Abstract The enhancement effect of supercritical water (SCW) on scrap tire (ST) depolymerization was investigated based on structural feature of SCW using the reactive force field (ReaxFF) molecular dynamics (MD) simulation and density functional theory (DFT) method. The results show that SCW acts not only in clusters but as non-bonded H2O monomers during ST depolymerization. Moreover, the fraction of clusters and non-bonded monomers determines the proportion of depolymerization products. The strong mutual attraction between oxygen atoms in SCW and carbon atoms in rubber leads to formation of C O bonds. This causes a sharp decrease in the cracking energy of contiguous C C bonds, thereby resulting in complete depolymerization of rubber. The impact of SCW on H2/CO formation was also analyzed. It is indicated that alkoxy groups (Rn-C=O) in rubber are the major precursors of CO. Microscopic pathways of H2 formation based on ST depolymerization with SCW were described. The optimal range of water/rubber mass ratio ranged from 4 to 6 for more oil and H2. The theoretical results presented herein are critical for understanding the practicality of using SCW to convert ST to valuable oil and fuel-gas, as well as provide new insight into chemical processes based on SCW.

中文翻译：

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超临界水对废旧轮胎解聚增强作用的新认识：基于ReaxFF-MD模拟和DFT方法的研究

摘要 基于超临界水(SCW) 的结构特征，采用反作用力场(ReaxFF) 分子动力学(MD) 模拟和密度泛函理论(DFT) 方法研究了超临界水(SCW) 对废轮胎(ST) 解聚的增强作用。结果表明，在 ST 解聚过程中，SCW 不仅在簇中起作用，而且作为非键合的 H2O 单体起作用。此外，簇和非键合单体的比例决定了解聚产物的比例。SCW 中的氧原子与橡胶中的碳原子之间的强烈相互吸引导致 CO 键的形成。这导致连续CC键的裂解能急剧下降，从而导致橡胶完全解聚。还分析了 SCW 对 H2/CO 形成的影响。表明橡胶中的烷氧基(Rn-C=O)是CO的主要前体。描述了基于SCW ST解聚H2形成的微观途径。对于更多的油和 H2，水/橡胶质量比的最佳范围为 4 到 6。本文提出的理论结果对于理解使用 SCW 将 ST 转化为有价值的石油和燃料气的实用性至关重要，并为基于 SCW 的化学过程提供新的见解。