基于分子动力学模拟的轮胎橡胶气相热解产物反应机理

运用分子动力学的方法，对轮胎橡胶的热解过程进行了模拟，并结合模拟结果和密度泛函数对其气相产物的反应路径进行推测计算。模拟结果表明，热解过程主要分为两个阶段，低温热解阶段发生的主要反应是橡胶长链断裂形成单体，主要产物为异戊二烯、苯乙烯和1,3-丁二烯；高温热解阶段发生的主要反应是单体进一步生成小分子气体，产物中CH₄、H₂、C₂H₄占大部分，还有少量C₂H₆、C₃H₆。其中CH₃·攻击异戊二烯和苯乙烯单体夺取特定位置的H·是生成CH₄的最优路径，H·攻击苯乙烯单体夺取特定位置的H·是生成H₂的最优路径，CH₂CH·攻击1,3-丁二烯单体夺取特定位置的H·是生成CH₂CH₂的最优路径。本文还将热解产物分别跟天然橡胶单独热解和天然橡胶与丁苯橡胶共热解的热解产物做对比，为废旧轮胎橡胶热解得到特定的气相产物和催化热解提供理论依据。

Gas phase pyrolysis products of tire rubber based on molecular dynamics simulation

In order to further understand the pyrolysis mechanism of tire rubber, the molecular dynamics method was used to simulate the pyrolysis process of tire rubber, and the reaction paths of gas-phase products were speculated by combining the simulation results and density function. The simulation results showed that the pyrolysis process was mainly divided into two stages: the low temperature pyrolysis stage where the main reaction was the long chain fracture of rubber to form monomers and the main products were isoprene, styrene and 1,3-butadiene, and the high temperature pyrolysis stage where the main reaction was that the monomers further generated small molecular gas in which CH₄, H₂ and C₂H₄ accounted for the majority with a small amount of C₂H₆ and C₃H₆. Among them, CH₃· attacking isoprene and styrene monomer to capture the H· at a specific position was the optimal path to generate CH₄, H· attacking styrene monomer to capture the H· at a specific position was the optimal path to generate H₂ and CH₂CH· attacking 1,3-butadiene monomer to capture the H· at a specific position was the optimal path to generate CH₂CH₂. The pyrolysis products were compared with those of natural rubber alone and natural rubber/butadiene styrene rubber co-pyrolysis. This would provide a theoretical basis for pyrolysis of waste tire rubber to obtain specific gaseous products and catalytic pyrolysis.