟凯达 宋立健 谭晶[1] 杨卫民[1] 程礼盛[1] Mou Kaida;Song Lijian;Tan Jing;Yang Weimin;Cheng Lisheng(College of Mechanical and Electrical Engineering,Beijing University of Chemical Technology,Beijing 100029)

机构地区：[1]北京化工大学机电工程学院,北京100029

出　　处：《化工新型材料》2023年第6期162-168,共7页New Chemical Materials

基　　金：国家自然科学基金面上项目(52073012)。

摘　　要：利用反应分子动力学ReaxFF方法模拟了聚乙烯热解碳沉积二氧化硅基底的微观过程,通过分析沉积过程中碳结构、体系产物数目及碳碳径向分布函数的变化来揭示聚乙烯碳化机理。结果表明:碳结构的形成主要是远离基底芳香环的沉积成片生长和靠近基底的小分子碳的渗入、析出,连接在沉积的碳结构上。其中远离基底的聚乙烯热解有两个方向,一是直接热解为小分子的碳氢化合物(C_(2)H_(4)、C_(3)H_(6)、C_(4)H_(8)等),继而小分子碳氢化合物继续反应脱氢,重组形成碳链和碳环;二是未完全断链的碳氢长链(C>5),与碳氢小分子进行反应。研究温度和保温时间对沉积的影响得知,升温可以加快反应速率,但不改变整体的反应趋势。温度为2500K,在保证碳源充足的情况下,会有更多的碳形成稳定的碳环结构,持续生长。从ReaxFF动力学角度研究高分子聚合物制备碳材料的机理,可以为相关实验研究提供理论支持。The reaction molecular dynamics simulation ReaxFF method was used to simulate the micro-process of polyethylene pyrolysis carbon deposition on silicon dioxide substrate.The polyethylene carbonization mechanism was revealed by analyzing the changes of carbon structure,system product number,and carbon-carbon radial distribution function during the deposition process.The results showed that the formation of carbon structure was mainly the deposition of sheet growth away from the substrate aromatic ring and the infiltration and precipitation of small molecular carbon near the substrate,which were linked to the deposited carbon structure.The pyrolysis of polyethylene had two directions.One was the direct pyrolysis of polyethylene into small molecular hydrocarbons(C_(2)H_(4),C_(3)H_(6),C_(4)H_(8),etc.),and then the small molecular hydrocarbons continued to react with dehydrogenation and recombine the carbon chain.The second was the incompletely broken long hydrocarbon chain(C5),which reacted with small hydrocarbon molecules,dehydrogenation,recombination and cyclization.The influence of temperature and holding time on the deposition was studied.The results showed that raising the temperature could accelerate the reaction rate,but did not change the overall reaction trend.When the temperature was 2500 K and the carbon source was sufficient,more carbon formed a stable carbon ring structure and continued to grow.In this paper,the mechanism of pyrolysis of polymer to prepare carbon materials was studied from the perspective of ReaxFF kinetics,which could provide theoretical support for related experimental studies.

关 键 词：聚乙烯 热解 二氧化硅 分子模拟 REAXFF 碳涂层 

分 类 号：O643[理学—物理化学]