高氯酸铵热分解机理的密度泛函理论研究  

Density Functional Theory Study on Thermal Decomposition Mechanisms of Ammonium Perchlorate

作　　者：杨洁[1,2] 凌琳 李玉学 吕龙 Yang Jie;Ling Lin;Li Yuxue;Lu Long(School of Materials and Chemistry,University of Shanghai for Science and Technology,Shanghai 200093,China;CAS Key Laboratory of Energy Regulation Materials,Shanghai Institute of Organic Chemistry,Chinese Academy of Sciences,Shanghai 200032,China)

机构地区：[1]上海理工大学材料与化学学院,上海200093 [2]中国科学院上海有机化学研究所院能量调控材料重点实验室,上海200032

出　　处：《化学学报》2023年第4期328-337,共10页Acta Chimica Sinica

基　　金：国家自然科学基金(No.22175197)资助项目。

摘　　要：深入理解高氯酸铵的热分解机理,对于优化固体推进剂配方设计十分重要.我们采用对称破缺密度泛函方法(BS-UB3LYP/6-311+G(d,p)),对高氯酸铵的热分解机理进行了系统的梳理和深入研究.首先,高氯酸铵通过质子转移,生成HClO_(4)和NH_(3),从吸附态进入气相.进而高氯酸的Cl—OH键均裂,生成羟基自由基·OH和三氧化氯自由基·ClO_(3),它们优先和NH3反应,生成·NH_(2).·NH_(2)和HClO_(4)反应生成·ClO_(4)自由基,进而和NH_(3)反应生成H_(2)NO,再被自由基物种拔H生成NO.NO和·OH反应生成NO_(2),和·NH_(2)及·OH反应生成N_(2)O.这些产物与诸多实验观测结果一致.The thermal decomposition characteristics of ammonium perchlorate(AP)have a great influence on the performance of solid propellant.Although a large number of mechanistic studies have been published over the past few decades,there is no unified understanding of the decomposition yet,and the overall mechanism pathway is still unclear.In the present work,the thermal decomposition pathways of AP were studied systematically using broken-symmetry density functional theory method(BS-UB3LYP/6-311+G(d,p)).This method can describe the homo-cleavage process of covalent bond well,and locate the transition state with singlet-diradical characteristics.Compared with typical multireference method,brokensymmetry density functional theory(BS-UDFT)can give good results and is much faster,and therefore is highly convenient for practical application.The results show that,the overall thermal decomposition pathway under the experimental conditions is initiated by the proton transfer between NH_(4)^(+)cation and ClO_(4)^(-)anion,leading to neutral NH_(3) and HClO_(4) molecules,which are absorbed on the AP surface and then escape to the gas phase.The second important step is the homolytic cleavage of the Cl—OH bond in HClO_(4).The energy barrier is 67.5 kJ/mol under 620 K.Then,·OH radical and·ClO_(3) radical react with NH_(3) molecule,yielding·NH_(2) radical.Then the·NH_(2) radical react with HClO_(4),leading to·ClO_(4) radical,which reacts with NH_(3),leading to the oxidized species H_(2)NO.The radical species,such as·OH,·NH_(2),·ClO and so on,abstract the H atom of H_(2)NO,yielding NO.NO reacts with·OH radical,leading to NO_(2);NO reacts with·NH_(2) radical and·OH radical,leading to N_(2)O.These products are consistent well with the experimental observations.Due to the complexity of the mechanisms,some strategies are used in this study:firstly,we concentrate on the reaction pathways of active species and the NH_(3) and HClO_(4) molecules,which exist in large amount;secondly,more reaction pathways involving the newly formed

关 键 词：高氯酸铵 热分解机理 broken-symmetry density functional theory(BS-UDFT) 开壳层单重态双自由基 固体推进剂 

分 类 号：TQ560.1[化学工程—炸药化工]