Recent studies indicate that accurate description of the reaction mechanisms in fast pyrolysis of 1,3,5-trinitro-1,3,5-triazinane (RDX) is still of great challenge. In this work, the pyrolysis mechanism of RDX has been investigated by ab initio kinetic calculations and modeling simulations. The potential energy profiles of primary and secondary reactions in RDX decomposition were constructed with B2PLYPD3/CBS//B3LYP-D3/6–311+G(d,p), and the rate constants were obtained from the solution of RRKM/master-equations. The proposed reaction pathways and calculated rate constants were incorporated into a kinetic model. The simulated results illustrate that the decomposition of RDX mainly occurs through its NNO₂ bond fission to generate RDXR, whose subsequent decomposition mainly undergoes CH β-scission to form INT175 and the ring-opening reaction to form RDXRO. Interestingly, the less favored initial intermediate, INT175, is predicted to be a major product in the secondary decomposition of RDXR. The incorporation of important channels for key intermediates, such as CH β-scission of RDXR, remarkably affects the decomposing pathways of RDX. Meanwhile, the contribution of bimolecular reactions such as H/O abstraction reactions from RDX by NO₂/NO is simulated to be insignificant for the decomposition of RDX under the conditions studied.

最近的研究表明，准确描述 1,3,5-三硝基-1,3,5-三嗪烷 (RDX) 快速热解的反应机理仍然是一个巨大的挑战。在这项工作中，通过从头算动力学计算和建模模拟研究了 RDX 的热解机理。用 B2PLYPD3/CBS//B3LYP-D3/6–311+G(d,p) 构建 RDX 分解中初级和次级反应的势能分布，并从 RRKM/主方程的解中获得速率常数. 提出的反应途径和计算的速率常数被纳入动力学模型。模拟结果表明RDX的分解主要通过其N NO ₂键裂变生成RDXR，其随后的分解主要经历C H β-裂开形成INT175和开环反应形成RDXRO。有趣的是，不太受欢迎的初始中间体 INT175 预计将成为 RDXR 二次分解的主要产物。关键中间体的重要通道的引入，例如RDXR 的 C H β 断裂，显着影响了 RDX 的分解途径。同时，在所研究的条件下，模拟了双分子反应（如 NO ₂ /NO 从 RDX 中提取 H/O 反应）对 RDX 分解的贡献是微不足道的。